OFFER OF EMPLOYMENT

EXHIBIT 10.23

January 28, 2005

Doug Arm, Ph. D.

Dear Dr. Arm:

We are pleased to offer you the position of Vice-President of Development - Biologics at a salary of $13,333 per month (which, if computed on an annual basis, would be equivalent to $160,000), payable semi-monthly. You will report to me, and your start date will be Monday, February 15^th, 2005.  Both the device development groups in Engineering and Biologics will report to you.  You will also primarily manage outside relationships relative to this project.  In effect, you will, in conjunction with me, have overall responsibility for the current engineering development and future direction of the stem cell device projects. You will have primary project management duties and responsibility to interact with quality, regulatory, production as well as related outside groups.  In addition, you will likely be called upon to interact with marketing, clinical trials coordinators and clinicians.  Clearly this will be a very challenging but very rewarding opportunity.

You will receive MacroPore’s employee benefits comparable to MacroPore’s standard package, including PPO medical insurance for you and your family, group life insurance, group long-term disability insurance, and participation in our flexible spending account and 401(k) plan. Your paid time off will be four (4) weeks per year.

We will propos