Real-Time, in-situ Detection of Pathogenic Bacteria on Food Surfaces Using a Surface-Scanning Coil Detector and Phage-Based Magnetoelastic Biosensors
Type of Degreedissertation
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This research uses wireless magnetoelastic (ME) biosensors combined with a surface-scanning coil detector for the direct, real-time detection of Salmonella Typhimurium on fresh food surfaces. The ME biosensor consists of an ME resonator as the sensor platform and E2 phage as the bio-recognition element. For in-situ detection of surface bacterial contaminants, a surface-scanning coil detector was designed and its performance was evaluated. The designed coil was used to excite the ME biosensor and then measure the biosensor’s signal in response to the potential presence of bacteria. A model of the sensor’s longitudinal vibration and an equivalent electrical circuit of the detection system were constructed to theoretically evaluate the coil design and its effect on signal amplitude and detection distance. In order to explain the reason for the different signal amplitudes, a theory of mutual inductive coupling between a vibrating sensor and the coil detector was proposed. Two types of coil detectors were evaluated for design and comparison: solenoid and planar spiral coils. Based on the sensor’s longitudinal vibration and the structure of the coils, the planar spiral coil detector was found to be more sensitive and to give a much larger signal amplitude at resonance. Furthermore, the ability to simultaneously measure multiple sensors on surfaces with the planar spiral coil has been demonstrated. A gradual change of the resonant frequency was observed over time during the reaction between an E2 phage-coated ME biosensor and S. Typhimurium on fresh food surfaces. The effects of a humid environment were researched and the limit of detection was statistically determined. This new technique eliminates the time-consuming and costly sample selection and preparation steps previously required.