The fixation of anti-HBsAg on plastic surfaces

Serum samples were found to be capable of desorbing as much as 40% of the antibody to hepatitis B surface antigen (anti-HBsAg) adsorbed to plastic surfaces. This previously unreported loss could affect the accuracy of the assay, so chemical fixation was examined as a means for preventing antibody desorption during a 'sandwich' radioimmunoassay for HBsAg. Methods for fixing the anti-HBsAg were developed with glutaraldehyde and ethylchloroformate. Both methods prevented antibody desorption from polyvinylchloride and polystyrene without affecting immunoreactivity in radioimmunoassay. A combined glutaraldehyde-ethylchloroformate method resulted in stronger fixation that fully resisted the sera that caused the greatest desorption. It was found that only polymerized glutaraldehyde fixed anti-HBsAg to plastic; the monomer was ineffective. Anti-HBsAg fixed microtiter plates could be stored for at least 4 weeks without loss of sensitivity in radioimmunoassays. These methods could be adapted for use in other assays where the prevention of protein desorption from the solid phase is an important consideration.