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Copper more effective than silver in killing covid virus

The material a surface is made of affects how long viruses and bacteria can remain contagious on it. (Image courtesy of Ruhr-University Bochum).

Researchers at Ruhr-University Bochum investigated ways to make copper and silver release even more ions than they normally would as a result of corrosion, a process that helps prevent the growth of bacteria or kill them completely.

In a paper published in the journal Scientific Reports, the scientists describe the use of a so-called sputtering system with which the thinnest layers or tiny nanopatches of the metals can be applied to a carrier material.

Depending on the sequence or quantity in which the individual metals are applied, different surface textures are created. If a precious metal such as platinum is also applied, silver corrodes even faster and releases more antibacterial ions.

“In the presence of a more noble metal, the baser metal sacrifices itself, so to speak,” researcher Alfred Ludwig said in a media statement. This phenomenon is called the principle of the sacrificial anode.

The effectiveness of such sacrificial anode systems against bacteria has already been demonstrated. However, whether viruses can also be rendered harmless in this way has not yet been investigated in detail.

“This is why we analysed the antiviral properties of surfaces coated with copper or silver as well as various silver-based sacrificial anodes, and also examined combinations of copper and silver with regard to possible synergistic effects,” virologist Stephanie Pfänder said.

The team compared the effectiveness of these surfaces against bacteria with the effectiveness against viruses.

Surfaces with sacrificial anode effect, especially nanopatches consisting of silver and platinum as well as the combination of silver and copper, efficiently stopped bacterial growth.

Yet, a different picture emerged with SARS-CoV-2: thin copper layers significantly reduced the viral load after only one hour. On the other hand, sputtered silver surfaces had only a marginal effect, and silver nanopatches did not impress the virus either.

“In conclusion, we demonstrated a clear antiviral effect of copper-coated surfaces against SARS-CoV-2 within one hour, while silver-coated surfaces had no effect on viral infectivity,” Pfänder said.