<PAGE>   1
                                 EXHIBIT 4.1






                              [GRAPHIC OMITTED]





                   AT FRANKFURT AM MAIN ON THIS JUNE 28, 2000


                     BEFORE ME THE UNDERSIGNED NOTARY PUBLIC
                               DR. HEINZ L. BAUER
                   WITH REGISTERED OFFICE AT FRANKFURT AM MAIN



THE FOLLOWING PARTIES APPEARED TODAY:


<PAGE>   2

Purchase Agreement ADL GmbH                                               Page 2

1.       Petra Urban, with business address c/o Bauer Gronen Kiesgen, 60486
         Frankfurt am Main, Hamburger Allee 1, demonstrating identity to the
         notary public by means of her personal identity card;

         hereinafter not acting on her own behalf but representing

         a.  Franz Maier, Am Haidengraben 7, 79199 Kirchzarten, *2.2.1952

         b.  Eva Heidt, Stuhlinger Strasse 32, 79106 Freiburg, *23.3.1959

         c.  Joachim Hevler, Am Haidengraben 11, 79189 Kirchzarten, *24.3.1961

         authorized by written Power of Attorney, issued on June 23, 2000,
         bearing the seal of the undersigned notary public. The Power of
         Attorney was produced to the notary in its original form and a
         notarized copy hereof is attached as SCHEDULE 0 hereto.

2.       Stephan Schmidt Esquire, with business address c/o SJ Berwin Knopf
         Tulloch, 60486 Frankfurt am Main, Hamburger Allee 1, demonstrating
         identity to the notary public by means of his personal identity card;

              hereinafter not acting on his own behalf but representing
              MATRITECH, Inc., with business address at 330 Nevada Street,
              Newton MA 02460 USA, authorized by written Power of Attorney,
              issued on June 20, 2000, bearing the seal of Julia S. Forbes,
              notary public, being certified by Apostille. The Power of Attorney
              was produced to the notary in its original form and a notarized
              copy hereof is attached as SCHEDULE 1 hereto.



At the request of the persons appearing this notarial deed is executed in the
English language, which the persons appearing are sufficiently capable of.

The notary inquires of the persons appearing whether he has been concerned
with the matter as defined in ss. 3 Abs. 1 Nr. 7 BeurkG. They declare that this
is not the case.

The persons appearing requested notarization of the following

<PAGE>   3

Purchase Agreement ADL GmbH                                               Page 3

                                    AGREEMENT

                for the sale and purchase of the entire shares in

                          ADL-VERTRIEBSGESELLSCHAFT mbH
        GESELLSCHAFT FUR ALLERGIE, DIAGNOSTIKA UND LABORKONZEPTE ("ADL")

<PAGE>   4

Purchase Agreement ADL GmbH                                               Page 4

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
<S>                                                                                      <C>
    Article I  Recitals................................................................... 5
    1      Introduction................................................................... 5
    2      Interpretation................................................................. 6
    3      Liability...................................................................... 7

    Article II  Sale and-Purchase......................................................... 7
    4      Sale and Assignment, Effective Date............................................ 7
    5      Consideration And Call Option.................................................. 8

    Article III  Representations and Warranties...........................................12
    6      General........................................................................12
    7      Representations and Warranties of Sellers with respect to
           the Shares, ADL and the ADL Business ..........................................12
    9      Representations and Warranties of Sellers with respect to
           the Acquisition Consideration .................................................27

    Article IV  Indemnification...........................................................29
    10     Indemnification by the Sellers, Payment........................................29
    11     Notification of Claims; Election to Defend.....................................31
    12     Notification of transfer of shares.............................................32
    13     Supplementary Contracts, Ancillary Documentation...............................33
    15     Notices........................................................................33
    16     Governing Law, Language, Place of Jurisdiction.................................34
    17     Announcements..................................................................34
    18     Fees and Expenses..............................................................35
    19     Loan Agreement.................................................................35
    20     Entire Agreement...............................................................36
    21     Severability...................................................................36
</TABLE>


<PAGE>   5

Purchase Agreement ADL GmbH                                               Page 5

                                    ARTICLE I
                                    ---------

                                    RECITALS

1          INTRODUCTION

1.1        ADL, which has its corporate domicile at Freiburg, Germany, and is
           registered in the Commercial Register of the municipal court of
           Freiburg under Ref.-No. HRB 5009 ("ADL"), is engaged in the business
           of the import, export and sale of equipment, tests and software for
           laboratories in the field of human, veterinary and environmental
           analysis especially in the areas of allergy and test-tube
           diagnostics, including service support, logistics and sales (the "ADL
           BUSINESS").

1.2        Franz Maier, Eva Heidt and Joachim Hevler (collectively, the
           "SELLERS") collectively own 100% of the issued share capital of ADL,
           which is in the total amount of 200,000DM (the "ADL SHARE CAPITAL").
           Each Seller holds property in the following number of shares of the
           ADL Share Capital:

<TABLE>
<CAPTION>

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

      NAME OF SHAREHOLDER          NUMBER OF SHARES      VALUE OF SHARES IN DM
 -------------------------------------------------------------------------------
<S>                                <C>                          <C>
          Franz Maier                     1                     43,000
 -------------------------------------------------------------------------------

                                          1                     30,000
 -------------------------------------------------------------------------------

                                          1                     12,500
 -------------------------------------------------------------------------------

                                          1                     10,000
 -------------------------------------------------------------------------------

                                          1                      7,000
 -------------------------------------------------------------------------------

                                          3                      5,000
 -------------------------------------------------------------------------------

                                          1                      2,500
 -------------------------------------------------------------------------------

           Eva Heidt                      1                     30,000
 -------------------------------------------------------------------------------
</TABLE>

<PAGE>   6

Purchase Agreement ADL GmbH                                               Page 6


<TABLE>
<S>                                      <C>                    <C>

                                          1                      5,000
 -------------------------------------------------------------------------------

                                          1                      5,000
 -------------------------------------------------------------------------------

        Joachim Hevler                    1                     40,000
 -------------------------------------------------------------------------------
</TABLE>


1.3        The aforementioned shares represent 100% of the totally paid up and
           outstanding share capital of ADL.

1.4        ADL is currently managed by a team made up of Franz Maier, Eva Heidt
           and Joachim Hevler.

1.5        MATRITECH, Inc., a corporation organized under the laws of the State
           of Delaware, USA (the "PURCHASER" or "MATRITECH") wishes to acquire
           all the shares referred to in Section 1.2 hereof (the "SHARES") from
           the Sellers by means of this purchase agreement (the "PURCHASE
           AGREEMENT") pursuant to the terms and conditions hereof.

2          INTERPRETATION

2.1        In this Purchase Agreement (including the Introduction and the
           Schedules), the following expressions shall have the following
           meanings:

           Business Days        means German business days

           BGB                  means the German Civil Code

           HGB                  means the German Commercial Code

           Domestic             means the Federal Republic of Germany

<PAGE>   7

Purchase Agreement ADL GmbH                                               Page 7

3          LIABILITY

3.1        The Sellers shall assume collective liability for their respective
           obligations incurred under the terms of this Purchase Agreement
           according to Sections 421 ff. BGB.

NOW, THEREFORE, in consideration of the mutual covenants, benefits, conditions
and agreements set forth herein, it is hereby agreed as follows:


                                  ARTICLE II
                                  ----------

                              SALE AND PURCHASE

4          SALE AND ASSIGNMENT, EFFECTIVE DATE

4.1        The Sellers hereby sell their respective Shares as set out in Section
           1.2. to the Purchaser who agrees to hereby purchase the respective
           Shares. The Sellers hereby assign their respective Shares to the
           Purchaser as of 12 pm today (the "EFFECTIVE DATE"). The Purchaser
           hereby assumes the respective Shares (Annahme der Abtretung) with
           effect from the Effective Date. For the avoidance of doubt: Among
           other things, all issued share capital and additional equity shall
           thereby be transferred to the Purchasers.

4.2        Each Seller hereby undertakes with the Purchaser at the request of
           the Purchaser to do or procure to be done all such further acts and
           things and execute or procure to be executed all such further deeds
           and documents as may be necessary or desirable fully and effectively
           to vest in the Purchaser the legal and beneficial ownership of the
           Shares and the benefits of this Purchase Agreement and any document
           specified herein and, pending such vesting, a Seller shall hold such
           Shares and benefits in trust
<PAGE>   8


Purchase Agreement ADL GmbH                                               Page 8


           for the Purchaser and shall receive all monies in connection
           therewith as trustee of the Purchaser and shall account to the
           Purchaser forthwith on receipt.

                                 ARTICLE III
                                 -----------
                          ACQUISITION CONSIDERATION
                          -------------------------

5          CONSIDERATION AND CALL OPTION

5.1.       In consideration for the sale and assignment of the Shares to the
           Purchaser, the Purchaser shall procure the issue to the Sellers in
           proportion of their respective shareholdings in ADL of that number of
           shares of the non-registered Common Stock of MATRITECH, $.01 par
           value (the "MATRITECH STOCK"), valued at the average of the quoted
           closing prices from 18 May 2000 through 16 June 2000 on the NASDAQ
           Stock Market (the "MARKET PRICE") at DM240,000 in aggregate (the
           "INITIAL CONSIDERATION"). The aggregate Consideration shall be split
           so that the Sellers receive MATRITECH Stock in the value of

           Franz Maier                               144,000DM

           Eva Heidt                                  48,000DM

           Joachim Hevler                             48,000DM.

           At the Effective Date the Purchaser shall pay to the Sellers the
           Initial Consideration by means of delivery of the respective share
           certificates to the Sellers. For the purposes of establishing the
           value of the Consideration in US dollars, the exchange rate is deemed
           to be $1 = DM2.0532, being the dollar spot rate published in the
           Financial Times newspaper of 16 June 2000.


<PAGE>   9

Purchase Agreement ADL GmbH                                               Page 9


5.1.1      A second payment (the "ADDITIONAL CONSIDERATION") will be made 60
           days after the completion of a financial audit of ADL for the fiscal
           year ended December 31, 2000. This payment will be calculated by
           multiplying 20% by the increase in year 2000 revenues over year 1999
           revenues of DM3,580,000,--. If year 2000 revenues exceed
           DM4,395,000,-- the amount of the excess over 4,395,000,-- will be
           multiplied by 40% and this result will be added to the Additional
           Consideration.

5.1.2      This Additional Consideration, if any, shall be paid to the Sellers
           in shares of MATRITECH Stock the number of which shares will be
           determined by dividing the payment amount by the same Market Price
           used to calculate the payment in Section 5.1, pro rata in the same
           proportions as the Initial Consideration is shared among the Sellers.
           The Initial Consideration and the Additional Consideration are
           collectively referred to as the "CONSIDERATION."

           The Sellers agree that they will not sell, assign, transfer, pledge
           or otherwise dispose of any of the shares of MATRITECH Stock received
           by them under this Purchase Agreement prior to the first anniversary
           of the Effective Date or while any of such shares are subject to the
           Call Option described in Section 5.2. Thereafter the Sellers agree
           that they will only sell or dispose of such shares in accordance with
           the terms of this Purchase Agreement and applicable securities laws.

 5.2.      The Sellers - each separately - herewith grant the Purchaser a call
           option (the "CALL OPTION") in the event of them leaving ADL, under
           the circumstances described in Section 5.3, as follows:

           Conditionally subsequent to and subject to (unter der aufschiebenden
           Bedingung) the occurrence of a Trigger Event (as defined below) each
           Seller herewith offers for sale to the Purchaser all or part of his
           MATRITECH Stock received as the Consideration under the following
           terms:

           (i)      In the event that a Trigger Event occurs with respect to a
                    Seller on or before the first anniversary of the Effective
                    Date, the Call Option

<PAGE>   10

Purchase Agreement ADL GmbH                                              Page 10

                    will cover all MATRITECH Stock received by that Seller as
                    Consideration at a price of 5% of the quoted price of such
                    MATRITECH Stock on the NASDAQ Stock Market at the close of
                    business on the day the Trigger Event occurs or the next
                    business day, if such Trigger Event does not occur on a
                    business day;

           (ii)     In the event that a Trigger Event occurs with respect to a
                    Seller after the first anniversary but on or before the
                    second anniversary of the Effective Date, the Call Option
                    will cover 67% of all MATRITECH Stock received by that
                    Seller as Consideration at a price of 5% of the quoted
                    price of such MATRITECH stock on the NASDAQ Stock Market at
                    the close of business on the day the Trigger Event occurs or
                    the next business day, if such Trigger Event does not occur
                    on a business day;

           (iii)    In the event that a Trigger Event occurs with respect to a
                    Seller after the second anniversary but on or before the
                    third anniversary of the Effective Date, 33% of all
                    MATRITECH Stock received as Consideration by that Seller at
                    a price of 5% of the quoted price of such MATRITECH shares
                    on the NASDAQ Stock Market at the close of business on the
                    day the Trigger event occurs or the next business day, if
                    such Trigger Event does not occur on a business day.

           All such offers may be accepted by the Purchaser within 4 weeks by
           written notice to the Sellers who is subject to the Trigger Event
           separately and any sale shall be completed on receipt of such notice.
           The Seller shall take all such actions as necessary and or
           appropriate to transfer title in such shares to the Purchaser. The
           Purchaser shall be entitled, at its sole discretion, to provide any
           consideration due to any seller under the Call Option either in kind
           by means of delivering MATRITECH stock or by making payments in cash.
           MATRITECH stock is to be valued as provided for in 5.2. (i - iii).
           The exchange rate for cash shall be the US dollar spot exchange rate
           published in the Financial Times newspaper of the day the Trigger
           event occurs or of the next business day if such Trigger event does
           not occur on a business day.

<PAGE>   11

Purchase Agreement ADL GmbH                                              Page 11

           If a Seller becomes obligated to sell any MATRITECH Stock to the
           Purchaser under the Call Option and fails to deliver such MATRITECH
           Stock in accordance with the terms of this Purchase Agreement, the
           Purchaser may, at its option, in addition to all other remedies it
           may have, send to the Seller the purchase price for such MATRITECH
           Stock as is herein specified. Thereupon, MATRITECH upon written
           notice to the Seller, (a) shall cancel on its books the certificate
           or certificates representing the MATRITECH Stock to be sold under the
           Call Option and (b) shall issue, in lieu thereof, a new certificate
           or certificates representing such MATRITECH Stock, and thereupon all
           of the Seller's rights in and to such MATRITECH Stock shall
           terminate.

           The obligations of the Sellers to transfer title in shares and/or
           cash to the Purchaser and the obligations of the Purchaser to
           transfer title in shares and/or cash to the Sellers as provided in
           this clause 5.2. shall be due 2 weeks following the receipt of the
           exercise notice by the Sellers.

           In the event of a Call Option being exercised on the MATRITECH Stock
           held by a single Seller, the shareholdings of the remaining two
           Sellers shall be unaffected.

           This Call Option shall expire in its entirety on the first business
           day following the third anniversary of the Effective Date.

5.3.       A Trigger Event for the purpose of this Purchase Agreement shall be
           deemed to occur:

           If a Seller ceases to work for or provide services to ADL be it as an
           employee, managing director, consultant or in any other comparable
           capacity if (1) he leaves of his own accord without the consent of
           the Purchaser before the third anniversary of the Effective Date or
           (2) ADL terminates the contract or otherwise dismisses such Seller
           with good legal reason (wirksame Kundigung) such termination or
           dismissal becoming effective before the third anniversary of the
           Effective Date. For the avoidance of doubt: In case the shareholders
           of the Company resolve to wind up the ADL for other reasons than its
           insolvency, or in case of an insolvency caused by

<PAGE>   12

Purchase Agreement ADL GmbH                                              Page 12

           the withdrawal of loans or other finance instruments by the Purchaser
           before maturity or in violations of a financing agreement, or in case
           that ADL closes down its business (Aufgabe des Geschaftsbetriebs)
           and the Sellers leave ADL because of such events before the third
           anniversary of this Agreement, such events shall not be deemed to
           be a Trigger Event.


                                  ARTICLE IV
                                  ----------

                        REPRESENTATIONS AND WARRANTIES


                     (Zusicherungen und Garantieversprechen)



6          GENERAL


6.1        Each representation and warranty in this Purchase Agreement is a
           separate and independent representation and warranty in relation to
           each of the statements in the representation and warranty and no such
           statement shall be limited by reference to any other such statement
           or by the other terms of this Purchase Agreement.

6.2        Unless expressly stated to the contrary, each representation and
           warranty in this Purchase Agreement shall be deemed given as of the
           Effective Date. The same shall apply to the contents of and listings
           in the Schedules attached hereto.



7          REPRESENTATIONS AND WARRANTIES OF SELLERS WITH RESPECT TO THE SHARES,
           ADL AND THE ADL BUSINESS


7.1        The Sellers, jointly and severally, represent and warrant to
           Purchaser each of the representations (Zusicherung einer Eigenschaft)
           and warran-
<PAGE>   13

Purchase Agreement ADL GmbH                                              Page 13


           ties (selbstandige Garantieversprechen) contained in this Section 7,
           each of which shall constitute an independent liability to the
           Sellers.

7.2        ADL is a limited liability corporation duly organized and validly
           existing under the German GmbH Act. ADL has the requisite corporate
           power and authority to carry on the ADL Business as it is currently
           conducted and is duly qualified or licensed to do the ADL Business,
           in each jurisdiction where the character of its properties owned or
           held under lease or the nature of its activities makes such
           qualification necessary. Complete and correct copies of the
           Certificate of Incorporation (Handelsregisterauszug) and the Articles
           of Incorporation of ADL as in effect on the date hereof are attached
           as SCHEDULE 7.2 hereto.


7.3        The Sellers have the necessary power and authority to execute and
           deliver this Purchase Agreement and to perform the transactions
           contemplated hereby. The execution and delivery hereof and the
           performance of the transactions contemplated hereby by the Sellers
           have been duly authorized and approved by ADL's shareholders, and
           no other corporate or shareholder proceedings on the part of ADL, its
           management board or the shareholders of ADL is necessary to authorize
           or approve this Purchase Agreement or to perform the transactions
           contemplated hereunder. This Purchase Agreement constitutes a valid
           and binding obligation on each Seller, enforceable against each
           Seller in accordance with the terms contained herein.

7.4        The ADL Share Capital consists of DM200,000, all of which is validly
           issued and legally and beneficially held by the Sellers. All the ADL
           Share Capital was issued in accordance with applicable laws, in
           particular the German GmbH Act. There are no options, warrants,
           calls, convertible notes, agreements, commitments or other rights
           (the "STOCK RIGHTS") outstanding or coming into effect after the
           Effective Date that would obligate ADL or any of the Sellers to
           issue, deliver or sell shares of the ADL Share Capital, or to grant,
           extend or enter into any such Stock Right.

<PAGE>   14

Purchase Agreement ADL GmbH                                              Page 14


7.5        Each Seller represents and warrants that all of the Shares are (i)
           validly issued and fully paid up and (ii) free and clear of any lien,
           charge, security interest, pledge, option, right of first refusal,
           voting proxy or other voting agreement, or encumbrance of any kind or
           nature (any of the foregoing, a "LIEN"), as at the Effective Date or
           coming into effect after the Effective Date, and no redemption of
           share capital pursuant to Section 30 of the German GmbH Act of any
           kind whatsoever has occurred from the time of incorporation of ADL to
           the Effective Date, and (iii) that the Purchaser will obtain good and
           marketable title to the Shares and (iv) that the SCHEDULE 7.5
           attached hereto contains a comprehensive and correct description of
           the development of shareholding in ADL GmbH including capital in-/
           decreases and transfer of shares.

7.6        ADL has no subsidiaries and does not otherwise own or control,
           directly or indirectly, any equity interest, or any security
           convertible into an equity interest, in any corporation, partnership,
           limited liability company, joint venture, association or other
           business entity (any of the foregoing, an "ENTITY").

7.7        None of the Sellers or their own family members respectively
           (including a spouse, or lineal descendent of any of the foregoing),
           has any direct or indirect interest or shareholding in any Person (as
           hereinafter defined) or material customer, supplier or competitor of
           ADL, or in any Person from whom or to whom ADL leases any real or
           personal property, or in any other Person with whom ADL is doing
           business whether directly or indirectly (including as a debtor or
           creditor), whether in existence as of the Effective Date or proposed,
           other than the ownership of stock of a company which is listed on a
           recognized stock exchange.

7.8        Neither (i) the execution and delivery of this Purchase Agreement by
           the Sellers, (ii) the consummation by the Sellers of the transaction
           contemplated hereby nor (iii) compliance by the Sellers with any of
           the provisions hereof will

           (a)    conflict with or violate the Articles of Incorporation of ADL;

<PAGE>   15

Purchase Agreement ADL GmbH                                              Page 15


           (b)    result in a violation or breach of, or constitute a default
                  (or an event that, with notice or lapse of time or both, would
                  become a default) under, or give to any other party any right
                  of termination, amendment, acceleration or cancellation of,
                  any contract, agreement, arrangement, lease, license, permit,
                  judgment, decree, franchise or other instrument or obligation,
                  to which ADL is a party or by which ADL or any of its
                  properties or assets may be bound or affected;

           nor, so far as the Sellers are aware after having made all due and
           careful enquiry to ascertain, will

           (c)    result in a violation of any statute, ordinance, rule,
                  regulation, order, judgment or decree applicable to ADL or any
                  of the Sellers, or by which ADL or any of its properties or
                  assets may be bound or affected; nor

           (d)    require any consent, waiver, license, approval, authorization,
                  order, permit, registration or filing with, or notification to
                  (any of the foregoing being a "CONSENT"), (i) any domestic
                  government or subdivision thereof, or any domestic
                  administrative, governmental, or regulatory authority, agency,
                  commission, court, tribunal or body, (any of the foregoing, a
                  "GOVERNMENTAL ENTITY"); or (ii) any other individual or Entity
                  (collectively, a "PERSON").

7.9        Sellers have heretofore furnished the Purchaser with a true and
           complete copy of:

                  The unaudited financial statements of ADL for the years ended
                  1998 and 1999 as well as the unaudited financial statement of
                  ADL Distribution GmbH 1997

           (referred to as the "ADL FINANCIAL STATEMENTS").

           Except as disclosed therein, the ADL as well as the merged ADL
           Distribution GmbH Financial Statements have been prepared in
           accordance with German accounting principles (Grundsatze
           ordnungsgemasser Buchfuhrung und Bilanzierung) consistently
           followed throughout the peri-

<PAGE>   16

Purchase Agreement ADL GmbH                                              Page 16


           ods indicated, and represent fairly, in all material respects, the
           financial position and operating results of ADL and ADL Distribution
           as of the dates specified above. As far as potential liabilities
           (Haftungsverhaltnisse) are not accounted for in the balance sheet,
           the amount is reflected otherwise in the financial statements.

7.10       Since December 31, 1999

           (a)    ADL has not entered into any transaction that was not in the
                  ordinary course of business (gewohnlicher Geschaftsgang);

           (b)    except for sales of goods and services in the ordinary course
                  of business, there has been no sale, assignment, transfer,
                  mortgage, pledge, encumbrance or lease of any material asset
                  or property of ADL;

           (c)    there has been (i) no declaration or payment of a dividend, or
                  any other declaration, payment or distribution of any type or
                  nature to any Seller in respect of his share, whether in cash
                  in DM or in property, and (ii) no purchase or redemption of
                  any share of the share capital of ADL;

           (d)    there has been no declaration, payment, or commitment for the
                  payment by ADL of a bonus or other additional salary,
                  compensation, severance, or benefit to any employee of ADL
                  that was not in the ordinary course of business, except for
                  normal year-end bonuses paid in the ordinary course of
                  business and disclosed in writing to the Purchaser;

           (e)    there has been no release, compromise, waiver or cancellation
                  of any debt to or claim by ADL, or waiver of any right of ADL
                  in excess of 5.000DM in the aggregate;

           (f)    there have been no capital expenditures in excess of 5.000DM
                  for any single item, or 50.000DM in the aggregate;

           (g)    so far as the Sellers are aware after having made all due and
                  careful enquiry to ascertain, there has been no change in
                  accounting meth-

<PAGE>   17

Purchase Agreement ADL GmbH                                              Page 17


                  ods or practices or revaluation of any asset of ADL in excess
                  of 5.000DM for any single asset, or 25.000DM in the aggregate;

           (h)    there has been no material damage, or destruction to, or loss
                  of, physical property (whether or not covered by insurance)
                  adversely affecting the ADL Business or the operations of ADL;

           (i)    there has been no loan by ADL, or guarantee by ADL of any
                  loan, to any employee, manager or officer of ADL or to any
                  other person or Entity;

           (j)    ADL has not ceased to transact business with any customer that
                  represented more than 5% of the annual gross revenues of ADL,
                  nor has ADL received notice from, or become otherwise aware
                  that, any such customer intends to cease transacting business
                  with ADL;

           (k)    there has been no termination of employment or resignation of
                  any key employee or key freelancer, manager or officer of ADL,
                  and, so far as the Sellers are aware after having made all due
                  and careful enquiry to ascertain, no such termination or
                  resignation is likely or threatened;

           (l)    there has been no amendment or termination of any material
                  oral or written contract, agreement or license related to the
                  ADL Business, to which ADL is a party or by which it is bound,
                  except in the ordinary course of business, or except as
                  expressly contemplated hereby;

           (m)    ADL has not failed to satisfy any of its debts, obligations or
                  liabilities related to the ADL Business or the assets of ADL
                  as the same become due and owing (except for ADL Accounts
                  Payable (as defined in Section 7.27 hereof) payable in
                  accordance with past practices and in the ordinary course of
                  business);

           (n)    there has been no agreement or commitment by ADL to do any of
                  the foregoing; and

           (o)    so far as the Sellers are aware after having made all due and
                  careful enquiry to ascertain, there has been no other event or
                  condition of any character pertaining to and materially and
                  adversely affecting (or

<PAGE>   18

Purchase Agreement ADL GmbH                                              Page 18

                  which could be reasonably be expected to materially and
                  adversely affect) the assets, business or financial position
                  of ADL.

7.11       Except as set forth on SCHEDULE 7.11 hereto, ADL has no debt,
           liability or obligation of any kind, whether accrued, absolute or
           otherwise, including, but not limited to, any liability or obligation
           on account of taxes, to the social security system or any
           governmental charge or penalty, interest or fine.
           In addition, Franz Maier agrees to indemnify as of the Effective Date
           the Purchaser and/or ADL as required for any existing or future
           liabilities to MBG or any third party arising out of the loan
           facility for DM 100,000 granted by Mittelstandige
           Beteiligungsgesellschaft Baden-Wurtemberg mbH, Stuttgart (MBG) to ADL
           that took effect from 1 June 1999 (the "MBG Loan"). Such
           indemnification covers re-payments of both capital and interest and
           any other charges levied in connection with the MBG Loan, and shall
           continue to apply if the MBG Loan is terminated or called in at short
           notice for whatever reason.

7.12       Except as provided for in SCHEDULE 7.12, ADL has good and marketable
           title to all tangible property and assets used in the ADL Business,
           and good and valid title to its leasehold interests in such property
           and assets, in each case, free and clear of any and all Liens.

7.13       The Sellers have furnished to the Purchaser in contemplation of the
           entering into of this Purchase Agreement a true, correct and up to
           date list of all items of tangible personal property (including
           technical and computer hardware) necessary for or used in the
           operation of the ADL Business in the manner in which it has been and
           is now operated by ADL (the "ADL EQUIPMENT"), except for personal
           property having a net book value of less than 1.000 DM. Each material
           item of ADL Equipment is in good condition and repair, ordinary wear
           and tear excepted.

7.14       The Sellers have furnished to the Purchaser in contemplation of the
           entering into of this Purchase Agreement a true, complete and up to
           date list of all material proprietary technology, patents, patent
           rights, trademarks,


<PAGE>   19

Purchase Agreement ADL GmbH                                              Page 19


           trademark rights, trade names, trade name rights, service marks,
           service mark rights, and copyrights (and all pending applications for
           any of the foregoing) used by ADL in the conduct of the ADL Business
           together with trade secrets and know how used in the conduct of the
           ADL Business (the "ADL INTELLECTUAL PROPERTY RIGHTS"). ADL owns, or
           is validly licensed or otherwise has the right to use or exploit, as
           currently used or exploited, all of the ADL Intellectual Property
           Rights, free of any obligation to make any payment (whether of a
           royalty, license fee, compensation or otherwise). No claims are
           pending or, so far as the Sellers are aware after having made all
           reasonable enquiry to ascertain, are threatened that ADL is
           infringing or otherwise adversely affecting the intellectual property
           rights of any Person. So far as the Sellers are aware after having
           made all reasonable enquiry to ascertain, no Person is infringing the
           rights of ADL with respect to any ADL Intellectual Property Right.
           Neither the Sellers, nor ADL or so far as the Sellers are aware after
           having made all due and careful enquiry to ascertain, any employee,
           agent or independent contractor of ADL, in connection with the
           performance of such Person's services with ADL, has used,
           appropriated or disclosed, directly or indirectly, any trade secret
           or other proprietary or confidential information of any other Person,
           or otherwise violated any confidential relationship with any other
           Person.

7.15       The Sellers have furnished to the Purchaser in contemplation of the
           entering into of this Purchase Agreement a true, complete and up to
           date list of all material computer software used by ADL in the
           conduct of the ADL Business (the "ADL SOFTWARE"). ADL currently
           licenses, or otherwise has the legal right to use, all of the ADL
           Software (including any upgrade, alteration or enhancement with
           respect thereto), and all of the ADL Software is being used in
           compliance with any applicable license or other agreement.

7.16       SCHEDULE 7.16 hereto sets forth a list of all leases pursuant to
           which ADL leases, as lessor or lessee, real or personal property used
           in operating the ADL Business or otherwise (the "ADL LEASES"). Copies
           of the ADL Leases, all of which have previously been provided to
           Purchaser, are true,

<PAGE>   20

Purchase Agreement ADL GmbH                                              Page 20

           complete and up to date copies thereof. All of the ADL Leases are
           valid, binding and enforceable against ADL and, so far as the Sellers
           are aware after having made all due and careful enquiry to ascertain,
           against the other parties thereto, in accordance with their
           respective terms, and there is not under any such ADL Lease any
           existing default by ADL, or, so far as the Sellers are aware after
           having made all due and careful enquiry to ascertain, by any other
           party thereto, or any condition or event that, with notice or lapse
           of time or both, would constitute a default. ADL has not received
           notice that the lessor of any of the ADL Leases intends to cancel,
           suspend or terminate such ADL Lease or to exercise or not exercise
           any option thereunder.

7.17       The Sellers have been provided with a Due Diligence Request List (the
           "DD-List", SCHEDULE 7.17.1), dated June 2/3, 2000 and have thereupon
           declared that the issues crossed out in this List are not applicable
           as to the business and or the shares of ADL. The handwritten remarks
           have been made on behalf of the Sellers. They have provided
           subsequently all the documents listed in the Due Diligence Documents
           Received List ("DDDR-List", SCHEDULE 7.17.2). True and complete
           copies of all material ADL Contracts (or a true and complete
           narrative description of any oral ADL Contract) have previously been
           provided to the Purchaser. Any Distributorship or Agency Agreement
           entered into by or on behalf of ADL which is still in force shall be
           deemed a material ADL Contract. Neither ADL nor, so far as the
           Sellers currently are aware, any other party to any of the ADL
           Contracts are in default under (nor does there exist any condition
           that, with notice or lapse of time or both, would cause such a
           default under) any of the ADL Contracts. Neither ADL nor, so far as
           the Sellers currently are aware after having made all reasonable
           enquiry to ascertain, any other party to any of the ADL Contracts
           have waived any right they may have under any of the ADL Contracts,
           the waiver of which would have a material adverse effect on the
           business, assets or financial condition or prospects of ADL. All of
           the ADL Contracts constitute valid and binding obligations of ADL,
           enforceable in accordance with their respective terms, and,

<PAGE>   21

Purchase Agreement ADL GmbH                                              Page 21

           so far as the Sellers currently are aware after having made all
           reasonable enquiry to ascertain, of the other parties thereto.

7.18       SCHEDULE 7.18 hereto sets forth a list of the name of each manager
           and officer of ADL and the position(s) held by each.

7.19       The Sellers have previously provided the Purchaser with a true and
           complete copy of the payroll report of ADL dated May 24, 2000,
           showing all employees of ADL and their levels of compensation as at
           such date, other than bonuses and other extraordinary payments, all
           of such bonuses and extraordinary payments are set forth in SCHEDULE
           7.19.1 hereto. ADL has paid all compensation required to be paid to
           employees of ADL on or prior to the Effective Date other than
           compensation accrued in the current pay period as specified in
           SCHEDULE 7.19.2 hereto.

7.20       There is no suit, action, claim, investigation or proceeding, pending
           or, so far as the Sellers are aware after having made all due and
           careful enquiry to ascertain, threatened against or affecting ADL or
           the ADL Business, nor is there any judgment, decree, injunction or
           order of any applicable domestic Governmental Entity or arbitrator
           outstanding against ADL.

7.21       Except as disclosed in SCHEDULE 7.21 hereto, there are no employee
           benefit plans, agreements or arrangements maintained by ADL,
           including (i) pension schemes (Pensionszusagen); (ii) current or
           deferred compensation, pension, profit sharing, vacation or severance
           plans or programs; or (iii) medical, hospital, accident, disability
           or death benefit plans (collectively, "ADL BENEFIT PLANS"). All ADL
           Benefit Plans are administered in accordance with, and are in
           material compliance with, all applicable laws and regulations. No
           default exists with respect to the obligations of ADL under any ADL
           Benefit Plan.

7.22       There are no labor disputes, grievances, controversies, strikes or
           requests for union representation pending, or, so far as the Sellers
           are currently aware, threatened, relating to or affecting the ADL
           Business. So far as the Sellers are aware after having made all due
           and careful enquiry to ascer-
<PAGE>   22

Purchase Agreement ADL GmbH                                              Page 22


           tain, no event has occurred that could give rise to any such dispute,
           controversy, strike or request for representation.

7.23       ADL has duly and timely filed all federal, state and local income,
           wage, franchise, excise, real and personal property and other tax and
           social security returns and reports, including extensions, required
           to have been filed by ADL on or prior to the Effective Date. ADL has
           duly and timely paid all taxes and other governmental or social
           security charges, and all interest and penalties with respect
           thereto, required to be paid by ADL on or prior to the Effective Date
           (whether by way of withholding or otherwise) to any federal, state,
           local or other taxing or social security authority (except to the
           extent the same are being contested in good faith, and adequate
           reserves therefor have been provided in the ADL Financial
           Statements). The Sellers warrant and represent that the company has
           not paid any amounts that could be regarded as hidden profit
           distribution. Further, the sellers warrant and represent a total loss
           carry forward for corporation tax purposes available to ADL GmbH for
           the year 2000 onwards in the amount of DM 655.000 and for trade tax
           purposes in the amount of DM 200.000,-- until December 31, 1998. ADL
           was duly and timely eligible to any and all VAT-input tax (Vorsteuer
           nach ss. 15 Umsatzsteuergesetz) whether resulting in a VAT-refund or
           in a reduction of ADL's VAT liability filed in preliminary or
           annual VAT-returns of ADL on or prior to the Effective Date. As of
           the Effective Date, all deficiencies proposed as a result of any
           audit have been paid or settled.

7.24       ADL holds all material permits, licenses, variances, exemptions,
           orders and approvals of all domestic Governmental Entities necessary
           to own, lease or operate all of the assets and properties of ADL, as
           appropriate, and to carry on the ADL Business as now conducted (the
           "ADL PERMITS"). ADL in all material respects complies with all
           applicable laws, ordinances and regulations and the terms of the ADL
           Permits. SCHEDULE 7.24 hereto sets forth a true, complete and up to
           date list of all ADL Permits, true and complete copies of which have
           previously been provided by the Sellers to the Purchaser, and unless
           otherwise indicated, none of the ADL Permits

<PAGE>   23

Purchase Agreement ADL GmbH                                              Page 23

           are affected by the entering into of this Purchase Agreement and the
           performance of the transactions contemplated hereunder.

7.25       No broker or finder is entitled to any broker's or finder's fee or
           other  commission  payable by ADL in connection  with the
           transactions contemplated hereunder.

7.26       All accounts, notes, contracts and other receivables of ADL
           (collectively, "ADL ACCOUNTS RECEIVABLE") (alle Vermogensgegenstande
           des Umlaufvermogens gemass ss. 266 Abs. 2 B. II, III. 3. und IV.
           HGB von ADL) were acquired by ADL in the ordinary course of business
           arising from bona fide transactions. So far as the Sellers are
           currently aware, there are no set-offs, counterclaims or disputes
           asserted with respect to any ADL Accounts Receivable that would
           result in claims in excess of the reserve for bad debts set forth on
           the ADL Financial Statements and, subject to such reserve, and so far
           as the Sellers are aware after having made internal enquiry to
           ascertain, all ADL Accounts Receivable are collectible in full.

7.27       All material accounts, notes, contracts and other amounts payable of
           ADL (collectively, "ADL ACCOUNTS PAYABLE") (alle Verbindlichkeiten
           gemass ss. 266 Abs. 3 C. HGB von ADL) are currently within their
           respective terms, and are neither in default nor otherwise overdue by
           more than 90 days with exception of issues listed in SCHEDULE 7.27..
           The Sellers have previously provided the Purchaser with a true and
           complete aged debtor report prepared as of 30 June 1998 which shows
           the time elapsed since the invoice date for all ADL Accounts Payable
           as at that date.

7.28       The insurance policies of ADL, in full force and effect, (the "ADL
           INSURANCE  POLICIES") are listed on SCHEDULE 7.28  hereto and ADL

           (a)    is not in default regarding the provisions of any ADL
                  Insurance Policy;

           (b)    has paid all premiums due thereunder; and

           (c)    has not failed to present any notice or material claim
                  thereunder in a due and timely fashion.

<PAGE>   24

Purchase Agreement ADL GmbH                                              Page 24


7.29       ADL has not filed a petition or request for reorganization or
           protection or relief under the bankruptcy laws of the Federal
           Republic of Germany, made any general assignment for the benefit of
           creditors, or consented to the appointment of a receiver or trustee,
           whether such receiver or trustee is appointed in a voluntary or
           involuntary proceeding.

7.30       As of the Effective Date, the ADL Debt is not in excess of DM635,000.

7.31       For the period commencing on 31 December 1999 and ending on the
           Effective Date ADL has not directly or indirectly incurred any debt
           or made any guarantee outside its ordinary course of business
           exceeding the amount of 5.000 DM in aggregate.

7.32       No statement of fact by any Seller contained herein and no written
           statement of fact furnished by ADL or any Seller to Purchaser in
           connection herewith contains any untrue statement of a material fact
           or omits to state a material fact necessary in order to make the
           statements herein or therein contained not materially misleading.

7.33       As of 31.12.1999, the Equity Deficit (der durch Eigenkapital nicht
           gedeckte Fehlbetrag) was DM 257. 056, 94. The Adjusted Equity Deficit
           as of Effective Date (as defined in Schedule 7.33) is not greater
           than DM110,000.

7.33.1     As of the Effective Date, there are no environmental hazards
           (Altlasten), contaminations of any kind, or other hazards as
           addressed in BBodSchG (jegliche relevante Beeintrachtigungen im
           Sinne des Bundesbodenschutzgesetzes) of or on the premises of ADL.



8          REPRESENTATIONS AND WARRANTIES OF PURCHASER WITH RESPECT TO THE
           ACQUISITION CONSIDERATION

8.1        The Purchaser represents and warrants, to each of the Sellers
           individually, the following representations and warranties contained
           in this Section 8.

8.2        The Purchaser is a corporation duly organized, validly existing and
           in good standing under the laws of the State of Delaware, USA. The
           Purchaser

<PAGE>   25

Purchase Agreement ADL GmbH                                              Page 25


           has the requisite corporate power and authority to carry on its
           business as it is currently conducted and is duly qualified or
           licensed to do business, and is in good standing, in each
           jurisdiction where the character of its properties owned or held
           under lease or the nature of its activities makes such qualification
           necessary, except where the failure to be so qualified or licensed
           would not have a material adverse effect on the Company.

8.3        The Purchaser has the necessary corporate power and authority to
           execute and deliver this Purchase Agreement and to perform the
           transactions contemplated hereby. The execution and delivery hereof
           and the performance of the transactions contemplated hereby by
           Purchaser have been duly and validly authorized and approved by its
           board of directors, and no other corporate or shareholder proceedings
           on the part of the Purchaser, or its board of directors or
           shareholders, are necessary to authorize or approve this Purchase
           Agreement or to perform the transactions contemplated hereby. This
           Purchase Agreement constitutes a valid and binding obligation on the
           Purchaser, enforceable against the Purchaser in accordance with its
           terms, subject, in each case, to bankruptcy, insolvency,
           reorganization, moratorium and similar laws of general application
           relating to or affecting creditors' rights and to general principles
           of equity, including principles of commercial reasonableness, good
           faith and fair dealing.

8.4        The execution and delivery of this Purchase Agreement by the
           Purchaser, the performance by the Purchaser of the transactions
           contemplated hereby, or compliance by the Purchaser with any of the
           provisions hereof, will not in any material sense:

           (a)    conflict with or violate the Certificate of Incorporation or
                  Bylaws of the Purchaser;

           (b)    result in a violation of any statute, ordinance, rule,
                  regulation, order, judgment or decree applicable to the
                  Purchaser, or by which the Purchaser or its properties or
                  assets may be bound or affected;

           (c)    result in a violation or breach of, or constitute a default
                  (or an event that, with notice or lapse of time or both, would
                  become a default)

<PAGE>   26

Purchase Agreement ADL GmbH                                              Page 26

                  under, or give to others any rights of termination, amendment,
                  acceleration or cancellation of, any note, bond, mortgage,
                  indenture, or any material contract, agreement, arrangement,
                  lease, license, permit, judgment, decree, franchise or other
                  instrument or obligation to which the Purchaser is a party or
                  by which the Purchaser or its properties may be bound or
                  affected;

           (d)    result in the creation of any Lien on any of the property or
                  assets of the Purchaser.



8.5        As of the date hereof, the authorized capital stock of Purchaser
           consists of 40,000,000 shares of Common Stock, $01 par value, of
           which 24,908,635 shares were issued and outstanding as of 31 March
           2000, and 4,000,000 shares of Preferred Stock, $1.00 par value, of
           which no shares are issued and outstanding.

8.6        When delivered to the Sellers in accordance with the terms hereof,
           the MATRITECH Stock will be (i) duly authorized, fully paid and
           non-registered and (ii) free and clear of all Liens other than
           restrictions imposed by this Purchase Agreement and by US federal and
           state securities laws.

8.7        Purchaser has not filed a petition or request for reorganization or
           protection or relief under the bankruptcy laws of the United States
           or any state or territory thereof, made any general assignment for
           the benefit of creditors, or consented to the appointment of a
           receiver or trustee, including a custodian under the United States
           bankruptcy laws, whether such receiver or trustee is appointed in a
           voluntary or involuntary proceeding.

8.8        The Purchaser warrants that it will, not later than the first
           business day following the first anniversary of the Effective Date,
           do all such things necessary to permit the Sellers to sell on the
           NASDAQ Stock Market or otherwise transfer the shares of MATRITECH
           Stock received under this Purchase Agreement, if and when such shares
           cease to be subject to any Call Option, in particular by doing away
           with any stop orders with

<PAGE>   27

Purchase Agreement ADL GmbH                                              Page 27


           MATRITECH's transfer agent and, if such shares are not eligible for
           resale on the NASDAQ Stock Market under Rule 144, Regulation S or
           other applicable exemption under the U.S. Securities Act of 1933 (the
           "SECURITIES ACT"), by registering such shares for resale under the
           Securities Act.



9          REPRESENTATIONS AND WARRANTIES OF SELLERS WITH RESPECT TO THE
           ACQUISITION CONSIDERATION


9.1        Each Seller represents that he

           (a)    is a German national and not a "U.S. person" as such term is
                  defined in Section 7701(a)(30) of the U.S. Internal Revenue
                  Code of 1986 or in the rules under the Securities Act, nor is
                  the Seller located in the United States and or acquiring the
                  shares of MATRITECH Stock for the account or benefit of a U.S.
                  person; the Seller has not offered, sold, or entered into any
                  transaction (e.g., the purchase of any put or sale of any
                  call) involving the sale or potential sale of any of the
                  shares in the United States or to U.S. persons;

           (b)    has been offered and is acquiring the MATRITECH Stock outside
                  the United States and solely for his own account and benefit
                  for investment and not with a view to, or for sale in
                  connection with, any distribution thereof; and

           (c)    will not, directly or indirectly, offer, transfer, sell,
                  pledge, hypothecate or otherwise dispose of any MATRITECH
                  Stock (or solicit any offers to buy, purchase or otherwise
                  acquire or take a pledge of any such shares) in the United
                  States or to or for the benefit or account of any U.S. person,
                  or otherwise, or conduct any hedging transaction involving
                  MATRITECH Stock, except in compliance with the Securities Act
                  and Regulation S or the other rules and regulations
                  thereunder, and other applicable laws, rules and regulations.

                  It is understood and agreed by the parties hereto that
                  MATRITECH is required to refuse to register any transfer of
                  MATRITECH Stock not made in accordance with the provisions of
                  said Regulation S, or pur-

<PAGE>   28

Purchase Agreement ADL GmbH                                              Page 28


                  suant to registration under the Securities Act or to an
                  exemption therefrom.

9.2        Each Seller acknowledges that

           (a)    the MATRITECH Stock received by him hereunder has not been
                  registered under the Securities Act;

           (b)    the MATRITECH Stock may be required to be held for a period of
                  up to three years, and he must continue to bear the economic
                  risk of the investment in such shares unless such shares are
                  subsequently registered under the Securities Act or Regulation
                  S or another exemption from such registration is available;

            (c)   restrictive legends shall be placed on the certificates
                  representing MATRITECH Stock; and

           (d)    a notation shall be made in the appropriate records of the
                  Purchaser's transfer agent indicating that the shares of
                  MATRITECH Stock issued under this Purchase Agreement are
                  subject to restrictions on transfer and appropriate
                  stop-transfer instructions will be issued to such transfer
                  agent with respect to such shares of MATRITECH Stock.

9.3        Each Seller represents and warrants that

           (a)    his financial situation is such that he can afford to bear the
                  economic risk of holding the MATRITECH Stock acquired by him
                  hereunder for an indefinite period;

           (b)    he can afford to suffer the complete loss of such MATRITECH
                  Stock; and

           (c)    he has been granted the opportunity to ask questions of, and
                  receive answers from, representatives of the Purchaser
                  concerning the terms and conditions of the issuance of
                  MATRITECH Stock hereunder and to obtain any additional
                  information that he deems necessary;

<PAGE>   29

Purchase Agreement ADL GmbH                                              Page 29


           (d)    his knowledge and experience in financial business matters is
                  such that he is capable of evaluating the merits and risk of
                  ownership of the MATRITECH Stock.


                                    ARTICLE V

                                 INDEMNIFICATION

10         INDEMNIFICATION BY THE SELLERS, PAYMENT

10.1       The Sellers, jointly and severally, shall indemnify and hold the
           Purchaser and/or, at the discretion of Purchaser, ADL harmless from
           and against, and agree to defend promptly the Purchaser and/or, at
           the discretion of Purchaser, ADL from and reimburse the Purchaser
           and/or, at the discretion of Purchaser, ADL, for, any and all losses,
           damages, costs, expenses, liabilities, obligations and claims of any
           kind (including reasonable attorneys' fees according to domestic
           standards and other legal costs and expenses) that the Purchaser
           and/or ADL may at any time suffer or incur, or become subject to
           (collectively, the "PURCHASER LOSS") [Schadensersatz gemass
           ss.ss. 249 ff BGB], as a result of or in connection with:

           (a)    any breach or any inaccuracy of any of the representations and
                  warranties [sollte ein garantierter oder zugesicherter Umstand
                  nicht, nicht im angegebenen Umfang oder zu dem vorausgesetzten
                  Zeitpunkt vorliegen] made by the Sellers in or pursuant
                  hereto, or in any instrument, certificate or affidavit
                  delivered by any of the same in accordance with the provisions
                  hereof;

           (b)    any failure by the Sellers to carry out, perform, satisfy and
                  discharge any of their respective covenants, agreements,
                  undertakings, liabili-


<PAGE>   30

Purchase Agreement ADL GmbH                                              Page 30


                  ties or obligations hereunder or under any of the documents
                  and materials delivered by the Sellers pursuant hereto; and
                  (c) any suit, action or other proceeding arising out of, or in
                  any way related to, any of the matters referred to in this
                  Section 10.

           (d)    and unknown or contingent liability which becomes known after
                  the Effective Date but which arose prior to the Effective
                  Date.

10.2.    Without prejudice to the foregoing, in the event of any violation of
         the any representations and warranties relating tax, social security
         payment or other mandatory contributions the sellers will indemnify the
         Purchaser and/or at the discretion of the Purchaser ADL for the full
         amount required to put the Purchaser and/or ADL in the position in
         which they would have been had the violation not occurred i.e. to put
         them - as the Purchasers may choose - in a position as if any
         additional taxes or social security contributions arising in the future
         had been properly reflected in the balance sheet as of December 31,
         1999 or to put them in a position as if the loss carry forward
         warranted had existed as warranted or as if payments which are regarded
         a constructive dividend had not been paid or made in accordance with
         the applicable law. Interest assessed on such taxes and social security
         contributions must be paid by the seller. Any claim arising from or in
         connection with the tax indemnification clauses hereof shall expire 6
         months after a final and binding assessment notice issued by the tax-
         or social security authorities, following upon a final tax- and social
         security audit.

10.3.    Any Purchaser Loss as defined in 10.1. or 10.2. shall be indemnified
         with respect to the amount due in cash in DM or, at the sole discretion
         of the indemnified party, in MATRITECH Stock as valued at the close of
         trading at the NASDAQ stock exchange and in accordance with the US
         dollar spot exchange rate published in the Financial Times newspaper of
         the day on the last business day prior to the date such payment is to
         be made. The aggregate of any such indemnification payable is capped at
         a figure of DM1,075,000,--. The Sellers shall not be liable for
         indemnification payments under Section 10.1 and 10.2. unless the
         aggregate amount of Purchaser Loss (determined without regard to any
         materiality qualification contained in


<PAGE>   31

Purchase Agreement ADL GmbH                                              Page 31

         any representations, warranties or covenants giving rise to the claim
         for indemnity) exceeds DM 5,000,-- and then to the full extent of such
         Purchaser Loss. The warranty and indemnification relating to loss carry
         forward and constructive dividends shall not be subject to this
         provision. Instead, as regards the warranty of a loss carry forward of
         DM 655,000,-- in clause 7.24 and as regards the warranty that there
         have been no constructive dividends (verdeckte Gewinnausschuttungen)
         the Sellers shall not be liable for indemnification payments under
         Section 10.1 and 10.2. unless the aggregate amount of Purchaser Loss
         p.a. for this warranty exceeds DM 10,000,-- and then to the full extent
         of such Purchaser Loss.

10.4.    To the extend not provided otherwise in clause 10.2. all claims arising
         under the warranties and  representations  except such warranties and
         representations provided for in 7.5. shall expire 5 years from the
         Effective Date.

11       NOTIFICATION OF CLAIMS; ELECTION TO DEFEND

11.1     A party entitled to be indemnified pursuant to Section 10 hereof,
         (the "INDEMNIFIED PARTY"), shall notify the party liable for such
         indemnification (the "INDEMNIFYING PARTY") in writing of any claim or
         demand (a "CLAIM") that the Indemnified Party has determined, has
         given or could give rise to a right of indemnification hereunder.
         Subject to the Indemnifying Party's right to defend in good faith
         third party claims as hereinafter provided, the Indemnifying Party
         shall satisfy its obligations under this Article V within 30 days
         after the receipt of written notice thereof from the Indemnified
         Party. Any amounts paid thereafter shall include interest thereon for
         the period commencing at the end of such 30-day period and ending on
         the actual date of payment, at a rate of 10% per annum.

11.2     If the Indemnified Party shall notify the Indemnifying Party of any
         Claim pursuant to Section 12.1 hereof, and if such Claim relates to a
         Claim asserted by a third party against the Indemnified Party that
         the Indemnifying Party acknowledges is a Claim for which it must
         indemnify or hold harmless the In-

<PAGE>   32

Purchase Agreement ADL GmbH                                              Page 32



         demnified Party under Section 10 or 11 hereof, as the case may be, the
         Indemnifying Party shall have the right, at its sole cost and expense,
         to employ counsel of its own choosing to defend any such Claim asserted
         against the Indemnified Party.

                                  ARTICLE IIII
                              ADDITIONAL AGREEMENTS

12       NOTIFICATION OF TRANSFER OF SHARES

12.1     The notary  public is hereby  instructed  by the parties to notify
         the sale and  purchase  of the Shares to ADL  pursuant to Section 16
         of the German GmbH Act.

12.2     Prior to the above notification, the Sellers shall not, directly or
         indirectly, adopt any shareholder resolutions in ADL or make any such
         resolutions, actions or the like, in particular but not limited to
         shall they not:

         (a)      resolve on the payment of, or pay, any dividend on, or make
                  any other distribution in respect of, any of the Shares, or
                  split, combine, redeem or reclassify any of the Shares, or
                  issue or authorize the issuance of any other securities in
                  respect of, in lieu of or in substitution for, the Shares;

         (b)      issue, deliver, sell, pledge or otherwise encumber any of the
                  Shares, any other voting security issued by ADL or any
                  security convertible into, or any right, warrant or option to
                  acquire any such share or voting security;

         (c)      amend the Articles of Incorporation of ADL or any other
                  comparable organizational document;

         (d)      subject to a Lien or sell, lease or otherwise dispose of any
                  of its properties or assets;

         (e)      incur any indebtedness for borrowed money or guarantee any
                  such indebtedness of another Person or issue or sell any debt
                  security of

<PAGE>   33

Purchase Agreement ADL GmbH                                              Page 33


                  ADL or guarantee any debt security of another Person, make any
                  loan, advance or capital contribution to, or investment in,
                  any other Person, or settle or compromise any material claim
                  or litigation; or

         (f)      authorize any of, or commit or agree to take any of, the
                  foregoing actions.

13       SUPPLEMENTARY CONTRACTS, ANCILLARY DOCUMENTATION

13.1     Following the consummation of this Purchase Agreement each Seller
         hereby agrees to enter into a service or employment, as the case may
         be, contract with ADL for a minimum term of three years from the
         Effective Date [according to the terms set out in the master
         employment contract attached in SCHEDULE 13.1 hereto].

14       CONSENT

14.1     The Board of Directors of Purchaser has approved this Purchase
         Agreement, upon the terms and subject to the conditions set forth
         herein.

14.2     The Sellers, hereby acting in their capacity of being the sole
         shareholders in ADL, hold a shareholder meeting, waive all
         requirements of form and notice and adopt a shareholder resolution
         and unanimously declare their respective consent to this Purchase
         Agreement, as required by law and by ADL's Articles of
         Incorporation.

14.3     The Sellers hereby waive all and any preemption rights or other
         rights which they have in respect of the Shares and in accordance
         with Section 16 of ADL's Articles of Incorporation.

15       NOTICES

15.1     All notices or other communications under this Purchase Agreement
         shall be in writing and shall be given (and shall be deemed to have
         been duly given


<PAGE>   34

Purchase Agreement ADL GmbH                                              Page 34


         upon receipt) by delivery in person, by telecopy (with confirmation of
         receipt), by courier service, or by registered or certified mail,
         postage prepaid, return receipt requested, at the address specified on
         the first and second page of this notarial deed or to such other
         address as any party may have furnished to the other parties in writing
         in accordance with this Section.

16       GOVERNING LAW, LANGUAGE, PLACE OF JURISDICTION

16.1     This Purchase Agreement and all documents supplemental thereto are
         governed in all respects by and are to be construed in accordance with
         the laws of the Federal Republic of Germany, except for the provisions
         in this Purchase Agreement covering the Consideration (other than
         Purchaser's warranties and representations in this regard), which shall
         be governed in all respects by and are to be construed in accordance
         with the internal laws of the State of Delaware, USA.

16.2     The English language text of this Purchase Agreement is definitive,
         provided, however, that German wording or a legal term which is
         incorporated in parentheses in the terms of this Purchase Agreement
         shall be for the avoidance of doubt regarded as a definition of any
         English language or term to which the German wording or legal term is
         adhered to and such German wording or legal term shall prevail the
         English language or term in order to determine the applicable German
         legal principles and rules.

16.3     The place of jurisdiction shall be Freiburg, Germany.

17       ANNOUNCEMENTS

17.1     The parties agree that, except as may otherwise be required to comply
         with applicable laws and regulations (including applicable securities
         laws) or to obtain consents required hereunder, public disclosure of
         the transactions contemplated hereby or any announcement to a third
         party shall be made only upon or after the consummation of this
         Purchase Agreement.

<PAGE>   35

Purchase Agreement ADL GmbH                                              Page 35

         Any such disclosure or announcement shall be coordinated by Purchaser,
         and none of the Sellers or ADL shall make any such disclosure or
         announcement without the prior written consent of Purchaser.

18       FEES AND EXPENSES

18.1     Each of the Parties is to be solely responsible for the payment of all
         of its costs and fees incurred in the negotiation and completion of
         this purchase agreement and in all matters arising from it. Any
         notarial fees payable will be split equally between the Purchaser and
         the Sellers.

19       LOAN AGREEMENT

19.1     By an agreement (the "LOAN AGREEMENT") made 30 June 1998 Franz Maier
         (the "VENDOR") as majority shareholder and sole managing director of
         ADL consolidated previous loans made by him and third parties to ADL
         and debts to ADL acquired by him with a further loan. At 1 July 1998
         ADL's indebtedness to Franz Maier was DEM 178,589.72. A list with the
         history of the Loan Agreement is attached hereto as Schedule 19.1. The
         Loan is subordinated in accordance with the subordination agreement
         dated 23 March 2000 (Schedule 19.2.).

19.2.    The Vendor herewith assigns to the Purchaser (and the Purchaser accepts
         such assignment) the Loan Agreement, in particular the rights, title
         and interest in all monies payable under the Loan Agreement and any
         previous loan agreements and all interest and other money (if any) now
         due and subsequently to become due in respect thereof (the "DEBTS")
         absolutely free and clear of any rights of third parties, all
         mortgages, charges, pledges, liens, trusts, claims and other interests.
         In addition, the Vendor assigns the Subordination Agreement dated 23
         March 2000 (Schedule 19.2) to the Purchaser since it forms part of the
         terms and conditions of the loan. The Vendor warrants that the loan
         assigned is absolutely free and clear of any rights of third parties,
         all mortgages, charges, pledges, liens, trusts, claims and other
         interests.


<PAGE>   36

Purchase Agreement ADL GmbH                                              Page 36


19.3.    In consideration for the assignment the Purchaser shall pay to the
         Vendor DEM200.000 but not in cash but in MATRITECH Stock valued at the
         Market Price determined in accordance with Section 5.1. To effect such
         payment the Purchaser shall procure the issue to the Vendor of that
         number of shares of non-registered MATRITECH Stock valued at the Market
         Price at DEM200.000 (the "LOAN CONSIDERATION").

19.4     If the Purchaser exercises its Call Option, as provided for in Sections
         5.2. and 5.3. hereof, with respect to the shares held by the Vendor,
         such Call Option shall also apply to the Loan Consideration.

19.5     The Vendor, in his capacity as sole Managing Director of ADL herewith
         gives the consent of ADL to such assignment.

20       ENTIRE AGREEMENT

         This Purchase Agreement and the documents, Schedules and instruments
         referred to herein and to be delivered pursuant hereto constitute the
         entire agreement between the parties pertaining to the subject matter
         hereof, and supersede all other prior agreements and understandings,
         both written and oral, among the parties, or any of them, with respect
         to the subject matter hereof. There are no other representations or
         warranties, whether written or oral, between the parties in connection
         the subject matter hereof, except as expressly set forth herein.

21       SEVERABILITY

21.1     If any term or other provision hereof is invalid, illegal or incapable
         of being enforced by any rule of law or public policy, all other
         conditions and provisions hereof shall nevertheless remain in full
         force and effect so long as the economics or legal substance of the
         transactions contemplated hereby are not affected in any manner
         materially adverse to any party. Upon determination that any term or
         other provision hereof is invalid, illegal or incapable of

<PAGE>   37

Purchase Agreement ADL GmbH                                              Page 37


         being enforced, the invalid, illegal or incapable term or other
         provision is substituted by such valid, legal or capable term or other
         provision so as to effect the original intent of the parties as closely
         as possible to the fullest extent permitted by applicable law in an
         acceptable manner to the end that the transactions contemplated hereby
         are fulfilled to the extent possible.

21.2     The provisions in Section 21.1 shall apply accordingly should this
         Purchase Agreement contain any lacuna. In order to fill the lacuna any
         such legal or capable term or other provision shall apply that comes
         nearest to what the parties have agreed upon or would have agreed upon
         had they considered this fact.

THIS NOTARIAL DEED together with the Schedules attached hereto was read out by
the notary public to the persons present, the contents of which was approved by
them, and then signed by them and the notary public, each in his own hand.





/s/ Petra Urban                             /s/ Stephan Schmidt
-------------------------------             ------------------------------------
    Petra Urban                                 Stephan Schmidt



                                            /s/ Dr. Heinz L. Bauer
                                            ------------------------------------
                                                Dr. Heinz L. Bauer
                                                notary public