In 2012, two researchers at the University of Nottingham in the United Kingdom discovered a group of new materials capable of repelling bacteria. Precisely why bacteria steer clear of this material, however, is not known. Now, the scientists have each won a prestigious research award worth a combined £2 million ($3.4 million) to solve the mystery. There is a lot at stake: bacteria-resistant polymers could lead to a significant reduction in hospital infections acquired through implanted medical devices.
Morgan Alexander, Professor of Biomedical Surfaces in the School of Pharmacy and Paul Williams, Professor of Molecular Microbiology, in the School of Life Sciences at the University of Nottingham, have each received a Wellcome Trust Senior Investigator Award to conduct the joint project.
Controlling the number of infections acquired through indwelling medical devices such as catheters, intravenous tubes, and artificial joints could significantly reduce the number of medical complications, save thousands of lives a year, and reduce medical costs. The Senior Investigator Awards will fund a centre of excellence, which will study the underlying mechanisms behind the resistance these materials show to bacterial attachment and biofilm development.
When asked if they had any preliminary theories at this stage, Alexander told PlasticsToday, "We have a number of possible theories but without experimental evidence we are not keen to go to press with them, since they would be readily shot down as pretty speculative, especially now that we have the money to explore our hypotheses properly. We are happy to say what it is not," he adds. "We are pretty sure that the physicochemical properties of the polymers (often cited as causal in the literature) are too simple to explain the resistance response observed, which is why we are investigating bacterial signaling processes via the surface."
"Bacteria are highly adaptable micro-organisms, and we need to discover the genetic basis of how they sense and respond to chemically distinct polymer surfaces," adds Williams. "By combining our expertise in materials science and microbiology we are taking an interdisciplinary approach to solving a major medical problem."
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| Morgan Alexander (foreground) and Paul Williams are shown with the pin printer they used to array polymers at the University of Nottingham. |
Bacteria typically attach to implanted devices as single cells and eventually form "slime cities" or biofilms. Within these biofilms, the bugs can hide to avoid detection and are protected from attack by the body's own immune defenses and antibiotics.
As we reported in PlasticsToday last month in an article titled, "Researchers mobilize to battle hospital-acquired infections," approximately one in 25 U.S. patients will contract a hospital-acquired infection (HAI), according to the Centers for Disease Control and Prevention (CDC). In 2011, an estimated 722,000 HAIs were recorded in U.S. acute care hospitals, says the CDC, and close to 75,000 patients with HAIs died during their hospitalization.
The lead polymer used by Alexander and Williams is a copolymer of monomer 4 and di(ethylene glycol) methyl ether methacrylate (DEGMA), but cyclic and aromatic hydrocarbon side chains were found to have similar bacteria-resistant properties. "Thus far, we have dip-coated silicone catheters with the polymer using a DCM solution," Alexander explains. "[The catheters] have been oxygen plasma etched, although we are investigating other interfacial bonding pretreatments for silicone," he adds.
In their initial research, Alexander and Williams found that silicone devices coated with the material achieved a nearly 97% reduction in bacteria-covered surface area ccompared with commercially available devices.
The discovery of the polymer could not have been possible without a technology developed with the help of experts from the Massachusetts Institute of Technology that allows the simultaneous screening of unique polymers. "The technology developed with the help of MIT means that hundreds of materials could be screened simultaneously to reveal new structure-property relationships. In total, thousands of materials were investigated using this high throughput materials discovery approach, leading to the identification of novel materials resisting bacterial attachment. This could not have been achieved using conventional techniques," said Alexander in a statement published in 2012 following the announcement of the discovery.
The newly discovered materials have been licensed to Camstent Ltd, with whom the University is developing coated urinary catheters through the first clinical trial, which is being prepared for this autumn.
A better understanding of the mechanisms used by bacteria to interact with polymer surfaces could inform rational design of improved bacteria-resistant polymers in the future and achieve a transformative change in preventing device-centered infections, according to the researchers.
The Wellcome Trust, which is helping to move this research forward with the award, was established in 1936 on the death of Sir Henry Wellcome to support projects dedicated to the improvement of human and animal health. The charitable foundation spends approximately £600 million ($1 billion) annually in the United Kingdom and internationally supporting biomedical and medical research.
