摘要
We developed a novel homogeneous immunoassay using photothermal beam deflection (PBD) spectroscopy. Antibody-coated glass beads having a particle size of 50 μm and antibody-coated colloidal gold ultrafine particles 20 nm in size were used, and an immune complex containing colloidal gold particles on antibody-coated glass beads was formed by immunological reaction in solution. An excitation beam was directed from below the sample, and a PBD signal was thus generated was measured. The PBD signal was not affected by nonreacted antibody-coated colloidal gold particles which were suspended in the solution up to the colloidal gold concentration of 0.008%. This result indicates that homogeneous immunoassay is possible. Human α-fetoprotein was assayed to examine the sensitivity of this method, and a detection limit of 0.25 ng/mL was obtained. This was more sensitive by 1 order of magnitude than the latex agglutination method, the conventional homogeneous rapid assay. Some improvements of reagents and techniques can be expected to enhance the sensitivity further. © 1995, American Chemical Society. All rights reserved.