Simultaneous Detection of Salmonella typhimurium and Bacillus anthracis Spores Using Phage-Based Magnetoelastic Biosensors

The objective of this research was to investigate simultaneous detection of two different biological pathogens using one type of sensor. The biosensors investigated are comprised of a magnetoelastic (ME) particle coated with phage as the biomolecular recognition element, and resonated by an AC magnetic field. As cells/spores are captured by the phage, the mass of the sensor increases, which results in a decrease in the sensor’s resonant frequency. Two genetically engineered phages, binding with S. typhimurium or B. anthracis, were immobilized onto two separate ME particles with different dimensions, allowing simultaneous measurement of two different resonance peaks. Upon exposure to solutions containing known concentrations of each analyte, only the biosensor coated with the corresponding phage responded. SEM and TEM were used to verify and quantify interaction of each biosensor with its target analyte. Results show that the observed number of bound cells/spores corresponds closely to the number calculated from the frequency shift data.