Drug metabolism biosensors:: electrochemical reactivities of cytochrome P450cam immobilised in synthetic vesicular systems

Biosensors containing cytochrome P450(cam) in a didodecyldimethylammonium bromide vesicular system were prepared by cross-linking onto a glassy carbon electrode (GCE) with glutaraldehyde in the presence of bovine serum albumin. Cyclic voltammetric responses of the sensor in air-free buffer solution showed that the sensor exhibited reversible electrochemistry due to direct electron exchange between the haem Fe3+/(2+) redox system and the GCE surface. In air-saturated solution containing camphor, the biosensor gave an irreversible electrocatalytic current which is compatible with the monooxygenation of the substrate. Steady state amperometric experiments with camphor, adamantanone and fenchone were performed with a biosensor prepared by cross-linking P450(cam) with glutaraldehyde onto a Pt disc electrode. The sensor was characterised by fast amperometric responses, attaining steady-state in about 20 s in a cobalt sepulchrate mediated electrochemical system. The kinetic parameters of the biosensor were analysed using the electrochemical Michaelis-Menten equation. The estimated apparent Michaelis-Menten constant, K-m', values for the biosensors were in the range of 1.41-3.9 mM. (C) 1998 Elsevier Science B.V. All rights reserved.