Particle concentration is one of the basic measurements reported in an extracellular vesicle characterization package, alongside size distribution and marker data. It is generated by a specific analytical method, such as nanoparticle tracking analysis or another particle-counting approach, and the reported number reflects what that instrument and method detected in that sample.
Because different methods and instrument settings can produce different concentration values for the same underlying sample, a concentration figure is only meaningful alongside the method that produced it. MISEV2023 recommends reporting source, size, concentration and markers together, rather than presenting a single number without that context.
Before treating concentration figures from different suppliers as directly comparable, confirm the numbers were generated by comparable methods, and request the full analytical report rather than a summary figure. A concentration number describes what was measured in a preparation; it does not by itself describe any clinical effect. FDA states there are no FDA-approved exosome products; they are generally regulated as biologic drugs under section 351 of the PHS Act, and purchase and clinical-use decisions belong to the physician and their own regulatory counsel.
Concentration figures are only comparable across suppliers when the measurement method is known, which is essential for apples-to-apples vendor evaluation.