Immobilization of cholesterol esterase and cholesterol oxidase onto sol–gel films for application to cholesterol biosensor

Cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been covalently immobilized onto tetraethylorthosilicate (TEOS) sol–gel films. The tetraethylorthosilicate sol–gel/ChEt/ChOx enzyme films thus prepared have been characterized using scanning electron microscopic (SEM), UV–vis spectroscopic, Fourier-transform-infrared (FTIR) spectroscopic and amperometric techniques, respectively. The results of photometric measurements carried out on tetraethylorthosilicate sol–gel/ChEt/ChOx reveal thermal stability up to 55 °C, response time as 180 s, linearity up to 780 mg dL−1 (12 mM), shelf life of 1 month, detection limit of 12 mg dL−1 and sensitivity as 5.4 × 10−5 Abs. mg−1 dL−1.