Development of a Urea Potentiometric Biosensor Based on Gelatin-Immobilized Urease

Abstract

Urease (typeIII) purified from Jack bean was immobilized on gelatin beads via cross-linking with glutaraldehyde. The maximum immobilization (70.82%) was observed with a half-life of 385 days and there was practical stability for over a period of 50 days. These beads could be reused more than 10 times (with 24 h intervals) without much loss of enzyme activity (i.e. less than 12%). The immobilized beads were used for the preparation of a new urea biosensor developed from the potentiometric pH glass electrode and the reference calomel electrode with major advantages such as long term operational and storage stability, response time and linear range. The beads, as well as the biosensor, were used to analyse the urea content in clinical samples from the local pathology laboratory. The results obtained with the biosensor were similar to those obtained with the various commonly employed biochemical/autoanalyzer^® methods. These immobilization studies also have a potential role in haemodialysis
machines that are used to maintain the urea level in kidney patients and in the construction of a portable or wearable kidney.