Silk may embody luxury and extravagance, but the soft, strong material has therapeutic features too: it may one day help people with burns or skin ulcers heal faster and with less pain.
Dr Asma Khalid, Vice-Chancellor’s Postdoctoral Fellow at RMIT University and Associate Investigator at the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP), is developing silk bandages that can not only monitor wound repair, but also fight off infections and encourage new skin growth.
These thin yet stretchy sheets of interconnected, uniformly sized fibres are relatively easy to make. Dr Khalid dissolves silk cocoons in a water-based solution — not before removing the silkworm, of course — then gently pours the liquid onto a surface and lets it dry.
As the water evaporates, silk proteins in the solution self-assemble into a clear, elastic membrane.
‘We can transform that liquid silk to a variety of beautiful structures, including transparent films that look like glass, but [are] actually foldable and flexible,’ Dr Khalid said.
When laid over a wound, a silk film provides structural support and protection from infection. It’s also biocompatible: in other words, it does not elicit an immune response. And being biodegradable, these films eventually fall apart in the body and melt away without a trace.
Today, people with burns or diabetic ulcers have their wounds covered with a dressing. These are removed and replaced regularly to check for infection and administer ointments or other treatments. Not only is this incredibly painful, it increases the risk of introducing a pathogen to the vulnerable tissue.
Dr Khalid and colleagues are now combining silk films with a host of particles to monitor temperature and pH — two indicators for how well the tissue is healing — and developing a handheld detector for remote sensing.
‘A high temperature can signal infection, while pH tells you how the wound is healing. If it’s acidic, it means the wound is not healing well,’ she said.
‘This would be especially useful in diabetic wounds or third-degree burns where we don’t really want to remove the dressing, but want to diagnose if there is inflammation or infection.’
A transparent silk bandage also provides, in more ways than one, a valuable window into the wound. CNBP Chief Investigator Prof Rob McLaughlin’s Bioengineering Imaging Group at the University of Adelaide is using a technique that looks through Dr Khalid’s silk films to ‘see’ layers below the skin’s surface where blood vessels reside.
The technology, called optical coherence tomography, can track capillaries as they regrow and snake their way through the tissue — another indicator that a wound is healing correctly.
To enhance the healing process, silk bandages may be loaded up with water-soluble medications or antimicrobial treatments that are released as the film degrades. And because their dissolving rate can be tweaked, silk film bandages have the potential to safely administer drugs over a few days, weeks or even months — all while protecting the wound.
While Dr Khalid and her collaborators are refining these technologies before they’re used in burn wards and diabetes clinics, she says nanoparticle-embedded silk bandages for wound monitoring have substantial commercial potential.
Silk cocoons are a sustainable raw material, and transforming them into films, using water-based processes at room temperature, is environmentally friendly.
‘I always used to think of silk as a fabric,’ Dr Khalid mused. ‘But when I did the literature review, I realised that it’d been used in medicine for centuries as a suture. Silk may be a fancy material, but it has a lot of benefits in health and medicine.’