Surface-Enhanced Raman Scattering and Fluorescence-Based Dual Nanoprobes for Multiplexed Detection of Bacterial Pathogens

Abstract

Surface-enhanced Raman scattering (SERS)-based biosensing has been of growing interest for the detection of bacterial pathogens. Moreover, fluorescence (FL)-based bioimaging is also useful in that it is rapid, nearly non-destructive and has high sensitivity. In this study, for the first time, we report the preparation of dual nanoprobes based on both SERS and FL. These probes comprise hierarchical nanostructures with metallic nanoparticle clusters (MNPCs). In combination with magnetic beads (MBs), the probes were used for fast and multiplexed detection of bacterial pathogens. Both MNPCs with different Raman dyes and two sets of FL dyes were simultaneously encapsulated within polymeric nanoparticles using electrohydrodynamic (EHD) jetting and chemically stabilized. Two different sets of monoclonal antibodies (mAbs) against two kinds of bacterial pathogens, Escherichia coli and Francisella tularensis, were separately conjugated with the dual nanoprobes and the MBs. Sandwich-type immunocomplexes composed of SERS-FL dual nanoprobes, pathogens, and MBs were formed in the presence of E. coli and F. tularensis, and a linear correlation was observed between Raman intensity and pathogen concentration in the range of 102–106 cells/mL; the limit of detection was less than 102 cells/mL. Also, selective sandwich-type immunocomplexes against the pathogens were successfully imaged by FL signals at 514 nm and 633 nm wavelength for excitation. In conclusion, excellent capability of fast imaging and multiplexed detection of bacterial pathogens was achieved using a new class of SERS-FL dual nanoprobes, providing a powerful tool for qualitative and quantitative multiplexed biodetection of pathogens.