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Quality reference

CD9, CD63, and CD81 Marker Panels

Reviewed by ExaVeyra Sciences editorial team · Updated 29 August 2026

Three markers appear on almost every exosome data sheet in the industry, usually as a row of ticks: CD9, CD63, CD81. Presented that way they look like a specification being met, and they are not. They are the result of a measurement, and the measurement has a number attached that the ticks leave out.

This page covers what those three proteins establish, why the proportion of particles carrying them is the figure worth asking for, and why two honest suppliers can report different answers for the same material.

What a tetraspanin panel establishes

CD9, CD63 and CD81 are membrane proteins enriched in small extracellular vesicles. Finding them supports the claim that what is in the vial came from the vesicle pathway rather than being debris, protein aggregate or free-floating cargo.

That is a useful thing to establish and a narrow one. No tetraspanin result speaks to potency, purity, sterility or suitability, and none of them is a specification a preparation can pass.

Ask for the fraction, and the panel starts working for you

A marker being present tells you it was detected somewhere in the sample. What a purchaser wants to know is how much of the material carries it, because a preparation where a small minority of particles are tetraspanin-positive is a different product from one where most are.

Measured work makes this concrete: tetraspanin positivity varies systematically with vesicle size, so the same preparation reports differently depending on which part of the size distribution an instrument can see.

Two honest labs can disagree, because the platform changes the answer

Single-particle platforms differ in what size of vesicle they can resolve and how faint a signal they can call positive. Comparisons across instruments show that the same material produces materially different counts and positivity fractions depending on the platform.

So a difference between two certificates is not automatically a discrepancy. Without the method named on both, there is nothing to compare, which is why the method line matters as much as the result.

How to read a negative result accurately

A negative result can mean the protein is genuinely absent, or that it sits below the detection limit of the instrument used. Those are different conclusions and a certificate rarely distinguishes them.

The same applies to markers nobody looked for. An attribute that was never assayed does not appear on the document, and its absence reads identically to a clean result.

What a good marker section looks like

  • Each marker named, with the assay and instrument used to measure it.
  • A measured value per marker, expressed as a percentage of particles, not a tick.
  • The size range the instrument resolves, since positivity varies across it.
  • Whether the result is lot specific or carried over from a process validation.
  • At least one negative control marker, which is what distinguishes a panel from a list.

A package with all five is uncommon. A supplier who can produce three of them is already ahead of a data sheet showing three ticks and a logo.

How to get marker data for a specific lot

Marker percentages with the assay named are a normal request, and the answer either exists or it does not. A supplier who measures routinely can attach the figures to the lot you are quoted on.

ExaVeyra provides characterisation data with lot-specific certificates to NPI-verified practices. Verification is the step that opens pricing, the formulary and the supporting documentation at once.

Sources

  1. 21 CFR Part 1271, human cells, tissues, and cellular and tissue-based products (accessed 29 August 2026)

Scientific literature

Each source carries the kind of study it was and, where the study enrolled people, how many. Study design decides what a result can establish, so it is stated rather than left to be inferred. Each line also says what that source is carrying on this page.

  1. Arab T, Mallick ER, Huang Y, et al. Characterization of extracellular vesicles and synthetic nanoparticles with four orthogonal single-particle analysis platforms. Journal of Extracellular Vesicles, 2021. doi:10.1002/jev2.12079 PMID:33850608In vitroSource 1 supports: The same preparations measured on four single-particle platforms. Cited as the direct evidence that a result is not separable from the instrument that produced it, which is the argument for asking what method was used before comparing two certificates.
  2. Fagúndez P, Olivera Á, Gololobova O, et al. Tetraspanin positivity as a function of extracellular vesicle size measured by a modified immuno-TEM protocol. ACS Applied Bio Materials, 2025. doi:10.1021/acsabm.5c00591 PMID:40669512In vitroSource 2 supports: Tetraspanin positivity measured across the vesicle size distribution rather than as a single figure. Cited for the specific point that the fraction reported depends on which sizes the instrument can see.
  3. Kim J, Xu S, Jung SR, et al. Comparison of EV characterization by commercial high-sensitivity flow cytometers and a custom single-molecule flow cytometer. Journal of Extracellular Vesicles, 2024. doi:10.1002/jev2.12498 PMID:39140467In vitroSource 3 supports: Commercial instruments compared against a higher-sensitivity reference. Cited for the detection-limit point: a negative result can mean absent or merely below what the instrument can call.
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Common questions

Are CD9, CD63 and CD81 required markers?
They are conventional rather than required. No United States regulation specifies a marker panel for these preparations, and the reporting standards in this field describe categories of marker to report rather than a fixed list. They are the ones most widely measured, which makes them useful for comparison between suppliers.
Is a preparation with all three markers better than one with two?
Not on that basis alone. The count of markers detected says less than the fraction of particles carrying each one and the method used to measure it. Three markers reported as ticks carries less information than one marker reported as a measured percentage with its assay named.
Why do two certificates for similar material disagree?
Most often because the platforms differ. Instruments vary in the vesicle sizes they resolve and the threshold at which they call a particle positive, and published comparisons across platforms show the same material giving different results. Compare method first, then numbers.
Does a marker panel tell us anything about potency?
No. Tetraspanin data supports the claim that the material is vesicular in origin. It is not a potency assay, it is not a purity measure, and it does not indicate suitability for any patient or procedure, which remains a prescriber determination.

Related reading

MISEV2023 and supplier documentationQualifying a supplier before the first orderHow to evaluate an exosome supplier COAEvaluating an exosome supplierExosome CMC requirements

These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease. There are no FDA-approved exosome products. Biomolecular signaling vesicle products distributed by ExaVeyra Sciences are supplied for topical aesthetic treatments in clinics and for medical, molecular biology, and biochemistry research applications, and are not tissue products as defined by FDA guidelines.

This guide summarizes publicly available federal regulation for licensed practitioner education. It is for informational purposes only, it is not legal advice, medical advice, or regulatory guidance, and it does not establish that any particular product or practice is compliant. Regulation changes, and state requirements frequently differ from the federal floor. Consult a healthcare attorney licensed in your jurisdiction and your own state boards before acting on anything here.