Rapid colorimetric detection and potent eradication of Staphylococcus aureus in dairy products via a dual-functional magnetic mesoporous manganese oxide nanozyme probe.

Abstract

Staphylococcus aureus, a major foodborne pathogen contaminating dairy products, threatens food safety and public health via food poisoning and severe infections such as 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 manganese oxide-like (MnOx) nanozyme probe (MMMNP) by integrating mesoporous MnOx nanozyme with oxidase-mimetic activity, Fe3O4 magnetic nanoparticles, and S. aureus-specific aptamers. The synthesis involved the preparation of hydrothermal Fe3O4, the synthesis of MnOx, and the construction of a composite with bond positions and electrostatic interactions. For detection, MMMNP mixed with samples underwent magnetic separation, followed by 3,3',5,5'-tetramethylbenzidine-triggered color reaction. The 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 limit of detection of 3.33 cfu·mL-1 for UV-visible detection and 1 × 102 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%, relative SD <5%). Unexpectedly, lower detection limits and better linearity were also achieved in the milk samples. Preliminary tests confirmed magnetic 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.