Fluorescence immunoassay for HBsAg using a thermal phase separating polymer

A novel fluorescence immunoassay for HBsAg was developed by using poly-N-is opropylacrylamide (PNIP) as an immunoreaction carrier, In sandwich immunoas say, after two steps immunoreaction, PNIP precipitates out of water above a critical temperature of 31 degrees C, enabling a polymer-bound immune comp lex to be separated from the solution, The calibration graph for HBsAg was linear over the range of 0.5-100 mu g/mL with a detection limit of 10 ng/mL . This method combines some advantages of both homogeneous and heterogeneou s immunoassays, and has been applied to determining the HBsAg in human bloo d serum with satisfactory results.