Exploring supramolecular gels as innovative materials for cosmetic applications

The environmental impact of synthetic polymers in cosmetic products, particularly microplastics, has raised growing concern due to their persistence and limited biodegradability. This thesis focuses on the development and characterisation of supramolecular gels based on Low Molecular Weight Gelators (LMWGs) as potential non-polymeric rheological modifiers for cosmetic systems, with potential applications beyond this sector. LMWGs are small organic molecules (typically <1 kDa) capable of self-assembling into fibrous networks through non-covalent interactions, immobilising large amounts of solvent and forming soft materials known as supramolecular gels. Two structurally different LMWGs, Boc-L-DOPA(Bn)₂-OH and Pal-L-Phe-OH, were synthesised and tested in detergent systems in combination with various anionic or amphoteric commercial surfactants. A parallel investigation explored already authorised cosmetic ingredients capable of gelation, leading to a successful formulation based on Sodium Cocoyl Glycinate, which exhibited particle suspension, stability under accelerated storage conditions, and feasibility for industrial manufacturing. The same LMWGs, Boc-L-DOPA(Bn)₂-OH and Pal-L-Phe-OH, along with their methyl esters, were studied in model cosmetic emulsions. The study focused on assessing the best way to incorporate these LMWGs into emulsions and exploring strategies, such as combination with biopolymers, to enhance formulation stability and achieve rheological properties suitable for cosmetic applications. Finally, during a research period at the University of Glasgow, the artificial intelligence AlphaFold 2 (AF2) was explored as a tool for predicting the folding of octapeptides and guiding the rational design of peptide-based supramolecular gelators. Selected sequences predicted to form β-sheets were synthesised and characterised using Circular Dichroism, SAXS, and rheology. Overall, this thesis work aims to demonstrate the potential of LMWGs based on peptides as sustainable alternatives to synthetic polymers in cosmetics, highlighting both the challenges and the opportunities for developing innovative formulations.