<PAGE>

                                                                   Exhibit 10.37

                           POLAR MOLECULAR CORPORATION
                               PURCHASE AGREEMENT

                                October 25, 2001

Polar Molecular Corporation
4600 S. Ulster St., Suite 700
Denver, Colorado 80237
Fax:  (303) 804-3825

Gentlemen and Ladies:

     1. Purchase. This Purchase Agreement (this "Agreement") is entered into by
the undersigned ("Purchaser"), and Purchaser hereby purchases from Polar
Molecular Corporation, a Delaware corporation (the "Company"), for a total
purchase price of $600,000 (the "Purchase Price") the following: (a) a
Promissory Note in the principal amount of $600,000 substantially in the form
attached as Exhibit A (the "Note") and (b) 555,556 shares (which number of
shares reflects the effectiveness of the Company's reverse stock split) of
common stock (the "Stock"), par value $0.0001 per share, of the Company (the
"Common Stock"). Upon execution of this Agreement, Purchaser has delivered the
full amount of the Purchase Price, and the Company has executed and delivered
the Note and issued the Stock.

     2. Representations and Warranties of Purchaser. Purchaser hereby
represents, warrants, and agrees:

          (a) Unregistered Securities. Neither the Note, nor the Stock
(collectively, the "Securities") is registered under the Securities Act of 1933
(the "Securities Act") or any state securities laws. The offering and sale of
the Securities is intended to be exempt from registration under the Securities
Act by virtue of Section 4(2) and/or Section 4(6) of the Securities Act and the
provisions of Regulation D promulgated thereunder, based in part upon the
representations, warranties, and agreements contained herein. Neither the
Securities and Exchange Commission nor any state securities commission has
approved the Securities or passed upon or endorsed the merits of the investment
or reviewed or confirmed the accuracy or determined the adequacy of any
information furnished to Purchaser by the Company.

          (b) Access to Information. All documents, records, and books of the
Company pertaining to the investment in the Securities have been made available
for inspection by Purchaser. Purchaser has had a reasonable opportunity to
obtain any additional information, review any additional documents, and meet
with representatives of the Company or have them answer any questions and
provide additional information regarding this investment and the finances,
operations, business, and prospects of the Company deemed relevant by Purchaser.
All such questions have been answered and requested information provided to
Purchaser's full satisfaction.

<PAGE>

          (c) Suitability; Accredited Investor. Purchaser has such knowledge and
experience in financial, tax, and business matters to evaluate the merits and
risks of an investment in the Securities and to make an informed investment
decision with respect thereto. Purchaser is aware that an investment in the
Securities involves very significant risks and acknowledges that the Company is
in the development stage and has substantial immediate needs for additional
financing in order to continue in the development stage. Purchaser meets the
requirements of at least one of the suitability standards for an "accredited
investor" as defined under Rule 501(a) of the Securities Act. Purchaser has a
sufficient net worth to sustain a loss of its entire investment in the Company
in the event such a loss should occur; and this investment is a suitable one for
Purchaser.

          (d) Investment Intent; Restrictive Legend. Purchaser is acquiring the
Securities solely for Purchaser's own account for investment and not with a view
to resale or distribution. Purchaser must bear the economic risk of the
investment indefinitely because none of the Securities may be sold,
hypothecated, or otherwise disposed of unless subsequently registered under the
Securities Act and applicable state securities laws or an exemption from
registration is available. Legends will be placed on the Note and certificates
representing the Stock to the effect that they have not been registered under
the Securities Act or applicable state securities laws and appropriate notations
thereof will be made in the Company's stock books; stop transfer instructions
will be placed with any transfer agent.

     3. Representations and Warranties of Company. The Company represents,
warrants, and agrees:

          (a) Due Incorporation and Authorization. The Company is duly
incorporated, validly existing, and in good standing under the laws of the State
of Delaware. As of the date of the closing of the transactions contemplated
hereby, the Company shall have duly authorized the issuance and sale of the
Securities in accordance with the terms of this Purchase Agreement by all
requisite corporate action.

          (b) Issuance of Securities. The shares of Stock, when issued, will
represent validly authorized, duly issued, fully paid, and nonassessable shares
of Common Stock of the Company. The issuance of the Securities will not conflict
with the certificate of incorporation, as amended, or the bylaws of the Company
or any material contract to which the Company is a party. The Company has
complied in all material respects with all laws applicable to the issuance of
the Securities.

          (c) Liens and Security Interests. The Company is the owner of the
"Collateral" (as such term is defined in that certain Security Agreement between
the Company and the Borrower dated as of the date hereof and to become effective
in accordance with the terms thereof (the "Note Security Agreement")) free and
clear of any lien, security interest, or other charge or encumbrance except for
the lien and security interest created by that certain Security Agreement
between the Company and certain other parties (the "Existing Security
Agreement") dated January 30, 2001. Purchaser acknowledges and accepts that
under that certain Security Agreement between the Company and Lockhart Holdings,
Inc. (the "Lockhart Security Agreement") dated October   , 2001 the Company will
                                                       --
grant a lien and security interest in the

                                       2

<PAGE>

Collateral to Lockhart Holdings, Inc. ("Lockhart") which will be junior to the
lien and security interest granted to Purchaser pursuant to the Note Security
Agreement and which will also become effective upon the redemption of the
Company's Series B Preferred Stock.

          (d) Available Funds. As of the date of the closing of the transactions
contemplated hereby, the Company shall have sufficient funds (including the
proceeds to be delivered to the Company by Purchaser pursuant to the terms of
this Agreement) to redeem all of the outstanding shares of the Company's Series
B Preferred Stock.

     4. Use of Proceeds. The Company agrees to use all of the proceeds from the
sale of the Securities for the exclusive purpose of redeeming the Company's
outstanding Series B Preferred Stock in order to obtain the release of the liens
granted pursuant to the Existing Security Agreement. Without the prior written
consent of Purchaser, the Company shall not use the proceeds from the sale of
the Securities for any other purpose.

     5. Registration Rights. The Company hereby agrees to grant Purchaser
registration rights pursuant to the terms of the Investor's Rights Agreement, a
form of which is attached hereto as Exhibit B.

     6. Covenants of Purchaser.

          (a) Subordination. Upon the request of the Company, Purchaser hereby
agrees to subordinate, on usual and customary terms, the repayment of
indebtedness evidenced by the Note with respect to equipment loans or leases
(not to exceed $50,000 per each such loan or lease) incurred in the ordinary
course of business from financial institutions, if the Company is requested by
such financial institutions to obtain such agreement of subordination.

          (b) Restrictions on Transfer of Securities. Purchaser shall not sell,
assign, transfer, give, pledge, hypothecate, encumber or otherwise dispose of
the Securities without the prior written consent of the Company, which consent
shall not be unreasonably withheld.

          (c) Lock-Up. In connection with an initial public offering of the
Company's securities, Purchaser agrees that, without the prior written consent
of the Company, Purchaser shall not offer, sell, contract to sell, or otherwise
dispose of any shares of Stock or Conversion Shares for and during the period
beginning on the date that the Company executes an underwriting agreement with
respect to such public offering and continuing to and including 180 days
thereafter, for sales of securities under Rule 144 under the Securities Act, and
two years in the case of all sales and dispositions, after the effective date of
the registration statement under the Securities Act for such offering.

     7. Covenant of the Company. The Company and Purchaser shall execute the
Note Security Agreement in substantially the form attached hereto as Exhibit C
concurrent with the execution of this Agreement and the Note.

     8. Conditions to Closing.

                                       3

<PAGE>

          (a) As a condition to the closing of the transactions contemplated
hereby, the Company shall deliver each of the following:

               (i) an officer's certificate of the Company attesting to the
authenticity of the articles of incorporation and bylaws of the Company;

               (ii) the duly executed Note in substantially the form attached
hereto as Exhibit A;

               (iii) the duly executed Investor's Rights Agreement in
substantially the form attached hereto as Exhibit B;

               (iv) the duly executed Note Security Agreement in substantially
the form attached hereto as Exhibit C;

               (v) a duly executed stock certificate of the Company representing
the transfer of the Stock to Purchaser;

               (vi) an executed UCC-1 financing statement with a description of
the Collateral to be filed by Purchaser with the Delaware Secretary of State;

               (vii) duly executed assignments, sufficient in form to secure and
to register Purchaser's security interest in the Collateral with the appropriate
patent and trademark offices;

               (viii) the duly executed Reaffirmation of Invention Assignment
and Confidentiality Agreement of each of Mark Nelson, Alan Smith and Chandra
Prakash;

               (ix) an Affirmation of Assignment of Patent Rights and Security
Agreement duly executed by each of Otis Nelson, Mark Nelson and A. Richard
Nelson; and

               (x) copies of all releases obtained from the holders of the
Company's Series B Preferred Stock.

          (b) Upon delivery of each of the documents listed above, or the waiver
of such delivery by Purchaser, Purchaser shall deliver the Purchase Price to the
Company in immediately-available funds.

          (c) As soon as practicable, the Company shall deliver to Purchaser
copies of recorded UCC-3 termination statements reflecting the termination of
the security interest of the holders of the Company's Series B Preferred Stock
in the Collateral.

     9. Modification. This Agreement shall not be modified or waived except in a
writing signed by both parties.

                                       4

<PAGE>

     10. Notices. Any notice or other communication hereunder shall be in
writing and shall be mailed by certified mail, return receipt requested,
transmitted by facsimile, or delivered against receipt to the party to whom it
is to be given (a) if to the Company, at the address set forth above, or
facsimile number, or (b) if to Purchaser, at the address or facsimile number set
forth on the signature page hereof (or, in either case, to such other address or
facsimile number as the party shall have furnished in writing in accordance with
the provisions of this Section 10). Each such notice or other communication
shall for all purposes of this Agreement be treated as effective or as having
been given when (x) delivered if delivered personally, (y) if transmitted by
facsimile, upon conclusion of the transmission, or (z) if sent by certified
mail, at the time of certification thereof.

     11. Assignability. This Agreement and the rights, interests and obligations
hereunder are not transferable or assignable by Purchaser, without the prior
written consent of the Company.

     12. Applicable Law. This Agreement shall be governed by and construed in
accordance with the internal laws of the State of Colorado without regard to its
conflicts of laws principles. Purchaser hereby irrevocably submits to the
jurisdiction of any State of Colorado or United States court sitting in the City
and County of Denver over any action or proceeding arising out of or relating to
this Agreement or any agreement contemplated hereby, and all claims in respect
of such action or proceeding may be heard and determined in such court.
Purchaser further waives any objection to venue in the State of Colorado and any
objection to any action or proceeding in such State on the basis of an
inconvenient forum. EACH OF PURCHASER AND THE COMPANY HEREBY WAIVES ITS RIGHTS
TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF
THIS AGREEMENT OR ANY DOCUMENT OR AGREEMENT CONTEMPLATED HEREBY.

     13. Confidentiality. Purchaser agrees that any information or data it has
acquired from or about the Company, not otherwise properly in the public domain,
was received in confidence. Purchaser shall not divulge, communicate, or
disclose, except as may be required by law or for the performance of this
Agreement, or use to the detriment of the Company or for the benefit of any
other person, or misuse in any way any confidential information of the Company,
including without limitation any technical, trade, or business secrets of the
Company and any technical, trade, or business materials that are treated by the
Company as confidential or proprietary, including without limitation ideas,
discoveries, inventions, developments, know-how and improvements belonging to
the Company and confidential information obtained by or given to the Company
about or belonging to third parties.

     14. Miscellaneous.

          (a) Entire Agreement. This Agreement constitutes the entire agreement
between Purchaser and the Company with respect to the subject matter hereof and
supersedes all prior oral or written agreements and understandings, if any,
relating to the subject matter hereof.

                                       5

<PAGE>

          (b) Survival. Purchaser's and the Company's representations and
warranties made in this Agreement shall survive the execution and delivery
hereof and of the Note and the Stock.

          (c) Fees and Expenses. The Company hereby agrees to reimburse
Purchaser for all of Purchaser's out-of-pocket costs incurred as reasonable fees
and expenses (including the fees of any attorneys, accountants, appraisers, or
others engaged by such party) in connection with this Agreement and the
transactions contemplated hereby, whether or not the transactions contemplated
hereby are consummated, which reimbursement shall be made no later than 120 days
following the execution of this Agreement or the termination of negotiations in
connection herewith; provided that the Company shall not reimburse Purchaser for
any such fees and expenses in excess of $15,000.

          (d) Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which shall
together constitute one and the same instrument.

          (e) Severability. Each provision of this Agreement shall be considered
separate. If for any reason any provision or provisions hereof are determined to
be invalid or contrary to applicable law, such invalidity shall not impair the
operation of or affect the remaining portions of this Agreement.

                            [SIGNATURE PAGE FOLLOWS]

                                       6

<PAGE>

     The undersigned have executed this Agreement to be effective as of the date
first set forth above.

PURCHASER:


AFFILIATED INVESTMENTS, L.L.C.
Address:
           -------------------------------------

           -------------------------------------
Fax:  (  )
           -------------------------------------


By: /s/ Bruce Becker
    --------------------------------------------
   Its: President


ACCEPTED AND AGREED October 25, 2001.

COMPANY:

POLAR MOLECULAR CORPORATION


By: /s/ Mark L. Nelson
    --------------------------------------------
        Mark L. Nelson, President and
        Chief Executive Officer

                                        7