Polymer nanoparticles as fluorescent labels in a fluoroimmunoassay for human chorionic gonadotropin

A sensitive fluoroimmunoassay (FIA) was developed for the determination of human chorionic gonadotropin (beta-HCG). It is based on fluorescent polymer nanoparticles (PFNPs) coated with anti-beta-HCG monoclonal antibodies in a sandwich type of fluoroimmunoassay. The PFNPs were synthesized by precipitation polymerization using methacrylic acid (MAA) as the monomer, trimethylolpropane trimethacrylate as the cross-linker, azobisisobutyronitrile as the radical initiator, and fluorescein as the fluorophore. Anti-beta-HCG monoclonal antibody was labeled with the PFNPs and then used in a FIA of beta-HCG in human serum samples using low-fluorescent transparent 96-well microtiter plates. The calibration graph for beta-HCG is linear over the range from 1.25 to 300 mIU mL(-1) with a detection limit of 0.3 mIU mL(-1) (3 sigma). The relative standard deviation for seven parallel measurements of 10 mIU mL(-1) of beta-HCG is 3.8%. The method has the specificity of an immunoassay and the sensitivity of fluorescent nanoparticle label technology.