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Materials Materials
The pros of
zwitterionic
here’s a reason that polyethylene glycol (PEG) is used in so many biomedical and medical device applications: it’s a highly biocompatible polymer that doesn’t biofoul. That is, it doesn’t allow contamination by microbes such as bacteria. However, there are structural and chemical- related properties of PEG that create instabilities – such as being easy to oxidise, possessing a low thermal stability, and being immunogenic (it can set off the body’s natural defences, causing an antibody response). This limits the lifetime of PEG-based devices – which is not ideal for a lot of applications, especially medical implants that go inside the body. Selecting other materials that are biocompatible and robust enough to withstand the biofluids and testing biological environments inside the body has
T 74
polymers
Polyethylene glycol, or PEG, is widely used in medical devices and implants. But it’s susceptible to degradation when exposed to oxygen and can be unstable at warmer temperatures. Zwitterionic polymers, on the other hand, which have oppositely charged groups in their repeating units, have emerged as an alternative offering versatility, enhanced stability and superior biocompatibility. Liam Critchley explores the advantages of zwitterionic polymers and how they can be applied in medical devices.
been a challenge. “Non-specific adsorption of biomacromolecules on material’s surface – such as biofilm formation starting with the adsorption of organic molecules followed by bacteria – is a challenge for many materials being used in medical devices,” says Peng Zhang, professor in the Department of Polymer Science and Engineering at Zhejiang University. “PEG is the most studied non- fouling material for biological applications, but due to its structural instability and immunogenicity, its in vivo applications are limited in the long term.” Zwitterionic polymers have emerged as a good option for overcoming the shortcomings of PEG in medical devices as they have an enhanced stability and high biocompatibility. Zhang notes that “zwitterionic polymers have gathered a lot of attention over the last
Medical Device Developments /
www.medicaldevice-developments.com
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