P24 In vivo permeation of cosmetic actives into the human stratum corneum assessed by secondary ion mass spectrometry
Anna Trzaska, Mark O’Mahony, Mike Bell, Nichola Starr, Rian Griffiths, Morgan Alexander, David ScurrAbstract
Introduction and aims
Understanding how cosmetic actives permeate the stratum corneum (SC) is essential for establishing both safety and functional performance. Vitamin C derivatives and palmitoylated peptides such as palmitoyl tripeptide-1 (pal-GHK) and palmitoyl tetrapeptide-7 (pal-GQPR) are used in cosmetic formulations for improving the signs of skin ageing. However, the impact of exposure time on permeation and spatial distribution of actives within the SC is currently limited. This study aims to determine time-dependent permeation behaviour using high-resolution secondary ion mass spectrometry (SIMS) techniques.
Methods
Two different formulations containing vitamin C and pal-GHK/pal-GQPR were applied at 2 mg cm−2 to the volar forearms of three healthy female volunteers (Fitzpatrick skin type I/II, < 35 years). Tape stripping (15 consecutive D-Squame® strips) was conducted after exposure time of 0.5, 2 and 5 h. Tape strips 2, 8 and 14 were analysed using two different mass spectrometry techniques [time-of-flight (ToF)-SIMS and OrbiSIMS].
Results
ToF-SIMS was able to detect and image the presence of vitamin C within the skin tape strips. The data showed a decline in ion intensity with depth, with no statistically significant differences between skin exposure times. Lateral distribution analysis observed vitamin C at the edges of corneocyte cells within the SC. OrbiSIMS enabled unambiguous detection of both peptides, which was not achieved by ToF-SIMS. Pal-GHK and pal-GQPR intensities decreased sharply with depth, with no exposure time dependencies. Depth profiles for both peptides mirrored those of endogenous SC lipids, indicating localization predominantly within the intercellular lipid matrix.
Conclusions
Under the exposure times tested, vitamin C, pal-GHK and pal-GQPR were detected within the SC with no enhancement in permeation at longer exposure times, suggesting that delivery happens quickly. Peptide spatial profiles support an intercellular permeation pathway. These findings demonstrate the value of SIMS-based analysis and imaging for resolving the behaviour of actives within the SC.