DIOXYGEN DIFFUSION IN THE STRATUM-CORNEUM - AN EPR SPIN-LABEL STUDY

The stratum corneum, the outer 10 mum of the skin, serves as a permeab ility barrier regulating the transport of molecules between the body a nd the environment. The purpose of this study is to understand this pe rmeability barrier function as it pertains to the diffusion of molecul ar oxygen. The stratum corneum was investigated with EPR spectroscopy following inoculation with a stearic acid spin probe. The presence of paramagnetic molecular oxygen results in the broadening of the EPR spe ctral lines of the spin probe. The rate of oxygen diffusion across the stratum corneum, and then the oxygen diffusion coefficient, D(O2), wa s determined by studying this line-broadening as a function of time. D (O2) in human stratum corneum was found to be 3 . 10(-7) cm2/s at 37-d egrees-C with an activation energy of approx. 44 kJ/mol. The applicati on of the permeation-enhancing chemicals, DeMSO and DMSO, to the strat um corneum increased D(O2) two- to three-fold.