The invention provides methods of immobilizing an active agent to a substrate surface, including the steps of, providing a substrate, contacting the substrate with a solution of a compound including a trihydroxyphenyl group, thereby forming a trihydroxyphenyl-treated substrate, and contacting the trihydroxyphenyl-treated substrate with an active agent, thereby immobilizing the active agent on the substrate. Further provided are methods of immobilizing an active agent on a substrate, including the steps of providing a substrate, combining a solution of a compound including a trihydroxyphenyl group with a solution of an active agent, thereby forming a solution of an active agent-trihydroxyphenyl conjugate, and contacting the substrate with the solution of the active agent-trihydroxyphenyl conjugate, thereby immobilizing the active agent on the substrate. The invention further provides substrates and medical device or device components with active agents immobilized on the surface thereof.