As a result of corrosion, copper and silver release positively charged ions into their environment that are harmful to bacteria in a number of ways, preventing their growth or killing them entirely. This effect has long been exploited, for example by coating implants with these metals to prevent bacterial infection.
There are tricks that can be used to release more ions and intensify this effect. For example, the team led by materials researcher Professor Alfred Ludwig used a so-called sputtering system, by which the thinnest metal layers or tiny nanospots can be applied to the support material. Depending on the order or amount of individual metal applications, different surface textures are produced. If a precious metal such as platinum is applied at the same time, silver will corrode faster and release more antibacterial ions.
Ludwig outlines the principle of sacrificial anodes: “In the presence of a more noble metal, the poorer metal sacrifices itself. A surgical research team led by Prof. Dr. Marina Breisch from Manfred Köller has demonstrated that this sacrificial anode system can The effectiveness of bacteria, and has been published many times.”
However, whether viruses can also become harmless in this way has not been investigated in detail. Professor Stephanie Pfänder, a virologist, said: “That’s why we analysed the antiviral properties of surfaces coated with copper or silver and various silver-based sacrificial anodes, and also investigated the combination of copper and silver to understand possible synergies effect.” The team compared the effectiveness of these surfaces against bacteria with their effectiveness against viruses. “
Marina Breisch describes the effect of these surfaces on Staphylococcus aureus. “The surface with the sacrificial anode effect, especially the nanopatches composed of silver and platinum and the combination of silver and copper, effectively prevented bacterial growth.”
A different story emerged with SARS-CoV-2: a thin copper coating drastically reduced the viral load after just one hour. On the other hand, the sputtered silver surface had only a small effect, and the silver nanopatches had no effect on the virus.
“In conclusion: we demonstrate that copper-coated surfaces have a clear antiviral effect against SARS-CoV-2 within one hour, whereas silver-coated surfaces have no effect on viral infectivity,” says Stephanie Pfänder.
The successful interdisciplinary collaboration between materials research, clinical microbiology and virology will be deepened in future studies to identify other materials with the broadest antimicrobial effects.