The effect of incubation temperature on the binding of Salmonella typhimurium to phage-based magnetoelastic biosensors

The objective of this study is to evaluate the effect of incubation temperature on the binding of Salmonella typhimurium with E2 phage magnetoelastic (ME) biosensors. S. typhimurium was inoculated on tomato surfaces and the attachment of S. typhimurium was observed using scanning electron microscopy (SEM). Measurement biosensors, immobilized with E2 phage, and control sensors devoid of E2 phage were placed on the inoculated tomato surface and incubated at different temperatures for a fixed time in order to determine the effect of incubation temperature on the binding. After incubation, the resonant frequencies of both measurement and control sensors were measured using a network analyzer. The binding of S. typhimurium with E2 phage on both types of sensors was confirmed by SEM analysis. The SEM images of the inoculated tomato surfaces confirmed that S. typhimurium attached across the surface, however, its distribution was not uniform. After placement and incubation of the ME biosensors on the spiked tomato surfaces, the resonant frequencies of the ME biosensors were measured. The resonant frequency shifts in the measurement sensors increased as temperature was increased up to 35 C. while the resonant frequency shifts of the control sensors were small and relatively constant across the entire range of incubation temperatures. There were no significant differences between incubation temperatures of 20, 25, 30, 35, 40, 45, and 50 degrees C in measurement sensors (P>0.05). SEM images of the measurement sensors confirmed that increasing resonant frequency shifts were caused by increasing numbers of bound S. typhimurium cells to the measurement sensors. This is contrasted with none or negligible binding of S. typhimurium cells on the control sensors. Overall, the optimum incubation temperature was chosen as 30 degrees C. This result will contribute to the development of a practical ME biosensor protocol for in situ detection of S. typhimurium on fresh produce. (C) 2011 Elsevier B.V. All rights reserved.