Site-directed immobilization of immunoglobulin G on 3-aminopropyltriethoxylsilane modified silicon wafer surfaces

Immobilization and distribution properties of the polyclonal antibodies to hepatitis B surface antigen (anti-HBsAg) onto 3-aminopropyltriethoxylsilane (APTES) modified silicon wafer surfaces under two different kinds of coupling conditions were investigated using atomic force microscopy (AFM). Enzyme immunoassay (EIA) and X-ray photoelectric spectroscopy (XPS) were also used as the complimentary techniques to quantify a NH2-terminated siloxane monolayer and a antibody layer. Anti-HBsAg antibodies were site-directly immobilized onto the APTES modified surface: (1) in acetate buffer of pH 5.2 for 3 days at 4°C and (2) in acetate buffer of pH 5.2 containing 5 mM NaBH4 for 12 h, via aldehydes generated on the carbohydrate side chains at the C-terminal of IgG using periodate (NaIO4)-oxidized reactions.