A smart polymer that changes colour to signal infection and then releases antibiotics could make medical devices safer.
Researchers in Saudi Arabia are working on technology to cut down on the number of patients being infected by bacterial contamination from re-usable tools such as X-ray imaging plates, which are used for mouth scans in dentistry.
Smart coatings have previously used nano-crystals embedded with silver ions, which have antibacterial properties, but tend to leach too rapidly over time.
However, a team at the King Abdullah University of Science and Technology in Saudi Arabia have developed a method that uses gold nanoparticles instead. These gold nano-particles have an advantage over other methods because they can change how they interact with light in response to specific bio-molecular interactions.
However, it wasn’t just as simple as swapping silver for gold. The team, led by Niveen Khashab, an associate professor at the university, had to develop a new type of ‘nano-filler’ to create their smart material.
“Nano-fillers are small chemical agents distributed in the matrix of a polymer composite,” she explained. “They’re dopants, so they improve on the regular material and introduce new properties—in our case, making the coating antibacterial.”
The team’s approach, which is described in a paper published in Advanced Healthcare Materials, involves treating gold nanoparticles with bacteria-killing lysozyme enzymes. They are then attached to slightly larger silica nanoparticles that have been stuffed with molecules of antibiotic drugs.
This complex cocktail emits a fluorescent red glow in normal, clean, conditions. However, when bacteria is present, the lysozyme enzyme rips the gold and the silica nano-clusters apart. This simultaneously switches off the fluorescent effect, and releases the antibiotic cargo.
The team have tested their new polymer in experiments with E. coli, and found less leaching compared to the silver ion method. They compared x-ray dental plates with and without the smart polymer coating, and found that they could determine the level of bacterial contamination by looking for colour changes under a UV light.
There was no change in the quality of the images obtained using these plates. “The process of coating is easy,” said Khashab. “We are looking at improving this technology to include other medical devices of different sizes and shapes.”