Abstract

A label-free electrochemical inmunosensor based on specific antibody immobilization was developed attached to an aminophenylboronic/poly-indole-6-carboxylic acid-modified electrode (APBA/6-PICA/GCE) for detection of the cancer biomarker, prostate-specific antigen (PSA). The optimal conditions for developing a reproducible bioplatform with excellent stability were determined, focusing on time and incubation temperature. Guided antibody immobilization was carried out using APBA and shown to improve the antigen-antibody affinity. Following the intrinsic redox response of 6-PICA, which corresponds to the electrode doping-undoping charge transfer process, this was chosen as an analytical electrochemical signal using square wave voltammetry (SWV). Cyclic voltammetry, electrochemical impedance spectroscopy and SWV were used in the characterization in the step-by-step optimal construction of the immunosensor and PSA detection. The calibration curve shows a linear range between 0.50 and 100.0 ng·mL−1, with a limit of detection (LOD) of 0.11 ng·mL−1, and a limit of quantification (LOQ) of 0.33 ng·mL−1, respectively. Also, an affinity constant (Ka) between specific monoclonal antibody and PSA was determined at 6.37·109 M−1. These analytical quality parameters propose that the bioplatform can be used to detect PSA concentrations within clinically relevant levels.