Electrochemical Impedance Biosensor for Chagas Disease Diagnosis in Clinical Samples

Chagas disease (CD) is one of the main neglected tropical diseases, diagnosed mainly by serological tests performed in centralized laboratories, which severely limits the clinical management of the disease in communities with scarce resources. Herein, an electrochemical impedance biosensor for the detection of CD was developed for the first time using a cruzipain-based sensor surface. The protein, highly immunogenic and isolated from Trypanosoma cruzi, was immobilized over the surface of gold disc electrodes modified with 11-mercaptoundecanoic (MUA) and 6-mercapto-1-hexanol (MCH) self-assembled monolayers (SAMs). Reproducible sensor surfaces, yielding 38 ± 3% coverage as measured by Surface Plasmon Resonance, were obtained by amide coupling of 120 μg/mL cruzipain onto 1/10 MUA/MCH SAMs for 30 min. Under optimized operational conditions, the impedimetric immunosensor recognized specific interactions for anti-T. cruzi antibodies in 1/800 diluted human serum patient samples. The charge transfer resistance of the biosensors increases by ∼18% in the presence of the positive samples, whereas the negative samples give rise to a negligible increase of around 6%. An excellent selectivity to clinical samples from patients infected with T. cruzi was obtained. The clear signal difference obtained for positive and negative clinical samples highlights the applicability of the sensors for the point-of-care diagnosis of CD.