Media Release
November 29, 2005
Antibacterial coatings cut infection rates
Putting antibacterial coatings on hip and knee implants and
biomedical devices such as catheters could cut infection rates following
surgery and significantly reduce health care costs and improve quality
of life for patients, researchers at the University of South Australia
have found.
A significant number of hip and knee implants are prone to infection
after surgery and in many cases are not amenable to treatment with
antibiotics, according to Hans Griesser, Professor of Surface Science
and Deputy Director of UniSA’s Ian Wark Research Institute.
“For patients in this situation it may be necessary to remove the
implant from the infected site, cleanse the wound and undergo
replacement surgery within a short time after original implantation,
causing significant trauma, especially for the elderly,” Professor
Griesser said.
Catheters can also be a source of bacterial infections, which can spread
from the skin to the incision for catheter insertion, and have been
known to cause anaphylactic shock resulting in death, according to
Professor Griesser. Hospitals combat this problem by removing and
replacing catheters at frequent intervals, and at considerable cost to
the health care system.
“Another significant problem caused by bacterial contamination of
medical devices is bacteria that settle on contact lenses and cause
inflammation and, more rarely, infections,” Professor Griesser said.
Researchers at The Wark™ are developing nanometre thin coatings for
biomedical implants and biomedical devices that prevent bacterial
colonisation of implants that result in septic inflammation problems.
“We are using molecules called furanones, which are derived from natural
chemicals originally extracted from Australian macro algae seaweed that
grows off the eastern coast. The chemicals produced by these macro algae
were found to prevent the colonisation of microbial organisms such as
bacteria and fungi on their surfaces, helping to keep the algae clean.
Researchers at the University of New South Wales developed synthetic
analogues of the natural compounds and discovered that these chemicals
also keep synthetic surfaces clean when placed on those surfaces in a
marine environment. This provided the impetus for studying their use in
biomedical device applications,” Professor Griesser said.
Furanones have a unique advantage in that they act differently to other
antibiotics. Unlike antibiotics, they don’t kill bacteria. This means
that the furanone compounds should not cause bacterial resistance,
according to microbiologists.
“When bacteria sit on the surface, they first anchor themselves
individually and then send out signalling molecules called homoserine
lactones to other bacteria, which do the same, talking to each other via
these signalling molecules until they reach sufficient density as a
group on the surface. The bacteria then change their metabolism and
start producing a slimy biofilm that protects them from antibiotics.
Sitting under the protective biofilm, the bacteria multiply and grow,
and that’s what causes infection,” Professor Griesser said.
Professor Griesser likens this process, called quorum sensing, to the
example of soccer hooligans who on their own are quite ineffective but
when they group together, can be a powerful force that creates havoc of
disastrous proportions.
It’s the furanones that come to the rescue by irreversibly switching off
the bacterial signalling mechanism. Without the signal, the bacteria
think that they are alone; they don’t start producing the biofilm and
eventually die on the surface.
“We attach the furanones by covalent bonding to our biomedical devices.
We stress covalent bonding because it is important that we anchor them
very firmly to the surface, making it impossible for them to break away
and travel into remote organs such as the brain or liver,” Professor
Griesser said.
UniSA PhD student in applied science (minerals and materials), Sameer
Al-Bataineh, has developed a fundamental understanding of the
antibacterial coatings and how to make them. Using model substrates made
from metal and plastics, he developed methods for attaching the
furanones, and analysing their surface properties and chemical
composition to get a detailed understanding of how they are best
applied.
Al-Bataineh’s research has been supervised principally by Professor
Griesser and co-supervisor Dr Leanne Britcher at The Wark™, with
co-supervision by microbiologist Professor Mark Willcox from the Vision
Cooperative Research Centre at the University of New South Wales, where
he and Dr Hua Zhu assessed the antimicrobial efficiency of the coatings.
“The result is a good understanding of how the coatings work and in
which way we can make them work for best effect. We have established
recipes for practical applications of the furanone coatings onto
different devices. We now have a very good basis for tailoring these
coatings towards particular biomedical devices and are using this
knowledge to work with Sydney-based company, Biosignal Limited, to
develop antibacterial contact lenses,” Professor Griesser said.
“This is an excellent example of where we can apply fundamental
knowledge gained in a PhD towards commercial applications that we
believe will have health benefits for a significant number of people. If
we can apply this to biomedical implants and other biomedical devices,
we will have a major impact on the health of the nation and the cost
benefits will be enormous.”
Media contact
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Geraldine Hinter, office (08) 8302 0963 mobile 0417 861 832 email geraldine.hinter@unisa.edu.au