Dendritic growth of protein gel in the course of sweat pore plugging by aluminium salts under physiological conditions
Résumé
Are aluminium ions unavoidable in antiperspirants? In spite of strong consumer demand for alternatives to aluminium salts in cosmetics, these salts remain, to date, the only active substance in the market for antiperspirants. Such exclusivity is the direct result of the lack of understanding of how ions interact with sweat proteins. Here, we unveil the mechanism of antiperspirant action of aluminium salts, based on our observations through confocal microscopy and our numerical simulations of protein and ion motions in the sweat pore. We find that aluminium polycations move through Brownian diffusion in the vicinity of the walls of a sweat pore. They react with sweat proteins, and form a sparse dendritic protein gel in the pore through a diffusion-limited aggregation process. When the dendrites percolate, the gel suddenly densifies, thereby plugging the pore. Altogether, these results allow the understanding of why aluminium polycations are so efficient and why they are so difficult to replace.
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