Particle Count Isn't Purity: The Five Lines That Decide Your Pilot
Two exosome spec sheets land on your desk. Both say "1 × 10¹⁰ particles/mL." One is worth a pilot; the other is worth walking away from. The difference is invisible until you read each line for what it proves — and for what it never measured.
What particle count actually proves
Particle count (NTA-measured, per mL) proves one thing: the product contains nanoscale particles at a stated density. It does not prove those particles are exosomes, that they carry useful cargo, or that they are free of protein aggregates that also scatter light. NTA counts everything in the size window — which is why serious spec sheets pair it with TEM morphology and state the method, the instrument class, and the dilution factor.
Buyer's question one: "Concentration measured by which method, against which guideline?" A sheet anchored to a published guideline — ours follows national guideline 2026 No. 17, which TONGNIAN helped draft — is comparable across batches. An unanchored number is comparable to nothing.
The five lines that matter more than the count
| Line | What to look for | Red flag |
|---|---|---|
| Size distribution | 80–150 nm (or stated range) + method | A single number ("~100 nm") with no distribution |
| Protein content | mg/mL with ratio context | Absent — aggregates may be doing the counting |
| Endotoxin | EU/mL against a printed release limit | "Tested" without a limit |
| Sterility / microbial | Negative on release, method stated | Absent on topical/oral formats |
| Payload or purity | Marker or protein-ratio check | "Proprietary" in place of a figure |
The five questions that turn a sheet into a comparison
- Which measurement guideline does the release panel follow?
- What is the recovery rate of the purification line (can they even state one)?
- What percentage of candidates did the seed screening keep?
- Does a retain sample exist for this batch, and for how long?
- Which filings cover the material line (INCI, DMF, or market equivalent)?
A supplier who answers five of five in one email is rare — and is the one to pilot with.
Every TONGNIAN spec sheet is written to pass this reading: request one and run the five questions. For the deeper document behind the sheet, see the COA reading guide, or the line fact-sheets for program-level specs.
Get the test panel that matches your batch
Tell us your target category and expected first batch size (a sample run, around 100 units, or 1,000 and up). We will send the matching test panel, characterization references, and a sample COA for your tier.