title: Portable nuclear magnetic resonance biosensor and assay for a highly sensitive and rapid detection of foodborne bacteria in complex matrices.
abstract: BACKGROUND
  Nuclear magnetic resonance (NMR) technique is a powerful analytical tool in determining the presence of bacterial contaminants in complex biological samples. In this paper, a portable NMR-based (pNMR) biosensor and assay to detect the foodborne bacteriaEscherichia coliO157:H7 is reported. It uses antibody-functionalized polymer-coated magnetic nanoparticles as proximity biomarker of the bacteria which accelerates NMR resonance signal decay.
  
  
  RESULTS
  The pNMR biosensor operates at 0.47 Tesla of magnetic strength and consists of a high-power pulsed RF transmitter and an ultra-low noise sensing circuitry capable of detecting weak NMR signal at 0.1 μV. The pNMR biosensor assay and sensing mechanism is used in detectingE. coliO157:H7 bacteria in drinking water and milk samples. Experimental results demonstrate that by adding a filtration step in the assay, the pNMR biosensor is able to detectE. coliO157:H7 as low as 76 CFU/mL in water samples and as low as 92 CFU/mL in milk samples in about one min.
  
  
  CONCLUSIONS
  The pNMR biosensor assay and sensing system is innovative for foodborne bacterial detection in food matrices. The lowest detection level forE. coliO157:H7 in water and milk samples is essentially 101CFU/mL. Although the linear range of detection is only from 101to 104CFU/mL, the wider detection range spans from 101CFU/mL to 107CFU/mL. Existing pNMR biosensors have detection limits at 103-104CFU/mL only. The detection technique can be extended to other microbial or viral organisms by merely changing the specificity of the antibodies. Besides food safety, the pNMR biosensor described in this paper has potential to be applied as a rapid detection device in biodefense and healthcare diagnostic applications.
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48824 USA.
authors.forename: Yilun
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48824 USA.
authors.forename: Evangelyn C
authors.initials: EC
authors.lastname: Alocilja
keywords: Biosensors; Magnetic nanoparticles; Magnetic separation; Nanotechnology; Nuclear magnetic resonance