A chitosan-based polyaniline–Au nanocomposite biosensor for determination of cholesterol

Abstract

A polyaniline–gold (PAni–Au) nanocomposite is chemically synthesized and impregnated in a chitosan matrix for immobilization of cholesterol oxidase on an indium tin oxide-coated glass plate for development of cholesterol biosensors. The PAni–Au nanocomposite is characterized for structural and thermal properties. Further the PAni–Au nanocomposite is used for cholesterol oxidase immobilization and linkage is examined by FTIR. The nanocomposite is used to form a modified bioelectrode by immobilizing cholesterol oxidase in the chitosan matrix and examined under an optical microscope for uniformity and morphological studies. A modified bioelectrode (ChOx/PAni–Au–CH/ITO) is used to detect cholesterol by using a voltammetric technique with a redox mediator. The sensor exhibits linearity in a wide range of 50–500 mg dL⁻¹ with a detection limit of 37.89 mg dL⁻¹, a sensitivity of 0.86 μA mg dL⁻¹ and a shelf life of more than 3 weeks when stored at 4 °C. Voltammetric studies have also been carried out with common possible interferents. Responses are recorded to get enzyme–substrate kinetics for the biosensor and found as K_m = 10.84 mg dL⁻¹. The low value of K_m indicates that the prepared nanocomposite facilitates the enzymatic reaction and enzymatic activity. Excellent immobilization and enzyme–substrate reactions show a distinct advantage of this matrix over other matrixes used for cholesterol biosensors. The novelty of the prepared electrode lies in its reusability, higher sensitivity, better shelf life, and accuracy.