Raman and Tip-Enhanced Raman spectroscopy characterization of milk-derived extracellular vesicles: Toward nanoscale single vesicle analysis

Tip-enhanced Raman Spectroscopy (TERS) is an advanced technique to perform local chemical analysis of the surface of a sample combining Raman spectroscopy and atomic force microscopy (AFM) [1]. In this work, TERS is demonstrated to represent an innovative and powerful approach to study extracellular vesicles, in particular bovine milk-derived extracellular vesicles (mEVs), which are nanostructures with considerable potential in drug delivery and therapeutic applications [2]. Raman spectroscopy has been used to analyze mEVs to obtain a detailed spectrum to identify the ‘signature’ of mEVs in terms of their characteristic molecular vibrations and, therefore, their chemical composition. TERS has been used to study individual mEVs [3], demonstrating the possibility to investigated a single mEV selected on the surface of the sample and, moreover, to analyze specific locations on the selected mEV with nanometer lateral resolution. Thanks to the property of TERS to acquire the signal from only the first few nanometers of the surface, chemical investigation of the lipidic membrane at the various locations of the selected mEV could be performed by analyzing the Raman shift peaks in the relevant range of the spectrum (2800-3000 cm-1). Despite limited to mEVs, this work demonstrates the potential of TERS in analysis of extracellular vesicles. References [1] Zhang Z., Sheng S., Wang R., Sun M., Anal. Chem. (2016); 88, 9328. [2] Tian MY., Hao DX., Liu Y., He J., Zhao ZH., Guo TY., Li X., Zhang Y., Food Funct. (2023); 14, 1320 [3] Stepanenko T., Sofińska K., Wilkosz N., Dybas J., Wiercigroch E., Bulat K., Szczesny-Malysiak E., Skirlińska-Nosek K., Seweryn S., Chwiej J., Lipiec E., Marzec KM., Analyst (2024); 149, 778.