How an improved immunoassay sensitivity can be achieved by gamma irradiation: modification, application and characterization of polystyrene surface for anti HIV-1 ELISA.

Polystyrene microtitre plates modified by (60)Co gamma-ray irradiation were used in an indirect enzyme-linked immunosorbent assay (ELISA) for detection of anti-human immunodeficiency virus type 1 (anti HIV-1). The plates with 9 kGy (optimum dose) irradiation showed 2-5-fold higher detection sensitivity in serodiagnosis tests compared to untreated ones, and a 3-fold lower enzyme concentration than the control used was still detectable. Adsorption/desorption experiment results, atomic force microscopy (AFM) images, and X-ray photoelectron spectroscopy (XPS) analysis provide the reason for this improvement. The oxidized surface formed during irradiation presented much more binding affinity for coating antigens and could adsorb a larger amount (1.5-3-fold) of protein uniformly.