Extracellular vesicles are nanoscale and microscale biological vesicles actively released by nearly all cell types within the body. These small vesicles have been shown to play important biological roles, including cell-to-cell communication, coagulation and signal transduction. They have also been shown to play oncogenic roles in cancer metastasis and progression. Extracellular vesicles are composed of an aqueous cytosolic core and a phospholipid membrane, and exhibit variability in their internal and external cargoes. Developing a better understanding of the structure and diversity of the components of extracellular vesicles may hold promise in uncovering the pathways involved in the formation and progression of various cancers and diseases. Current studies of extracellular vesicles focus on bulk analysis, whereas variability amongst individual extracellular vesicles has been minimally reported in literature. In this study, we propose the use of a surface-enhanced Raman spectroscopy platform in movement towards trapping extracellular vesicles secreted from a mesenchymal stem cell line followed by probing their individual spectral signatures. Here, we propose the use of plasmonic-well based structures as a means of isolating, trapping and controlling the position of biologically relevant vesicles on plasmonic platforms. Trapping and identification of extracellular vesicles occurs without use of labelling agents, allowing for characterization of the intrinsic molecular information of individual extracellular vesicles.
Although discovered 40 years ago, the interest in surface enhanced Raman spectroscopy (SERS) for a variety of applications in the fields of material and biomaterial has been revived over the past decade mostly due to a better control over the fabrication methods of nanoscale metallic structures. Metallic structures prepared by bottom-up or top-down methods can be tailored for a variety of applications in order to benefit from the best conditions for surface enhancement. SERS platforms made by nanosphere lithography are for example very versatile platforms that show a detection limit in the femtomolar range. Although quantitative measurements are difficult to perform in Raman spectroscopy, the plasmon-mediated enhancement by the metallic nanostructures are of great interest to improve the detection of analytes traces at surfaces. The extension of SERS to tip-enhanced Raman spectroscopy (TERS) is also very valuable to improve spatial resolution of Raman measurements and to yield surface signals, thus making TERS spectroscopy a surface specific technique. Herein we review SERS and TERS measurements of a model molecule (nitrothiophenol) adsorbed onto gold surfaces.
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