CONVERTIBLE PROMISSORY NOTE

EXHIBIT 4.1

NEITHER THIS NOTE NOR ANY OF THE SECURITIES ISSUABLE UPON CONVERSION HEREOF HAVE BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), OR ANY STATE SECURITIES LAW. NO SALE, TRANSFER, PLEDGE OR ASSIGNMENT OF THIS NOTE OR OF THE SECURITIES ISSUABLE UPON CONVERSION HEREOF SHALL BE VALID OR EFFECTIVE UNLESS (A) SUCH TRANSFER IS MADE PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND IN COMPLIANCE WITH ANY APPLICABLE STATE SECURITIES LAW, OR (B) THE HOLDER SHALL DELIVER TO THE BORROWER AN OPINION OF COUNSEL THAT SUCH TRANSFER IS EXEMPT FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND OF ANY APPLICABLE STATE SECURITIES LAW.

THIS CONVERTIBLE PROMISSORY NOTE (THE “NOTE”) HAS BEEN ISSUED PURSUANT TO AND IS SUBJECT TO THE TERMS OF THAT CERTAIN LOAN AGREEMENT DATED SEPTEMBER 3, 2008 (AS AMENDED FROM TIME TO TIME).

CONVERTIBLE PROMISSORY NOTE

FOR VALUE RECEIVED, VIAGEN, INC. , an Arizona corporation (“ViaGen”), promises to pay, subject to Section 6 below, to the order of Geron Corporation, a Delaware corporation, or its successors and assigns (“Payee”), up to the principal sum of $1,500,000, plus simple interest at the rate of 6% per annum. At any time while an Event of Default (as defined below) is continuing interest shall accrue at a simple interest rate of 8% per annum. Interest will accrue on the outstanding principal balance hereunder from time to time until irrevocably paid in full or converted in accordance with Section 6 hereof. Interest will be computed on the basis of a year of 365 or 366 days as the case may be and the actual number of days elapsed.

      Section 1. Issuance . This Note is issued pursuant to the terms of that certain Loan Agreement, dated as of September 3, 2008, by and between ViaGen and Payee (as amended, supplemented and restated or otherwise modified in writing from time to time, the “Loan Agreement”). Capitalized terms not otherwise defined herein will have meanings set forth in the Loan Agreement.

      Section 2. Maturity Date . Unless sooner converted or the Maturity Date is accelerated in accordance with Section 6, all then outstanding principal and accrued and unpaid interest under this Note, including and up to the Maturity Date (“Outstanding Amount”) will immediately become due and payable on December 31, 2009 (the “Maturity Date”). Notwithstanding the foregoing, should the Transaction not close within 30 days of the date of the Loan Agreement, ViaGen will immediately pay the Outstanding Amount to Payee, whereupon this Note will be cancelled.

      Section 3. Maximum Interest Rate . Anything herein to the contrary notwithstanding, if during any period for which interest is computed hereunder, the amount of interest computed on the basis provided for in this Note, together with all fees, charges and other payments which are treated as interest under applicable law, as provided for herein or in any other document executed in connection herewith, would exceed the amount of such interest computed on the basis of the Highest Lawful Rate, ViaGen shall not be obligated to pay, and Payee shall not be entitled to charge, collect, receive, reserve or take, interest in excess of the Highest Lawful Rate, and during any such period the interest payable hereunder shall be computed on the basis of the Highest Lawful Rate. As used herein, “Highest Lawful Rate” means the maximum non-usurious rate of interest, as in effect from time to time, which may be charged, contracted for, reserved, received or collected by Payee in connection with this Note under applicable law.

     Section 4. Event of Default .

          (a) For purposes of this Note, any and each of the following shall constitute an “Event of Default”:

               (1) Failure by ViaGen to pay any of the obligations under this Note on the date due when the same shall have become due and payable.

               (2) Failure by ViaGen to perform or observe any term, covenant or agreement contained in this Note or the Loan Agreement on its part to be performed or observed and such failure s