Protein density gradients on surfaces

Gradients of biologically active proteins can be obtained by applying photochemical reactions. A photosensitive polysaccharide-based polymer (OptoDex) is used to covalently immobilize proteins on surfaces. Gradients of proteins are generated by varying the dose of light during the photoimmobilization. Probe proteins conserve their catalytic activity or immunological binding characteristics when linked to surfaces exemplified by silicon nitride or polystyrene. Heterogeneous immunoreactions between photoimmobilized antigens and antibodies showed an optimum binding efficiency at an antigen density of approximatly 1.3 ng/mm(2).