Silver and gold

Materials World magazine
,
3 Sep 2015

Following seven years of work, University of Bolton Professor Mohsen Miraftab speaks with Khai Trung Le about the innovative wound dressing that aims to challenge the market leaders.

Ousting an industry gold standard is always going to be a challenge. More so, toppling one that has endured for decades. However, a team led by Professor Mohsen Miraftab, University of Bolton, UK, has developed a wound dressing intended to rival commercial efforts with some unusual influences – seaweed and crabshell.

Aquacel, an antibacterial wound dressing made from carboxymethylcellulose, has been widely celebrated by healthcare professionals since 2003. Miraftab did not hesitate to espouse its qualities, noting, ‘It has a very high degree of absorption, superior to anything else available right now. It doesn’t fall apart, so once it’s picked at the moisture, you can just lift it off from wounds. It has a nice gel-like feel. A lot of nurses like it.’

However, Aquacel lacks antimicrobial properties and, in 2008, Miraftab’s team began developing a dressing that would best it, beginning with the medical properties of alginate and chitosan, found in algae and crustaceans.

Miraftab commented, ‘Chitosan is a known element in pharmaceutical manufacturing, and comes in many forms including capsule, powder and film. It has a natural ability to enhance wound healing, as well as being naturally antimicrobial. However, in a fibre form, it is rather brittle and hydrophobic.’

The Bolton team sought to pair chitosan’s properties with alginate, which Miraftab elaborated, ‘has excellent liquid properties, which is important in wound dressings as the body produces its own natural defence to wounds, for example, plasma, which needs to be absorbed and held away from the skin.’

Alginate and chitosan have been utilised prominently in medicinal use, even dating back to ancient China – ‘In battles, there are tales of crabs being smashed open and thrust into wounds. There is logic in this. Chitosan is antimicrobial and accelerates cell activity. In effect, it heals and kills bacteria’ – although Miraftab’s team has been the first to successfully create a combined fibre strong enough to form into a wound dressing, through a patented technique employing hydrolysis and wet extrusion processes.

‘Modification of fibres with unhydrolysed chitosan generally resulted in a significant reduction in tenacity, and a reduction in elongation percentage, if a water washing stage was not used. Reduction of chitosan molecular weight had a positive effect on its ability to penetrate the alginate fibres, not only increasing fibre chitosan content, but also reinforcing fibre structure and thus enhancing tensile properties.

‘The question became, can we combine the qualities within chitosan and alginate to create a hybrid fibre, which is exactly what we have been working on over the past seven years. We call our hybrid fibre alchite, and it performs better than Aquacel – it is more absorbent, it has a high degree of gelling, is naturally antimicrobial and is haemostatic.’

Production was hampered by a number of issues, including ensuring the dressing gelled to an acceptable standard, and Miraftab stated, ‘One of my PhD students worked on resolving this for three years.’

Other cited advantages over Aquacel detailed in the paper A new carbohydrate-based wound dressing fibre with superior absorption and antimicrobial potency, written by Miraftab and co-authors Rashid Masood, National Textile University, Pakistan, and Valerie Edward-Jones, Manchester Metropolitan University, UK, include featuring less silver in the fibre than other commercial dressings, and with a slower dispersion rate.

‘Silver is a premium material and therefore has a high cost. Excessive use of silver not only increases manufacturing and hence retailing costs but can also initiate unnecessary complications in the wound healing process […] commercial dressings generate high concentration of silver in liquid media very quickly. This in turn would lead to generation of silver chloride and cause possible skin rash.’ Discolouration and adverse allergic reactions are also common side effects.

For a video demonstrating the absorptive properties of the alchite wound dressing, check out the September issue in the Materials World App. Visit app.materialsworld.org