Black phosphorus coating kills superbugs then self-destructs
Bacteria are becoming more and more dangerous, as they evolve resistance to our best drugs. New weapons against these so-called “superbugs” are desperately needed. Now, researchers at RMIT have developed a coating that quickly kills bacteria and fungi, then dissolves within 24 hours – and best of all, the mode of attack is something they can’t develop defenses against.
The discovery of penicillin was one of the most important scientific breakthroughs of the 20th century, making potentially lethal infections easily treatable. But decades of overuse and misuse has worn away our upper hand in the battle, as bacteria develop resistance to each antibiotic we make. It’s now getting to the point where certain strains are immune to everything we can throw at them, threatening to cast us back to “a dark age of medicine” in the coming decades.
To try to turn the tide back in our favor, scientists are regularly developing or discovering new antibiotics, but that just kicks the problem further down the road. Other research is investigating non-chemical alternatives that the bugs won’t be able to become resistant to – physical attacks that use intense lighting, liquid-metal shredders, poisoned arrows, or molecular drills to tear into them.
And that’s the kind of technique that the RMIT team has now created. The key is black phosphorus (BP), an ultra-thin material that’s mostly being studied for use as a possible silicon replacement in electronics. Its antimicrobial functions have also been noted, but not previously investigated. Ironically, one of BP’s biggest disadvantages in electronics turns out to be useful in medical applications.
“BP breaks down in the presence of oxygen, which is normally a huge problem for electronics and something we had to overcome with painstaking precision engineering to develop our technologies,” says Sumeet Walia, co-lead researcher on the study. “But it turns out materials that degrade easily with oxygen can be ideal for killing microbes – it’s exactly what the scientists working on antimicrobial technologies were looking for. So our problem was their solution.”
As the BP breaks down, it produces reactive oxygen species, which damage the outer membrane of bacteria and fungi, ultimately killing them. The BP itself disintegrates completely, so it wouldn’t accumulate in the body where it can harm human cells.
In the lab, the team tested thin layers of BP against five bacteria, including E. coli and the superbug MRSA, and five fungi, including Candida auris. They found that within two hours, up to 99 percent of the cells were killed, and within 24 hours the BP itself had broken down entirely.
This shows that the material could be used to make coatings for “medically-relevant surfaces,” such as wound dressings or implants, which would quickly kill off any potential infections before dissolving away itself. Importantly, this technique shouldn’t contribute to further antimicrobail resistance.
“Our nanothin coating is a dual bug killer that works by tearing bacteria and fungal cells apart, something microbes will struggle to adapt to,” says Aaron Elbourne, co-lead researcher on the study. “It would take millions of years to naturally evolve new defenses to such a lethal physical attack. While we need further research to be able to apply this technology in clinical settings, it’s an exciting new direction in the search for more effective ways to tackle this serious health challenge.”
The research was published in the journal Applied Materials & Interfaces.