Silver-enhanced colloidal gold metalloimmunoassay for Schistosoma japonicum antibody detection

A silver-enhanced colloidal gold metalloimmunoassay has been proposed for the determination of Schistosoma japonicum antibody (SjAb) in rabbit serum. The adult worm antigen of S. japonicum (SjAg) was adsorbed passively on the walls of a polystyrene microwell and then reacted with the desired SjAb. The colloidal gold-labeled goat anti-rabbit IgG secondary antibody was adsorbed on the walls of the polystyrene microwells through the reaction with SjAb, followed by the silver enhancement process, dissolution of silver metal atoms in an acidic solution, and determination of dissolved silver ions by anodic stripping voltammetry (ASV) at a glassy-carbon electrode. Assay conditions were optimized, including the reaction time of SjAg with SjAb, the interaction of SjAb with the colloidal gold-labeled secondary antibody, the dilution ratio of the colloidal gold-labeled secondary antibody and the silver enhancement time. The integration of the anodic stripping peak current depended linearly on the SjAb logarithmic concentration over the range of 6.4 ng/ml to 100 μg/ml. A detection limit as low as 3.0 ng/ml SjAb was achieved, which was better than the piezoelectric body acoustic wave sensor (detection limit of 7.2 μg/ml) and the renewable amperometric immunosensor (detection limit of 0.36 μg/ml). Rabbit serum samples with various degrees of infection were analyzed, and the results demonstrate that the proposed method meets the requirements of clinical analysis.