<PAGE>
                                                                   Exhibit 10.36

                       VENTURE LOAN AND SECURITY AGREEMENT

                                                  Dated as of September 27, 2001

                                  by and among

                               GATX VENTURES, INC.
                                       and
                       VENTURE LENDING & LEASING III, INC.

                                   as Lenders

                                       and
                                 ACUSPHERE, INC.
                             a Delaware corporation
                                38 Sidney Street
                         Cambridge, Massachusetts 02139
                                   as Borrower

                                       and
                        ACUSPHERE SECURITIES CORPORATION
                           a Massachusetts corporation
                                38 Sidney Street
                         Cambridge, Massachusetts 02139
                                  as Guarantor

                            CREDIT AMOUNT: $5,000,000
<TABLE>
<CAPTION>
                                                          Commitment Amounts:                   Commitment Percentage:
                                                          ------------------                    ---------------------
             <S>                                          <C>                                   <C>
                            GATX Ventures, Inc.:               $2,500,000                                50%
             Venture Lending & Leasing III, Inc.               $2,500,000                                50%
</TABLE>

<TABLE>
<CAPTION>
                  <S>                                                  <C>
                  Repayment Period:                                    30 months

                  Loan Rate:                                           15%

                  Commitment Termination Date:                         September 30, 2001
</TABLE>

         The defined terms and information set forth on this cover page are a
part of the Venture Loan and Security Agreement, dated as of the date first
written above (this "Agreement"), entered into by and among GATX VENTURES, INC.,
and VENTURE LENDING & LEASING III, INC. (each individually a "Lender" and
collectively, "Lenders"), and the borrower ("Borrower") set forth above. The
terms and conditions of this Agreement agreed to between Lenders and Borrower
are as follows:
<PAGE>
                                   ARTICLE I
                                 INTERPRETATION

         1.01. Certain Definitions. Unless otherwise indicated in this Agreement
or any other Operative Document, the following terms, when used in this
Agreement or any other Operative Document, shall have the following respective
meanings:

         "Affiliate" means any Person that owns or controls directly or
indirectly ten percent or more of the stock of another entity, any Person that
controls or is controlled by or is under common control with such Persons or any
Affiliate of such Persons or each of such Person's officers, directors, joint
venturers or partners.

         "Agreement" shall mean this Venture Loan and Security Agreement, as the
same may from time to time be amended or supplemented.

         "Borrower" shall have the meaning set forth on the cover page hereof.

         "Business Day" means any day that is not a Saturday, Sunday, or other
day on which banking institutions are authorized or required to close in
California or Massachusetts.

         "Claim" has the meaning given to that term in Section 10.03.

         "Code" means the Uniform Commercial Code as adopted and in effect in
the State of California, as amended from time to time.

         "Collateral" has the meaning given to that term in Section 5.01.

         "Comdisco Indebtedness" shall mean the Indebtedness of Borrower to
Comdisco, Inc. pursuant to a certain Subordinated Loan and Security Agreement,
dated as of October 16, 1998, as amended by Amendment Number One to Subordinated
Loan and Security Agreement, dated as of August 9, 1999.

         "Commitment" means, with respect to each Lender, the amount set forth
on the cover page of this Agreement under the column titled "Commitment Amount"
and "Commitments" means all such amounts collectively.

         "Commitment Percentage" means with respect to each Lender, the
percentage set forth on the cover page of this Agreement under the column titled
"Commitment Percentage."

         "Commitment Termination Date" shall mean the date specified on the
cover page of this Agreement.

         "Credit Amount" shall mean the maximum aggregate amount of the Loans
under this Agreement (if the conditions specified in Schedule 3 are satisfied),
which amount is set forth following such term on the cover page of this
Agreement.

                                      -2-
<PAGE>
         "Default" shall mean any event which with the passing of time or the
giving of notice or both would become an Event of Default hereunder.

         "Default Rate" means the per annum rate of interest equal to 5% over
the Loan Rate, but such rate shall in no event be more than the highest rate
permitted by applicable law to be charged on commercial loans.

         "Disclosure Schedule" shall mean Schedule 2 of this Agreement.

         "Elan Indebtedness" shall mean any and all Indebtedness now existing or
hereafter incurred pursuant to that certain 6% Convertible Subordinated
Promissory Note due June 30, 2006 in the aggregate principal amount of
$8,010,000 originally issued to Elan International Services Ltd, as amended and
in effect from time to time.

         "Elan Joint Venture" shall mean Acusphere Newco Ltd., an exempted
liability company incorporated under the laws of Bermuda, including any
successor or assign.

         "Elan Joint Venture Agreements" shall mean and include (i) the
Securities Purchase Agreement by and between Borrower and Elan International
Services Ltd. ("Elan") dated as of June 30, 2001 (the "Elan Securities
Agreement"), (ii) the 6% Convertible Subordinated Promissory Note due June 30,
2006 in the aggregate principal amount of $8,010,000 (the "Elan Note"), (iii)
the Exchange Agreement by and between Borrower and Elan dated as of June 30,
2001, (iv) the Subscription, Joint Development and Operating Agreement by and
among Elan, Elan Corporation, plc, Elan Pharma International Limited, Borrower
and Acusphere Newco Ltd. dated as of June 30, 2001 (the "JDOA"), (v) the License
Agreement by and between Borrower and Acusphere Newco Ltd. dated as of June 30,
2001, and (vi) any amendments, extensions, renewals or extensions to any of the
foregoing, other than amendments, extensions, renewals or extensions which could
reasonably be expected to have a Material Adverse Effect.

         "Environmental Claims" means all claims, however asserted, by any
Governmental Authority or other Person alleging potential liability or
responsibility for violation of any Environmental Law or for release or injury
to the environment or threat to public health, personal injury (including
sickness, disease or death), property damage, natural resources damage, or
otherwise alleging liability or responsibility for damages (punitive or
otherwise), cleanup, removal, remedial or response costs, restitution, civil or
criminal penalties, injunctive relief, or other type of relief, resulting from
or based upon (a) the presence, placement, discharge, emission or release
(including intentional and unintentional, negligent and non-negligent, sudden or
non-sudden, accidental or non-accidental placement, spills, leaks, discharges,
emissions or releases) of any Hazardous Material at, in, or from Property,
whether or not owned by Borrower, or (b) any other circumstances forming the
basis of any violation, or alleged violation, of any Environmental Law.

         "Environmental Laws" means all foreign, federal, state or local laws,
statutes, common law duties, rules, regulations, ordinances and codes, together
with all administrative orders, directed duties, requests, licenses,
authorizations and permits of, and agreements with, any Governmental
Authorities, in each case relating to environmental, health, safety and land use
matters, including the


                                      -3-
<PAGE>
Comprehensive Environmental Response, Compensation and Liability Act of 1980,
the Clean Air Act, the Federal Water Pollution Control Act of 1972, the Solid
Waste Disposal Act, the Federal Resource Conservation and Recovery Act, the
Toxic Substances Control Act and the Emergency Planning and Community
Right-to-Know Act.

         "Equity Securities" of any Person shall mean (a) all common stock,
preferred stock, participations, shares, partnership interests or other equity
interests in and of such Person (regardless of how designated and whether or not
voting or non-voting) and (b) all warrants, options and other rights to acquire
any of the foregoing.

         "Existing Equipment Indebtedness" shall mean Indebtedness now or
hereafter owed by Borrower with respect to the lease obligations outstanding on
the date hereof and arising under the Master Lease Agreement by and between
Borrower and Comdisco, Inc., dated as of May 1, 1995.

         "Event of Default" has the meaning given to that term in Section 9.01.

         "Funding Date" shall mean a date on which a Loan is made to or on
account of Borrower under this Agreement, provided, however, the Funding Date
shall in all cases be a Business Day.

         "GAAP" shall mean generally accepted accounting principles and
practices as in effect in the United States of America from time to time and
recognized as such by the American Institute of Certified Public Accountants,
consistently applied. Each accounting term used but not otherwise expressly
defined herein shall have the meaning given to it by GAAP.

         "Guarantor" means Acusphere Securities Corporation.

         "Guarantor Collateral" means the personal property of Guarantor in
which Guarantor granted or pledged Lenders a security interest.

         "Guarantor Security Agreement" means that certain Security Agreement
executed on or about the date hereof executed in favor of Lenders whereby
Guarantor granted a security interest in all of its personal property in favor
of Lenders to secure its obligations under the Guaranty.

         "Guaranty" means that certain Guaranty executed by Guarantor in favor
of Lenders on or about the date hereof whereby the Guarantor guaranteed the
payment and performance of all obligations of Borrower to Lenders.

         "GV" means GATX Ventures, Inc., and its successors and/or assigns.

         "Hazardous Materials" means all those substances which are regulated
by, or which may form the basis of liability under, any Environmental Law,
including all substances identified under any Environmental Law as a pollutant,
contaminant, hazardous waste, hazardous constituent, special waste, hazardous
substance, hazardous material, or toxic substance, or petroleum or petroleum
derived substance or waste.

         "Indebtedness" shall mean, with respect to Borrower or any Subsidiary,
the aggregate amount of, without duplication,

                                      -4-
<PAGE>
         (a) all obligations of such Person for borrowed money,

         (b) all obligations of such Person evidenced by bonds, debentures,
notes or other similar instruments,

         (c) all obligations of such Person to pay the deferred purchase price
of property or services (excluding trade payables aged less than 180 days),

         (d) all capital lease obligations of such Person,

         (e) all obligations or liabilities of others secured by a lien on any
asset of such Person, whether or not such obligation or liability is assumed,

         (f) all obligations or liabilities of others guaranteed by such Person;
and

         (g) any other obligations or liabilities which are required by GAAP to
be shown as debt on the balance sheet of such Person or to which reference is
made by footnotes thereto.

         Unless otherwise indicated, the term "Indebtedness" shall include all
Indebtedness of Borrower and the Subsidiaries.

         "Intellectual Property" shall mean all of Borrower's right, title and
interest in and to patents, patent rights (and applications and registrations
therefor), trademarks and service marks (and applications and registrations
therefor, other than "Intent to Use" trademark applications), inventions,
copyrights, mask works (and applications and registrations therefor), trade
names, trade styles, software and computer programs, trade secrets, methods,
processes, know how, drawings, specifications, descriptions, and all memoranda,
notes, and records with respect to any research and development, all whether now
owned or subsequently acquired or developed by Borrower and whether in tangible
or intangible form or contained on magnetic media readable by machine together
with all such magnetic media.

         "Investment" shall mean the purchase or acquisition of any capital
stock, equity interest, or any obligations or other securities of, or any
interest in, any Person, or the extension of any advance, loan, extension of
credit or capital contribution to, or any other investment in, any Person.

         "Lien" shall mean any voluntary or involuntary security interest,
pledge, bailment, lease, mortgage, hypothecation, conditional sales and title
retention agreements, charge, claim, encumbrance or other lien with respect to
the Property in favor of any Person.

         "Loan" means the Loan advanced by a Lender to Borrower under this
Agreement according to the Commitment of such Lender.

         "Loan Rate" shall mean the per annum rate of interest (based on a year
of twelve 30-day months) set forth on the cover page of this Agreement.

         "MAC Occurrence" shall have the meaning set forth in Section 2.02(d) of
this Agreement.

                                      -5-
<PAGE>
         "Material Adverse Effect" shall have the meaning set forth in Section
3.01(a) of this Agreement.

         "Note" shall mean one of the secured promissory notes of Borrower
substantially in the form of Exhibit A.

         "Obligations" has the meaning given to that term in Section 5.01.

         "Operative Documents" shall mean this Agreement, the Notes, the
Guaranty, the Guarantor Security Agreement and the Warrants and all other
documents, instruments and agreements executed and delivered in connection
herewith or therewith or in respect of the closing of the transactions
contemplated hereby or thereby.

         "Payment Date" has the meaning given to that term in the applicable
Note.

         "Permitted Indebtedness" shall mean and include:

         (a)      Indebtedness of Borrower to Lenders;

         (b)      Indebtedness of Borrower secured by Liens permitted under
                  clause (e) of the definition of Permitted Liens up to an
                  aggregate principal amount or aggregate original acquisition
                  value of $3,000,000 (excluding the Transamerica Indebtedness
                  and the Existing Equipment Indebtedness);

         (c)      Indebtedness arising from the endorsement of instruments in
                  the ordinary course of business;

         (d)      Indebtedness existing on the date hereof and set forth on the
                  disclosure schedule attached hereto on the Disclosure
                  Schedule;

         (e)      The Existing Equipment Indebtedness, provided the aggregate
                  principal amount or aggregate original acquisition value of
                  such Indebtedness does not exceed $2,200,000;

         (f)      The Comdisco Indebtedness, provided the aggregate principal
                  amount of such Indebtedness shall not exceed $1,800,000 and
                  such Indebtedness shall be repaid on or before November 15,
                  2001;

         (g)      The Transamerica Indebtedness, provided that the aggregate
                  principal amount or aggregate original acquisition value of
                  such Indebtedness shall not exceed $3,000,000;

         (h)      The Elan Indebtedness, provided the terms of such Indebtedness
                  do not require the repayment of any such Indebtedness prior to
                  the final Payment Date of the Loan; and

                                      -6-
<PAGE>
         (i)      Subordinated Indebtedness.

         "Permitted Investments" shall mean and include:

         (a)      Deposits with commercial banks organized under the laws of the
                  United States or a state thereof to the extent such deposits
                  are fully insured by the Federal Deposit Insurance
                  Corporation;

         (b)      Investments in marketable obligations issued or fully
                  guaranteed by the United States and maturing not more than one
                  (1) year from the date of issuance;

         (c)      Investments in open market commercial paper rated at least
                  "A1" or "P1" or higher by a national credit rating agency and
                  maturing not more than one (1) year from the creation thereof;

         (d)      Investments pursuant to or arising under currency agreements
                  or interest rate agreements entered into in the ordinary
                  course of business;

         (e)      Investments consisting of deposit accounts of Borrower in
                  which Lenders have a perfected security interest;

         (f)      Investments in the Elan Joint Venture in accordance with the
                  Elan Joint Venture Agreements; and

         (g)      Other Investments aggregating not in excess of Two Hundred
                  Fifty Thousand Dollars ($250,000) at any time.

         "Permitted Liens" shall mean:

         (a) the Lien created by this Agreement,

         (b) Liens for fees, taxes, levies, imposts, duties or other
governmental charges of any kind which are not yet delinquent or which are being
contested in good faith by appropriate proceedings which suspend the collection
thereof (provided, however, that such proceedings do not involve any substantial
danger of the sale, forfeiture or loss of any item of equipment and that
Borrower has adequately bonded such Lien or reserves sufficient to discharge
such Lien have been provided on the books of Borrower),

         (c) Liens identified on the Disclosure Schedule,

         (d) Liens to secure payment of worker's compensation, employment
insurance, old age pensions or other social security obligations of Borrower in
the ordinary course of business of Borrower,

                                      -7-
<PAGE>
         (e) Liens upon any equipment or other personal property acquired by
Borrower after the date hereof to secure (i) the purchase price of such
equipment or other personal property or (ii) lease obligations or indebtedness
incurred solely for the purpose of financing the acquisition of such equipment
or other personal property; provided that (A) such Liens are confined solely to
the equipment or other personal property so acquired and the original amount
secured does not exceed the acquisition price thereof, and (B) no such Lien
shall be created, incurred, assumed or suffered to exist in favor of Borrower's
officers, directors or shareholders holding five percent (5%) or more of
Borrower's Equity Securities,

         (f) carriers', warehousemen's, mechanics', landlords', materialmen's,
repairmen's or other similar Liens arising in the ordinary course of business
which are not delinquent or remain payable without penalty or which are being
contested in good faith and by appropriate proceedings;

         (g) non-exclusive licenses of Intellectual Property entered into in the
ordinary course of business and licenses existing on the date hereof with
Acusphere Newco Ltd. and non-exclusive licenses and exclusive licenses (provided
such exclusive licenses concern no more than four (4) Compounds (as defined in
the JDOA)) in favor of Acusphere Newco Ltd.;

         (h) Liens securing the Comdisco Indebtedness, provided such Liens are
released on or before November 15, 2001; and

         (i) Liens securing the Transamerica Indebtedness and Existing Equipment
Indebtedness, provided such Liens shall only attach to the specific equipment
financed with the Transamerica Indebtedness and Existing Equipment Indebtedness,
respectively.

         "Person" shall mean and include an individual, a partnership, a
corporation, a business trust, a joint stock company, a limited liability
company, an unincorporated association or other entity and any domestic or
foreign national, state or local government, any political subdivision thereof,
and any department, agency, authority or bureau of any of the foregoing.

          "Property" means any interest in any kind of property or asset,
whether real, personal or mixed, whether tangible or intangible.

         "Subordinated Indebtedness" shall mean Indebtedness subordinated to the
Obligations on terms and conditions acceptable to Lenders including, without
limiting the generality of the foregoing, subordination of such Indebtedness in
right of payment to the prior payment in full of the Obligations, the
subordination of the priority of any Lien at any time securing such Indebtedness
to the Lien of Lender in the collateral covered thereby, and the subordination
of the rights of the holder of such Indebtedness to enforce its junior Lien
following an Event of Default hereunder.

         "Subsidiary" shall mean any corporation of which a majority of the
outstanding capital stock entitled to vote for the election of directors
(otherwise than as the result of a default) is owned by Borrower directly or
indirectly through Subsidiaries.

         "Term" shall mean the period from and after the date hereof until the
payment or satisfaction in full of all Obligations under this Agreement and the
other Operative Documents.

                                      -8-
<PAGE>
         "Transamerica Indebtedness" means the Indebtedness owed by Borrower to
Transamerica Business Credit Corporation pursuant to a Master Lease Agreement by
and among Borrower, Guarantor, and Transamerica Business Credit Corporation,
dated as of February 21, 2001.

         "VLL" means Venture Lending & Leasing III, Inc.

         "Warrants" shall mean separate warrants to be issued at the direction
of the Lenders to purchase securities of Borrower substantially in the form of
Exhibit B.

         1.02. Headings. Headings in this Agreement and each of the other
Operative Documents are for convenience of reference only and are not part of
the substance hereof or thereof.

         1.03. Plural Terms. All terms defined in this Agreement or any other
Operative Document in the singular form shall have comparable meanings when used
in the plural form and vice versa.

         1.04. Construction. This Agreement is the result of negotiations among,
and has been reviewed by, Borrower and Lenders and their respective counsel.
Accordingly, this Agreement shall be deemed to be the product of all parties
hereto, and no ambiguity shall be construed in favor of or against Borrower or
Lenders.

         1.05. Entire Agreement. This Agreement, together with the terms set
forth in each of the other Operative Documents, taken together, constitute and,
contain the entire agreement of Borrower and Lenders and, with regard to their
respective subject matters, supersede any and all prior agreements, term sheets,
negotiations, correspondence, understandings and communications among the
parties, whether written or oral, with respect to their respective subject
matters. Borrower acknowledges that it is not relying on any representation or
agreement made by any Lender or any employee, agent or attorney of any Lender,
other than the specific agreements set forth in this Agreement and the Operative
Documents.

         1.06. Other Interpretive Provisions. References in this Agreement to
"Articles," "Sections," "Exhibits," "Schedules" and "Annexes" are to articles,
sections, exhibits, schedules and annexes herein and hereto unless otherwise
indicated. References in this Agreement and each of the other Operative
Documents to any document, instrument or agreement shall include (a) all
exhibits, schedules, annexes and other attachments thereto, (b) all documents,
instruments or agreements issued or executed in replacement thereof, and (c)
such document, instrument or agreement, or replacement or predecessor thereto,
as amended, modified and supplemented from time to time and in effect at any
given time. The words "hereof," "herein" and "hereunder" and words of similar
import when used in this Agreement or any other Operative Document shall refer
to this Agreement or such other Operative Document, as the case may be, as a
whole and not to any particular provision of this Agreement or such other
Operative Document, as the case may be. The words "include" and "including" and
words of similar import when used in this Agreement or any other Operative
Document shall not be construed to be limiting or exclusive. Unless otherwise
indicated in this Agreement or any other Operative Document, all accounting
terms used in this Agreement or any other Operative Document shall be construed,
and all accounting and financial computations hereunder or thereunder shall be
computed, in accordance with GAAP.

                                      -9-
<PAGE>
                                   ARTICLE II
                                   THE CREDIT

         2.01. Credit Facility.

                  (a) The Commitment Amount. Subject to the terms and conditions
of this Agreement and relying upon the representations and warranties herein set
forth as and when made or deemed to be made, each Lender severally agrees to
lend to Borrower one Loan in the aggregate amount of such Lender's Commitment.
The Loans made on the Funding Date shall be made pro rata in accordance with
each Lender's Commitment and Commitment Percentage and shall be in an aggregate
amount of not more than Five Million Dollars ($5,000,000). No Lender shall be
required to make a Loan in an aggregate amount in excess of its Commitment. The
Loans may not be prepaid, except in accordance with Section 2.03(d) and Section
7.01(f) hereof.

                  (b) Interest Rates. Borrower shall pay interest on the unpaid
principal amount of each Loan from the date of such Loan until such Loan is paid
in full, at a per annum rate of interest equal to the Loan Rate for such Loan
determined in accordance with the definition of Loan Rate. The Loan Rate
applicable to a Loan shall not be subject to change in the absence of manifest
error. All computations of interest on a Loan shall be based on a year of twelve
30-day months. If Borrower pays interest on a Loan which is determined to be in
excess of the then legal maximum rate, then that portion of each interest
payment representing an amount in excess of the then legal maximum rate shall be
deemed a payment of expenses or principal and applied first, to the payment of
principal outstanding under the Loan; then to any expenses owed by Borrower to
Lender under the terms hereof, with the excess (if any) to be timely refunded to
Borrower.

                  (c) Payments of Principal and Interest. Commencing on the
first Payment Date under each Lender's Loan, Borrower shall make six (6) monthly
payments of accrued interest only on each Payment Date as set forth in such
Lender's Note. Commencing on the seventh Payment Date of each Loan Borrower
shall make twenty-four (24) equal monthly payments of principal in the amount of
4.167% of the Loan Amount plus accrued interest on the outstanding principal
amount of such Lender's Loan on each subsequent Payment Date as set forth in
such Lender's Note. If the Funding Date is not the first day of the month,
Borrower shall pay interim interest (accruing from the Funding Date through the
last day of that month) on the Funding Date.

                                      -10-
<PAGE>
                  (d) VLL shall not be obligated to make any Loan under its
Commitment if at the time of or after giving effect to the proposed Loan VLL
would no longer qualify as: (A) a "venture capital operating company" under U.S.
Department of Labor Regulations Section 2510.3-101(d), Title 29 of the Code of
Federal Regulations, as amended; and (B) a "business development company" under
the provisions of federal Investment Company Act of 1940, as amended; and (C) a
"regulated investment company" under the provisions of the Internal Revenue Code
of 1986, as amended. VLL hereby represents that as of the Closing Date it is so
qualified, and has no reason to believe that it will not remain so qualified
through the Commitment Termination Date. In the event that VLL declines to make
a requested Loan solely on the basis of its failure to be so qualified, then the
total number of shares of stock issuable to VLL upon exercise of the Warrant
issued to VLL pursuant to this Agreement shall be proportionately reduced to a
number determined by multiplying such total number of shares (68,421) with
respect to this Agreement by a fraction the numerator of which is the amount of
the Loan actually funded by VLL, and the denominator of which is the amount of
VLL's original Commitment.

         2.02. Use of Proceeds; the Loan and the Notes; Disbursement.

                  (a) Use of Proceeds. The proceeds of the Loans shall be used
solely for working capital, capital equipment acquisition or general corporate
purposes of Borrower.

                  (b) The Loans and the Notes. The obligation of Borrower to
repay the unpaid principal amount of and interest on each Lender's Loan shall be
evidenced by a Note issued to each Lender and each Lender is authorized to
endorse on a grid annexed to its Note appropriate notations regarding payments
made on the Note; provided, however, that the failure to make, or an error in
making, any such notation shall not limit or otherwise affect the obligations of
Borrower hereunder or thereunder.

                  (c) Disbursement. Each Lender shall disburse its Loan by wire
transfer to Borrower at Fleet Bank, 100 Federal Street, Boston, MA 02110,
Account No. 003121-0933, ABA Routing No. 011000138, Beneficiary: ACUSPHERE, INC.
Notwithstanding anything stated herein to the contrary, no Lender shall have any
obligation to advance funds on behalf of the another Lender.

                  (d) Termination of Commitment to Lend. Notwithstanding
anything to the contrary in the Operative Documents, Lenders' obligations to
advance the Loans hereunder shall terminate on the earliest of (i) the
occurrence of any Event of Default hereunder and (ii) the Commitment Termination
Date. Notwithstanding the foregoing, each Lender's obligation to lend the
undisbursed portion of such Lender's Commitment to Borrower shall terminate if,
in Lenders' sole judgment, there has been a material adverse change in the
general affairs, management, results of operations, condition (financial or
otherwise) or prospects of Borrower, whether or not arising from transactions in
the ordinary course of business, or there has been any material adverse
deviation by Borrower from the business projections of Borrower dated July 5,
2001 presented to Lenders, on or before the date of this Agreement
(collectively, a "MAC Occurrence").

         2.03. Other Payment Terms.

                                      -11-
<PAGE>
                  (a) Place and Manner. Borrower shall make all payments due to
Lenders in lawful money of the United States. All payments of principal,
interest, fees and other amounts payable by Borrower hereunder shall be made, in
immediately available funds, by debit to any account of Borrower with Payment
Agent not later than 10:00 a.m. California time, on the date on which such
payment is made. Borrower shall make such payments via wire transfer as follows:
<TABLE>
<CAPTION>
         GV Payment
         ----------
         <S>                                        <C>
         GATX Ventures, Inc
         Bank Name:                                 Bank of America
         Bank Address:                              Dallas, Texas  75202
         Account No.:                               3750878673
         ABA Routing No.:                           111-000012
         Reference:                                 ACUSPHERE Invoice #___________

         VLL Payment
         -----------
         Venture Lending & Leasing III, Inc.
         Bank Name:                                 Union Bank of California, N.A.

         ABA Routing No.:                           122000496
                                                    F/C Client Funds #700016472-00
         Reference:                                 Venture Lending & Leasing III Custody
</TABLE>

                  Any payment received by one Lender for the account of the
         other Lender shall be paid promptly to such Lender, in like funds, for
         the Loan in respect of which such payment is made; provided, however,
         that Borrower hereby (i) authorizes each Lender to initiate debit
         entries to Borrower's account shown in Section 2.02(c) above (its
         "Primary Operating Account"), through Automated Clearinghouse ("ACH")
         transfers, in order to satisfy the Obligations; (ii) agrees to provide
         each Lender at least thirty (30) days' written notice in advance of any
         change in Borrower's Primary Operating Account; and (iii) grants each
         Lender any additional authorizations necessary to begin ACH debits from
         a new account which becomes the Primary Operating Account. Any payment
         received by any Lender hereunder for the account of any other Lender
         shall be paid promptly to such Lender, in like funds, for the Loan in
         respect of which such payment is made.

                  (b) Date. Whenever any payment due hereunder shall fall due on
a day other than a Business Day, such payment shall be made on the next
succeeding Business Day, and such extension of time shall be included in the
computation of interest or fees, as the case may be.

                                      -12-
<PAGE>
                  (c) Default Rate. If either (i) any amounts required to be
paid by Borrower under this Agreement or the other Operative Documents
(including principal or interest payable on the Loan, any fees or other amounts)
remain unpaid after such amounts are due, or (ii) an Event of Default has
occurred and is continuing, Borrower shall pay interest on the outstanding
principal balance hereunder from the date due or from the date of the Event of
Default, as applicable, until such past due amounts are paid in full or until
all Events of Defaults are cured, as applicable, at a per annum rate equal to
the Default Rate. All computations of such interest at the Default Rate shall be
based on a year of 360 days and twelve 30-day months.

                  (d) Prepayment. Upon ten (10) Business Days' prior written
notice to Lenders, Borrower may, at its option, at any time on or after
September 15, 2002, prepay all, and not less than all, of the Loans in full by
paying to Lenders an amount equal to (i) all principal with respect to each
Loan; (ii) any accrued and unpaid interest; (iii) an amount equal to the sum of
all remaining unpaid interest which would have otherwise come due under the
Loans discounted to the relevant date at a rate of five percent (5%) per annum,
and (iv) all other sums, if any, that shall have become due and payable
hereunder. Except as set forth in Section 7.01(f) and this Section 2.03(d), the
Loans may not be prepaid.

         2.04. Facility Fee. Borrower shall pay a fee in the aggregate amount of
$50,000 to Lenders upon the closing of the operative Documents. Such fee shall
be deemed earned by Lenders when paid.

         2.05. Good Faith Deposit. Borrower has paid a good faith deposit in the
aggregate amount of $20,000 to Lenders (the "Good Faith Deposit"). Any portion
of the Good Faith Deposit not utilized to pay Lenders' expenses, including
reasonable attorneys' fees in connection with due diligence or the negotiation,
documentation, administration and funding of the Loans will be applied pro rata
to the initial payment due under the Notes.

                                  ARTICLE III
                         REPRESENTATIONS AND WARRANTIES

         3.01. Representations and Warranties. Except as set forth in the
Disclosure Schedule, Borrower and Guarantor make the following representations
and warranties to Lenders as of the date hereof and again on the Funding Date:

                  (a) Organization and Qualification. Borrower and Guarantor are
each corporations duly organized and validly existing and in good standing under
the laws of their respective states of incorporation and are qualified and
licensed to do business in, and are in good standing in, any state in which the
conduct of their business or their ownership of Property requires that they be
so qualified or in which the Collateral or Guarantor Collateral is located,
except for such states as to which any failure to so qualify would not have a
material adverse effect on the financial condition, business or operations of
Borrower or Guarantor (a "Material Adverse Effect").

                                      -13-
<PAGE>
                  (b) Authority. Borrower and Guarantor have all necessary power
and authority to execute, deliver, and perform in accordance with the terms
thereof, the Operative Documents to which it is a party. Borrower and Guarantor
have all requisite power and authority to own and operate their respective
properties and to carry on their respective businesses as now conducted.

                  (c) Conflict with Other Instruments, etc. Neither the
execution and delivery of any Loan Document to which Borrower or Guarantor is a
party nor the consummation of the transactions therein contemplated nor
compliance with the terms, conditions and provisions thereof will (i) conflict
with or result in a breach of any of the terms, conditions or provisions of the
articles of incorporation and the by-laws, or other organizational documents of
Borrower or Guarantor or any law or any regulation, order, writ, injunction or
decree of any court or governmental instrumentality or any material agreement or
instrument to which Borrower or Guarantor is a party or by which it or any of
their properties is bound or to which they or any of their properties are
subject, or (ii) constitute a default thereunder or (iii) result in the creation
or imposition of any Lien, other than Permitted Liens, in any such case with
respect to (i) and (ii) above, which could reasonably be expected to have a
Material Adverse Effect.

                  (d) Properties. Borrower has good and marketable title to the
Collateral, free and clear of all Liens, other than Permitted Liens. Guarantor
has good and marketable title to the Guarantor Collateral, free and clear of all
Liens, other than Permitted Liens. Borrower has good title and ownership of, or
is licensed under, all of Borrower's current Intellectual Property, with no
known infringement of the rights of others. Borrower has not received any
communications alleging that Borrower has violated, or by conducting its
business as proposed, would violate any proprietary rights of any other Person.
Borrower has no knowledge of any infringement or violation by it of the
intellectual property rights of any third party and has no knowledge of any
violation or infringement by a third party of any of its Intellectual Property.
The Collateral and the Intellectual Property constitute substantially all of the
assets and property of Borrower. The Guarantor Collateral constitutes
substantially all of the assets and property of Borrower.

                                      -14-
<PAGE>
                  (e) Authorization, Governmental Approvals, etc. The execution
and delivery by Borrower and Guarantor of each Operative Document to which it is
a party, the granting of the security interest in the Collateral and Guarantor
Collateral, the issuance of the Warrants, the issuance of the securities into
which the Warrants are exercisable, the issuance of any securities into which
the securities issuable upon exercise of the Warrants are convertible, and the
performance of the obligations herein and therein contemplated have each been
duly authorized by all necessary action on the part of Borrower and Guarantor.
No authorization, consent, approval, license or exemption of, and no
registration, qualification, designation, declaration or filing with, or notice
to, any Person is, was or will be necessary for (i) the valid execution and
delivery of any Operative Document to which Borrower or Guarantor is a party,
(ii) the performance of Borrower's or Guarantor's obligations under any
Operative Document, or (iii) the granting of the security interest in the
Collateral and Guarantor Collateral, except for filings in connection with the
perfection of the security interest in any of the Collateral or Guarantor
Collateral or the issuance of the Warrants. The Operative Documents to which
Borrower or Guarantor are a party have been or will be duly executed and
delivered and constitute or will constitute legal, valid and binding obligations
of Borrower and Guarantor, enforceable in accordance with their respective
terms, except as the enforceability thereof may be limited by bankruptcy,
insolvency or other similar laws of general application relating to or affecting
the enforcement of creditors' rights or by general principles of equity.

                  (f) Litigation. Except as disclosed in the Disclosure
Schedule, there are no actions or proceedings pending by or against Borrower or
Guarantor before any court or administrative agency in which an adverse decision
could have a Material Adverse Effect or a material adverse effect on the
aggregate value of the Collateral or the Guarantor Collateral. Borrower and
guarantor do not have knowledge of any such pending or threatened actions or
proceedings.

                  (g) Security Interest. Assuming the proper filing of one or
more financing statement(s) identifying the Collateral with the proper state
and/or local authorities, the security interests in the Collateral granted to
Lenders pursuant to this Agreement (i) constitute and will continue to
constitute first priority security interests (except to the extent any other
Permitted Lien may create any priority to Lenders' Lien under this Agreement)
and (ii) are and will continue to be superior and prior to the rights in the
Collateral of all other creditors of Borrower (except to the extent of such
Permitted Liens). Except as set forth in the Disclosure Schedule, neither
Borrower nor Guarantor owns any right, title or interest in or to any real
property (other than leasehold interests), motor vehicles, promissory notes or
other property (excluding Intellectual Property) with respect to which a
security interest must be perfected by a method other than the filing of a UCC-1
financing statement. Except as set forth in the Disclosure Schedule, Borrower
has no right, title or interest in any federally registered patents, patent
applications, trademarks, trademark applications, copyrights, or copyright
applications.

                                      -15-
<PAGE>
                  (h) Name; Location of Chief Executive Office, Principal Place
of Business and Collateral. Neither Borrower nor Guarantor has done business
under any name other than those specified on the signature page hereof, other
than the Borrower previously conducted business under the name of "Polymers for
Medicine, Inc." The chief executive office, principal place of business, and the
place where Borrower and Guarantor maintain their records concerning the
Collateral and Guarantor Collateral are presently located at the addresses set
forth on the cover page and the Disclosure Schedule. The Collateral and
Guarantor Collateral is presently located at the addresses set forth on the
cover page and the Disclosure Schedule.

                  (i) Solvency, Etc. Each of Borrower and Guarantor is Solvent
(as defined below) and, after the execution and delivery of the Operative
Documents and the consummation of the transactions contemplated thereby,
Borrower and Guarantor will be Solvent. "Solvent" shall mean, with respect to
any Person on any date, that on such date (a) the fair going concern value of
the property of such Person is greater than the fair value of the liabilities
(including, without limitation, contingent liabilities) of such Person, (b) the
present fair saleable value of the assets of such Person is not less than the
amount that will be required to pay the probable liability of such Person on its
debts as they become absolute and matured, (c) such Person does not intend to,
and does not believe that it will, incur debts or liabilities beyond such
Person's ability to pay as such debts and liabilities mature and (d) such Person
is not engaged in business or a transaction, and is not about to engage in
business or a transaction, for which such Person's property would constitute an
unreasonably small capital.

                  (j) Catastrophic Events; Labor Disputes. None of Borrower or
its properties is or has been affected by any fire, explosion, accident, strike,
lockout or other labor dispute, drought, storm, hail, earthquake, embargo, act
of God or other casualty that could reasonably be expected to have a Material
Adverse Effect. There are no disputes presently subject to grievance procedure,
arbitration or litigation under any of the collective bargaining agreements,
employment contracts or employee welfare or incentive plans to which Borrower is
a party, and there are no strikes, lockouts, work stoppages or slowdowns, or, to
the knowledge of Borrower, jurisdictional disputes or organizing activity
occurring or threatened which could reasonably be expected to have a Material
Adverse Effect.

                  (k) Financial Statements. All financial statements relating to
Borrower, Guarantor or any Affiliate that have been or may hereafter be
delivered by Borrower to each Lender present fairly in all material respects
Borrower's and Guarantor's financial condition as of the date thereof and
Borrower's results of operations for the period then ended. No event has
occurred and no condition exists which could reasonably be expected to have a
Material Adverse Effect since December 31, 2000.

                                      -16-
<PAGE>
                  (l) Accuracy of Information Furnished. None of the Operative
Documents and none of the other certificates, statements or information
furnished to Lenders by or on behalf of Borrower or Guarantor in connection with
the Operative Documents or the transactions contemplated thereby contains any
untrue statement of a material fact or omits to state a material fact necessary
to make the statements therein, in light of the circumstances under which they
were made, not misleading. Lenders recognize that all financial projections
furnished to Lenders by or on behalf of Borrower and Guarantor in connection
with the Operative Documents or the transactions contemplated thereby are not to
be viewed as facts and that actual results during the period or periods covered
by such projections may differ from the projected or forecasted results.

                  (m) Certain Agreements of Officers, Employees and Consultants.

                           (i) To the knowledge of Borrower, no officer,
employee or consultant of Borrower is, or is now expected to be, in violation of
any material term of any employment contract, proprietary information agreement,
nondisclosure agreement, noncompetition agreement, or any other material
contract or agreement or any restrictive covenant relating to the right of any
such officer, employee or consultant to be employed by Borrower because of the
nature of the business conducted or to be conducted by Borrower or relating to
the use of trade secrets or proprietary information of others, and to Borrower's
knowledge, the continued employment of Borrower's officers, employees and
consultants does not subject Borrower to any material liability for any claim or
claims arising out of or in connection with any such contract, agreement, or
covenant.

                           (ii) To the knowledge of Borrower, no officers of
Borrower, and no employee or consultant of Borrower whose termination, either
individually or in the aggregate, could reasonably be expected to have a
Material Adverse Effect, has any present intention of terminating his or her
employment or consulting relationship with Borrower.

                  (n) Subsidiaries. Borrower has no Subsidiaries or Affiliates
other than Guarantor and Acusphere Newco, Ltd.

                                   ARTICLE IV
                             REPORTING REQUIREMENTS

         4.01. Furnishing Reports. Borrower shall furnish to Lenders:

                                      -17-
<PAGE>
                  (a) Financial Statements, Reports, Certificates. Borrower
shall deliver to each Lender: (1) as soon as available, but in any event within
thirty (30) days after the end of each month, a company prepared unaudited
balance sheet, income statement and cash flow statement covering Borrower's
operations during such period, certified by a president, treasurer, secretary or
chief financial officer of Borrower (a "Responsible Officer"); (2) as soon as
available, but in any event within ninety (90) days after the end of Borrower's
fiscal year, audited financial statements of Borrower prepared in accordance
with generally accepted accounting principles, consistently applied, together
with an unqualified opinion (except with respect to going concern) on such
financial statements of a nationally recognized or other independent public
accounting firm reasonably acceptable to Lenders; and (3) such other financial
information as Lenders may reasonably request from time to time. From and after
such time as Borrower becomes a publicly reporting company, promptly as they are
available and in any event: (x) within five (5) Business Days of filing of
Borrower's Form 10-K with the Securities and Exchange Commission after the end
of each fiscal year of Borrower, the financial statements of Borrower filed with
such Form 10-K; and (y) within five (5) Business Days of filing of Borrower's
Form 10-Q with the Securities and Exchange Commission after the end of each of
the first three fiscal quarters of Borrower, the financial statements of
Borrower filed with such Form 10-Q; provided that no default shall occur in the
delay in sending such public filings to Lenders unless Borrower does not deliver
copies within three (3) Business Days of written notice of Borrower's failure to
provide copies to Lenders. In addition, Borrower shall deliver to each Lender
(i) promptly upon becoming available, copies of all material statements, reports
and notices sent or made available generally by Borrower to its all of its
security holders; (ii) immediately upon receipt of notice thereof, a report of
any material legal actions or governmental investigations pending or threatened
against Borrower; and (iii) such other information as Lenders may reasonably
request from time to time.

                  (b) Certificates of Compliance. Each time financial statements
are furnished pursuant to Section 4.01(a) above, there shall be delivered to
each Lender, a certificate signed by a Responsible Officer (each, an "Officer's
Certificate") with respect to such financial reports to the effect that: (i) no
Event of Default or Default has occurred and is continuing hereunder since the
date of this Agreement or, if later, since the date of the prior Officer's
Certificate or, if such an event or condition has occurred and is continuing,
the nature and extent thereof and the action Borrower proposes to take with
respect thereto, and (ii) Borrower is in compliance with the provisions of
Articles 6 and 7.

                  (c) Notice of Event of Loss. As soon as possible, and in any
event within ten (10) days after Borrower has knowledge thereof, Borrower shall
notify each Lender in writing in reasonable detail of any material Collateral
which is lost, stolen, destroyed, damaged beyond repair, rendered permanently
unfit for use, or seized by any governmental authority, the loss or destruction
of which could reasonably be expected to have a Material Adverse Effect.

                  (d) Notice of Defaults. As soon as possible, and in any event
within five (5) days after the discovery of a Default or an Event of Default
provide each Lender, with an Officer's Certificate of Borrower setting forth the
facts relating to or giving rise to such Default or Event of Default and the
action which Borrower proposes to take with respect thereto.

                                      -18-
<PAGE>
                                   ARTICLE V
                           GRANT OF SECURITY INTEREST
                     GENERAL PROVISIONS CONCERNING SECURITY

         5.01. Grant of Security Interest. Borrower, in order to secure the
payment of the principal and interest with respect to the Loans made pursuant to
this Agreement, all other sums due under and in respect hereof and of the other
Operative Documents, including fees, charges, expenses and attorneys' fees and
costs and the performance and observance by Borrower of all other terms,
conditions, covenants and agreements herein and in the other Operative Documents
(all such amounts and obligations being herein sometimes called the
"Obligations"), does hereby grant to Lenders and their successors and assigns, a
security interest in and to the following property (collectively, the
"Collateral"): All right, title, interest, claims and demands of Borrower in and
to all personal property of Borrower, including, without limitation:

                  (a) All goods and equipment now owned or hereafter acquired,
including, without limitation, all laboratory equipment, computer equipment,
office equipment, machinery, fixtures, vehicles (including motor vehicles and
trailers), and any interest in any of the foregoing, and all attachments,
accessories, accessions, replacements, substitutions, additions, and
improvements to any of the foregoing, wherever located;

                  (b) All inventory now owned or hereafter acquired, including,
without limitation, all merchandise, raw materials, parts, supplies, packing and
shipping materials, work in process and finished products including such
inventory as is temporarily out of Borrower's custody or possession or in
transit and including any returns upon any accounts or other proceeds, including
insurance proceeds, resulting from the sale or disposition of any of the
foregoing and any documents of title representing any of the above, and
Borrower's books relating to any of the foregoing;

                  (c) All contract rights and general intangibles (including
Intellectual Property), now owned or hereafter acquired, including, without
limitation, goodwill, license agreements, franchise agreements, blueprints,
drawings, purchase orders, customer lists, route lists, infringements, claims,
computer programs, computer disks, computer tapes, literature, reports,
catalogs, design rights, income tax refunds, payments of insurance and rights to
payment of any kind;

                  (d) All now existing and hereafter arising accounts, contract
rights, royalties, license rights and all other forms of obligations owing to
Borrower arising out of the sale or lease of goods, the licensing of technology
or the rendering of services by Borrower (subject, in each case, to the
contractual rights of third parties to require funds received by Borrower to be
expended in a particular manner), whether or not earned by performance, and any
and all credit insurance, guaranties, and other security therefor, as well as
all merchandise returned to or reclaimed by Borrower and Borrower's books
relating to any of the foregoing;

                                      -19-
<PAGE>
                  (e) All documents, cash, deposit accounts, letters of credit,
certificates of deposit, instruments, chattel paper and investment property,
including, without limitation, all securities, whether certificated or
uncertificated, security entitlements, securities accounts, commodity contracts
and commodity accounts, and all financial assets held in any securities account
or otherwise, wherever located, now owned or hereafter acquired and Borrower's
books relating to the foregoing; and

                  (f) Any and all claims, rights and interests in any of the
above and all substitutions for, additions and accessions to and proceeds
thereof, including, without limitation, insurance, condemnation, requisition or
similar payments and proceeds of the sale or licensing of Intellectual Property.

Notwithstanding anything to the contrary, the grant of security interest as
provided in this Agreement shall not extend to, and the term "Collateral" shall
not include, any equipment (including any improvements thereon and the proceeds
thereof) subject to (i) a loan agreement or capital lease in effect on the date
hereof which by its terms prohibits any other Lien on such equipment and is
disclosed in the Disclosure Schedule, (ii) Existing Equipment Indebtedness,
(iii) Transamerica Indebtedness and (iv) Permitted Liens permitted under
subsection (b) of the definition of Permitted Liens, provided that upon payment
in full or satisfaction of such Indebtedness, the equipment or property
theretofor subject to the Lien securing such Indebtedness shall immediately and
automatically become a part of the Collateral.

         5.02. Duration of Security Interest. Lenders' security interest in the
Collateral shall continue until the payment or prepayment in full and the
satisfaction of all Obligations, whereupon such security interest shall
terminate. Lenders, upon payment in full and the satisfaction of the
Obligations, shall execute, at Borrower's sole cost and expense, such further
documents and take such further actions as may be necessary to effect the
release and/or termination contemplated by this Section 5.02, including duly
executing and delivering termination statements for filing in all relevant
jurisdictions.

         5.03. Location and Possession of Collateral. The Collateral is and
shall remain in the possession of Borrower at Borrower's addresses listed in the
Disclosure Schedule or at such other locations as Borrower may from time to time
designate by fifteen (15) days prior written notice to Lender. So long as no
Event of Default has occurred and is continuing, Borrower shall remain in full
possession, enjoyment and control of the Collateral (except only as may be
otherwise required by Lenders for perfection of its security interest therein)
and to manage, operate and use the same and each part thereof with the rights
and franchises appertaining thereto; provided, however, that the possession,
enjoyment, control and use of the Collateral shall at all times be subject to
the observance and performance of the terms of this Agreement.

         5.04. Reserved.

         5.05. Lien Subordination. Lenders agree that the Liens granted to them
hereunder in Third Party Equipment (as defined below) shall be subordinate to
the Liens of (i) existing and future lenders providing equipment financing and
equipment lessors; provided, that such Liens are confined


                                      -20-
<PAGE>
solely to the equipment so financed and the proceeds thereof ("Third Party
Equipment") and provided such Liens secure Permitted Indebtedness; and provided,
further, that the Obligations hereunder shall not be subordinate in right of
payment to any obligations to any other lender, equipment lender or equipment
lessors and Lenders' rights and remedies hereunder shall not in any way be
subordinate to the rights and remedies of any such lender or equipment lessors.
Lenders agree to execute and deliver such agreements and documents as may be
reasonably requested by Borrower from time to time which set forth the lien
subordination described in this Section 5.05 and are reasonably acceptable to
Lenders. Lenders shall have no obligation to execute any agreement or document
which would impose obligations, restrictions or lien priority on Lenders which
are less favorable to Lenders than those described in this Section 5.05.

         5.06. Intellectual Property. (a) Borrower shall register or cause to be
registered with the United States Copyright Office (i) any software (material to
the business of Borrower) developed or acquired by Borrower in connection with
any product developed or acquired for sale or licensing. (b) While any
Obligations remain outstanding, Borrower shall register or cause to be
registered with the United States Copyright Office (i) any software (material to
the business of Borrower) developed or acquired by Borrower hereafter from time
to time in connection with any product developed or acquired for sale or
licensing and (ii) any major revisions or upgrades to any software that has
previously been registered with the United States Copyright Office. Borrower
shall file for registration within 30 days from the development or acquisition
of such software, major revision or upgrade. (c) While any Obligations remain
outstanding, Borrower shall promptly notify Lenders of the federal registration
or filing by such Borrower of any patent or patent application, or trademark or
trademark application, or copyright or copyright application, and shall promptly
execute and deliver to Lenders any grants of security interests in same, in form
acceptable to Lenders and consistent with the grants of security interest
executed and delivered simultaneously with this Agreement, to file with the
United States Patent and Trademark Office or the United States Copyright Office,
as applicable.

                                   ARTICLE VI
                              AFFIRMATIVE COVENANTS

         6.01. Affirmative Covenants.

         (a) Payment of Taxes, etc. Borrower and Guarantor shall pay and
discharge all taxes, assessments and governmental charges or levies imposed upon
them or upon their income or profits, or upon any properties belonging to them,
prior to the date on which penalties attach thereto, and all lawful claims
which, if unpaid, might become a Lien upon any of their properties; provided
that there shall be no requirement to pay any such tax, assessment, charge, levy
or claim (i) which is being contested in good faith and by appropriate
proceedings or which presents no risk of seizure, forfeiture, levy or other
event which could jeopardize any Collateral or (ii) for which payment in full is
bonded or reserved in Borrower's financial statements.

                                      -21-
<PAGE>
                  (b) Inspection Rights. Borrower and Guarantor shall, at any
reasonable time and from time to time (but provided no Event of Default shall
exist, no more than once per calendar quarter and only during Borrower's normal
business hours and upon reasonable notice), permit Lenders or any of its agents
or representatives to inspect the Collateral or Guarantor Collateral, to examine
and make copies of and abstracts from the records and books of account of, and
visit the properties of, Borrower and Guarantor and to discuss the affairs,
finances and accounts of Borrower and Guarantor with any of its officers or
directors relating in each case to Lenders' capacity as lenders and secured
party hereunder and under the Guarantor Security Agreement and with respect to
the Collateral and Guarantor Collateral.

                  (c) Maintenance of Equipment and Similar Assets. Borrower
shall keep and maintain all items of equipment and other similar types of
personal property that form any significant portion or portions of the
Collateral in good operating condition and repair and shall make all necessary
replacements thereof and renewals thereto so that the value and operating
efficiency thereof shall at all times be maintained and preserved. Borrower
shall not permit any such material item of Collateral to be operated or
maintained in violation of any applicable law, statute, rule or regulation. With
respect to items of leased equipment (to the extent Lenders have any security
interest in any residual Borrower's interest in such equipment under the lease),
Borrower shall keep, maintain, repair, replace and operate such leased equipment
in accordance with the terms of the applicable lease.

                  (d) Insurance. Borrower shall, obtain and maintain, at its own
expense, insurance of a type and with such limits as are carried by similarly
situated companies, including at a minimum:

                           (i) "All risk" insurance against loss or damage to
the Collateral. The coverage limit shall be determined to Lenders' reasonable
satisfaction. The deductible shall not exceed $25,000. The policy shall name
Lenders as loss payees with respect to the Collateral, shall not be invalidated
by any action of or breach of warranty by Borrower of any provision thereof and
waive subrogation against Lenders.

                           (ii) Commercial general liability insurance
(including contractual liability, products liability and completed operations
coverages) reasonably satisfactory to Lenders. The limit of liability shall be
at least $5,000,000 per occurrence. The policy shall be without deductible,
except for products liability coverage which may have a deductible up to
$25,000. The policy(ies) shall name Lenders as an additional insured in the full
amount of Borrower's liability coverage limits (or the coverage limits of any
successor to Borrower or such successor's parent which is providing coverage),
and contain cross liability and severability of interest clauses.

                           (iii) Such other insurance against risks of loss and
with terms as shall be reasonably required by Lenders.

All policies of insurance shall be placed with financially sound, commercial
insurers reasonably satisfactory to Lenders. All policies of insurance shall
provide that Lenders shall be given 30 days notice of cancellation of coverage.
On or prior to the first Funding Date and prior to each policy renewal, Borrower
shall furnish to Lenders certificates of insurance or other evidence
satisfactory to Lenders that insurance complying with all of the above
requirements is in effect.

                                      -22-
<PAGE>
                  (e) Further Assurances. At any time and from time to time
Borrower and/or Guarantor shall execute and deliver such further instruments and
take such further action as may reasonably be requested by Lenders to effect the
purposes of this Agreement.

                  (f) Equity Investment. Subject to the terms and conditions of
that certain Eighth Amended and Restated Investors Rights Agreement dated as of
June 1, 2001 by and among the Borrower and certain of its shareholders, as
amended and in effect from time to time, Borrower shall use reasonable efforts
to permit GV, at GV's option, to purchase in Borrower's next round of equity
financing up to $250,000; and VLL, at VLL's option, to purchase in Borrower's
next round of equity financing up to $250,000, of the securities sold in such
financing at the same price and on the same terms as paid and received by the
lead investor of the equity financing, and agrees that it shall provide each
Lender with thirty (30) days prior written notice of the proposed final closing
date thereof, which notice shall include the proposed terms, conditions and
pricing of the financing. This right of purchase may be assigned by: (i) a
Lender to one or more of the other Lenders or such Lender's designates listed in
clauses (ii) and (iii); (ii) GV to GV's affiliates (as that term is defined in
Regulation D promulgated under the Securities Act of 1933 ("Reg D"); and (iii)
VLL to VLL's affiliates (as that term is defined in Reg D).

                  (g) Managerial Assistance from VLL. Permit VLL to
substantially participate in, and substantially influence the conduct of
management of Borrower through the exercise of "management rights," as that term
is defined in 29 C.F.R. Section 2510.3-101(d), including without limitation the
following rights:

                           (i) Borrower agrees that (i) it will make management
available at such times as VLL may reasonably request for VLL to consult with
and advise as to the conduct of Borrower's business, its equipment and financing
plans, and its financial condition and prospects, and (ii) VLL shall have the
right to inspect Borrower's books, records, facilities and properties at
reasonable times during normal business hours on reasonable advance notice,
provided that access to highly confidential proprietary information and
facilities need not be provided.

                            (ii) VLL shall cooperate with Borrower to ensure
that the exercise of VLL's rights shall not disrupt the business of Borrower.
Notwithstanding the foregoing, Borrower and each Lender (other than VLL)
acknowledges and agrees that the provisions of this Section 6.01(g) do not
result in or confer upon any Lender other than VLL any managerial right or
control of Borrower, and the relationship of each Lender and the Borrower is and
shall remain solely as lender and borrower.

         The rights described in this Section 6.01(g) shall terminate and be of
no further force or effect upon the earliest to occur of (a) the closing of a
public offering of shares of the Borrower's capital stock pursuant to a
registration statement filed by the Borrower under the Securities Act of 1933
which has become effective (other than a registration statement relating solely
to employee benefit plans or a transaction covered by Rule 145), (b) such time
as the Borrower becomes required to file reports with the Securities and
Exchange Commission under Sections 12(g) or 15(d) of the Securities Exchange Act
of 1934, or (c) the earlier of (i) such time as the aggregate principal amount

                                      -23-
<PAGE>
outstanding under the Note originally issued to VLL shall be less than One
Million Dollars ($1,000,000) or (ii) the Loan Documents are no longer in full
force and effect.

                                  ARTICLE VII
                               NEGATIVE COVENANTS

         7.01. Negative Covenants. So long as the Obligations remain
outstanding, Borrower and Guarantor shall not:

                  (a) Name; Chief Executive Office. During the continuance of
this Agreement, change its name or chief executive office or principal place of
business without thirty (30) days prior written notice to Lenders.

                  (b) Collateral Control. Remove any items of Collateral from
Borrower's facility located at the addresses set forth on the cover page or the
Disclosure Schedule or such other addresses within the United States as Borrower
may from time to time designate by fifteen (15) days prior written notice to
Lender.

                  (c) Dispositions of Collateral. Convey, sell, offer to sell,
lease, transfer, exchange or otherwise dispose of (collectively, a "Transfer")
to any Person all or any part of the Collateral not constituting equipment
financed with the Transamerica Indebtedness or Existing Equipment Indebtedness
other than: (1) Transfers of inventory in the ordinary course of business; (2)
Transfers which would constitute Permitted Liens; or (3) Transfers of worn-out
or obsolete equipment.

                  (d) Liens on Collateral. Create, incur, assume or suffer to
exist any Lien of any kind upon any Collateral or Guarantor Collateral, whether
now owned or hereafter acquired, except Permitted Liens.

                  (e) Distributions. (i) Pay any dividends or make any
distributions on its Equity Securities; (ii) purchase, redeem, retire, defease
or otherwise acquire for value any of its Equity Securities (other than
repurchases by cancellation of indebtedness pursuant to the terms of employee
stock purchase plans, employee restricted stock agreements or similar
arrangements (a) in an aggregate amount not to exceed $100,000), or (b) where
Borrower may repurchase shares previously issued to employee(s) of Borrower
pursuant to Borrower's stock option plans, using the proceeds from such
issuance), (iii) return any capital to any holder of its Equity Securities as
such; (iv) make any distribution of assets, Equity Securities, obligations or
securities to any holder of its Equity Securities as such; or (v) set apart any
sum for any such purpose; provided, however, that Borrower may (A) pay dividends
payable solely in Common Stock and (B) convert any of its convertible securities
into other Equity Securities pursuant to the terms of such convertible
securities or otherwise in exchange therefor.

                                      -24-
<PAGE>
                  (f) Mergers or Acquisitions. Merge or consolidate with or into
any other Person or acquire all or substantially all of the capital stock or
assets of another Person without Lender's prior written consent, in Lenders'
sole discretion, provided that if Lenders refuse to provide their consent within
twenty (20) days of receiving a written request for consent, Borrower may prepay
the Loan without penalty.

                  (g) Transactions With Affiliates. Enter into any contractual
obligation with any affiliate or engage in any other transaction with any
affiliate except upon terms at least as favorable to Borrower as an arms-length
transaction with unaffiliated Persons.

                  (h) Maintenance of Accounts. Maintain any deposit accounts or
accounts holding securities except with respect to which Lenders take such
action as they deem necessary to obtain a perfected security interest in such
account, provided that, Borrower shall use commercially reasonable efforts to
deliver to Lenders account control agreement(s) for such accounts in a timely
fashion and in such forms as are reasonably acceptable to Lenders and Borrower.

                  (i) Indebtedness Payments. (i) Prepay, redeem, purchase,
defease or otherwise satisfy in any manner prior to the scheduled repayment
thereof any Indebtedness for borrowed money (other than amounts due or permitted
to be prepaid under this Agreement, the Comdisco Indebtedness or lease
obligations, including without limitation the Existing Equipment Indebtedness
and Transamerica Indebtedness, and if such Indebtedness constitutes lease
obligations, the Permitted Indebtedness permitted under subsection (b) of the
definition of Permitted Indebtedness), (ii) amend, modify or otherwise change
the terms of any Indebtedness for borrowed money or lease obligations so as to
accelerate the scheduled repayment thereof or (iii) repay any notes to officers,
directors or shareholders.

                  (j) Indebtedness. Create, incur, assume or permit to exist any
Indebtedness except Permitted Indebtedness.

                  (k) Investments. Make any Investment except for Permitted
Investments.

                  (l) Subsidiaries/Joint Ventures. Create any Subsidiaries or
enter into any joint ventures, or transfer, sell or assign any assets to any
Subsidiaries or joint ventures, without Lenders' prior written consent, provided
Lenders' prior written consent shall not be required if such actions are taken
with respect to the Elan Joint Venture in accordance with the Elan Joint Venture
Agreements.

                                  ARTICLE VIII
                              CONDITIONS PRECEDENT

         8.01. Closing. At the time of execution and delivery of this Agreement,
Borrower and Guarantor shall have duly executed and/or delivered to Lenders the
items set forth in Part I of Schedule 3.

                                      -25-
<PAGE>
         8.02. Other Conditions. The obligation of the Lenders to make the Loans
shall be subject to the execution and/or delivery to such Lenders of each of the
items set forth in Part I of Schedule 3 and the satisfaction by Borrower and
Guarantor of each condition set forth in Part II of Schedule 3.

         8.03. Covenant to Deliver. Borrower and Guarantor agree (not as a
condition but as a covenant) to deliver to Lenders each item required to be
delivered to Lenders as a condition to a Loan, if the Loan is advanced. Borrower
and Guarantor expressly agree that the extension of any Loan prior to the
receipt by Lenders of any such item shall not constitute a waiver by Lenders of
Borrower's or Guarantor's obligation to deliver such item.

                                   ARTICLE IX
                              DEFAULT AND REMEDIES

         9.01. Events of Default. An "Event of Default" shall mean the
occurrence of one or more of the following described events:

                  (a) Borrower shall (i) default in the payment of principal of
or interest on any Loan when the same is due, or (ii) default in the payment of
any expense or other amount payable hereunder or thereunder for five (5) days
after receipt of written notice from a Lender that the same is due; or

                  (b) Borrower shall breach any provision of Section 6.01(d) or
Section 7.01; or

                  (c) Borrower shall default in the performance of any covenant,
agreement or obligation (other than a covenant, agreement or obligation referred
to in, Section 9.01(a) or Section 9.01(b)) contained in any Operative Document
(other than the Warrants) and Borrower shall fail to cure within thirty (30)
days after the occurrence of any such default; or

                  (d) Borrower shall have materially breached the terms of any
of the Warrants; or

                  (e) Any representation or warranty made herein or on the
Funding Date by Borrower in any Operative Document, or any certificate or
financial statement furnished pursuant to the provisions of any Operative
Document, shall prove to have been false or misleading in any material respect
as of the time made or furnished; or

                  (f) Any Operative Document shall in any material respect cease
to be, or Borrower or Guarantor shall assert that any Operative Document is not,
a legal, valid and binding obligation of Borrower or Guarantor enforceable in
accordance with its terms; or

                  (g) Defaults shall exist under any agreements of Borrower or
Guarantor which consist of the failure to pay any Indebtedness of Borrower or
Guarantor in an aggregate amount in excess of One Hundred Thousand Dollars
($100,000)at maturity or which result in a right by such third party or parties,
whether or not exercised, to accelerate the maturity of Indebtedness of Borrower
or Guarantor in an aggregate amount in excess of One Hundred Thousand Dollars
($100,000) or a default shall exist under any financing agreement with a Lender
or any of such Lender's affiliates; or

                                      -26-
<PAGE>
                  (h) A proceeding shall have been instituted in a court of
competent jurisdiction seeking a decree or order for relief in respect of
Borrower or Guarantor in an involuntary case under any applicable bankruptcy,
insolvency or other similar law now or hereafter in effect, or for the
appointment of a receiver, liquidator, assignee, custodian, trustee (or similar
official) of Borrower or guarantor or for any substantial part of their
property, or for the winding-up or liquidation of their affairs, and such
proceeding shall remain undismissed or unstayed and in effect for a period of
sixty (60) consecutive days or such court shall enter a decree or order granting
the relief sought in such proceeding; or

                  (i) Borrower or Guarantor shall commence a voluntary case
under any applicable bankruptcy, insolvency or other similar law now or
hereafter in effect, shall consent to the entry of an order for relief in an
involuntary case under any such law, or shall consent to the appointment of or
taking possession by a receiver, liquidator, assignee, trustee, custodian (or
other similar official) of Borrower or Guarantor or for any substantial part of
their property, or shall make a general assignment for the benefit of creditors,
or shall fail generally to pay their debts as they become due, or shall take any
corporate action in furtherance of any of the foregoing; or

                  (j) If a judgment or judgments for the payment of money in an
amount, individually or in the aggregate, of at least One Hundred Thousand
Dollars ($100,000) shall be rendered against Borrower or Guarantor and shall
remain unsatisfied and unstayed for a period of thirty (30) days; or

                  (k) If the Borrower has less than $5,000,000 in cash or cash
equivalents and there occurs a material adverse change in Borrower's business
provided, in determining whether a material adverse change has occurred in
Borrower's business, the Lenders shall examine (i) the status of Borrower's
current and future partnering activities, including, without limitation, the
Elan Joint Venture, (ii) the status and prospects of Borrower's equity raising,
and (iii) the status of Borrower's product development; or

                  (l) If any material portion of Borrower's or Guarantor's
assets is attached, seized, subjected to writ or distress warrant, or is levied
upon, or comes into possession of any trustee, receiver or Person acting in a
similar capacity and such attachment, seizure, writ or distress warrant or levy
has not been removed, discharged or rescinded within thirty (30) days, or if
Borrower or Guarantor is enjoined, restrained, or in any way prevented by court
order from continuing to conduct all or any material part of its business
affairs, or if a judgment or other claim becomes a lien or encumbrance upon any
material portion of Borrower's or Guarantor's assets, or if a notice of lien,
levy, or assessment is filed of record with respect to any of Borrower's or
Guarantor's assets by the United States Government, or any department, agency,
or instrumentality thereof, or by any state, county, municipal, or governmental
agency, and the same is not paid within thirty (30) days after Borrower or
Guarantor receives notice thereof, provided that none of the foregoing shall
constitute an Event of Default where such action or event is stayed or an
adequate bond has been posted pending a good faith contesting by Borrower or
Guarantor.

         9.02. Consequences of Event of Default.

                                      -27-
<PAGE>
                  (a) If an Event of Default specified under any of clauses (a)
through (g) or (j) through (l) of Section 9.01 shall occur and be continuing,
Lender may (i) declare all of the Loans, and all other liabilities of Borrower
and Guarantor hereunder and under the other Operative Documents to be
immediately due and payable without presentment, demand, protest or further
notice of any kind, all of which are hereby expressly waived, and (ii) terminate
any commitment to make the Loan and terminate any commitment to advance money or
extend credit to or for the benefit of Borrowers pursuant to any other agreement
or commitment extended by Lender to Borrowers.

                  (b) If an Event of Default specified under clause (h) or (i)
of Section 9.01 shall occur, then immediately and without notice (i) all of the
Loans, and all other liabilities of Borrower and Guarantor hereunder and under
the other Operative Documents to be immediately due and payable without
presentment, demand, protest or notice of any kind, all of which are hereby
expressly waived, and (ii) Lender's commitments hereunder to make any Loan and
any other commitment of Lender to Borrowers to advance money or extend credit
pursuant to any other agreement or commitment shall be terminated.

         9.03. Rights Regarding Collateral. Borrower agrees that when any Event
of Default has occurred and is continuing, Lenders shall have the rights,
options, duties and remedies of a secured party as permitted by law and, in
addition to and without limiting the foregoing, Lenders may exercise any one or
more or all, and in any order, of the remedies herein set forth, in accordance
with applicable law, including the following:


                                      -28-
<PAGE>


            (a) Lenders, personally or by agents or attorneys, shall have the
right (subject to compliance with any applicable mandatory legal requirements)
to require Borrower to assemble the Collateral and make it available to Lenders
at a place to be designated by Lenders and reasonably convenient to both Lenders
and Borrower or to take immediate possession of the Collateral, or any portion
thereof, and for that purpose may pursue the same wherever it may be found, and
may peaceably enter any of premises of Borrower, with or without notice, demand,
process of law or legal procedure, to the extent permitted by applicable law,
and search for, take possession of, remove, keep and store the same, or use and
operate or lease the same until sold. In furtherance of Lenders' rights
hereunder, Borrower hereby grants to Lenders an irrevocable, non-exclusive
license (exercisable without royalty or other payment by Lenders) to use,
license or sublicense any patent, trademark, trade name, copyright or other
intellectual property in which Borrower now or hereafter has any right, title or
interest together with the right of access to all media in which any of the
foregoing may be recorded or stored; provided, however, that such license shall
only be exercisable in connection with the disposition of Collateral upon
Lenders' exercise of their remedies hereunder. Lenders may make such payments
and do such acts as Lenders consider necessary or reasonable to protect Lenders'
security interest in the Collateral. Borrower agrees to assemble the Collateral
if Lenders so require, and to make the Collateral available to Lenders at such
location as Lenders may designate and which is mutually convenient to both
Lenders and Borrower. Borrower authorizes Lenders to peaceably enter the
premises where the Collateral is located, to take and maintain possession of the
Collateral, or any part of it, and to pay, purchase, contest, or compromise any
encumbrance, charge, or lien which in Lenders' determination appears to be prior
or superior to their security interest and to pay all expenses incurred in
connection therewith. With respect to any of Borrower's owned premises, Borrower
hereby grants Lenders, a license to peaceably enter into possession of such
premises and to occupy the same, without charge, for up to one hundred twenty
(120) days in order to exercise any of Lenders' rights or remedies provided
herein, at law, in equity, or otherwise;

            (b) Lenders may, if at the time such action may be lawful and always
subject to compliance with any mandatory legal requirements, either with or
without taking possession and either before or after taking possession, without
instituting any legal proceedings whatsoever, having first given notice of such
sale by registered or certified mail to Borrower once at least ten (10) days
prior to the date of such sale, and having first given any other notice which
may be required by law, sell and dispose of the Collateral, or any part thereof,
at a private sale or at public auction, to the highest bidder, in one lot as an
entirety or in separate lots, and either for cash or on credit and on such terms
as Lenders may determine, and at any place (whether or not it be the location of
the Collateral or any part thereof) designated in the notice referred to above.
To the extent permitted by applicable law, any such sale or sales may be
adjourned from time to time by announcement at the time and place appointed for
such sale or sales, or for any such adjourned sale or sales, without further
published notice, and Borrower, Lenders or the holder or holders of the Notes,
or of any interest therein, may bid and become the purchaser at any such sale.


                                      -29-
<PAGE>
            (c) Lenders may proceed to protect and enforce this Agreement and
the other Operative Documents by suit or suits or proceedings in equity, at law
or in bankruptcy, and whether for the specific performance of any covenant or
agreement herein contained or in execution or aid of any power herein granted;
or for foreclosure hereunder, or for the appointment of a receiver or receivers
for any real property security or any part thereof, or for the recovery of
judgment for the Obligations or for the enforcement of any other proper, legal
or equitable remedy available under applicable law.

      9.04. Waiver by Borrower. Upon the occurrence and during the continuance
of an Event of Default, to the extent permitted by law, Borrower covenants that
it will not at any time insist upon or plead, or in any manner whatsoever claim
or take any benefit or advantage of, any stay or extension law now or at any
time hereafter in force, nor claim, take nor insist upon any benefit or
advantage of or from any law now or hereafter in force providing for the
valuation or appraisement of the Collateral or any part thereof prior to any
sale or sales thereof to be made pursuant to any provision herein contained, or
to the decree, judgment or order of any court of competent jurisdiction; nor,
after such sale or sales, claim or exercise any right under any statute now or
hereafter made or enacted by any state or otherwise to redeem the property so
sold or any part thereof, and, to the full extent legally permitted, except as
to rights expressly provided herein, hereby expressly waives for itself and on
behalf of each and every Person, except decree or judgment creditors of
Borrower, acquiring any interest in or title to the Collateral or any part
thereof subsequent to the date of this Agreement, all benefit and advantage of
any such law or laws, and covenants that it will not invoke or utilize any such
law or laws or otherwise hinder, delay or impede the execution of any power
herein granted and delegated to Lenders, but will suffer and permit the
execution of every such power as though no such power, law or laws had been made
or enacted.

      9.05. Set Off Right. During the occurrence and continuance of an Event of
Default, Lenders may set off and apply to the Obligations any and all
indebtedness at any time owing to or for the credit or the account of Borrower.

      9.06. Effect of Sale. Any sale, whether under any power of sale available
to Lenders or by virtue of judicial proceedings, shall operate to divest all
right, title, interest, claim and demand whatsoever, either at law or in equity,
of Borrower in and to the property sold, and shall be a perpetual bar, both at
law and in equity, against Borrower, its successors and assigns, and against any
and all persons claiming the property sold or any part thereof under, by or
through Borrower, its successors or assigns.

      9.07. Application of Collateral Proceeds. The proceeds and/or avails of
the Collateral and Guarantor Collateral, or any part thereof, and the proceeds
and the avails of any remedy hereunder or under the Guarantor Security Agreement
(as well as any other amounts of any kind held by Lenders at the time of, or
received by Lenders after, the occurrence of an Event of Default hereunder)
shall be paid to and applied as follows:


                                      -30-
<PAGE>
            (a) First, to the payment of reasonable costs and expenses,
including all amounts expended to preserve the value of the Collateral or
Guarantor Collateral, of foreclosure or suit, if any, and of such sale and the
exercise of any other rights or remedies, and of all proper fees, expenses,
liability and advances, including reasonable legal expenses and attorneys' fees,
incurred or made hereunder or under the Guarantor Security Agreement by Lenders;

            (b) Second, to the payment to Lenders of the amount then owing or
unpaid on the Notes, and in case such proceeds shall be insufficient to pay in
full the whole amount so due, owing or unpaid upon the Notes, then first, to the
unpaid interest thereon, second, to unpaid principal thereof and third to the
remaining balance of the Obligations under the Notes; such application to be
made upon presentation of the Notes, and the notation thereon of the payment, if
partially paid, or the surrender and cancellation thereof, if fully paid;

            (c) Third, to the payment of other amounts then payable to Lenders
under any of the Operative Documents; and

            (d) Fourth, to the payment of the surplus, if any, to Borrower, its
successors and assigns, or to whomsoever may be lawfully entitled to receive the
same.

      9.08. Reinstatement of Rights. If Lenders shall have proceeded to enforce
any right under this Agreement or any other Operative Document by foreclosure,
sale, entry or otherwise, and such proceedings shall have been discontinued or
abandoned for any reason or shall have been determined adversely, then and in
every such case (unless otherwise ordered by a court of competent jurisdiction),
Lenders shall be restored to their former position and rights hereunder with
respect to the property subject to the security interest created under this
Agreement.


                                    ARTICLE X

                                  MISCELLANEOUS

      10.01. Modifications, Amendments or Waivers. The provisions of any
Operative Document may be modified, amended or waived only by a written
instrument signed by each of the parties thereto. Each Lender agrees that if the
assignee of any Lender is a creditor of such Lender to whom such Lender has
granted a security interest in this Agreement, then following the occurrence of
an event of default (however defined) under or with respect to the indebtedness
held by such assignee or the occurrence of an event which with the giving of
notice or the passage of time or both would constitute such an event of default,
the written consent of such assignee, rather than of such assignor Lender, shall
be required for any modification or amendment to this Agreement.

      10.02. No Implied Waivers; Cumulative Remedies; Writing Required. No delay
or failure of Lenders in exercising any right, power or remedy hereunder shall
affect or operate as a waiver thereof; nor shall any single or partial exercise
thereof or any abandonment or discontinuance of steps to enforce such a right,
power or remedy preclude any further exercise thereof or of any other right,
power or remedy. The rights and remedies hereunder of Lenders are cumulative and
not exclusive of any rights or remedies which it would otherwise have. Any
waiver, permit, consent or approval of any kind or character on the part of
Lenders of any breach or default under this


                                      -31-
<PAGE>
Agreement or any such waiver of any provision or condition of this Agreement
must be in writing and shall be effective only in the specified instance and to
the extent specifically set forth in such writing.

      10.03. Indemnification and Waiver. Whether or not the transactions
contemplated hereby shall be consummated:

            (a) General Indemnity. Borrower and Guarantor shall pay, indemnify,
and hold each Lender and each of their respective officers, directors,
employees, counsel, partners, agents and attorneys-in-fact (each, an
"Indemnified Person") harmless from and against any and all liabilities,
obligations, losses, damages, penalties, actions, judgments, suits, costs,
charges, expenses or disbursements (including Lenders' Expenses and reasonable
attorney's fees and the allocated cost of in-house counsel) of any kind or
nature whatsoever with respect to the execution, delivery, enforcement,
performance and administration of this Agreement and any other Operative
Documents, or the transactions contemplated hereby and thereby, and with respect
to any investigation, litigation or proceeding (including any case, action or
proceeding before any court or other Governmental Authority relating to
bankruptcy, reorganization, insolvency, liquidation, dissolution or relief of
debtors or any appellate proceeding) related to this Agreement or the Loans or
the use of the proceeds thereof, whether or not any Indemnified Person is a
party thereto (all the foregoing, collectively, the "Indemnified Liabilities");
provided, that neither Borrower nor Guarantor shall have any obligation
hereunder to any Indemnified Person with respect to Indemnified Liabilities
arising from the gross negligence or willful misconduct of such Indemnified
Person or breach of this Agreement or any other Operative Document.

            (b) Environmental Indemnity. Borrower hereby agrees to indemnify,
defend and hold harmless each Indemnified Person, from and against any and all
liabilities, obligations, losses, damages, penalties, actions, judgments, suits,
costs, charges, expenses or disbursements (including reasonable attorneys' fees
and the allocated cost of in-house counsel and internal environmental audit or
review services), which may be incurred by or asserted against such Indemnified
Person in connection with or arising out of any pending or threatened
investigation, litigation or proceeding, or any action taken by any Person, with
respect to any Environmental Claim arising out of or related to any Property
owned, leased or operated by Borrower. No action taken by legal counsel chosen
by any Lender or Agent in defending against any such investigation, litigation
or proceeding or requested remedial, removal or response action (except for
actions which constitute fraud, willful misconduct, gross negligence or material
violations of law) shall vitiate or in any way impair Borrower's obligation and
duty hereunder to indemnify and hold harmless each Lender and Agent. Lenders and
Agent agree to use reasonable efforts to cooperate with Borrower respecting the
defense of any matter indemnified hereunder, except insofar as and to the extent
that their respective interests may be adverse to Borrower's, in each Lenders'
reasonable discretion.

      10.04. Waivers. NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS
AGREEMENT OR ANYWHERE ELSE, EACH OF LENDERS, BORROWER AND GUARANTOR AGREE THAT
IT SHALL NOT SEEK FROM ANY PARTY TO THIS AGREEMENT UNDER ANY THEORY OF LIABILITY
(INCLUDING ANY THEORY IN TORTS), ANY SPECIAL, INDIRECT, CONSEQUENTIAL OR
PUNITIVE DAMAGES,


                                      -32-
<PAGE>
PROVIDED, HOWEVER, THIS WAIVER SHALL NOT BE DEEMED TO LIMIT THE BORROWER'S
INDEMNITY AND LENDERS' RIGHTS UNDER SECTIONS 10.03 AND 10.15 HEREOF.

      10.05. Notices; Payments. Unless otherwise provided in this Agreement, all
notices or demands by any party relating to this Agreement or any other
agreement entered into in connection herewith shall be in writing and (except
for financial statements and other informational documents which may be sent by
first-class mail, postage prepaid) shall be personally delivered or sent by
certified mail, postage prepaid, return receipt requested, or by prepaid
facsimile to Borrower or to Lenders, as the case may be, at their respective
addresses set forth below:

      If to Borrower/Guarantor: ACUSPHERE, INC.
                                38 Sidney Street
                                Cambridge, MA 02139
                                Attention: Sherri C. Oberg
                                Fax: (781) 674-0174
                                PH: (617) 577-8800

                                With a copy to:

                                Testa, Hurwitz & Thibeault, LLP
                                125 High Street
                                Boston, MA 02110
                                Attention: Lawrence S. Wittenberg, Esq.
                                Fax: (617) 248-7100
                                PH: (617) 248-7000

      If to GV:                 GATX Ventures, Inc.
                                3687 Mount Diablo Blvd., Suite 200
                                Lafayette, CA 94549
                                Attention: Contract Administration
                                Fax: (925) 258-6020
                                PH: (925) 258-6000

                                With a copy to:

                                GATX Ventures, Inc.
                                16 Munson Road, 5th Floor
                                Farmington, CT 06032
                                Attention: Contract Administration
                                Fax: (860) 284-4350
                                PH: (860) 284-4314


                                      -33-
<PAGE>
      If to VLL                 Venture Lending & Leasing III, Inc.
                                2010 North First Street, Suite 310
                                San Jose, CA  95131
                                Attention: Maurice Werdegar
                                Fax: (408) 436-8625
                                PH: (408) 436-8577 (ext. 23)


      The parties hereto may change the address at which they are to receive
notices hereunder, by notice in writing in the foregoing manner given to the
other.

      10.06. Termination. This Agreement shall terminate at the end of the Term;
provided, however, that the termination of this Agreement shall not affect any
of the rights and remedies of Lenders hereunder, it being understood and agreed
that all such rights and remedies shall continue in full force and effect until
payment of all amounts owed to Lenders under or in connection with the Operative
Documents, whether on account of principal, interest, fees or otherwise.

      10.07. Severability. If any provision of any Operative Document is held
invalid or unenforceable to any extent or in any application, the remainder of
such Operative Document and all other Operative Documents, or the application of
such provision to different Persons or circumstances or in different
jurisdictions, shall not be affected thereby.

      10.08. Survival. All covenants, representations and warranties made in
this Agreement shall continue in full force and effect so long as any
Obligations remain outstanding. The obligations of Borrower and Guarantor to
indemnify Lenders with respect to the expenses, damages, losses, costs and
liabilities described in Section 10.03 shall survive until all applicable
statute of limitations periods with respect to actions that may be brought
against Lenders have run.

      10.09. Relationship of Parties. Borrower, Guarantor and each Lender
acknowledge, understand and agree that the relationship between the Borrower and
Guarantor, on the one hand, and Lenders, on the other, is, and at all time shall
remain that of a borrower, guarantor and lenders. Lenders shall not under any
circumstances be construed to be partners or joint venturers of Borrower,
Guarantor or any of their Affiliates; nor shall Lenders under any circumstances
be deemed to be in a relationship of confidence or trust or a fiduciary
relationship with Borrower, Guarantor or any of their Affiliates, or to owe any
fiduciary duty to Borrower, Guarantor or any of their Affiliates. Lenders do not
undertake or assume any responsibility or duty to Borrower, Guarantor or any of
their Affiliates to select, review, inspect, supervise, pass judgment upon or
otherwise inform the Borrower, Guarantor or any of their Affiliates of any
matter in connection with its or their Property, any Collateral or Guarantor
Collateral held by any Lender or the operations of Borrower, Guarantor or any of
their Affiliates. Borrower, Guarantor and each of their Affiliates shall rely
entirely on their own judgment with respect to such matters, and any review,
inspection, supervision, exercise of judgment or supply of information
undertaken or assumed by any Lender in connection with such


                                      -34-
<PAGE>
matters is solely for the protection of Lenders and Borrower, Guarantor and
their Affiliates are not entitled to rely thereon.

      10.10. Successors and Assigns. This Agreement and the other Operative
Documents shall be binding upon and inure to the benefit of Lenders, all future
holders of the Notes, Borrower, Guarantor and their respective successors and
permitted assigns, except that Borrower and Guarantor may not assign or transfer
their respective rights hereunder or any interest herein without the prior
written consent of Lenders and Lenders may not assign the rights conferred
pursuant to Section 6.01(f) except in accordance with the terms thereof. Each
Lender may sell to any other financial entity (a "Participant") participation
interests in Lender's rights under this Agreement and the other Operative
Documents; provided that notwithstanding the sale of participations, such Lender
shall remain solely responsible for the performance of its obligations under
this Agreement, such Lenders shall remain the holder of its Note for all
purposes under this Agreement and Borrower shall continue to deal solely and
directly with such Lender in connection with this Agreement and the other
Operative Documents. Lenders may disclose the Operative Documents and any other
financial or other information relating to Borrower or any Subsidiary to any
potential Participant, provided that such Participant agrees to protect the
confidentiality of such documents and information on terms substantially similar
to the terms in Section 10.15. In connection with any of the foregoing, Lenders
may disclose all documents and information that Lenders now or hereafter may
have relating to the Loans, Borrower, Guarantor or their business; provided that
any person who receives such information shall have agreed in writing in advance
to maintain the confidentiality of such information on terms reasonably
acceptable to Borrower. Borrower and Guarantor acknowledge that any Lender may
grant a security interest in such Lender's rights under this Agreement and the
other Loan Documents in connection with such Lender's own financing
arrangements. Borrower and Guarantor agree not to assert against any such
collateral assignee of such Lender any counterclaim, offset or dispute Borrower
or Guarantor may have against such Lender. Each Lender agrees that if the
assignee of any Lender is a creditor of such Lender to whom such Lender has
granted a security interest in this Agreement, then following the occurrence of
an event of default (however defined) under or with respect to the indebtedness
held by such assignee or the occurrence of an event which with the giving of
notice or the passage of time or both would constitute such an event of default,
all rights (but not the obligations) of the assignor Lender under this Agreement
shall thereafter be exercisable solely by such assignee except to the extent
such assignee may otherwise consent in writing. It is the intention of the
parties that as a "venture capital operating company," Venture Lending & Leasing
III, LLC ("LLC"), the parent and sole owner of VLL, shall have the benefit of,
and the power to exercise independent of any other Lender, those "management
rights" provided in Section 6.01 (g). To that end, the references to "VLL" or
"Lender" in Sections 2.01(d), and 6.01(g) hereof shall include LLC, and LLC
shall have the right to exercise the advisory, inspection, information and other
rights given to a lender under those Sections independently of any Lender.

      10.11. No Set-Offs by Borrower. All sums payable by Borrower or pursuant
to this Agreement or any of the other Operative Documents shall be payable
without notice or demand and shall be payable in United States Dollars without
set-off or reduction of any manner whatsoever.


                                      -35-
<PAGE>
      10.12. Counterparts. This Agreement may be executed in any number of
counterparts and by different parties hereto on separate counterparts, each of
which, when so executed and delivered, shall be an original, but all such
counterparts shall together constitute one and the same instrument.

      10.13. Further Assurances. Borrower and Guarantor will, at their own
expense, from time to time do, execute, acknowledge and deliver all further
acts, deeds, conveyances, transfers and assurances, and all financing and
continuation statements and similar notices, reasonably necessary or proper for
the perfection of the security interest being herein, or in the Guarantor
Security Agreement, provided for in the Collateral and Guarantor Collateral,
whether now owned or hereafter acquired.

      10.14. Power of Attorney in Respect of the Collateral. Borrower and
Guarantor do hereby irrevocably appoint Lenders (which appointment is coupled
with an interest), the true and lawful attorney-in-fact of Borrower or Guarantor
with full power of substitution, for it and in its name (a) to perform (but
Lenders shall not be obligated to and shall incur no liability to Borrower or
any third party for failure to perform) any act which Borrower or Guarantor is
obligated by this Agreement or the Operative Documents to perform, (b) to ask,
demand, collect, receive, receipt for, sue for, compound and give acquittance
for any and all rents, issues, profits, avails, distributions, income, payment
draws and other sums in which a security interest is granted under Section 5.01
with full power to settle, adjust or compromise any claim thereunder as fully as
if Lenders were Borrower itself, (c) to receive payment of and to endorse the
name of Borrower to any items of Collateral (including checks, drafts and other
orders for the payment of money) that come into Lenders' possession or under
Lenders' control, (d) to make all demands, consents and waivers, or take any
other action with respect to, the Collateral, (e) in Lenders' discretion, to
file any claim or take any other action or institute proceedings, either in its
own name or in the name of Borrower or otherwise, which Lenders may reasonably
deem necessary or appropriate to protect and preserve the right, title and
interest of Lenders in and to the Collateral, and (f) to otherwise act with
respect thereto as though Lenders were the outright owner of the Collateral;
provided, however, that the power of attorney herein granted shall be
exercisable only upon the occurrence and during the continuation of an Event of
Default unless in Lenders' reasonable opinion immediate action is necessary to
maintain adequate insurance on the Collateral. Borrower agrees to reimburse
Lenders upon demand for all reasonable costs and expenses, including attorneys'
fees and expenses, which Lenders may reasonably incur while acting as Borrower's
attorney in fact hereunder, all of which costs and expenses are included within
the Obligations.

      10.15. Confidentiality. All information (other than periodic reports filed
by Borrower with the Securities and Exchange Commission) disclosed by Borrower
or Guarantor to Lenders in writing or through inspection pursuant to this
Agreement shall be considered confidential. Lenders agree to use the same degree
of care to safeguard and prevent disclosure of such confidential information as
Lenders uses with its own confidential information, but in any event no less
than a reasonable degree of care. Lenders shall not disclose such information to
any third party (other than Lenders' or Lenders' partner's attorneys and
auditors subject to the same confidentiality obligation set forth herein) and
shall use such information only for purposes of evaluation of its investment in
Borrower and the exercise of Lenders' rights and the enforcement of their
remedies under this Agreement and the other Operative Documents. The obligations
of confidentiality shall not apply to any information


                                      -36-
<PAGE>
that (a) was known to the public prior to disclosure by Borrower or Guarantor
under this Agreement, (b) becomes known to the public through no fault of
Lenders, (c) is disclosed to Lenders by a third party having a legal right to
make such disclosure, or (d) is independently developed by Lenders.
Notwithstanding the foregoing, Lenders' agreement of confidentiality shall not
apply if any Lender has acquired indefeasible title to any Collateral or
Guarantor Collateral or in connection with any enforcement or exercise of
Lenders' rights and remedies under this Agreement or the Guarantor Security
Agreement following an Event of Default, including the enforcement of Lenders'
security interest in the Collateral or Guarantor Collateral.

      10.16. CHOICE OF LAW AND VENUE; JURY TRIAL WAIVER. THIS AGREEMENT SHALL BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF
CALIFORNIA, WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW. EACH OF BORROWER,
GUARANTOR AND LENDERS HEREBY SUBMITS TO THE NON-EXCLUSIVE JURISDICTION OF THE
STATE AND FEDERAL COURTS LOCATED IN THE NORTHERN DISTRICT OF CALIFORNIA.
BORROWER, GUARANTOR AND LENDERS HEREBY WAIVE THEIR RESPECTIVE RIGHTS TO A JURY
TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF ANY OF THE
OPERATIVE DOCUMENTS OR ANY OF THE TRANSACTIONS CONTEMPLATED THEREIN, INCLUDING
CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW OR
STATUTORY CLAIMS.


                                      -37-
<PAGE>
      IN WITNESS WHEREOF, the parties hereto, by their officers thereunto duly
authorized, have executed this Agreement as of the day and year first above
written.

                                          ACUSPHERE, INC.


                                          By: /s/ Sherri Oberg
                                              ----------------------------------

                                          Name: Sherri C. Oberg

                                          Title: President


                                          GUARANTOR:

                                          ACUSPHERE SECURITIES CORPORATION


                                          By: /s/ Sherri C. Oberg
                                              ----------------------------------

                                          Name: Sherri C. Oberg

                                          Title: President


                                          LENDERS:

                                          GATX VENTURES, INC.


                                          By: /s/ Robert D. Pomeroy, Jr.
                                              ----------------------------------

                                          Name: Robert D. Pomeroy, Jr.

                                          Title: Senior Vice President


                                          VENTURE LENDING & LEASING III, INC.


                                          By: /s/ Salvador O. Gutierrez
                                              ----------------------------------

                                          Name: Salvador O. Gutierrez

                                          Title: President
<PAGE>
      SCHEDULES

            1     Funding Certificate
            2     Disclosure Schedule
            3     Conditions Precedent

      EXHIBITS

            A     Form of Secured Promissory Notes
            B     Form of Warrant
            C     Form of Opinion of Counsel
<PAGE>
                                   SCHEDULE 1

                               FUNDING CERTIFICATE

      The undersigned, being the duly elected and acting President and Chief
Executive Officer of ACUSPHERE, INC., a Delaware corporation ("Borrower"), does
hereby certify to the Lenders (as defined in the Loan Agreement defined below)
in connection with that certain Venture Loan and Security Agreement dated as of
September 27, 2001, among Borrower and certain Lenders named therein (the "Loan
Agreement"; with other capitalized terms used below having the meanings ascribed
thereto in the Loan Agreement) that:


      1.    The representations and warranties made by Borrower in Article III
            of the Loan Agreement and in the other Operative Documents are true
            and correct as of the date hereof.

      2.    No event or condition has occurred and is continuing that would
            constitute a Default or an Event of Default under the Loan Agreement
            or any other Operative Document.

      3.    Borrower is in compliance with the covenants and requirements
            contained in Articles IV, V, VI and VII of the Loan Agreement.

      4.    All conditions referred to in Article VIII of the Loan Agreement to
            the making of the Loan to be made on or about the date hereof have
            been satisfied.

      5.    No material adverse change in the general affairs, management,
            results of operations, condition (financial or otherwise) or
            prospects of Borrower, whether or not arising from transactions in
            the ordinary course of business, has occurred since September 27,
            2001.

Dated: September 27, 2001
                                          ACUSPHERE, INC.

                                          By: /s/ Sherri C. Oberg
                                              ----------------------------------

                                          Name: Sherri C. Oberg

                                          Title: President and CEO
<PAGE>
                                   SCHEDULE 2

                               DISCLOSURE SCHEDULE


                                   SCHEDULE 3

                              CONDITIONS PRECEDENT

      PART I:

      At the time of execution and delivery of this Agreement, there shall also
have been duly executed and delivered to Lenders:

      (a)   The Loan Agreement and the Warrants executed in favor of Lenders and
            Persons specified by Lenders which are exercisable for shares of
            Borrower's preferred stock;

      (b)   The Guaranty and Guarantor Security Agreement executed in favor of
            Lenders;

      (c)   The Intercreditor Agreement, in form and substance satisfactory to
            Lenders and duly executed by Lenders;

      (d)   A favorable opinion of counsel for Borrower, dated as of the closing
            date, in such other form or forms as Lenders may accept;

      (e)   Copies, certified by the Secretary, Assistant Secretary or Chief
            Financial Officer of each of Borrower and Guarantor as of the
            closing date, of each of their respective charter documents and
            bylaws and of all documents evidencing corporate action taken by
            each of them authorizing the execution, delivery and performance of
            the Operative Documents to which each is a party and containing
            incumbency and representative signatures, in form and substance
            satisfactory to Lenders and their counsel;

      (f)   Good standing certificates from each of Borrower's and Guarantor's
            respective states of incorporation and the state in which Borrower's
            principal place of business is located, together with certificates
            of the applicable governmental authorities that Guarantor and
            Borrower are in compliance with the franchise tax laws of each such
            state, each dated as of a recent date;

      (g)   Evidence of the insurance coverage required by Section 6.01(d) of
            this Agreement;

      (h)   All necessary consents of shareholders and other third parties with
            respect to the execution, delivery and performance of this
            Agreement, the Warrants, the Notes and the other Operative
            Documents;

      (i)   Form UCC-1 Financing Statements, duly executed by Borrower, or other
            documents, and Borrower shall have taken such actions, if any, as
            Lenders shall reasonably determine are necessary or desirable to
            perfect and protect its security interest in the Collateral;
<PAGE>
      (j)   Grants of security interest in federally-registered Intellectual
            Property;

      (k)   Evidence of not less than $14,000,000 in cash or cash equivalents in
            Borrower's deposit and or investment accounts; and

      (l)   All other documents as Lenders shall have reasonably requested.

      PART II

      On or prior to the Funding Date of the Loans, each of the items set forth
in Part I of this Schedule 3 shall have been delivered to such Lenders and the
following conditions shall have been satisfied or waived by such Lenders:

      (a)   Borrower shall have provided to Lenders such documents, instruments
            and agreements as Lenders shall reasonably request to evidence the
            perfection and priority of the security interests granted to Lenders
            pursuant to Article V;

      (b)   Guarantor shall have provided to Lenders such documents, instruments
            and agreements as Lenders shall reasonably request to evidence the
            perfection and priority of the security interests granted to Lenders
            pursuant to the Guarantor Security Agreement;

      (c)   Form UCC-1 Financing Statements, duly executed by Guarantor, or
            other documents, and Guarantor shall have taken such actions, if
            any, as Lenders shall reasonably determine are necessary or
            desirable to perfect and protect its security interest in the
            personal property of the Guarantor;

      (d)   No Event of Default or Default shall have occurred and be
            continuing;

      (e)   Borrower shall have duly executed and delivered to each Lender a
            Note in the amount of such Lender's Loan and a Funding Certificate
            in the form of Schedule 1;

      (f)   In Lenders' sole discretion, there shall not have occurred any MAC
            Occurrence;

      (g)   The representations and warranties contained in this Agreement and
            the other Operative Documents to which Borrower is a party shall be
            true and correct in all material respects as if made on such Funding
            Date except as previously otherwise certified to Lenders in writing;

      (h)   Each of the Operative Documents remains in full force and effect;
            and

      (i)   The Funding Date of the Loans shall not be later than the Commitment
            Termination Date.


                                      -2-
<PAGE>
                                    EXHIBIT A

                             SECURED PROMISSORY NOTE

$___________                                          Dated:  September __, 2001

      FOR VALUE RECEIVED, the undersigned, ACUSPHERE, INC., a Delaware
corporation ("Borrower"), HEREBY PROMISES TO PAY to the order of [GATX VENTURES,
INC./VENTURE LENDING & LEASING III, INC.] ("Lender") the principal amount of
______________________________________ Dollars ($_________) or such lesser
amount as shall equal the outstanding principal balance of the Loan made to
Borrower by Lender pursuant to the Loan and Security Agreement referred to below
(the "Loan Agreement"), and to pay all other amounts due with respect to the
Loan on the dates and in the amounts set forth in the Loan Agreement.

      Interest on the principal amount of this Note from the date of this Note
shall accrue at the Loan Rate or, if applicable, the Default Rate. The Loan Rate
for this Note is fifteen percent (15%) per annum based on a year of twelve
30-day months. If the Funding Date is not the first day of the month, interim
interest accruing from the Funding Date through the last day of that month shall
be paid on the Funding Date. Commencing on ________, 2001, and continuing on the
first day of each month thereafter (each, a "Payment Date"), Borrower shall make
to Lender thirty (30) equal payments of principal in the amount of $_________,
plus accrued interest on the then outstanding principal amount.

      Principal, interest and all other amounts due with respect to the Loan,
are payable in lawful money of the United States of America to Lender as set
forth in the Loan Agreement. The principal amount of this Note and the interest
rate applicable thereto, and all payments made with respect thereto, shall be
recorded by Lender and, prior to any transfer hereof, endorsed on the grid
attached hereto which is part of this Note.

      This Note is one of the Notes referred to in, and is entitled to the
benefits of, the Venture Loan and Security Agreement, dated as of September __,
2001, to which Borrower and Lender are parties. The Loan Agreement, among other
things, (a) provides for the making of a secured Loan to Borrower, and (b)
contains provisions for acceleration of the maturity hereof upon the happening
of certain stated events.

      This Note may not be prepaid except in accordance with the Loan Agreement.

      This Note and the obligation of Borrower to repay the unpaid principal
amount of the Loan, interest on the Loan and all other amounts due Lender under
the Loan Agreement is secured under the Loan Agreement.

      Presentment for payment, demand, notice of protest and all other demands
and notices of any kind in connection with the execution, delivery, performance
and enforcement of this Note are hereby waived.


                                      -A-1-
<PAGE>
      Borrower shall pay all reasonable fees and expenses, including, without
limitation, reasonable attorneys' fees and costs, incurred by Lenders in the
enforcement or attempt to enforce any of Borrower's obligations hereunder not
performed when due. This Note shall be governed by, and construed and
interpreted in accordance with, the laws of the State of California.

      IN WITNESS WHEREOF, Borrower has caused this Note to be duly executed by
one of its officers thereunto duly authorized on the date hereof.

                                          ACUSPHERE, INC.

                                          By:
                                             -----------------------------------

                                          Name:
                                               ---------------------------------

                                          Title:
                                                --------------------------------


                                      -A-2-
<PAGE>
                  LOAN INTEREST RATE AND PAYMENTS OF PRINCIPAL


<TABLE>
<CAPTION>
                                              SCHEDULED
            PRINCIPAL                          PAYMENT
  DATE       AMOUNT       INTEREST RATE        AMOUNT       NOTATION BY
  ----       ------       -------------        ------       -----------
<S>         <C>           <C>                 <C>           <C>
</TABLE>







                                      -B-1-
<PAGE>
                                    EXHIBIT B

                                 FORM OF WARRANT


                                      -B-2-
<PAGE>
                                    EXHIBIT C

                           FORM OF OPINION OF COUNSEL




                                          September __, 2001

      GATX Ventures, Inc.
      16 Munson Road, 5th Floor
      Farmington, CT 06032

      Venture Lending & Leasing III, Inc.
      2010 North First Street, Suite 310
      San Jose, CA 95131

            Re: Acusphere, Inc.

      Ladies and Gentlemen:

            We have acted as counsel for Acusphere, Inc., a Delaware corporation
(the "Borrower"), and Acusphere Securities Corporation, a Massachusetts
securities corporation (the "Guarantor"), in connection with the execution and
delivery by the Borrower and Guarantor of the Venture Loan and Security
Agreement (the "Loan Agreement") dated as of the date hereof between the
Borrower, Guarantor and you. Capitalized terms not defined herein shall have the
meanings specified in the Loan Agreement and any supplements thereto. We are
furnishing you this opinion pursuant to Schedule 3, Part I(c) of the Loan
Agreement.

            In connection with this opinion, we have examined originals, or
copies identified to our satisfaction, of the following documents (these
documents being sometimes hereinafter collectively referred to as the "Loan
Documents"):

      1.    the Loan Agreement;

      2.    the Guaranty;

      3.    the Guarantor Security Agreement;

      4.    the Notes; and

      5.    the Warrants.

            As to all questions of fact material to our opinion, we have assumed
the completeness and accuracy of, and have relied upon, the representations and
warranties of the Borrower and Guarantor contained in the Loan Documents, and
upon certificates obtained from and representations made by officers of the
Borrower, the Guarantor and public officials, and have undertaken no independent
verification of such facts.


                                     -C-1-
<PAGE>
      In particular, we have not searched the dockets or records of any court,
government agency or other office in any jurisdiction, or undertaken any
independent investigation to determine the existence or absence of such facts.
Any reference herein to "our knowledge" or to matters "known to us" or "of which
we are aware," or any variation thereof, shall mean the actual knowledge of the
individual attorneys in our firm who participated directly in the specific
transactions to which this letter relates.

      No inference as to our knowledge of the existence or absence of such facts
should be drawn from the fact of our representation of the Borrower and
Guarantor. In our examination of the foregoing documents, we have assumed the
genuineness of all signatures and the legal capacity of all natural persons
executing all documents examined by us, the authenticity and completeness of all
documents submitted to us as originals, the conformity to original documents of
documents submitted to us as copies of facsimiles and the authenticity and
completeness of the originals of such latter documents.

      For the purposes of this opinion, we have assumed (1) the power and
authority of each party other than the Borrower and Guarantor to any of the Loan
Documents to have the Loan Documents to which it is a party executed and
delivered on its behalf and to effect the transactions contemplated by such Loan
Documents to be effected by such party, (2) such party's due authorization,
execution and delivery of the Loan Documents and the taking by such party of all
other actions contemplated to be taken by such party in the Loan Documents, and
(3) the legality, validity, binding effect and enforceability of the Loan
Documents with respect to such party.

      In rendering the opinion set forth in paragraph 1 below with respect to
the due incorporation, legal existence and good standing of the Borrower in
Delaware and the Guarantor in Massachusetts and the due qualification,
authorization and corporate good standing of the Borrower to do business in
Massachusetts, we have relied solely upon certificates received from the
Secretary of State of Delaware and the Secretary of the Commonwealth of
Massachusetts, respectively.

         The opinion expressed in paragraph 3 below that each of the Loan
Documents is a valid and binding obligation of the Borrower and Guarantor and is
enforceable against the Borrower and the Guarantor in accordance with its terms
is subject to the qualifications that:

            (a) enforcement of the rights and remedies created by any Loan
Document is subject to (i) applicable bankruptcy, insolvency, reorganization,
moratorium, fraudulent conveyance or transfer, preference, equitable
subordination or similar laws affecting the rights of creditors or secured
parties generally; (ii) duties and standards imposed on creditors from time to
time, including without limitation, good faith, fair dealing, diligence and
reasonableness under the Uniform Commercial Code, or any other applicable law;
(iii) statutory or decisional law concerning recourse by creditors to security
in the absence of notice and hearing; and (iv) general principles of equity
(whether in a proceeding in equity or at law);

            (b) we express no opinion as to the validity or enforceability of
any provision in the Loan Documents (i) relating to your rights of set-off
against the accounts of the Borrower or Guarantor, to the extent that (A) the
funds on deposit in such accounts are subjected to trustee


                                     -C-2-
<PAGE>
process or attachment or are in any manner special accounts held for the benefit
or trust of a third party, including, without limitation, payroll or tax escrow
accounts, (B) the funds on deposit in such accounts are the identifiable
proceeds of collateral securing either the Borrower's or Guarantor's obligation
to a secured party other than you under Article 9 of the Uniform Commercial
Code, (C) your set-off is directed against uncollected checks or drafts naming
either the Borrower or Guarantor as payee held by you solely as collecting agent
(and not as depository) or (D) you have accepted, certified or paid any item in
accordance with the terms of Article 4 of the Uniform Commercial Code drawn on
either the Borrower's or Guarantor's accounts prior to the exercise of such
set-off rights; (ii) that may be deemed or construed to waive any constitutional
or statutory right of either the Borrower or Guarantor that may not lawfully be
waived; (iii) relating to either the Borrower's or Guarantor's agreement to
submit to the jurisdiction of any court to the extent that any court has the
discretion to assume or decline such jurisdiction; (iv) relating to your
election or cumulation of remedies; (v) relating to the effect of your failure
to exercise any right or remedy provided to you in any of the Loan Documents; or
(vi) relating to the severability of any provision of the Loan Documents;

            (c) we express no opinion as to the applicability of or compliance
with (i) Regulations G, T, U or X of the Board of Governors of the Federal
Reserve System or any similar law or regulation with respect to margin stock or
(ii) any usury law or regulation or any similar law or regulation with respect
to the maximum rate of interest which may be imposed; and

            (d) we express no opinion as to the availability of any equitable
remedy (including without limitation the remedy of specific performance) upon
any breach of any of the provisions of any of the Loan Documents.

         Our opinion is limited to the laws of the Commonwealth of
Massachusetts, the General Corporation Law of the State of Delaware and the
federal laws of the United States of America, and we do not express herein any
opinion with respect to, or with respect to any matter subject to, any other
law. We note that certain of the Loan Documents provide that they are to be
governed by the laws of the State of California, with respect to which we do not
express herein any opinion.

            Based upon and subject to the foregoing, we are of the opinion that:

            1. The Borrower is a corporation duly incorporated, validly existing
and in good standing under the laws of the State of Delaware, and is duly
qualified to do business and is in corporate good standing as a foreign
corporation in the Commonwealth of Massachusetts. The Guarantor is a corporation
duly incorporated, validly existing and in good standing under the laws of the
Commonwealth of Massachusetts

            2. Each of the Borrower and Guarantor has (a) the corporate power to
execute and deliver and to perform its obligations under each of the Loan
Documents, and (b) taken all requisite corporate action to authorize its
execution and delivery of each of the Loan Documents and the performance of its
obligations thereunder; and each of the Loan Documents constitute valid and


                                     -C-3-
<PAGE>
binding obligations of Borrower and Guarantor, enforceable against Borrower and
Guarantor in accordance with its terms.

            3. The execution and delivery of the Loan Documents by each of the
Borrower and Guarantor does not, and the performance by each of the Borrower and
Guarantor of its obligations thereunder will not, result in any violation of the
Amended and Restated Certificate of Incorporation, as amended, or By-laws of the
Borrower or the Borrower's Eighth Amended and Restated Investors' Rights
Agreement dated as of June 1, 2001, as amended and in effect as of the date
hereof, or Articles of Organization, as amended, or By-laws of the Guarantor,
respectively.

            4. Other than as disclosed in the Disclosure Schedule, to our
knowledge, there are no actions, suits or proceedings pending or overtly
threatened against the Borrower or Guarantor before any United States federal or
Commonwealth of Massachusetts court, governmental commission, board, or
authority which, if adversely determined, would have a material and adverse
effect (separately or in the aggregate) on the ability of the Borrower or
Guarantor to perform its obligations under the Loan Documents.

            5. The Warrants have been duly authorized and validly issued by the
Borrower. The shares of Borrower's Series F Non-Voting Preferred Stock, par
value $.01 per share, issuable upon exercise of the Warrants (the "Warrant
Shares") have been duly and validly reserved for issuance by the Borrower. Upon
exercise of the Warrants in accordance with the terms thereof, the Warrant
Shares will be duly authorized, validly issued, fully paid and non-assessable.
The shares of Borrower's Common Stock, par value $.01 per share, issuable upon
conversion of the Warrant Shares (the "Conversion Shares") have been duly and
validly reserved for issuance by the Borrower. Upon conversion of the Warrant
Shares in accordance with the terms thereof, the Conversion Shares will be duly
authorized, validly issued, fully paid and non-assessable.

            This letter is furnished by us as counsel for the Borrower and
Guarantor solely in connection with the transaction described above and is
solely for your benefit and for the benefit of any permitted assignee of your
rights under the Loan Documents, and it may not be relied upon by any other
person or for any other purpose without our prior written consent.

                                          Very truly yours,



                                          TESTA, HURWITZ & THIBEAULT, LLP


                                     -C-4-