This paper demonstrates the direct detection of Salmonella typhimurium on fresh tomatoes using multiple phage-based magnetoelastic (ME) biosensors. In this investigation, the sample collection/preparation step that is necessary for current pathogen detection methods was eliminated. ME biosensors are wireless sensors and are composed of a ME resonator platform immobilized with E2 phage. The E2 phage is genetically engineered to bind with Salmonella typhimurium. Upon contact with the specific target bacteria, Salmonella typhimurium, the resonance frequency of the ME biosensor decreases due to the binding of bacterial cells on the sensor surface. Multiple ME biosensors were directly placed on tomato surfaces spiked with different concentrations of Salmonella typhimurium and binding with the bacteria allowed to occur. The resonance frequencies of the ME biosensors and control sensors (without phage coating) were measured before and after the placement of the biosensors on tomato surfaces. Results showed that shifts in the resonance frequency of the phage coated ME biosensors were observed, while the changes of control sensors were negligible.
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