Exosomes are small (~50-150nm) extracellular vesicles (EVs) released from all cell types and found in body fluids and cell culture supernatants.

Exosomes are generated by fusion of a specialized endosome, the multivesicular body (MVB)1 with the plasma membrane. Exosomes are delimitated by a lipid bilayer and can not replicate. Exosomes were initially thought as cellular waste produced by damaged cells or of cellular metabolism with no effect on other cells.

However, exosomes have recently been proposed to provide means for intercellular exchange of macromolecules, allowing the transfer of proteins, lipids, mRNA, miRNA and DNA, contributing to intercellular communication in relevant biological processes, including apoptosis, antigen presentation, angiogenesis, inflammation, and coagulation, playing, therefore, an important role in the development of several diseases, and specifically, modulating cancer microenvironment and the immune response.

In addition, exosomes have emerged as a new source of potential non-invasive biomarkers for various diseases, since they can be easily obtained from body fluids such as urine, blood, saliva, or breastmilk and their composition may be directly dependent on the physiological and/or pathological state of the patient. Even the number of secreted exosomes can change with the onset of different pathologies, so the detection of quantity variations could be of great relevance for diagnosis, especially in patients with cancer. Isolation and characterization of exosomes from body fluids can provide very valuable information for early detection, disease monitoring and development of effective treatments against cancer and autoimmune diseases, among others.

Moreover, a deeper knowledge of the exosome biology can also accelerate the use of these EVs in fields such as regenerative medicine, vaccines and monoclonal antibodies, where they could play an important role as delivery systems, helping to increase the effectiveness of the treatments. 

Research in exosomes as a potential source of biomarkers of human diseases has grown rapidly in recent years and consequently there is a large number of techniques for the isolation and the characterization of this type of EVs.

However, many of the current techniques are poorly standardized.  Furthermore, the use of exosomes in diagnostic tests or clinical research, requires a sensitive, reproducible and highperformance method for the detection, characterization and quantification of exosome samples.