Skin interface

Safety is an important factor when determining the quality of any iontophoresis electrode. During transdermal iontophoretic delivery using metal electrodes, an applied DC current will induce pH changes on the electrode/skin interface [178], pH measurement is used to eliminate the possibility of unsafe pH changes (chemical bums). It has been reported that the pH shift caused by platinum electrodes has a significant influence on the permeation and stability of insulin [175],... 

In contrast, vehicle that are immiscible with water and those with a high proportion of oils have occlusive effects. They reduce both insensible perspiration and the release of sweat. The sweat collects as droplets at the opening of the glands, but does not spread as a film between the hydrophobic skin surface and the hpophific base because the free surface energy of the vehicle-skin interface is smaller than that between water and skin. If a lipophilic layer of vehicle is present, this is not spontaneously replaced by the water-skin layer if sweat is secreted. 

For the experiment, the dorsal skin of young rats (Wistar or a comparable strain) is shaved and washed with an antibiotic solution (containing, e.g., streptomycin, penicillin, chloramphenicol, and amphotericin in concentrations inhibiting bacterial growth). After skin excision, excess fat is peeled off and the skin is placed over the end of a polytetrafluoroethylene tube with the epidermal side in touch with the hollow cylinder. The skin is fixed with an O-ring and the tube interior is sealed. The side of the dermis is then submersed in a magnesium sulphate solution (154 mM). The samples are applied at 30°C to the epidermal side of the skin in such a way that the skin interface is fully covered. After the incubation time, the substances are removed with prewarmed water the skin surface tension is decreased with ethanol which is subsequently replaced with magnesium sulphate solution (154 mM). 

Elias, PM. and Feingold, K.R. A dynamic view of the stratum corneum applications to skin. In Skin Interface of a Living System. Tagami, H., Parrish, J.A., and Ozawa, T. Eds. Elsevier, New York, 1998, p. 141-150. 

Figure 8 A schematic representation of attenuated total reflectance. An incident beam propagating through an IR transparent crystal of refractive index, nj strikes the skin interface of lower refractive index, n2 at the angle 0 which is greater than the critical angle (0c = sin [na/ni]). As a result, the beam is totally internally reflected and an evanescent beam established at the interface propagates into the skin. The amplitude (A) of the wave decays exponentially with increasing distance (D) from the interface. A = (intensity at distance, D)/(intensity at interface).

Using 4-cyanophenol (CP) as a model compound, ATR-IR has been applied following an approach pubhshed by Pirot et al. (1997). The SC distribution profile of the chemical following its relatively short-term contact, via contaminated soil, with the skin has been detomined and used to obtain diffusion and partitioning parameters. In addition, the results have permitted the hypothesis that a significant mass transfer resistance exists across the soil—skin interface, reducing thereby the rate and extent of chemical absorption following short-term contact. 

Cooper, G., Barker, A.T., Heller, B.W., Good, T., Kenney, L.P.J., Howard, D., 2011. The use of hydrogel as an electrode-skin interface for electrode array FES appHcations. Medical... 

Once a surfactant is applied to skin, it will tend to concentrate at the solution-skin interface and, more particularly, its hydrophobic domain will tend to intercalate within the lipid bilayers of the well-organized lamellar liquid crystal of the stratum comeum. Such an... 

In a recent theoretical study [83] was shown that by refractive index matching at the skin interface and a fibre-optical fluorescence probe one can improve the contrast and spatial resolution of the shallow sampling volume. 

Li and Holcombe [21] reported a new model by interfacing the model for a naked body with a heat and moisture transfer model of a fabric. They developed the boundary condition between the body and clothing by quantifying the heat and mass flow. At the fabric-skin interface. 

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