Most published descriptions of EV products treat the vesicle as the active ingredient. The truth is more specific. The active ingredient is the vesicle and the layer of biomolecules adsorbed onto its surface. That outer layer, the biomolecular corona, mediates how the EV interacts with the recipient cell membrane. It is not an artefact. It is part of the particle, and it is shaped by the isolation method that produced the preparation.
Two EV preparations isolated from identical biomass by different methods are not the same product. Anyone making purchasing decisions about EV-based actives should understand why.
What the corona is
When an EV is suspended in a biological fluid, proteins, lipids, glycans, and other small molecules from that fluid bind to its outer surface. Some bind tightly through specific high-affinity interactions, forming what is called the hard corona. Others bind through weaker electrostatic and hydrophobic interactions and form a more dynamic soft corona. Both layers contribute to the particle's identity from the perspective of recipient cells.
The corona is functionally meaningful. It influences cellular uptake pathways, determines which receptors on the recipient cell are engaged, and shapes the downstream signalling response. A bare EV with the corona stripped off is biophysically the same particle. Biologically, it behaves differently.
What isolation method does to it
Our group's published work directly tested this: ultracentrifugation and ultrafiltration produce EV preparations from the same starting material that differ measurably in corona composition and functional activity downstream. The two methods do not just yield different particle yields. They yield particles with different surfaces.
The mechanism is straightforward. Ultracentrifugation applies high gravitational force over long periods, which can shear the loose corona, fragment less stable EV subpopulations, and pellet contaminating non-vesicular protein aggregates that then co-isolate with the vesicles. Ultrafiltration uses a size-cutoff membrane and depends on different physical principles; it preserves more of the soft corona but can introduce adsorption losses to the membrane and concentration-dependent aggregation effects. Size exclusion chromatography (SEC) preserves the corona more gently than either, with its own trade-offs in yield and concentration.
None of these methods are wrong. They produce different preparations. The question is whether the preparation that ends up in a commercial product was made with awareness of these trade-offs and characterized accordingly, or whether the corona was simply not on the manufacturer's radar.
What this means for EV product evaluation
Three implications follow.
First, "EVs from species X" is not a complete specification of what the product is. Source biomass plus isolation method together determine the active particle. Two products marketed as "aloe-derived EVs" or "rose-stem-cell exosomes" or "ginger nanovesicles" may carry meaningfully different surface chemistry depending on how they were isolated, even when source is identical.
Second, batch-to-batch consistency in an EV product depends on holding both source variability and processing variability inside narrow specifications. A manufacturer that has not characterized how their isolation method shapes the corona is, by definition, not controlling for one of the two main drivers of lot-to-lot variation.
Third, isolation method should be disclosable to qualified clinical and manufacturing partners. Process secrecy is normal in the supplements industry, and it has no place in characterized EV manufacturing. The method is part of what the product is. BioThera's isolation process is proprietary, with ongoing IP protection, and process transparency documentation is available to qualified partners under appropriate agreement. The standard is "characterized and disclosed under terms," not "undisclosed by default."
Why the field is moving on this
The corona work is part of a broader maturation of the EV field. MISEV2023, the most recent global characterization standard, places explicit emphasis on documenting isolation method and on characterizing not just particle counts but particle properties relevant to function. The corona literature has grown from a handful of foundational studies in the 2010s to a recognized component of EV characterization at the preclinical and clinical levels.
For clinicians and procurement teams: the right question is not "do you preserve the corona." Almost no manufacturer can answer that confidently if they have not done the work. The right question is the one MISEV2023 implies: "what is your isolation method, what does the resulting particle look like in your characterization data, and is that consistent across batches." The corona discussion sits inside that question. It is not a separate audit item. It is part of why the audit matters.