Target Recognition-Triggered Interfacial Electron Transfer Model: Toward Signal-On Photoelectrochemical Aptasensing for Efficient Detection of <i>Staphylococcus aureus</i> Using Ti₃C₂T_<i>x</i>-Au NBPs/ZnO NR Composite

<i>Staphylococcus aureus</i> (<i>S. aureus</i>) is one of the most common foodborne pathogens worldwide, which poses a great threat to public health. It is of utmost importance to develop rapid, simple, and sensitive methods for the determination of <i>S. aureus</i>. A signal-on photoelectrochemical (PEC) aptasensor is constructed herein based on titanium carbide (Ti₃C₂T_<i>x</i>)-Au nanobipyramids (NBPs)/ZnO nanoarrays (NRs). The reliability and capability of the PEC aptasensor make it suitable for the sensitive and selective determination of <i>S. aureus</i>. First, the electrostatically self-assembled Ti₃C₂T_<i>x</i>-Au NBP nanomaterial was coated on the ZnO NR surface by a spin-coating method. On the one hand, Ti₃C₂T_<i>x</i>-Au NBPs can broaden the spectral absorption of ZnO NRs, resulting in Ti₃C₂T_<i>x</i>-Au NBPs/ZnO NR composites that exhibit a wide range of absorption from the ultraviolet to the infrared region. On the other hand, Ti₃C₂T_<i>x</i> can reduce the agglomeration of nanoparticles, while Au NBPs can effectively fix the aptamer through the Au-S bond. Specifically, the experimental results show that when <i>S. aureus</i> is present, the Au NBPs-aptamer-<i>S. aureus</i> complex is shed from the electrode surface, altering the interfacial electron transfer model and reducing the steric hindrance. Consequently, an amplified photocurrent signal for the quantitative determination of <i>S. aureus</i> is obtained. Under optimal experimental conditions, a linear correlation is observed between the current response of the aptasensor and the logarithm of the <i>S. aureus</i> concentration (ranging from 1.0 to 1.0 × 10⁶ CFU/mL), with an impressive detection limit as low as 0.5 CFU/mL. Furthermore, the aptasensor has been successfully employed for the detection of <i>S. aureus</i> in milk, with the recovery of 93.0%-99.0%. Hence, this research offers a novel approach for the detection of foodborne pathogens and other noxious substances.