Extracellular vesicles: a working definition
Extracellular vesicles (EVs) are small, membrane-bound particles released by cells into their surrounding environment. They come in several subtypes that differ by size and how they form inside or at the surface of a cell; "exosome" refers specifically to one subtype believed to form through a particular intracellular pathway before being released. In commercial preparations, confirming that a batch of particles are specifically exosomes, rather than EVs more broadly, requires demonstrating that formation pathway, which is harder to do than simply measuring particle size or count.
This distinction is why terminology matters for a clinic evaluating a product. A supplier describing a product as an "exosome" product is making a more specific claim than describing it as an "extracellular vesicle" product, and that claim should be backed by the kind of characterization data described below.
Why MISEV2023 guidance recommends careful terminology
The Minimal Information for Studies of Extracellular Vesicles (MISEV2023) guidelines, a widely referenced position statement in the EV research field, recommend that preparations be described as "extracellular vesicles" unless exosome-specific biogenesis has actually been demonstrated for that material. The guidelines also recommend that any report on an EV preparation include its source, particle size distribution, concentration, and marker profile, rather than a single headline number presented without that context.
Applying this guidance to procurement means asking a supplier not just "how many exosomes are in this vial," but what source material and cell line the particles came from, what isolation method was used, and what evidence supports calling them exosomes specifically rather than EVs generally.
How EV and exosome products are characterized in a lab
Common characterization methods include nanoparticle tracking analysis (NTA), which measures particle size distribution and concentration by tracking light scattering from individual particles in suspension; ELISA, an antibody-based assay used to detect specific proteins associated with the preparation; and single particle interferometric reflectance imaging sensing (SP-IRIS), which can identify and count particles displaying specific surface markers at the single-particle level.
Bio Xsomes supplier characterization identifies CD81 and CD9; these are analytical findings, not clinical-effect claims. A characterization report that names the specific methods used and the specific markers identified is meaningfully more informative than a product description that simply states a particle count without that supporting detail.
Regulatory status: why no exosome product carries FDA approval
FDA has stated publicly that there are no FDA-approved exosome products on the market. Extracellular vesicle and exosome preparations are generally regulated as biologic drugs under section 351, a different regulatory pathway than the section 361 framework sometimes discussed for certain tissue allografts. This pathway requires its own licensing process rather than falling under tissue-donation rules. No exosome product should be described as a section 361 HCT/P.
Purchase and clinical use decisions for any EV or exosome product are matters for the ordering physician and their own regulatory counsel to evaluate directly; this article is informational and is not legal advice, and a supplier's description of its own regulatory posture should be independently verified rather than relied on as settled fact.
These products are not FDA approved or licensed for any disease or condition. Information is for licensed healthcare professionals and is not medical or legal advice.
What to request from an EV or exosome supplier
Before treating a particle count or marker claim as established, a buyer can reasonably ask for the specific characterization methods used on that lot, the source cell line or tissue, the isolation method, and documentation of marker identification. Supplier-provided literature and characterization data are a starting point for this review, not a substitute for independent verification.
- Source cell line or tissue and isolation method used
- Characterization methods applied (e.g., NTA, ELISA, SP-IRIS) and results
- Specific markers identified (e.g., tetraspanins CD9/CD81) and how
- Lot-specific documentation rather than a general product claim
Frequently asked questions
Is an exosome the same thing as an extracellular vesicle?+
An exosome is one specific subtype of extracellular vesicle. MISEV2023 guidance recommends using the broader term "extracellular vesicle" unless exosome-specific biogenesis has actually been demonstrated for that preparation.
Are any exosome products FDA approved?+
No. FDA has stated there are no FDA-approved exosome products, and these preparations are generally regulated as biologic drugs under section 351, rather than under the tissue-donation framework.
What lab methods are used to characterize exosome or EV products?+
Common methods include nanoparticle tracking analysis (NTA) for size and concentration, ELISA for protein detection, and single particle interferometric reflectance imaging sensing (SP-IRIS) for marker-based particle identification. Tetraspanin marker testing, such as CD9 and CD81, may also be reported.
Can an exosome product be classified as a section 361 HCT/P?+
No. Exosome products are not described as section 361 HCT/Ps; they are generally regulated as biologic drugs under section 351, and this determination should be reviewed with regulatory counsel.