Biodegradability of sol–gel silica microparticles for drug delivery
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Abstract
The biodegradability of porous sol–gel silica microparticles in physiological buffers has been investigated using a USP4 flow-through dissolution tester. In the open configuration, which most closely models in-vivo conditions, the particles dissolved rapidly at pH 7.4, with a rate dependent on the surface area and media flow rate. In the closed configuration, the fastest dissolving 4 mg silica sample was almost completely dissolved in 100 mL of buffer after 36 h. The initial dissolution rates appeared relatively linear but dropped off as dissolved SiO2 concentrations approached 20–25 ppm. Addition of serum proteins acted to slow dissolution by 20–30%, suggesting a slower degradation in vivo. Silica microparticles administered for controlled release drug delivery would therefore be expected to be eliminated relatively rapidly from the body, depending on the sample size and local fluid flow conditions.
Keywords
Biodegradability Encapsulation Drug delivery Dissolution MicroparticlesNotes
Acknowledgements
The authors thank David Cassidy and Elizabeth Drabarek of the Australian Nuclear Science and Technology Organisation for sample characterisation, and Dr Sam Knight, of CeramiSphere, for advice concerning the dissolution tests. We are grateful to Eka Chemicals for the gift of Bindzil 30/360 colloidal silica.
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