Scientists have been inspired by the fast hydrolysis of RNA in water for engineering a biodegradable plastic (PLA) that can degrade in seawater within a week.
The world’s first fully synthetic plastic was invented in 1907 by Leo Baekeland. Since then, the widespread success and dominance of plastics has unfortunately led to widespread environmental problems. This is mostly due the materials slow decomposition rate in natural ecosystems.
Today, over 8 million tons of plastic end up in the ocean every year. This not only negatively impacts the marine environment and wildlife, but it also affects human health. Toxic contaminants that are released by plastics due to prolonged exposure to seawater accumulate in marine food webs over time and are transferred to humans through the consumption of seafood causing safety hazards.
Understandably, the worldwide challenge of marine plastic pollution is pushing scientists to make advances in the field of biodegradable polymers. Polylactide (PLA) is a promising biodegradable polymer that is used in several applications. It can be manufactured from natural resources, such as corn and potato starch, and rapidly degrades under specific conditions. However, PLA degradation rates in seawater are very slow. In fact, research has shown that PLA does not lose any mass in 25°C seawater, even after an entire year.
Faster-degrading PLA
Historically, researchers have developed several approaches for producing faster-degrading PLA. However, each of these are linked with drawbacks, such as altering the materials properties can render them un-useful. But recently, a group of scientists took a different route. They were inspired by the fast hydrolysis of RNA by intramolecular transesterification, which is the process of RNA degradation that occurs spontaneously in aqueous solution. Compared to DNA, which is very stable against hydrolysis, RNA hydrolysis occurs much faster via intramolecular transesterification. The study was published in the Journal of the American Chemical Society.
To simulate the RNA-inspired mechanism, the team installed phosphoester breaking points with hydroxyethoxy side groups, similar to those found in RNA, into the PLA backbone. After being immersed in seawater, the weight of the engineered PLA and the release of lactic acid were measured. Lactic acid is a degradation product of PLA. Excitingly, it was found that the PLA with a high concentration (15%) of the RNA-inspired breaking points broke down completely into lactic acid after two weeks. On the other hand, PLA polymers with lower concentrations took longer, with some even taking several years.
Using RNA to control plastic degradation
Essentially, the scientists in this study used RNA-inspired breaking points to vary the speed of PLA degradation in seawater for the first time. The findings suggest that it is possible to tailor the rate of PLA degradation, depending on the number of breaking points in the material. Moreover, the thermal and mechanical properties of the plastic remained unchanged.
Additionally, the potential applications of these RNA-inspired breaking points are not limited to PLA. Adding breaking points to speed the decomposition of other plastics is feasible and it would be possible to translate the general concept to other slowly degrading polymers. This is hugely exciting because it could become a key strategy for preventing additional marine pollution in the future.
Image credit: Environmental Health News
