Preparation of pH-sensitive phase separating polymers and its application in immunoassay

The methylmethacrylate-acrylic acid-maleic anhydrate copolymer(MAM) and methacrylic acid-acrylamide-N-acryloxysuccinimide copolymer(MAN) were prepared. These copolymers were conjugated with monoclonal antibody separately and utilized in a novel separation method for enzyme immunoassay. The polymer precipitated out of water below a critical pH, enabling the polymer-bound immune complex to be separated from the solution. However, the MAM-antibody can show phase separation properties in urine, but can not precipitate in serum. The MAN-antibody showed the insoluble form below PH 3.5 and soluble form above pH 4.0. It has been demonstrated to be applicable to determination of antigen by determining HBsAg in serum. Forty-five samples were assayed, and there was a good correlation between the results by this method and ELISA.