Scientists at the US Department of Energy’s Argonne National Laboratory have discovered a way to use sound waves to levitate individual droplets of pharmaceutical solutions, producing physical properties at the molecular level that may aid drug delivery.
At the molecular level, pharmaceutical structures fall into one of two categories: amorphous or crystalline. In many cases, amorphous drugs are more efficiently taken up by the body than their crystalline counterparts because they are more soluble with a higher bioavailability. Thus a lower dose can produce the desired effect.
‘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,’ said Argonne X-ray physicist Chris Benmore, who led the study.
‘Most drugs on the market are crystalline – they don’t get fully absorbed by the body and thus we aren’t getting the most efficient use out of them,’ added Yash Vaishnav, Argonne senior manager for IP Development and Commercialisation. Getting pharmaceuticals from solution into an amorphous state, however, is no easy task. If the solution evaporates while it is in contact with part of a vessel, it is far more likely to solidify in its crystalline form.
To avoid this problem, Benmore needed to find a way to evaporate a solution without it touching anything. Because liquids conform to the shape of their containers, this was a nearly impossible requirement. Benmore turned to an acoustic levitator, a piece of equipment originally developed for NASA to simulate microgravity conditions.
Levitation or ‘containerless processing’ can form pristine samples that can be probed in situ with the high-energy X-ray beam at Argonne’s Advanced Photon Source. ‘This allows ‘amorphisation’ of the drug to be studied while it is being processed,’ said Rick Weber, who works on the project team at the synchrotron.
The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22kHz and precisely aligned such that they cancel the effect of gravity, and allow light objects to levitate.
Although only small quantities of a drug can currently be ‘amorphised’, it is a powerful analytical tool. Argonne researchers have already investigated several pharmaceuticals and have now teamed up with scientists at Purdue University and Arizona State University to identify the drugs on which the levitation process could have the strongest impact.