Glucose sensing with glucose oxidase immobilized covalently on the films of thiophene copolymers

Films of 3-methylthiophene/thiophene-3-acetic acid (3MT/T3A) copolymer were prepared by electrochemical polymerization, and glucose oxidase (GOx) was immobilized covalently by condensation reaction with the carboxyl groups of T3A units on the films. By use of the GOx-immobilized films, glucose sensing was carried out to examine the influence of property of the copolymer as a support material on amperometric sensitivity. Conductivity of the copolymer films was found to increase with decreasing content of T3A units. UV-VIS absorption spectra of the copolymer films showed that wavelength of maximum absorption of the copolymer films shifted to lower energy with decreasing content of T3A units. Amperometric response to incremental addition of glucose solution was examined with the GOx-immobilized copolymer films at + 0.4 V (vs. saturated calomel electrode) using p-benzoquinone as a mediator. It was confirmed that large response currents were obtained by use of the copolymer films with a small content of T3A units., In addition, electrically dedoped GOx-immobilized films exhibited smaller response currents than doped one. These results suggest that the conductivity of support materials is a very important factor to dominate the efficiency of glucose-sensing devices.