Microscission blasts drugs through skin

Nightmares of doctors or dentists with oversized hypodermic needles could soon be a thing of the past. A new painless way of delivering drugs through the skin is described in the journal BMC Medicine this week – and needles are not involved.

The technique, called microscission, uses a stream of gas to bombard small areas of the skin with tiny crystals of inert aluminium oxide. The sharp particles remove the rough surface-layer of the skin, and create tiny holes, known as microconduits, in the underlying layers of the skin. The crystals and loosened skin are taken away with the gas flow. The whole process takes less than 20 seconds.

Volunteers reported that the sensation they felt was like a gentle stream of air against the skin – much less painful than being pricked by a needle.

The microconduits formed are invisible to the naked eye, measuring under ¼mm in diameter and between 1/20mm and 1/5mm in depth. The width of the microconduits is defined by the size of holes punched in a mask made from polyimide film, which is placed over the skin.

The researchers, from the Harvard-MIT Division of Health Sciences and Technology, tested the technique by seeing whether they could administer a local anaesthetic to volunteers through the microconduits. After using microscission to create four microconduits within a small area, the researchers applied a pad soaked with the anaesthetic, lidocaine, to the region. Within two minutes the patch of skin was anaesthetised; the loss of feeling that the volunteers experienced demonstrated that the drug had been successfully delivered.

The research team led by Dr James Weaver observed that, "the onset of anaesthesia takes longer in microconduits deep enough to yield blood than in shallower, non-blood producing microcondits. Possibly the blood outflow impedes inflow of the externally-applied lidocaine, or the clotting blood partially obstructs the microconduit."

Deeper microconduits that yield spots of blood would be useful for patients with diabetes, though. These patients have to regularly check the glucose level in their blood. Currently they must suffer the pain of pricking their finger with a needle so that a small amount of blood can be used to test for glucose. Microscission would provide a new and painless way to do this.

One of the skin's fundamental functions is to act as a barrier to the outside world. Therefore, finding ways to deliver drugs through the skin has always been a major challenge. To date, only the hypodermic needle has met this need. However, needles are not ideal for patients as piercing the skin is often painful and there is always a risk of bruising.

Microscission could be set to revolutionise how blood is taken and drugs are delivered through the skin.

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