Using light to create bacteria-fighting polymers

Warwick University team devises lights-mediated method to make and test polymers that can kill “superbugs” on contact

The method would allow the synthesis of large libraries of related polymers

The evolution of bacteria resistant to established methods of controlling them has become an increasingly urgent problem in hospitals and elsewhere. Antimicrobial substances are vital components for fighting diseases and infections in the body, but are also used in personal care products and, for example, contact lens solutions. Bacteria that are immune to their effects can lead to infections.

The Warwick team, led by Prof Matthew Gibson, was investigating whether combinatorial chemistry, a technique used to generate large libraries of related chemical compounds which is widely used in the pharmaceutical industry to determine which compounds have the highest activity, could be used to find new antimicrobial agents. This would allow researchers to “go fishing” for new properties.

The main thrust of the research was to mimic naturally occurring peptides – fragments of large proteins – that have bacteria killing properties. “Whilst many people have successfully mimicked antimicrobial peptides with polymers, the limiting step was the number of different combinations of building blocks you can use,” he said. “We used simple robotics and a light controlled polymerisation, which lets us do the chemistry open to air, without any sealed vials which are essential for most polymer syntheses.”

In a paper in the journal Chemistry: A European Journal, the team explains how they synthesised a variety of polymers based upon methacrylate monomers. Having made their polymers, the group used a robotic method to mix them directly with bacteria to observe how they behaved.

These polymethacrylates were expected to have a different mode of action from antibiotics like penicillin, which work by inhibiting processes within the bacterial cells. Instead, the polymethacrylates should have mimicked the action of peptides that break apart the membranes of bacteria. However, in tests, the peptides made by the team seemed to inhibit the growth of bacteria rather than bursting them open. Team member Sarah-Jane Richards said the group is now investigating this mode of action.