Urea biosensors

A biosensor is an analytical tool that comprises two essential components-an immobilized biocomponent, in intimate contact with a transducer that converts a biological signal into a measurable electrical signal. This review summarizes the studies carried on the development of biosensors for the analysis of urea in different fields of application, the various techniques of immobilization of urease enzyme, the stability and response time characteristics and the transducers used for biosensor development such as pH electrodes, ammonia gas sensing electrodes, ammonium ion-selective electrodes, optical, conductometric and amperometric transducers. Underlying the importance of this study is the fact that urea is toxic above certain concentrations and its continuous real time monitoring in clinical, environmental and food related environments is of utmost interest. The conventional analytical techniques used, although precise, are time consuming and mostly laboratory bound whereas biosensors have the advantages of ease of use, portability and the ability to furnish real time signals. (C) 2008 Elsevier B.V. All rights reserved.