Iron oxide-chitosan nanobiocomposite for urea sensor

Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide (ITO) coated glass plate via physical adsorption for urea detection. The magnitude of magnetization (60.9 emu/g) of Fe3O4 nanoparticles (∼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 (Km, 0.56 mM) indicates high affinity of enzymes (Ur and GLDH) for urea detection.