CARDIUM THERAPEUTICS , I NC. CONVERTIBLE PROMISSORY NOTE

Exhibit 4.1

THE SECURITIES EVIDENCED BY THIS NOTE HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED OR APPLICABLE STATE SECURITIES LAWS, AND NO INTEREST MAY BE SOLD, DISTRIBUTED, ASSIGNED, OFFERED, PLEDGED OR OTHERWISE TRANSFERRED UNLESS (A) THERE IS AN EFFECTIVE REGISTRATION STATEMENT UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS COVERING ANY SUCH TRANSACTION INVOLVING SAID SECURITIES, (B) THE COMPANY RECEIVES AN OPINION OF LEGAL COUNSEL FOR THE HOLDER OF THESE SECURITIES SATISFACTORY TO THE COMPANY STATING THAT SUCH TRANSACTION IS EXEMPT FROM REGISTRATION, OR (C) THE COMPANY OTHERWISE SATISFIES ITSELF THAT SUCH TRANSACTION IS EXEMPT FROM REGISTRATION.

C ARDIUM T HERAPEUTICS , I NC .

CONVERTIBLE PROMISSORY NOTE

Cardium Therapeutics, Inc. , a Delaware corporation (the “ Company ”), for value received, promises to pay to TRC Royalty Co. (the “ Holder ”), or the Holder’s registered assigns, the principal sum of $500,000 (the “ Principal Amount ”).

The Holder and the Company acknowledge that the Company (or its subsidiary) was obligated to make a Milestone Payment of $500,000 to the Holder on February 11, 2009, pursuant to Section 2.2(a)(ii) of the Asset Purchase Agreement made as of August 11, 2006 by and among the Holder, the Company and the Company’s subsidiary (formerly Cardium Biologics, Inc. now Tissue Repair Company). In lieu of making that payment, the Holder, the Company and the Company’s subsidiary have agreed to new terms to substitute for that payment, pursuant to the provisions of this Note:

(a) Principal and Interest . Interest shall accrue on the unpaid Principal Amount at a rate of 0.60% per annum, simple interest (“ Interest ”), representing the applicable federal rate for short-term note obligations in effect for February 2009. Interest will commence accrual as of February 11, 2009. The outstanding Principal Amount will be paid as follows:

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with the balance of the Principal Amount and any accrued and unpaid Interest becoming due and being paid on June 11, 2009 (the “ Maturity Date ”), unless this Note shall be earlier accelerated pursuant to its terms. In the event of any Event of Default (as defined in Section 6), all accrued and unpaid Interest shall be added to the outstanding Principal Amount, and simple interest at a rate of 10% per annum shall begin to accrue until such balance is paid.

(b) Prepayment . The Company may at any time prepay in whole or in part the outstanding Principal Amount, plus accrued and unpaid Interest.

(c) Acceleration . The remaining Principal Amount and all accrued and unpaid interest will accelerate and become immediately due and payable upon the closing of either a Qualified Financing or the sale of the Company’s Innercool Therapies subsidiary. For purposes of this Note, a “ Qualified Financing ” will mean an equity financing in the amount of at least $2,000,000 (inclusive of the conversion of any indebtedness), in one closing or a series of closings.

If, upon the maturity of this Note, the remaining Principal Balance and all accrued and unpaid Interest is not paid in full, the Holder shall have the option, exercisable in its sole discretion, to (a) pursue and exercise all collection remedies provided by this Note or under applicable California creditors’ rights laws, (b) forbear, waive or otherwise accommodate the default or (c) convert the remaining Principal Balance and all accrued and unpaid Interest into shares of the Company’s Common Stock. If the Holder gives the Company written notice of its election to convert this Note into the Company’s Common Stock, the remaining Principal Amount and all accrued and unpaid Interest shall be automatically converted into that number of fully paid and nonassessible shares of Common Stock realized by dividing the remaining Principal Amount and all accrued and unpaid Interest by the Conversion Price. For purposes of this Section, the “ Conversion Price ” will be determined as follows:

(x) if the Company’s Common Stock is then traded on the NYSE Alternext U.S. exchange, the average of the closing or last sale price reported for the five trading days immediately preceding the Maturity Date (with appropriate adjustments for any stock splits, dividends, combinations or the like that occur between the Maturity Date and the date of conversion);

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(y) if the Company’s Common Stock is then not traded on the NYSE Alternext U.S. exchange, but is traded in the over-the-counter market, the average of the closing bid and asked prices reported for the five trading days immediately preceding the Maturity Date (with appropriate adjustments for any stock splits, dividends, combinations or the like that occur between the Maturity Date and the date of conversion); and

(z) in all other cases, the fair value as of the Maturity Date (with appropriate adjustments for any stock splits, dividends, combinations or the like that occur between the Maturity Date and the date of conversion), as determined in good faith by the Company’s Board of Directors.

Neither the Holder nor affiliates of the Holder will engage in sales or short sales of the Company’s Common Stock during the twenty trading days immediately preceding the establishment of the Conversion Price and will provide confirmation of s