Hichem KICHOU holds a PhD in analytical chemistry from the University of Tours, France. His doctoral research focused on developing comprehensive multi-method analytical approaches to study the interaction and diffusion of active ingredients, both cosmetic and pharmaceutical, within human skin. His work involved using advanced chromatography techniques to investigate the penetration kinetics of molecules across different skin layers. Additionally, he used Raman spectroscopy combined with multivariate analysis to explore skin penetration profiles. This innovative methodology provided significant insights into the behaviour of active ingredients in dermatological applications, advancing scientific knowledge and practical applications in skin research. 

Exploring Reconstructed Human Skin and Synthetic Membranes as Alternatives to In Vitro Permeation Testing.

In the development and optimisation of dermatological products, in vitro permeation tests (IVPT) are essential for studying skin penetration. To improve standardisation and replicate the properties of human skin, several models are explored as alternatives. Among these models, Strat-M® and RHE models stand out. Strat-M®, a polymer model, does not replicate the formulation effect observed on human skin. However, it shows permeability closer to human skin compared to RHE. RHE, while reproducing the formulation effect and demonstrating qualitative molecular similarity to human skin through Mass Spectrometry and Raman Spectroscopy (RS), shows higher permeability values than human skin. This makes it a good alternative for screening formulations, highlighting its importance as a reliable substitute. However, a major challenge with RHE is its limited shelf life. To address this, the chemical fixation of RHE in formalin for 24 hours has been examined for storing samples for up to 21 days. RS analysis revealed that while fixation alters the biochemical architecture, particularly proteins and lipids, it does not significantly affect the cumulative amount and permeability in IVPT using caffeine as a model compound. This preservation method offers increased flexibility and utility in skin model research, opening up prospects for mitigating the storage limitations of RHE models while maintaining their performance as effective barriers for rate-limiting diffusion of active molecules.