Can growth factors penetrate the skin?
Growth factors are large proteins, typically 6 to 25 kilodaltons, well above the classical 500-dalton stratum corneum cutoff. Unaided penetration through intact skin is limited. Topical performance depends on the carrier system, formulation environment, barrier condition, and the surface chemistry of the delivery vehicle. Delivery is therefore part of the active, not an afterthought.
Skincare brands evaluating growth factor ingredients should think about delivery as part of the molecule. A recombinant growth factor on an INCI list does not equal a functional dose at the right cells. The skin barrier is engineered to keep large proteins out, and that is true whether the protein is grown in a microbe, an animal cell, or a plant.
What is the skin barrier and why is it hard to cross? #
The stratum corneum is a 10 to 40 micrometer thick layer of dead, flattened keratinocytes embedded in a lipid matrix. Its purpose is to keep water in and foreign molecules out. Empirically, passive diffusion is reasonable for small lipophilic molecules below about 500 daltons. Most growth factors sit far outside this window.
How big is a growth factor? #
- EGF: about 6 kilodaltons
- FGF-2 (bFGF): about 17 kilodaltons
- KGF (FGF-7): about 19 kilodaltons
- VEGF: about 23 kilodaltons (monomer)
- IGF-1: about 7.5 kilodaltons
Compared to the classical permeability cutoff, growth factors are 10 to 50 times too large to cross intact stratum corneum unassisted.
How delivery systems compare for protein actives #
| System | Mechanism | Practical limits |
|---|---|---|
| Free recombinant protein | Diffusion through any compromised barrier | Limited unaided penetration; stability is the bigger problem |
| Liposomes | Phospholipid bilayer that integrates with skin lipids | Better surface localization; depth depends on lipid composition |
| Nanoemulsions | Small oil droplets with surfactant films | Good spreadability; surfactants can destabilize proteins |
| Microemulsions and hydrogels | Solvent reservoirs that prolong residence time | Improve contact time, not necessarily depth |
| Oleosomes | Native plant lipid droplets with a phospholipid monolayer biomimetic to the skin barrier; the active is fused or anchored to the surface via oleosin | Surface display means the active reaches cells without leaving the carrier; ambient-stable |
How oleosome-based delivery can help #
Oleosomes are native lipid droplets from plant seeds. Their phospholipid surface is chemically similar to the lipids of the stratum corneum, which supports integration rather than rejection. In our platform, the recombinant protein is fused to oleosin and ends up displayed on the outside of the oleosome. The carrier delivers the active to where cells can interact with it, while shielding the protein from oxidation and degradation in the formulation.
This does not mean the protein floods the dermis. It means the system improves localization and functional readouts compared to a free recombinant protein in solution.
How to evaluate penetration evidence #
Brands should ask for functional clinical evidence, not penetration claims. Useful readouts include:
- TEWL changes (barrier-level activity)
- Corneometer hydration (upper stratum corneum)
- Antera 3D or Cutometer (mechanical and topographic dermal change)
- Phototrichogram density or anagen ratio (follicle-level activity)
- Melanin index in hyperpigmented zones (basal epidermal effect)
These are not penetration markers, but they are downstream evidence that the active reached cells capable of responding.
Best for / Not ideal for #
- Premium serums positioned around bioactives
- Recovery and barrier repair products
- Anti-aging products with measurable claims
- Scalp and follicle treatments
- Rinse-off products where the carrier washes away
- Heavy occlusive products that block carrier integration
- Formulas built on penetration-enhancing surfactants that denature proteins
What skincare brands should look for #
- Clarity on which carrier system is used
- Stability and compatibility data in realistic formula bases
- Functional clinical evidence in controlled studies
- Carefully worded claims that avoid drug-like language
Frequently asked questions #
Can growth factors penetrate the skin?
Growth factors are large proteins, so unaided penetration through intact stratum corneum is limited. Topical performance depends on the carrier system, formulation environment, barrier condition, and the surface chemistry of the delivery vehicle.
How big is a growth factor compared to the skin barrier cutoff?
Most growth factors are between 6 and 25 kilodaltons. The classical empirical cutoff for passive stratum corneum permeability is around 500 daltons, so unaided diffusion is unlikely.
Do liposomes help growth factors penetrate?
Liposomes can improve apparent penetration of small encapsulated cargoes and can support surface localization of larger proteins. The actual depth depends on lipid composition and the active itself.
How do oleosomes support topical delivery?
Oleosomes are native plant lipid droplets with a phospholipid monolayer biomimetic to the skin barrier. When an active is anchored to the oleosome surface, the carrier can integrate with the stratum corneum and present the active where cells can interact with it.
Should brands claim deep skin penetration?
Cosmetic regulations limit claims about modifying physiology. Brands should reference functional readouts from controlled studies, not unsupported penetration claims.
For deeper detail on the carrier biology, see our overview of oleosomes. For molecule comparison, see EGF vs FGF-2 in skincare. Underlying platform: platform overview.