Even the smallest wound is potentially serious, so something as simple as a finger plaster and a little disinfectant can make the difference when it comes to preventing a nasty infection. But a dressing can do more than just keep out germs. That’s the idea behind work of the Laboratory of Thermodynamics in Emerging Technologies (ETH) in Zurich, Switzerland, where Prof. Dimos Poulikakos and his team of engineers and biologists are developing a new plaster that not only protects a wound from infection, it can also accelerate healing through the use of specially contoured silicone that promotes cell migration.

How wounds heal is a very complex process that involves all sorts of chemical and biological functions in an overlapping cascade that breaks down into four phases. In the first, the body fights to control bleeding. In the second, it combats infections. In the third, it rebuilds the damaged tissues and in the fourth, it closes and seals the wound. The third, rebuilding, phase is called the “proliferative” phase. As part of this phase, special cells called fibroblasts migrate into the wound and help to rebuild tissue by making collagen and constructing a framework on which new tissue can grow. Though there are many other processes going on at the same time, the fibroblasts are vital to healing the wound, so it’s important that they move into the area as quickly and completely as possible.

The problem is that the fibroblasts move in from the edges of the wound. As they advance, they move in a formation that’s a bit like a line of soldiers all marching in step. This works fine when the wound is a cut or shaped with straight edges because the advancing lines of fibroblasts from the various edges can march toward one another and meet flat, thus enabling the wound to heal quickly and completely. However, if the wound is roundish, then the advancing lines form a contracting circle. The fibroblasts crowd in on one another and jam up, so the healing is slow and imperfect. Also, if a wound is very large, such as when a patch of skin has been lost or damaged, the fibroblasts take a very long time to reach the center, which increases the chances of infection and scarring.

What the new plaster from the ETH team does is to speed up and make easier the migration of the fibroblasts into the wound. It does this through a special silicone plastic called Polydimethylsiloxane (PDMS), which doesn’t stick to wounds or to fibroblasts, so it can be removed easily without causing damage. The team used a soft lithography technique to embed parallel grooves in the plastic one micrometre wide and 0.6 micrometres deep. These grooves are not only too small to be seen with the eye, they are also smaller than the fibroblasts. However, they are large are enough to hamper the movement of the fibroblasts unless they follow the grooves. Since fibroblasts prefer to follow the path of least resistance, the grooved plaster becomes a sort of highway that guides the fibroblasts into the wound without bumping into each other. This way, they can spread over the entire wound quickly and promote a much faster healing.

Electron microscope image of ETH's silicone wound-healing plaster (Image: A. Marmaras / ETH Zurich)

So far, this new healing plaster is still in the laboratory phase. The “wounds” that it’s healed have been single layer tissue cultures, but the results have been very promising and the team hopes to soon go on to the next phase, which is animal and human testing to see how the plaster fares against more complex tissues.

The researchers see the main application of the plaster in treating burns, where healing and scarring are major issues.

Source: ETH Life

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