Application of charged polymeric materials as additional permselective membranes for improvement of the performance characteristics of urea-sensitive enzymatic field effect transistors .1. Determination of urea in model solutions

Urea-sensitive enzymatic field effect transistors (ENFETs) were prepared by cross-linking urease with bovine serum albumin in a saturated glutaraldehyde vapour on the sensor chips. Additional Nafion or PVP (poly(4-vinylpyridine-co-styrene)) membranes were deposited on top of the enzymatic membranes of the urea biosensors by a spin-coating process. It was found that the main characteristics of the obtained urea biosensor, such as the dependence of the sensor response on buffer and salt concentration, the sensitivity to urea concentration and the detection limit, reproducibility and operational stability, can be improved by the use of these different permselective additional membranes. (C) 1997 Elsevier Science S.A.