Other than the normal procedures for transferring ownership of a business (as Regional Centers are LPs/LLCs/etc.) according to the laws of your state, notifying USCIS of the change would be recommended. An I-924 amendment may be required as the more formal of the processes.
The first step is to retain an experienced EB-5 attorney who can advise you of the next steps. The Regional Center may enter into an agreement with the buyer but the buyer cannot take over the ownership or management of this Regional Center until the I-924 Application requesting USCIS to approve the new ownership has been approved. This process may take several months.