Part of technology’s mission is to improve performance, and now Australian researchers may have optimized something nature has done well for thousands of years.
You may be aware of copper’s natural antimicrobial properties — a more recent example is the US Environmental Protection Agency (EPA) announcing that certain surfaces made from copper alloys can provide long-term effectiveness against viruses, including the SARS-CoV-2 virus responsible for COVID-19. The downside is the metal can take hours to kill a bug.
Scientists at RMIT University in Australia and the country’s national science organization CSIRO have developed a new copper alloy that they report can kill bacteria more effectively — and more than 100 times faster — than standard copper. “We found that copper nanostructured surfaces, produced by dealloying copper-manganese alloys, are capable of eliminating over 99.9% of bacteria within only two minutes,” said Jackson Smith, PhD, lecturer at RMIT’s school of engineering and the study’s lead author.
The idea, Smith said, was to pursue a superior alternative to plain copper and copper alloys like brass or bronze, which “have been used for thousands of years to kill bacteria.” (One well-cited example: The ancient Egyptian book Smith Papyrus, written between 2600 and 2200 B.C., describes copper being used to clean chest wounds and sterilize drinking water.)
Smith’s team first uses a conventional metal casting process to form a specific copper-manganese alloy. Then it’s submerged into a corrosive solution — a “dealloying” process — to produce the pure copper “nanostructures” that make the new substance unique.
The hope is this discovery becomes a game-changer in the way we combat both bacterial and viral infections — particularly antibiotic-resistant superbugs.
How Copper Kills
Say an infectious cell lands on a copper surface. What happens next?
Copper ions breach the culprit’s outer cell membranes and disrupt the cell’s metabolic activity, impeding its ability to create energy or breathe. “Dissolved copper ions have shown to target and degrade several physical aspects of bacteria necessary for its survival, including the cell wall, cell membrane and even DNA,” explains Smith. The result: A dead cell.
As high-touch surfaces like doorknobs and elevator buttons are responsible for the spread of many germs, researchers have experimented with adding copper to these surfaces. This can be especially helpful in shared spaces, like medical settings, office buildings, and city buses.
One study compared bacterial infection rates in three different hospital ICUs — conventional surfaces vs copper alloy surfaces — and saw up to 58% fewer infections in rooms featuring copper surfaces. Meanwhile, a 2021 trial in Vancouver, Canada monitored copper surfaces on public transit. More than 99% of bacteria died within an hour of landing on the surface.
Copper certainly has its bandwagon. Chick-fil-A has experimented with copper door handles in a North Carolina location. The Sao Paulo, Brazil airport outfitted its check-in counters with antimicrobial copper. And NHL’s St. Louis Blues and Los Angeles Kings players lift dumbbells made from copper.
A More Efficient Killer
So does this copper breakthrough change things? At the very least, it’s a start. Thus far, Smith and his team have only tested their new form of copper against non-drug resistant Staphylococcus aureus, the bacteria behind staph infections.
And as mentioned, traditional copper surfaces take time to kill — anywhere from 1-8 hours depending on the organism. How is this new copper alloy capable of killing staph within 2 minutes?
The dealloying process produces a copper structure that is microscopically porous, which means “our copper super-fine nanostructures provide a large surface area,” said Smith. This allows far more copper ions to release from the surface, causing faster damage to the bacteria compared with traditional copper.
Another factor: When the bacteria sit on the surface of the nanostructures, the bacteria bind to them, which stretches the bacterial cell to the point of rupturing. “Both of these factors lead to a superior killing rate compared to traditional copper surfaces,” he said.
So, What’s Next?
Smith’s team will now conduct further studies, putting this new copper alloy to trial on a larger scale, and against a wide range of pathogenic bacteria. “We would then like to incorporate real world touch surfaces — door handles or handrails — using this scalable dealloying technique and test their effectiveness in a real healthcare environment to observe their long-term effectiveness,” said Smith.
Smith hopes to implement these surfaces in clinical trials within healthcare environments and see results within the next few years.
Industry insiders are excited about these latest innovations. “It’s great that facilities now have more antimicrobial copper solutions available that can fit their budget and design needs,” said Adam Estelle, BS, vice president of the Copper Development Association. “We see a number of different solutions available, ranging from adhesive-backed foils that can be retrofitted on existing surfaces, to durable, engineered products made from solid wrought and cast alloys.”
Smith confirms the ease with which this new copper could be deployed. “The unmatched scalability of the process would allow for any geometry or shaped surface to be produced, making commercialization easy,” he said.
That sounds good, of course, but copper is notoriously expensive. Can these new surfaces be made cheaply enough to be practical and widespread? Smith points out that more expensive forms of copper are all about the purity. Electrical or heat transfer applications, for example, require copper purity higher than 99.99%. Antimicrobial copper can be less than 99% pure, and thus cheaper. The extra dealloying process Smith’s team uses does increase cost, “but not by much,” he said.
Although a significantly faster kill rate is appealing, Estelle stresses that market acceptance will come down to multiple factors, like cost, ease of installation, design capabilities, durability, aesthetics, and availability — and ultimately, how effective this copper alloy is long term. “The true public health value of antimicrobial copper surfaces, regardless of how they are deployed, is their ability to continuously kill human pathogens without the need for human intervention, even after repeated contamination events,” he said.
Nicole Pajer is a freelance journalist whose work has appeared in The New York Times, Rolling Stone, AARP, Wired, and more.
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