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 μM^-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 μA μM^-1 and a low detection limit of 0.015 μM. 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.