The importance of surface energetics of powders for drug delivery and the establishment of inverse gas chromatography

Powders are complex systems with more than one value for surface energy. The presence of different faces, defects, physical forms and impurities will alter the surface properties. There are few good ways to measure powder surface energies, with vapour sorption, especially inverse gas chromatography...

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Bibliographic Details
Published in:Advanced drug delivery reviews 2007-12, Vol.59 (14), p.1474-1479
Main Authors: Buckton, Graham, Gill, Hardyal
Format: Article
Language:English
Subjects:
Amorphous forms
Batch variability
Chemical Phenomena
Chemistry, Pharmaceutical
Chemistry, Physical
Chromatography, Gas
Contact angle
Drug Delivery Systems
Glass transition
Humidity
Inverse gas chromatography
Powders - chemistry
Surface energy
Surface Properties
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Summary:Powders are complex systems with more than one value for surface energy. The presence of different faces, defects, physical forms and impurities will alter the surface properties. There are few good ways to measure powder surface energies, with vapour sorption, especially inverse gas chromatography (IGC) being a logical choice. The significance of surface energy is reviewed briefly, as is the difference between contact angle and IGC data. The utility of IGC for studies of batch to batch variability and some issues relating to finding a suitable number to describe a complex range of surface energies are discussed. The utility of IGC in studies of the amorphous state is shown, where there is value in being able to monitor molecular mobility thresholds, glass transition, collapse and crystallisation, as well as relaxation and its impact on surface energy. The conclusion is that the complexity of powders means that scientists should not expect simple correlations between measurements and performance, but that correlations are likely to be there if the correct data are recorded in the most appropriate way.
ISSN:0169-409X
1872-8294
DOI:10.1016/j.addr.2007.06.017