Enhanced vitamin C skin permeation from supramolecular hydrogels, illustrated using in situ ToF-SIMS 3D chemical profiling

Vitamin C (ascorbic acid) is a naturally occurring, powerful anti-oxidant with the potential to deliver numerous

benefits to the skin when applied topically. However, topical use of this compound is currently restricted by an

instability in traditional formulations and the delivery and eventual fate of precursor compounds has been

largely unexplored. Time of flight secondary ion mass spectrometry (ToF-SIMS) is an emerging technique in the

field of skin research and offers detailed chemical analysis, with high mass and spatial resolution, as well as

profiling capabilities that allow analysis as a function of sample depth. This work demonstrates the successful use

of ToF-SIMS to obtain, in situ, accurate 3D permeation profiles of both ascorbic acid and a popular precursor,

ascorbyl glucoside, from ex vivo porcine skin. The significant permeation enhancing effect of a supramolecular

hydrogel formulation, produced from an amphiphilic gemini imidazolium-based surfactant, was also demonstrated

for both compounds. Using ToF-SIMS, it was also possible to detect and track the breakdown of ascorbyl

glucoside into ascorbic acid, elucidating the ability of the hydrogel formulation to preserve this important

conversion until the targeted epidermal layer has been reached. This work demonstrates the potential of ToFSIMS

to provide 3D permeation profiles collected in situ from ex vivo tissue samples, offering detailed analysis on

compound localisation and degradation. This type of analysis has s