Biofunctionalized magnetic nanoparticle integrated mid-infrared pathogen sensor for food matrixes.

Magnetic nanoparticles functionalized with anti-Escherichia coli O157:H7 or anti-Salmonella typhimurium antibodies that can specifically bind to their target organisms were used to isolate E. coli O157:H7 and S. typhimurium separately from a cocktail of bacteria and from food matrixes. The pathogens were then detected using label-free IR fingerprinting. The binding and detection protocol was first validated using a benchtop FT-IR spectrometer and then applied to a portable mid-IR spectrometer to enable this approach as a point-of-detection technology. Highly selective detection was achieved in less than 30 min at both species (E. coli O157:H7 vs S. typhimurium ) and strain (E. coli O157:H7 vs E. coli K12) levels in complex food matrixes (2% milk, spinach extract) with a detection limit of 10(4)-10(5) CFU/mL. The combined approach of functionalized magnetic nanoparticles and IR spectroscopy imparts specificity through spectroscopic fingerprinting and selectivity through species-specific antibodies with an in-built sample extraction step and could be applied in the field for on-site food-borne pathogen monitoring.