Vancomycin recognition and induced-aggregation of the Au nanoparticles through freeze-thaw for foodborne pathogen Staphylococcus aureus detection

Infectious diseases caused by foodborne pathogens have become a serious public health problem. It is urgent to develop simple, rapid, and visual methods for pathogen detection. Herein, gold nanoparticles (AuNPs), aptamer and vancomycin (Van) based dual-recognition molecules and magnetic enrichment were combined to realize visual detection of Staphylococcus aureus (S. aureus). Initially, S. aureus was bounded to aptamer coupled Fe3O4 with high affinity and selectivity, which can achieve the separation and enrichment of S. aureus in complex sample matrix. Subsequently, the second recognition molecule, Van, was conjugated to S. aureus -Apt - Fe3O4. Finally, the unbound Van supernatant was dropped in AuNPs solution that induced the aggregation of the AuNPs through freeze-thaw. Firstly, it was found that AuNPs were stable in the presence of Van after a freeze-thaw cycle. A facile visual colorimetric detection of S. aureus was constructed with the linear range from 101 to 104 CFU/mL and the limit of detection (LOD) of 0.2 CFU/mL. By altering the aptamer, this method can be extended to the other Gram-positive bacteria. The proposed method has great potential applications in monitoring food contamination and infectious diseases.