An electrochemical metalloimmunoassay based on a colloidal gold label

A novel, sensitive electrochemical immunoassay has been developed using a c olloidal gold label that, after oxidative gold metal dissolution in an acid ic solution, was indirectly determined by anodic stripping voltammetry (ASV ) at a single-use carbon-based screen-printed electrode (SPE), The use of d isposable electrodes allows for simplified measurement in 35 muL of solutio n. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) and a concentration as low as 3 x 10(-12) M wa s determined, which is competitive with colorimetric ELISA or with immunoas says based on fluorescent europium chelate labels, The high performance of the method is related to the sensitive ASV determination of gold(III) at a SPE (detection limit of 5 x 10(-9) M) and to the release of a large number of gold(III) ions from each gold particle anchored on the immunocomplex (e. g., 1.7 x 10(5) gold atoms are theoretically contained in a 18-nm spherical gold particle).