Researchers from the Institute of Bioengineering and
Nanotechnology (IBN) of the Agency for Science, Technology and Research (A*STAR)
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.
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
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.”