Q&A: Gel-based wound dressings
16 February 2010
What was your aim?
We wanted to make a gel that would change the conditions within a wound to speed up healing. When skin is wounded, cells called keratinocytes move in a sheet from the edges to the centre of the wound. In the lab, the top speed of a keratinocyte is 50 μm/h. On the skin they go a little slower, around 10 μm/h. We wanted to speed this migration, promoting healing.
Why did you use a gel-based dressing?
Previous work has shown that low calcium and high magnesium levels increase the speed of keratinocyte migration, so we wanted to include something to produce these conditions. We used a hydrogel, which is essentially a jelly. They're used in many things, including wound dressings, dental adhesives and contact lenses. We tested different gels that our team in Chemistry produced and found one that can accelerate and improve healing of superficial burns and scalds.
Why is calcium so important?
Calcium makes the world go round! The fluid that fills wounds has a lower calcium level than tissue fluid, but a higher level of magnesium. Reproducing these conditions in a skin model of wounding increases the rate of migration. We reproduced other groups' experiments, varying concentrations of calcium and magnesium to find the 'sweet spot' in terms of the rate of migration. We then set about making a gel that would mop up the right amount of calcium and donate sufficient magnesium to reproduce those amounts.
What skin model did you use?
Traditional models were keratinocytes growing in a single layer on plastic dishes. We now have more complex models. We use a piece of dermis [the lower layer of skin that provides mechanical strength and flexibility] donated from patients undergoing reconstructive surgery through our colleagues in Plastic Surgery. We add cells grown from skin and grow it in conditions similar to those real skin is exposed to, creating a 3D model. The resulting epithelium looks and behaves like skin. Just like skin, if you wound it, it heals up.
Why did you focus on burns?
Wounds caused by burns often require skin grafts, which can contract as they heal. Enzymes in the skin cells that migrate during healing start remodelling the dermis, which can get smaller. This contraction makes wounds look puckered and wrinkly as they heal and can cause deformity of limbs as, for example, large burns heal. Patients who receive skin grafts often require further surgery to release this contracted skin.
Did you find anything surprising?
We found that skin contracted less with gels that didn't donate magnesium. However, we also know that magnesium is required to promote cell migration, so you could imagine using one formulation of a gel loaded with magnesium for the first two weeks of healing, to promote cell migration. You could then switch to a magnesium-free formulation to block contraction. We didn't expect to find this link between magnesium and contraction - it's a nice result.
What's your ultimate research aim?
To work with burns surgeons to make something which we can move to the clinic to reduce skin graft contraction, which is particularly bad in children who have suffered burns injuries.
What do you do outside of work?
I'm a keen guitarist, although most of my time is taken up raising two boisterous girls (aged five and two). I enjoy climbing and tinkering with cars and motorbikes.
Image: Dr Anthony Bullock
Reference
Bullock AJ et al.
Development of a calcium-chelating hydrogel for treatment of superficial burns and scalds. Regen Med 2010:5(1):55-64.
Supported by a Wellcome Trust University Translation Award.
