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Title: Nuclear magnetic resonance studies of controlled drug release devices
Author: Perkins, Emily Louise
ISNI:       0000 0004 2683 808X
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2009
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In this work the techniques of NMR cryoporometry and cryodiffusometry are developed and applied to the investigation of porous systems for controlled drug release devices. Both sol-gel silicas and PLGA microspheres are investigated. The cryoporometry method is developed from that described in the literature and a robust method for pore size determination is established. Cryoporometry investigations on sol-gel silicas are compared to data from other more traditional and better understood porosimetry techniques in order to determine the cause of hysteresis seen between the freezing and thawing process of an imbibed liquid. The causes of hysteresis are determined to be both pore shape and pore network related. Percolation theory is applied to the freezing process within the sol gel silica and shows that the freezing process occurs as a freezing front that begins in the bulk and progresses in toward the centre of the pellet. Thus, the freezing curve can be used to determine the size of the pore entrances. NMR diffusometry techniques are applied to PLGA microspheres at room temperature and during the freeze-thaw process in cryoporometry, a technique called cryodiffusometry. These investigations provide information about the micrometer scale pores within the microspheres and also the characteristics of the polymer matrix structure at the nanometer scale. Time-resolved cryodiffusometry studies of the PLGA microspheres show changes in the polymer matrix nominal pore neck and pore body sizes, tortuosity, and connectivity. These changes can be qualitatively discussed in terms of the drug release mechanism. The development of this technique and its application to nanometer scale porosity evolution in polymer matrices is novel and has advanced the understanding of the freezing process of a liquid imbibed in a porous solid.
Supervisor: Rigby, Sean ; Edler, Karen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available