Development of Electrochemiluminescence and Surface Plasmon Resonance based Immunosensors with Surface Accumulable Molec
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Development of Electrochemiluminescence and Surface Plasmon Resonance based Immunosensors with Surface Accumulable Molecules. Ryoji Kurita National Institute of Advanced Industrial Science and Technology 1-1-1 Higashi, Tsukuba, Ibaraki, JAPAN ABSTRACT The electrochemiluminescence (ECL) and surface plasmon resonance (SPR) based immunosensors for measuring a trace level of disease markers are shown. It is well known that thiols form a self-assembled monolayer on a metal surface, and this has been widely used to modify metal surfaces. We employed this characteristic for a highly sensitive immunosensors by obtaining a surface pre-concentration of thiol molecules formed by the enzymatic reaction of labeled antibody.
INTRODUCTION The development of a highly sensitive measurement system for detecting trace levels of disease markers is important for the early diagnosis of fatal disorders. The enzyme linked immunosorbent assay (ELISA) is currently one of the most frequently used techniques for determining various disease markers. This is because a relatively large signal can be easily obtained with ELISA by optimizing the incubation time of a labeled enzyme. As a result, a sufficient number of substrates are converted to products as detected molecules owing to the enzymatic reaction. The electrogenerated chemiluminescence- (ECL) based immunoassay technique has recently attracted a lot of attention because it is much more sensitive than the optical absorption method. Therefore, various applications have been reported. The overwhelming majority of ECL immunoassay techniques and all commercially available systems use a tris(2,2′bipyridyl)ruthenium(II) (Ru(bpy)32+) derivative as an ECL luminophore because of its strong luminescence in a neutral solution. Assay results can be obtained by oxidizing the labeled luminophore in the presence of tripropylamine as a coreactant since the ECL emission intensity is proportional to the luminophore concentration. The background level of the ECL immunoassay is known to be extremely low since no excitation light is used. Therefore, the ECL immunoassay is considered to achieve a low detection limit more easily and inexpensively than fluorescence detection. Surface plasmon resonance (SPR) technique also attracted for immunosensor format, and many researchers have reported immunosensors based on the SPR angle shifts caused by the formation of an immuno-complex on an antibody or antigen modified sensing surface. The SPR based immunosensor has advantages as regards bedside monitoring and point-of-care because the method is a rapid, simple, safe and low power technique that does not use any isotopes or fluorescence labels. However, the sensitivity for small molecules is insufficient compared with conventional radio- or fluorescence based detection. With a view to overcoming the problem of sensitivity, several researchers have reported highly sensitive SPR immunosensors realized by introducing signal amplification using a sandwich immunoassay technique with an antigen or
antibody labeled with late
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