AMPEROMETRIC ENZYME-IMMUNOASSAY FOR URINARY HUMAN SERUM-ALBUMIN USING PLASMA-TREATED MEMBRANE

A partial modification was made to a microporous hydrophobic polypropylene film by water vapour plasma glow discharge treatment. The modified part, a spot 6 mm in diameter, became hydrophilic so that water could penetrate easily. By treating this ''plasma spot membrane'' with octamethylenediamine and glutaraldehyde, a membrane for immobilization of proteins was obtained. As immobilization of the antibody and the immunoreaction could be performed in the limited spot area, only small amounts (10 mul) of reagents and sample were required. Using this plasma spot membrane and a Pt-AgCl electrode, an amperometric enzyme immunoassay system was established for the measurement of urinary human serum albumin. In this system, non-specific adsorption of enzyme-labelled antigen to the membrane was only 4.4% of specific binding. The range of measurement was 0.5-200 mg l-1 of human serum albumin, which is satisfactory for the diagnosis of human kidney function.