Synthesis and Characterization of Hydroxyapatite Nanocrystals in Ordinary Solvents, Simulated Body Fluid and Collagen Matrix
| Autor: | Po-Yu Cheng, 鄭博宇 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 A full understanding of the multiscale structure of the bone is crucial for developing efficient drugs or therapies for many bone diseases and disorders. This goal has not been fulfilled yet because of the complexities involved in this type of living inorganic-organic hybrid systems. Some less challenging but still very important problems are the sizes, morphologies and surface characteristics of the hydroxyapatite nanocrystals (HApNC) in the bone. In this work, we synthesize a series of HApNCs under different conditions (changing pH, ions, simulated body fluid, collagen) and characterize them with various analytical methods, particularly, solid state NMR. It is demonstrated that solid state NMR is a powerful method for studying this type of systems. The 1H and 31P solid state MAS NMR spectra of HApNCs prepared in buffers at different temperatures (which can mimic the effect of fever on bone nanocrystals). Both the chemical shift and lineshape of the 31P spectra do not show appreciable change (which means phosphate is not affected by the preparation temperature) but the 1H spectra display clear temperature effect: the surface water signal moves upfield as temperature increases, indicating that the environment of the surface water becomes less acidic as temperature increases. This suggests that the HApNC surfaces are sensitive to preparation temperature (but the details about the surface properties and temperature requires more investigation). The structural water signal in the 1H spectra becomes weaker as temperature increases, which implies that structural water is driven out as temperature is raised during preparation. The 1H and 31P solid state NMR spectra of HApNCs prepared in buffers with different pH values, demonstrating significant pH effect, e.g., both 1H (of surface water) and 31P peaks shift to upfield as pH increases. The relationship between chemical shift, lineshape of solid state NMR spectra and the size, morphology and surface properties of HApNCs will be analyzed and the implications of these results to bone structure and diseases will be discussed. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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