Detection of pathogen Escherichia coli O157:H7 with a wireless magnetoelastic-sensing device amplified by using chitosan-modified magnetic Fe3O4 nanoparticles

We report on a wireless magnetoelastic-sensing device for the assay of pathogen with Escherichia coli O157:H7 (E. coli) as a target using chitosan-modified magnetic Fe3O4 nanoparticles (CMNPs) as signal-amplifying tags. At suitable pH the CMNPs, Fe3O4 nanoparticles functionalized with a layer of chitosan, bind to negatively charged E. coli through electrostatic attraction. The E. coli attached CMNPs are magnetically bound to the surface of the magnetoelastic sensor, resulting in enhanced mass loading on the sensor surface that in turn decreases its resonance frequency allowing quantification of E. coli concentrations. The sensor shows a linear response to the logarithmic concentration of E. coli in the range of 10 cells mL−1 to 3.7 × 108 cells mL−1, with a detection limit (LOD) of 10 cells mL−1. Small molecules such as albumin bovine and ovalbumin show no interference on the detection.