Minerals such as titanium dioxide and zinc oxide are very effective sunscreen ingredients, but they can harm coral reefs if used in their non-nanoparticle form. An experimental new sunscreen forgoes the minerals altogether, replacing them with "just-as-effective" plant pollen.
The pollen-based sunscreen was developed by a team of scientists at Singapore's Nanyang Technological University, working with colleagues from Seoul National University in South Korea.
They experimented with both sunflower and camellia flower pollen, getting the best results from the latter. Camellia pollen is considered nonallergenic, and is widely available as a relatively inexpensive health supplement.
The researchers utilized "a proprietary water-based process that does not involve harsh chemicals or high heat" to remove the inner contents of individual pollen grains. This left behind an outer coating of a tough natural biopolymer known as sporopollenin, which was converted into a transparent microgel no thicker than a human hair.
When applied to animal skin in lab tests, that gel was found to block harmful ultraviolet rays as effectively as a conventional mineral- or chemical-based sunscreen with an SPF rating of about 30. This means it blocked approximately 97% of the UV rays.
As an added benefit, because sporopollenin absorbs less energy than regular sunscreen in the visible to near-infrared spectrum, the microgel was found to keep the skin a total of 5 ºC (9 ºF) cooler for 20 minutes after application.
And importantly, the gel had no effect on corals after being added to the water in which they were living, even after 60 days. By contrast, the corals died of bleaching within six days of exposure to commercial sunscreens.
"We know that pollen is naturally UV-resistant, as its shell needs to protect its inner contents from harsh environmental conditions, including sunlight," says the lead scientist, NTU's Prof. Cho Nam-Joon. "We wanted to develop an affordable and effective natural sunscreen that is non-allergenic to humans and eco-friendly to the environment."
The research is described in a paper that was recently published in the journal Advanced Functional Materials.
Source: Nanyang Technological University
