How can characterisation of the morphology and roughness of pharmaceutical granules using atomic force microscopy result in
improved granulation and pharmaceutical processing?
The flow properties of a powder can be influenced by the shape and roughness of the particles. A thorough knowledge of the
surface properties of excipient powders and the resulting granules will enable process parameters to be optimised. It will
also be helpful when modifying process methods, for example, a switch from wet granulation to dry granulation or direct compression.
Rough particles also have a greater surface area, allowing the absorption of more moisture. This may be desirable or undesirable,
depending on the application of the powder.
How might AFM be applied to the measurement of dynamic rheological properties, to benefit characterisation of a pharmaceutical
formulation?
AFM can be used in liquids, and there have been several studies of suspensions and colloids in which AFM has been used to
measure interactions between particles, as well as between the particles and fluid. There have also been studies that have
examined the formation of bubbles in liquids and their interaction with particles in the suspension. AFM could be used to
complement other techniques in optimising the design and manufacture of pharmaceutical suspensions, creams and lotions. In
addition to the properties of the drug delivery systems, AFM can be used to characterise the areas to which the formulations
are applied, such as skin, hair or dressing.
Are there any knowledge or technological gaps in the pharma industry that prevent AFM from being fully exploited?
The techniques and research strategies for using AFM in the pharma industry are now well established: examining the properties
of powdered excipients, colloids, pulmonary drug delivery, microbiological systems and implants. The volume of data is still
limited, however, and has not kept pace with the new formulations. As manufacturing companies modify their practices to accommodate
the new quality by design approach, AFM will have a part to play. Along with bulk powder techniques, knowledge of the variation
of surface properties will enable optimisation of solid-dosage manufacturing processes.
Mark Leaper is Senior Lecturer, School of Pharmacy,De MontfortUniversity (UK).
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