How to read “10 billion particles/mL”: NTA, TEM and the COA questions to ask

Particle concentration is the number most often printed on exosome products, and the one buyers find hardest to verify. This article explains what the figure means and how to ask for evidence in a way that suppliers can answer clearly.

Why are exosomes counted, not weighed?

Exosomes are vesicles roughly in the tens to low hundreds of nanometers. Their effect in a formula depends on how many are present, so the industry states concentration as particles per millilitre. Mars exosome serums state 10 billion particles/mL (10¹⁰/mL).

What is NTA?

Nanoparticle tracking analysis (NTA) illuminates particles in a liquid with a laser and tracks their movement under a microscope camera. Software uses that movement to estimate each particle’s size and to count particles in a known volume. The result is typically a size distribution chart and a concentration figure.

What is TEM?

Transmission electron microscopy (TEM) produces images at very high magnification. For exosomes, TEM is used to show that particles have the expected cup or round shape and fall within an expected size range. It is visual confirmation rather than a high-throughput count.

What should a useful COA tell you?

A certificate of analysis (COA) is a batch document. To make it meaningful for your purchase, check that it states:

• the batch or lot number that matches the goods you receive;
• the test methods used for each parameter;
• whether figures refer to the powder or the activated serum;
• basic quality parameters such as appearance and microbiology.

Alongside the COA, ask for the MSDS and the full INCI list. If you are registering the product in a new market, tell the supplier early which documents your regulator or importer expects.

Questions to send your supplier

1. Which batch does this COA describe, and will my shipment come from it?
2. Which method was used to determine particle concentration?
3. Does the stated concentration refer to the activated serum?
4. Can you share MSDS and INCI for label and registration work?

We supply MSDS and COA per batch on request, and the INCI list for every product. Read more on our quality and documentation approach, or request documents for a specific product.