Molecular warfare

August 24, 2017

Bacterial biofilms are a major problem in medicine: tough, toxic and nearly indestructible. But Cyrille Boyer thinks he’s found a way to beat them.

bacterial biofilms

Featured image above: Cyrille Boyer of UNSW’s School of Chemical Engineering. Credit: Quentin Jones

We often picture disease-causing bacteria as an invading army of individual cells. But in fact, these pathogens find strength in numbers, glomming onto each other and coating the surfaces around them in near-indestructible protective sheets called biofilms.  

These biofilms pose an enormous problem in medicine. They can form directly on lungs, wounds or other living tissue, and can contaminate medical devices such as catheters, prosthetic joints and other implants. Food production, water treatment, and other industrial facilities can also fall victim to their powers. Many types of biofilms resist antibiotics, and the bacteria they’re built from churn out toxins that make their human hosts sick. Yet, no good way exists to destroy them. 

Cyrille Boyer, a polymer chemist and Co-Director of the Australian Centre for Nanomedicine at UNSW in collaboration with Dr Nicolas Barraux, believes that a nanomaterial he designed – a polymer-coated iron oxide particle that heats up when a magnetic field is applied – can provide a solution.

In December 2015, he and his colleagues reported in Nature’s open access journal Scientific Reports that using these nanoparticles to raise the temperature of a biofilm by just a few degrees caused it to break apart.

bacterial biofilm

bacterial biofilm
Biofilm of staphylococcus aureus (or ‘golden staph’) on a catheter; bloodstream infections with this bacteria kill 20 to 35% of patients within a year.

Solo-swimming bacteria are much more susceptible to antibiotics, Boyer explains, so the researchers could then send in another type of particle to deliver medicine that kills off the bugs. They are now planning on testing the particles in live mice and discussing a potential partnership with a company interested in taking the method into clinical development.  

Polymer chemist Eva Harth from Vanderbilt University in Tennessee, describes it as an out-of-the-box strategy to treat a long-intractable problem.

This paper shows that a polymer construct can be much more effective than a traditional drug,” she says. 

“There’s an enormous need for new technologies” for breaking up biofilms, says Rodney Dolan, Director of the Biofilms Laboratory at the US Centers for Disease Control and Prevention. “It’s a very creative, very interesting approach, particularly combining particles with magnetic fields to localise and control the effect.” 

Smart, easy, elegant solution

Boyer is a master of materials, and his specialty is controlling the effects of the nanoparticles and polymers he creates.

“In my team, we are looking at how to make smarter nanoparticles, where the nanoparticle acts in response to an external signal,” he says.

In 2015, Boyer was awarded the Australian Prime Minister’s Prizes for Science Malcolm McIntosh Prize for Physical Scientist of the Year for his work using light to catalyse the assembly of polymers with distinct properties. Although the biofilm-busting technique doesn’t employ light, it’s right in line with Boyer’s vision of building ‘smart’ particles whose behaviour can be controlled for therapeutic purposes.  

Boyer created his iron oxide particles in response to a discovery made by microbiologist Nicolas Barraud at the Institut Pasteur in Paris, France. The two met by chance, when Barraud, then based at UNSW, was attending a conference out of town. He popped
in on a talk Boyer was giving about polymers that release nitric oxide.
“It was a serendipitous meeting,” he says. “We realised we were working at the same university, a few buildings across.”  

Barraud was studying the basic properties of biofilm formation and dispersal, and had recently discovered that nitric oxide could break up biofilms. Back in Sydney, he asked Boyer if he could try the polymers described in the talk. Boyer was happy to comply, and the approach worked relatively well, according to both researchers.

They published a couple of papers, filed a patent, and are still pursuing the project — but the drawback was that nitric oxide is a gas, which makes it difficult to spatially and temporally control its release.

Barraud had also discovered that giving biofilms a tiny temperature boost made the bacteria move and shake, ultimately disbanding them, but he couldn’t work out how to apply the discovery. Then one day, over a beer, Boyer mentioned that he could create particles that induce local heating. “I’ve worked with chemists before,” Barraud says, “and usually as soon as you get into the lab you run into problems. But with Cyrille’s polymer, it was very straightforward,” he says.  

That’s because in this project and others, Boyer focuses on identifying simple, well-worked-out polymerisation methods that can be used in specific applications. “Very precise materials that are easy to make – that’s the key,” says Harth. “It’s smart, easy, and elegant – that’s what he’s after.”

– Alla Katsnelson

For more stories at the forefront of engineering research, check out Ingenuity magazine.

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