Gold nanoparticles-reduced graphene oxide based electrochemical immunosensor for the cardiac biomarker myoglobin

A composite consisting of gold nanoparticles and reduced graphene oxide (AuNPs@rGO) was electrochemically prepared in-situ on a screen printed electrode (SPE) which then was used as an immunosensor for the cardiac biomarker myoglobin. The nanocomposite was characterized by transmission electron microscopy (TEM, scanning electron microscopy (SEM), atomic force microscopy, FTIR and electrochemical impedance spectroscopy. For FTIR, TEM and SEM, the deposition was done on indium tin oxide coated glass plates. The immunosensor was obtained by immobilization of in-house generated antibody against cardiac myoglobin on the electrode surface. The immunosensing response was monitored using differential pulse voltammetry, which showed a reduction peak at similar to-0.5 V (vs. Ag/AgCl). The reduction peak arises from the reduction of iron moiety present in the heme group of myoglobin. The immunosensor exhibited dynamic linearity range from 1 ng.mL(-1) to 1400 ng.mL(-1) with the detection limit of similar to 0.67 ng.mL(-1) for cardiac myoglobin. The obtained result was almost eight times better (in terms of detection limit) than that obtained with ELISA tests (with detection limit of similar to 4 ng.mL(-1)) using the same antibodies. The immunosensor was applied to analyze spiked serum samples also.