Sea-food dressing

Extracts from seaweed and crab shells have long been used, separately, in the treatment of wounds, but now scientists have combined the substances to create a new medical textile.

Chitocel was developed by Bolton University researchers using alginate and chitosan. Together, the substances exhibit properties that the scientists say makes a hypoallergenic wound dressing that is antimicrobial, absorbs moisture and helps stop bleeding (haemostasis).

‘We are not the first team to look at alginate and chitosan, but we are the first to successfully create a combined fibre strong enough to be made into a wound dressing,’ said project leader Dr Mohsen Miraftab. The initial university prototype of the material measured 10 sq cm and three to five millimetres thick.

Alginate is a powdery product from algae. Chitosan, which also comes in a powder form, starts off as chitin, a form of starch found in the shells of marine crustaceans, such as crabs or lobsters. The substances are both widely available.

‘The fibre we produced as Chitocel is combed during processing and comes up as a web,’ said Miraftab. ‘Then it is needle-punched to make it into a non-woven structure. That can have a sticky backing so when it sits on the wound, our fabric will be in the centre of that sticky material. Once it does its job it can be peeled off and thrown away.’

When fibres are processed into a non-woven form, Miraftab said it resembles tissue paper. The scientists opted for this structure because it is the cheapest method of production and the number of fibres per square centimetre is high, resulting in a big surface area. This allows the Chitocel to absorb large quantities of liquid.

The absorption properties of Chitocel are thanks to the alginate.

‘Alginate has the ability to absorb high amounts of liquid, in this case exudate [blood and plasma that comes out of the body] plus the ability to gel. These two features are very important when the wound is about to heal because it needs a moist environment to heal properly,’ said Miraftab.

This means alginate is ideal for wounds that are medium to heavily wet, rather than dry wounds such as burns.

Chitosan provides the material with its other healing-aid properties.

‘I understand that bandages and dressings made out of chitosan are being used in the Iraq war, and it is claimed to be saving many lives,’ said Miraftab.

‘Chitin itself is not soluble and it does contain a lot of impurities. So to make it into the more user-friendly chitosan, it is purified and then deacetylated (a technique for obtaining chitosan). The advantages are the antimicrobial and haemostatic properties, which stop the bleeding,’ he added.

To mix alginate and chitosan, the molecules of the latter need to be broken down, which the Bolton team did using hydrolysis. According to Miraftab, simply breaking down chitosan brings out further healing properties.

‘A long period of hydrolysis breaks down the chains and make them more accessible to bonding with the alginate,’ said Miraftab. ‘Also, we understand that the action of breaking down is helpful in healing the wound because it exposes the N-acetyl-glucosamines that are present within chitosan — and these are fundamental in the formation of fibroblasts (collagen-producing cells) in the tissues,’ he added.

Miraftab said the nearest product to Chitocel is Aquacel, which is made from carboxymethyl cellulose (CMC). ‘That has the ability to gel and absorb liquid, but it is not antimicrobial,’ he said.

In the past, people have used chitosan to produce films and pharmaceutical capsules, but attempts to make it into a fibre have not been successful. This is because when a fibre is made entirely of chitosan, it has a tendency to be very brittle.

Mixing it with alginate, however, removes this problem and therefore allowed the Bolton team to create a useable fibrous wound dressing.

Sumed UK, a medical dressings company based in Oxfordshire, is helping the researchers develop Chitocel commercially.

‘Results from the semi-commercial production have actually shown the dressing to be better than we have produced in the laboratory. At the moment we are doing clinical analyses and once those are all cleared, we foresee it becoming available in the next 12 months,’ said Miraftab.