Scanning Electrochemical Microscopy of Iontophoretic Transport in Hairless Mouse Skin: Analysis of the Relative Contributions of Diffusion, Migration, and Electroosmosis to Transport in Hair Follicles

The study used scanning electrochemical microscopy (SECM) to investigate the transport mechanisms in hairless mouse skin, particularly focusing on hair follicles. By applying an electric current, the researchers examined the transport of an anion, a cation, and a neutral molecule to understand the contributions of diffusion, migration, and electroosmosis. They discovered that hair follicles possess a net negative charge at neutral pH, which facilitated electroosmotic transport, increasing the rate of neutral molecule transport by 2.4 times at 0.1 mA/cm². Migration notably enhanced the flux of charged species. The electroosmotic flow velocity was measured at 0.5 μm/s at 0.1 mA/cm², with a net volume flow rate of 0.3 μL/cm²h. The study concluded that hair follicles are a crucial pathway for electroosmotic flow during iontophoresis, with follicle openings averaging 21 ± 5 μm in radius.