Site-directed immobilization antibody for alpha-fetoprotein detection by optical biosensor

Carbohydrate side chain in antibody Fc region can be oxidized into aldehyde group by sodium m-periodate, which can simultaneously couple with the amino-group on silicon surface obtained by chemistry modification. This combination will introduce C=N linkage and site-directed immobilization of antibody, which was confirmed by AFM observation. The acquired antibody layer can then be used for immunoassay for alpha-fetoprotein (AFP). The combined antigen is directly detected by imaging ellipsometry in grayscale format. The proposed method was further compared with commercial kit by determination 20 clinic samples with significant correlation (R = 0.93).