High Surface Area Copper for Enhanced Antibacterial Activity

At Australia’s RMIT University, a team of scientists developed a copper alloy that can kill bacteria on its surface 100 times faster than normal copper. The researchers created the material using copper and manganese atoms, and then removed the manganese after the material was formed, resulting in a comb-shaped copper structure with a greatly increased surface area. The development could help fight drug-resistant bacteria in healthcare facilities and could be useful in antimicrobial door handles and handrails, face masks, respirators, and ventilation systems.

Images magnified 120,000 times under a scanning electron microscope show golden staphylococcal bacteria cells after two minutes on a) polished stainless steel, b) polished copper and on c) and d), the micro-nano copper surface of the equipment.

Copper is naturally antibacterial, and copper ions produce toxic effects on exposed bacterial cells. While this natural phenomenon is helpful, it can be a bit time consuming for routine antimicrobial use, and it can take hours to kill bacteria on a surface. For frequently touched objects, such as door handles in a busy hospital corridor, this is likely not fast enough to prevent the transfer of bacteria from one person to another.

“A standard copper surface will kill approximately 97% of golden staph in four hours,” Ma Qian, one of the developers of the new material, said in a press release. “Unbelievably, when we placed golden staph on our specially designed copper surface, it destroyed over 99.99% of the cells in just two minutes. So not only is it more effective, it is 120 times faster. Our copper structure has proven to be remarkably powerful for such a common material. “

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The new copper alloy, magnified 2000 times under a scanning electron microscope, shows its unique micro-comb structure.

To create the copper alloy, the researchers used a copper mold casting process and incorporated manganese and copper into the alloy. However, a low-cost chemical process called deblocking helped them remove the manganese, leaving a porous copper structure. Not only does the surface area increase dramatically compared to unmodified copper, but the material is hydrophilic and attracts bacteria from the surface water and creates additional stress for them.

“Our copper is made up of micro-scale comb-shaped cavities and within each tooth of that comb structure there are much smaller nanoscale cavities; it has a massive active surface area, ”said Jackson Leigh Smith, another researcher involved in the study. “The pattern also makes the surface super hydrophilic, or water-loving, so that the water lies on it as a flat film rather than droplets. The hydrophilic effect means that the bacterial cells struggle to maintain their shape while being stretched by the surface’s nanostructure, while the porous pattern allows copper ions to be released faster. These combined effects not only cause the structural degradation of bacterial cells, making them more vulnerable to poisonous copper ions, but also facilitate the absorption of copper ions by bacterial cells. It is this combination of effects that results in a very accelerated elimination of bacteria. “

The researchers hope that copper alloy could be a very useful antimicrobial surface in a variety of healthcare settings and devices, including ventilation systems, door handles, and even face masks.

Study in magazine Biomaterials: Robust bulk micro-nano hierarchical copper structures possessing exceptional bactericidal efficacy

Via: RMIT

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