It is ironic that the process used to discover pharmaceutical drug targets is the same one that decreases the actual efficacy of those drugs once ingested. If you remember from basic chemistry, there are compounds that exist in highly ordered crystalline states and those that remain in amorphous form. The discovery of drug targets has often been accomplished through X-ray crystallography, which requires a sample (for example, of a defective enzyme linked to cancer or high cholesterol) to be crystallized so that the diffraction patterns can be made sense of. Scientists may spend years trying to crystallize one molecule or compound so that they can identify regions that, for example, may be blocked by pharmaceuticals.
However, when it comes to the molecular arrangement of those pharmaceuticals, crystallization actually decreases their bioavailability and solubility. Thus, it may be better for these drugs to be in amorphous form. (For a good, short summary of crystalline versus amorphous drugs, check out this slideshow). This is easier said than done because the drug preparation process is unforgiving and often leads to unintended crystallization, which is exacerbated when the solution evaporates when it is in contact with the holding vessel.
Researchers at the U.S. Department of Energy’s Argonne National Laboratory are applying a NASA technology – acoustic levitation – to this problem in an effort to improve the drug development process. Their answer: get rid of the vessel. As explained in Argonne’s press release:
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 phenomenon known as a standing wave.
At certain points along a standing wave, known as nodes, there is no net transfer of energy at all. Because the acoustic pressure from the sound waves is sufficient to cancel the effect of gravity, light objects are able to levitate when placed at the nodes.
Although only small quantities of a drug can currently be “amorphized” using this technique, it remains a powerful analytical tool for understanding the conditions that make for the best amorphous preparation…
The labs also released this video demonstrating their levitating droplet approach:
It will be interesting to see how Argonne, or peer groups of researchers, improve upon this process and make it scalable so that larger quantities of drugs may be produced. Currently the researchers are determining which drugs may benefit the most from this new production process, especially because amorphous compounds are generally less stable and degrade faster than their crystalline counterparts.
For more information, you may read the group’s paper in the European Biophysics Journal: Acoustic levitation: recent developments and emerging opportunities in biomaterials research
Argonne National Laboratory: No magic show: Real-world levitation to inspire better pharmaceuticals