NIR-driven multifunctional PEC biosensor based on aptamer-modified PDA/MnO₂ photoelectrode for bacterial detection...

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/MnO₂ 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 10⁷ CFU/mL with a low detection limit of 2.0 CFU/mL. Notably, PDA/MnO₂ with peroxidase-like activity facilitated the catalytic oxidation of S. aureus with assistance of hydrogen peroxide (H₂O₂) 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/MnO₂ converted light energy into heat energy under the irradiation of NIR light (808 nm, 1.5 W/cm²), 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.