Exosomes and microvesicles: identification and targeting by particle size and lipid chemical probes

Exosomes and microvesicles are two classes of submicroscopic vesicle released by cells into the extracellular space. Collectively referred to as extracellular vesicles, these membrane containers facilitate important cell-cell communication by carrying a diverse array of signaling molecules, including nucleic acids, proteins, and lipids. Recently, the role of extracellular vesicle signaling in cancer progression has become a topic of significant interest. Methods to detect and target exosomes and microvesicles are needed to realize applications of extracellular vesicles as biomarkers and, perhaps, therapeutic targets. Detection of exosomes and microvesicles is a complex problem as they are both submicroscopic and of heterogeneous cellular origins. In this Minireview, we highlight the basic biology of extracellular vesicles, and address available biochemical and biophysical detection methods. Detectible characteristics described here include lipid and protein composition, and physical properties such as the vesicle membrane shape and diffusion coefficient. In particular, we propose that detection of exosome and microvesicle membrane curvature with lipid chemical probes that sense membrane shape is a distinctly promising method for identifying and targeting these vesicles.