A medical device comprising a substrate having a plasma polymerized functionality bonded to at least a portion of the substrate. A superoxide dismutase mimic agent having a complimentary functional group to the plasma polymerized functionality is bonded to the portion of the substrate by bonding to the plasma polymerized functionality. The functionalities can be carboxylate, amine, or sulfate groups and/or polyethylene glycol and can optionally include crosslinking groups.