An Amperometric Cytochrome P450-2D6 Biosensor System for the Detection of the Selective Serotonin Reuptake Inhibitors (SSRIs) Paroxetine and Fluvoxamine

Abstract

Paroxetine is the second most prescribed selective serotonin reuptake inhibitor (SSRI) antidepressant drug, characterized by extensive inter-individual variation in steady state plasma concentrations resulting in drug toxicity amongst patinets. A nanopolymeric biosensor for studying the biotransformation of paroxetine is presented. The bioelectrode system consists of cytochrome P450-2D6 enzyme encapsulated in nanotubular poly (8-anilino-1-napthalene sulphonic acid) electrochemically deposited on gold. The biosensing procedure involved the determination of the extent of modulation of fluvoxamine responses to the P450-2D6 enzyme electrode after incubation in paroxetine standard solutions. Paroxetine inhibited the activity of cytochrome P450-2D6 (CYP2D6) resulting in a decrease in the fluvoxamine signal of the biosensor. The biosensor gave a linear analytical response for the paroxetine in the interval 0.005 and 0.05 μM, with a detection limit of 0.002 μM and a response time of 30 s. Electrochemical Michaelis–Menten kinetics of the reversible competitive inhibition of the fluvoxamine responses of the biosensor by 0, 0.05 and 0.1 μM paroxetine gave apparent Michaelis–Menten constant (KMapp) values of 1.00 μM, 1.11 μM and 1.25 μM, respectively. The corresponding value for the maximum response, IMAX was 0.02 A. The dissociation constant, KI, value evaluated from Dixon analysis of the paroxetine modulation data was estimated to be-0.02 μM while Cornish-Bowden analysis confirmed the competitive inhibitory characteristics of the enzyme.