Porous Amorphous Calcium Carbonate and Phosphate : Synthesis and Application

Abstract: The synthesis of porous amorphous calcium carbonate (ACC) and porous amorphous calcium phosphate (ACP) was developed in this thesis. Porous ACC with specific Brunauer–Emmett–Teller (BET) surface area of >350 m2/g was synthesized using a surfactant free approach. The high surface area of porous ACC was related to its nanostructure. Porous ACC was constructed with aggregated ACC nanoparticles that were less than 10 nm in diameter. The porosity and stability of porous ACC could be enhanced by introducing additives in the synthesis steps. The use of additives could also be used to control the crystallization of ACC to form vaterite particles with controllable morphologies. Porous ACC was tested as a drug carrier for two poorly soluble drugs (itraconazole and celecoxib). The porous ACC carrier was able to stabilize these drugs in their amorphous forms and enhance their release rate significantly when compared with the crystalline drug. Furthermore, porous ACC could also be used as a precursor/template for the synthesis of porous carbon. A porous carbon adsorbent with high uptake and high selectivity for greenhouse gases was produced. Porous ACP with a specific BET surface area of >400 m2/g was obtained by introducing phosphoric acid to the ACC suspension obtained during the synthesis of porous ACC. Similar to porous ACC, porous ACP was constructed of aggregated nanoparticles. ACP was found to be stable in ambient conditions for over 12 months and the stability could also be tailored by adjusting its composition. Porous ACP was cytocompatible and an effective drug carrier for alendronate - a bisphosphate drug for treatment of osteoporosis. The development of porous ACC and porous ACP as functional porous materials is summarized in this thesis.