Copper is effective against SARS-CoV-2 on surfaces, but not silver.

The material a surface is made of affects how long viruses and bacteria can remain contagious on it. Credit: RUB, Marquard

Copper and silver corrode and emit positively charged ions into their environment, which are detrimental to bacteria in a variety of ways, preventing their growth or killing them totally. This effect has been used for a long period of time, for example, by covering implants with these metals to prevent bacterial infection. There are a few strategies that may be used to increase the amount of ions released and hence the strength of this impact. For instance, the team led by materials researcher Professor Alfred Ludwig employs a technique known as sputtering to deposit the thinnest layers or tiniest nanopatches of metal onto a carrier material. Different surface textures are formed depending on the order or quantity of the particular metals used. When combined with a precious metal such as platinum, silver corrodes more rapidly and releases more antimicrobial ions.

“In the presence of a more noble metal, the baser metal makes a kind of self-sacrifice,” Ludwig explains, elaborating on the notion of the sacrificial anode. The surgical research team led by Professor Manfred Köller and Dr. Marina Breisch has already proved and reported the efficiency of such sacrificial anode systems against germs multiple times.

However, whether viruses can be rendered harmless in this manner has not been thoroughly examined. “This is why we evaluated the antiviral capabilities of copper and silver-coated surfaces, as well as various silver-based sacrificial anodes, as well as copper and silver combinations for possible synergistic effects,” virologist Professor Stephanie Pfänder explains. The researchers compared the efficiency of various surfaces against germs and viruses.

Regarding the effect of the surfaces on Staphylococcus aureus, Breisch notes that “sacrificial anode surfaces, particularly nanopatches composed of silver and platinum, as well as a mixture of silver and copper, effectively inhibited bacterial growth.”

With SARS-CoV-2, a distinct picture emerged: after only one hour, thin copper coatings drastically lowered the viral burden. On the other hand, sputtered silver surfaces had a negligible effect, while silver nanopatches had no effect on the virus. “In conclusion, we demonstrated an immediate antiviral effect of copper-coated surfaces against SARS-Cov-2, but silver-coated surfaces had no effect on viral infectivity,” Stephanie Pfänder concludes.

The present discovery was published in Scientific Reports, and further research will be conducted to identify additional compounds with the broadest antimicrobial effect imaginable.

Further information: Toni Luise Meister et al, Nanoscale copper and silver thin film systems display differences in antiviral and antibacterial properties, Scientific Reports (2022). DOI: 10.1038/s41598-022-11212-w

Journal information: Scientific Reports

Source: Ruhr-Universitaet-Bochum