Low-cost immunosensing approach for Chagas disease: exploiting modified pencil graphite electrodes with polymer films

Chagas disease (CD) is an endemic disease in America that affects impoverished communities. It is caused by the protozoan Trypanosoma cruzi, which is transmitted by triatomine insects known as kissing bugs. Considering the treatment effectiveness, early detection of the disease is crucial to control its impact on public health. In this study, we developed a low-cost immunosensor in which pencil graphite electrodes (PGEs) were functionalized by electropolymerization of monomers 2-aminobenzamide (2AB), 4-aminobenzoic acid (4ABA), 4-hydroxybenzoic acid (4HBA), 4-hydroxyphenylacetic acid (4HPA), and 4-aminophenylacetic acid (4APA). Electrochemical and morphological studies confirmed the successful modification of PGEs for all investigated compounds. The bioreceptor IBMP 8.1, a recombinant antigen, was immobilized on each functionalized platform. Electrochemical impedance spectroscopy identified poly(4HPA) as the most effective material for functionalizing PGEs and consequently recognizing the anti-T. cruzi antibodies, leading to their selection for subsequent optimization of the transducer. The use of silver nanoparticles to improve sensitivity was also investigated. The conditions for immobilizing the antigen, blocking the protein, and the dilution and response time of the device were optimized. Cross-reactivity studies with other diseases have demonstrated the high specificity of immunosensors. Reproducibility and repeatability tests showed relative standard deviation values of 7.3% (± 2.4) and 5.6% (± 1.8), respectively, for the 20 sensors. Furthermore, the stability over a three-month period (n = 20) showed a 32% decrease in response at 25 °C and a 12% decrease at 4 °C. These results indicated the potential of PGE/poly(4HPA) for rapid and accurate CD detection.