Abstract
Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tinoxide (ITO) coated glass plate via physical adsorption for urea detection. The magnitude of magnetization (60.9 emu/g) of Fe3O4 nanoparticles (similar to 22 nm) estimated using vibrating sample magnetometer (VSM) indicates superparamagnetic behaviour. It is shown that presence of Fe3O4 nanoparticles results in increased active surface area of CH-Fe3O4 nanobiocomposite for immobilization of enzymes (Ur and GLDH), enhanced electron transfer and increased shelf-life of nanobiocomposite electrode. Differential Pulse voltammetry (DPV) studies show that Ur-GLDH/CH-Fe3O4/ITO bioelectrode is found to be sensitive in the 5-100 mg/dL urea concentration range and can detect as low as 0.5 mg/dL. A relatively low value of Michaelis-Menten constant (K-m, 0.56 mM) indicates high affinity of enzymes (Ur and GLDH) for Urea detection. (C) 2009 Elsevier B.V. All rights reserved.