A medical device for implantation into a host organism is disclosed. The device comprises a surface adapted for contact with body tissue of the host organism and an electrode disposed on at least a portion of the surface. Also the device comprises a power source in direct or indirect electrical communication with the electrode. The power source is capable of providing a current to the electrode to create an average surface charge density on the surface that is effective to promote the biocompatibility of the surface with the body tissue or create other desired biological effects.