A biomedical device surface, such as a contact lens surface, is covalently linked to a cationic copolymer. The copolymer may include monomeric units derived from an ethylenically unsaturated monomer containing a quaternary ammonium moiety and monomeric units derived from an ethylenically unsaturated monomer containing a moiety reactive with complementary reactive functionalities at the lens surface. The copolymer may be covalently linked directly to the lens surface, or covalently linked with an intermediate polymer reactive with both the lens surface and the copolymer.
