disclosed is a method of providing a substrate with a layer comprising a polyvinyl base hydrogel and a biochemically active material by photolithograhy , comprising coating the substrate by centrifugal force with an aqueous solution of a photosensitive hydrogel forming polymer , a crosslinking agent and a biochemically active material , drying said coating , exposing the coated substrate through a photomask to ultraviolet radiation and developing said exposed coating , which is characterized by applying to the substrate an aqueous solution comprising as the cross - linking agent a polyazonium compound and glutardialdehyde . because of this specific combination of cross - linking agents superior properties with respect to the binding of the biochemically active material are obtained .