Application of the charged polymeric materials as additional permselective membranes for improvement of the performance characteristics of urea-sensitive ENFETs 2. Urea determination in blood serum

An improved urea-sensitive biosensor based on pH-sensitive field-effect transistors was 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 the top of enzymatic and reference membranes of urea biosensors by a spin-coating process. It was shown that the presence of such permselective additional layers removes the non-specific response coming from high concentration of proteins and other components in real biological samples and furthermore increases the biosensor stability. The use of enzymatic field-effect transistors coated with additional membranes allows analysis of urea in serum with increased sensitivity and accuracy.