Amperometric Vitamin C Biosensor Based on the Immobilization of Ascorbate Oxidase into the Biocompatible Sandwich-Type Composite Film

Ascorbate oxidase (AO), a biologically active macromolecule, was successfully immobilized into a biocompatible sandwich-type composite film for developing the vitamin C (VC) biosensor, and the content of VC in commercial juices was amperometrically determined. The biocompatible and conducting poly(3,4-ethylenedioxythiophene) composite film and highly stable and selective multiwalled carbon nanotubes –Nafion composite film were prepared as inner and outer films of biosensor. AO molecules were immobilized between these two composite films. The as-fabricated biosensor displayed an excellent bioelectrocatalytic performance towards the oxidation of VC, a fast current response, a low working potential, a high sensitivity, a wide linear range, and a low detection limit. Moreover, the working mechanism of the biosensor was proposed, and its kinetics was also discussed. In addition, the specificity, reproducibility, and feasibility of the as-fabricated biosensor were also evaluated. Good results of the VC determination in commercial juices indicated that the as-fabricated biosensor was a potential candidate for the electrochemical determination of VC in agricultural crops. Inner and outer films provided a promising platform for the immobilization of biologically active species.