Nanostructured iron oxide platform for impedimetric cholesterol detection

A nanostructured iron oxide (NanoFe₃O₄, particle size ca. 25 nm and roughness ca. 21 nm) film deposited onto a hydrolyzed indium-tin-oxide (ITO) coated glass plate has been used to immobilize cholesterol oxidase (ChOx) to fabricate an impedimetric cholesterol sensor. Electrochemical studies reveal that surface charged Fe₃O₄ nanoparticles provide better conformation for ChOx loading resulting in enhanced electron transfer between ChOx and the electrode. Impedimetric response studies of the ChOx/NanoFe₃O₄/ITO bioelectrode exhibit improved linearity (2.5 -400 mg/dL), low detection limit (0.25 mg/dL), fast response time (25 s), high sensitivity (86 Ω/mg dL^-1/cm^-2) and a low value of the Michaelis-Menten constant (K_m, 0.8 mg/dL) with a regression coefficient of 0.997.