Kicking against the pricks

Seen the needle and the damage done? Get ready for a more 'constructive' approach to injections � microscission

By Graham Furness

Needle-shy patients may at last be able to face their doctor without fear. It's good news for those with this paralyzing phobia � estimated to affect as much as 10% of the population � and patients requiring frequent injections. Researchers at Harvard-MIT Division of Health Sciences and Technology have created a device that does a syringe's job without pain or danger of needle injuries and infections.

The technique, known as microscission, owes its inspiration to the sandblasters used to remove dirt and pollution from urban buildings. Here's how it works: a mask made from Teflon or polyimide and pierced with one to four holes is placed over the skin of the inner wrist. A gun fixed to the mask fires a high-speed blast of gas containing tiny crystals of aluminium oxide, a material commonly used in sandpaper. Only the skin that's exposed through the holes is 'sandblasted' by the microscission gun. The particles remove the surface layer of skin, exposing tiny holes or microconduits in the lower skin layers.

PAINLESS DELIVERY
Researchers first tested the efficiency of the device to deliver medications using a local anesthetic � a relatively low-risk task considering that titration is less important with these drugs. Once the microconduits had been made in the skin of volunteers, a pad soaked with lidocaine was applied. Within three minutes the patch of skin was anesthetized. The same pad took 90 minutes to work on normal, 'unmicroscissed' skin.

Their results show that the syringe's days could be numbered � the volunteers reported that the sensation they felt was like a gentle stream of air against the skin. Another benefit is the fact that no foreign bodies were detected after healing took place.

If the device is set to make deeper microconduits, it produces some minor spotting of blood on the skin. This seemed to reduce the effectiveness of microscission as a drug delivery method. The researchers noted, in their article published April 19 in the online journal BMC Medicine, that "the onset of anesthesia takes longer in microconduits deep enough to yield blood than in shallower, non-blood producing microconduits. Possibly the blood outflow impedes inflow of the externally applied lidocaine, or the clotting blood partially obstructs the microconduit."

The technique, which is being licensed to a pharmaceutical company and is likely to be available for commercial use within a few years, could offer a boon to doctors who have patients intolerant to injections. "One of the skin's fundamental functions is to act as a barrier to the outside world," explained lead author Dr James Weaver. "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's always a risk of bruising."

SYRINGE-LESS SAMPLES
An unexpected bonus of the device is the possibility of replacing the syringe's other prime function: taking blood samples. The deeper, blood-producing microconduits produce an ideal quantity of blood for a commercial blood glucose monitoring system.

The microconduits are invisible to the naked eye at the time of injection, then develop into a small red spot which fades over a few days. Through-skin microscopy showed no sign of foreign bodies remaining in the skin after the procedure.

It's most unlikely that diabetics will be able to carry their own personal skin-sandblaster around anytime soon, and even family doctors may not be doing any 'microscissioning' for a while yet. But for busy hospitals that spend big money on disposable needles and continually worry about accidental jabs and their potentially deadly consequences, the technique could well prove to be a godsend.