Are needles on the way out? Two new methods for administering drugs to the skin have been in the news within a day of each other.

In a paper published today in Optics Letters a team from Seoul National University in South Korea demonstrates how to use a small laser assembly to force tiny jets of drugs into skin with less pain and more control than a needle.

The system includes two back-to-back chambers separated by a flexible membrane, one containing water behind another of the liquid drug to be delivered under the skin. The attached laser pulses once, for 250 millionths of a second, and a steam bubble forms in the water chamber, which presses on the membrane and forces the drug out of the other chamber. A hair-thin jet of the drug then shoots out the attached nozzle and penetrates the surface of the skin to a precisely calibrated depth, causing little or no pain. The laser never touches the skin—only the jet of liquid that the air bubble forces out. Multiple pulses of the laser up the dosage.

The creators had tried this with earlier prototypes, but the trick this time was to use the right laser wavelength to create the perfect-size bubble of steam. In previous tries the bubble had been too small and unstable, and the resulting jet didn't reliably penetrate the skin. Right now the device is best suited for small doses of drugs at multiple sites, but lead researcher Jack Yoh, professor of mechanical and aerospace engineering, says in a statement that further development could make the laser suitable for children's vaccinations en masse. He is currently working with a private company to make affordable, replaceable injectors that might soon be available overseas, but FDA approval would likely slow that process in the U.S.

Meanwhile, MIT scientists have developed an ultrasound method that they say "could pave the way for noninvasive drug delivery or needle-free vaccinations." They say their device could be used for topical drugs like steroids, proteins like insulin, or vaccines. The team of chemical and mechanical engineers published a study, funded by the National Institutes of Health, set to appear in the Journal of Controlled Release.

When ultrasonic waves move through a fluid such as a topical medication, they (like lasers) can create bubbles that zoom around at high speeds. When the bubbles get bigger, they pop, and surrounding liquid rushes in to fill the space. These little jets of fluid brush the skin, making microscopic scratches, which gives the drug access to underlying skin cells.

The microjets from the collapsed bubbles "act like little hammers hitting the skin, creating temporary pathways across the outermost barrier of the skin, the stratum corneum (SC), through which drugs can more readily penetrate and reach the blood capillaries," Daniel Blankschtein, professor of chemical engineering and one of the senior authors, tells PM.

High frequency ultrasound makes the bubbles and keeps them from moving around too much, while low frequency ultrasound is what makes the bubbles big enough to pop. So MIT researchers combined the two frequencies and tested it out on pig skin. Drug delivery across the scratched patch was better compared with patches of skin treated with traditional ultrasound at only one frequency, and the results lasted up to 24 hours, which would be useful for diabetics self-administering insulin several times a day. The authors also think ultrasound could be used for painless vaccination, which could be of particular significance in developing countries, where needles and people trained to use them can be in short supply—provided ultrasound machines could be made more affordable.

The group is now developing a handheld ultrasound device, which would need to be tested on animals and on humans before the FDA would approve it.

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