Few-layered black phosphorus is highly antimicrobial toward resistant bacteria and fungal species; it is one of the thinnest antimicrobial coatings developed to date and could be used on wound dressings and implants, according to a paper published in the journal ACS Applied Materials & Interfaces.
Black phosphorus is effective at killing microbes when spread in nanothin layers on surfaces like titanium and cotton. Image credit: RMIT University.
Antimicrobial resistance has rendered many conventional therapeutic measures, such as antibiotics, ineffective.
This makes the treatment of infections from pathogenic microorganisms a major growing health, social, and economic challenge.
“Finding one material that could prevent both bacterial and fungal infections is a significant advance,” said Dr. Aaron Elbourne, a researcher in the School of Science at RMIT University.
“These pathogens are responsible for massive health burdens and as drug-resistance continues to grow, our ability to treat these infections becomes increasingly difficult.”
As black phosphorus breaks down, it oxidizes the surface of bacteria and fungal cells. This process, known as cellular oxidisation, ultimately works to rip them apart.
Dr. Elbourne and colleagues tested the effectiveness of nanothin layers of black phosphorus against five common bacteria strains, including Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA), as well as five types of fungus, including Candida auris.
In just two hours, up to 99% of bacterial and fungal cells were destroyed.
Importantly, black phosphorus also began to self-degrade in that time and was entirely disintegrated within 24 hours — an important feature that shows the material would not accumulate in the body.
The authors also identified the optimum levels of black phosphorus that have a deadly antimicrobial effect while leaving human cells healthy and whole.
“Black phosphorus 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,” said Dr. Sumeet Walia, a researcher in the School of Engineering at RMIT University.
“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.”
Z.L. Shaw et al. Broad-Spectrum Solvent-free Layered Black Phosphorus as a Rapid Action Antimicrobial. ACS Appl. Mater. Interfaces, published online April 12, 2021; doi: 10.1021/acsami.1c01739