NIR-driven multifunctional PEC biosensor based on aptamer-modified PDA/MnO photoelectrode for bacterial detection and inactivation.

Sensitive detection and effective inactivation of bacteria are essential in preventing foodborne bacterial infection that poses a significant threat to human health. Herein, a near-infrared (NIR)-driven multifunctional photoelectrochemical (PEC) biosensor was constructed for detection and inactivation of S. aureus. Based on the covalent bonding between amine and carboxyl groups, carboxyl-functionalized SA31 aptamer was immobilized on the PDA/MnO photoelectrode. In the presence of S. aureus, SA31 aptamer can specifically capture S. aureus, causing the decrease of photocurrent signal owing to steric hindrance effect. Leveraging photocurrent-off signal, there existed a satisfied linear relationship between the photocurrent variation and the logarithm of S. aureus concentration, achieving a wide linear range from 10 to 10 CFU/mL with a low detection limit of 2.0 CFU/mL. Notably, PDA/MnO with peroxidase-like activity facilitated the catalytic oxidation of S. aureus with assistance of hydrogen peroxide (HO) to cause the inactivation of S. aureus. Desorption of inactivated S. aureus from the photoelectrode led to a recovery of photocurrent signal, enabling a "signal on" switch. Simultaneously, the excellent photothermal performance of the PDA/MnO converted light energy into heat energy under the irradiation of NIR light (808 nm, 1.5 W/cm), triggering the synergistic antibacterial effect against S. aureus (97.36%). This work provides a novel strategy for fabricating the detection and inactivation of bacteria in practical applications.