A cholesterol biosensor based on a bi-enzyme immobilized on conducting poly(thionine) film

A simple and cheap cholesterol biosensor was designed by immobilizing cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) onto a poly(thionine)-modified glassy carbon electrode (GCE/PTH). Being mediated by hydroquinone (HQ), the immobilized HRP exhibited excellent electrocatalytic activity in reducing H2O2, which was produced from cholesterol by the enzymatic reaction of ChOx. The linear detection range for cholesterol was 25–125 μM, with a detection limit (S/N = 3) and a sensitivity of 6.3 μM and 0.18 μA/cm2/μM, respectively, under optimal conditions. The highly reproducible and sensitive GCE/PTH/ChOx/HRP sensor exhibited an interference-free signal for cholesterol detection with excellent recoveries for real sample analysis.