Separation and detection of E. coli O157:H7 using a SERS-based microfluidic immunosensor

A sensitive SERS-based microfluidic immunosensor was developed to separate and detect Escherichia coli O157:H7 in romaine lettuce. SERS nanoprobes, containing gold nanoparticles and specific antibodies against E. coli O157:H7, were used to selectively anchor onto the E. coli O157:H7 cells and separate them from lettuce samples. Separated cells were then detected within a hydrodynamic flow-focusing microfluidic device using the Raman spectroscope with an excitation laser of 785 nm at similar to 35 mW. Bacterial concentrations of 100, 10, 1, and 0.5 CFU .mL(-1) were successfully detected after less than 60 min of enrichment. The limit of detection of E. coli O157:H7 in romaine lettuce was found to be 0.5 CFU.mL(-1), verifying the sensitivity of our protocol for detection of pathogens in food samples. High linearity (R-2 > 0.93) in the calibration curves for E. coli O157:H7 was observed after 30 min of enrichment. The method reduced the analysis time for single-cell detection to only 1 h, which is significantly shorter than the days required in conventional methods. In summary, combining the hydrodynamic flow-focusing microfluidic device with SERS nanoprobes provides a reliable, selective, and sensitive approach for the detection of various pathogens in complex food samples.

Automated summary

A sensitive SERS-based microfluidic immunosensor was developed for the separation and detection of Escherichia coli O157:H7 in romaine lettuce. The combination of SERS nanoprobes and a hydrodynamic flow-focusing microfluidic device provides a reliable, selective, and sensitive approach for the detection of various pathogens in complex food samples.