Nanoparticles Keep Sunscreen on the Skin

Materials Today Volume 00, Number 00 January 2016 NEWS News Nanoparticles keep sunscreen on the skin Encasing the active ingredient of sunscreens inside sticky polymer nanoparticles stops penetration into the skin, preventing exposure to potentially harmful chemicals, researchers at Yale University have found. Commercial sunscreens contain organic or inorganic ultraviolet (UV) filters that block radiation from the sun, which can cause sunburn, skin aging, and skin cancers. But over the past few decades, studies have indicated that organic UV filters in particu- lar can penetrate the skin or hair follicles and find their way into the bloodstream and other bodily fluids, where they could act as allergens or hormone disruptors. In combination with sunlight, there are also con- cerns that some of these active agents can generate reactive oxygen species (ROS) that cause damage at the cellular and DNA level. To get around this problem, W. Mark Saltzman and his team encapsulated one such organic UV filter, padimate-O, with polymeric bioadhesive nanoparticles (or Transmission electron microscopy images of BNPs. The scale bar represents 200 nm. (Photo credit: Yang BNPs) [Deng, et al., Nat. Mater. (2015), Deng.) doi:10.1038/nmat4422]. The nanoparticles, which are typically just under 100 nm in diameter, comprise a polylactic acid (PLA) on the surface and do not penetrate The BNP-based sunscreen has an addi- core and a surface of hyperbranched poly- into the skin, in marked contrast to non- tional practical advantage—while it is water glycerol (HPG). The UV filter is held in the bioadhesive nanoparticles or padimate-O resistant, it can be readily wiped off with a core of the nanoparticle and the hydroxyl alone. Moreover, a much lower concen- towel or left to slough off with dead skin surface is converted to one rich in aldehyde tration of active sunscreen has a compa- cells without any harmful effect. groups, which stick to biological molecules rable anti-UV effect when applied in Encapsulating padimate-O in nanoparti- like proteins. combination with BNPs compared with cles appears to have another benefit, as well. ‘‘The bioadhesive nanoparticles adhere commercial formulations. In fact, the In the researchers’ study, the BNP-based strongly to the skin and retain UV filter researchers found that just 5% of the formulation significantly reduces a type of molecules within the core,’’ explains Saltz- amount of UV filter used in commercial DNA damage called double-strand breaks. man. sunscreens is needed to achieve the same ‘‘We have taken UV agents that are In mouse models, the team found level of protection in their nanoparticle- known to be effective, combined them with that the UV filter-containing BNPs remain based formulation. materials that are known to be safe, and 1369-7021/http://dx.doi.org/10.1016/j.mattod.2016.01.003 1 Please cite this article in press as: C. Sealy, Mater. Today (2016), http://dx.doi.org/10.1016/j.mattod.2016.01.003 MATTOD-688; No of Pages 2 NEWS Materials Today Volume 00, Number 00 January 2016 produced a better sunblock,’’ says Saltzman. now planning the first tests of the BNP- Peter J. McHugh of the University of ‘‘[Our] sunblock is more effective, longer- based formulation on human volunteers. Oxford. lasting, and less toxic than any previously ‘‘This is a promising approach that could This paper was originally published in described.’’ protect against the collateral damage po- Nano Today (2015), doi:10.1016/j.nantod. Saltzman believes the tactic should tentially inflicted by the penetration of 2015.10.003. work with other UV filters too, and is active sunscreen agents into cells,’’ says Cordelia Sealy NEWS 2 Please cite this article in press as: C. Sealy, Mater. Today (2016), http://dx.doi.org/10.1016/j.mattod.2016.01.003.

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