All-electrochemical nanocomposite two-electrode setup for quantification of drugs and study of their electrocatalytical conversion by cytochromes P450

This paper describes the electrochemical behavior and an electrooxidative method for the determination of diclofenac, DF, (2-[(2,6-dichlorophenyl)amino]benzeneaceticacid) and acetaminophen, AC, (N-acetyl-p-aminophenol). Drugs electrochemical oxidation was realized on the surface of graphite-based screen printed electrodes (SPEs) modified with a stable dispersion of multiwalled carbon nanotubes (MWCNTs) in aqueous solutions of an amphiphilic poly(1,2-butadiene)-block-poly(N,N-dimethylaminoethyl methacrylate) diblock copolymer (PB-b-PDMAEMA). The oxidation peak potentials of DF and AC were detected at + 0.53 ± 0.02 V and + 0.35 ± 0.02 V (vs. Ag/AgCl), respectively. The analytical characteristics of electro-oxidation of the drugs on the SPE/(PB-b-PDMAEMA/MWCNTs) constructs were estimated with a detection limit of 35 nM and 40 nM, and a sensitivity of 4.90 mA/M and 2.3 mA/M for DF and AC, respectively. Electro-oxidation of DF and AC was applied as analytical technique for the detection of these pharmaceuticals in their mixtures and in human serum. Further, we demonstrate an approach for the estimation of the enzymatic activity of cytochrome P450 3A4 (CYP3A4) based on the electrochemical oxidation of residual DF used as a model drug. Two separate electrochemical cells were used and each was supplied by a specific electrode. The first one was CYP-sensitive electrode, which contains CYP3A4 immobilized on didodecyldimethylammonium bromide (DDAB) as a CYP3A4 fixing matrix, while another one was our newly developed drug-sensitive electrode. Therefore, drug conversion, which takes place in the first electrochemical cell supplied by CYP-sensitive electrode, can be quantitatively monitored by drug-sensitive electrode by taking aliquots at specified time periods and assaying a residual drug concentration in the second electrochemical cell. Thus, the estimation of kinetic parameters for CYP3A4 catalysis can be carried out.