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The researchers from IBN, clockwise from left, Dr Guangshun Yi, Dr Yuan Yuan, Dr Xiukai Li and Dr Yugen Zhang, who developed the dragonfly-inspired nano coating that can kill bacteria spontaneously upon contact. Dr Yi is holding up a piece of zinc coated with zinc oxide nanopillars. / Credit: A*STAR

The researchers from IBN, clockwise from left, Dr Guangshun Yi, Dr Yuan Yuan, Dr Xiukai Li and Dr Yugen Zhang, who developed the dragonfly-inspired nano coating that can kill bacteria spontaneously upon contact. Dr Yi is holding up a piece of zinc coated with zinc oxide nanopillars. / Credit: A*STAR

A*STAR researchers develop dragonfly-inspired anti-bacterial nano coating

Researchers from the Institute of Bioengineering and Nanotechnology (IBN) of the Agency for Science, Technology and Research (A*STAR) have developed a nature-inspired anti-bacterial nano coating for disinfecting frequently touched surfaces such as door handles, tables and lift buttons. Their new research was recently published in the journal, Small.

This technology is expected to be particularly useful in creating bacteria-free surfaces in places like hospitals and clinics, where sterilisation is important to help control the spread of infections.

According to the B.C. Centre for Disease Control, around 80% of common infections are spread by hands. Disinfecting commonly touched surfaces helps to reduce the spread of harmful germs by our hands, but it would require manual and repeated disinfection. Current disinfectants may also contain chemicals like triclosan which are not recognised as safe and effective, and may lead to bacterial resistance and environmental contamination if used extensively.

To tackle this problem, the researchers were inspired by the wings of dragonflies and cicadas, which are covered in nanopillars that look like a bed of nails and prevent bacterial growth. When bacteria come into contact with the surfaces of the wings, their cell membranes get ripped apart immediately and they are killed.

The team led by IBN Group Leader, Dr Yugen Zhang, created a novel nano coating that can spontaneously kill bacteria upon contact. The IBN scientists grew nanopilllars of zinc oxide, a compound known for its anti-bacterial and non-toxic properties. The zinc oxide nanopillars can kill a broad range of germs like E. coli and S. aureus that are commonly transmitted from surface contact.

L - Zinc oxide nanopillars that looked like a bed of nails can kill a broad range of germs when used as a coating on frequently-touched surfaces/ R - E. coli bacteria destroyed by the anti-bacterial coating made from zinc oxide nanopillars/ Credit: A*STAR

Tests were conducted on ceramic, glass, titanium and zinc surfaces, showing that the coating effectively killed up to 99.9% of germs found on the surfaces. Since the coating kills bacteria mechanically rather than chemically, its use would not contribute to environmental pollution. Also, the bacteria will not be able to develop resistance as they are completely destroyed when their cell walls are pierced by the nanopillars upon contact.

Further studies revealed that the nano coating demonstrated the best bacteria killing power when it is applied on zinc surfaces, compared with other surfaces. This is because the zinc oxide nanopillars catalysed the release of superoxides (or reactive oxygen species), which could even kill nearby free-floating bacteria that were not in direct contact with the surface.

This super bacteria killing power from the combination of nanopillars and zinc broadens the scope of applications of the coating beyond hard surfaces.

The researchers also studied the effect of placing a piece of zinc that had been coated with zinc oxide nanopillars into water containing E. coli (Escherichia coli are bacteria found in the environment, foods, and intestines of people and animals. Most strains of E. coli are harmless but some cause food poisoning). All the bacteria were killed, suggesting that this material could potentially be used for water purification.

IBN has recently received a grant from the National Research Foundation (NRF) under the Prime Minister’s Office, Singapore, under its Competitive Research Programme to further develop this coating technology in collaboration with Tan Tock Seng Hospital for commercial application over the next 5 years.

“There is an urgent need for a better way to disinfect surfaces without causing bacterial resistance or harm to the environment. This will help us to prevent the transmission of infectious diseases from contact with surfaces,” said IBN Executive Director Professor Jackie Y. Ying.

Dr Zhang said, “Our nano coating is designed to disinfect surfaces in a novel yet practical way. This study demonstrated that our coating can effectively kill germs on different types of surfaces, and also in water. We were also able to achieve super bacteria killing power when the coating was used on zinc surfaces because of its dual mechanism of action. We hope to use this technology to create bacteria-free surfaces in a safe, inexpensive and effective manner, especially in places where germs tend to accumulate.”

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