Coatings & surface treatment
adding chemical functional groups that alter its properties. For instance, Su and his team functionalised one of their nanopillar surfaces with an enzyme. “We know that enzymes are more lethal to Gram-positive bacteria,” he says. “And we noticed that this did actually kill more Gram-positive bacteria.” You may also need to alter the surface properties based on the function of the implant itself. Su gives an example: you might have an implant that needs to promote growth of the host cell while keeping microbes at bay. Designing a surface that can do both is a challenge Su and his team have been working on over the past few years.
There may be additional requirements depending on where in the body the implant is going to be applied as well, adds Michalska. She hopes that in future, there will be more focus within the field on how surfaces could meet all these different criteria at once. “Right now, we’re still quite stuck in looking at ‘How do I increase the bactericidal activity of these surfaces?’” Plus, having an additional antimicrobial mechanism up your sleeve can be useful if the nanopattern gets scratched or damaged. After all, the properties brought on by the physical pattern will only stay in effect if the pattern stays intact. Damage could happen if the implant was subject to screwing or hammering, for instance, while the features of the pattern might be
altered if the surface becomes covered in microbial debris. “If one mechanism fails, you can still rely on the other,” says Michalska.
Worth the wait It’s going to be a while before we see these surfaces investigated in clinical trials, let alone in medical devices on the market. But in the meantime, there’s been interest in non-medical applications, such as air or water filtration. These efforts could help us to better understand the antibacterial mechanisms at play, says Su. What about viruses and fungi? There’s been less research on this front, but we may see more movement in the coming years. Some nanopatterned surfaces might be effective on viruses, says Ivanova, but they’re particularly tough to kill because they’re so small. But, she adds, as nanofabrication becomes more advanced, we may soon be able to design surfaces with even tinier features. With fungi, Ivanova and her colleagues showed that a surface inspired by dragonfly wings caused rupturing of fungal spores. Improvements in nanofabrication technology will really help move the needle here, Ivanova emphasises. “The key is the precision at nanoscale, that’s the main challenge.” And our capabilities have already come a long way, she says. “Ten years ago, we couldn’t even dream that it would be possible to [create nanopatterns] with this precision.” ●
Parylene Medical and Electronics Coating
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www.parylene.co.uk +353 91 780 300 Curtiss-Wright, Surface Technologies Division, Parkmore Business Campus, Parkmore West, Galway, Ireland 104
www.medicaldevice-developments.com
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