Enhancement of Hair Fiber Strength and Surface Morphology by <em>Saccharomyces </em>Lysate Assessed Using Tensile Testing and μ-CT

Consumer demand for sustainable solutions to protect against hair damage is growing, yet quantitative studies linking molecular interactions to mechanical strengthening and structural changes remain limited. Here, we investigated the effectiveness of biotechnologically obtained Saccharomyces Lysate as an active ingredient for hair care. Molecular modeling was used to explore the interactions between peptides in the lysate with keratin and suggested a network of intermolecular interactions at multiple sites of the proteins. Based on these observations, the strength and structural integrity of hair fibers treated with Saccharomyces Lysate were assessed using tensile measurements. We observed an improvement in the strength of hair tresses, with an increased Young’s Modulus compared to hair tresses treated only with water along with a significantly increased break stress. To visualize the hair fibers and their surface roughness after treatment with the lysate, we employed micro-computed tomography (µ-CT) offering high-resolution visualization of hair fibers. We introduce this method to qualitatively highlight the surface appearance following the application of a cosmetic product and complemented it with combing-force measurements. Our results demonstrate the potential of this complex mixture of small peptides to strengthen hair integrity and we propose a hypothesis for its mode of action on the molecular level.