Photoelectrochemically driven bioconversion and determination of nifedipine based on a double photoelectrode system

In the present work, a double photoelectrode system has been constructed for photoelectrochemically driven enzymatic bioconversion and determination of nifedipine. In which, the TiO2 nanotube arrays in-situ assembled with g-C3N4 (TNA/g-C3N4) was used as a photoanode, and a cytochrome P450 3A4 (CYP3A4) enzyme was immobilized in the porous ITO/CuO films to fabricate an ITO/CuO/CYP3A4 photocathode. The constructed double photoelectrode system had a significant photocurrent response compared to the single ITO/CuO/CYP3A4 or TNA/g-C3N4 under visible light irradiation. Under optimal conditions, the photocurrent of the double photoelectrode system had a high catalytic activity toward substrate nifedipine with k(cat) of 5.62 s(-1) and catalytic efficiency with k(cat)/k(m)(app) of 0.94 mu M-1 s(-1), and the bioconversion yield of nifedipine reached 22.1%. Furthermore, the constructed double photoelectrode system could be used to determine the nifedipine concentration with a high sensitivity of 2.46 mu A mu M-1 and a low detection limit of 0.015 mu M. Therefore, the proposed double photoelectrode system can be used well for study enzyme biocatalysis for target bioconversion, and also has a potential application for toxicity analysis.