COMPARISON OF TECHNIQUES FOR ENZYME IMMOBILIZATION ON SILICON SUPPORTS

Enzyme immobilization onto silicon substrates has been investigated by five different coupling procedures. The methods included covalent cou pling either through a metal link reagent or silane reagents containin g pendant amino or epoxide linkers, an entrapment technique using a th in layer of gelatin, or an adsorption technique using poly-L-lysine. T hese immobilization procedures were evaluated using glucose oxidase an d a simple spectrophotometric method employing Fenton's reagent. Reten tion of enzyme activity and surface loading were assessed. The immobil ization techniques were also evaluated by electron microscopy to chara cterize the evenness of the surface coatings. All of the covalent coup ling procedures led to surface loadings, approaching I pmol mm(-2); ho wever, the surfaces appeared irregular on a microscopic scale. The pol y-L-lysine adsorption technique provided the smoothest surface. With t he exception of the entrapment technique, all immobilization procedure s provided immobilized enzyme that retained >75% activity after severa l weeks of storage. (C) 1998 Elsevier Science Inc.