Azlactone-functional substrates, (especially hydrogels), mammalian body implants, and methods of making and using them are disclosed. The azlactone-functional substrates are the reaction product of substrates having azlactone-reactive nucleophilic surfaces and a multi-functional azlactone composition having at least two azlactone moieties, where at least one moiety covalently couples to the azlactone-reactive nucleophilic surface and at least one moiety remains available for further nucleophilic reaction, such as with a biologically active material. A preferred use of azlactone-functional hydrogel is as the optical element of a corneal prosthesis which enhances epithethial cell growth.