Exosomes vs. Secretome vs. Conditioned Media: What's Actually in the Vial?

By Stem Nova Network | October 2026 | 8 min read | For licensed medical professionals only

Exosomes are one specific part of what cells release; the secretome is everything they release; and conditioned media is the culture fluid that holds the secretome along with leftover culture ingredients. Exosomes (more precisely, small extracellular vesicles) are membrane-bound particles counted by Nanoparticle Tracking Analysis. The secretome also includes the free-floating proteins and other molecules cells release. Conditioned media is the least processed of the three. PDRN and plant-derived "exosomes" are different source materials altogether.

These terms are used interchangeably on product labels, which makes supplier comparisons hard. A vial labeled "exosome" may be a purified vesicle product, a secretome product, or lightly processed conditioned media. This guide defines each category, shows how each is typically measured, and lists the questions that tell you which one you are actually buying.

The Short Answer: Six Terms, Side by Side

What Are Exosomes (Extracellular Vesicles)?

Exosomes are a subtype of extracellular vesicles (EVs): small particles enclosed by a lipid bilayer membrane that cells release into their surroundings. In the scientific literature, the International Society for Extracellular Vesicles (ISEV) recommends the broader term "extracellular vesicles" or "small EVs," because proving that a given particle is an exosome in the strict sense is difficult. On product labels, "exosome" is used loosely for the small EV fraction.

What makes an EV product an EV product is separation. Cells are cultured, the culture fluid is collected, and the vesicle fraction is separated and concentrated. The result can be counted particle by particle using Nanoparticle Tracking Analysis (NTA), which is why EV products are usually labeled with a particle count, such as 77 billion particles per vial.

What Is the Secretome?

The secretome is the complete set of materials a cell population releases. It includes extracellular vesicles, but also soluble proteins and other molecules that float freely in the culture fluid rather than being enclosed in vesicles.

Secretome products are not "less" than EV products or "more." They are a different composition. A secretome product keeps more of what the cells released; an EV product isolates one fraction of it. What matters for comparison is that the label says which one you are buying and how it was measured. A secretome product may report a particle count for its vesicle content, a total protein figure, or both.

What Is Conditioned Media?

Conditioned media is the culture fluid harvested after cells have grown in it. It contains the secretome, but also whatever remains of the original culture medium: nutrients, salts, buffers, and, depending on the process, serum components such as fetal bovine serum (FBS).

Conditioned media is the least processed of these categories. Some products are conditioned media that has been filtered or concentrated; others are sold close to how they were collected. Because the vesicle fraction has not been isolated, conditioned media products are often described by total protein, or by no quantitative measure at all. Total protein can include media proteins that did not come from the cells, so it is not a substitute for a particle count.

Questions that separate the three

• Was the vesicle fraction separated from the culture fluid? If yes, how (for example, ultracentrifugation, tangential flow filtration, or size-exclusion chromatography)?
• Is the particle count measured by NTA on the finished product? Or is the product described only by protein content or volume?
• Was the culture xeno-free and FBS-free? Serum components can carry through into conditioned media and secretome products if not removed.
• What cell source was used, and how was the source tissue screened?

Where Do Growth Factor Serums Fit?

"Growth factor" products are a separate category. Many are formulated around specific named proteins, often produced recombinantly (by engineered microorganisms or cell lines) rather than collected from cultured human cells. They are typically labeled by ingredient and concentration, not by particle count. A growth factor serum is not an exosome product, and an exosome product is not a growth factor serum, even when marketing blurs the two.

Plant-Derived vs. Human-Cell-Derived Exosomes

"Exosome" now appears on a wide range of consumer and professional skincare labels, and many of those products are plant-derived. Plant-derived vesicles are isolated from sources such as fruit, roots, or plant cell cultures. They are a different material from vesicles collected from cultured human cells, and the two are not interchangeable in a supplier comparison.

Neither label is a quality guarantee on its own. The comparison that matters is the same for both: what is the source, how was the vesicle fraction isolated, how was the count measured, and is there a lot-specific COA. Our 2026 pricing guide shows how to compare products by cost per billion particles.

What Is PDRN, and How Is It Different From Exosomes?

PDRN (polydeoxyribonucleotide) is a purified mixture of DNA fragments, most commonly sourced from salmon or trout. It has become one of the most searched skincare ingredients of 2026, and it is frequently compared with exosomes online.

The comparison is a category mismatch. PDRN is not a vesicle, is not produced by cultured human cells, and is not counted by NTA. It is typically labeled by concentration by weight or percentage. Exosome products are vesicle products from cell culture, labeled by particle count. Some topical systems combine categories: NovaRenew, for example, pairs a secretome step with formulation ingredients that include PDRN and GHK-Cu, and is labeled accordingly.

How to Read the Label Before You Buy

Stem Nova Network topical cosmetic biologics are manufactured in the USA in an FDA-registered facility that is cGTP-compliant (21 CFR Part 1271), from xeno-free, FBS-free 3D bioreactor culture, with NTA-verified particle counts and dual-lab COA documentation for every lot.

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