In recent years, the existence of a specific way of cell communication based on the release of membranous

nano/micro-sized vesicles has been discovered and acknowledged; and the research in this field is currently

producing an exponentially rising number of scientific publications (1, 2). The general term for such cellderived

particles is Extracellular Vesicles (EVs) (1); they are expelled from almost all living cells and can be

isolated from a variety of body fluids such as blood plasma, urine, saliva, and milk, among others (2). In

general, EVs population is quite heterogeneous; their size may vary between 30 nm and 3 μm, and

depending on the origin, function or size they bear various names: exosomes, microvesicles,

ectosomes/microparticles, apoptotic bodies, etc. EVs reflect the physiological state of the cells of origin;

being released in the extracellular space, they can interact with neighbour/remote cells and directly induce a

signalling pathway or affect the cellular phenotype via the transfer of new receptors or genetic material (2).

For example, EVs may carry messenger- and micro-RNAs, which can be functionally expressed in the

recipient cells and/or regulate their gene expression (3). Other EVs can transmit immune properties to their

cell targets (4). Diseased cells are even more prone to secrete EVs, which then contain signatures of a

number of specific illnesses such as cancers, cardiac and neurological disorders, AIDS, infections or allergic

diseases. For example, concentration and protein composition of EVs might be useful for early detection of

various cancers (2, 5). Therefore, EVs are important interesting candidates for evaluation of “healthy” and “ill”

cellular states, for diagnostic purposes.

Raman spectroscopy, in combination with the effect of optical trapping, is known for a long time as a

powerful method of molecular analysis (6). At the single-cell level, this technique was first applied in 2002

and since then has become a recognized powerful method of cellular research (7). However, at the subcellular

level, the inherently weak Raman signal poses problems; and a very limited number of Raman

studies was reported for biological objects in the size range down to 200 nm. We have recently performed

the first Raman Tweezer Microspectroscopy (RTM) study (8) of EVs from Dictyostelium discoideum  cells and

also from human urine samples proving the feasibility of Raman Tweezers approach in ~100-nm range.

In my talk I’ll focus on our current RTM research of EVs in ~100 nm range (so-called exosomes).

The experimental setup, data accumulation protocol, and data treatment procedures will be presented, and

the possibilities and limitations of the method will be discussed in detail, together with our latest results on

exosomes and related compounds (liposomes, low-density lipoproteins).

1. Raposo G, Stoorvogel W (2013) Extracellular vesicles: Exosomes, microvesicles, and friends. Journal of Cell

Biology 200:373-383.

2. Corrado C, et al. (2013) Exosomes as Intercellular Signaling Organelles Involved in Health and Disease: Basic

Science and Clinical Applications. International Journal of Molecular Sciences 14:5338-5366.

3. Valadi H, et al. (2007) Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic

exchange between cells. Nature Cell Biology 9:654-U672.

4. Robbins PD, Morelli AE (2014) Regulation of immune responses by extracellular vesicles. Nature Reviews

Immunology 14:195-208.

5. Peinado H, et al. (2012) Melanoma exosomes educate bone marrow progenitor cells toward a pro-metastatic

phenotype through MET. Nature Medicine 18:883-891.

6. Petrov DV (2007) Raman spectroscopy of optically trapped particles. Journal of Optics a-Pure and Applied Optics

9:S139-S156.

7. Chan JW (2013) Recent advances in laser tweezers Raman spectroscopy (LTRS) for label-free analysis of single

cells. Journal of Biophotonics 6:36-48.

8. Tatischeff I, Larquet E, Falcon-Perez JM, Turpin P-Y, Kruglik SG (2012) Fast characterisation of cell-derived

extracellular vesicles by nanoparticles tracking analysis, cryo-electron microscopy, and Raman tweezers

microspectroscopy. Journal of Extracellular Vesicles 1:1.