Cholesterol biosensor based on cholesterol esterase, cholesterol oxidase and peroxidase immobilized onto conducting polyaniline films

Cholesterol oxidase, cholesterol esterase and peroxidase have been co-immobilized onto electrochemically prepared polyaniline films. These polyaniline–enzyme films characterized using spectroscopic techniques, have been used to fabricate a cholesterol biosensor. This polyaniline-based cholesterol biosensor has a response time of about 240 s, an apparent Km value as 75 mg dl−1 and can be used to estimate cholesterol concentration up to 500 mg dl−1. These polyaniline/cholesterol oxidase/cholesterol esterase films have a detection limit of 25 mg dl−1 with sensitivity of 0.042 μA mg dl−1. The enzyme films were found to be thermally stable up to 48 °C and have a shelf-life of about 6 weeks when stored at 4 °C. The values of the activation energy before and after the critical temperature were found to be 191 and 95.5 kJ mol−1, respectively.