Detection of trace antigens in body fluid using ultrasensitive immunoassay by laser induced photothermal spectroscopy and its application to the forensic medical tests

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We developed several new immunoassays based on highly sensitive detection by a photo-thermal conversion system, in place of conventional absorption spectrophotometric detectors. They are an immunobinding assay using photothermal deflection spectroscopy, a capillary zone electrophoresis (CZE) which uses capillary vibration induced by laser (CVL) and a photothermal microscopy. The new feature of these methods is the use of colloidal gold which is feasible to laser photothermal method as a labeling material.Using these newly developed immunoassay methods, we could detect and quantitate trace antigens in human sera, i.e.carcinoembryonic antigen, IgE,Lewis antigens. We could also detect human chorionic gonadotropin, and some drugs, methamphetamine in urine and antibiotics in a epithelial cell of renal tubules.These assay methods are sensitive and easy enough to detect trace substances in samples. Therefore, these new immunoassays are applicable to forensic medical test and/or clinical diagnosis.