Researchers have developed a new form of sunblock, based on adhesive nanoparticles, which they say is not only as effective as traditional chemical sunblocks and water resistant, but also cannot penetrate the skin and potentially enter the bloodstream.
In a paper published online in Nature Materials (Sept. 28, 2015), the sunblock’s developers note that there are concerns about many of the organic and inorganic ultraviolet (UV) filters used in conventional commercial sunblocks causing hormonal changes or cellular damage after penetrating the skin. This risk is due to the way absorption of UV radiation by some filter molecules can lead to the production of reactive oxygen species (ROS). These ROS in turn can cause cellular damage or facilitate skin cancer, the authors note.
The new sunblock involves the UV filter Padmate O (PO) being encapsulated in bioadhesive nanoparticles which are easily suspended in water but adhere well to the stratum corneum, according to the paper. The concentration of the filter is much smaller in the experimental formulation than in commercial sunblocks as well, the authors note.
“We found that when we apply the sunblock to the skin, it doesn’t come off, and more importantly, it doesn’t penetrate any further into the skin,” the paper’s senior author, Mark Saltzman, PhD, said in a press release from Yale (Sept. 28, 2015). Dr. Saltzman is the Goizueta Foundation Professor of Biomedical Engineering at Yale university in New Haven, Conn. “Nanoparticles are large enough to keep from going through the skin’s surface, and our nanoparticles are so adhesive that they don’t even go into hair follicles, which are relatively open,” he said.
In mouse models of UV irradiation, the nanoparticle-based sunblock was equally effective in preventing sunburn as a commercial sunblock. The study also showed that while the commercial product had penetrated deeply into the mice’s skin, the new sunblock remained entirely on the surface.
The new sunblock also created a very durable barrier, according to the findings, remaining on the skin for several days even with exposure to water. As well, when it was applied to the skin the nanoparticle product was transparent, potentially giving it an aesthetic advantage over opaque inorganic sun blocks containing titanium dioxide or zinc oxide, the authors note.