SURFACE MODIFICATION FOR DIRECT IMMUNOPROBES

The modification of glass-type surfaces by several hydrophilic polymer s of different molecular masses and functional properties [chitosan, d extran, poly(oxyethylene), poly(ethyleneimine) and poly(acrylamide)] w ith respect to the application for direct immunoprobes was investigate d. Activation of the surface was carried out by silanisation and the p olymers were coupled to the surface via amide bonds. The carboxyl deri vative of a hapten was attached to the functional groups of the polyme rs by carbodiimide-activated coupling. As a reference system, the liga nd was directly coupled to the silanised surface. Non-specific protein adsorption, specific binding of antibodies and regeneration were moni tored by evaluation of reflectance spectra obtained by white light int erference at a thin silica layer (RifS). All polymer modified layers s howed improved properties compared to those with direct attachment of the hapten. The non-specific adsorption was reduced to 5-50 %. Binding of a specific antibody was significantly increased by the polymer mod ification: Mass transport limited binding of the specific antibody in low concentrations (30 nM) up to a surface coverage value of 2 ng/mm(2 ) and a maximum surface coverage in the range of a monolayer of IgG (5 -6 ng/mm(2)) was observed for most of the polymers. The surface covera ge found for IgG bound specifically to the dextran-modified surface ex ceeded a protein monolayer.