Feasibility of an immunosensor based upon capacitance measurements

Abstract The feasibility of a direct immunosensor is shown. The capacitance changes of the heterostructures (semiconductor/thin silica layers with covalently-bonded antibodies/buffer) are measured. A specific signal for the antigen-antibody interaction, which is antigen concentration dependent, is obtained for alpha-fetoprotein and IgE antigens. A sensitivity of 1 ng ml −1 is reached with a monoclonal anti-alpha-fetoprotein. This method can also be used to determine size and to provide evidence of conformational effects.