Possible new fillers for UV-blocking in cosmetic applications

Women with yellow sun glasses in front of a pink background

Women with yellow sun glasses in front of a pink background

A study shows shown that the recently emerged mesoporous Magnesium Carbonate (MMC) can be used as a support for UV-blocking semiconductors without compromising their performance. MMC-TiO2-ZnO showed interesting properties for potential application as a filler material in cosmetics with UV screens. In a recent study Michelle Åhlén, Ocean Cheung , and Maria Strømme, Upsalla Univeristy Sweden analysed amorphous mesoporous Magnesium Carbonate (MMC) as a functional support for UV-blocking semiconductor nanoparticels for cosmetic applications.

Fillers in modern sunscreens

Modern sunscreens are traditionally divided into two main groups: organic/chemical sunscreen filters, which absorb UVR, and inorganic/physical sunscreen filters, which mainly scatter and reflect UVR. Inorganic filters (e.g., TiO2 and ZnO) are usually preferred over chemical filters as they generally do not induce skin irritation and have limited skin penetration. However, a prerequisite for the use of TiO2/ZnO particles is that they can be coated with materials such as silica, alumina, poly(methyl methacrylate), or dimethicone.

Semiconductors absorb and reflect

The reason for this is that TiO2 and ZnO belong to a class of materials denoted as semiconductors, which can absorb as well as reflect UVR. The absorption of UVR leads to the formation of electron–hole pairs in the material that can react with adsorbed molecules on the surface of the particles, which unfortunately can lead to the generation of free radicals and reactive oxygen species (ROS). By coating the surface of TiO2 and ZnO with the previously mentioned compounds, such reactions can usually be prevented, however, this would increase the cost of the material. Furthermore, to increase the cosmetic elegance of a sunscreen, much of the TiO2/ZnO formulated for sunscreen use today contains particles within the nanometer size range (20–50 nm). However, the inclusion of TiO2 and ZnO nanoparticles in formulations that can lead to the formation of airborne nanoparticles is not considered safe, as the nanoparticle agglomerates could have adverse health effects if inhaled.(14−16) By associating the use of semiconductor nanoparticles, a material that can incorporate such nanoparticle aggregates without greatly affecting their UV-blocking properties, as well as possibly reducing their ability to facilitate free radical (or ROS) production, would be of interest.

Study of mesoporous magnesium carbonate (MMC)

Highly porous amorphous mesoporous magnesium carbonate (MMC) with a Brunauer–Emmett–Teller (BET) surface area over 600 m2·g–1 was evaluated as a micrometer-sized support for TiO2 and ZnO semiconductor nanoparticles. In their study Åhlén  et al. have shown that the recently emerged MMC material can be used as a support for UV-blocking semiconductors without compromising their performance. MMC-TiO2-ZnO showed interesting properties for potential application as a filler material in cosmetics with UV screens. Incorporating TiO2 and ZnO nanoparticles within micrometer-sized MMC particles could reduce the risk of nanoparticle exposure. The MMC support does not affect the overall SPF values of the semiconductors but drastically decreased their photocatalytic activities in an aqueous environment, which may indicate a lower risk of harmful free radical production. Further studies including examining the ROS generation under UV light and detailed biocompatibility studies are important for potential real-life cosmetic applications of MMC-TiO2-ZnO.

The study was published in ACS Omega 2019,  4, 2, 4429-4436.

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