SUBZERO THERMAL-ANALYSIS OF HUMAN STRATUM-CORNEUM

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