Rapid Colorimetric Detection and Potent Eradication of Staphylococcus aureus in Dairy Products via a Dual-Functional Magnetic Mesoporous MnOx Nanozyme Probe

Staphylococcus aureus (S. aureus), a major foodborne pathogen contaminating dairy products, threatens food safety and public health via food poisoning and severe infections like bacteremia. Conventional culture-based methods are time-consuming, while advanced techniques need expensive equipment, limiting on-site use. To address this, we developed a novel Magnetic Mesoporous MnOx Nanozyme Probe (MMMNPs) by integrating Mesoporous MnO_x Nanozyme with oxidase-mimetic activity, Fe₃O₄ magnetic nanoparticles, and S. aureus-specific aptamers. The synthesis involved the preparation of hydrothermal Fe₃O₄, the synthesis of MnO_x, and the construction of a composite with bond positions and electrostatic interactions. For detection, MMMNPs mixed with samples underwent magnetic separation, followed by TMB-triggered color reaction. S. aureus (0 - 10⁶ cfu·mL^-1) inhibited probe activity, fading solution from deep blue to colorless. There was a good linear correlation (R² = 0.980) between the shift of the absorbance peak at 652 nm and the logarithm of S. aureus concentration, with a LOD of 3.33 cfu·mL^-1 for UV-Vis detection and 1x10² cfu·mL^-1 for naked-eye visual detection.The probe exhibited high specificity, with no response to interfering bacteria, and demonstrated good applicability in spiked milk (recovery: 86.84% - 113.81%, RSD <5%). Unexpectedly, lower detection limits and better linearity were also achieved in the milk samples. Preliminary tests confirmed Mag-MnOx's significant bacteriostatic activity against S. aureus. This low-cost, easy-to-operate strategy enables S. aureus detection and elimination, promising on-site use in food safety and clinical diagnosis.