Nonseparation Electrochemical Enzyme Immunoassay Using Microporous Gold Electrodes

Abstract

In recent years, the coupling of immunological reactions to electrochemical and optical detectors has led to a flurry of research in the area of immunosensor technology. ^{1 - 15} While there have been extensive efforts to devise so-called “direct” immunosensors, where antibodies are immobilized on the surface of a transducer and the immunological binding reaction is monitored via a change in, e.g., innate fluorescence, surface refractive index, or electrical capacitance, the most successful immunosensors from a practical analytical point of view are those that involve the use of labeled reagents (e.g., enzymes, fluorophores). Indeed, such methods are rather similar to their more classical immunoassay counterparts, except that the antibodies are immobilized on the surface of the transducer (e.g., electrode, optical fiber), rather than on the walls of microtiter plates, magnetic particles, or some other solid-phase material. Hence, in many of the immunosensor methods reported to date, where labeled reagents are utilized, extensive washing steps to remove unbound labeled species are required ^{6 - 13, 14}. Hrein, we review recent efforts to devise a novel electrochemical enzyme immunoassay arrangement capable of detecting both large and small molecules at low concentrations without the need for any discrete separation or washing steps.