A novel light-driven pH-biosensor based on bacteriorhodopsin

Since it is one of the common proton pump proteins, the bacteriorhodopsin (bR) has attracted significant attention in the field of photoelectronic devices for the development of biohybrid sensors. Here, we report a bR-based photoelectrode for determination of pH in aqueous solutions. Under light irradiation, the bR-based electrode quickly generates a transient photocurrent and follows a reverse photocurrent when the light is switched off. Moreover, the magnitude of forward (I_p) and reverse (I_n) currents are controlled by adjusting the pH of electrolyte. An excellent linear relationship between the I_p/I_n ratio is obtained in the range of pH from 3.5 to 9. In addition, because of the rapid photoelectric response of bR, the bR-based biohybrid sensor is used for the real-time detection of pH in a microfluidic designed system.