Epidermal membranes

R. C. Scott, M. Walker, and P. H. Dugard. In vitro percutaneous absorption experiments A technique for the production of intact epidermal membranes from rat skin. J. Soc. Cosmet. Chem. Jpn. 37 35-41 (1986). 

Li, S.K, A.-H. Ghanem, K.D. Peck, and W.I. Higuchi. 1997. Characterization of the transport pathways induced during low to moderate voltage iontophoresis in human epidermal membrane. J Pharm Sci 87 40. 

Peck, K.D., et al. 1996. Quantitative description of the effect of molecular size upon electroosmotic flux enhancement during iontophoresis for a synthetic membrane and human epidermal membrane. J Pharm Sci 85 (7) 781. 

FIGURE 15.1 Instantaneous flux of estradiol through human epidermal membrane. Membranes were electroporated by either 5 x 100 V pulses with a pulse width of 100 ms (closed symbols) or 50 x 100 V pulses with a pulse width of 10 ms (open symbols) (n — 3). 

FIGURE 15.3 Instantaneous flux profiles of estradiol through human epidermal membrane during a three stage experiment. Electrical procedures were iontophoresis (0.8 mA/cm2), electroporation (5 x 100 Y pulses with a pulse width of 100 ms), or electroporation followed by iontophoresis (n = 5-9). 

Higuchi, W.I., et al. 1999. Mechanistic aspects of iontophoresis in human epidermal membrane. J Control Release 62 13. 

Inada, H., W.I. Higuchi, and A. Ghanem. 1994. Studies on the effects of applied voltage and duration on human epidermal membrane alteration/recovery and the resultant effects upon iontophoresis. Pharm Res 11 687. 

If skin is placed in a water bath under controlled conditions [14] the primary barrier to transdermal delivery, the epidermal membrane comprising the stratum corneum and viable epidermis, can be readily removed and used to analyze the penetration and diffusion of materials. Figure 18.3a and Figure 18.3b show the appearance of human breast epidermal membrane, with epidermis facing uppermost, following application of the cylindrical dry-etch and pyramidal wet-etch silicon microneedles, respectively. In each case the microneedles are clearly shown to pierce the stratum corneum and viable epidermis to facilitate controlled access of molecules to the target region of skin. 

FIGURE 18.3 Scanning electron micrographs of epidermal membrane treated with dry-etch and wet-etch silicon microneedles. The epidermal membrane, consisting of stratum corneum and viable epidermis, was obtained by heat separation of full-thickness human breast skin. The tissue was immersed in distilled water preheated to 60°C for 60 s and the upper layers carefully peeled off from the dermal layer using tweezers. Epidermal membranes were treated with microneedles for 30 s at an approximate pressure of 2 kg/cm2. (a) Dry-etch microneedle-treated epidermal membrane. Bar = 200 pm (b) wet-etch microneedle-treated epidermal membrane. Bar = 500 pm. 

Robbins, C. and Fernee, K., Some observations on the swelling of human epidermal membrane. J. Soc. Cosmet. Chem. 34 21-34, 1983. 

Human skin membranes are usually prepared from abdominal or breast skin, while for animal skin membranes the commonly used sites are the flank and back (rat) or the flank and ear (pig). Three types of membranes can be prepared epidermal membranes (thickness of approximately 0.1mm, prepared by... 

To illnstrate the differences between skin membrane types, Fignre 9.1 shows a series of independent experiments with the lipophilic reference compound testosterone performed in onr laboratory. The data demonstrate that epidermal membranes were approximately 3.5 times more permeable than fnll-thickness skin, based on the percentage of the applied compound reaching the receptor fluid during 24 h. Each experiment was performed with skin from a different donor, and the variation between the in vitro experiments was within the same range as reported for hnman volunteers in vivo (Schaefer and Redelmeier, 1996). 

Figure 9.1 In vitro absorption of testosterone through (a) human full-thickness skin membranes of approximately LOO mm thickness or (b) human epidermal membranes after 24 h exposure. Testosterone was applied at a dose of 15p,g/cm and each independent experiment was performed with four to six membranes obtained from the abdominal skin of one donor...

The decontamination efficiency of Fuller s earth, Amber-gard, and BDH spillage granules was tested by measuring the skin absorption rates and the percentage of applied dose of SM that penetrated human and pig ear epidermal membranes in vitro. Fuller s earth was found to be better than the other two. This was in agreement with an in vivo... 

Investigation of intact SC samples by transmission IR was first undertaken in the 1970s by Park and Baddiel [31] and has since become a routine procedure. The thin (10-20 pm) cross section of the SC allows an intact sheet of SC (following isolation from epidermal membranes) to be analyzed directly by transmission IR. The resulting spectmm is typified by absorbances origi-... 

Peck, K. D Ghanem, A. H., Higuchi, W. I. and Srinivasan, V. (1993). Improved stability of the human epidermal membrane during successive permeability experiments. Int. J. Pharm. 95 141-147. 

Peck, K. D., Ghanem, A. H. and Higuchi, W. 1. (1994). Hindered diffusion of polar molecules through and effective pore radii estimates of intact and ethanol treated human epidermal membrane. Pharm. Res. 77 1306-1314,... 

Smyth HD, Becket G, and Metha S. Effect of permeation enhancer pretreatment on the iontophoresis of luteinizing hormone releasing hormone (LHRH) through human epidermal membrane (HEM). J. Pharm. Sci. 2002 91 1296-1307. 

Li, S.K. Higuchi, W.I. Kochambilli, R.P. Zhu, H. Mechanistic studies of flux variability of neutral and ionic permeants during constant current DC iontophoresis with human epidermal membrane. Int. J. Pharm. 2004, 273, 9-22. 

Insert magnetic flea in receptor chamber and mount epidermal membranes stratum corneum side up in horizontal Franz-type diffusion cells, that are then placed on a magnetic stirrer plate in a water bath (Fig. 1) (see Note 8). 

An in vitro study indicated that 2-butoxyethanol is absorbed through human abdominal epidermis (Dugard et al. 1984). Undiluted 2-butoxyethanol was applied to human abdominal epidermal membranes for a period of 8 hours. The absorption rate was 0.2 mg/cm%our. In another in vitro study, a 10% solution of 2-butoxyethanol was applied to a 3-cm area on frozen human arm skin, which was obtained at autopsy, under semiocclusive or nonocclusive conditions (Bartnik et al. 1987). The percentage of absorption was 6.9% for the nonocclusive condition and 17.3% for the semiocclusive condition. 

Epidermal membranes, comprising the viable epidermis and the stratum corneum (prepared by heat separation)... 

Stratum corneum alone (prepared from epidermal membranes by enzyme treatment)... 

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