In the future, parents may apply a little electricity to their kids' scraped knees. Find out why in this Science Update.
Charging up the healing process. I'm Bob Hirshon and this is Science Update.
A little electricity may dramatically speed up the healing of skin wounds. This according to work led by Min Zhao and Colin McCaig of the University of Aberdeen School of Medicine in Scotland. McCaig says it's long been known that wounds naturally generate weak electric currents, and that our cells sense and follow these currents to rebuild. In lab and animal studies, his team found that enhancing these electric fields made wounds heal up to 50 percent faster. In the future, he says doctors could achieve this with topical drugs.
So you could imagine using them in an ointment or in solutions, or whatever, just as a dressing to wounds.
Another strategy would be to apply electricity directly, perhaps with a specialized bandage that generates its own electric field. I'm Bob Hirshon, for AAAS, the science society.
Making Sense of the Research
Sometimes, scientific innovation depends on breakthrough discoveries that radically change what we know about the world. But just as often, if not more so, scientists simply come up with a new way of using old knowledge.
That's the case here. As the report mentions, scientists already knew that skin wounds generate weak electric fields. That's not so surprising when you consider that our bodies use electricity all the time. For example, our entire nervous system works on electricity: electrical impulses carry signals from our brain to our fingers to pick something up. If that object is too hot, the sensory nerves in our fingers send an electrical impulse back, which triggers yet another electrical impulse to let go.
Aside from these single-cell electrical signals, our body also has electrical gradients, which are differences in electrical charge across a surface. One of these gradients occurs across our skin. McCaig explains that if you compare the electrical charge of the outside world to the electrical charge just under our skin, there's a difference of about 100 millivolts. That's because the skin naturally absorbs positive sodium ions and secretes negative chloride ions, causing the area under the skin to be more positively charged than the area just above it.
As long as your skin is intact, that voltage difference holds fairly steadily, although it varies somewhat with stress, emotion, and other changes in the activity of our nervous system. However, if the skin is cut, there's nothing to hold back the electric current. So, because electric current flows from positive to negative, the positive charge flows out of your body, perpendicular to the surface of your skin.
Now the voltage across your skin at the site of the wound is zero, but the voltage difference across the rest of your skin is still 100 millivolts. That voltage difference lasts for hours or even days, until the skin closes itself. It turns out that the voltage difference triggers several responses in the nearby, healthy skin cells. It causes the cells to divide and move more easily, facilitating healing. Not only that, it tells those cells which direction to move in so that they can start repairing the damaged tissue.
McCaig and his colleagues hypothesized that if an electrical gradient helps wounds to heal, then a stronger electrical gradient might help them heal faster. And in fact, that's exactly what they found. You heard that in the future, doctors could boost the electrical signal by either zapping the wound site with electrodes, or applying an ointment. The ointment would increase the electrical gradient by making the skin transport charged ions more efficiently. And it's not so absurd that either of these abilities could eventually be built into an ordinary bandage. Of course, there are limits to how strong this electrical field should be; otherwise the skin would be fried, not healed.
Now try and answer these questions:
- Why is there a voltage difference across our skin?
- How does a wound change this voltage difference?
- How does this change affect the healing process?
- What would happen if you reduced or eliminated the voltage difference around the site of a wound? What would happen if you reversed it—in other words, swapped positive charges for negative?
- What types of wounds do you think this would work best for?
You may want to check out the September 29, 2006, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: a good time to be a dinosaur hunter, how your personality affects your health, electricity could heal wounds, plastics made from DNA, and the fastest body parts in the world.
Tissues of Life, from the Science Museum of Minnesota, contains many interactive features about the body's tissues, including epithelial tissue, which makes up the skin.
To learn about other unusual techniques for facilitating skin healing, see the National Geographic News articles on Spray-On Skin Cells and Maggot Medicine.