Covalent immobilization of glucose oxidase on the film prepared by electrochemical polymerization of N-phenylglycine for amperometric glucose sensing

•Poly(N-phenylglycine) (PPG) was prepared electrochemically in the form of a thin film.•The PPG film had a considerably high conductivity.•Glucose oxidase (GOx) was immobilized covalently on the PPG film.•The GOx-immobilized PPG film was applied to amperometric glucose sensing.•A marked sensitivity was achieved, owing to the high conductivity of the PPG film.

N-Phenylglycine, an aniline-derived amino acid, was polymerized electrochemically. The resulting poly(N-phenylglycine) (PPG) was in the form of a thin film having the conductivity of 2.5 × 10−3 S cm−1. The surface of the PPG film had a fibrous structure, which made the actual area of the surface larger than the apparent one. Glucose oxidase (GOx) was immobilized covalently on the PPG film by the condensation reaction of amino groups of GOx with the carboxyl groups present on the film. The quantity and activity of the immobilized GOx were determined to be 66.4 μg cm−2 and 121 mU cm−2, respectively. The GOx-immobilized PPG film was applied to amperometric glucose sensing in the presence of p-benzoquinone employed as an electron mediator. It was found that the current response increased with an increase in glucose concentration up to 7.5 mM. The sensitivity was 21.0 μA mM−1 cm−2 with the relative standard deviation of 6.2% (n = 5).

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