The Study Of The Electrochemical Immunoassay Method Based On The Colloidal Gold Labeling

The antigen or antibody was labeled with the metal chelated compounds in the former methods of metal immunoassay. But each protein molecule could only be labeled with several metal chelated compounds so that the accurate determination couldn't be achieved. Based on this situation, the paper proposed a novel immunoassay with the antigen or antibody labeled with the colloidal gold, and described this kind of immunoassay from the four parts that are shown in the following:1. The recent progress of applications of colloidal gold and the study of immunoassays are reviewed.2. A silver-enhanced colloidal gold metalloimmunoassay has been proposed for the determination of Schistosoma japonium antibody (SjAb) in rabbit serum. The adult worm antigen of Schistosoma japonium (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 the SjAb, followed by the silver enhancement process and the dissolution of silver metal atoms in an acidic solution, and the determination of dissolved silver ions by the anodic stripping voltammetry (ASV) at a glassy-carbon electrode. A detection limit as low as 3.0ng/ml SjAb was achieved, which was better than the piezoelectric body acoustic wave sensor (detection limit of 7.2 g/ml) and the renewable amperometric immunosensor (detection limit of 0.36g/ml). Rabbit serum samples with varying infection degrees were analyzed, and the results demonstrated that the proposed method meets the requirement of clinical analysis.3. An anodic stripping immunoassay based on gold label has been developed. The immunoreaction is performed in a polystyrene microwellusing the sandwich format. Rabbit anti-human immunoglobulin G (IgG) antibodies are adsorbed passively on the walls of a polystyrene microwell. The IgG analyte is first captured by the rabbit anti-human antibody and then sandwiched by a colloidal gold-labeled goat anti-human IgG antibody. The subsequent interaction with the immunocomplex consisting of the colloidal gold-labeled goat anti-human IgG antibody and the colloidal gold-labeled rabbit anti-goat IgG secondary antibody results in the adsorption of a large amount of colloidal gold onto the walls of a polystyrene microwell which, after gold metal dissolution in an appropriate solution, is determined by anodic stripping voltammetry (ASV) at a carbon-paste electrode. The influence of some immunoassay conditions upon the anodic stripping peak current is examined and optimized. The anodic stripping peak current depended linearly on the logarithm of IgG concentration over the range of 1.1ng/mL to 1143ng/mL and a detection limit as low as 1ng/mL is achieved. The anodic stripping immunoassay is applied to the determination of IgG concentration in human serum with satisfactory results.4. An anodic stripping immunoassay based on gold label has been developed to determine IgA concentration in human serum. The immunoreaction is performed in a polystyrene microwell in the same way. Rabbit anti-human immunoglobulin A (IgA) antibodies are adsorbed passively on the walls of a polystyrene microwell. The IgA analyte is first captured by the rabbit anti-human antibody and then sandwiched by a colloidal gold-labeled goat anti-human IgA antibody. The subsequent interaction with the immunocomplex consisting of the colloidal gold-labeled goat anti-human IgA antibody and the colloidal gold-labeled rabbit anti-goat secondary antibody result in the adsorption of a large amount of colloidal gold onto the walls of a polystyrene microwell which, after gold metal dissolution in an appropriate solution, is determined by anodic stripping voltammetry (ASV) at a carbon-paste electrode. The...