Phage immobilized magnetoelastic sensor for the detection of Salmonella typhimurium

In this article, a phage-based magnetoelastic sensor for the detection of Salmonella typhimurium is reported. Filamentous bacteriophage specific to S. typhimurium was used as a biorecognition element in order to ensure specific and selective binding of bacteria onto the sensor surface. Phage was immobilized onto the surface of the sensors by physical adsorption. The phage immobilized magnetoelastic sensors were exposed to S. typhimurium cultures with different concentrations ranging from 5 × 101 to 5 × 108 cfu/ml, and the corresponding changes in resonance frequency response of the sensor were studied. It was experimentally established that the sensitivity of the magnetoelastic sensors was higher for sensors with smaller physical dimensions. An increase in sensitivity from 159 Hz/decade for a 2 mm sensor to 770 Hz/decade for a 1 mm sensor was observed. Scanning electron microscopy (SEM) analysis of previously assayed biosensors provided visual verification of frequency changes that were caused by S. typhimurium binding to phage immobilized on the sensor surface. The detection limit on the order of 103 cfu/ml was obtained for a sensor with dimensions 1 × 0.2 × 0.015 mm.