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                                                                   Exhibit 10.38

                        FOUNDER STOCK PURCHASE AGREEMENT
                        --------------------------------

          THIS AGREEMENT is made this 12th day of April, 2001, by and between
Spine Wave, Inc., a Delaware corporation (the "Company"), and Protein Polymer
Technologies, Inc. ("Purchaser").

          NOW THEREFORE, IT IS HEREBY AGREED:

          1.   Sale of Stock. Subject to the terms hereof, the Company shall
               -------------
sell to Purchaser and Purchaser shall purchase from the Company One Million
(1,000,000) shares of common stock of the Company (the "Stock"). The sale and
purchase shall occur at the offices of the Company on the date set forth above
or at such other place and time as the parties may agree (the "Closing").

          2.   Consideration. In exchange for and as full consideration for the
               -------------
Stock, the Purchaser shall enter into that certain License Agreement with the
Company attached hereto as Exhibit A (the "License Agreement") pursuant to which
                           ---------
Purchaser grants to the Company exclusive rights to certain of Purchaser's
intellectual property solely for use in the Field (as defined in the License
Agreement). In addition, Purchaser shall deliver two (2) duly executed blank
Assignments Separate from Certificate in the form attached hereto as Exhibit C,
                                                                     ---------
which Assignments Separate from Certificate shall only be used in connection
with the exercise of the Company's Repurchase Option as set forth in Section 4
below. The Company and the Purchaser agree that the fair market value of each
share of Stock as of the date of this Agreement equals ** per share (the
"Purchase Price").

          3.   Issuance of Stock. Upon the execution and delivery of the License
               -----------------
Agreement by the Purchaser, the Company shall issue a duly executed certificate
evidencing the Stock in the name of Purchaser and provide Purchaser with a copy
of such certificate. The original of such certificate shall be held in escrow by
the Company until the expiration of the Repurchase Option (as defined below);
provided however, upon Purchaser's request, Company shall release to Purchaser a
certificate representing that number of shares of the Stock which, as of the
date of such request, are no longer subject to the Repurchase Option set forth
in Section 4 below.

          4.   Repurchase Option. The Stock shall be subject to a right (but not
               -----------------
an obligation) of repurchase by the Company (the "Repurchase Option"). The
Company shall have the right to purchase Unvested Shares (as defined below) from
the Purchaser at the Purchase Price on or after termination of the License
Agreement (such termination to be pursuant to the terms set forth therein).

               a. This Repurchase Option shall lapse in accordance with the
schedule attached hereto as Exhibit B (the "Schedule") which sets forth the
                            ---------
amount of Stock which may be repurchased under the Repurchase Option ("Unvested
Shares") and the corresponding contingencies for repurchase. The Repurchase
Option shall terminate and cease to be exercisable with respect to any and all
Unvested Shares upon the earlier of (i) the date that is seven years from the
date hereof; (ii) the date upon which the **; (iii) the consummation of a

**Material is confidential and has been omitted and filed separately with the
Securities and Exchange Commission.


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merger, consolidation or other reorganization of the Company ("Merger") in which
(1) securities representing more than 50% of the total combined voting power of
the voting securities of the successor business entity are not immediately
thereafter beneficially owned directly or indirectly and in substantially the
same proportion by the persons who beneficially owned the Company's outstanding
voting securities immediately prior to such Merger, or (2) the consideration to
the Company's stockholders for the Merger is not solely voting securities, or
(3) at least 50% of the senior executive officers of Company immediately prior
to the Merger do not continue as senior executive officers of the successor
business entity; (iv) the completion of a sale, transfer or other disposition of
all or substantially all of the Company's assets; or (v) the consummation of the
Company's sale of its common stock in a public offering pursuant to a
registration statement under the Securities Act of 1933, as amended (the "Act").

               b.   The Repurchase Option shall be exercised by written notice
signed by the President or Treasurer of the Company and delivered as provided in
subparagraph 10(b) hereof. The Company may pay for the shares of Stock it has
elected to repurchase by delivery of a cashier's check or by wire transfer of
immediately available funds in an aggregate amount equal to the Purchase Price
multiplied by the number of shares of Stock being repurchased.

               c.   Adjustments to Stock. If, from time to time during the term
                    --------------------
of the Repurchase Option, there is any change affecting the Company's
outstanding common stock as a class that is effected without the receipt of
consideration by the Company (through merger, consolidation, reorganization,
reincorporation, stock dividend, dividend in property other than cash, stock
split, liquidating, dividend, combination of shares, change in corporation
structure or other transaction not involving the receipt of consideration by the
Company), then any and all new, substituted or additional securities or other
property to which Purchaser is entitled by reason of Purchaser's ownership of
Stock shall be immediately subject to the Repurchase Option and be included in
the word "Stock" for all purposes of the Repurchase Option with the same force
and effect as the shares of the Stock presently subject to the Repurchase
Option, but only to the extent the Stock is, at the time, covered by such
Repurchase Option. While the aggregate Purchase Price shall remain the same
after each such event, the Purchase Price per share of Stock upon exercise of
the Repurchase Option shall be appropriately adjusted.

          5.   Right of First Refusal. Stock subject to the Repurchase Option
               ----------------------
may not be transferred, except for transfers by operation of law or other
involuntary transfer. Before any shares of Stock registered in the name of
Purchaser and not subject to the Repurchase Option may be sold or transferred
(excluding transfer by operation of law or other involuntary transfer) such
shares shall first be offered to the Company in the following manner:

               a.   The Purchaser or its transferee shall deliver a notice
pursuant to subparagraph 10(b) ("Notice") to the principal business office of
the Company stating (i) the bona fide intention to sell or transfer such shares,
(ii) the number of such shares of Stock to be sold or transferred, (iii) the
price and other terms, if any, for which Purchaser or its transferee proposes to
sell or transfer such shares of Stock, and (iv) the name and address of the
proposed purchaser or transferee and that such purchaser or transferee is
committed to acquire the stated number of shares on the stated price and terms.

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               b. The Company shall have the right at any time within twenty
(20) days of receipt of the Notice to purchase all of the shares to which the
Notice refers at the price per share specified in the Notice, or if no price is
specified therein, at the fair market value thereof as determined by the Board
of Directors in good faith. Said right shall be exercised by written notice
signed by the President or any Vice President of the Company and delivered as
provided in subparagraph 10(b) hereof, which notice shall specify the time,
place and date for settlement of such purchase.

               c. In the event the Company does not, for any reason, exercise
its right pursuant hereto, the Company may assign such right, provided such
right shall not extend beyond such twenty (20) day period. If exercised by the
assignee pursuant hereto, the right to purchase shall be exercised by written
notice signed by the exercising assignee and delivered as provided in
subparagraph 10(b) hereof, which notice shall specify the time, place and date
for settlement of such purchase. Purchaser shall sell the shares to the Company
or such assignees within thirty (30) days after the date of the Notice.

               d. If all of the shares to which the Notice refers are not
purchased, as provided in subparagraphs 5(b) or 5(c) above, the Purchaser may
sell such shares to the person named in the Notice at the price and terms
specified in the Notice, provided that such sale or transfer is consummated
within seventy five (75) days of the date of the Notice to the Company, and
provided further that any such sale is in accordance with all the terms and
conditions hereof. If Purchaser does not consummate the sale or transfer within
such seventy five (75) day period, the right provided hereby shall be deemed to
be revived with respect to such shares and no sale or transfer shall be effected
without first offering the shares in accordance herewith.

               e. Notwithstanding the above, neither the Company nor the
assignees of the Company shall have any right of first refusal under this
Section 5 at any time subsequent to the following: i) the closing of a bona
fide, firm commitment underwritten public offering of the common stock of the
Company pursuant to a Registration Statement declared effective under the Act,
or ii) the first date on which the Stock is held of record by more than five
hundred (500) persons. In addition, the Company's right of first refusal under
this Section 5 shall not apply to the proposed sale or transfer by Purchaser of
stock subject to this Agreement as part of the sale of all or substantially all
of Purchaser's assets ("Sale of Assets") except in the event that the Sale of
Assets is to a direct competitor of the Company or to such other entity which
directly or indirectly controls a direct competitor of the Company and provided
that in such circumstance, the time period set forth in subparagraph 5(d) above
shall be 180 days.

          6.   "Market Stand-Off" Agreement. Purchaser hereby agrees that,
                ---------------------------
during the period specified by the Company (such period not to exceed one
hundred eighty (180) days in the case of an initial public offering, and ninety
(90) days for all subsequent offerings) and the underwriter or underwriters of
common stock (or other securities) of the Company following the effective date
of a registration statement of the Company filed under the Act, Purchaser shall
not, to the extent requested by the Company and such underwriter, and without
the prior written consent of the managing underwriter of such offering, directly
or indirectly, sell, offer or contract to sell (including, without limitation,
any short sale), grant any option to purchase or otherwise

                                       3

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transfer or dispose of (other than to donees who agree to be similarly bound)
any securities of the Company at any time during such period except common stock
included in such registration, provided, however, that all officers, directors,
founders (to the extent such founder is employed by the Company at such time)
and beneficial holders of 5% or more of the Company holding securities of the
Company enter into similar agreements.

          In order to enforce the foregoing covenant, the Company may impose
stop-transfer instructions with respect to common stock held by Purchaser until
the end of such period.

          7.   Representations and Warranties of Purchaser.
               -------------------------------------------

               a.   Due Authorization. Purchaser hereby represents and warrants
                    -----------------
to Company that it is duly authorized and empowered to enter into and perform
this Agreement; and the execution and performance of this Agreement by Purchaser
does not and will not conflict with or violate any contract, agreement,
indenture, mortgage, instrument, writ, judgment, or order of any court, arbiter
or governmental or quasi-governmental body to which Purchaser is a party or by
which Purchaser is bound.

               b.   Investment Intent. This Agreement is made with Purchaser in
                    -----------------
reliance upon its representation to the Company, which by Purchaser's acceptance
hereof confirms, that the Stock has been acquired by Purchaser for investment
for an indefinite period for Purchaser's own account, not as a nominee or agent,
and not with a view to the sale or distribution of any part thereof, and that
Purchaser has no present intention of selling, granting participation in, or
otherwise distributing the same. By executing this Agreement, Purchaser further
represents that Purchaser does not have any contract, undertaking, agreement or
arrangement with any person to sell, transfer, or grant participations, to such
person or to any third person, with respect to any of the Stock.

               c.   Restricted Securities. Purchaser understands that the Stock
                    ----------------------
has not been registered under the Act, on the ground that the sale provided for
in this Agreement is exempt from the registration requirements of the Act, and
that the Company's reliance on such exemption is predicated on Purchaser's
representations set forth herein.

          Purchaser understands that if the Company does not register with the
Securities and Exchange Commission pursuant to Section 12 or 15 of the
Securities Exchange Act of 1934, as amended, or if a registration statement
covering the Stock (or a filing pursuant to the exemption from registration
under Regulation A of the Act) under the Act is not in effect when Purchaser
desires to sell the Stock, Purchaser may be required to hold the Stock for an
indeterminate period. The Purchaser also acknowledges that Purchaser understands
that any sale of the Stock that might be made Purchaser in reliance upon Rule
144 under the Act may be made only in limited amounts in accordance with the
terms and conditions of that rule and that Purchaser may not be able to sell the
Stock at the time or in the amount Purchaser so desires. Purchaser is familiar
with Rule 144 and understands that the Stock constitutes "restricted securities"
within the meaning of that Rule.

               d.   Investment Experience. In connection with the investment
                    ---------------------
representations made herein Purchaser represents that Purchaser is either an
"Accredited

                                        4

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Investor", as that term is defined in Rule 501 of Regulation D promulgated under
the Act, or is able to fend for itself in the transactions contemplated by this
Agreement, has such knowledge and experience in financial and business matters
as to be capable of evaluating the merits and risks of its investment, has the
ability to bear the economic risks of its investment and has been furnished with
and has had access to such information as Purchaser has requested and deems
appropriate to its investment decision.

               e.   Limitations  on  Disposition.  Purchaser agrees that in no
                    ----------------------------
event will Purchaser make a disposition of any of the Stock, unless and until
(i) Purchaser shall have notified the Company of the proposed disposition, and
(ii) Purchaser shall have furnished the Company with an opinion of counsel
satisfactory to the Company to the effect that such disposition will not require
registration of such Stock under the Act or that appropriate action necessary
for compliance with the Act has been taken, or (iii) the Company shall have
waived, expressly and in writing, its rights under clauses (i) and (ii) of this
subparagraph. In addition, prior to any disposition of any of the Stock, the
Company shall require the transferee or assignee to provide in writing
investment representations and such transferee's or assignee's agreement to be
bound by the right of first refusal and market stand-off provisions hereof in a
form acceptable to the Company.

               The Company shall not be required (I) to transfer on its books
any shares of Stock of the Company which shall have been sold or transferred in
violation of any of the provisions set forth in this Agreement, or (II) to treat
as owner of such shares or to accord the right to vote as such owner or to pay
dividends to any transferee to whom such shares shall have been so transferred.
Purchaser shall, during the term of this Agreement, exercise all rights and
privileges of a stockholder of the Company with respect to the Stock after the
issuance, and prior to the repurchase, thereof.

               f.   Legends. All certificates representing any shares of Stock
                    -------
of the Company subject to the provisions of this Agreement shall have endorsed
thereon the following legends:

               (i)  "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"). THESE
SECURITIES HAVE BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION
OR RESALE, AND THEY MAY NOT BE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION
STATEMENT FOR SUCH SHARES UNDER THE ACT OR PURSUANT TO RULE 144 UNDER THE ACT OR
AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT REGISTRATION IS NOT
REQUIRED UNDER THE ACT."

               (ii) "THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT
TO THE TERMS AND CONDITIONS OF A CERTAIN FOUNDER STOCK PURCHASE AGREEMENT
BETWEEN THE COMPANY AND THE HOLDER HEREOF WHICH INCLUDES A MARKET STAND-OFF
AGREEMENT, A RIGHT OF REPURCHASE AND A RIGHT OF FIRST REFUSAL ON THE SALE OF THE
SECURITIES. THESE SECURITIES MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED,
OR IN ANY MANNER DISPOSED OF EXCEPT IN CONFORMITY WITH

                                        5

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THE TERMS OF SUCH AGREEMENT. COPIES OF THE AGREEMENT MAY BE OBTAINED UPON
WRITTEN REQUEST TO THE SECRETARY OF THE COMPANY."

               (iii) Any legend required to be placed thereon by applicable
state laws.

          8.   Conditions Precedent to Purchaser's Obligations. Pursuant to the
               -----------------------------------------------
terms of that certain Convertible Promissory Note Purchase Agreement of even
date herewith (the "Note Purchase Agreement"), on the date of Closing, Windamere
II LLC ("Investor") shall have purchased and Company shall have issued to
Investor that certain Convertible Promissory Note in aggregate principal amount
of ** (the "Convertible Note"). Pursuant to the terms of the Note Purchase
Agreement, Investor shall have the right to purchase, in ** increments, up to **
aggregate principal amount of additional convertible promissory notes on the
same terms as the Convertible Note.

          9.   Representations and Warranties of Company.
               -----------------------------------------

               a. As of the date of Closing, the authorized capital stock of the
Company consists of 4,000,000 shares of common stock, $.001 par value per share,
(the "Common Stock").

               b. As of the date of Closing, the Company has reserved 1,500,000
shares of Common Stock for issuance pursuant to the Company's 2001 Stock
Option/Stock Issuance Plan.

               c. Immediately following the Closing, the Company shall have
issued and outstanding 2,950,000 shares of Common Stock.

               d. Company hereby represents and warrants to Purchaser that it is
duly authorized and empowered to enter into and perform this Agreement; and the
execution and performance of this Agreement by the Company does not and will not
conflict with or violate any contract, agreement, indenture, mortgage,
instrument, writ, judgment, or order of any court, arbiter or governmental or
quasi-governmental body to which the Company is a party or by which the Company
is bound.

          10.  Miscellaneous.
               -------------

               a. Further Instruments and Actions. The parties agree to execute
                  -------------------------------
such further instruments and to take such further action as may reasonably be
necessary to carry out the intent of this Agreement.

               b. Notices. All notices required or permitted hereunder shall be
                  -------
in writing and shall be deemed effectively given: (i) upon personal delivery to
the party to be notified, (ii) when sent by confirmed facsimile transmission if
sent during normal business hours of the recipient; if not, then on the next
business day, or (iii) for domestic addresses one (1) business day after deposit
with a nationally recognized overnight courier, specifying next day delivery,
with written verification of receipt and for international addresses three (3)
business days after deposit with a nationally recognized overnight courier,
specifying next day delivery,

**Material is confidential and has been omitted and filed separately with the
Securities and Exchange Commission.

                                       6

<PAGE>

with written verification of receipt. All communications shall be sent to the
party to be notified at the address as set forth on the signature pages hereof
or at such other address as such party may designate by ten (10) days advance
written notice to the other parties hereto.

               c.  Governing Law, Assignment and Enforcement. This Agreement is
                   -----------------------------------------
governed by the internal law of California and shall inure to the benefit of the
successors and assigns of the Company and, subject to the restrictions on
transfer herein set forth, be binding upon Purchaser, its successors and
assigns. The prevailing party in any action to enforce this Agreement shall be
entitled to attorneys' fees and costs. The parties agree that damages are not an
adequate remedy for breach hereof and each party shall accordingly be entitled
to specific performance of this Agreement.

               d.  Entire Agreement; Amendments and Waivers. This Agreement and
                   ----------------------------------------
the related License Agreement, Supply and Services Agreement, Voting Agreement
and Escrow Agreement, among Purchaser and Company, and all of even date
herewith, constitute the entire agreement and understanding between the parties
with respect to the subject matter contained herein, and there are no promises,
representations, conditions, provisions or terms related thereto other than as
set forth in this Agreement and the related License Agreement, the Supply and
Services Agreement, Voting Agreement and Escrow Agreement between the Purchaser
and Company all of even date herewith. This Agreement may only be amended with
the written consent of the parties hereto, or their successors or assigns, and
no oral waiver or amendment shall be effective under any circumstances
whatsoever.

               e.  Cooperation. Purchaser agrees to cooperate affirmatively with
                   -----------
the Company, to the extent reasonably requested by the Company, to enforce
rights and obligations pursuant to this Agreement.

          11.  California Commissioner of Corporations. THE SALE OF THE
               ---------------------------------------
SECURITIES WHICH ARE THE SUBJECT OF THIS AGREEMENT HAS NOT BEEN QUALIFIED WITH
THE COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA, AND THE ISSUANCE OF
SUCH SECURITIES OR THE PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION
THEREFOR PRIOR TO SUCH QUALIFICATION IS UNLAWFUL UNLESS THE SALE OF SECURITIES
IS EXEMPT FROM QUALIFICATION BY SECTION 25100, 25102 OR 25105 OF THE CALIFORNIA
CORPORATIONS CODE. THE RIGHTS OF ALL PARTIES TO THIS AGREEMENT ARE EXPRESSLY
CONDITIONED UNLESS THE SALE IS SO EXEMPT.

                                        7

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     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                                   SPINE WAVE, INC.


                                   By: _________________________________________
                                       David Coats
                                       President and Chief Executive Officer

                         Address:  12230 El Camino Real, Suite 300
                                   San Diego, California 92130


                                   PURCHASER

                                   Protein Polymer Technologies, Inc.

                                   _____________________________________________
                                       J. Thomas Parmeter
                                       President and Chief Executive Officer

                         Address:  10655 Sorrento Valley Road
                                   San Diego, California 92121



              [Signature Page To Founder Stock Purchase Agreement]


<PAGE>

                                    EXHIBIT A
                                    ---------

                               [LICENSE AGREEMENT]

Filed separately under Exhibit 10.39 of the Registrant's Form 10-KSB for fiscal
year ended December 31, 2001.



<PAGE>

                                    EXHIBIT B
                                    ---------

                                VESTING SCHEDULE

**

** Material is confidential and has been omitted and filed separately with the
   Securities and Exchange Commission.


<PAGE>

                                    EXHIBIT C
                                    ---------

                      ASSIGNMENT SEPARATE FROM CERTIFICATE



          FOR VALUE RECEIVED, Protein Polymer Technologies, Inc. hereby sells,
assigns and transfers unto _____________________________, ______________________
(__) shares of the Common Stock of Spine Wave, Inc., standing in its name on the
books of said corporation represented by Certificate No.___ herewith and do
hereby irrevocably constitute and appoint __________________ attorney to
transfer said stock on the books of the within-named corporation with full power
of substitution in the premises.

Dated: _________________, _____.


                                         Protein Polymer Technologies, Inc.



                                         _______________________________________
                                         By:
                                         Its:

          This Assignment Separate from Certificate was executed in conjunction
with the terms of a Founder Stock Purchase Agreement between the above assignor
and Spine Wave, Inc. dated April __, 2001.