Permeation behaviour of cosmetic actives into the human stratum corneum.
This study highlights that the permeation behavior of cosmetic actives like peptides and vitamin C derivatives is complex and not solely determined by lipophilicity.
Where it sits
this study against the rest of the matrixyl corpusSummary and findings
This study investigated the permeation behavior of cosmetic actives, including peptides and vitamin C derivatives, through the human stratum corneum in three healthy female volunteers. Serum formulations containing 3-O-ethyl ascorbic acid and Matrixyl™ 3000 were applied for exposure times of 0.5, 2, and 5 hours. The study utilized Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Orbital trapping SIMS (OrbiSIMS) to analyze the permeation characteristics.
Abstract
Characterising the permeation of cosmetic actives through human skin is important for understanding their functional performance. Vitamin C derivatives, including 3-O-ethyl ascorbic acid and ascorbyl glucoside, are widely incorporated into skincare formulations for their antioxidant properties, while peptides such as palmitoyl tripeptide-1 (Pal-GHK) and palmitoyl tetrapeptide-7 (Pal-GQPR), present in Matrixyl™ 3000, are employed to promote extracellular matrix remodelling and reduce visible signs of skin ageing. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Orbital trapping SIMS (OrbiSIMS) were used to investigate the in vivo permeation behaviour of these cosmetic actives through the stratum corneum of three healthy female volunteers following topical application of cosmetic serum formulations. Serum formulations containing 3-O-ethyl ascorbic acid and Matrixyl™ 3000 were applied for exposure times of 0.5, 2, and 5 h, while a serum containing ascorbyl glucoside was applied for 0.5 h. Tape stripping of skin combined with SIMS analysis enabled an evaluation of both depth and lateral spatial distributions. For 3-O-ethyl ascorbic acid, the ascorbic acid fragment ion generated during SIMS analysis was used as a permeation marker due to its enhanced ionisation efficiency. A consistent decrease in signal intensity with stratum corneum depth was observed at all exposure times, indicating higher localisation at the surface of the stratum corneum. ToF-SIMS imaging further revealed heterogeneous lateral localisation of ascorbic acid throughout the stratum corneum, decorating corneocyte boundaries. ToF-SIMS depth profiling of ascorbyl glucoside revealed depth-dependent behaviour consistent with partitioning into intracellular regions of the stratum corneum. OrbiSIMS analysis of Pal-GHK and Pal-GQPR detected both peptides throughout every layer of the stratum corneum, demonstrating decreasing ion intensities with depth and no significant changes relative to exposure time. The OrbiSIMS depth profiling demonstrated that the ion intensities for both peptides dropped immediately, suggesting that they were only present on the outer surfaces of the cells and not within them (intercellular). Overall, these findings demonstrated that commonly used predictors such as lipophilicity do not fully determine permeation pathway selection within the stratum corneum and that SIMS-based techniques provide unique mechanistic insight into the spatial distribution and transport routes of cosmetic actives within human skin which will assist in the development of future products.
Background
This paper addresses the permeation behavior of cosmetic actives through the human stratum corneum, which is crucial for understanding their functional performance in skincare. Previous knowledge indicates that vitamin C derivatives and peptides are commonly used in formulations for their purported benefits. Understanding the mechanisms of permeation can inform the development of more effective cosmetic products.
Methods
The study utilized Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Orbital trapping SIMS (OrbiSIMS) to analyze the permeation of cosmetic actives in vivo. Three healthy female volunteers received topical applications of serum formulations containing 3-O-ethyl ascorbic acid, ascorbyl glucoside, and Matrixyl™ 3000. The exposure times for the formulations were 0.5, 2, and 5 hours, with tape stripping of skin performed for analysis.
Results
For 3-O-ethyl ascorbic acid, a consistent decrease in signal intensity with stratum corneum depth was observed at all exposure times. Pal-GHK and Pal-GQPR were detected throughout every layer of the stratum corneum, with decreasing ion intensities relative to depth. No significant changes in ion intensities were noted with varying exposure times for the peptides.
Interpretation
The findings suggest that traditional measures like lipophilicity do not fully account for the permeation pathways of cosmetic actives in human skin. While the study provides valuable insights into the spatial distribution of these compounds, the small sample size and lack of broader applicability limit the conclusions that can be drawn. The results imply that further research is needed to validate these findings in larger populations.
Key findings
- A consistent decrease in signal intensity with stratum corneum depth was observed at all exposure times for 3-O-ethyl ascorbic acid.
- ToF-SIMS imaging revealed heterogeneous lateral localisation of ascorbic acid throughout the stratum corneum.
- Depth profiling of ascorbyl glucoside showed depth-dependent behaviour consistent with partitioning into intracellular regions of the stratum corneum.
- Pal-GHK and Pal-GQPR were detected throughout every layer of the stratum corneum, demonstrating decreasing ion intensities with depth.
- Ion intensities for both peptides dropped immediately, indicating they were only present on the outer surfaces of the cells.
Limitations
- small sample size of three healthy female volunteers
- results may not be generalizable to broader populations
- short exposure times may not capture long-term permeation effects
- no clinical outcomes reported