Multi-walled carbon nanotubes/sol–gel-derived silica/chitosan nanobiocomposite for total cholesterol sensor

Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) have been immobilized via glutaraldehyde as a cross-linker onto sol–gel-derived silica (SiO2)/chitosan (CHIT)/multi-walled carbon nanotubes (MWCNT)-based nanobiocomposite film deposited onto indium-tin-oxide (ITO) glass for estimation of esterified cholesterol. The ChEt–ChOx/MWCNT/SiO2–CHIT/ITO bioelectrode characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and electrochemical techniques and shows response time of 10 s, linearity as 10–500 mg/dL for esterified cholesterol (cholesterol oleate), sensitivity as 3.8 μA/mM and shelf-life of about 10 weeks under refrigerated conditions. The value of Michaelis–Menten constant (Km) estimated as 0.052 mM using Lineweaver–Burke plot indicates high affinity of ChEt and ChOx to cholesterol oleate. Attempts have been made to utilize this electrode for estimation of total cholesterol in blood serum samples.