Dioxygen diffusion in the stratum corneum: an EPR spin label study

The stratum corneum, the outer 10 microns of the skin, serves as a permeability barrier regulating the transport of molecules between the body and the environment. The purpose of this study is to understand this permeability barrier function as it pertains to the diffusion of molecular 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 spectral lines of the spin probe. The rate of oxygen diffusion across the stratum corneum, and then the oxygen diffusion coefficient, D(O2), was determined by studying this line-broadening as a function of time. D(O2) in human stratum corneum was found to be 3 x 10(-7) cm2/s at 37 degrees C with an activation energy of approx. 44 kJ/mol. The application of the permeation-enhancing chemicals, DeMSO and DMSO, to the stratum corneum increased D(O2) two- to three-fold.