Fabrication and kinetic modeling of cytochrome P4502D6 amperometric biosensors for serotonin reuptake inhibitors

Abstract

An amperometric biosensor was prepared by in situ deposition of cytochrome P4502D6 (CYP2D6, P4502D6) enzyme on a polyaniline (PANI)-doped glassy carbon electrode. The PANI film was electrochemically deposited on the electrode at 100 mV s-1 against Ag/AgCl. Cyclic voltammetric characterisation of the PANI film in 1 M HCl solution showed two distinct redox peaks, which prove that the PANI film was electroactive and exhibited fast reversible electrochemistry. The surface concentration and film thickness of the adsorbed electroactive species was estimated to be 1.85 x 10 -7 mol cm -2 and approximately 16 nm, respectively. Cytochrome P4502D6 was electrostatically immobilised onto the surface of the PANI film and cyclic voltammetry was used to monitor the serotonin reuptake inhibitors (fluoxetine, fluvoxamine and citalopram) in phosphate buffer solution. Fluoxetine was found to be a substrate of CYP2D6 at low concentrations but inhibits enzyme activity at high concentrations; this was consistent with uncompetitive substrate inhibition kinetics. Thus PANI-mediated electrochemistry can be used to observe monooxygenation reaction of CYP2D6.