Methods for treating surfaces of polymeric substrates (as used in medical implants) with inert plasmas to promote the growth of bioentities (such as cells) on these surfaces is disclosed. The treated surfaces are subsequently exposed to an environment to form functionalities associated with enhanced growth of the bioentity on the surface. For example, the substrate may be exposed to the ambient environment. The bioentity may then be deposited on the modified surface. This inert plasma treatment and exposure to a suitable environment does not degrade the implants, and thus improved implants are created. Also, due to the specific functional groups at the modified surface, high cell densities are achieved.