Transdermal electroosmosis

The development of the first transdermal patches in the 1980s generated considerable interest in this route of drug administration. Soon afterwards, iontophoresis was rediscovered and its potential to contribute to the new field of transdermal drug delivery was examined. This work provided the basic principles for modern iontophoretic devices [13,18-21]. Furthermore, and importantly, they demonstrated the existence of a (primarily) electroosmotic, convective solvent flux during transdermal iontophoresis [10,11,22-24], and it was shown that the permselective properties of the skin (a) could be exploited to enhance the transport of neutral, polar species and (b) have a clear impact on ionic transport. Subsequent research has better characterized skin permselectivity and the factors which determine the magnitude of electroosmosis [25-27],... 

Sieg, A., R.H. Guy, and M.B. Delgado-Charro. 2004. Electroosmosis in transdermal iontophoresis Implications for non-invasive and calibration-free glucose monitoring. Biophys J 87 3344. 

Iontophoresis by definition is the process of transport of ions into or through a tissue by the use of an applied potential difference across the tissue [52], Depending on the physicochemical characteristics of a molecular species, electrorepulsion is usually the primary mechanism of transdermal transport for ions, whereas electroosmosis and increased passive diffusion (as a result of the reduced barrier properties) are more prominent for neutral species [53]. In contrast, enhancement in flux for neutral or weakly charged species during electroporation arises predominantly from the reduced barrier properties of the membrane, whereas direct electrorepulsion is usually of secondary importance [25],... 

SECM has been recently used by Bath et al. in the investigation of elec-troosmotic convective flow (10). Electroosmosis occurs in porous membranes employed in fuel cells, representing an important practical issue in the parasitic crossover of fuel (e.g., methanol) and in the flooding/drying of the fuel cell electrodes (29,30). Electroosmotic flow across skin, a naturally occurring ion-selective membrane, is also of interest in transdermal drug delivery, as discussed in Sec. III.B.2. 

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