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Characterization of porcine skin as a model for human skin studies using infrared spectroscopic imaging Rong Kong and Rohit Bhargava*
Downloaded by Queen Mary, University of London on 19/04/2013 18:44:34. Published on 21 April 2011 on http://pubs.rsc.org | doi:10.1039/C1AN15111H
Received 10th February 2011, Accepted 14th March 2011 DOI: 10.1039/c1an15111h Porcine skin is often considered a substitute for human skin based on morphological and functional data, for example, for transdermal drug diffusion studies. A chemical, structural and temporal characterization of porcine skin in comparison to human skin is not available but will likely improve our understanding of this porcine skin model. Here, we employ Fourier transform infrared (FT-IR) spectroscopic imaging to holistically measure chemical species as well as spatial structure as a function of time to characterize porcine skin as a model for human skin. Porcine skin was found to resemble human skin spectroscopically and differences are elucidated. Cryo-prepared fresh porcine skin samples for spectroscopic imaging were found to be stable over time and small variations are observed. Hence, we extended characterization to the use of this model for dynamic processes. In particular, the capacity and stability of this model in transdermal diffusion is examined. The results indicate that porcine skin is likely to be an attractive tool for studying diffusion dynamics of materials in human skin.
Skin is a naturally efﬁcient barrier that protects the body from physical and chemical hazards, and the loss of water.1–3 Maintenance of the disease-free function of this vital organ is directly relevant to patients’ health and their social interactions. In particular, skin cancer is the most common form of cancer in the United States4 and the understanding of this tissue is of great importance to prevent and treat this disease. Skin is also an important pathway for drug delivery and for the application of cosmetics. Transdermal drug delivery has many advantages, such as its easy handling, safety, ability of controlled release and bypassing the gastrointestinal tract.5–8 The combined needs in these areas have led to the development and use of several model systems as a surrogate for human skin, including from other animals and engineered skin.9–11 Based on morphological and functional data, domestic pig skin seems to be the closest to human skin,12–14 and is often used as a substitute in various human skin studies.14,15 Processes like transdermal drug diffusion are mechanistically related to the chemical structure and composition of skin.16–19 Hence, the similarity of porcine skin in mimicking human skin largely depends on the structural and chemical similarity to some extent. Both these properties of skin and their evolution over time should also be examined as accurate histologic reproduction and minimal chemical degradation are critical aspects of any skin model. Finally, skin is structurally
Department of Bioengineering, Micro and Nanotechnology Laboratory and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA. E-mail: rxb@ illinois.edu
hetergeneous.1 Hence, variations among different samples and of the same histological entities within a sample must be accounted for to either understand or address reproducibility issues in using model systems. While histologic characterization of tissue is routinely accomplished by structural imaging, a biochemical characterization typically requires destruction of the structure. Destructive methods result in a loss of spatially speciﬁc information, which is vital to many skin studies, including the diffusion of molecules in skin. Yet, there are few techniques available...