Exosomes & Extracellular Vesicles

Exosome is the familiar word; extracellular vesicle (EV) is the term the research community now prefers. Here is what these particles are, where they come from, how they are separated and how they are counted.

Last updated October 7, 2026For licensed medical professionals7 peer-reviewed and regulatory sources

In short

Extracellular vesicles are nano-sized particles enclosed by a lipid membrane that cells release into their surroundings. "Exosome" refers to a subtype of endosomal origin, which is hard to prove in a finished product, so the MISEV2023 guidelines recommend "EV" as the general term. EVs are not cells: they contain no nucleus and cannot divide. Stem Nova exosome products are topical cosmetic products, counted by nanoparticle tracking analysis (NTA).

Exosome, EV, secretome: the terms

Term What it means
Extracellular vesicle (EV) Any membrane-enclosed particle released by cells that cannot replicate on its own. The general term recommended by MISEV2023.
Exosome An EV subtype formed inside the cell's endosomal system. Widely used commercially; the strict definition requires evidence of origin.
Secretome Everything cells release into culture media, including EVs and soluble proteins.
Conditioned media Culture media collected after cells have grown in it; the starting material for EV processing.

Where EVs come from

Cells release several kinds of vesicles, which differ in where they form and how large they are. Reviews by van Niel and colleagues and by Doyle and Wang summarize the main groups:

Size comparison of extracellular vesicle types on a 10 nm to 10 micrometer scale: exosomes about 30 to 150 nm forming inside the cell in a multivesicular body, microvesicles about 100 to 1,000 nm budding from the cell surface, and apoptotic bodies about 1 to 5 micrometers.
EV types by size. Exosomes form inside the cell in multivesicular bodies; microvesicles bud from the cell surface; apoptotic bodies are much larger. Note the scale is logarithmic. Illustration.
EV type Where it forms Typical size
Exosomes Inside the cell, as small vesicles within multivesicular bodies (an endosomal compartment), released when that compartment fuses with the cell surface About 30–150 nm
Microvesicles Budding outward directly from the cell's outer membrane About 100–1,000 nm
Apoptotic bodies Fragments released by cells undergoing programmed cell death About 1–5 µm

Size ranges overlap, which is why a size measurement alone cannot prove a particle is an exosome.

How exosomes form

  1. EndosomeThe cell takes in part of its outer membrane, forming an internal compartment called an early endosome.
  2. Multivesicular bodyThe endosome's membrane folds inward, filling the compartment with small intraluminal vesicles.
  3. ReleaseThe multivesicular body fuses with the cell's outer membrane and releases those vesicles. Once outside, they are called exosomes.

What an EV is made of

Kalluri and LeBleu describe exosomes as averaging about 100 nanometers across, with contents that reflect the cell they came from. In structural terms, an EV has:

Cutaway of a single extracellular vesicle about 100 nm across, labeled lipid bilayer membrane, tetraspanin markers CD9, CD63 and CD81, proteins, lipids and nucleic acids.
Structure of an extracellular vesicle. A lipid bilayer membrane carrying tetraspanin markers (CD9, CD63, CD81), enclosing proteins, lipids and nucleic acids. Illustration, not to exact scale.
  • A lipid bilayer membrane, the same basic structure as a cell membrane, enclosing the vesicle.
  • Membrane proteins, including tetraspanins such as CD9, CD63 and CD81, which are used as identification markers in characterization.
  • Internal contents: proteins, lipids, nucleic acids and metabolites carried from the parent cell.
  • No nucleus. EVs cannot divide or grow, so they are counted as particles, not cells.

EVs are not stem cells

Extracellular vesicles MSCs (cells)
Living cells? No Yes
Can divide? No Yes
Typical size Roughly 30–200 nm Roughly 15–30 µm
How it is counted Particles per mL by NTA Cell count and viability
Stem Nova category Topical cosmetic Individualized biologic, not FDA-approved

How EV products are made

  1. Cell sourceA characterized cell population, for Stem Nova umbilical cord tissue-derived MSCs.
  2. CultureCells are expanded, at Stem Nova in 3D bioreactor systems.
  3. CollectionConditioned media containing the secretome is collected.
  4. Separation and concentrationMedia is clarified to remove cells and debris, then EVs are separated and concentrated.
  5. Characterization and releaseParticle concentration and size by NTA, plus sterility, endotoxin and mycoplasma testing, documented on the lot's Certificate of Analysis.

How EVs are separated

There is no single standard method. Each separates EVs from other material by a different property, with trade-offs in yield, purity and scale (Doyle & Wang 2019; MISEV2023).

Method Separates by Trade-offs
Ultracentrifugation Density and size, by spinning at very high speed Long-established; time-consuming and hard to scale
Tangential flow filtration (TFF) Size, by flowing media across a membrane Scales to large volumes; Haraszti 2018 reported higher yield with TFF
Size-exclusion chromatography Size, by passing sample through a porous column Gentle and good at removing free proteins; limited volume per run
Ultrafiltration Size, by pressing media through a membrane Fast concentration; can also concentrate non-EV proteins
Precipitation Solubility, using polymers that pull particles out of solution Simple; can co-precipitate non-EV material

How EVs are counted: NTA

Nanoparticle tracking analysis shines a laser through a diluted sample and records the Brownian motion of individual particles. Software converts each particle's movement into a size and counts particles per milliliter. Dragovic and colleagues showed NTA can size vesicles down to about 50 nm.

Illustrative nanoparticle tracking analysis report showing a particle size distribution curve, a scattering video frame, mean size, concentration, D10 to D90 range and a size-bin table.
Illustrative NTA report layout. A size-distribution curve, a frame from the scattering video, summary statistics and size bins. Example values only; this is not Stem Nova lot data.

Reading an NTA report

Field What it tells you
Concentration Particles per mL in the measured sample, corrected for dilution
Mean and mode size The average particle size and the most common size
D10 / D50 / D90 The sizes below which 10%, 50% and 90% of particles fall; a narrow range means a more uniform population
Size distribution curve How many particles were seen at each size; extra peaks can point to aggregates or other particles
Dilution factor How much the sample was diluted to measure; the reported concentration should already account for it

From concentration to labeled count. Particles per vial = concentration × fill volume. For example, 3.3 × 1010 particles/mL × 2 mL = 6.6 × 1010, or 66 billion particles per vial.

Beyond particle counts

NTA counts any particle in range, so a particle counter cannot tell a vesicle from a similar-sized particle on its own. MISEV2023 recommends pairing counts with other characterization:

  • EV-associated proteins such as CD9, CD63 and CD81, detected by methods like western blot or flow-based assays
  • Imaging by electron microscopy to show vesicle shape and membrane
  • Purity ratios. Webber and Clayton proposed comparing particle count to total protein; more particles per microgram of protein suggests less free protein carried along

Stem Nova exosome products

Product Labeled particles (NTA) Use category
3DEXO+ 60B Exosome Matrix 60 billion per vial Topical cosmetic
Nova Core Secretome Concentrate 66 billion per 2 mL Topical cosmetic
Dermal Papillary Secretome Matrix+ 150B 150 billion per 1.8 mL Topical cosmetic
3DEXO+ 12B Exosome Matrix 12 billion per 10 mL Topical cosmetic

Products are manufactured in the USA in an FDA-registered facility, cGTP-compliant (21 CFR Part 1271). Each lot is NTA-verified with dual-lab COA documentation.

What to ask your supplier

  1. How was the particle count measured, and was it measured on this lot?
  2. What are the mean size and D10–D90 range?
  3. Which separation method is used: ultracentrifugation, TFF, size-exclusion or precipitation?
  4. Is the count supported by marker or purity data, not NTA alone?
  5. What cell source and culture method were used: 2D flasks or a 3D bioreactor?
  6. Which release tests are on the COA: sterility, endotoxin, mycoplasma? From which laboratories?
  7. Is the product labeled and sold as a topical cosmetic?

Frequently asked questions

Are exosomes stem cells?

No. Extracellular vesicles are particles released by cells. They contain no nucleus, are not alive and cannot divide.

What is the difference between "exosome" and "EV"?

Exosomes are an EV subtype defined by how they form inside the cell. Because that origin is hard to confirm in a finished product, the MISEV2023 guidelines recommend "extracellular vesicle" as the general term.

What does "NTA-verified" mean?

The particle count and size distribution were measured by nanoparticle tracking analysis on the lot, and the result appears on the Certificate of Analysis.

Does a higher particle count mean a higher-quality product?

Not by itself. The count tells you how many particles fall in the measured size range. Size distribution, purity, separation method and lot testing complete the picture.

Why can two products with the same label count differ?

They may use different cell sources, culture systems, separation methods and measurement settings. Ask for the NTA report, the size range and the method behind the number.

How are Stem Nova exosome products classified?

They are topical cosmetic products. They are not drugs and are not FDA-approved.

References

  1. Welsh JA, Goberdhan DCI, O'Driscoll L, et al. J Extracell Vesicles. 2024;13(2):e12404 (MISEV2023). doi:10.1002/jev2.12404. Cited for: EV nomenclature and characterization guidance.
  2. van Niel G, D'Angelo G, Raposo G. Nat Rev Mol Cell Biol. 2018;19(4):213-228. doi:10.1038/nrm.2017.125. Cited for: EV types and biogenesis.
  3. Doyle LM, Wang MZ. Cells. 2019;8(7):727. doi:10.3390/cells8070727. Cited for: EV types and isolation methods.
  4. Kalluri R, LeBleu VS. Science. 2020;367(6478):eaau6977. doi:10.1126/science.aau6977. Cited for: exosome size and composition.
  5. Dragovic RA, Gardiner C, Brooks AS, et al. Nanomedicine. 2011;7(6):780-788. doi:10.1016/j.nano.2011.04.003. Cited for: nanoparticle tracking analysis of vesicles.
  6. Webber J, Clayton A. J Extracell Vesicles. 2013;2:19861. doi:10.3402/jev.v2i0.19861. Cited for: particle-to-protein purity ratio.
  7. Haraszti RA, Miller R, Stoppato M, et al. Mol Ther. 2018;26(12):2838-2847. doi:10.1016/j.ymthe.2018.09.015. Cited for: 3D microcarrier vs. 2D EV yield.

Citations support manufacturing, characterization and sourcing facts only. They are not claims about any Stem Nova product's effect in the body.

Source with the paperwork in hand

Licensed MD, DO, NP and PA practices can apply for wholesale access. Lot documentation is available for review, and applications are typically approved within 24 hours.

Apply for wholesale accessTalk to our team

For licensed medical professionals only. Exosome products are topical cosmetic products. hUCT-MSC products are individualized and not FDA-approved; use is clinician-directed, and patients should consult their primary care provider. Stem Nova Network does not provide dosing or procedural guidance. Products are not intended to diagnose, treat, cure, or prevent any disease. Stem Nova Network is a DBA of D1D Enterprises, Inc.