Controlled Synthesis And Application Of Calcified Inorganic Nanomaterials

Since calcium phosphate (CaP) are the main inorganic constituents of biological hard tissues such as bone and teeth, synthetic nanostructured CaP materials exhibit excellent biocompatibility and boiodegradability. Nowadays, CaP based functional nanomaterials have been well studied and applied in many fields such as tissue engineering、drug delivery、protein adsorption、bioimaging、antibacterial materials、 catalysis and environmental engineering. However, these CaP materials are mainly amorphous calcium phosphate (ACP) based and hydroxyapatite (HAP) based materials, the reports on β-tricalcium phosphate (TCP) based nanomaterials with intelligent and multifunctional properties are still scarce. This dissertation has given some progress of the synthesis of P-TCP based functional nanomaterials and their applications in the field of biomedicine and environmental engineering. The main contents of this dissertation are summarized as follows:In chapter 1, we provides an overview about CaP materials, preparation method of CaP materials and application of CaP materials. Based on above summarization, we put forward the main research contents of this dissertation.In chapter 2, we have demonstrated a new solvothermal strategy for the synthesis of P-TCP porous nanospheres with trimethyl phosphate as an organic phosphorus source. The as-prepared β-TCP nanospheres (average diameter about 120nm) were composed of 15-25nm β-TCP nanoparticles, which were assembled into nanostructured porous nanospheres, resulting in their relatively high specific surface area and cumulative pore volume. As a result, they have excellent cytocompatibility, high drug loading and protein adsorption capacities, and sustained pH-sensitive release behaviors. It follows that the uniform P-TCP porous nanospheres are more promising for applications in biomedical fields such as pH-sensitive drug delivery and protein adsorption.In chapter 3, multifunctional Gd, Ce, Tb co-doped β-TCP porous nanospheres are prepared by a facile solvothermal strategy with trimethyl phosphate as the phosphorus source. The as-prepared nanomaterial (average diameter of 100 nm) has a multiple level pore size distribution with the specific surface area of 124.33 m2 g-1 and cumulative pore volume of 0.39 cm3 g-1, which benefits drug loading. The as-prepared Gd, Ce, Tb co-doped β-TCP porous nanospheres exhibit excellent cytocompatibility and a relatively high DOX loading capacity (89.92 mg g-1) as well as sustained pH-sensitive drug release property, which attributed to the increased dissolution of the Gd, Ce, Tb co-doped β-TCP porous nanospheres in the acidic environment and the increased hydrophilicity and higher solubility of DOX at lower pH value caused by increased protonated -NH2 groups on DOX. The co-doping of Gd3+, Ce3+and Tb3+ ions endows β-TCP porous nanospheres with photoluminescent and magnetic multifunctions, making them promising for fluorescence imaging and magnetic resonance imaging (MRI). It is suggested that the Gd, Ce, Tb co-doped β-TCP porous nanospheres are promising for applications in the biomedical fields such as multifunctional drug delivery systems and tissue engineering scaffolds with bioimaging guidance.In chapter 4, we have successfully synthesized Ag/β-TCP nanocomposites through a facile two-step method. P-TCP nanospheres were firstly prepared by using a solvothermal method with trimethyl phosphate as an organic phosphorus source and were served as the supporting substrates. Then high-density Ag nanoparticles can be readily deposited onto the surface of the β-TCP nanospheres through an in situ growth process. The coverage of the Ag nanoparticles can be well controlled by changing the initial AgNO3 concentration. With the increase of coverage of Ag nanoparticles, the distances between them decrease, the coupling effects of adjacent Ag nanoparticles get enhanced, resulting in their UV-vis absorption peak became red-shifted and broadened. The as prepared Ag/β-TCP nanocomposites show good catalytic activity during the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4, excellent SERS property as well as highly sensitive and selective detection of hydrogen sulfide, which render them ideal candidates for various applications.In chapter 5, we reveal that N-stearoyl-L-glutamic acid (Cis-Glu, an amphiphile that mimics biomineralization-relevant biomolecule) can switch calcite crystallization from classical ion-by-ion to non-classical particle-by-particle pathway, which combine the classical and non-classical crystallization in one system.This growth mechanism change is controlled by the concentration ratio of [C18-Glu]/[Ca2+] in solution. The high [C18-Glu]/[Ca2+] can stabilize precursor nanoparticles to provide building blocks for aggregation-based crystallization, in which the interaction between Cis-Glu and nano precursor phase rather than that of Cis-Glu on calcite steps is highlighted. At a relatively low ratio of [C18-Glu]/[Ca2+], calcite with smooth faces was grown via ion-by-ion pathway, while both types of crystallization co-exist at intermediate ratio of [C18-Glu]/[Ca2+]. Our finding emphasizes the enrollment of organic additives on metastable nano building blocks, which provides an alternative understanding about organic control in inorganic crystallization.In chapter 6, we summarize the study. We have synthesized several β-TCP based functional nanomaterials, and investigated their applications in the field of bio medicine and environmental engineering. Moreover, we reveal that C18-Glu can switch calcite crystallization pathway from classical ion-by-ion to non-classical particle-by-particle, which is controlled by the concentration ratio of [C18-Glu]/[Ca2+] in solution. Finally, we analysis the shortages of this work and unsolved issues for further study.