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Skin as good as the real thing?
BILLERICA, Mass.—A synthetic skin membrane produced by EMD Millipore is just as effective for some research purposes as the real thing, a new study has found. The product, Strat-M, was found to predict skin permeation of chemical compounds during in-vitro transdermal diffusion studies as effectively as human or animal skin. The study found that Strat-M could be effectively used as a model to predict diffusion for a diverse range of molecules.
“Strat-M membrane offers a wide utility as a model for compound screening and formulation studies,” Vivek Joshi, principal research scientist at EMD Millipore, a life-sciences subsidiary of Merck KGaA, tells DDNews.
The pharmaceutical and personal care industries rely on various kinds of skin models to test the adsorption and diffusion of active ingredients during development of transdermal drugs and personal care products, including active pharmaceutical ingredients, cosmetic actives and pesticides. This testing is frequently conducted using human cadaver skin or animal skin models from rats, mice or pigs. There are significant drawbacks to these biological models, however. The diffusion rate through human cadaver skin is dependent on the site from which the skin is removed and is also affected by the age, race and gender of the donor. Moreover, biological models have special storage requirements, are often difficult to procure and require special methods of disposal.
“All these biological models are inherently plagued with high variability,” says Joshi. “They are also more expensive and difficult to obtain in larger amounts and have limited shelf life.”
The Strat-M membrane, which was first released in 2012, was designed to overcome these challenges associated with biological diffusion models while also providing data that is very similar to diffusion through human skin in in-vitro studies. The Strat-M membrane is now used by many pharmaceutical and personal care industry companies during various phases of product development—employed for the screening of active compounds, formulation screening, formulation rank ordering and other purposes. Strat-M is constructed of multiple layers, creating morphology similar to human skin. The product comes individually packaged as precut discs that are easy to store and do not need to be hydrated prior to use.
The study, which was conducted by researchers at Josai University in Japan, was published earlier this year in the European Journal of Pharmaceutical Sciences. The researchers’ aim was to evaluate the usefulness of Strat-M membrane as a diffusion model relative to human and animal skin. Thirteen different compounds with Log P -0.9 to 3.5 and molecular weight range of 152 to 289 were tested for their diffusion behavior through Strat-M membrane as well as through human and rat skin.
“The most significant finding of the study was that the Strat-M membrane could be used as a model to predict diffusion behavior of compounds with a molecular weight range of 151 to 288 and log K o/w (Octanol / water partition coefficient ) values between 0.9 to 3.53,” Joshi tells DDNews. “This range of molecular weights and Log K o/w covers a wide range of compounds that are used in transdermal formulations.”
The study found that permeability coefficients obtained with Strat-M could be used to predict those obtained from the human and rat skins.
“Our study suggests that Strat-M membrane can serve as an alternative to human and animal skin in permeation studies, offering researchers a valuable tool for screening candidate compounds,” said study co- author Dr. Hiroaki Todo.
Patrick Schneider, head of bioscience at EMD Millipore, noted that the study confirmed that Strat-M is an effective tool for transdermal diffusion testing. “Published results supporting the membrane’s application will increase awareness and accelerate adoption by the research community, facilitating in-vitro testing of transdermal formulations,” he said.
Kenji Sugibayashi, author of the study and professor of pharmaceutical sciences at Josai University, says that finding more effective methods of testing skin permeation is very important. “In-vitro skin permeation studies are essential to development of new transdermal delivery systems,” he said. “Biological models are often used to conduct this research, but there are various drawbacks, including high variability, low availability, safety considerations and storage limitations.”