Electrochemical Behavior of Glassy Carbon Electrodes Modified with Electropolymerized Film of N,N′-bis (2-thienylmethylene)-1,X-diaminobenzene toward Homovanillic Acid and 4-Hydroxyphenylacetic Acid

This study evaluates different electrochemical behaviors of modified glassy carbon electrodes (GCEs) for detecting urinary biomarkers related to breast cancer, namely homovanillic acid (HVA) and 4-hydroxyphenylacetic acid (4HPA). The analysis was performed in the presence of common urinary interferents, creatinine and urea. Modification of bare GCEs was done through the electropolymerization of N,N′-bis (2-thienylmethylene)-1,X-diaminobenzene (X = 2, 3, 4) isomers, so-called BTMD. The formation and characteristics of these polymeric layers were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Differential pulse voltammetry (DPV) was used to measure responses of the electrodes  to HVA and 4HPA, assessing their sensitivity and selectivity. Results showed that the developed electrodes effectively detected both biomarkers, with peak currents increasing proportionally to biomarker concentrations and minimal interference from creatinine and urea. The modified electrodes exhibited better linearity at higher concentrations; however, saturation was observed for 4HPA at high concentrations with the p-BTMD/GCE. Each electrode displayed unique peak current, potential, and response profiles, highlighting their promise for cross-reactive sensing systems, such as electronic tongues, to analyze complex matrices such as urine.