Liquid Phase Electron Microscopy as an Innovative Tool to Probe Pharmaceutical Crystallisation

Liquid Phase Electron Microscopy (LPEM) allows visualisation of nanoscale events suspended in their native liquid environment, hermetically sealed from the high vacuum environment of the TEM. Since the inception of this technique, LPEM coupled with state-of-the-art detectors has revealed new fundamental information e.g. nanoparticle growth processes, electrochemical dynamics, and catalysis events.<br/>In the pharmaceutical industry, a thorough understanding of an API crystallisation process and propensity for uncontrolled polymorph transition is required to fully characterise an API and assess the most beneficial crystal structure for treatment that will treat the ailment through optimum bioavailability and dosage. Although the aforementioned is a fundamental understanding for drug discovery, we can utilise LPEM to observe in situ the nucleation of an API on the nanoscale to discover the poorly understood events of the preceding and intermediate stages that lead to the formation of API crystals.<br/>We have previously reported that LPEM allows nucleation to occur at 125x lower in concentration than that expected for supersaturation for a vital anti-inflammatory drug, flufenamic acid. By using LPEM, we can probe the nucleation and subsequent crystallisation process by exploiting the induced crystallisation through radiolysis of the solvent. The cascading events of solute-radiolysis products are believed to be the result of crystallisation in these unique conditions at such low concentrations where crystallisation should not be possible. A central question remains of how exactly this occurs.<br/>Establishing a combined and deep understanding of the radiation chemistry and crystallisation mechanisms commanding the formation of these life-saving organic molecular crystals will lead to a more thorough analysis of how to harvest more beneficial polymorphs of existing drugs.<br/>Herein, I present the use of LPEM to reveal fundamental and somewhat surprising observations of the nucleation and growth of the Active Pharmaceutical Ingredient (API), Flufenamic acid in its native growth solution.