Surface plasmon immunoassay

The most sensitive existing assays used to determine antibody levels in blood serum samples require a tracer material, e.g., radioisotope, fluorofore, or enzyme, to identify the specific analyte. Surface plasmon spectroscopy has been applied recently as a no-label technique for the assay of specific antibody solutions with the antigen proteins immobilized on a metal surface. It is found that the metal surface configuration originally proposed for the surface plasmon immunoassay (SPI) is unstable and unsuitable for the assay of specific antibodies in a large mixture of proteins such as in a blood serum. Nevertheless, by properly designing the metal surface structure, the SPI can be made an extremely practical device. Preliminary results for the assay of dinitrophenyl (DNP) and keyhole limpet hemocyanin (KLH) antibodies in blood serum samples, indicate that the SPI, in addition to providing a simple and fast measurement, is comparable with existing approaches, such as radioimmunoassy or enzyme-linked immunosorbent assay both in sensitivity and specificity.