A novel Aptamer-induced CHA amplification strategy for ultrasensitive detection of Staphylococcus aureus and NIR-triggered photothermal bactericidal Activity based on aptamer-modified magnetic Fe3O4@AuNRs

The development of multifunctional biosensors integrating recognition and therapeutic functions is critical for ensuring food safety and preventing foodborne diseases. Herein, an integrated design strategy was demonstrated to establish an innovative Fe3O4 @AuNRs-aptasensor for efficient detecting Staphylococcus aureus (S. aureus), which could enrich and photothermally eliminate bacteria under the radiation of near-infrared light irradiation (NIR). The detection assay relies on the binding of aptamer to Fe3O4 @AuNRs (Fe3O4 @ AuNRs-aptasensor) to induce the release of c-aptamer (c-Apt) in the presence of S. aureus, thereby triggering catalytic hairpin assembly (CHA) reaction and restoring the fluorescence of the reporter. The developed biosensor achieved direct, ultrasensitive, and specificity detection of S. aureus with a linear response ranging from 102 to 106 CFU/mL and a detection limit of 101 CFU/mL under optimal conditions. Furthermore, the aptasensor can be applied for the detection of S. aureus in milk with recoveries of 90.3–95.6% at the concentration between 1.0 × 102 and 1.0 × 104 CFU/mL. Additionally, Fe3O4 @AuNRs-aptasensor shows high photothermal sterilization performance under NIR irradiation. The study emphasizes the combination of high sensitivity base on molecular detection and photothermal antibacterial activity of novel nanomaterials activated by NIR light to design multifunctional probe, which show great potential for application in food analysis and early foodborne disease diagnosis.