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Water Content, Nanoparticles and Skin Penetration in Brazil: Lindo Maravilhoso!
By: Rachel Grabenhofer, Cosmetics & Toiletries
Posted: May 29, 2013
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From the research side, Jeffrey Grice, of the University of Queensland, Australia, explored the targeting of topical products and the levels to which they penetrate the skin in his keynote address. “Sunscreen nanoparticulates ZnO and TiO2 in sunscreens are effective UV filters but there are concerns over their safety when they come into contact with cells. ZnO in particular has been shown to cause DNA damage in vitro—although not in vivo—and small concentrations of Zn ions have been found in blood and urine samples of subjects having applied them topically.”
Grice thus began his work by focusing on whether nanoparticles could penetrate the human skin; and if they could, whether they did anything once there. He described experiments involving the topical application of commercial materials and measurements of their fluorescent emission spectra as a means to track the depth of materials into skin. In the end, his team observed no changes in the metabolism of cells, no changes in TEWL, and only some ZnO traces in the skin, which caused no adverse effects. “This suggested that while nanoparticles could penetrate the skin in in vitro models, since there was no evidence of their penetration in vivo, perhaps something in the living tissue protected against their penetration.”
Other aspects of Grice’s work examined the efficacy of transfollicular delivery, which was found to be 10X faster than transdermal delivery, as well ultra-deformable, novel surfactant, ethanol and cholesterol (SEC)-osomes, designed to twist and squish into the spaces between cells and penetrate deeply, even to the DNA level, for effects such as gene silencing. Throughout his work, Grice described multiphoton tomography as a useful technique to examine skin condition and treatments.
Bozena Michniak-Kohn, of Rutgers University in New Jersey, USA, also looked at skin penetration but from a medical view—i.e., to treat psoriasis topically. She described the development of tyrospheres: biocompatible, tyrosine-derived polymers that can act as carriers to load lipophilic drugs for application to the skin. “The challenge has been to deliver materials not across the skin, but into the skin,” said Michniak. She explained that the tyrospheres increase the solubility of the drugs contained therein to increase their driving force into skin. “The drug or cosmetic active is thus released from the carrier in a slow, diffusion-controlled manner.” Liquid chromatography–mass spectrometry quantified the amount of active delivered into the layers of the skin and showed no evidence of the tyrospheres themselves penetrating the skin.
Taking her work further, Michniak noted, “These are all simple vehicles, but what happens when you put them into a formulation?” Results were the same: the concentration of active was the highest in the dermis and no transdermal delivery was observed. Further, only small, insignificant differences were noted in concentrations of the active delivered from a gel formula vs. the simple carrier. Michniak emphasized, however, “When you put anything into a formulation, you have to check that the actives contained are released.”
Select the Right Skin Delivery System for Your Application
Science and Applications of Skin Delivery Systems bridges the gap between the two extremes of all-science and all-systems books. This book was written by experts who know the potentials as well as the limitations of the delivery systems.Science and Applications of Skin Delivery Systems and Skin Barrier: Chemistry of Skin Delivery Systems