Antigen detection using microelectrode array microchips

Abstract Procedures and results are described for multiplexed immunochemical assays using semiconductor microchips. The microchips used here are miniaturized arrays of individually addressable microelectrodes controlled by active CMOS circuitry. Electrode densities exceed 1000 per cm 2 . The array chips are coated with a porous reaction layer material to provide a ‘biofriendly’ milieu overlaying the electrode array. Biotin is linked covalently to regions within the porous reaction layer proximate to selected microelectrodes. Covalent linkage is accomplished using reagents that are generated in situ by the microelectrodes. The covalent linkage of biotin within the porous reaction layer allowed traditional streptavidin (SA)-based immunoassay formats to be used on the biochips. Biochips were used to develop multiplexed assay formats for biological entities over a wide size range — from small organic molecules to cells. Sandwich immunoassays were used for larger entities and competitive immunoassays for smaller molecules. Detection of analytes was accomplished using fluorophore-tagged antibodies and epifluorescent microscopy. Results from a broad range of analytes are presented.