Long range surface plasmon resonance bacterial pathogen biosensor with magnetic nanoparticle assay

In this paper, long range surface plasmons (LRSP) and magnetic iron oxide nanoparticle (MNP) immunoassay are investigated for advancing the sensitivity of surface plasmon resonance (SPR) biosensor technology for the analysis of bacterial pathogens. The MNPs-antibody conjugates served as labels for enhancing the binding-induced refractive index changes and as “vehicles” for rapid delivery of bacteria from a sample solution to the sensor surface by applied magnetic field. A sensor chip for diffraction-coupled long range surface plasmon resonance (LRSPR) was developed and functionalized with capture antibodies. These surface plasmon waves enable improving the resolution of refractive index changes measurements on the surface and probing whole volume of captured bacterial pathogens. The combined LRSPR and MNP assay was applied for detection of Escherichia coli O157:H7. About 3 orders of magnitude improvement of the sensitivity with respect to regular SPR and the analysis time of ~30 min are demonstrated.