Controlling crystals for more reliable drugs

Sometimes, compounds crystallize in unexpected ways. This is a problem for drug manufacturers, who need to create consistent products. Scientists are working to understand why substances take on different crystal forms, called polymorphs, under different conditions. Recently, they’ve shown that impurities can affect the relative stability of those forms.

Video credits are available on YouTube.

Source Article

“Thermodynamic Stability Transitions and Coexistence of Two Polymorphs via Crystalline Solid Solutions: The T-X Phase Diagram of Salicylic Acid and 2,3-Dihydroxybenzoic Acid”
Crystal Growth & Design
Corresponding author: Fredrik L. Nordstrom, Ph.D.

Transcript

Crystals can be … frustrating. And growing the wrong crystals can be costly. 

Some compounds can crystallize in multiple forms called polymorphs. Polymorphs are important in the pharmaceutical industry. When scientists develop a new drug, they get approval for one polymorph. If a batch of the drug crystallizes as a different polymorph, that batch can’t be used as medicine. So scientists are studying what makes one polymorph more likely to form than another. 

For example, this compound usually crystallizes with its molecules in parallel sheets. But when an impurity with a similar structure is in the mix, it makes a different crystal form with the molecules interacting at right angles. 

Here’s a mixture of those two compounds. As scientists apply heat, the crystals change shape. That’s because the mixture transitions from one polymorph to another at high temperature. Learning to control these changes will help scientists make more reliable drugs.