Abstract:

Indirect competitive ELISA methods were developed based on the high-titer antibody and the dilution ratio of goat anti-rabbit-HRP, competition time and the pH of PBS solution were optimized. The IC50 of optimized indirect compete ELISA for dexamethasone, betamethasone and flumethasone were 2.66, 7.36, 6.12 ng/ml, respectively. The group selection of three antibodies was accessed by detecting their cross-reactivities. The results showed that the anti-dexamethasone antiboidy was the best suitable for group selection and the cross-reactivity toward flumethasone, betamethasone, riacinolone and predinisolon was up to 120%, 73%, 37%, predinisolone 21% while the cross activity towards several natural glucocorticoids was lower than 0.1%. The recoveries were detected by spiking four concentrations (0.375, 0.75, 1.5 ng/ml and 3.0 ng/ml) of DEX in chicken muscle tissue and the results indicated that the recoveries were between 61.3% and 80.3% and the coefficients of variation were lower than 15%. The ELISA method and LC-MS method were applied to analyze the real samples, and high correlation was observed between the two methods.

Key words: corticosteroids, ELISA, detection, class specific antibody, group-selection