Amperometric magnetoimmunoassay for the determination of lipoprotein(a)

Abstract

A highly sensitive amperometric magnetoimmunoassay for rapid determination of lipoprotein(a) (Lp(a)), an important predictor of cardiovascular disease risk, in human serum, is described. It uses a sandwich configuration involving selective capture antibody [antiLp(a)] and biotinylated detector antibody [biotin-antiLp(a)], and a streptavidin-HRP conjugate on carboxy-modified magnetic beads (HOOC-MBs). The resulting MBs bearing the sandwiched immunoconjugates were captured by a magnet placed under the working electrode surface of a disposable screen-printed carbon electrode and the extent of the affinity reaction was monitored amperometrically at −0.20 V (vs a silver pseudo-reference electrode) in the presence of hydroquinone as an electron transfer mediator and upon addition of H2O2 as the enzyme substrate. The method exhibited a wide linear response range (from 0.01 to 0.5 μg mL−1), a detection limit of 4 ng mL−1, and an excellent selectivity over other serum components. The utility of the immunoassay was demonstrated by analyzing a reference serum containing a certified quantity of Lp(a). The performance of this magnetoimmunoassay compares favorably to that of an integrated amperometric immunoassay described earlier.