<PAGE>
                                                                     EXHIBIT 2.3
 
                           ASSET PURCHASE AGREEMENT

                                  BY AND AMONG

                        BIOSOURCE INTERNATIONAL, INC.,
                            A DELAWARE CORPORATION

                                      AND

                               BIOFLUIDS, INC.,
                            A MARYLAND CORPORATION

                                      AND

                           THE BIOFLUIDS STOCKHOLDER


                               DECEMBER 14, 1998
                                        
<PAGE>
 
                               TABLE OF CONTENTS
                                        
                                                                       Page
                                                                       ----
                                                                           
1.  DEFINITIONS...........................................................1
                                                                           
      1.1       Definitions...............................................1
                -----------
                                                                           
SECTION 2.  SALE AND TRANSFER OF ASSETS...................................6
      2.1       Purchased Assets..........................................6
                ----------------  
      2.2       Excluded Assets...........................................6
                ---------------
      2.3       Delivery of Possession....................................6
                ----------------------
      2.4       Right of Endorsement; Payment.............................6
                -----------------------------
                                                                           
SECTION 3.  CONSIDERATION.................................................6
      3.1       Purchase Price............................................6
                --------------
      3.2       Allocation of Purchase Price..............................7
                ----------------------------
      3.3       Prorations/Adjustments....................................7
                ----------------------
      3.4       Form of Payments..........................................7
                ----------------
                                                                           
SECTION  4.  ASSUMPTION OF LIABILITIES....................................7
      4.1       Assumed Liabilities.......................................7
                -------------------
      4.2       Liabilities Not Assumed...................................8
                -----------------------
      4.3       Right of Enforcement and Settlement.......................8
                -----------------------------------
                                                                           
SECTION  5.  CLOSING......................................................8
      5.1       The Closing Date..........................................8
                ----------------
      5.2       Actions and Deliveries by Seller at the Closing...........8
                -----------------------------------------------
      5.3       Actions and Deliveries by Purchaser at the Closing........9
                --------------------------------------------------
                                                                           
SECTION  6.  REPRESENTATIONS AND WARRANTIES OF BIOFLUIDS          
      AND THE BIOFLUIDS STOCKHOLDER.......................................9
      6.1       Organization, Standing and Corporate Power................9
                ------------------------------------------
      6.2       Authority and Capacity...................................10
                ----------------------
      6.3       Title to the Assets......................................10
                -------------------
      6.4       Rights of First Refusal on Assets........................10
                ---------------------------------
      6.5       Effect of Agreement......................................11
                -------------------
      6.6       Contracts, Agreements, Arrangements, Etc.................11
                ----------------------------------------
      6.7       Consents.................................................13
                --------
      6.8       Financial Statements.....................................14
                --------------------
      6.9       Litigation...............................................14
                ----------
      6.10      Compliance with the Law and Other Instruments............14
                ---------------------------------------------
      6.11      Absence of Certain Changes or Events.....................15
                ------------------------------------
<PAGE>
 
      6.12      Operation of the Business ....................................16
                -------------------------
      6.13      Suppliers; Raw Materials .....................................16
                ------------------------
      6.14      Absence of Certain Business Practices.........................16
                -------------------------------------
      6.15      Intellectual Property ........................................16
                ---------------------
                (a)          Title ...........................................16
                             -----
                (b)          Transfer ........................................16
                             --------
                (c)          No Infringement .................................17
                             ---------------
                (d)          Licensing Arrangements ..........................17
                             ----------------------
                (e)          No Intellectual Property Litigation .............17
                             -----------------------------------
                (f)          Due Registration, Etc ...........................17
                             ---------------------
                (g)          Use of Name and Mark ............................17
                             --------------------
      6.16      Environmental Matters ........................................18
                ---------------------
      6.17      Employees ....................................................18
                ---------
      6.18      Employee Benefit Plans, Etc...................................18
                ---------------------------
      6.19      Customers ....................................................18
                ---------
      6.20      Inventory ....................................................18
                ---------
      6.21      Purchase and Sale Obligations.................................19
                -----------------------------
      6.22      Accounts Receivable ..........................................19
                -------------------
      6.23      Tax Returns ..................................................19
                -----------
      6.24      Insurance ....................................................19
                ---------
      6.25      Powers of Attorney ...........................................20
                ------------------
      6.26      Prepaid Expenses .............................................20
                ----------------
      6.27      No Unrelated Liabilities .....................................20
                ------------------------
      6.28      No Change of Control Provisions...............................20
                -------------------------------
      6.29      No Finder's Fee ..............................................20
                ---------------
      6.30      Accuracy of Other Information; Disclosure.....................20
                -----------------------------------------
 
SECTION  7.  REPRESENTATIONS AND WARRANTIES OF BIOSOURCE......................20
      7.1       Organization, Standing and Corporate Power....................21
                ------------------------------------------
      7.2       Authorization of Agreement....................................21
                --------------------------
      7.3       Execution, Delivery and Performance...........................21
                -----------------------------------
      7.4       Effect of Agreement ..........................................21
                -------------------
      7.5       No Consents Required .........................................21
                --------------------
      7.6       No Finder's Fee ..............................................21
                ---------------
      7.7       Accuracy of Other Information; Disclosure.....................21
                -----------------------------------------

SECTION  8.  CONDUCT AND TRANSACTIONS PRIOR TO CLOSING .......................22
      8.1       Investigations ...............................................22
                --------------
      8.2       Operation of the Business Pending Closing.....................22
                -----------------------------------------
      8.3       Advice of Changes ............................................24
                -----------------
      8.4       Non-Disclosure or Use of Information..........................24
                ------------------------------------
      8.5       Governmental and Third Party Consents and Approvals...........24
                ---------------------------------------------------
      8.6       8-K Financial Statements .....................................25
                ------------------------
<PAGE>
 
SECTION  9.  CONDITIONS OF PURCHASE AND SALE..................................25
      9.1       Conditions to Obligations of Purchaser........................25
                --------------------------------------
                (a)       Representations and Warranties of Biofluids
                          -------------------------------------------
                          and the Biofluids Stockholder To Be True............25
                          ----------------------------------------
                (b)       No Proceedings......................................25
                          --------------
                (c)       No Adverse Change...................................25
                          -----------------
                (d)       Statutory Requirements..............................26
                          ----------------------
                (e)       Certificates........................................26
                          ------------
                (f)       Opinion of Counsel for Biofluids....................26
                          --------------------------------
                (g)       Audit...............................................26
                          -----
                (h)       Releases of Security Interests......................26
                          ------------------------------
                (i)       Consents............................................26
                          --------
                (j)       Authorization.......................................26
                          -------------
                (k)       Receipt of Right of Endorsement.....................26
                          -------------------------------
                (l)       Employment Agreement................................26
                          --------------------
                (m)       Non-Compete Agreement...............................26
                          ---------------------
                (n)       Escrow Instrument...................................26
                          -----------------
                (o)       Other Matters.......................................27
                          -------------
      9.2    Conditions to Obligations of Biofluids...........................27
             --------------------------------------
                (a)       Representations and Warranties of Purchaser 
                          -------------------------------------------
                          To Be True..........................................27
                          ----------
                (b)       Certificates........................................27
                          ------------
                (c)       Authorization.......................................27
                          -------------
                (d)       Opinion of Counsel for Purchaser....................28
                          --------------------------------
                (e)       No Proceedings......................................28
                          --------------
                (f)       Delivery of Purchase Price..........................28
                          --------------------------
                (g)       Escrow Instrument...................................28
                          -----------------
                (h)       Statutory Requirements..............................28
                          ----------------------
                (i)       Other Matters.......................................28
                          -------------
 
SECTION  10.  FURTHER AGREEMENTS OF THE PARTIES...............................28
      10.1      Further Agreements of Biofluids...............................28
                -------------------------------
      10.2      Confidentiality...............................................28
                ---------------
      10.3      Access to Books and Records...................................29
                ---------------------------
 
SECTION  11.  NATURE AND SURVIVAL OF REPRESENTATIONS AND 
      WARRANTIES; INDEMNITY; OFFSET RIGHTS....................................30
      11.1      Nature and Survival of Representations and Warranties.........30
                -----------------------------------------------------
      11.2      Indemnification by Biofluids and the Biofluids Stockholder....30
                ----------------------------------------------------------
      11.3      Indemnification by Purchaser..................................31
                ----------------------------
      11.4      Notice of Claim...............................................31
                ---------------
      11.5      Direct Claims.................................................31
                -------------
      11.6      Third Party Claims............................................32
                ------------------
<PAGE>
 
      11.7      Settlement of Third Party Claims..............................32
                --------------------------------
      11.8      Cooperation...................................................33
                -----------
      11.9      Adjustment to Indemnification Payments; 
                --------------------------------------- 
                Insurance; Subrogation........................................33
                ----------------------
      11.10     Basket on Indemnity...........................................33
                -------------------
      11.11     Limitation of Biofluids' Indemnification Liability............33
                --------------------------------------------------
      11.12     Release of Escrow Funds.......................................33
                -----------------------
 
SECTION  12.  TAXES...........................................................33
      12.1      Payment of Taxes, Filing of Returns...........................33
                -----------------------------------
      12.2      Sales Taxes...................................................33
                -----------
 
SECTION  13.  ARBITRATION.....................................................34
      13.1      Submission to Jurisdiction....................................34
                --------------------------
      13.2      Waiver of Immunity and Inconvenient Forum.....................34
                -----------------------------------------
      13.3      Arbitration Procedures........................................34
                ----------------------
      13.4      Final Arbitration Decisions...................................34
                ---------------------------
      13.5      Claims for Unpaid Balance.....................................35
                -------------------------
 
SECTION  14.  TERMINATION.....................................................35
      14.1      Termination...................................................35
                -----------
 
SECTION  15.  MISCELLANEOUS...................................................35
      15.1      Notices.......................................................35
                -------
      15.2      Entire Agreement..............................................37
                ----------------
      15.3      Successors and Assigns........................................37
                ----------------------
      15.4      Waiver and Amendment..........................................37
                --------------------
      15.5      Governing Law.................................................37
                -------------
      15.6      Captions; Certain Terms.......................................37
                -----------------------
      15.7      Counterparts..................................................37
                ------------
      15.8      Costs and Attorneys' Fees.....................................38
                -------------------------
      15.9      Expenses......................................................38
                --------
      15.10     Severability..................................................38
                ------------
      15.11     Rights Cumulative.............................................38
                -----------------
      15.12     Purchase from Tysan...........................................38
                -------------------
      15.13     Publicity.....................................................38
                ---------
      15.14     Specific Performance..........................................38
                --------------------
      15.15     No Third Party Beneficiaries..................................39
                ----------------------------
<PAGE>
 
                           ASSET PURCHASE AGREEMENT


     THIS ASSET PURCHASE AGREEMENT (this "Agreement") is made and entered into
                                          ---------                           
on the 14th day of December, 1998, by and among BioSource International, Inc. a
Delaware corporation ("BioSource"), Biofluids, Inc., a Maryland corporation
                       ---------                                           
("Biofluids") and Robert R. Rafajko, Ph.D (the "Biofluids Stockholder").
-----------                                                               
Biofluids is sometimes referred to herein as "Seller."  BioSource is sometimes
                                              ------                          
referred to herein as "Purchaser."

                                    RECITALS
                                    --------

     WHEREAS, subject to the terms and conditions set forth in this Agreement,
Seller desires to sell and transfer to BioSource, and BioSource desires to
purchase and acquire from Seller the Business (as defined below).

                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the foregoing premises and the mutual
promises herein made, and in consideration of the representations, warranties
and covenants herein contained, the parties agree as follows:

                            SECTION  1.  DEFINITIONS

      1.1 Definitions.  As used in this Agreement, the following terms shall
          -----------                                                       
have the following meanings:
 
          "Accounts Receivable" has the meaning set forth in Section 622.
           -------------------                                           

          "Affiliate" means with respect to any particular Person, any Person
           ---------                                                         
controlling, controlled by or under common control with, such Person.

          "Agreement" means this Agreement and includes each Exhibit and
           ---------                                                    
Schedule delivered pursuant to the terms of this Agreement.

          "Arbitration Notice" has the meaning set forth in Section 133(b).
           ------------------                                              

          "Arbitration Panel" has the meaning set forth in Section 133(a).
           -----------------                                              

          "Assumed Liabilities" has the meaning set forth in Section 41.
           -------------------                                          
<PAGE>
 
          "Balance Sheet Date" means the date of the Biofluids Balance Sheet,
           ------------------                                                
October 31, 1998.

          "Basket Amount" has the meaning set forth in Section 11.10.
           -------------                                             

          "Biofluids Balance Sheet" has the meaning set forth in Section 68.
           -----------------------                                          

          "Biofluids Financial Statements" has the meaning set forth in Section
           ------------------------------                                      
68.

          "Biofluids Stockholder" means Robert R. Rafajko, Ph.D.
           ---------------------                                

          "Business" means the manufacture and sale of high quality serum, media
           --------                                                             
and buffers.

          "Claim" has the meaning set forth in Section 114.
           -----                                           

          "Closing" has the meaning set forth in Section 51.
           -------                                          

          "Closing Date" has the meaning set forth in Section 51.
           ------------                                          

          "Direct Claim" has the meaning set forth in Section 114.
           ------------                                           

          "Disclosure Schedule" has the meaning set forth in Section 6.
           -------------------                                         

          "Employees" has the meaning set forth in Section 617.
           ---------                                           

          "Escrow Agent" means Union Bank of California, N.A.
           ------------                                      
 
          "Escrow Funds" has the meaning set forth in Section 31.
           ------------                                          

          "Escrow Instrument" has the meaning set forth in Section 9.1(n).
           -----------------                                              

          "Exchange Act" means the Securities Exchange Act of 1934, as amended.
           ------------                                                        

          "Excluded Assets" means those properties and assets listed on Schedule
           ---------------                                              --------
2.2.
--- 

          "GAAP" means generally accepted accounting principles.
           ----                                                 

          "Governmental Approval" means any consent of any Governmental
           ---------------------                                       
Authority.

          "Governmental Authority" means any nation or government, any state or
           ----------------------                                              
other political subdivision thereof, any entity exercising executive,
legislative, judicial, regulatory or administrative functions of or pertaining
to government, including, without limitation, any multilateral authority or any
government authority, agency, department, board, commission or

                                       2
<PAGE>
 
instrumentality of the United States, any State of the United States or any
political subdivision thereof, and any tribunal or arbitrator(s) of competent
jurisdiction, and any self-regulatory organization.

          "Hazardous Substances" means any natural or artificial substance,
           --------------------                                            
preparation or article which if generated, transported, stored, treated, used or
disposed of (alone or combined with any other substance, preparation or article)
is harmful to water, air or land or any living organism.

          "Indemnified Party" has the meaning set forth in Section 11.4.
           -----------------                                           

          "Indemnifying Party" has the meaning set forth in Section 11.4.
           ------------------                                           

          "Intellectual Property" means any and all United States and foreign:
           ---------------------                                              
(a) patents (including design patents, industrial designs and utility models)
and patent applications (including docketed patent disclosures awaiting filing,
reissues, divisions, continuations-in-part and extensions), patent disclosures
awaiting filing determination, inventions and improvements thereto; (b)
trademarks, service marks, trade names, trade dress, logos, business and product
names, slogans, and registrations and applications for registration thereof; (c)
copyrights (including software) and registrations thereof; (d) inventions,
processes, designs, formulae, trade secrets, know-how, industrial models,
confidential and technical information, manufacturing, engineering and technical
drawings, product specifications and confidential business information; (e)
intellectual property rights similar to any of the foregoing; and (f) copies and
tangible embodiments thereof (in whatever form or medium, including electronic
media).

          "Intellectual Property Assets" has the meaning set forth in Section
           ----------------------------                                      
6.15(a).

          "Inventory"  means all raw material, work in process and finished
           ---------                                                       
goods inventory of the Business located at the premises or at other facilities
of Seller  which is usable by the Business in the ordinary course of its
business, and including all such inventory set forth on Schedule 6.20, less only
                                                        ------------           
those items listed therein sold by Biofluids in the ordinary course of its
business.

          "Knowledge" of Biofluids means actual knowledge of the Biofluids
           ---------                                                       
Stockholder, or any officer or director of Biofluids, after reasonable
investigation.

          "Leases" means any real or personal property leases, subleases,
           ------                                                        
licenses and occupancy agreements pursuant to which Biofluids is the lessee,
sublessee, licensee or occupant other than real property leases, subleases,
licenses and occupancy agreements included in Excluded Assets.

          "Liens" shall include any encumbrance, lien, charge, hypothecation,
           -----                                                             
pledge, mortgage, title retention agreement, security interest of any nature,
adverse claim, exception, reservation, easement, right of occupation, any matter
capable of registration against title, option,

                                       3
<PAGE>
 
right-of-preemption, privilege or any agreement, indenture, contract, lease,
deed of trust, license, option, instrument or other commitment to create any of
the foregoing.

          "Losses" means any and all costs, demands, claims, liabilities, fines,
           ------                                                               
penalties, assessments, damages and expenses (including the burden and expense
of defending against all of the foregoing even if the assertions therein are
groundless, false or fraudulent), or amounts paid in settlement thereof, and
court costs (including court-awarded interest) and reasonable attorneys' fees
and disbursements of counsel (including legal or other expenses reasonably
incurred in connection with investigating or defending the same); provided, that
                                                                  --------      
the term "Losses" shall not include costs, demands, claims, liabilities, fines,
penalties, assessments, damages and expenses which are indirect or consequential
in nature.
 
          "Material Adverse Effect" means any event, occurrence, fact,
           -----------------------                                    
condition, change or effect that is materially adverse to the business,
operations, prospects, results of operations, condition (financial or
otherwise), properties (including intangible properties), assets (including
intangible assets) or liabilities of the Business, not otherwise disclosed,
permitted or reflected in this Agreement.

          "Material Contracts" has the meaning set forth in Section 6.6(b).
           ------------------                                          

          "Notices" has the meaning set forth in Section 15.1.
           -------                                           

          "Other Material" has the meaning set forth in Section 15.2.
           --------------                                            

          "Permit" means any license, permit, order, approval or Governmental
           ------                                                            
Approval from any Governmental Authority.

          "Permitted Liens" means
           ---------------       

               (i) liens for taxes, assessments and governmental charges due and
     being contested in good faith and diligently by appropriate proceedings
     (and for the payment of which adequate provision has been made);

               (ii) servitudes, easements, restrictions, rights-of-way and other
     similar rights in real property or any interest therein, including without
     limitation, those existing at the Closing Date in favor of Biofluids;
     provided the same are not of such nature as to materially adversely affect
     --------                                                                  
     the use of the property subject thereto;

               (iii) liens for taxes either not due and payable or due but for
     which notice of assessment has not been given;

               (iv) undetermined or inchoate liens, charges and privileges
     incidental to current construction or current operations and statutory
     liens, charges, adverse claims, security

                                       4
<PAGE>
 
     interests or encumbrances of any nature whatsoever claimed or held by any
     governmental authority that have not at the time been filed or registered
     against the title to the asset or served upon the Seller pursuant to law or
     that relate to obligations not due or delinquent;

               (v) liens or rights reserved in any lease for rent or for
     compliance with the terms of such lease;

               (vi) security given in the ordinary course of the Business to any
     public utility, municipality or government or to any statutory or public
     authority in connection with the operations of the Business, other than
     security for borrowed money;

               (vii) statutory liens in favor of a seller of personal property,
     mechanic's liens or other statutory liens in favor of a provider of a
     service; provided, that obligations to a secured party are not overdue or
              --------                                                        
     delinquent; and

               (viii) the Liens described on Schedule 6.3.
                                             ------------ 

          "Person" means any individual, corporation, trust, estate,
           ------                                                   
partnership, joint venture, joint stock company, association, unincorporated
organization, governmental bureau or other entity of whatsoever kind or nature.

          "Plans" has the meaning set forth in Section 6.18.
           -----                                           

          "Purchase Price" has the meaning set forth in Section 3.1.
           --------------                                          

          "Purchased Assets" has the meaning set forth in Section 2.1
           ----------------                                         

          "Records" has the meaning set forth in Section 10.3.
           -------                                           

          "Regulation S-X" has the meaning set forth in Section 8.6.
           --------------                                           

          "Rules of Arbitration" has the meaning set forth in Section 13.3.
           --------------------                                           

          "Third Party" has the meaning set forth in Section 11.6.
           -----------                                            

          "Third Party Claim" has the meaning set forth in Section 11.4.
           -----------------                                           

          "Tysan" has the meaning set forth in Section 15.12.
           -----                                             


                                       5

<PAGE>
 
                    SECTION 2.  SALE AND TRANSFER OF ASSETS

      2.1 Purchased Assets.  On the terms and subject to the conditions set
          ----------------                                                 
forth in this Agreement, on the "Closing Date" (as that term is defined in
                                 ------------                             
Section 51 of this Agreement) Seller agrees to sell, convey, assign, transfer
and deliver to Purchaser,  free and clear of any and all Liens of any type, kind
or nature (other than Permitted Liens and those which Purchaser expressly agrees
to assume pursuant to Section 41 of this Agreement), all of the properties,
assets, powers and rights, wherever located, including, but not limited to, the
name "Biofluids," held by Seller or used or usable by Seller in connection with
the operation and conduct of the Business, other than the Excluded Assets
referred to in Section 22 below (the "Purchased Assets"), as of and as the same
                                      ----------------                         
shall exist on the Closing Date, and Purchaser agrees to purchase and acquire
the Purchased Assets from Seller, for the Purchase Price provided in Section 31
of this Agreement.

      2.2 Excluded Assets.  Notwithstanding anything to the contrary contained
          ---------------                                                     
in Section 2.1 hereof, the Purchased Assets shall not include, and Seller shall
retain for its own use and benefit those other properties and assets of Seller
listed on Schedule 2.2 to this Agreement (the "Excluded Assets").
          ------------                         ---------------   

      2.3 Delivery of Possession.  At the Closing, Seller shall, at Seller's
          ----------------------                                            
expense, deliver to Purchaser physical possession of the Purchased Assets, at
Biofluids' facilities in Rockville, Maryland.

      2.4 Right of Endorsement; Payment.  After the Closing Date, Purchaser
          -----------------------------                                    
shall have the absolute and unconditional right and authority (subject to
promptly providing to Seller a full accounting) to endorse, without recourse,
the name of Seller on any check or any other evidence of indebtedness received
by Purchaser on account of any Purchased Asset, and Seller shall deliver to
Purchaser at the Closing a letter of instruction executed by Seller sufficient
to permit Purchaser to deposit such checks or other evidences of indebtedness in
bank accounts in the name of Purchaser. In addition, if after the Closing Date,
Seller receives any payment on account of the Purchased Assets, Seller will,
each business day, remit all payments to Purchaser.  To the extent Seller
receives, by direct deposit into its bank accounts, any payment after the
Closing Date on account of the Purchased Assets, Seller shall, at the end of
each business day, deliver to Purchaser an accounting of all payments received
and shall, at the end of each week, transfer to Purchaser the aggregate amounts
so received during the week.  To the extent Purchaser receives a check or other
evidence of indebtedness unrelated to the Purchased Assets, Purchaser will
promptly return such payment to Biofluids.

                           SECTION  3.  CONSIDERATION

      3.1 Purchase Price.  The Purchased Assets shall be purchased by Purchaser
          --------------                                                       
from Seller for an aggregate purchase price (the "Purchase Price") consisting of
                                                  --------------                
$2,700,000 in cash payable to Seller as follows: (i) $1,680,000 at Closing, (ii)
$750,000 on January 4, 1999 and (iii) $270,000 (the "Escrow Funds") to be held
                                                     ------------             
and paid or offset pursuant to Section 11.12 below and pursuant to the

                                       6
<PAGE>
 
terms of the Escrow Instrument, at the conclusion of the period ending eighteen
(18) months following the Closing. The Escrow Funds shall be held in an interest
bearing account, such interest accruing on a pro rata basis to the party
receiving the Escrow Funds.

      3.2 Allocation of Purchase Price.  BioSource and Biofluids shall agree on
          ----------------------------                                         
the allocation of the Purchase Price among the Purchased Assets as soon as
practicable following the Closing.

      3.3 Prorations/Adjustments.  Rent, utility charges, common area charges
          ----------------------                                             
and other costs and expenses, including personal property taxes payable with
respect to Leases included in the Purchased Assets shall be prorated as of the
Closing Date, and payable, to the extent possible, by a dollar-for-dollar
adjustment to the Purchase Price on the Closing Date, and if not paid on the
Closing Date, then paid within 30 days of the Closing Date.

      3.4 Form of Payments.  All amounts to be paid by any party pursuant to
          ----------------                                                  
this Agreement at the Closing shall be paid by banker's check or by irrevocable
wire transfer to a bank account established by the payee, such payment to be in
Los Angeles Clearinghouse or equivalent "next day" funds.

                     SECTION  4.  ASSUMPTION OF LIABILITIES

      4.1 Assumed Liabilities.  Subject to the provisions of this Agreement,
          -------------------                                               
Purchaser agrees that upon transfer of the Purchased Assets on the Closing Date,
it shall assume, pay, satisfy, discharge, perform and fulfill, to the extent not
paid, satisfied, performed, discharged or fulfilled by Seller on or before the
Closing Date only the following obligations of Seller (collectively, the
"Assumed Liabilities"), and none other:
--------------------                   

          (a) the contracts, agreements, arrangements, etc. described in
Schedules 6.6  except that  those contracts, agreements, arrangements, etc.
-------------                                                              
referred to in Section 6.6 which are not set forth on Schedule 6.6 because they
                                                      ------------             
require payments, discounts or expenditures in amounts less than the amounts set
forth in such sections shall also constitute Assumed Liabilities;

          (b) the Permits, agreements or arrangements described in Schedules
                                                                   ---------
6.10 and 6.15(d);
---------------- 

          (c) the agreements entered into by Seller in the ordinary course of
the Business for the provision of services or goods to Seller including, without
limitation, agreements with suppliers listed in Schedule 6.13;
                                                ------------- 

          (d) the agreements entered into by Seller in the ordinary course of
the Business for the sale of Inventory by Seller; and

          (e) all liabilities for employee compensation, benefits, vacation pay,
sick leave, severance payments, social security, and payroll taxes, whether
under individual or collective labor

                                       7
<PAGE>
 
agreements or under the Plans (as defined in Section 6.18), existing at or
accruing from and after the Closing Date which relate to employees of Seller
employed by Purchaser after the Closing Date and involved in the Business.

          It is not the intention of either Purchaser or Seller that the
assumption by Purchaser of the Assumed Liabilities shall in any way enlarge the
rights of third Persons under any agreements or arrangements with Purchaser or
Seller.  Nothing contained herein shall in any way prevent Purchaser from
contesting in good faith any of the Assumed Liabilities with any third Person
obligee; provided no contestation shall relieve Purchaser of its obligations
         --------                                                           
hereunder to Seller with respect thereto.

      4.2 Liabilities Not Assumed.  Purchaser shall not and does not assume any
          -----------------------                                              
liabilities, obligations or commitments of Seller of any kind, known or unknown,
contingent or otherwise, of whatsoever kind or nature, not specifically included
within the Assumed Liabilities, and the same shall remain the sole
responsibility of Seller.

      4.3 Right of Enforcement and Settlement.  From and after the Closing Date,
          -----------------------------------                                   
Purchaser shall have complete control over the payment, settlement or other
disposition of the Assumed Liabilities and the right to commence, conduct and
control all negotiations and proceedings with respect thereto.  Seller shall
notify Purchaser promptly of any claim made with respect to any such Assumed
Liability and shall not, except with Purchaser's prior written consent, which
may arbitrarily be withheld by Purchaser, voluntarily make any payment of,
settle or offer to settle, or consent to any compromise or admit liability with
respect to, any such Assumed Liability.  Seller shall cooperate with Purchaser
in any reasonable manner requested by Purchaser in connection with any
negotiations or proceedings involving any Assumed Liabilities.

                              SECTION  5.  CLOSING

      5.1 The Closing Date.  The Closing of the purchase and sale of the
          ----------------                                              
Business (the "Closing") shall take place at 9:00 a.m. on December __, 1998, or
               -------                                                         
at such time as the parties hereto agree, at the offices of Troop Steuber Pasich
Reddick & Tobey, LLP, 2029 Century Park East, Los Angeles, CA 90067.  The date
and time of the Closing is herein referred to as the "Closing Date."

      5.2 Actions and Deliveries by Seller at the Closing.  At the Closing,
          -----------------------------------------------                  
Seller shall deliver to Purchaser the following instruments in form and
substance satisfactory to Purchaser:

          (a) such bills of sale, endorsements, assignments, subleases, and
other good and sufficient instruments of conveyance, transfer and assignment,
including without limitation, a Bill of Sale in the form of Exhibit 5.2 to this
                                                            -----------        
Agreement, as shall be necessary or appropriate to vest in Purchaser, good title
in and to the Purchased Assets, free and clear of any and all Liens (other than
Permitted Liens and Assumed Liabilities);

                                       8
<PAGE>
 
          (b) any terminations of Liens or other security interests necessary
for the consummation of the transactions contemplated by this Agreement or as
may be required to permit Seller to deliver the Purchased Assets free and clear
of any and all Liens (other than Permitted Liens and Assumed Liabilities); and

          (c) the documents, instruments and evidences of the satisfaction of
all of the conditions precedent set forth in Section 91 of this Agreement.

      5.3 Actions and Deliveries by Purchaser at the Closing.  At the Closing,
          --------------------------------------------------                  
Purchaser shall deliver:

          (a) to Seller or as it may otherwise direct in writing, the cash
portion of the Purchase Price due at Closing as set forth in Section 3.1 above;
and

          (b) to Seller, the following instruments in form and substance
reasonably satisfactory to or for the account of Seller:

               (i) any acceptances of assignments required in connection with
the transfer and delivery of the Purchased Assets and the assumption of the
Assumed Liabilities; and

               (ii) the documents, instruments and evidences of the satisfaction
of the conditions precedent provided for in Section 9.2 of this Agreement.

          (c) to the Escrow Agent, the Escrow Funds.

           SECTION  6.  REPRESENTATIONS AND WARRANTIES OF BIOFLUIDS
                         AND THE BIOFLUIDS STOCKHOLDER

     As a material inducement to Purchaser to enter into this Agreement and to
perform its obliga  tions hereunder and thereunder Biofluids and the Biofluids
Stockholder jointly and severally represent and warrant to and agree with
Purchaser as follows, except as set forth in the disclosure schedule attached
hereto (the "Disclosure Schedule").  The Disclosure Schedule shall be initialed
             -------------------                                               
by Purchaser and Biofluids and the Biofluids Stockholder and shall be arranged
in paragraphs corresponding to the numbered and lettered paragraphs contained in
this Section 6 and the disclosure in any paragraph of the Disclosure Schedule
shall qualify only the corresponding paragraph in this Section 6 to the extent
apparent on its face.

      6.1 Organization, Standing and Corporate Power.  Biofluids is a
          ------------------------------------------                 
corporation duly organized, validly existing and in good standing under the laws
of the State of Maryland, and has full power and authority (corporate and other)
to own its properties and assets and carry on its business as presently
conducted.  Biofluids is duly qualified to conduct business and is in good
standing in each jurisdiction in which the property owned, leased or operated by
it or the nature of the business conducted by it makes such qualification
necessary and where the failure to be so

                                       9
<PAGE>
 
qualified would be reasonably expected to have a Material Adverse Effect on
Biofluids. Biofluids has all approvals, permits and licenses necessary for the
conduct of its business and operations as currently conducted which approvals,
permits and licenses are valid and in full force and effect.

      6.2 Authority and Capacity.  Biofluids  has full power and authority
          ----------------------                                          
(corporate and other) to enter into, execute and deliver this Agreement and to
perform its respective obligations hereunder. The execution and delivery of this
Agreement, and the consummation of the transactions contemplated hereby, have
been duly authorized by the Board of Directors of Biofluids, and no other
corporate proceedings on the part of either are necessary to authorize this
Agreement and the trans  actions contemplated hereby.  This Agreement has been
duly executed and delivered by Biofluids, and constitutes the valid and binding
obligations of Biofluids, enforceable against Biofluids in accordance with its
terms.

      6.3 Title to the Assets.
          ------------------- 

          (a) Except as set forth in Schedule 6.3, Biofluids has good and
                                     ------------                        
marketable title to all of the Purchased Assets, including, but not limited to,
all of the properties and assets reflected on the Biofluids Balance Sheet,
wherever located, free and clear of all Liens other than Permitted Liens, other
than properties or assets held under valid Leases which are in full force and
effect and not in default.

          (b) Except as set forth in Schedule 6.3, the Purchased Assets to be
                                     ------------                            
transferred to Purchaser hereunder are adequate for the operation of the
Business as presently conducted, constitute all of the properties and assets,
tangible and intangible, applicable to or used in connection with the operation
of the Business as it is being conducted on the date hereof, and are in good
operating condition and repair, ordinary wear and tear excepted, and in the
stated maintenance, repair and operating condition reasonably required for the
proper operation and use thereof in the ordinary course of the Business.

          (c) Schedule 6.3 sets forth the address, name of landlord and term of
              ------------                                                     
the lease of Biofluids' facilities. The Lease with respect to such property is
valid, enforceable and effective in accordance with its terms; all rentals,
royalties and other monetary obligations thereunder payable have been fully
paid; there is not under the Lease any existing or claimed default by Biofluids
or, to the Knowledge of Biofluids, of any other party thereto; there is not
under the Lease any event or condition which with or without notice or the
passage of time, or both, would constitute a default by Biofluids or, to the
Knowledge of Biofluids, of any other party thereto; and Biofluids enjoys
peaceable and undisturbed possession under the Lease. The Lease is not
encumbered by any Liens, other than Permitted Liens.

      6.4 Rights of First Refusal on Assets.  Neither Biofluids nor the
          ---------------------------------                            
Purchased Assets are subject to any right of first refusal of any third party
relating to the sale of any of the Purchased Assets or the Business.

                                      10
<PAGE>
 
      6.5 Effect of Agreement.  The sale by Biofluids of the Purchased Assets to
          -------------------                                                   
Purchaser at the Closing, the performance by each of its respective obligations
pursuant to the terms of this Agreement, and the consummation of the
transactions contemplated hereby, do not and will not, with or without the
giving of notice or passage of time, or both:

          (a) violate or conflict with any term of the certificate of
incorporation, bylaws or other organizational documents of Biofluids;

          (b) violate any provision of law, statute, rule, regulation or
executive order of any Governmental Authority relating to the Business to which
Biofluids is subject or by which the Purchased Assets are bound or affected;

          (c) violate any judgment, order, writ or decree of any court or
administrative body applicable to the Business or by which the Purchased Assets
are bound or affected;

          (d) require on the part of Biofluids any filing with, or any permit,
authorization, consent or approval of, any court, arbitrational tribunal,
administrative agency or commission or other governmental or regulatory
authority or agency;

          (e) accelerate or constitute an event entitling the holder of any
indebtedness related to the Business and assumed hereunder by Purchaser to
currently accelerate the maturity of any such indebtedness or increase the rate
of interest presently in effect with respect to such indebtedness; or

          (f) result in the breach of, constitute a default under, constitute an
event which with notice or passage of time, or both, would become a default
under, or result in the creation of any mortgage, Lien, security interest,
charge or encumbrance upon any of the Purchased Assets under any agreement,
commitment, contract (written or oral) or other instrument to which Biofluids is
a party, or by which the Purchased Assets are bound or affected.

      6.6 Contracts, Agreements, Arrangements, Etc.
          -----------------------------------------

          (a) Except as set forth on Schedule 6.6, neither Biofluids is a party
                                     ------------                              
to, nor are any of the Purchased Assets bound by, any:

                 (i) license agreement, assignment or contract (whether as
licensor or licensee, assignor or assignee) relating to trademarks, trade names,
patents or copyrights (or applications therefor), know-how or technical
assistance, or other proprietary rights (other than trademark agreements which
are entered into in the ordinary course of Biofluids' business) which relates to
the Business;

                 (ii) agreement or other arrangement for the sale of goods or
services by the Business to any government or Governmental Authority (other than
pursuant to open purchase

                                      11
<PAGE>
 
orders issued by such entities) at an aggregate price per agreement or
arrangement in excess of $10,000;

                 (iii) agreement with any labor union or otherwise relating to
employees of Biofluids;

                 (iv) agreement with any vendor, distributor, dealer, sales
agent or representative relating to the Business other than contracts or orders
for the purchase or sale of goods at an aggregate price per contract or order of
more than $10,000;

                 (v) agreement with any distributor or customer of the Business
with respect to discounts (other than those reflected on Biofluids' current
price lists or in distribution or sale agreements duly disclosed under this
Agreement) or allowances or extended payment terms, where each such discount,
allowance or extended payment term has a value in excess of $5,000;

                 (vi) joint venture or partnership agreement with any other
Person which relates to the Business;

                 (vii) agreement guaranteeing, indemnifying or otherwise
becoming liable for the obligations or liabilities of another in connection with
the Business;

                 (viii) agreement appointing any Person as a distributor or
subdistributor with respect to the Business;

                 (ix) agreement for the making of any capital expenditure
relating to the Business in excess of $10,000;

                 (x) agreement giving any customer of the Business the right to
require a reduction in prices or the repayment of any amount previously paid
other than discounts in the ordinary course or agreements disclosed under this
Agreement;

                 (xi) any agreement (or group of related agreements) for the
lease of personal property from or to third parties with annual payments
exceeding $25,000;

                 (xii) any agreement concerning noncompetition;

                 (xiii) any written arrangement (or group of related written
arrangements) under which it has (A) created, incurred, assumed, or guaranteed
(or may create, incur, assume or guarantee) indebtedness in excess of $25,000 or
(B) imposed (or may impose) a Lien (other than Permitted Liens) on any of its
assets, tangible or intangible;

                 (xiv) any other contract or group of related contracts with the
same party requiring payments after the date hereof to or by Biofluids of more
than $20,000;

                                      12
<PAGE>
 
                 (xv) any contract with any stockholder or Affiliate of any
stockholder;

                 (xvi) other agreement, not included in or expressly excluded
from the terms of the foregoing clauses (i) through (xv), which would have a
Material Adverse Effect on the Purchased Assets or the Business; or

                 (xvii) other agreement, not included in or expressly excluded
from the terms of the foregoing clauses (i) through (xvi), which would require
the payment by BioSource of an amount in excess of $20,000.

          (b) Correct and complete copies of all agreements, indentures,
mortgages, plans, policies, arrangements and other instruments and written
amendments thereto (or, where they are oral, written summaries of the material
terms thereof), required to be shown on Schedule 6.6 or which, except for their
                                        ------------                           
inclusion on other Schedules to this Agreement, would have been shown on
                                                                        
Schedule 6.6 (collectively referred to herein as the "Material Contracts") have
------------                                          ------------------       
been separately delivered to Purchaser prior to the date hereof.

          (c) Each of the Material Contracts is valid, in full force and effect
and is enforceable against Biofluids and, to the Knowledge of Biofluids, against
the other party thereto in accordance with its terms.

          (d) There has not occurred any default by Biofluids or any event
which, with notice or the passage of time and/or the election of any person
other than Biofluids will become a default, nor to the Knowledge of Biofluids
has there occurred any default by others or any event which, with notice or the
passage of time and/or the election of Biofluids, will become a default under
any of the Material Contracts, nor, to the Knowledge of Biofluids has there
occurred any default by any other party to any of the Material Contracts, except
defaults, if any, which (i) have not resulted and will not result in any
material loss to or liability of the Business, or (ii) have been indicated on
Schedule 6.6 or on Schedule 6.24.
------------       ------------- 

          (e) Except as set forth on Schedule 6.7 referred to below, each of the
                                     ------------                               
Material Contracts is assignable by Biofluids to Purchaser without the consent
of the other parties thereto.

      6.7 Consents.  Schedule 6.7 sets forth a complete and accurate list of all
          --------   ------------                                               
approvals, authorizations, consents, orders or other actions of, or filings
with, any Person that are required to be obtained or made by Seller in
connection with the execution of, and the consummation of the transactions
contemplated under, this Agreement, including, without limitation, the effective
transfer and conveyance to the Purchaser of the Purchased Assets.

                                      13
<PAGE>
 
      6.8 Financial Statements.
          -------------------- 

          (a) Attached as Schedule 6.8 to this Agreement are the unaudited
                          ------------                                    
balance sheets and supporting schedules of Biofluids as of December 31, 1996 and
December 31, 1997 and the related statement of operations and statement of cash
flows for the periods then ended; and the unaudited balance sheet of Biofluids
as of October 31, 1998 (the "Biofluids Balance Sheet").  All of the financial
                             -----------------------                         
statements, including the notes thereto, referred to in the preceding sentence
are sometimes collectively referred to herein as the "Biofluids Financial
                                                      -------------------
Statements".
----------  

          (b) All of the Biofluids Financial Statements:

                (i) are in accordance with the books and records of Biofluids;

                (ii) present fairly the financial condition of Biofluids as of
the date of such Biofluids Financial Statements and the results of its
operations and its cash flows for the periods therein specified; and

                (iii) were prepared in accordance with GAAP and the valuation
rules adopted by the Board of Directors of Biofluids applied on a basis
consistent with prior accounting periods.

          (c) As of the dates of the Biofluids Financial Statements, Biofluids
did not have any liabilities or obligations, either accrued, absolute,
contingent or otherwise, which have not been reflected, and which are required
to be reflected in accordance with GAAP and the valuation rules adopted by the
Board of Directors of Biofluids, in the Biofluids Financial Statements, other
than liabilities or obligations which are disclosed in Schedule 6.8.
                                                       ------------ 

      6.9 Litigation.  Except as set forth in Schedule 6.9  to this Agreement,
          ----------                          ------------                    
there is no claim, legal action, suit, arbitration, investigation or hearing,
notice of claims or other legal, administrative or governmental proceedings
relating to the Business or the Purchased Assets pending or, to the Knowledge of
Biofluids, threatened against Biofluids or any of the Purchased Assets (or in
which Biofluids is plaintiff or otherwise a party thereto), and, to the
Knowledge of Biofluids, there are no facts existing which are likely to result
in any such claim, action, suit, arbitration, investigation, hearing, notice of
claim or other legal, administrative or governmental proceeding.  Biofluids has
not waived any statute of limitations or other affirmative defense with respect
to any of the Assumed Liabilities.  There is no continuing order, injunction or
decree of any court, arbitrator or Governmen  tal Authority relating to the
Business to which Biofluids is a party or to which it or any of the Purchased
Assets is subject.

      6.1 Compliance with the Law and Other Instruments. The operation of the
          ---------------------------------------------                      
Business has been and is being conducted in accordance with all material
applicable laws, ordinances, rules and regulations, judgments and decrees of all
Governmental Authorities applicable to the Business.  No investigations by any
Governmental Authorities asserting or alleging any violation of or

                                      14
<PAGE>
 
noncompliance with any such material applicable laws, ordinances, rules and
regulations, judgments and decrees are pending or, to the Knowledge of
Biofluids, threatened. To the Knowledge of Biofluids, Schedule 6.10 sets forth a
                                                      -------------
true and complete list of all Permits necessary to the conduct of the Business
as currently conducted. Biofluids has obtained all of such Permits, each of
which is in full force and effect. No violation of any Permit has occurred which
is continuing and no proceeding is pending or, to the Knowledge of Biofluids,
threatened to revoke or limit any such Permit.

      6.1 Absence of Certain Changes or Events.  Since the Balance Sheet Date,
          ------------------------------------                                
there has not been any change in, or event affecting, the condition (financial
or otherwise), business, properties, assets, liabilities, operations or
prospects of the Business other than changes in the ordinary course of its
Business, none of which has (either when taken by itself or when taken in
conjunction with any other or all such other changes) had a Material Adverse
Effect on the Business.  Except as set forth in Schedule 6.11, since the Balance
                                                -------------                   
Sheet Date, the Business has not:

          (a) suffered any adverse change in, and no events have occurred which,
individually or in the aggregate, have had, or may have, any Material Adverse
Effect on the Business;

          (b) incurred damage to or destruction of any of the Purchased Assets
of the Business by casualty, whether or not covered by insurance, which,
individually or in the aggregate, exceeded $10,000 in value;

          (c) made or granted any wage or salary increase to any employee or
paid any bonus, for which Purchaser shall be obligated, to any employee (other
than as required by law or contract existing at the date of this Agreement)
since the date of the payroll listing set forth on Schedule 6.11 hereto; entered
                                                   -------------                
into any employment agreement with any officer or employee which is not
terminable on thirty days notice; or entered into or instituted any new Plans
(as defined herein);

          (d) made any loans which have not been repaid to its employees other
than travel advances made in the ordinary course of business and consistent with
past practice and any individual salary advance not in excess of $5,000 made to
nonmanagement employees in the ordinary course of business and consistent with
past practice;

          (e) mortgaged, pledged or subjected to Lien or any other encumbrance
any of the Purchased Assets other than the Assumed Liabilities and Permitted
Liens;

          (f) amended or terminated any of its contracts, agreements, leases or
arrangements which otherwise would have been set forth on Schedule 6.6 to this
                                                          ------------        
Agreement if such termination would have a Material Adverse Effect;

          (g) waived or released any other rights with a value over $10,000;

                                      15
<PAGE>
 
           (h) entered into any transaction that has not been disclosed in a
Schedule to this Agreement and which is not in the ordinary course of business;
or

           (i) agreed to do any of the actions described in the preceding
subsections (a) through (h).

      6.12 Operation of the Business.  Except as set forth in Schedule 6.12, (a)
           -------------------------                          -------------     
Seller currently conducts the Business only through Biofluids and not through
any other divisions or any other Affiliate of Biofluids and (b) no part of the
Business is operated by Biofluids through any entity other than Biofluids.

      6.13 Suppliers; Raw Materials.  Schedule 6.13 sets forth (a) the names and
           ------------------------   -------------                             
addresses of all suppliers from which Biofluids ordered raw materials, supplies,
merchandise and other goods and services with an aggregate purchase price for
each such supplier of $25,000 or more during the twelve-month period ended
October 31, 1998 and (b) the amount for which each such supplier invoiced
Biofluids in such period.

      6.14 Absence of Certain Business Practices.  To the Knowledge of 
           -------------------------------------   
Biofluids, neither Biofluids nor any officer, employee or agent of Biofluids,
nor any other person acting on their behalf, has, directly or indirectly, since
January 1, 1997 given or agreed to give any gift or similar benefit to any
customer, supplier, governmental employee or other person who is or may be in a
position to help or hinder the Business (or assist Biofluids in connection with
any actual or proposed transaction relating to the Business) (i) which subjected
Biofluids to any damage or penalty in any civil, criminal or governmental
litigation or proceeding, (ii) which if not given in the past, might have had a
Material Adverse Effect, (iii) which if not continued in the future, might have
a Material Adverse Effect or subject Biofluids to suit or penalty in any private
or governmental proceeding, or (iv) for the purpose of establishing or
maintaining any concealed fund or concealed bank account.

      6.15 Intellectual Property.
           --------------------- 

           (a) Title.  Schedule 6.15(a) contains a complete and correct list of 
               -----   ---------------- 
all Intellectual Property that is owned by Biofluids and primarily related to,
currently used in, held for current use in connection with, or currently
necessary for the conduct of, or otherwise material to the Business (the
"Intellectual Property Assets") other than Intellectual Property that is both
-----------------------------                                                
not registered or subject to application or registration and not material to the
Business as currently conducted.  The Intellectual Property Assets comprise all
of the Intellectual Property necessary for Purchaser to conduct and operate the
Business as it is now being conducted by Biofluids.

           (b) Transfer.  Immediately after the Closing, Purchaser will own all
               --------                                                        
of the Intellectual Property Assets free from any Liens  (other than Permitted
Liens) subject to any notices or transfer filings or registrations which
Biofluids will effect or support pursuant to Section 10.1.

                                      16
<PAGE>
 
          (c) No Infringement.  Except as set forth on Schedule 6.15(c), the 
              ---------------                          ----------------   
conduct of the Business does not infringe or otherwise conflict with any rights
of any Person in respect of any Intellectual Property. To the Knowledge of
Biofluids, none of the Intellectual Property Assets is being infringed or
otherwise used or available for use by any other Person.

          (d) Licensing Arrangements.  Schedule 6.15(d) sets forth all 
              ----------------------   ---------------- 
agreements or arrangements (i) pursuant to which Biofluids has licensed
Intellectual Property Assets to, or the use of Intellectual Property Assets has
been otherwise permitted (through settlement or similar agreements) by, any
other Person and (ii) pursuant to which Biofluids has had Intellectual Property
licensed to it or has otherwise been permitted to use Intellectual Property
(through settlement or similar agreements). All of the agreements or
arrangements set forth on Schedule 6.15(d) (x) are in full force and effect in
                          ----------------
accordance with their terms and no default exists thereunder by Biofluids, or to
the Knowledge of Biofluids, by any other party thereto, (y) are free and clear
of all Liens, other than Permitted Liens and Assumed Liabilities and (z) do not
contain any change in control or other terms or conditions that will become
applicable or inapplicable as a result of the transactions contemplated by the
Agreement. Biofluids has delivered to Purchaser true and complete copies of all
licenses and arrangements (including amendments) set forth on Schedule 6.15(d).
                                                              ---------------- 

          (e) No Intellectual Property Litigation.  Except as set forth on
              -----------------------------------                         
Schedule 6.15(e), no claim or demand of any Person has been made nor is there 
----------------
any proceeding that is pending or to the Knowledge of Biofluids, threatened,
which (i) challenges the rights of Biofluids in respect of any Intellectual
Property Assets, (ii) asserts that Biofluids is infringing or otherwise in
conflict with, or is, except as set forth in Schedule 6.15(d), required to pay
                                             ----------------
any royalty, license fee, charge or other amount with regard to any Intellectual
Property, or (iii) claims that any default exists under any agreement or
arrangement listed on Schedule 6.15(d). None of the Intellectual Property Assets
                      ----------------
is subject to any outstanding order, ruling, decree, judgment or stipulation by
or with any court, arbitrator, or administrative agency, or has been the subject
of any litigation within the last five years, whether or not resolved in favor
of Biofluids.

          (f) Due Registration, Etc.  Schedule 6.15(f) sets forth the 
              ---------------------   ----------------    
Intellectual Property Assets and the filing offices, domestic or foreign, where
such Intellectual Property Assets have been registered, issued or filed.
Biofluids has taken such other actions that Biofluids considers reasonably
necessary to ensure full protection under any applicable laws or regulations,
and such registrations, filings, issuances and other actions remain in full
force and effect, in each case to the extent material to the Business.

          (g) Use of Name and Mark.  Except as set forth in Schedule 6.15(g), 
              --------------------                          ----------------    
there are, and immediately after the Closing will be, no contractual restriction
or limitations pursuant to any orders, decisions, injunctions, judgments, awards
or decrees of any Governmental Authority on Purchaser's right to use the name
and mark "Biofluids" in the conduct of the Business as presently carried on by
Biofluids.

                                      17
<PAGE>
 
     6.16 Environmental Matters.  Biofluids  has obtained all necessary permits
          ---------------------                                                
for the storage, production and use of all Hazardous Substances which have been
and are in its possession or under its control.  Such storage, production and
use have not resulted in the release or discharge into the environment (which
for the avoidance of doubt includes the soil and sub-soil) of any Hazardous
Substances in a manner which would give rise to liability to Purchaser under
environmental laws currently in effect.

     6.17 Employees.  Schedule 6.17 is a true and complete list of all current
          ---------   -------------                                           
employees (the "Employees") of Biofluids who primarily perform services in
                ---------                                                 
connection with the operation or conduct of the Business, together with their
current rates of compensation, all written employment contracts and collective
bargaining agreements and all other agreements or arrangements providing for
compensation to Employees, to which Biofluids is a party or by which Biofluids
is bound.  At the Closing, Schedule 6.17 will also contain, for each employee,
                           -------------                                      
all accrued but unpaid vacation and sick pay earned by such employee.  Biofluids
has delivered to Purchaser accurate and complete copies of all such contracts,
agreements and arrangements and all handbooks, manuals and other writings
describing Biofluids' employment policies applicable to the Employees.  There
are no commissions due and owing to any Employee which are currently due and
payable and which have not been paid in full. Except as set forth on Schedules
                                                                     ---------
6.17 and 6.18, Biofluids is not a party to, or subject to any present obligation
-------------                                                                   
(statutory or otherwise), liability or commitment with respect to, any written
employment, compensation, consulting, severance pay or similar agreement
relating to any Employee, and Biofluids is not now, nor will be liable in the
future for any material termination payment or benefit payable to any Employee
as a consequence of the transaction contemplated by this Agreement.

     6.18 Employee Benefit Plans, Etc.  Schedule 6.18 contains a true and
          ---------------------------   -------------                    
complete list of each employee benefit plan, fringe benefit plan, vacation plan,
sick leave plan, retiree health plan, bonus plan, deferred compensation plan and
any other compensation agreements or plan or funding arrangement (collectively,
the "Plans") sponsored, maintained or contributed to by Biofluids or by any
     -----                                                                 
member of a group or organization of which Biofluids is a member under which any
Employee may be entitled to benefits.  Biofluids has delivered to Purchaser
accurate and complete copies of all documents embodying or relating to the
Plans, including a list of the Employees eligible for coverage and the benefits
available under each such Plan.  Except as disclosed on Schedule 6.18, all Plans
                                                        -------------           
have in the past been, and are now, in all respects maintained, funded and
administered in compliance with all applicable law.

     6.19 Customers.  Schedule 6.19 contains a correct and complete list of each
          ---------   -------------                                             
of the customers of the Business who have purchased from Biofluids products
and/or services in excess of 10% of Biofluids' revenues during the twelve months
ended October 31, 1998, and indicates the dollar value of the products and/or
services purchased by each such customer.

     6.20 Inventory.  Set forth on Schedule 6.20 is a correct and complete list
          ---------                -------------                               
as of October 31, 1998, of all items which constitute Inventory on such date,
indicating for each item of Inventory where it is located.  All of the Inventory
is of a quality and quantity saleable at regular prices or 

                                      18
<PAGE>
 
usable by Purchaser in the ordinary course of business of Purchaser, net of
reserves reflected on the balance sheet of Biofluids as of October 31, 1998.

     6.21 Purchase and Sale Obligations.  Since the Balance Sheet Date, all
          -----------------------------                                    
purchase and sales orders and all other commitments for purchases and sales made
by or on behalf of Biofluids relating to the Business have been made in the
usual and ordinary course of business in accordance with Biofluids' normal
practices.

     6.22 Accounts Receivable.  Attached hereto as Schedule 6.22 is a true and
          -------------------                      -------------              
complete schedule of the accounts receivable of Biofluids as of October 31, 1998
(the "Accounts Receivable"), setting forth a description of the Accounts
      -------------------                                               
Receivable including the names and, at the Closing, the addresses of the account
debtors, the balance amount and aging as of the date indicated therein.  The
Accounts Receivable and all books, records and documents relating to the
Accounts Receivable were genuine and accurate as of October 31, 1998.  As of
October 31, 1998, each of the Accounts Receivable represented an undisputed,
bona fide sale and delivery of goods or services rendered or to be rendered,
subject to any reserve or allowance taken or made in respect thereof in
accordance with Biofluids' normal practices.  As of October 31, 1998, Biofluids
was the lawful owner of the Accounts Receivable.

     6.23 Tax Returns.  Biofluids has paid in full all ad valorem property taxes
          -----------                                                           
and other assessments levied on its assets and properties which have heretofore
become due and payable. Biofluids has withheld all proper and accurate amounts
from its employees and made provisions, deposited or paid over such withheld
amounts in full and complete compliance with the tax laws of the United States
and other applicable State or local laws, and has filed proper and accurate
Federal, State and local returns and reports and has paid all related taxes or
assessments (including penalties and interest) for all years and periods (and
portions thereof) for which any such returns and reports were due with respect
to corporate income, franchise, sales and use, personal property, local business
license, employee income, withholding, old age pension, unemployment, and all
other taxes.

     6.24 Insurance.  Set forth on Schedule 6.24 is a correct and complete list
          ---------                -------------                               
of (a) all currently effective insurance policies and fidelity and surety bonds
covering the Purchased Assets, and (b) for the three-year period ending on the
date hereof, (i) all accidents, casualties or damage occurring on or to the
Purchased Assets or relating to the Business or its products, and (ii) claims
for damages, contribution or indemnification and settlements (including pending
settlement negotiations) relating thereto.  Except as set forth on Schedule 
                                                                   --------
6.24, as of the date hereof there are no disputes with underwriters of any such
----
policies or bonds, and all premiums due and payable have been paid.  To the
Knowledge of Biofluids, there are no pending or threatened terminations or
premium increases with respect to any of such policies or bonds and, to the
Knowledge of Biofluids, there is no condition or circumstance applicable to the
Business, other than the sale of the Purchased Assets and assumption of the
Assumed Liabilities pursuant to this Agreement, which is likely to result in
such termination or increase.  The Business and the Purchased Assets are in
compliance with all conditions contained in such policies or bonds, which are
included in the Purchased Assets, except 

                                      19
<PAGE>
 
for non-compliance which, individually or in the aggregate, would not have a
Material Adverse Effect on the Business or the Purchased Assets.

     6.25 Powers of Attorney.  Except for powers of attorney given in the
          ------------------                                             
ordinary course of business to officers and directors of Biofluids and except as
set forth on Schedule 6.25, no person has been granted and currently holds any
             -------------                                                    
power of attorney to act on behalf of Biofluids in connection with any of the
Purchased Assets or the Business.

     6.26 Prepaid Expenses.  Set forth on Schedule 6.26 is a true, complete and
          ----------------                -------------                        
accurate list of all prepaid expenses, trade deposits, security deposits and
other similar assets of the Business, which in each case is in excess of
$10,000, and existing as of October 31, 1998.

     6.27 No Unrelated Liabilities.  As of the Closing Date, Purchaser will not
          ------------------------                                             
by reason of the transactions contemplated by this Agreement assume, acquire,
succeed to or be subject in any way to, any liability arising out of or in
connection with the Business other than the Assumed Liabilities or otherwise as
results from this Agreement.

     6.28 No Change of Control Provisions.  Biofluids is not a party nor subject
          -------------------------------                                       
to any agreement or contract which would require under the terms of such
agreement or contract the making by Purchaser or the Business of any payment,
other than payments contemplated by this Agreement, to any employee of the
Business or to any other Person as a result of the consummation of the
transactions contemplated herein.
 
     6.29 No Finder's Fee.  Except as set forth on Schedule 6.30, Biofluids has
          ---------------                          -------------               
not retained any finder, broker, agent or other party or incurred any liability
or is otherwise obligated for any brokerage fees, commissions, finder's fees or
investment banking fees in connection with this Agreement or the transactions
contemplated hereby.

     6.30 Accuracy of Other Information; Disclosure.  None of the information
          -----------------------------------------                          
contained in any certificate delivered or to be delivered by Biofluids to
Purchaser at the Closing, or contained in this Agreement, contains any untrue
statement of a material fact or omits to state any material fact necessary in
order to make the statements therein, in light of the circumstances under which
they were made or will be made, not materially misleading.  Biofluids has
disclosed to Purchaser all information known to it which it reasonably believes
to be material to a decision by Purchaser to acquire the Purchased Assets and
Assumed Liabilities hereunder.

            SECTION 7.  REPRESENTATIONS AND WARRANTIES OF BIOSOURCE

     As a material inducement to Biofluids to enter into this Agreement and to
perform its obligations hereunder and thereunder, BioSource represents and
warrants to and agrees with Biofluids as follows:

                                      20
<PAGE>
 
      7.1 Organization, Standing and Corporate Power.  BioSource is a
          ------------------------------------------                 
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware, with adequate corporate power and authority to own its
properties and carry on its business as presently conducted.  BioSource has the
corporate power to enter into, execute and deliver this Agreement and to
consummate the transactions contemplated hereby in accordance with its terms.

      7.2 Authorization of Agreement.  The execution and delivery of this
          --------------------------                                     
Agreement and the performance by BioSource of its obligations and agreements
under this Agreement will prior to the Closing have been duly and validly
authorized and approved by BioSource's Board of Directors. BioSource has taken,
and shall take prior to the Closing Date, all other actions required on its part
by law and its Certificate of Incorporation and Bylaws in order to consummate
the transactions contemplated hereby.

      7.3 Execution, Delivery and Performance. This Agreement constitutes the
          -----------------------------------                                
valid and binding obligations of BioSource, enforceable in accordance with its
terms.

      7.4 Effect of Agreement.  The execution and delivery of this Agreement do
          -------------------                                                  
not, and compliance by BioSource with the provisions hereof will not, (i)
conflict with or result in a breach or default under any of the terms,
conditions, or provisions of any note, bond, mortgage, indenture, license,
agreement or other instrument or obligation (including, without limitation,
BioSource's Certificate of Incorporation or Bylaws) to which BioSource is a
party or by which it may be bound; or (ii) violate any order, writ, injunction,
decree, statute, rule or regulation applicable to BioSource, which conflict,
breach, default or violation could have a Material Adverse Effect on BioSource,
or BioSource's ability to fulfill its obligations pursuant to this Agreement.

      7.5 No Consents Required.  There are no approvals, authorizations,
          --------------------                                          
consents, orders or other actions of, or filings with, any Governmental
Authority required to be filed by BioSource in connection with the consummation
of the transactions contemplated under this Agreement.

      7.6 No Finder's Fee.  BioSource has not retained any finder, broker, agent
          ---------------                                                       
or other party or incurred any liability or is otherwise obligated for any
brokerage fees, commissions, finder's fees or investment banking fees in
connection with this Agreement or the transactions contemplated hereby.

      7.7 Accuracy of Other Information; Disclosure.  None of the information
          -----------------------------------------                          
contained in any certificate delivered or to be delivered by BioSource to
Biofluids at the Closing, or contained in this Agreement, contains any untrue
statement of a material fact or omits to state any material fact necessary in
order to make the statements therein, in light of the circumstances under which
they were made or will be made, not materially misleading.  BioSource has
disclosed to Biofluids all information known to it which it reasonably believes
to be material to a decision by Biofluids to sell the Business hereunder.

                                      21
<PAGE>
 
             SECTION 8.  CONDUCT AND TRANSACTIONS PRIOR TO CLOSING

      8.1 Investigations.  Between the date of this Agreement and the Closing
          --------------                                                     
Date, Biofluids shall give to Purchaser and its representatives full access to
all of Biofluids'  premises, books, records, employees, bankers, independent
public accountants and other agents possessing any information relating in any
manner to the Business, and shall furnish Purchaser with such financial and
operating data and other information with respect to the business and properties
of the Business as Purchaser shall from time to time request; provided, however,
                                                              --------  ------- 
that any such investigation shall not affect any of the representations and
warranties hereunder; and provided, further, that any such investigation shall
                          --------  -------                                   
be conducted in such manner as not to interfere unreasonably with the operation
of the Business.  If this Agreement is terminated without the transactions
contemplated hereby having been effected, Purchaser and Biofluids shall each
return to the other all documents, working papers and other materials obtained
from the other party pursuant to this Agreement, and the confidentiality
provisions of Section 10.2 of this Agreement shall continue to apply.

      8.2 Operation of the Business Pending Closing.  Between the date hereof
          -----------------------------------------                          
and the Closing Date, unless Purchaser consents in writing to the contrary,
other than as provided for herein, Biofluids shall:

          (a) conduct the Business in the ordinary course in accordance with
prior practice;

          (b) make, amend and terminate contracts and operate only in the
ordinary course of business;

          (c) not create or incur indebtedness except current liabilities in the
ordinary course of business;

          (d) not suffer, create or incur any mortgage, security interest, Lien,
Lease, encumbrance or restriction on any of the Purchased Assets (other than
Permitted Liens);

          (e) duly comply with all laws, ordinances, rules and regulations
applicable to Biofluids and to the conduct of the Business;

          (f) not make or agree to make any capital expenditures in excess of
$10,000 in the aggregate;

          (g) not sell, lease, dispose of, convey or transfer or agree to sell,
lease, dispose of, convey or transfer any Purchased Assets, except sales from
Inventory in the ordinary course of business;

          (h) not incur any fixed or contingent obligation or enter into any
agreement, commitment or other transaction or arrangement relating to the
Business which (i) may not be 

                                      22
<PAGE>
 
terminated by Biofluids on 30 days' notice or less without cost or liability,
and (ii) which is not in the ordinary course of the Business, and (iii) which is
not transferrable or assignable to Purchaser;

          (i) use its best efforts to preserve its business organization, retain
its employees and preserve good relationships with suppliers, customers and
other persons having significant business relationships with the Business;

          (j) use its best efforts to keep available for possible retention by
Purchaser the services of the Employees;

          (k) not enter into any agreement, arrangement or undertaking with
respect to any Employee relating to the payment of any bonus, profit-sharing or
special compensation or any increase in the compensation payable to an Employee
(other than as required by law or contract) if any such payment will be incurred
by Purchaser;

          (l) maintain in full force and effect all existing insurance policies
and keep the Purchased Assets insured in accordance with present practice;

          (m) maintain the Purchased Assets in a good condition and state of
repair, except for reasonable wear and tear;

          (n) not sell, assign, license or transfer or agree to sell, assign,
license or transfer (with or without consideration) any of the Intellectual
Property Assets or any interest therein;

          (o) use its best efforts not to commit any act or omit to do any act
which would be or result in a breach of any of its obligations, duties,
agreements or representations under any agreement, contract or commitment to
which it is a party or to which it enters into subsequent to the date of this
Agreement which would have a Material Adverse Effect;

          (p) bear the risk of loss or damage to the Purchased Assets on and
prior to the Closing Date, and maintain all properties necessary for the conduct
of the Business, whether owned or leased, in substantially the same condition as
they now are, reasonable wear and tear excepted; and, in the event that any
Purchased Asset is damaged on or prior to the Closing Date by any casualty,
Biofluids shall give Purchaser immediate written notice of such damage, and, if
such damage or destruction has a Material Adverse Effect on the Business, shall
afford Purchaser, in its sole and absolute discretion, the right to cancel,
terminate or delay the Closing under this Agreement without further liability.

          (q) maintain the books, records and accounts of Biofluids in the
usual, regular and ordinary manner, on a basis consistent with prior periods;

                                      23
<PAGE>
 
          (r) not enter into any agreement of any kind or nature with any
Affiliate of Biofluids with respect to the Purchased Assets or the Business
other than transactions required to give effect to this Agreement;

          (s) not enter into any transaction or perform any act which would make
any of the representations, warranties or agreements contained in this Agreement
false or misleading in any material respect if made again immediately after such
transaction or act; and

          (t) not, directly or indirectly, sell, transfer or otherwise dispose
of, solicit any offer for the purchase or acquisition of, or engage in any
negotiations, discussions or agreements with any Person other than Purchaser the
purpose or result of which would be the sale, transfer or disposition of the
Business or any Purchased Assets, excepting only sales from Inventory and other
dispositions in the ordinary course of business.

      8.3 Advice of Changes.  If Biofluids becomes aware of any fact or facts
          -----------------                                                  
which, if known at the date of this Agreement, would have been required to be
set forth or disclosed in or pursuant to this Agreement or which, individually
or in the aggregate, materially adversely affects the Business, Biofluids shall
promptly advise Purchaser in writing thereof.

      8.4 Non-Disclosure or Use of Information.  BioSource agrees that, unless
          ------------------------------------                                
this Agreement is terminated, subject to Section 10.2, from and after the date
hereof, BioSource shall not use or disclose to any third party, other than in
the ordinary course of business, any information proprietary to Biofluids and
held by Biofluids or used by Biofluids in the Business, including, without
limitation, Biofluids's customer lists, except for the benefit of Purchaser and
with the prior written consent of Purchaser.

      8.5 Governmental and Third Party Consents and Approvals.  Prior to the
          ---------------------------------------------------               
Closing, Biofluids shall take all such actions as are reasonable and necessary
to:

          (a) prepare and file applications with any governmental agency or
multilateral body or other appropriate agency and any other necessary third
party for consent to the transactions contemplated by this Agreement or as may
be required to deliver the Purchased Assets in accordance with the terms and
subject to the conditions of this Agreement;

          (b) prosecute such applications with diligence;

          (c) diligently oppose any objections to, appeals from or petitions to
reconsider such governmental or third party approvals or consents; and

          (d) take all such further action as reasonably may be necessary to
obtain and maintain such consents.

                                      24
<PAGE>
 
      8.6 8-K Financial Statements.  Biofluids shall permit Purchaser access to
          ------------------------                                             
its books and records sufficient to allow Purchaser to prepare audited financial
statements and pro forma financial statements of the Business sufficient to
               --- -----                                                   
permit Purchaser to fully, completely and timely comply with Purchaser's
obligations, if any, to file financial statements relating to the Business under
and pursuant to the General Instructions to Form 8-K under the Exchange Act and
Rule 3-05 of Regulation S-X of the General Rules and Regulations under the
Exchange Act ("Regulation S-X"); provided that neither Biofluids nor any of its
               --------------    --------                                      
respective officers, directors or Affiliates shall have any liability to
Purchaser or any other Person in respect of or arising out of any financial
statements so prepared and filed, and Purchaser agrees to indemnify Biofluids
and its respective officers, directors and Affiliates in respect thereof in
accordance with the provisions of Section 11 herein.

                  SECTION 9.  CONDITIONS OF PURCHASE AND SALE

      9.1 Conditions to Obligations of Purchaser.  Unless waived, in whole or in
          --------------------------------------                                
part, in writing by Purchaser, the obligations of Purchaser to effect
consummation of the transactions contemplated by this Agreement shall be subject
to the fulfillment prior to or at the Closing Date of each of the following
conditions:

          (a) Representations and Warranties of Biofluids and the Biofluids
              -------------------------------------------------------------
Stockholder To Be True.  The representations and warranties of Biofluids and the
----------------------                                                          
Biofluids Stockholder (contained in this Agreement, any Exhibit or Schedule
hereto, or any certificate, instrument or other writing delivered to Purchaser
or its representatives by Biofluids, or any of its representatives) shall be
true and correct in all material respects on the Closing Date with the same
force and effect as though made on and as of the Closing Date (i.e., with
respect to a representation that a state of facts exists on or as of the date
hereof, it is a condition that such state of facts exists on or as of the
Closing Date, and with respect to a representation that a state of facts has or
has not changed between a date prior to the date hereof and the date hereof, it
is a condition that such state of facts has or has not changed between such
prior date and the Closing Date), except as affected by transactions
contemplated hereby and thereby and except that any such representation or
warranty made as of a specified date (other than the date of this Agreement)
shall only need to have been true on and as of such date.  Biofluids shall have
performed all obligations and complied with all covenants required by this
Agreement to be performed or complied with by Biofluids on or prior to the
Closing Date.

          (b) No Proceedings.  No action, suit or proceeding before any court or
              --------------                                                    
any governmental body or authority pertaining to the transactions contemplated
by this Agreement or to their consummation shall have been instituted or
threatened on or prior to the Closing Date.

          (c) No Adverse Change.  Since the date of this Agreement there shall
              -----------------                                               
not have been any change in the business, properties, prospects, results of
operations or condition (financial or otherwise) of the Business which,
individually or in the aggregate, is materially adverse.

                                      25
<PAGE>
 
          (d) Statutory Requirements.  All consents and approvals of all United
              ----------------------                                           
States, State and local Governmental Authorities, and any other person or
entity, required to be obtained to permit consummation by Biofluids of the
transactions contemplated by this Agreement or as may be required to deliver the
Purchased Assets free and clear of any Liens and encumbrances (not otherwise
permitted hereunder) shall have been obtained, and true and correct copies of
such consents and approvals shall have been delivered to Purchaser or its
counsel.

          (e) Certificates.  Biofluids shall have delivered to Purchaser a
              ------------                                                
certificate, dated the Closing Date, certifying that the conditions specified in
Sections 9.1(a), 9.1(b), 9.1(c) and 9.1(d) of this Agreement have been
satisfied.

          (f) Opinion of Counsel for Biofluids .  Purchaser shall have received
              ---------------------------------                                
from counsel for Biofluids, an opinion, dated the Closing Date, in form and
substance substantially identical to Exhibit 9.1(f) attached hereto.
                                     --------------                 

          (g) Audit.  A review of Biofluids' audit and accountant's work papers
              -----                                                            
shall have been completed by KPMG Peat Marwick prior to the Closing Date.

          (h) Releases of Security Interests.  Biofluids shall have delivered
              ------------------------------                                  
to Purchaser any required releases and/or termination statements, releasing all
security interests in favor of any third party in or to any of the Purchased
Assets except those which are in connection with the Assumed Liabilities and
Permitted Liens.

          (i) Consents. Biofluids shall have delivered all consents of third
              --------                                                      
parties necessary to the transfer of the Purchased Assets.

          (j) Authorization.  Biofluids shall have delivered to Purchaser
              -------------                                              
certified copies of resolutions adopted by its board of directors authorizing
the execution, delivery and performance of this Agreement and the consummation
of the transactions contemplated herein.

          (k) Receipt of Right of Endorsement.  Purchaser shall have received a
              -------------------------------                                  
letter of instruction executed by Seller sufficient to permit Purchaser to
deposit checks or other evidences of indebtedness in bank accounts in the name
of Purchaser.
 
          (l) Employment Agreement.  Purchaser shall have entered into an
              --------------------                                       
employment agreement with Robert R. Rafajko, Ph.D. substantially in the form
attached hereto as Exhibit 9.1(l).
                   ---------------
 
          (m) Non-Compete Agreement.  Purchaser shall have entered into a non-
              ---------------------                                          
compete agreement with Robert R. Rafajko, Ph.D. substantially in the form
attached hereto as Exhibit 9.1(m).
                   -------------- 

          (n) Escrow Instrument.  Purchaser shall have entered into an escrow
              -----------------                                              
instrument (the "Escrow Instrument") with Biofluids substantially in the form
                 -----------------                                           
attached hereto as Exhibit 9.1(n).
                   -------------- 

                                      26
<PAGE>
 
          (o) Other Matters.  All corporate and other proceedings and actions
              -------------                                                  
taken in connection with this Agreement and all certificates, opinions,
agreements, instruments and documents mentioned in this Agreement or incident to
any such transactions shall be reasonably satisfactory in form and substance to
Purchaser and its counsel.

          If any of the conditions contained in this Section 91 shall not be
performed or fulfilled at or prior to the Closing to the satisfaction of
Purchaser, Purchaser may, by notice to Biofluids, terminate this Agreement and
the obligations of Biofluids and Purchaser under this Agreement, other than the
obligations contained in Sections 10.2 and 13; provided that Purchaser may also
                                               --------                        
bring an action pursuant to Section 11 against Biofluids for damages, other than
incidental or consequential damages, suffered by Purchaser where the non-
performance or non-fulfillment of the relevant condition is as a result of a
breach of covenant, representation or warranty by Biofluids.

      9.2 Conditions to Obligations of Biofluids.  Unless waived, in whole or in
          --------------------------------------                                
part, in writing by Biofluids, the obligations of Biofluids to effect the
consummation of the transactions contem  plated by this Agreement shall be
subject to the fulfillment prior to or at the Closing Date of each of the
following conditions:

          (a) Representations and Warranties of Purchaser To Be True.  The
              ------------------------------------------------------      
representations and warranties of Purchaser (contained in this Agreement, any
Exhibit or Schedule hereto, or any certificate, instrument or other writing
delivered to Biofluids or its representatives by Purchaser, or any of its
representatives) shall be true and correct on the Closing Date with the same
force and effect as though made on and as of the Closing Date (i.e., with
                                                               ----      
respect to a representation that a state of facts exists on or as of the date
hereof, it is a condition that such state of facts exists on or as of the
Closing Date, and with respect to a representation that a state of facts has or
has not changed between a date prior to the date hereof and the date hereof, it
is a condition that such state of facts has or has not changed between such
prior date and the Closing Date), except as affected by transactions
contemplated hereby and thereby and except that any such representation or
warranty made as of a specified date (other than the date of this Agreement)
shall only need to have been true on and as of such date.  Purchaser shall have
performed all obligations and complied with all covenants required by this
Agreement to be performed or complied with by Purchaser on or prior to the
Closing Date.

          (b) Certificates.  Purchaser shall have delivered to Biofluids a
              ------------                                                
certificate of Purchaser dated the Closing Date certifying that the conditions
specified in Section 92 of this Agreement shall have been fulfilled.

          (c) Authorization.  Purchaser shall have delivered to Biofluids
              -------------                                              
certified copies of resolutions adopted by its board of directors authorizing
the execution, delivery and performance of this Agreement and the consummation
of the transactions contemplated hereby.

                                      27
<PAGE>
 
          (d) Opinion of Counsel for Purchaser.  Biofluids shall have received
              --------------------------------                                
from Troop Steuber Pasich Reddick & Tobey, LLP, counsel for Purchaser, an
opinion, dated the Closing Date, in the form of Exhibit 9.2(d) attached hereto.
                                                --------------                 

          (e) No Proceedings.  No action, suit or proceeding before any court or
              --------------                                                    
any Governmental Authority pertaining to the transactions contemplated by this
Agreement or to their consummation shall have been instituted or threatened on
or prior to the Closing Date.

          (f) Delivery of Purchase Price.  Purchaser shall have delivered to
              --------------------------                                    
Biofluids that portion of the Purchase Price due and payable at the Closing.

          (g) Escrow Instrument.  Purchaser and Biofluids shall have entered
              -----------------                                             
into an Escrow Instrument substantially in the form attached hereto as Exhibit
                                                                       -------
9.1(n).
------ 

          (h) Statutory Requirements.  All consents and approvals of all United
              ----------------------                                           
States, State and Governmental Authorities, and any other Person or entity,
required to be obtained to permit consummation by BioSource of the transactions
contemplated by this Agreement or as may be required to buy the Purchased Assets
shall have been obtained, and true and correct copies of such consents and
approvals shall have been delivered to Seller or its counsel.

          (i) Other Matters.  All corporate and other proceedings and actions
              -------------                                                  
taken in connection with this Agreement and all certificates, opinions,
agreements, instruments and documents mentioned in this Agreement or incident to
any such transactions shall be reasonably satisfactory in form and substance to
Biofluids and its counsel.

          If any of the conditions contained in this Section 9.2 shall not be
performed or fulfilled at or prior to the Closing to the satisfaction of
Biofluids acting reasonably, Biofluids may, by notice to Purchaser, terminate
this Agreement and the obligations of Biofluids and Purchaser under this
Agreement, other than the obligations contained in Sections 10.2 and 13; 
provided that Biofluids may also bring an action pursuant to Section 11 against
--------
Purchaser for damages, other than indirect or consequential damages, suffered by
it where the non-performance or non-fulfillment of the relevant condition is as
a result of a breach of covenant, representation or warranty by Purchaser.

                SECTION 10.  FURTHER AGREEMENTS OF THE PARTIES

     10.1 Further Agreements of Biofluids.  Biofluids shall upon the request of
          -------------------------------                                      
Purchaser from time to time execute and deliver to Purchaser such further bills
of sale, endorsements and other good and sufficient instruments of title,
conveyance, transfer and assignment as may be necessary or desirable in order to
vest in Purchaser, free and clear of all Liens and encumbrances (other than
Permitted Liens), all right, title and interest in and to any and all of the
Purchased Assets.

     10.2 Confidentiality.  Purchaser and Biofluids hereby acknowledge to and
          ---------------                                                    
agree with the other that any and all information which has been disclosed by
one to the other, its employees, 

                                      28
<PAGE>
 
consultants, agents and, if applicable, stockholders during the discussions and
negotiations leading to the execution of this Agreement, and all information to
be disclosed by one to the other, its employees, consultants and agents and, if
applicable, stockholders, during the period commencing on the date of execution
of this Agreement through the Closing or termination of this Agreement, shall
constitute confidential information and trade secrets of the disclosing party,
and as such are secret, confidential and unique and constitute the exclusive
trade secrets and property of such party. Such information has been made known
and available to the other party and its respective employees, consultants and
agents strictly in connection with the negotiation and execution of this
Agreement and the consummation of the transactions provided for herein. Each
party hereby acknowledges and agrees that any use or disclosure of any such
confidential information or trade secrets, other than pursuant to this
Agreement, would be wrongful and would cause irreparable injury to the other.
Accordingly, each party hereby expressly agrees, for itself and on behalf of its
stockholders and directors, if any, and its principal officers, managers,
employees, agents, consultants and representatives, that it and they will not at
any time prior to the Closing or at any time thereafter, use or disclose, other
than in accordance with the terms and provisions of this Agreement, any of such
confidential information or trade secrets; provided, that either Purchaser or
                                           --------        
Biofluids may use or disclose such confidential information or secrets of the
other without restriction if such information or secrets (i) were or are
available to such party on a non-confidential basis from a source other than the
other party; or (ii) were or become generally available to the public (other
than as a result of an impermissible disclosure by such party or its
Affiliates); and provided, further, that if either party is requested or
                 --------  -------
required (by oral question, interrogatories, requests for information or
documents, subpoena or similar process) to disclose any of such information or
secrets of the other, such disclosure, be made without liability hereunder
(although notice of such request or requirement shall be given to the other
party so that, if practicable, the other party may seek a protective order
against such disclosure). Notwithstanding the foregoing, no provision of this
Section 10.2 shall in any manner whatsoever prevent or inhibit Purchaser from
using or disclosing any such confidential information relating to the Business
or the Purchased Assets including, without limitation, customer lists in any
manner Purchaser shall deem fit from and after the Closing. Each party
acknowledges that, in the event of a violation by the other of the terms and
provisions of this Section 10.2, the remedies at law would not be adequate; and
accordingly, in such event such party may proceed to protect and enforce its
rights under this Section 10.2 by a suit in equity for specific performance
hereof, or for an injunction against the violation hereof.

     10.3 Access to Books and Records.  After the Closing Date, Purchaser and
          ---------------------------                                        
Biofluids shall grant to each other access to the books, records, papers and
documents relating to the Business (i) in the case of Purchaser, included in the
Purchased Assets, and (ii) in the case of Biofluids, not included in the
Purchased Assets which relate to the operation of the Business (the "Records").
                                                                     -------    
Such access shall be given upon the reasonable request of the requesting party
during normal business hours and upon five business days prior notice.  Each
party shall maintain the Records in its possession for a period of four years
from and after the Closing Date, and each shall first offer to the other such of
the Records as it may hereafter desire to dispose of or destroy at least 30 days
prior to initiating any disposition or destruction whether prior to or following
the aforementioned four-year period.

                                      29
<PAGE>
 
     10.4 Mail and Remittances.  After the Closing, all mail addressed to
          --------------------                                           
Biofluids and Purchaser relating to their respective businesses shall be
delivered promptly by each party to the other party.

     10.5 Change of Name.  Within 10 calendar days following the Closing,
          --------------                                                 
Biofluids shall change its corporate name from Biofluids, Inc. to Bonheur, Inc.

     10.6 Fetal Bovine Letters.  Biofluids agrees to use its reasonable best
          --------------------                                              
efforts to obtain an agreement from each of its purchasers of fetal bovine serum
in the form of Exhibit 10.6.

            SECTION 11.  NATURE AND SURVIVAL OF REPRESENTATIONS AND
                     WARRANTIES; INDEMNITY; OFFSET RIGHTS

     11.1 Nature and Survival of Representations and Warranties.  Except as
          -----------------------------------------------------            
provided herein, all of the covenants, representations and warranties and
indemnification obligations of the parties herein and in any certificate,
document or instrument delivered in connection with this Agreement shall survive
the Closing of the transactions contemplated hereby, and shall be binding upon
the parties to this Agreement, their successors and assigns for a period of
eighteen (18) months following the Closing, notwithstanding any investigation
made by or on behalf of the party entitled to the benefit thereof.
Notwithstanding the foregoing, the representations and warranties of Biofluids
and the Biofluids Stockholder set forth in Sections 6.3, 6.16 and 6.23 shall
survive the Closing and continue in full force and effect until the expiration
of the applicable statute of limitations.  No party will be liable for
indemnification pursuant to this Section 11 with respect to any breach of any
representation, warranty, covenant or obligation, unless such party is provided
with notice of a claim for indemnification with respect to such breach before
expiration of the applicable survival period described herein.  So long as
Purchaser delivers the applicable notice of a claim for indemnification prior to
the expiration of the date which is 18 months following the Closing, the amount
of the claim shall be retained in the Escrow Account and only the balance which
is not subject to the claim shall be released to Biofluids on such date.

     11.2 Indemnification by Biofluids and the Biofluids Stockholder.
          ----------------------------------------------------------   
Biofluids and the Biofluids  Stockholder hereby jointly and severally covenant
and agree with Purchaser that they shall indemnify and save harmless Purchaser
from, against and in respect of all Losses suffered or incurred by Purchaser as
a result of or arising directly or indirectly out of or in connection with:

          (a) any material breach by Biofluids or the Biofluids Stockholder of
or any inaccuracy of any representation or warranty of Biofluids or the
Biofluids Stockholder contained in this Agreement or in any certificate
delivered pursuant hereto;

          (b) any material breach or non-performance by Biofluids or the
Biofluids Stockholder of any covenant or agreement to be performed by it that is
contained in this Agreement or in any agreement or certificate delivered
pursuant hereto; and

                                      30
<PAGE>
 
          (c) the operations of the Business up to and including the Closing
Date.

     11.3 Indemnification by Purchaser.  Purchaser covenants and agrees with
          ----------------------------                                      
Biofluids and the Biofluids Stockholder to indemnify and save harmless Biofluids
and the Biofluids Stockholder from, against and in respect of all Losses
suffered or incurred by Biofluids or the Biofluids Stockholder as a result of or
arising directly or indirectly out of or in connection with:

          (a) any breach by Purchaser of or any inaccuracy of any representation
or warranty contained in this Agreement or in any certificate delivered pursuant
hereto;

          (b) any breach or non-performance by Purchaser of any covenant or
agreement to be performed by it that is contained in this Agreement or in any
agreement or certificate delivered pursuant hereto; and

          (c) the operations of the Business after the Closing Date including,
without limitation, any failure by Purchaser to pay, satisfy, discharge, perform
or fulfill any of the Assumed Liabilities.

     11.4 Notice of Claim.  In the event that a party (the "Indemnified Party")
          ---------------                                   -----------------  
shall become aware of any claim, proceeding or other matter (a "Claim") in
                                                                -----     
respect of which the other party (the "Indemnifying Party") agreed to indemnify
                                       ------------------                      
the Indemnified Party pursuant to this Agreement, the Indemnified Party shall
promptly give written notice thereof to the Indemnifying Party.  Such notice
shall specify whether the Claim arises as a result of a claim by a person
against the Indemnified Party (a "Third Party Claim") or whether the Claim does
                                  -----------------                            
not so arise (a "Direct Claim"), and shall also specify with reasonable
                 ------------                                          
particularity (to the extent that the information is available):

          (a)  the factual basis for the Claim;
 
          (b) the basis for the Indemnified Party's right to indemnification;
and

          (c) the amount of the Claim, if known.

          If, through the fault of the Indemnified Party, the Indemnifying Party
does not receive notice of any Claim in time to effectively contest the
determination of any liability susceptible of being contested, the Indemnifying
Party shall be entitled to set off against the amount claimed by the Indemnified
Party the amount of any Losses incurred by the Indemnifying Party resulting from
the Indemnified Party's failure to give such notice on a timely basis.

     11.5 Direct Claims.  With respect to any Direct Claim, following receipt of
          -------------                                                         
notice from the Indemnified Party of the Claim, the Indemnifying Party shall
have 45 days to make such investigation of the Claim as is considered necessary
or desirable.  For the purpose of such investigation, the Indemnified Party
shall make available to the Indemnifying Party sufficient information to
substantiate the Claim, together with all such other non-privileged information
as the 

                                      31
<PAGE>
 
Indemnifying Party may reasonably request. If both parties agree at or prior to
the expiration of such 45-day period (or any mutually agreed upon extension
thereof) to the validity and amount of such Claim, the Indemnifying Party shall
immediately pay to the Indemnified Party the full agreed upon amount of the
Claim. If the parties have not so agreed to the validity and/or amount of the
Claim, then the parties shall proceed in the manner set forth in the following
sentence. If the Closing shall have occurred under this Agreement, the matter
shall be resolved pursuant to the arbitration provisions contained in Section
13; and if the Closing shall not have occurred under this Agreement, the
Indemnified Party may bring an action against the Indemnifying Party in any
court located in Los Angeles, California.

     11.6 Third Party Claims.  With respect to any Third Party Claim, the
          ------------------                                             
Indemnifying Party shall have the right, at its expense, to participate in or
assume control of the negotiation, settlement or defense of the Claim.  Until an
Indemnifying Party notifies the Indemnified Party that the Indemnifying Party is
assuming the defense thereof, then the Indemnified Party may defend against the
matter in any manner it reasonably may deem appropriate, without prejudice to
any of its rights hereunder.  If the Indemnifying Party elects to assume such
control, the Indemnified Party shall have the right to retain counsel to act on
its behalf, provided that the fees and disbursements of such counsel shall be
paid by the Indemnified Party unless the Indemnifying Party consents to the
retention of such counsel or unless the named parties to any action or
proceeding include both the Indemnifying Party and the Indemnified Party and a
representation of both the Indemnifying Party and the Indemnified Party by the
same counsel would be inappropriate due to the actual or potential differing
interests between them (such as the availability of different defenses).  If the
Indemnifying Party, having elected to assume such control, thereafter fails to
defend the Third Party Claim within a reasonable time, the Indemnified Party
shall be entitled to assume such control and the Indemnifying Party shall be
bound by the results obtained by the Indemnified Party with respect to such
Third Party Claim.  If any Third Party Claim is of a nature such that the
Indemnified Party is required by applicable law to make a payment to any person
(a "Third Party") with respect to the Third Party Claim before the completion of
    -----------                                                                 
settlement negotiations or related legal proceedings, the Indemnified Party may
make such payment and the Indemnifying Party shall, forthwith after demand by
the Indemnified Party, reimburse the Indemnified Party for such payment.  If the
amount of any liability of the Indemnified Party under the Third Party Claim in
respect of which such a payment was made, as finally determined, is less than
the amount that was paid by the Indemnifying Party to the Indemnified Party, the
Indemnified Party shall, forthwith after receipt of the difference from the
Third Party, pay the amount of such difference to the Indemnifying Party.

     11.7 Settlement of Third Party Claims.  If the Indemnifying Party fails to
          --------------------------------                                     
assume control of the defense of any Third Party Claim, the Indemnified Party
shall have the exclusive right to contest, settle or pay the amount claimed.
Whether or not the Indemnifying Party assumes control of the negotiation,
settlement or defense of any Third Party Claim, the Indemnifying Party shall not
settle any Third Party Claim without the written consent of the Indemnified
Party, which consent shall not be unreasonably withheld or delayed.

                                      32
<PAGE>
 
    11.8  Cooperation.  The Indemnified Party and the Indemnifying Party shall
          -----------                                                         
cooperate fully with each other with respect to Third Party Claims, and shall
keep each other fully advised with respect thereto (including supplying copies
of all relevant documentation promptly as it becomes available).

    11.9  Adjustment to Indemnification Payments; Insurance; Subrogation.  Any
          --------------------------------------------------------------      
payment made by an Indemnifying Party to an Indemnified Party pursuant to this
Section 11 in respect of any Claim (i) shall be net of any insurance proceeds
available to the Indemnified Party in respect of such claim and (ii) shall be
reduced by an amount equal to any Tax benefits attributable to such Claim. The
Indemnified Party shall use its reasonable efforts to make insurance claims
relating to any claim for which it is seeking indemnification pursuant to this
Section 11.  The Indemnifying Party shall be subrogated to all rights of the
Indemnified Party in respect of any Losses borne by the Indemnifying Party.

    11.10 Basket on Indemnity.  No indemnity shall be payable to Purchaser with
          -------------------                                                  
respect to any Losses under Section 11.2 unless the aggregate amount due
thereunder with respect to all Losses shall exceed Fifty Thousand Dollars
($50,000) (the "Basket Amount"), whereupon all amounts then or thereafter due
                -------------                                                
with respect to such Losses in excess of the Basket Amount shall be payable.

    11.11 Limitation of Biofluids' Indemnification Liability.   Biofluids'
          --------------------------------------------------              
liability under the indemnification provisions set forth in this Section 11 will
be limited to fifty percent (50%) of the Purchase Price.
 
    11.12 Release of Escrow Funds.  Subject to the terms and conditions of the
          -----------------------                                             
Escrow Instrument, to the extent the Escrow Funds are not used for purposes of
indemnification of Purchaser, then Purchaser shall release the Escrow Funds,
less any amounts used to satisfy Purchaser's indemnification claims, to
Biofluids on the date which is eighteen (18) months from the Closing Date.

                              SECTION 12.  TAXES

    12.1  Payment of Taxes, Filing of Returns.  Biofluids shall remain liable
          -----------------------------------                                
for the filing of all tax returns and reports and for the payment of all
Federal, State and local taxes (other than payroll taxes to the extent expressly
included as part of the Assumed Liabilities) of Biofluids relating to the
operation of the Business for any period ending on or prior to the Closing Date,
and for the payment of all taxes attributable to or relating to the consummation
of the transactions contemplated herein and shall indemnify and hold Purchaser
harmless from and against all liability in connection therewith.

    12.2  Sales Taxes.  Subject to Section 4.1 hereof, Biofluids shall bear all
          -----------                                                         
responsibility for sales, use, value added or other similar taxes, if any,
arising out of the consummation of the transactions herein provided for and
shall be liable for the filing of all necessary tax returns and reports with
respect to such taxes.

                                      33
<PAGE>
 
               SECTION 13.  ARBITRATION; CONSENT TO JURISDICTION

     13.1 Submission to Jurisdiction.  BioSource, Biofluids and the Biofluids
          --------------------------                                          
Stockholder each hereby agree that any and all disputes, legal actions, suits,
or proceedings arising out of or relating to this Agreement or the transactions
contemplated hereby may be brought in any state or federal court located in Los
Angeles County, State of California.  By their signature to this Agreement,
BioSource, Biofluids and the Biofluids Stockholder each irrevocably submit to
the jurisdiction of the courts located in Los Angeles County, State of
California, in any dispute, legal action, suit, or proceeding arising out of or
relating to this Agreement or the transactions contemplated hereby.

     13.2 Waiver of Immunity and Inconvenient Forum.  BioSource and Biofluids
          -----------------------------------------                          
each hereby irrevocably waives all immunity from jurisdiction, attachment and
execution, whether on the basis of sovereignty or otherwise, to which it might
otherwise be entitled in any legal action or proceeding brought in any state or
federal court located in Los Angeles County, State of California, and further
irrevocably waives, to the fullest extent permitted by law, any objection which
it may now or hereafter have to any dispute, legal action, suit, or proceeding
arising out of or relating to this Agreement or the transactions contemplated
hereby being brought in any federal or state court located in Los Angeles
County, State of California, and hereby further irrevocably waives any claim
that any such dispute, legal action, suit, or proceeding brought in any such
court has been brought in an inconvenient forum.

     13.3 Arbitration Procedures.
          ---------------------- 

          (a) Except as otherwise expressly provided in Section 13.5 below, all
disputes arising in connection with this Agreement or any contract of sale
hereunder shall be finally settled by arbitration in Los Angeles, California, in
accordance with the Arbitration Rules of the American Arbitration Association
(the "Rules of Arbitration").  Judgment on the award rendered by the arbitration
      --------------------                                                      
panel (the "Arbitration Panel") may be entered in any court of competent
            -----------------                                           
jurisdiction.

          (b) Any party which desires to initiate arbitration proceedings may do
so by delivering written notice to the other party (the "Arbitration Notice")
                                                         ------------------  
specifying (x) the nature of the dispute or controversy to be arbitrated; (y)
the name and address of the arbitrator appointed by the party initiating such
arbitration; and (z) such other matters as may be required by the Rules of
Arbitration.  The party who receives an Arbitration Notice shall appoint an
arbitrator and notify the initiating party of such arbitrator's name and address
within 30 days after delivery of the Arbitration Notice; otherwise, a second
arbitrator shall be appointed by the American Arbitration Association at the
request of the party who delivered the Arbitration Notice.  The two arbitrators
so appointed shall appoint a third arbitrator who shall be chairman of the
Arbitration Panel and the "neutral arbitrator" for purposes of the Rules of
Arbitration.

     13.4 Final Arbitration Decisions.  All decisions of the Arbitration Panel
          ---------------------------                                         
shall be final, conclusive and binding on all parties and shall not be subject
to judicial review.  The parties 

                                      34
<PAGE>
 
expressly waive the provisions of California Code of Civil Procedure Section
1285 insofar as it permits a party to an arbitration in which an award has been
made to petition a court of competent jurisdiction to vacate an arbitration
award.

     13.5 Claims for Unpaid Balance.  Notwithstanding anything to the contrary
          -------------------------                                           
contained in this Section 13, any claim by either party for a "provisional
remedy" as defined in Section 1281.8 of the Rules of Arbitration, may be brought
in any court of competent jurisdiction, and any judgment, order or decree
relating thereto shall have precedence over any arbitral award or proceeding.

                           SECTION 14.  TERMINATION

     14.1 Termination.  This Agreement may be terminated at any time prior to
          -----------                                                        
the Closing:

          (a) by the mutual agreement of Biofluids and Purchaser; provided,
                                                                  -------- 
however, that such termination is set forth in a writing executed by both
-------                                                                  
parties;

          (b) by Purchaser, in a writing, if Biofluids or  the Biofluids
Stockholder are in breach, in any material respect, of any material
representation, warranty or covenant contained in this Agreement;

          (c) by Biofluids, in a writing, if Purchaser is in breach, in any
material respect, of any material representation, warranty or covenant contained
in this Agreement;

          (d) by either Purchaser or Biofluids, in a writing, if the Closing
does not occur on or prior to December 31, 1998, other than by reason of a
breach of a covenant to be performed hereunder of the party electing to
terminate this Agreement; or

          (e) by either Purchaser or Biofluids, in a writing, if any of the
conditions set forth in Section 9 are not met.

          In the event of such termination, no party shall have any obligation
or liability to any other in respect to this Agreement, except for any breach of
this Agreement occurring prior to such termination, or except as may be provided
in Section 10.2 of this Agreement; provided, however, that Section 15.9
(Expenses) and Section 15.13 (Publicity) shall survive any such termination and
shall continue in full force and effect.

                          SECTION 15.  MISCELLANEOUS

     15.1 Notices.  All notices, requests, demands and other communications
          -------                                                          
(collectively, "Notices") given or made pursuant to this Agreement shall be in
                -------                                                       
writing and shall be deemed to have been duly given if sent by registered or
certified mail, return receipt requested, postage and fees prepaid, by overnight
service with a nationally recognized "next day" delivery company such as 

                                      35
<PAGE>
 
Federal Express or United Parcel Service, by facsimile transmission, or
otherwise actually delivered to the addresses set forth below for Purchaser,
Biofluids and the Biofluids Stockholder. Any Notice shall be deemed duly given
when received by the addressee thereof, provided that any Notice sent by
registered or certified mail shall be deemed to have been duly given two
business days from the date of deposit in the United States mails, unless sooner
received. Any of the parties to this Agreement may from time to time change its
address for receiving notices by giving written notice thereof in the manner set
forth above.

                    (i)   if to Purchaser, to:

                    BioSource International, Inc.
                    820 Flynn Road, Suite A
                    Camarillo, California  93012
                    Fax No. (805) 987-0296
                    Attn: James H. Chamberlain
                          President

                    with a copy (which shall not constitute notice) to:
                    Troop Steuber Pasich Reddick & Tobey, LLP
                    2029 Century Park East, Suite 2400
                    Los Angeles, California 90067
                    Fax No. (310) 728-2222
                    Attn: Scott W. Alderton

                    (ii)  if to Biofluids or the Biofluids Stockholder
                          (prior to the Closing), to:

                    Biofluids, Inc.
                    1146 Taft Street
                    Rockville, MD 20850
                    Attn: Dr. Robert R. Rafajko
                          President

                          if to Biofluids or the Biofluids Stockholder
                          (after the Closing), to:

                    Dr. Robert R. Rafajko
                    12053 Weatherfield Lane
                    Potomac, MD 20854
 
                    with a copy (which shall not constitute notice) to:
                    Freedman, Levy, Kroll & Simonds
                    Washington Square

                                      36
<PAGE>
 
                    1050 Connecticut Avenue, NW
                    Washington, DC 20036
                    Attn: Jay W. Freedman

     15.2 Entire Agreement.   This Agreement, including the other agreements and
          ----------------                                                      
schedules to be entered into in connection with the transactions contemplated by
this Agreement, constitutes and embodies the entire understanding and agreement
of the parties hereto relating to the subject matter hereof and there are no
other agreements or understandings, written or oral, in effect between the
parties relating to such subject matter except as expressly referred to herein.
The representations and warranties made by Biofluids and the Biofluids
Stockholder in this Agreement, and the schedules that accompany this Agreement,
supersede, replace and nullify in every respect the data set forth in any other
document, material or statement, whether written or oral, made available to
Purchaser (the "Other Material") and Purchaser shall not rely on any data
                --------------                                           
contained in the Other Material for any purpose whatsoever, including, without
limitation, as a promise, projection, guaranty, representation, warranty or
covenant.

     15.3 Successors and Assigns.  This Agreement shall be binding upon and
          ----------------------                                           
inure to the benefit of the parties hereto and their respective successors and
assigns.  No party may assign any of its rights, or delegate any of its duties
or obligations (by operation of law or otherwise), under this Agreement without
the prior written consent of the other parties, and any such purported
assignment or delegation shall be void ab initio.

     15.4 Waiver and Amendment.  No provision of this Agreement may be waived
          --------------------                                               
unless in writing signed by all the parties to this Agreement, and the waiver of
any one provision of this Agreement shall not be deemed to be a waiver of any
other provision.  This Agreement may be amended only by a written agreement
executed by the parties to this Agreement.

     15.5 Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED BOTH
          -------------                                                         
AS TO VALIDITY AND PERFORMANCE AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF DELAWARE AND THE UNITED STATES OF AMERICA, WITHOUT REGARD TO THE
APPLICATION OF ANY STATE OR FEDERAL CONFLICTS OF LAWS RULES OR CHOICE OF LAW
PRINCIPLES THEREOF.

     15.6 Captions; Certain Terms.  The various captions and headings contained
          -----------------------                                              
in this Agreement are for reference only and shall not be considered or referred
to in resolving questions of interpretation of this Agreement.  As used in this
Agreement, the term "including" means "including but not limited to" unless
otherwise specified; the word "or" means "and/or."

     15.7 Counterparts.  This Agreement may be executed in any number of
          ------------                                                  
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.

                                      37
<PAGE>
 
    15.8  Costs and Attorneys' Fees.  If any action, suit or other proceeding
          -------------------------                                           
is instituted to remedy, prevent or obtain relief from a default in the
performance by any party of its obligations under this Agreement, the prevailing
party shall recover all of such party's costs and attorneys' fees incurred in
each and every such action, suit or other proceeding, including any and all
appeals or petitions therefrom.  As used in this Section 15.8, attorneys' fees
shall be deemed to mean the full and actual costs of any legal services actually
performed in connection with the matters involved calculated on the basis of the
usual fee charged by the attorney performing such services and shall not be
limited to "reasonable attorneys' fees" as defined in any statute or rule of
court.

    15.9  Expenses.  Except as otherwise provided in this Agreement each of the
          --------                                                             
parties shall pay its own costs and expenses, including, without limitation, the
fees and expenses of its counsel and financial advisors, incurred in connection
with the preparation of this Agreement and the consummation of the transactions
contemplated hereby and all documents reasonably necessary to effectuate the
terms and intent of this Agreement.

    15.10 Severability.  Whenever possible, each provision of this Agreement
          ------------                                                      
shall be interpreted in such a manner as to be effective and valid under
applicable law, but if any provision of this Agreement shall be or become
prohibited or invalid under applicable law, such provision shall be ineffective
to the extent of such prohibition or invalidity without invalidating the
remainder of such provision or the remaining provisions of this Agreement.

    15.11 Rights Cumulative.  No right granted to the parties under this
          -----------------                                             
Agreement on default or breach is intended to be in full or complete
satisfaction of any damages arising out of such default or breach, and each and
every right under this Agreement, or under any other document or instrument
delivered hereunder, or allowed by law or equity, shall be cumulative and may be
exercised from time to time.
 
    15.12 Purchase from Tysan.  On the day following the Closing Date, Purchaser
          -------------------                                                   
shall purchase from Tysan Serum, Inc. ("Tysan") 1,000 liters of fetal bovine
                                        -----                               
fluid for a purchase price equal to the price paid by Tysan plus an amount equal
to five percent (5%) of such price.  Tysan shall also deliver to Purchaser its
vendor lists.  Purchaser shall have no further obligations or liabilities to
Tysan following the purchase of the fetal bovine fluid.

    15.13 Publicity.  Purchaser, Biofluids and the Biofluids Stockholder agree
          ---------                                                           
that press releases and other announcements with respect to the transactions
contemplated hereby shall be subject to mutual agreement; provided, however,
that either party may make such announcement as, in the opinion of its counsel,
such party is required to make pursuant to applicable law, but in such event
such party shall, to the extent practicable, give the other party reasonable
prior notice and an opportunity to comment on the proposed announcement.

    15.14 Specific Performance.  Each of the parties acknowledges and agrees 
          --------------------  
that one or more of the other parties would be damaged irreparably in the event
any of the provisions of this Agreement are not performed in accordance with
their specific terms or otherwise are breached. 

                                      38
<PAGE>
 
Accordingly, each of the parties agrees that the other parties shall be entitled
to an injunction or injunctions to prevent breaches of the provisions of this
Agreement and to enforce specifically this Agreement and the terms and
provisions hereof in any action instituted in any court of the United States or
any state hereof having jurisdiction over the parties and the matter, in
addition to any other remedy to which it may be entitled, at law or in equity.

    15.15 No Third Party Beneficiaries.  Nothing in this Agreement shall confer
          ----------------------------                                         
any rights upon any person or entity other than the parties hereto.
 
    IN WITNESS WHEREOF, each of the parties hereto has executed or caused this
Agreement to be executed on its behalf all as of the day and year first above
written.
<PAGE>
 
                              "SELLER"

                              BIOFLUIDS, INC.


                              By:__________________________

                              Its:_________________________



                              BIOFLUIDS STOCKHOLDER


                              -----------------------------



                              "PURCHASER"

                              BIOSOURCE INTERNATIONAL, INC.


                              By:__________________________

                              Its:_________________________

 
<PAGE>
 
                                 SCHEDULES
                                 ---------

<TABLE>
<C>              <S> 
2.2    -         Excluded Assets
 
6.3    -         Title to Purchased Assets
 
6.6    -         Contracts
 
6.7    -         Biofluids Approvals, Authorizations, Consents
 
6.8    -         Financial Statements of Biofluids
 
6.9    -         Litigation
 
6.10   -         Permits
 
6.11   -         Absence of Changes; Payroll Listing
 
6.12   -         Conduct of Business
 
6.13   -         Suppliers Names & Addresses
 
6.15(a)-         Intellectual Property
 
6.15(c)-         Possible Infringements of Intellectual Property
 
6.15(d)-         Licensing Arrangements
 
6.15(e)-         Intellectual Property Litigation
 
6.15(f)-         List of Intellectual Property Assets and Filing Offices
 
6.15(g)-         Restrictions on Use of Name and Mark
 
6.17   -         Employees
 
6.18   -         Employee Benefit Plans
 
6.19   -         Customer List
</TABLE> 
<PAGE>
 
<TABLE> 
<C>              <S> 
6.20   -         Inventory
 
6.22   -         Accounts Receivable
 
6.24   -         Insurance Policies
 
6.25   -         Powers of Attorney
 
6.26   -         Prepaid Expenses
 
6.30   -         Finders' Fee
 
7.5    -         BioSource Approvals, Authorizations, Consents
</TABLE>
<PAGE>
 
                                   EXHIBITS
                                   --------

<TABLE>
<C>             <S> 
5.2       -     Form of Bill of Sale
 
9.1(f)    -     Form of Opinion of Counsel for Biofluids
 
9.1(l)    -     Form of Employment Agreement
 
9.1(m)    -     Form of Non-Compete Agreement
 
9.1(n)    -     Form of Escrow Instrument
 
9.2(d)    -     Form of Opinion of Counsel for BioSource
 
10.6      -     Form of Agreement from Fetal Bovine Serum Purchasers
</TABLE>