An electrochemical immunosensor for anti-T. cruzi IgM antibodies, a biomarker for congenital Chagas disease, using a screen-printed electrode modified with gold nanoparticles and functionalized with shed acute phase antigen

Abstract

The authors describe a sandwich immunosensor for anti-IgM T. cruzi-specific antibodies which are a biomarker for congenital Chagas disease (CCD). A screen-printed carbon electrode (SPCE) was modified with gold nanoparticles (AuNPs) and then functionalized with recombinant shed acute phase antigen (SAPA). The AuNPs/SPCE was characterized by scanning electron microscopy, cyclic voltammetry, and X-ray diffraction. The AuNPs provide an increased active surface area, high conductivity, and improved electrocatalytic characteristics, this resulting in a significant improvement of the detection limit. Following interaction between immobilized SAPA and the target antibodies in the serum sample, secondary antibody (an anti-human IgM-HRP conjugate) and solutions of H2O2 and 4-tert-butylcatechol were added and the enzymatic product was detected at −100 mV (vs. Ag/SPCE). The resulting current was proportional to the anti-T. cruzi IgM antibodies present in the sample and showed a linear trend from 10 to 200 ng mL−1 (R = 0.998). The detection limit was 3.03 ng mL−1. These values demonstrate that this electrochemical immunosensor can be used as an alternative serological method for diagnosis of congenital Chagas disease.