B‐type natriuretic peptide (BNP) is a selective biomarker for cardiac diagnosis and prognosis of patients with cardiac insufficiency or heart failure, which means the pump function of cardiac muscle is reduced. A pseudocapacitive immunosensor was developed based on faradaic currents generated by a reduction‐reaction with a metallocyanine modified‐carbon nanotube surface. This technique is based on changes in interface by antigen‐antibody interactions, which perturbs the dependent‐diffusion potential reducing the charge transfers proportionally to the BNP captured. This new concept allows new perspectives for point‐of‐care tests since it is simpler and faster to manage with direct measurements of samples than conventional immunosensors.

An electrochemical immunosensor based on a nanohybrid film of carboxylated polypyrrole and amine nanoclay was developed for label-free detection of the human cardiac troponin T (cTnT). The nanohybrid film was formed in situ on the surface of the glassy carbon electrode, followed by the covalent immobilization of anti-troponin T antibodies by glutaraldehyde. Morphological and chemical characterizations of the nanohybrid film were performed by scanning electron microscopy and Fourier-transform infrared spectroscopy. Under the optimized conditions, a calibration curve for cTnT in spiked serum was obtained by square wave voltammetry, and a low limit of detection and quantification was achieved (0.35 and 1.05 pg mL−1, respectively). This was the first time that this type of nanohybrid film was used in the development of an immunosensor for cTnT that proved to be a simple and efficient strategy for the manufacture of a label-free electrochemical device that could be applied in the diagnosis of acute myocardial infarction.