At the molecular level, most solid materials can be described as either crystals or glasses, the difference lying in the degree of internal organization of their constituent molecules. Researchers focused on a method which would encourage this internal molecular arrangement to be more organised.
Using a technique known as vapour deposition, the researchers built up glass layer by layer, which allowed the molecules to arrange themselves in a more orderly fashion. This resulted in increased stability and strength of the glass.
The instability of conventional glasses poses problems for amorphous pharmaceuticals. Conventional glasses tend to be less thermodynamically stable, as the molecules slowly abandon their higher energy elevations in favour of a low-energy crystalline arrangement, which changes the structural nature of the material. This is clearly an issue with regards to amorphous pharmaceuticals, as any internal structural alterations can change the properties of the drug.
Lead author of the study, Professor Mark Ediger, and his team believe that there is scope for their new technique to be applied to pharmaceutical compounds, in a bid to tackle this problem.
While compounds that are too molecularly unstable can degrade over time and undermine the drug's effectiveness, those that are too stable may be insoluble in the human body. By applying the new techniques as a method of controlling the stability and solubility of molecular glass, the team hope it may be possible to develop previously unusable drug compounds. Stable glass films could also be applied to extend the shelf-life of existing medical tools such as off-the-shelf blood and pregnancy testing kits.
"This increased stability expands the applications of amorphous pharmaceuticals," said Professor Lian Yu of the Pharmaceutical Sciences Division at the University of Wisconsin-Madison.
These non-crystalline forms, or amorphous pharmaceuticals, have been the subject of recent research in an attempt to enhance drug delivery and enable active therapeutic ingredients to reach targets inside the body. The research group has already successfully made stable glass with indomethacin, an anti-inflammatory. Indomethacin is used as a model system for studying amorphous drugs as it is fairly well understood and there is a significant body of information on which researchers can draw.
"The principle is general enough that it should be applicable not only to indomethacin,"Professor Yu told In-PharmaTechnologist.
"The phenomenon has been established; the next challenge might be more of an engineering challenge to scale up to pharmaceutical requirements."
Professor Yu and his colleagues are optimistic regarding future applications of these 'super-stable glasses', and are currently studying another potential drug, nifedipine, a poorly soluble calcium channel blocker.