Template Regulating Synthesis And The Formation Mechanism Of Mesostructured Nanosized Apatite

Mesostructured hydroxyapatite (HAP) nanoparticles (NPs) were prepared using various templates. The reaction temperature, the additive, the variety and the concentration of templates were proposed to regulate the pore shape, the pore size and the morphology of the mesostructured HAP, and meanwhile to improve the the specific surface area and the pore volume. And the mesostructured HAP NPs were further fuctionalized with magnetism and luminescence, to endow them with biotargeting and biomarking functions when applied in drug carriers. The morpgolies and microstructures of the obtained mesostrured HAP were analysed by X-ray diffraction (XRD), small angle X-ray diffraction (SAXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and nitrogen absorption, etc. The regulation mechanmisms of mesostrutured HAP by various templates were fully disscussed based on the self-assemly behaviors of surfactants. Furthermore, the functions of the doped mesostructured HAP NPs, drug adsorption property and in-vitro release kinetics for mesostructured HAP NPs were also investigated.All the as-prepared precursors in-situ templated by dodecyl, n-octyl, n-pentyl, and ethyl phosphates had ordered nanostructures. But only the ethyl phosphate templated HAP sustained with an orderly hexagonal nanostructure at 400°C, possessing a specific surface area of 42m2/g and a pore volume of 0.0644cm3/g. With Tween-60 as the cosurfactant, the ethyl phosphate in-situ templated HAP had a large amount of 4nm worm-like mesopores which still thermally stable at 650oC.The aqueous behavios of Pluronic P123 regulated by the addition of P123, the reaction temperature and the additive were utilized to mediate the biomimetic synthesis of hydroxyapatite (HAP) with controllable morphology, microstructure and surface property in the presence of Tween-60. The thermodynamic calculations proved the demanded energy of HAP nucleation upon lamellar PEO aggregates is less than one twentieth of that on HAP surface, and the nucleation upon lamellar PEO aggregates favors in the longitudinal direction of the lamellar aggregates resulting in the oriented crystal growth along the [001] or c-direction of HAP and forming the oriented raft-like HAP. The characteristic of P123, i.e. insoluble at CP and totally soluble below CMT, was used to prepare mesoscaled hollow HAP nanoparticles in the help of Tween-60 which possesses a much higher CP than P123 does. The resultant hollow HAP has a sphere-like morphology, and it can be transformed to rod-like shape with the addition of polar citric acid. The citrate added HAP hollow nanorods have a layer of citrate molecules with a thickness of 1.15nm coupled upon the inner surfaces, which are pH-responsive and have great potential in smart drug delivery system.Monetite/HAP nanoparticles with lamellar mesostructures were prepared using monododecyl phosphate (MDP) as the directing template. The morphology and layer space of the lamellar mesostructured products could be controlled by different Ca/P mol ratio, reaction temperature, addition of MDP and ethanol. These factors changed the chemical potential of the product. Therefore the product had to regulate its morphology and microstructure to keep the potential in banlance.In the mediation of MDP: the Sm3+ doped HAP had a excellent luminescence, which increased with the addition of Sm3+; the Fe2+ doped HAP nanoparticles were embeded with Fe3O4 orγ-Fe2O3, and had an increased magnetism with the addition of Fe2+; and multifunctional magnetic and luminescent mesoporous HAP nanoparticles were prepared by doping with Sm3+ and Fe2+, the doped Sm3+ and Fe2+ were found dispersedly embeded and solid-soluted in HAP, and the resultant magnetic and luminescent mesoporous HAP NPs possessed both good magtism and excellent luminescence, a high specific surface area (153.52m2/g) and a large pore volume (0.3286cm3/g) with a bimodal pore size distribution (3.64 and 9.014nm).In the drug loading process, the hollow property made all the hollow HAP NPs have a much higher drug payload than the traditional HAP NPs did. The citrate coupled hollow rod-like HAP had a relatively high drug payload of 24.14%, and it was further increased to be 35.83% with the addition of cationic polyelectrolyte poly (dimethyldiallyl ammonium) chloride (PDAD). In in-intro release, the loaded vancomycin was stored inside the citrate chelate hollow rod-like HAP when the pH was at acidity, and released in a neutral environment. Reversely, with the addition of PDAD, the drug was steadily stored at a neutral pH (7.4), the cumulative release was less than 28% for 20h. But the drug linearly released when the pH was at weak acidity, the cumulative release was more than 89% for 5h and 98% for 20h. In addition, the magnetic and luminescent mesoporous HAP NPs also had a high payload ratio of vancomycin, over 33%. The drug loading and in-intro releasing results indicated that the prepared hollow HAP with a mesoscaled hollow diameter and the magnetic and luminescent mesoporous HAP NPs, were smart and multifunction integrated drug carriers, having a great potential in biomedical applications.