Wireless magnetoelastic biosensors for the detection of Salmonella on fresh produce

This paper investigates the use of wireless magnetoelastic (ME) biosensors for the direct detection of Salmonella Typhimurium on fresh produce (tomatoes, spinach leaves and shell eggs). The ME biosensor consists of an ME resonator as the sensor platform and E2 phage as the bio-recognition element. The E2 phage is genetically engineered to specifically bind with S. Typhimurium. The ME biosensor, a wireless sensor, is actuated into resonance by an externally applied magnetic field. When the biosensor binds with Salmonella cells, the mass of the resonator increases, resulting in a decrease in the sensor´s resonant frequency. Multiple sensors can be wirelessly and remotely monitored. Multiple measurement and control sensors were placed on fresh produce that was spiked with S. Typhimurium solutions of different known concentrations (5 × 10¹ to 5 × 10⁸ CFU/ml (colony-forming unit/ml)). The resonant frequency of the sensors before and after the exposure to the spiked fresh produce was measured. The resonant frequency change of the measurement sensors was significantly different from the control sensors, indicating Salmonella contamination. Despite the different surface topographies of the fresh produce, similar ME biosensor measurement results were obtained for the three fresh produces. Scanning electron microscopy was used to confirm binding of the Salmonella to the biosensor surface and the resulting resonant frequency changes.