Levitation used to improve drug delivery

Posted by Emma Woollacott

Scientists at the US Department of Energy's Argonne National Laboratory are levitating individual droplets of different pharmaceuticals, aiming to improve the drug development process.

At the molecular level, pharmaceutical structures fall into one of two categories: amorphous or crystalline. Amorphous drugs are usually more efficiently taken up by the body than their crystalline cousins, as they're more highly soluble and require a lower dose.

"One of the biggest challenges when it comes to drug development is in reducing the amount of the drug needed to attain the therapeutic benefit, whatever it is," says Argonne X-ray physicist Chris Benmore, who led the study.

But it isn't easy getting pharmaceuticals from solution into an amorphous state. If the solution evaporates while in contact with part of a vessel, it's far more likely to solidify in its crystalline form.

However, it can be done with levitation, or 'containerless processing'. The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a a standing wave.

At certain points along this standing wave, known as nodes, there's no net transfer of energy at all. Because the acoustic pressure from the sound waves is enough to cancel the effect of gravity, light objects can levitate here.

Although the technique only works on small quantities of a drug, it's a powerful analytical tool for understanding the conditions that make for the best amorphous preparation, say the team.

They've already investigated more than a dozen different pharmaceuticals, and the laboratory's Technology Development & Commercialization Division is currently pursuing a patent for the method.