New bactericidal surface materials: sharp stainless steel and copper bring double blows to bacteria

In order to help fight against the increase of antibiotic resistant bacteria, researchers have been experimenting with drug free methods to kill pathogenic bacteria for many years. A new type of stainless steel just does this, and it is convenient to use and economical.

According to a global survey described in Nature magazine, in 2019 alone, antibiotic resistant bacteria killed more people than HIV/AIDS or malaria. Superbacteria are associated with the death of nearly 5 million people, directly causing more than 1.27 million deaths. According to a report of the United Nations Environment Programme, the World Health Organization lists antibiotic resistance (AMR) as one of the top ten global health threats. By 2050, bacteria evolved to avoid our drugs may cause as many as 10 million deaths. This will be equivalent to the global cancer death toll in 2020.

Understandably, Georgia Institute of Technology researchers are worried about such figures, and they begin to use mechanical methods rather than chemical methods to deal with antimicrobial resistance. In particular, they are trying to fight against gram-negative bacteria, such as Escherichia coli, cholera and salmonella, because they contain a protective capsule that makes them particularly good at fighting traditional antibiotics.

Anuja Tripathi, the main author of the study, said: "It is relatively easy to kill gram-positive bacteria without chemicals, but processing gram-negative bacteria is a major challenge because their cell membranes are thick and multi-layer. If these bacteria continue to exist on the surface of objects, they will grow rapidly. My goal is to develop a bactericidal surface without antibiotics, which can effectively fight against gram-negative and gram-positive bacteria. "

Using the electrochemical process, Tripathi's team etched the stainless steel surface to produce thousands of tiny micro spikes. Then they used electrochemistry again to bond copper ions to the surface of the steel. The result is a material that can destroy antibiotic resistant bacteria in two ways. They pierced their protective outer membranes, while copper, known for its antibacterial properties since ancient Egypt, further degraded their cell membranes.

In the test, steel and copper materials reduced the number of Gram negative Escherichia coli by 97%, and led to a 99% reduction of Gram positive Staphylococcus epidermidis. This material has been shown to achieve these effects in 30 minutes.

In fact, this new material only contains a very thin layer of copper, which means that it avoids the high cost of materials, thus maintaining the affordability of the new steel/copper combination. Moreover, since it can tear up bacteria with sharp spines, it should prevent bacteria from evolving ways to escape death, just as they can use chemical treatment.

This is not the first time that we have seen the use of mechanical methods to crush resistant bacteria. This year alone, we reported a spiny titanium material, inspired by the wings of dragonflies, which can tear up a common respiratory virus, and a spike on a nanocrystal, which rotates in the light and can cut bacteria into small pieces. Georgia Institute of Technology's research went further, adding copper. Based on the terrible warning of health institutions on antibiotic resistance, do we really have enough methods to fight against the attack of superbacteria?

The study was published in the journal Small.

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