Catechol sensor based on ascorbate oxidase immobilized polymer-modified graphite electrode

A selectivity and sensitivity enhanced catechol sensor based on a polymer-modified graphite electrode was fabricated by immobilizing ascorbate oxidase (AO) into a poly(N-vinyl pyrrolidone) (PNVP) membrane. AO was immobilized between two PNVP membrane layers as a sandwiched structure by cross-linking PNVP with gamma radiation. The sensor responses to catechol and ascorbic acid were evaluated by cyclic voltammetry. The sensor showed a selective response to catechol even in the presence of ascorbic acid, which was due to blocking ascorbic acid access to the electrode surface by the enzymatic activity of AO immobilized in the polymer membrane. Compared to a bare electrode without modification with the PNVP membrane, an enhanced response of the sensor to catechol was observed, which was due to preconcentration of catechol into the PNVP membrane. The enzymatic activity of AO immobilized on the sensor surface did not change for at least four days.