Micro Amperometric Immunosensor Based On MEMS

A micro amperometric immunosensor that can be easily integrated with processing circuitry, is developed for human immunoglobulin G (IgG) detection. The sensor, which is composed of two electrodes made of platinum and a micro reaction cell made of SU-8 photoresist, is fabricated on silicon wafer using the Micro-Electro-Mechanical Systems (MEMS) technology.Different methods for antibody immobilization are developed, which includes covalent binding antibody by glutaraldehyde based on conventional immobilization method and novel electropolymerization methods. The electropolymerization methods, such as co-electropolymerizing antibody with polypyrrole, co-electropolymerizing antibody with poly (o-phenylenediamine), and immobilizing antibody oriently on electropolymerized staphylococcal protein A and polypyrrole, show many advantages, such as fast, simple, controllable and suitable for microelectrode with small sample volumes.IgG is specifically recognized in sandwich way and scaled by detecting the current from the catalyzed reaction between enzyme and its substrate. IgG with the concentration of nanogram per microliter can be detected by this micro immunosensor, with reagent usage of only several microlitre.Compared with traditional enzyme linked immunosorbent assay and reported amperometric immunosensor, this micro amperometric immunosensor based on MEMS has many advantages such as easy fabrication, fast response, small reagent usage, miniature in size and easy integration with processing circuitry.