Copper is an extremely useful element in the fight against bacteria, and its anti-microbial properties have been shown to be effective against antibiotic-resistant bacteria, fungi, and even viruses. This makes the material extremely useful in situations where the presence of bacteria on a surface could lead to dangerous infections, like in a hospital.
Researchers from Australia have now delivered an improved copper surface that can kill some bacteria 120 times faster than regular copper. As reported in the journal Biomaterials, the material was tested against Staphylococcus aureus, AKA golden staph, a bacterium that was responsible for 50,000 deaths per year in the United States in data collected 15 years ago.
“A standard copper surface will kill about 97% of golden staph within four hours,” senior author Professor Ma Qian, from RMIT University, said in a statement. “Incredibly, when we placed golden staph bacteria on our specially-designed copper surface, it destroyed more than 99.99% of the cells in just two minutes. So not only is it more effective, it’s 120 times faster. Our copper structure has shown itself to be remarkably potent for such a common material.”
The secret of the material is in its microscopic structure. To achieve it the team used a special copper mold casting process that creates an alloy made of copper and manganese. The manganese is then chemically removed in a way that is both cheap and scalable.
What’s left behind is a surface that is full of tiny cavities, a perfect trap for microbes to fall into and be killed off by the copper ions.
“Our copper is composed of comb-like microscale cavities and within each tooth of that comb structure are much smaller nanoscale cavities; it has a massive active surface area,” lead author Dr Jackson Leigh Smith explained.
The peculiar pattern created by the removal of manganese makes the surface hydrophilic, meaning water-attracting. Water forms a film rather than droplets on it.
“The hydrophilic effect means bacterial cells struggle to hold their form as they are stretched by the surface nanostructure, while the porous pattern allows copper ions to release faster. These combined effects not only cause structural degradation of bacterial cells, making them more vulnerable to the poisonous copper ions, but also facilitates uptake of copper ions into the bacterial cells,” Smith added.
These effects are a winning combo that ends up greatly accelerating the demise of the bacteria. The team hopes that this surface could be employed in many different places where dangerous bacteria might proliferate such as hospitals, schools, homes, and public transport.
The team will also investigate if the surface is effective in killing SARS-CoV-2, the virus that causes COVID-19.