Researchers at RMIT in Australia have developed a drug-free approach to kill bacteria and fungi that can infect surfaces on medical implants. Such pathogens can cause serious and difficult-to-treat infections around medical implants, sometimes requiring the removal of the implant. In addition, many microbes are increasingly resistant to common antibiotics, highlighting the need for drug-free approaches. This new technique is inspired by the nanopillars present on dragonfly wings, which can skewer microbial cells, killing them. The researchers used a relatively simple plasma etching technique to create such nanopillars on titanium surfaces, and tested their ability to kill multi-drug resistant Candida cells, a fungal pathogen behind many medical device infections.
Medical implants can rectify many unfortunate clinical situations, but they can also harbor microbes that can colonize the surfaces of the device after implantation. This typically leads to a nasty infection, which is often complicated by biofilm formation, and may require the eventual removal of the implant. Antimicrobial drug resistance is a further complication, and this has inspired these researchers to create a drug-free surface modification that can kill microbes indiscriminately.
They used a plasma etching technique to create tiny pillars on titanium, which is used in many medical implants. The tiny spikes are approximately the height of a bacterial cell, and when a cell settles on the surface, the spikes can lead to perforations in the cell that can cause its death. In studies so far, the researchers have shown that if the cell does not die outright, it will still perish a little later because of the damage it sustained.
“The fact that cells died after initial contact with the surface — some by being ruptured and others by programmed cell death soon after — suggests that resistance to these surfaces will not be developed,” said Elena Ivanova, a researcher involved in the study. “This is a significant finding and also suggests that the way we measure the effectiveness of antimicrobial surfaces may need to be rethought. This latest study suggests that it may not be entirely necessary for all surfaces to eliminate all pathogens immediately upon contact if we can show that the surfaces are causing programmed cell death in the surviving cells, meaning they die regardless.”
An intact Candida cell on polished titanium surface (left), and a ruptured Candida cell on the micro-spiked titanium surface (right).
While it is easy to visualize the antimicrobial activity as a simple skewering action, it is more like a stretching action, as the cells are pulled by different pillars. “It’s like stretching a latex glove,” said Ivanova. “As it slowly stretches, the weakest point in the latex will become thinner and eventually tear. This new surface modification technique could have potential applications in medical devices but could also be easily tweaked for dental applications or for other materials like stainless steel benches used in food production and agriculture.”
Study in journal Advanced Materials Interfaces: Apoptosis of Multi‐Drug Resistant Candida Species on Microstructured Titanium Surfaces
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