An efficient urea biosensor based on laser ablated ZnO thin film
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An efficient urea biosensor based on laser ablated ZnO thin film Neha Batra1, Monika Tomar2 and Vinay Gupta1 1 Department of Physics and Astrophysics, University of Delhi, Delhi 110007, INDIA 2 Department of Physics, Miranda House, University of Delhi, Delhi 110007, INDIA 1 Email id: [email protected]; [email protected] Contact no: +91 9811563101 ABSTRACT Zinc oxide (ZnO) thin film deposited onto indium tin oxide (ITO) coated Corning glass substrates using pulsed laser deposition (PLD) technique has been used as a matrix for realization of an efficient urea biosensor after immobilization of urease (Urs) enzyme onto the surface of ZnO. The bioelectrode (Urs/ZnO/ITO/glass) is found to be exhibiting an enhanced sensitivity of 22μΑmΜ-1cm-2 towards urea over a wide detection range of 5-200 mg/dl. The relatively low value of Michaelis menten constant (Km= 0.94mM) indicates high affinity of the immobilized urease towards the analyte (urea). The prepared biosensor retains 90% of its activity for more than 10 weeks. The observed enhanced response characteristics of bioelectrode are attributed to the growth of the matrix (highly c-axis oriented ZnO thin film) with desired surface morphology and high electron communication feature. The results confirm the promising application of PLD grown ZnO thin film as an efficient matrix for urea detection. INTRODUCTION Urea [(NH2)2CO] is an end product of nitrogen metabolism and has great significance in clinical chemistry where blood urea level is an indicator of possible kidney malfunction in human body. An increase in urea level in blood (normal range is 15-40mg/dl) and urine causes a number of health concerns including renal failure, urinary tract obstruction, dehydration etc, while reduced level of urea may be responsible for hepatic failure, nephritic syndrome and cachexia. Moreover, urea is widely distributed in nature and its analysis is necessary in food chemistry and environmental monitoring [1-3]. Amongst various methods used for urea detection, biosensors have attracted interest of research community due to their high selectivity, sensitivity, portability, fast response speed etc. A biosensor is an analytical device based on direct spatial coupling of a biologically active compound (e.g. Enzymes, antibodies, microorganisms etc.) with a compatible transducer, which converts the biochemical signal into quantifiable electrical signal. The enzymes are highly specific and therefore find extensive application in biosensors for the detection of a specific analyte. The most important aspect of a biosensor design include the selection of an appropriate matrix upon which biomolecules are to be immobilized and the binding chemistry be such that the biological activity and stability of the biomolecules is retained [4]. To achieve this goal, nanostructured semiconducting metal oxides are attracting considerable interest in bio-analytical area as they possess high surface area, nontoxicity, ease of fabrication, good optical transmission in visible region, chemical stability etc.
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