Quality, Testing & COAs
How to Read an Exosome Certificate of Analysis (COA)
A plain-English walkthrough of an extracellular-vesicle Certificate of Analysis: lot numbers, analytical methods, particle concentration, particle size, characterization, specifications and results.
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When evaluating an extracellular-vesicle product, you'll often hear the term Certificate of Analysis, or COA.
At first glance, a COA can look intimidating.
It may contain lot numbers, particle concentrations, laboratory methods, sterility results, specifications and terminology that isn't immediately meaningful if you don't work in a laboratory.
But the basic purpose is straightforward:
A COA provides documented information about a particular product or batch and the testing associated with it.
Learning how to read one can help you move beyond marketing claims and look at the actual information supplied about a product.
What Is a Certificate of Analysis?
A Certificate of Analysis is a quality document associated with a product, material or manufacturing lot.
Depending on the manufacturer and product, it may contain information such as:
- product identification
- lot or batch number
- manufacturing or testing information
- analytical methods
- specifications
- measured results
- particle concentration
- particle-size information
- sterility or microbiological testing
- other quality-control results
Not every COA contains the same tests or uses the same format.
That's important.
A COA isn't valuable simply because a document called a “COA” exists. The useful information is what was actually tested, how it was tested, and what the results show.
Start With the Product and Lot Number
One of the first things to look for is product identification.
A COA should make it possible to determine which product or material the document describes.
Then look for the lot or batch number.
This matters because testing is often performed on material associated with a particular production lot.
If you're evaluating a specific vial or product, a useful question is:
Does the lot number on the product correspond to the lot documented on the COA?
A generic COA from some unrelated batch doesn't provide the same batch-specific information.
That's one reason Express Biologics emphasizes batch-specific COA availability.
Look at What Was Actually Tested
Next, don't simply scan the page looking for words like “passed.”
Look at the tests themselves.
Depending on the EV preparation and the manufacturer's testing program, a COA may report information related to:
Particle concentration
How many detectable particles were measured within a specified volume or sample.
Particle-size distribution
Information about the sizes of particles detected in the preparation.
Characterization
Additional analytical information used to describe the extracellular-vesicle preparation.
Sterility or microbiological testing
Testing intended to evaluate microbial contamination.
Other quality-control measurements
Additional specifications established by the manufacturer for the particular product.
The exact testing panel can vary considerably between products and manufacturers.
Particle Count
Particle count is one of the most noticeable measurements on an exosome COA because the numbers can be very large.
For example:
4 × 10¹⁰ particles/mL
means:
40 billion particles per milliliter.
When reading this measurement, pay attention to whether the COA reports a concentration or a total quantity, the volume associated with the measurement, and the analytical method used.
Particle information is commonly presented alongside other characterization data, such as particle-size measurements and EV-associated markers, to provide a more complete description of the preparation.
For a deeper explanation of particle measurements, see Understanding Exosome Concentration and Particle Count.
Look at the Analytical Method
A number becomes much more informative when you know how it was measured.
One technique you may encounter is nanoparticle tracking analysis (NTA); other analytical approaches are also used for EV characterization, and each has different capabilities and detection limitations — Understanding Exosome Concentration and Particle Count explains how NTA works.
The analytical method tells you how the laboratory determined the reported particle number, providing important context for interpreting the result.
Understand the Difference Between a Specification and a Result
COAs may present information in columns such as:
| Item | Specification | Result |
|---|---|---|
| Example measurement | Established acceptance criterion | Measurement obtained for the lot |
A specification describes the manufacturer's established criterion or acceptable range for a particular test.
A result reports what was measured for the specific lot being documented.
When a result is marked Pass, it means the reported result met the applicable acceptance criterion for that test.
Reading the specification and result together shows you both what standard was applied and how that particular lot performed against it.
What Does “Characterization” Mean?
Characterization is one of the most important concepts in extracellular-vesicle science.
As explained in How Are Exosomes Produced and Processed?, processing or purification and characterization aren't the same thing.
Processing concerns how material is separated and refined.
Characterization asks:
What properties does the resulting preparation have?
Researchers can examine characteristics such as:
- particle concentration
- particle-size distribution
- morphology
- EV-associated proteins
- proteins or other components that may indicate non-EV material
- additional physical or biochemical properties
MISEV2023 specifically addresses EV characterization and technique-specific reporting because no single measurement completely describes an extracellular-vesicle preparation.
We'll examine those techniques more closely in Understanding Extracellular Vesicle Characterization and Testing.
What About Sterility Testing?
For biologically derived materials, microbiological quality-control information provides another important category of documentation.
Depending on the manufacturing and testing program, documentation may include testing related to:
- sterility
- aerobic microorganisms
- anaerobic microorganisms
- other microbial or contamination controls
Sterility testing is a distinct quality-control function from EV characterization.
In other words:
Particle analysis asks questions about the particle population.
Microbiological testing asks questions about microbial contamination.
Those are different questions, and both can appear within a broader quality program.
Research examining manufacturing-quality systems for EV preparations likewise treats sterility testing as a distinct quality-control consideration.
What HydroKarma's Documentation Includes
HydroKarma/KWEHEALTH provides batch-specific documentation associated with its products.
The documentation reports an EV quantity of 50 billion EV per 3 mL vial. According to KWEHEALTH, HydroKarma's 50-billion designation means 50 billion exosomes per vial, in addition to other extracellular vesicles naturally present in the product. The finished preparation also contains naturally occurring growth factors, cytokines, proteins and other signaling molecules.
According to KWEHEALTH's supplied COA documentation, its quality process includes donor screening and source-material controls as well as testing associated with manufactured lots.
The documentation describes donor screening that includes:
- communicable-disease serology
- medical-history review
- physical examination
- behavioral risk assessment
- additional information relevant to donor suitability
As we explain in How Are Exosomes Produced and Processed?, HydroKarma's process begins with human amniotic fluid rather than collecting extracellular vesicles from cultured-cell-conditioned media.
The supplied documentation also describes manufacturing using aseptic techniques within an ISO-certified controlled environment and quality-assurance/environmental monitoring associated with product lots.
KWEHEALTH also states that a subset of the finished product vials is sent out for safety testing and total exosome-count testing, and that the finished product is released for distribution once those results are acceptable.
That information provides context about the manufacturer's quality program in addition to the analytical measurements reported for the material itself.
These HydroKarma-specific statements come from KWEHEALTH/HydroKarma's supplied product documentation; they should not be interpreted as findings from the independent scientific papers cited in this article.
Want to Walk Through a COA Step by Step?
Reading the individual measurements is easier when you can see where they appear on the actual document. Visit Understanding Your Certificate of Analysis on our Quality page for a guided walkthrough of a HydroKarma Certificate of Analysis and an explanation of the major sections, measurements, and testing information.
The Bottom Line
A Certificate of Analysis provides a window into the testing and documentation associated with a particular product or manufacturing lot.
When reading an extracellular-vesicle COA, pay particular attention to:
lot identification → analytical methods → particle concentration → particle size → characterization → microbiological testing → specifications → actual results
A well-documented COA gives you lot-specific information about the testing performed, the methods used and the results reported for the product.
Original Source / References
Continue Learning
Understanding Extracellular Vesicle Characterization and Testing
Characterization is how laboratories measure and describe different properties of an extracellular-vesicle preparation — particle count, particle size, EV-associated markers, total protein and zeta potential — and why no single test describes everything.
Understanding Exosome Concentration and Particle Count
A particle count can provide useful information about a sample, but the number needs context: how it was measured, the volume it represents, the size distribution, and what else may be present.