Detection of food-borne pathogens by nanoparticle technology coupledto a low cost Cell Reader

摘要

The detection, identification and quantification of pathogenic microorganisms at low cost are of great interest to theagro-food industry. We have developed a simple, rapid, sensitive, and specific method for detection of food-bornepathogens based on use of nanoparticles alongside a low cost fluorescence cell reader for the bioassay. The nanoparticlesare coupled with antibodies that allow specific recognition of the targeted Listeria in either a liquid or food matrix. Thebioconjugated nanoparticles (FNP) contain thousands of dye molecules enabling significant amplification of thefluorescent signal emitted from each bacterium. The developed fluorescence Cell Reader is an LED-based readercoupled with suitable optics and a camera that acquires high resolution images. The dedicated algorithm allowed thecounting of each individual nanoparticles-fluorescent bacterial cells thus enabling highly sensitive reading. The systemallows, within 1 hour, the recovery and counting of 10~4to 10~8cfu/mL ofListeriain pure culture. However, neither theCell Reader nor the algorithm can differentiate between the FNPs specifically-bound to the target and the residualunbound FNPs limiting sensitivity of the system. Since FNPs are too small to be washed in the bioassay, a dual taggingapproach was implemented to allow online optical separation of the fluorescent background caused by free FNPs.