A new type of sunscreen based on bioadhesive nanoparticles (BNP) has been developed by researchers at Yale.
While the commercial chemical sunscreens partially get absorbed into the body, causing hormone changes and increasing the chance of skin cancer. The sticky polymer nanoparticles in the BNP sunscreen are big enough not to penetrate the skin and are adhesive enough not to go into the pores/hair follicles.
With less than 5wt% of the active ingredient (UV-filter concentration) found in commercial sunscreens, BNP sunscreen is able to provide an equal protection against the sun.
They also researched a more indirect side effect of UV rays. When the UV-filter concentration absorbs light, a chemical reaction results in the production of reactive oxygen species (ROS) which can potentially act as allergens. When allergens penetrates the skin, they are able to cause damage to the cells and increase the chance of skin cancer.
As seen on this image, the ROS from UV filter penetrates the skin. With the BNP sunscreen the ROS is unable to escape the nanoparticle, making it much safer for indirect UV damage.
The nanoparticles have an enclosed padimate O, with a hydropholic coating around it. Making the sunscreen not only water resistant, but also making it stick to the outer skin surface. Tests showed that a significant amount of the sunscreen was still sticking to the skin of mice after a few days. It is possible to wipe off the sunscreen with a towel.
There is still a concern over what these particles can do if they do make it into deeper skin layers through broken skin. The next step for the researchers will be to test the sunscreen on human subjects. If we are lucky we could see these BNPs being implemented in sunscreens and other topical agents within the next few years.
Source: Nature Materials