HYDROCOATING - A NEW METHOD FOR COUPLING BIOMOLECULES TO SOLID-PHASES

Solid-phase immunoassays such as enzyme-linked immunosorbent assays re quire one of the assay components to be immobilized. Most frequently t his is achieved by passive adsorption of the antigen or antibody to a hydrophobic polymer surface composed of, e.g., polystyrene. Alternativ ely the biomolecule can be bound indirectly via passively adsorbed car rier proteins or directly via functional groups on the solid phase usi ng cross-linking agents. Here we describe a new technique - hydrocoati ng - for covalent immobilization of biomolecules, such as peptides, in highly hydrophilic surroundings. Peptides were immobilized on microti ter plates via covalent bonds to an activated hydrophilic polymer. Sol uble dextran was activated using 2,2,2-triflouroethanesulphonyl chlori de (tresyl chloride) leading to activation of hydroxyl groups on the d extran polymer. This activated dextran molecule was immobilized on a s urface containing amino groups leaving a sufficient number of active g roups for secondary binding of other biomolecules. Peptides, that were either undetectable or poorly recognized when adsorbed on polystyrene , were readily recognized when immobilized by the hydrocoating techniq ue. Furthermore, peptides immobilized by this method were recognized 5 -10-fold better compared to the same peptides immobilized covalently o n a surface containing secondary amino groups. The technique appears t o provide an alternative to passive adsorption of biomolecules on soli d phases and may be useful in the future development of immunoassays.