Passive diffusion microscopy

The in situ precipitation technique and transmission electron microscopy have been used to investigate the effect of DMSO on percutaneous absorption in the mouse barrier [27] and human SC [46]. Sharata and Burnette examined ultrastructural changes in mouse stratum comeum by determining the distribution of sulfide precipitates of topically applied, water-soluble tracers (Hg and Ni ) after application of enhancer [27]. For skin pretreated with DMSO, mercury and nickel precipitates were found within swollen basal stratum comeum cells as well as intercellularly and associated with the cell envelopes, but not below the stratum comeum-stratum granulosum interface. It was concluded that treatment with DMSO, as well as with other dipolar aprotic solvents such as DMF and DMA, alters the passive intercellular diffusion pathway by expanding the size of the basal stratum comeum cells, resulting in an increased free volume for tracer diffusion. 

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