Pain-Free Injections Possible With Laser-Powered 'Needle'
Work is under way to create low-cost injectors for clinical use (Sept. 13)
From annual flu shots to childhood immunizations, needle injections are among the least popular staples of medical care. Although various techniques have been developed in hopes of taking the “ouch” out of injections, hypodermic needles are still the first choice for ease-of-use, precision, and control.
However, according to a September 13 announcement from the Optical Society of America (OSA), a new laser-based system that blasts microscopic jets of drugs into the skin could soon make getting a shot as painless as being hit with a puff of air.
The system uses an Er:YAG (erbium-doped yttrium aluminum garnet) laser to propel a tiny, precise stream of medicine with just the right amount of force. This type of laser is commonly used by dermatologists, particularly for facial esthetic treatments, explains Dr. Jack Yoh, who developed the device along with his graduate students.
Yoh and his team describe the injector in a paper published in OSA’s journal Optics Letters.
The laser is combined with a small adaptor that contains the drug to be delivered, in liquid form, plus a chamber containing water that acts as a “driving” fluid. A flexible membrane separates the two liquids. Each laser pulse, which lasts just 250 millionths of a second, generates a vapor bubble inside the driving fluid. The pressure of that bubble puts elastic strain on the membrane, causing the drug to be forcefully ejected from a miniature nozzle in a narrow jet a mere 150 millionths of a meter (150 micrometers) in diameter — just a little larger than the width of a human hair.
Tests on guinea pig skin show that the drug-laden jet can penetrate up to several millimeters beneath the skin surface, with no damage to the tissue. Because of the narrowness and quickness of the jet, it should cause little or no pain, Yoh says. Injection with the jet is aimed at the epidermal layer, which is located closer to the skin surface, at a depth of about 500 micrometers. This region of the skin has no nerve endings, so the method should be completely pain-free, according to Yoh.
Although other research groups have developed similar injectors, they are mechanically driven, using piston-like devices to force drugs into the skin, which gives less control over the jet strength and the drug dosage, Yoh says. In contrast, the laser-driven microjet injector can precisely control the dose and the depth of drug penetration underneath the skin.
Yoh is now working with a company to produce low-cost replaceable injectors for clinical use.
For more information, visit the Optical Society of America Web site.