Microscopic FT-IR/DSC combined system used to investigate the thermotropic behavior of lipid in porcine stratum corneum after pretreatment with skin penetration enhancers.

BACKGROUND

The stratum corneum (SC) is the outermost barrier of the skin to prevent environmental attack and water loss. The function of SC has been found to be related to the lipid phase transitions in SC. In this study, we used a newly developed microscopic Fourier transform infrared spectrometer equipped with a thermal analyzer (FT-IR/DSC) system to simultaneously investigate the correlation between the thermotropic response and the structural changes of lipids in porcine SC after pretreatment with skin penetration enhancers.

METHODS

The CH2 stretching vibrational bands near 2850 and 2920 cm(-1) of lipid in porcine SC pretreated with skin penetration enhancers were studied by this microscopic FT-IR/DSC system.

RESULTS

The results indicate that the temperature-induced change in the peak position for both asymmetric and symmetric CH2 stretching bands was found to be shifted to higher wavenumber position with increased temperature and this alteration was reversible after cooling the heated SC sample, which was independent of the skin penetration enhancers pretreated except the SC sample pretreated with azone/propylene glycol.

CONCLUSION

The porcine SC pretreated with azone/propylene glycol exhibited a marked change in the phase-transition temperatures of lipid during 1 st and 2nd heating processes, suggesting the synergistic effect of both azone and temperature on the lipid thermotropic behavior of porcine SC.