Protein a for human IgG oriented immobilization on silicon surface for an imaging ellipsometry biosensor

Imaging ellipsometry biosensor was developed on the basement of imaging ellipsometry for thin-film and surface characterization. Using protein A to immobilize Human IgG on silicon surface for the imaging ellipsometry biosensor immunoassay was studied. As a result, The Human IgG immobilized on silicon surface by protein A bound much more polyclonal antibody than that on hydrophobic surface directly, which indicated that protein A could be used to immobilize Human IgG molecules in a highly oriented manner and Human IgG molecule could maintain its native configuration well on the silicon surface. Furthermore, the absorption quantity of protein A affecting on interaction of human IgG and antibody molecules was investigated. The surface concentration of Human IgG and antibody molecules was enhanced as well as the increasing of the absorption quantity of protein A, but there are no obvious increase when the ratio of surface concentration of protein A layer to that of saturated adsorption is larger than 80%. However, even decrease slightly.