Amperometric biosensor for determining human salivary phosphate

An amperometric biosensor was constructed for analysis of human salivary phosphate without sample pretreatment. The biosensor was constructed by immobilizing pyruvate oxidase (PyOD) on a screen-printed electrode. The presence of phosphate in the sample causes the enzymatic generation of hydrogen peroxide (H2O2), which was monitored by a potentiostat and was in proportion to the concentration of human salivary phosphate. The sensor shows response within 2 s after the addition of standard solution or sample and has a short recovery time (2 min). The time required for one measurement using this phosphate biosensor was 4 min, which was faster than the time required using a commercial phosphate testing kit (10 min). The sensor has a linear range from 7.5 to 625 mu M phosphate with a detection limit of 3.6 mu M. A total of 50 salivary samples were collected for the determination of phosphate. A good level of agreement (R-2 = 0.9646) was found between a commercial phosphate testing kit and the phosphate sensor. This sensor maintained a high working stability (>85%) after 12 h operation and required only a simple operation procedure. The amperometric biosensor using PyOD is a simple and accurate tool for rapid determinations of human salivary phosphate, and it explores the application of biosensors in oral and dental research and diagnosis. (C) 2005 Elsevier Inc. All rights reserved.