Tetraspanins are a family of membrane proteins commonly found on the surface of extracellular vesicles, though not on every vesicle. Because they appear across EV preparations broadly, antibody-based tests for tetraspanins such as CD9, CD63 and CD81 are a standard part of characterization panels used to support a claim that a given particle preparation is in fact composed of EVs.
Detecting a tetraspanin marker alone does not establish a specific vesicle subtype, since these proteins are found across multiple EV populations. Ask which markers and methods were reported for a given product: Bio Xsomes supplier data identify CD81 and CD9 among its reported characterization.
When reviewing characterization documentation, check which specific markers were tested, which assay method was used, and whether the results sit alongside other measurements such as particle size and concentration, rather than standing alone. FDA states there are no FDA-approved exosome products; they are generally regulated as biologic drugs under section 351 of the PHS Act, and purchase and clinical-use decisions belong to the physician and their own regulatory counsel.
Marker testing is one input into a credible characterization package; buyers should expect it alongside other measurements, not as a standalone claim.