Subzero Thermal Analysis of Human Stratum Corneum

Abstract

The thermal behaviour of human stratum corneum was studied using differential thermal analysis within the temperature range of −130°C to 120°C. Aside from thermal transitions at around 40°C, 70°C, 85°C and 100°C, which have been reported before, a particular transition below 0°C (subzero), at approx. −9°C (264 K), was noticed. This transition was present in the analysis curves of dehydrated as well as hydrated stratum corneum sheets and could be distinguished from the water peak found only in hydrated stratum corneum samples. To further characterize this transition, thermal analysis was performed on stratum corneum sheets: (i) after lipid extraction, (ii) after pre-treatment of propylene glycol and (iii) after pretreatment of oleic acid/propylene glycol solution. From the results, it was concluded that the subzero transition (−9°C) belongs to low melting lipid components of stratum corneum.