Trienzymatic biosensor for the determination of inorganic phosphate

A biosensor for phosphate detection has been fabricated using a mixture of maltose phosphorylase (MP), mutarotase (MR), and glucose oxidase (GOD) entr apped in an inorganic laponite clay. The response of the biosensors to phos phate and glucose additions was measured by potentiostating the modified el ectrodes at 0.6 V versus Ag/AgCl in order to oxidize the enzymatically gene rated hydrogen peroxide. The bioelectrochemical response of the biosensor f or phosphate detection is strongly affected by the ratio of each enzyme in the enzyme-clay mixture. The optimum pH and temperature of the biosensor ar e 6.5 and 40 degreesC. Under these optimum conditions, the phosphate sensit ivity and the linear range are 52.4 mA M-1 cm(-2) and 1-50 muM, respectivel y. The maximum response current of the biosensor is stable at least for 2 w eeks, a 30% decay of initial activity was observed after 42 days at 4 degre esC. (C) 2001 Elsevier Science B.V. All rights reserved.