A Wireless RFID Compatible Sensor Tag Using Gold Nanoparticle Markers for Pathogen Detection in the Liquid Food Supply Chain

A wireless antibody-free biosensor for rapid detection of pathogenic bacteria in milk was developed using dextrin-capped gold nanoparticles (d-AuNP) as markers. The developed system consists of an interdigitated capacitor coupled to an inductor forming an inductor–capacitor (
LC
) resonant tank; a “Smart” vial onto which
E. coli
C3000 suspended in milk matrix adheres and are labeled with d-AuNP markers; and a wireless pick up coil. Detection is based on impedance loading of the interdigitated sensor by d-AuNP bound to the pathogenic bacteria. The resonance frequency shift of the
LC
tank is correlated with the concentration of
E. coli
cells in the milk. The sensors are field-operable and can detect bacteria counts as low as 5 log CFU/ml within an hour. Spectrophotometry is used to verify the sensitivity of the developed sensor. The resonance frequency of these sensors can be easily designed to match the existing radio frequency identification (RFID) frequency bands. The developed tag holds potential application in detection of a variety of pathogenic bacteria for quality control along the liquid food supply chain.