Electrochemical sensing of ecstasy with electropolymerized molecularly imprinted poly(o-phenylenediamine) polymer on the surface of disposable screen-printed carbon electrodes

This study demonstrates the ability of an electrochemical sensor based on molecularly imprinted polymers (MIPs) to selectively quantify 3,4-methylenedioxymethamphetamine (MDMA), also known as ecstasy, in bio-logical samples. The device was constructed using ortho-phenylenediamine (o-PD) as the MIP's building monomer at the surface of a screen-printed carbon electrode (SPCE). The step-by-step construction of the SPCE-MIP sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Density functional theory (DFT) calculations and modelling were performed not only to understand template-monomer interaction but also to comprehend which possible polymer structure - linear or ramified poly(o-PD) - indeed interacts with the analyte. The prepared sensor worked by directly measuring the MDMA oxidation signal through square-wave voltammetry (SWV) after an incubation period of 10 min. Several parameters were optimized, such as the monomer/template ratio, the number of electropolymerization scanning cycles, and the incubation period, to obtain the best sensing efficiency. Optimized sensors exhibited suitable selectivity, repeatability (2.6%), reproducibility (7.7%) and up to one month of stable response. A linear range up to 0.2 mmol L-1 was found with an r(2) of 0.9990 and a limit of detection (LOD) and quantification (LOQ) of 0.79 and 2.6 mu mol L-1 (0.15 and 0.51 mu g mL(-1)), respectively. The proposed sensor was successfully applied to human blood serum and urine samples, showing its potential for application in medicine and in forensic sciences.