Method of providing a substrate with a bio-active/biocompatible coating

A method of enhancing the biocompatibility of a substrate by providing said substrate with a continuous bio-active surface coating comprising:

• a) applying to said substrate a first coating comprising an aqueous dispersion or emulsion of (i) a polymer containing an organic acid functional group and (ii) an excess of a polyfunctional cross-linking agent which is reactive with said organic acid groups of said polymer, permitting said first coating to dry in order to cross-link and render said first coating substantially water-insoluble, wherein unreacted polyfunctional cross-linking agent remains present in said cross-linked first coating;
• b) forming said continuous bio-active surface coating on said substrate by contacting said dried first coating layer with a second coating of an aqueous solution or dispersion of a bio-active agent containing an organic acid functional group or metal salt thereof;
• and
• c) drying said first and second coatings to covalently bond said organic acid functional groups of said bio-active agent to said polymer through said excess unreacted polyfunctional cross-linking agent.