Researchers used polymerization to create large molecules that still block UV radiation but are too big to penetrate our skin, coral, and algae. 

A new coral-friendly polymeric UV filter may be more effective at preventing sunburn than existing sunscreens.

Researchers used polymerization to create large molecules that still block UV radiation but are too big to penetrate our skin, coral, and algae. 

The study was published in the March 1, 2023 issue of Cell Reports Physical Sciences.

“This is an initial exploration of a new strategy to design bio-friendly and coral-friendly polymeric UV filters,” says senior author Lei Tao, a chemist at Tsinghua University, in a news release. “We hope this leads to the next generation of sunscreens.”

Tao’s team first used a chemical reaction to randomly generate different ring-shaped molecules with similar structures to avobenzone, an existing UV filter. Then, they used a second chemical reaction to link these ring-shaped molecules together in different combinations, thus creating a suite of candidate polymers to choose from. The researchers zeroed-in on the best candidate by comparing the polymers’ SPF value and capacity to absorb UV radiation.

When the researchers tested the winning polymer’s ability to prevent UV-induced skin-burn in mice, they found that it was significantly superior to oxybenzone, avobenzone, and two commercial sunscreens. It was also safe: the mice did not absorb the polymer through their skin, nor did they experience any inflammation or other skin damage.

The polymer UV filter also appears to be non-hazardous for coral and algae, two groups of organisms that are harmed by currently available chemical sunscreens. Chlorella algae was unaffected when the team grew it in the presence of small amounts of the polymer, as were two common types of coral. These same corals bleached and died within 6 and 20 days of exposure to oxybenzone, respectively.

One caveat of the UV filter is that it is not biodegradable due to the structure of its chemical backbone, but the researchers say that this is just the first step towards developing the next generation of environmentally safe UV filters.

“We have some ideas for other non-random polymerization methodologies that we could combine with the chemical group that we developed in this study to create an environmentally friendly and readily biodegradable UV filter,” says Tao. “Meanwhile, we will try to work with companies to test the current polymer and see whether it can be used in sunscreens.”