Quality documentation guide
What is a COA for Exosomes?
A Certificate of Analysis (COA) for exosomes is the primary quality document that verifies what's in the vial. This guide explains every field that should appear on an exosome COA, what each field means, and how to distinguish meaningful documentation from marketing.
What is a COA?
A Certificate of Analysis is a formal document issued by a manufacturer or testing laboratory that records the quality attributes of a specific batch of material. For exosomes, the COA links a specific lot number to its tested quality parameters — particle size, concentration, markers, endotoxin, and sterility.
A COA is not a marketing document. It is a quality record. If it reads like a product brochure, it's not a COA.
Required fields on an exosome COA
Product identification
What to look for
Product name, catalog number, lot/batch number, manufacture date, and expiry date. The product name should clearly state "exosomes" or "extracellular vesicles" — not "stem cell conditioned media" or "growth factor cocktail."
Why it matters
Without a lot number, there is no way to verify that the COA corresponds to the material you received. Without a clear product name, you cannot confirm you received exosomes at all.
Source material
What to look for
The MSC source (Wharton's Jelly, bone marrow, adipose, etc.), donor eligibility status (21 CFR 1271 for human materials), and passage number if applicable.
Why it matters
The source determines the exosome cargo. Changing sources between lots without notification compromises research reproducibility.
Particle characterization (NTA)
What to look for
Mean and mode particle size (nm), particle concentration (particles/mL), and ideally a size distribution graph. The mean should fall within 50-150 nm for exosomes.
Why it matters
NTA confirms the material contains vesicles in the exosome size range and quantifies how many. Without NTA, "exosomes" is an unsupported claim.
Exosome markers
What to look for
Confirmation of CD9, CD63, and CD81 (tetraspanins) by Western blot or flow cytometry. Ideally, negative controls (calnexin, GM130) should also be reported as negative.
Why it matters
Particle size alone doesn't confirm exosomes — protein aggregates and liposomes can be similar sizes. Marker confirmation is the identity test for exosomes.
Endotoxin level
What to look for
Specific endotoxin value (EU/mL) measured by LAL assay. The acceptance criterion should be stated (e.g., <0.5 EU/mL or <0.25 EU/mL). USP <85> is the standard method reference.
Why it matters
Endotoxins cause inflammatory responses in cell cultures and animal models. "Endotoxin-free" without a measured value is meaningless — everything has some endotoxin level; the question is how much.
Sterility testing
What to look for
Sterility testing result with the method reference (USP <71> is the pharmacopeial standard). The result should state "no growth at 14 days" or equivalent.
Why it matters
Contaminated exosome preparations ruin cell cultures and invalidate in vivo research. Sterility testing with a referenced method is non-negotiable for research-grade material.
Testing laboratory identity
What to look for
The name and address of the laboratory that performed the testing. Is it the supplier's own lab (in-house) or an independent third party (e.g., Eurofins)?
Why it matters
In-house testing creates a conflict of interest. Third-party verification from an independent lab provides the highest confidence that results are accurate and unbiased.
Storage and handling conditions
What to look for
Recommended storage temperature (-20°C or -80°C), light protection requirements, reconstitution instructions, and post-reconstitution storage conditions.
Why it matters
Improper storage degrades exosome quality. The COA should document the conditions that maintain product integrity.
In-house COA vs third-party COA
Manufacturer-issued
The supplier tests its own product and writes its own COA. Creates an inherent conflict of interest. Common but less verifiable. Some reputable suppliers do this — but the question is whether they also offer third-party verification.
Independent lab verification
An independent laboratory (e.g., Eurofins) with no commercial interest in the product performs testing and issues the COA. This is the gold standard. B&H Bio uses Eurofins third-party COA on every batch as standard practice — not "on request."
COA red flags
- "COA available on request"Why would a supplier withhold quality data from a prospective buyer? If the COA exists, it should be provided before purchase.
- Pass/fail without numbers"Purity: Passes" is meaningless. The COA should report quantitative results.
- No lot numberA COA without a lot number cannot be linked to any specific batch — it's a generic template.
- No testing lab identifiedWho performed the testing? No lab name = no accountability.
- "Proprietary blend"If the source material isn't identified, you can't evaluate the product.
- Therapeutic claimsNo exosome product is FDA-approved for therapeutic use. A COA that implies clinical use is misrepresenting the product.
B&H Bio's COA standard
- Third-party Eurofins COA on every batchNot in-house. Not "on request." Standard.
- Lot-linked documentationEvery product, lot, and quality report reconcilable.
- USP <71> sterility criterionPharmacopeial standard testing.
- USP <85> endotoxin criterionQuantitative endotoxin results, not "endotoxin-free."
- 21 CFR 1271 donor eligibilityDocumented source material with donor screening records.
Evaluate the records
Request a sample COA.
Review actual quality records before you evaluate any material.