Azone® induced fluidity in human stratum corneum. A fourier transform infrared spectroscopy investigation using the perdeuterated analogue

Abstract

The effect of Azone® on human stratum corneum (SC) lipid fluidity was investigated by the use of FT-IR spectroscopy and its perdeuterated analogue (D-azone). SC lipid fluidity was monitored in terms of the degree of organisation of the lipid acyl chains (reflected by changes in the frequency of the C-H 2 symmetric stretching frequency) and in terms of the rate of motion of the lipid chains within the ordered environment (reflected in changes in the bandwidth of the C-H 2 symmetric stretching frequency at half maximum height). Two levels of D-azone treatment were used. At the lower level results indicated that D-azone did induce disordering of the lipid acyl chains by the introduction of gauche conformers above the SC lipid gel to liquid crystalline phase transition midpoint (T m). The rate of motion of the chains was increased at lower temperatures indicating that D-azone did affect one aspect of SC lipid fluidity below T m. At the higher level of D-azone treatment the SC lipid fluidity was increased with respect to both aspects of fluidity examined, both above and below the SC lipid phase transition. This action could suggest how the penetration of molecules through the skin is enhanced by Azone. The data also seem to suggest a homogeneous distribution of D-azone through the SC lipid array.