Abstract:[Objective] This study aims to improve the detection specificity and sensitivity for Escherichia coli (E. coli) O157:H7.[Method] A highly specific and sensitive method for the detection of E. coli O157:H7 was established based on magnetic separation and signal amplification strategies combined with surface-enhanced Raman spectroscopy (SERS). Aptamers were used as recognition elements and combined with magnetic beads and polystyrene (PS) microspheres to construct a separation probe (MB@Apt) and a signal amplification Raman tag (4-MBN@PS@Apt), respectively.[Result] In the presence of E. coli O157:H7, MB@Apt and 4-MBN@PS@Apt formed a “sandwich” structured composite (MB@Apt/E. coli O157:H7/4-MBN@PS@Apt), which could be rapidly separated and enriched by an external magnet. After tetrahydrofuran (THF) was added, the low biological background Raman reporter 4-MBN in the Raman tag was quickly released. The relative Raman intensity of 4-MBN at 1 073.9 cm-1 showed a good linear relationship with the logarithm of E. coli O157:H7 concentration in the range of 1×103 to 1×108 CFU/mL, with a determination coefficient (R2) of 0.98. The established method showed a limit of detection (LOD) of 312 CFU/mL for E. coli O157:H7, the recovery rates ranging from 61.87% to 135.55% in tap water and milk samples, and relative standard deviations (RSD) between 0.27% and 5.28%.[Conclusion] This method exhibited high detection sensitivity for E. coli O157:H7 and provided a new approach for rapid detection of foodborne pathogenic bacteria.
