The present invention is directed to a stabilized bioactive hydrogel matrix coating for substrates, such as medical devices. The invention provides a coated substrate comprising a substrate having a surface, and a bioactive hydrogel matrix layer overlying the surface of the medical device, the hydrogel matrix comprising a first high molecular weight component and a second high molecular weight component, the first and second high molecular weight components each being selected from the group consisting of polyglycans and polypeptides, wherein at least one of the first and second high molecular weight components is immobilized (e.g., by covalent cross-linking) to the surface of the substrate.