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A fluorescence-positioned hybridization chain reaction system for sensitive detection of Salmonella in milk

In this study, a fluorescence-positioned hybridization chain reaction (HCR) system for the detection of single-stranded DNA (ssDNA) specific to Salmonella was developed. Target ssDNA captured by magnetic beads was used to trigger the HCR, forming multiple double-stranded DNAs (dsDNAs). SYBR Green I was applied to intercalate with the minor groove of the dsDNA forming MBs + dsDNA + SYBR Green I. Magnetic separation was used to isolate the MBs + dsDNA + SYBR Green I from the excess reagents before recording the fluorescence intensity (FI). This fluorescence-positioned HCR method for the quantitative detection of Salmonella showed a limit of detection (LOD) as low as 4.2 × 101 CFU mL−1 in 0.01 M phosphate-buffered saline (PBS). When the method was applied in spiked milk samples, the LOD was recorded at 4.2 × 102 CFU mL−1. The fluorescence-positioned HCR method provided a modification-free and fluorescence-positioned strategy for sensitive detection of target DNA which holds promise for sensitive and selective bacterial detection.