Permeability of thermally damaged skin IV: influence of branding iron temperature on the mass transfer of water and n-alkanols across hairless mouse skin

Our previous studies were extended to determine the effects of temperature of ‘dry burns’ on the skin's permeability. Using a branding iron device, burns have been administered to the dorsal surfaces of freshly sacrificed hairless mice at 60°, 70°, 80°, 90°, 100°, 110°, 120°, 140°, 150°, 200°, and 250°C, all for 60-second durations. Permeability coefficients of control (abdominal) and burn-damaged (dorsal) skins were determined by using a two-chamber diffusion cell. Water, methanol, ethanol, n -butanol, n -hexanol, and n -octanol were used as test permeants. Up to 70°C, the 60-second burns do not markedly alter skin permeability. At higher temperatures, marginal to extreme increases are found depending on the lipophilicity of the permeant. Permeability increased dramatically for the polar solutes, water, methanol, and ethanol, moderately for butanol, and only slightly for hexanol. Octanol's permeability was little affected by temperature. In terms of chemical barrier properties, the maximum effect of burning is on the stratum corneum, which controls the polar permeants' transport. Dermal barrier properties appear appreciably unchanged based on the limited sensitivity of the permeation rates of lipophilic solutes. The alkyl chain length sensitivity of permeation was observed to diminish linearly with increasing temperature of branding, reaching a value of zero at ∼120°C. This indicates a complete loss of the partitioning dependency of the permeation process and therefore functional alteration of the stratum corneum.