Magnetic Nanoparticles Enhanced Microarray Detection of Multiple Foodborne Pathogens

In order to ensure food safety and minimize the occurrence of foodborne illness, it is critical to monitor food production for the presence of foodborne pathogens. This highlights the need for rapid, sensitive, and selective methods to detect pathogens in food products. In this study, a magnetic nanoparticles enhanced oligonucleotide microarray assay was developed for rapid and sensitive identification of Escherichia coli O157: H7, Salmonella enterica, Vibrio cholerae and Campylobacter jejuni in food. Biotin labeled forward primer and Cy3 labeled reverse primer were used for exponential PCR amplification. Magnetic nanoparticles with covalently attached streptavidin were then used to capture the PCR products. After denaturation at 95 degrees C and magnetic separation, the Cy3-labeled target strand was collected and concentrated in the supernatant for hybridization. By using streptavidin-modified magnetic nanoparticles (SA-MNPs) for rapid generation of purified single stranded DNA target, we successfully increased hybridization signal and improved sensitivity for pathogen detection on DNA microarray. In comparison with the conventional single stranded target preparation methods, this magnetic nanoparticles based method yielded up to 15-fold increase in the hybridization signal and achieved 1 similar to 2 orders of magnitude enhancement on limit of detection. The assay sensitivity for identification of Salmonella enterica in ground chicken sample was 200 cells/g of food without a pre-enrichment, and the sensitivity was increased 100-fold (similar to 2 cells/g) following 5 hr pre-enrichment at 37 degrees C. The results indicate that the magnetic nanoparticles enhanced microarray method has great potential for detection of food-borne pathogens in food samples with both high specificity and high sensitivity.