Fluoroimmunoassay for Antigen Based on Fluorescence Resonance Energy Transfer Between Quantum Dots and Gold Nanoparticles

A unique, sensitive, and highly specific fluoroimmunoassay system for antigen detection using quantum dot and gold nanoparticles has been developed. The assay is based on the fluorescence quenching of quantum dots caused by gold nanoparticles coated with antibody. To demonstrate its analytical capabilities, the quantum dots were coated with anti-HBsAg monoclonal antibodies (QDs-MAb1) and gold nanoparticles coated with another anti-HBsAg monoclonal antibodies (GNPs-MAb2) which specifically bound with HBsAg could sandwich the HBsAg captured by the immunoreactions. The sandwich-type immunocomplex was formed and the energy of quantum dots was transferred to gold nanoparticles as they were within a short distance, so that the fluorescence intensity of quantum dots was quenched. The fluorescence intensity of quantum dots at 570 nm was negative linear proportional to HBsAg concentration logarithm. The result showed that the limit of detection of the HBsAg was 0.928 ng/mL. This new system can be extended to detect target molecules with matched antibodies and has broad potential applications in immunoassay and disease diagnosis.