Exosomes are small (~ 100 nm diameter) vesicles of endocytic origin that are naturally produced by many cell types and are released into several bodily fluids, including the bloodstream. Extracellular vesicles contain a variety of cargo including DNA, RNA, microRNA and protein. Due to the cell membrane and effective packaging, extracellular vesicles provide a stable environment for the cargo while circulating in the bloodstream.
Exosomes were originally thought to be cellular waste products, and little attention was paid to them. Now, they are recognized as being important in intercellular communication, spreading of biomolecules, and in the development of a number of diseases.
Because of their lipid bilayer membranes, exosomes may be an excellent means of drug delivery because they would be well tolerated by the host. Exosomes can be loaded with drugs and engineered such that they will deliver their payload to tissues of interest (such as diseased organs and cancerous tumors); surface markers can be introduced to exosomes that target these tissues and their therapeutic payload will be delivered.