American Journal of Agricultural and Biological Sciences 3 (2): 444-450, 2008 ISSN 1557-4989 © 2008 Science Publications Corresponding Author: Aroonsri Priprem, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand Tel: +66-43-362092 Fax: +66-43-362092 444 Comparative Permeation Studies between Scale Region of Shed Snake Skin and Human Skin In vitro Aroonsri Priprem, Chidchanok Khamlert, Thaned Pongjanyakul, Sarayut Radapong, Theera Rittirod and Padungkwan Chitropas Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand Abstract: Scales of shed king cobra (Ophiophagus hannah) skin from the dorsal portions, (SSS) and human breast epidermis (HE) were used as barrier membranes for comparison in an in vitro drug permeation study of nine active compounds (MW range 150-300 g mol -1 , pK a 3-10). Each compound, saturated in a donor solution at pH 4.0 or 5.6, permeated through the barrier membrane, fully hydrated. A receptor solution at pH 7.4 was sampled for quantification at its λ max by UV-Visible spectrophotometry and/or HPLC. The permeability coefficients of nine compounds were correlated to the n-octanol/water partition coefficients of these compounds. The permeability coefficient of these compounds using HE and SSS was correlated. Scales of shed skin from the dorsal portions of king cobras were shown to be well correlated to the human breast epidermis in this in vitro aqueous permeation study of these compounds. Key words: Scale region, shed king cobra skin, human skin, permeation, barrier membrane INTRODUCTION Permeation of drugs through the skin barrier has been the basis of transdermal delivery [1] . The human skin is an effective and selective barrier to chemical permeation [2] ; however, it is not always possible to do actual skin permeation studies in humans. In vitro permeation studies and model barrier membranes using excised skins (human cadaver and animals) or artificial materials have been employed. Animal skins generally gave higher permeation profiles than the human skin because of the differences in thickness, stratum corneum, density of hair follicles, sweat glands and appendages [3] . The idea of using shed snake skin as the barrier membrane in in vitro permeation studies was introduced by Higuchi and Kans [4] . It is a non-living tissue which can be obtained without sacrifices, lacks hair follicles, and gives less variation than human or animal skin. Shed skins of several snakes, such as Elaphe obsoleta [3,5,6,7,8] , Python reticulatus [9] and Ophiophagus hannah [10] , have been investigated. Haigh et al. [7] emphasized the effect of species, sites and regions of the shed snake skin used. Good correlation of results to human skin suggested the use of shed snake skin as a model membrane for permeation studies despite the differences in anatomical and chemical compositions [5,11,12] . Haigh et al. [7] suggested that the differences in lipid contents, a vital component of the skin, between shed snake and human skin could affect the permeability of compounds. Shed snake skin usually consists of three distinctive layers; beta, mesos and alpha-layers [3] . Major lipid compositions of shed snake skins are phospholipids while that of the human skin are ceramides [13] . Shed snake skin is composed of two very different regions; scales and separating these, hinges. The scales are rigid while the hinge is elastic. The scales on the dorsal part are much smaller and usually thinner than the scales on the ventral part. Most of the studies related to the use of shed snake skins employed whole skin which included the scales and hinges, except that of Harada et al. [9] which used only the scales of Python reticulatus for in vitro permeability of salicylic acid. Factors affecting the permeation of different compounds include ionization [14] , partition, and molecular weight [14] . Takahashi et al. [6] used six basic compounds with low pK a (0.6-5.3) and found that non-ionized forms permeated at a greater rate (0.01-33.3×10 -3 cm h -1 ). Potts and Guy [15] selected more than 90 compounds from various reports with molecular weights ranging from 18 to 750 and n-octanol/water partition coefficients (log K o/w ) ranging from 3 to 6 to predict skin permeability using multiple linear regressions.