Study of Drug Metabolism by Xanthine Oxidase

In this work, we report the studies of drug metabolism by xanthine oxidase (XOD) with electrochemical techniques. Firstly, a pair of stable, well-defined and quasi-reversible oxidation/reduction peaks is obtained with the formal potential at −413.1 mV (vs. SCE) after embedding XOD in salmon sperm DNA membrane on the surface of pyrolytic graphite electrode. Then, a new steady peak can be observed at −730 mV (vs. SCE) upon the addition of 6-mercaptopurine (6-MP) to the electrochemical system, indicating the metabolism of 6-MP by XOD. Furthermore, the chronoamperometric response shows that the current of the catalytic peak located at −730 mV increases with addition of 6-MP in a concentration-dependent manner, and the increase of the chronoamperometric current can be inhibited by an XOD inhibitor, quercetin. Therefore, our results prove that XOD/DNA modified electrode can be efficiently used to study the metabolism of 6-MP, which may provide a convenient approach for in vitro studies on enzyme-catalyzed drug metabolism

Xanthine oxidase modified glassy carbon paste electrode

Glassy carbon paste electrode based on xanthine oxidase (XO) was developed for the determination of xanthine (X). The biosensor employs the amperometric detection of hydrogen peroxide evaluated by the enzymatic reaction catalyzed by XO immobilizing in the glassy carbon paste material. The optimum operational conditions for the biosensor were investigated and the system was calibrated for both hypoxanthine and xanthine, respectively. A linearity for the biosensor was obtained in concentration range between 5.0 × -10 -7-4.0 × -10 -5 M xanthine and 2.0 × -10 -5-8.0 × -10 -5 M hypoxanthine with detection limits of 1.0 × -10 -7 and 5.3 × -10 -6 M, respectively. Furthermore, as well as optimization of enzyme amount, sample application and accuracy were also searched. © 2004 Elsevier B.V. All rights reserved

Laccase biosensors based on mercury thin film electrode

PubMed ID: 16317963A biosensor was developed by immobilizing laccase onto mercury thin film electrode (MTFE) by means of gelatin that is then crosslinked with glutaraldehyde. Mercury thin film (MTF) was deposited onto glassy carbon electrode (GCE) and the obtained biosensor was utilized for the determination of phenolic compounds. The measurement was based on the amperometric detection of oxygen consumption in relation to analyte oxidation. The optimum experimental conditions for the biosensor were investigated and the system was calibrated for both catechol and phenol. A linear relationship between sensor responses and analyte concentrations was obtained in concentration range between 0.5 × 10-6-5.0 × 10-6 M for catechol and 2.5 × 10-6-2.0 × 10-6 M for phenol, respectively. Mercury thin film was also formed onto the surface of screen printed graphite electrodes and applied for the catechol detection. The linearity was observed in concentration range between 2.5 × 10-6-3.0 × 10 -5 M. Copyright © Taylor & Francis, Inc