David James Scurr oral presentation (OB3-Tue4-2-1)
3D Chemical Imaging of Skin Permeation
1 University of Nottingham, Science Road, NG7 2RD Nottingham, United Kingdom
2 Walgreens Boots Alliance, 1 Thane Road West, NG90 1BS Nottingham, United Kingdom
This work presents the use of time of flight secondary ion mass spectrometry (ToF-SIMS) as an emerging tool for skin analysis, offering the ability to monitor the distribution of xenobiotic compounds. This work has demonstrated the ability to analyse individual tape stripped layers of human stratum corneum for both native and following application of a topical compound. The sensitivity of the technique has also enabled the detection of analytes from native human in vivo samples highlighting differences in the lipid composition of the stratum corneum relating to both intrinsic and extrinsic aging effects . In aged samples a significant increase was observed for cholesterol sulfate, (localised in ‘pools’), which has been shown to play a key role in skin desquamation.
In conducting an analysis of native ex vivo porcine tissue we were successfully able to detect and spatially map chemical biomarkers of both the stratum corneum and underlying epidermis. In addition, using gas cluster ion beam (GCIB) depth profiling, the 3D distribution of analytes throughout the epidermis could be visualised for both pharmaceutical and cosmetic topical products following Franz cell experiments. A comparison of permeation was achieved for ascorbic acid (vitamin C) as delivered using a PBS solution (Fig. 1b) and encapsulated within a supramolecular gel (Fig. 1c). An enhanced permeation depth is observed using the supramolecular gel delivery into the underlying epidermis and in PBS the ascorbic acid is not observed beyond the stratum corneum. The depth of permeation can be determined using sputter rates derived from optical profilometry (Fig. 1a) of the resulting craters and / or using native tissue markers observed within different layers of the skin.