Gamma irradiation as a substitute for H2O2 in peroxidase-labelled enzyme immunoassays

The ability of gamma irradiation to substitute for H2O2 in peroxidase-labelled enzyme immunoassays was investigated. Colouring of TMB (3,3',5,5'-tetramethylbenzidine), ABTS [2,2'-azino-di(3-ethylbenzthiazoline-6-sulphonic acid)], and OPD (o-phenylenediamine) was produced with doses of 10 and 20 Gy. Addition of superoxide dismutase enhanced TMB and ABTS, and inhibited OPD. The reaction was terminated when the irradiation was stopped. The use of denaturing compounds to stop the reaction was unnecessary and coated antigens could be re-used for a second immunoassay.