Amperometric cholesterol biosensors based on carbon nanotube–chitosan–platinum–cholesterol oxidase nanobiocomposite

A highly sensitive and fast responsed biosensor was successfully fabricated in this work. Platinum nanoparticles were electrochemically deposited in multiwalled carbon nanotube (MWCNT)–chitosan matrix by a cyclic voltammetry method. A Pt(IV) complex was reduced to Pt on the surface of MWCNTs. The Pt nanoparticles in the MWCNT–chitosan film were identified with transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The doped Pt nanoparticles demonstrate the abilities to electrocatalyze the oxidation of hydrogen peroxide and substantially raise the response current. The results indicated that the Pt nanoparticles exhibited efficiently electrocatalytic activity. The influence of enzyme loading within the MWCNT–chitosan–Pt–cholesterol oxidase nanobiocomposite was explored to optimize the electroanalytical performance of the cholesterol biosensor. The optimized cholesterol biosensor shows a sensitivity of 0.044 A M−1 cm−2 and a response time of about 8 s. No response currents were observed at the MWCNT–chitosan–Pt–cholesterol oxidase nanobiocomposite modified electrode after the additions of 100 μM glucose and 1 μM ascorbic acid to 100 μM cholesterol in 0.1 M phosphate buffer solution (pH 7) in the interference study. The prepared cholesterol biosensor retained 60% of initial activity after 7 days when stored in 0.1 M phosphate buffer solution at 4 °C.