Amperometric determination of choline released from rat submandibular gland acinar cells using a choline oxidase biosensor

A choline (CHO) biosensor based on the determination of H2O2 generated at the electrode surface by the enzyme choline oxidase (CHOx) was developed. The biosensor consisted of CHOx retained onto a horseradish peroxidase (HRP) immobilized solid carbon paste electrode (sCPE). The HRPsCPE contained the molecule phenothiazine as redox mediator and CHOx was physically retained on the electrode surface using a dialysis membrane. Several parameters have been studied such as, mediator amount, influence of applied potential, etc. The CHO measurements were performed in 0.1 M phosphate buffer, pH 7.4. Amperometric detection of CHO was realized at an applied potential of 0.0 mV vs Ag/AgCl. The response is linear over the concentration range 5.0 x 10(-7)-7.0 x 10(-5) M, with a detection limit of 1.0 x 10(-7) M. This biosensor was used to detect choline released from phosphatidylcholine (PC) by phospholipase D (PLD) in isolated rat salivary gland cells stimulated by a purinergic agonist (ATP). (C) 2002 Elsevier Science B.V. All rights reserved.