Each year, hundreds of billions of tonnes of polymers are produced around the world.
The materials made from these chains of small, repeating molecules, including plastics, paints, adhesives, clothing and electronic devices, are virtually everywhere.
As techniques to create polymers become more sophisticated, chemists are designing materials with unique physical properties and functions, opening up applications in targeted drug delivery, energy storage, and diagnostics.
But the process of creating polymers is energy intensive, requiring extremely high temperatures to trigger the necessary chemical reactions, as well as toxic substances, derived from non-renewable fossil fuels.
Associate Professor Cyrille Boyer is working at the cutting-edge of chemical engineering, mimicking nature to develop more sustainable, functional polymers.
The winner of a 2015 Prime Minister’s Prize for Science, the 2016 Le Fevre Memorial Prize from the Australian Academy of Science and a 'rock star' of the Knowledge Nation 100, Boyer’s pioneering approach is inspired by photosynthesis – the process that allows plants, algae and certain bacteria to convert sunlight into energy, stored in the form of natural polymers.
“By using light we can significantly reduce the energy consumption and carry out the polymerisation process at room temperature,” he says. “Light also allows us to precisely manipulate and control the polymer properties.”
Boyer’s group recently became the first in the world to demonstrate that visible light and bacterial chlorophyll, a natural, non-toxic catalyst, could be used to activate the polymerisation process and produce well-defined, functional materials. The results were reported in Chemical Science and the Journal of the American Chemical Society.
“This is very exciting for our group and the polymer community globally, because it means we can now overcome the limitation of toxicity,” he says.
Boyer’s team has also demonstrated another impressive world first: they recently triggered a similar polymerisation process using near-infrared light, which has longer wavelengths than visible light and can penetrate a wider range of materials, including human skin.
Boyer says this will enable non-toxic polymers to be made inside the body, for things like tissue engineering and wound healing, and in implant surgeries.
As Deputy Director of the Australian Centre for NanoMedicine at UNSW Boyer is using his new polymers to develop next-generation drugs that will help keep potentially lethal microbes at bay.
The World Health Organization’s 2014 report on global surveillance of antimicrobial resistance concluded that “without urgent, coordinated action, the world is heading towards a post-antibiotic era, in which common infections… can once again kill.”
In the same year, A Review on Antimicrobial Resistance, funded by the UK government, found that drug-resistant infections could kill 300 million people and cost the global economy $100 trillion by 2050.
Boyer isn’t abandoning antibiotics, but innovating new ways of delivering them via intelligent nanoparticles, in combination with either nitric oxide or carbon monoxide.
One of the big issues in antimicrobial resistance is biofilms, where micro-organisms adhere to each other, building into a layered slimy mass.
“In these structures, microbes are 1000 times more resistant to antibiotics than when they’re in their planktonic form,” says Boyer. “They transfer their resistance genes more quickly, they regenerate and they spread.”
To overcome this, the objective is to deliver the nanoparticles to an infection site in a very controlled manner, says Boyer. Once there, the chemical sends a signal causing the biofilm to breakdown, and the nanoparticle releases its antibiotic, killing the dispersed bacteria.
This work has been done in collaboration with researchers from the Institut Pasteur in France and Nanyang Technological University in Singapore, and research papers describing their innovative drug delivery method and early results have been published in Chemical Science.