Eftychios Hadjittofis

Research area: Solid Surface Characterisation

Research sponsor: EPSRC DTA and AbbVie

Project overview

Surface Characterisation of Organic Solids

The effect of the particle processing impacts powder surface properties. For example, micronisation/milling may induce surface amorphisation or the exposure of different crystalline facets, which will result in dramatic changes in the surface properties, affecting powder properties and performance. The physico-chemical properties of solids are important for the determination of a wide range of particle behaviour such as dissolution rates, aggregation/de-aggregation, crystal growth mechanisms, and colloidal stability.

This project aimed at developing predictive capability for determining changes in crystalline solid properties (eg polymorphs, size and shape) during agitated drying. The impact of particle defects will also be investigated.

This proposed study includes the use of the following approaches:
1. Finite Dilution Inverse Gas Chromatography (FD-IGC).
2. Quartz Crystal Microbalance (QCM) for Particle Adhesion.
3. Detailed Physico-chemical Characterisation of Pharmaceutical Powders.
4. Development of an Experimental Approach to Determine Powder mixing.

The key hypothesis in this proposed programme of work is that the surface properties of organic solids is anisotropic, and impacts on particle-particle interactions (including API-excipients) during powder handling and processing. This proposed research would greatly aid the rationale of product development and formulation, based on a detailed description of powder properties.

References:
1. J. W. Kwek, M. Jeyabalasingam, W. K. Ng, J. Y. Y. Heng and R. B. H. Tan, “Comparative study of the triboelectric charging behaviour of powders using a nonintrusive approach”, Ind. Eng. Chem. Res. (2012), 51, 16488-16494.
2. R. Ho and J. Y. Y. Heng, “A Review of Inverse Cas Chromatography and its Development as a Tool to Characterize Anisotropic Surface Properties of Pharmaceutical Solids”, KONA Powder and Particle Journal (2013), 30, 164-180.
3. G. D. Wang, F. P. Mallet, F. Ricard and J. Y. Y. Heng, “Pharmaceutical nanocrystals”, Curr. Op. Chem. Eng. (2012), 1, 102-107.
4. F. Thielmann, D. J. Burnett and J. Y. Y. Heng, “Determination of the surface energy distributions of different processed lactose”, Drug Dev. Ind. Pharm. (2007), 33 (11), 1240-1253.
5. J. Y. Y. Heng, A. Bismarck, A. F. Lee, K. Wilson and D. R. Williams, “Anisotropic Wettability of Macroscopic Form I Paracetamol Crystals”, Langmuir (2006), 22 (6), 2760-2769.