RESUMO
This paper reported a new home-made nonpoisonous substrate of horseradish peroxidase(HRP),3,3′,5,5′-tetramethylbenzidine sulphate(TMBS),used in ELISA with the aqueous soluble egg antigen(SEA)as antigen;proved patients'sera as antibo- dy and the antihuman IgG was replaced by protein A conjugate. The optimun condition obtained by orthogonal design was 1.0 millimolarity of TMBS,1.2 millimolarity of H_2O_2,and pH value at 5.0.The best time to stop reaction with H_2SO_4,was 30-60 min after adding substrate TMBS.At the same time,TMB and OPD were used as compared substrates.It showed that the reaction colour of both TMBS and TMB remained much more stable than that of OPD when being exposured in light and oxygen.After the solutions of TMBS and TMB were stored under 4℃ in refrigerator for 60 days,the coefficient of variation among different experiments was less than 10%. The results in detecting specific antibody in sera from 28 patients with proved schistosomiasis also showed that the sensitivity of TMBS was remarkably higher than OPD.It was found that TMBS used in enzyme immunoassay for demonstrating specific antibody was suitable not only for optical density(OD)read by spectrophotometer but also for estimation judged by naked-eye.During TMBS and TMB used in indirect immunoperoxidase method(IIP),the specific antibody in the tissue can be easily dete- cted and located as well.