Amperometric sandwich immunoassay for determination of myeloperoxidase by using gold nanoparticles encapsulated in graphitized mesoporous carbon.

An ultrasensitive sandwich-type electrochemical immunosensor was developed for the amperometric determination of serum myeloperoxidase (MPO). The method is making use of (a) gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC); and (b) horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab2) immobilized on AuNP@GMC. MPO capture antibody (Ab1) was immobilized on the electrode modified with an AuNP-graphene oxide nanocomposite. The sandwich immunoreaction leads to the formation of the complex composed of Ab1, MPO, and HRP@Ab2. An amplified electrochemical signal is produced by electrocatalytic reduction of H2O2 (at a typical voltage of -0.18 V vs. Ag/AgCl) in the presence of enzymatically oxidized thionine. The peak current of thionine was measured using differential pulse voltammetry. Under optimized steady-state conditions, the reduction peak increases in the 1 to 300 pg.mL-1 MPO concentration range, and the detection limit is 0.1 pg.mL-1 (at S/N = 3). Graphical abstract Schematic presentation of AuNP-GO based sandwich-type electrochemical immunoassay for the determination of myeloperoxidase by using gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC) as a carrier for horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab2).