Development of colorimetric enzyme-linked immunosorbent assay for human chorionic gonadotropin

The present study demonstrated the development of a solid phase competitive enzyme linked immunosorbent assay (ELISA) for direct estimation of human chorionic gonadotropin (hCG) in serum and urine. Polyclonal antisera raised against the beta- subunit of peak-I hCG was used in the assay. The Peak-IA hCG-penicillinase was used as tracer. The performance of this antiserum and tracer was compared against hCG-beta antisera of NIH, USA and penicillinase conjugated to hCG-beta obtained from NIH, respectively. Almost parallel standard curves were obtained in both cases, suggesting that these antisera and enzyme label have much potential for developing ELISA system. To the anti-rabbit gamma globulin (ARGG) coated polystyrene tubes, standard or serum or urine samples (50 microL), 100 microL of hCG-beta antiserum, 100 microL of peak-I(A) hCG-penicillinase conjugate and 350 microL of assay buffer were incubated at 37 degrees C for 2 hours. Bound enzyme activity was measured using Penicilline V as substrate. In this new strategy, locally available polystyrene tubes were ground from inside and coated with ARGG. The sensitivity of the assay was 17 mIU/mL in urine and 18 mIU/mL in serum. The intra-assay and inter-assay coefficients of variation (CVs) appeared to be within acceptable limits of 10%. The serum and urinary hCG values, obtained by this method, correlated well with those obtained by radioimmunoassay (RIA) r = 0.98 (n = 100 for serum samples; n = 250 for urinary samples).