Scientists at the University of Nottingham, in the UK, have discovered a new class of polymers that they say are resistant to bacterial attachment. These new materials could lead to a significant reduction in hospital-acquired infections and medical device failures.

Fig. 1 – Dr. David Scurr monitors the surface analysis of polymer samples using time-of-flight secondary ion mass spectrometry (ToF-SIMS).
Medical device-associated infections can lead to systemic infections or device failure, which have cost the National Health Service, the publicly funded healthcare system in the UK, upwards of £1 billion a year. Affecting many commonly used devices, such as urinary and venous catheters, bacteria form aggregate communities known as biofilms. This “strength in numbers approach” protects them against the body’s natural defenses and against antibiotics.

Researchers led by Professor Morgan Alexander, and Professor Martyn Davies in the School of Pharmacy and Professor Paul Williams in the School of Molecular Medical Sciences, have shown that when the new materials are applied to the surface of medical devices they repel bacteria and can prevent them from forming biofilms. Their results from the four-year project were published in the journal, Nature Biotechnology.

Technique Used to Discover Novel Materials

The researchers screened thousands of different chemistries and tested their reaction to bacteria. To reduce the time needed to screen so many materials, they used a process that allowed them to screen thousands of unique polymers simultaneously. Up to 1,200 materials were tested at the same time on a single slide. (See Figure 1)

Using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) the scientists used a pulsed primary ion beam to desorb and ionize species from a sample surface. The resulting secondary ions were accelerated into a mass spectrometer, where they were mass analyzed by measuring their time-offlight from the sample surface to the detector.

Alexander said: “This is a major scientific breakthrough — we have discovered a new group of structurally related materials that dramatically reduce the attachment of pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli). We could not have found these materials using the current understanding of bacteria-surface interactions.”

“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.” he explained.

The new materials prevent infection by halting biofilm formation at the earliest possible stage — when the bacteria first attempt to attach themselves to the device. In vitro testing was very successful, so the researchers moved on to in vivo testing and found that the animal models they used were able to clear the bacteria as well.

In the laboratory, the scientists were able to reduce the numbers of bacteria by up to 96.7 percent — compared with a commercially available silver-containing catheter — and were effective at resisting bacterial attachment in a mouse implant infection model. By preventing this bacterial attachment, the body’s own immune system could kill the bacteria before any biofilm could be generated.

Bacterial attachment and subsequent biofilm formation have been key challenges to the performance of medical devices. Although this research is in the early stage, the results so far look promising, they say.

The next stage of this research will be to develop the manufacture of these coatings to enable the performance of these materials to be assessed clinically. The inventors are in earlystage discussions with a number of medical device companies. For more information and a discussion of the materials, a video can be seen at http://www.techbriefs.com/tv/bacteria-resistant.

University of Nottingham
Queen’s Medical Centre, Nottingham, UK
http://www.nottingham.ac.uk/mol/index.aspx