Urea biosensors and their application in hemodialysis--perspective of EnFET application.

Parameters such as blood urea nitrogen concentration, normalized protein catabolic rate and Kt/V that are utilized for urea concentration measurements in blood and dialysate for the optimization of the hemodialysis process are reviewed in the paper. Basic methods of urea concentration measurement are described. Urea biosensors of the EnFET type based on the pH-sensitive Si3N4 gate FET and pNH4-sensitive FET with a Siloprene membrane containing nonactine, both of our own construction, are presented. Application of these biosensors for urea concentration measurement in blood and dialysate is described. An experimental microdialysis system with urease in detector solution and a pH-ISFET detector are described. A comparison of two dialysis procedures, with a commercial dialysate an initial of pH 5.6 and with pH kept lowered during the dialysis process applied to rats, is given.