RESUMEN
BACKGROUND: Barium sulphate, a stable inorganic material, has been used in contrast media and cosmetic products because of its stability. As a negative external electric potential accelerates the skin barrier repair after barrier disruption, we hypothesized that topical application of barium sulphate may affect the skin barrier recovery rate depending on its zeta potential. OBJECTIVES: To investigate whether barium sulphate particles in aqueous solution have different zeta potentials depending on their surface structure, and to investigate the possible relation between zeta potential and skin barrier recovery rate. METHODS: Mice were subjected to tape stripping to disrupt barrier function, or were treated with acetone and kept in a dry environment to induce epidermal hyperplasia. They were then treated with different forms of barium sulphate, and barrier recovery was monitored by measurements of transepidermal water loss. RESULTS: There was a significant correlation between the barrier recovery rate and zeta potential of barium sulphate applied topically. Barium sulphate with a negative zeta potential significantly accelerated barrier recovery, but barium sulphate with a positive zeta potential did not accelerate or even delayed barrier repair. Barium sulphate with a negative zeta potential had an X-ray diffraction pattern different from that with a positive potential. The distribution of calcium in the epidermis was also influenced by the polarity of zeta potential. CONCLUSIONS: These findings suggest a new pharmacological approach towards altering barrier function or epidermal hyperplasia with inorganic particles in healthy and diseased skin.