Preparation And Biological Properties Of Ti-based Nanomaterials And Drug-Loaded Au Nanocages

With the development of nanotechnology,nanomaterials have been widely used in biomedicine,including disease diagnosis,cancer therapy,drug delivery,biological imaging and tissue engineering.This dissertation mainly focused on the preparation of multifunctional Ti-based nanomaterials and their applications in bone tissue engineering,as well as the application of drug-loaded Au nanocages in cancer therapy.The main contents of this dissertation are as follows:(1)Preparation of calcium titanate nanosheets and their osteogenic propertiesSurface modification is an effective method to improve the integration performance of the bone implant materials.In this study,calcium titanate nanosheet was prepared using two step hydrothermal methods.The as-obtained materials present high roughness and good hydrophilicity.The content of Ca can be controlled by the temperature of the hydrothermal reaction.In vitro and in vivo experiment was performed to evaluate the biocompatibity and osteogenesis of a series of nanomaterials with different Ca content.As demonstrated by the SEM images,the Ca-contained nanosheets can significantly promote the adhesion and spreading behavior of MC3T3-E1 cells.In addition,cell viability increased significantly with the increase of Ca content and the prolonged culture time.The results of fluorescence images indicate the calcium titanate nanosheet significantly enhance the migrigation of MC3T3-E1 cells on the surface of the prepared materials,which is important for the bone regeneration.In addition,the in vivo experiment was used to further evaluate the osteogenic properties of the prepared nanomaterials.The X-ray results and the HE/masson's staining results show that the calcium titanate nano-sheet present strong osteoinduction ability,which could promote the calcification and growth of new bone.(2)Preparation of Zn-contained nanoarrays and their antibacterial and osteogenic propertiesNew generation of bone implants with long-term antibacterial activity and favourable biocompatibility have attracted a great deal of attentions recently.In this study,we have designed and prepared Zn-contained-Ti02 nanorod arrays through two-step hydrothermal method,the content of Zn can be controlled by the concentration of precusor.We use SEM,MTT and ALP assays evaluate the cytocompatibility of the Zn-incorporated TiO2 nanoarrays.Among all Zn-incorporated TiO2 nanoarrays,TiO2-Zn0.2 presents the most remarkably stimulative effects on the growth of MC3T3-E1 cells when compared with pure Ti and Ti02 nanorods.Meanwhile,the antibacterial tests confirm that the hybrid nanoarrays can effectively inhibit the growth of Escherichia coli(E.coli,Gram-negative)and Staphylococcus aureus(S.aureus,Gram-positive)to various degrees.And the antibacterial properties were enhanced with the increase of Zn content.However,due to the Zn was modified on the surface of Ti02 nanorod,all materials present explosive release of Zn ions,which go against the long term antibacterial properties.In order to improve the Zn content and control the release of Zn,in the other project,we prepared highly-ordered and interconnecting Zn-incorporated ZrO2 nanoarrays.It was prepared by a hydrothermal approach with the precursor hydrolyzed in situ.The Zn ions released from the interval of ZrO2 nanoparticle,successfully avoiding the explosive release of Zn ions.The content of Zn can be easily controlled by pH value of the HCl solution.All Zn-incorporated nanoarrays show good antibacterial properties against both E.coli and S.aureus,as indicated by high antibacterial rates and the apparent inhibition zone.Analysis of the biocompatibility confirms that the hybrid nanoarrays could cause varying degrees of promotion for the adhesion and spreading of MC3T3-E1 cells.Zn-incorporated-ZrO2-nanotubes balance antibiosis and osteogenesis delicately,as proved by the upregulated MTT and ALP activities,as well as the increase of bone-related gene expression.The novel bone implant materials with better antibacterial properties can promote the osteogenesis,and have promising applications in biomedical devices.(3)Design of alveolate Se-inserted TiO2 and its effect on osteosarcoma cells and osteoblastsOsteosarcoma is a common clinical disease with high incidence,relapse rate and lethality.Thus it is urgently necessary to fabricate bone implants with anti-tumor functions to improve the prognosis of bone cancer.In this study,a novel double-layer Ti02 nano-grid with an outer diameter of 100 nm and an inner diameter of 35 nm is prepared by a simple two-step anodization procedure.In the outer pore of the double-layer TiO2 nano-grid,we precisely embed selenium(Se)nanoparticles using electrodeposition,and this process can be readily tailored by adjusting the time.Biological assays indicate that the prepared Se-embedded Ti02 nano-grid arrays show a dose-dependent anti-tumor effect by inducing apoptosis in MG63 cells.Compared with the Ti substrate,the Se-embedded Ti02 which has a double-layer honeycomb structure facilitates healthy cell(MC3T3-E1)growth when the electrrodeposition time is less than 1 h.Thus the novel bone implants have a balanced anti-tumor effect and biocompatibility and are therefore potential candidates for the treatment of osteosarcoma(4)Preparation of selenous acid-loaded Au nanocages and their application on cancer treatment.Gold nanocages(AuNCs),is emerging as an attractive photothermal agent owing to its high photothermal conversion efficiency.Here we demonstrate a new formulation of nanomedicine based on selenous acid,which is mixed with lauric acid(a phase-change material with amelting point around 43 ?)and then loaded into the cavities of Au nanocages.The Au nanocages can serve as a carrier during cell endocytosis and then as a photothermal agent to melt the lauric acid upon the irradiation with a near-infrared laser,triggering the swift release of selenous acid.The photothermal and chemo therapies can also work synergistically,leading to enhanced destruction of cancer cells.Our systematic study suggests that the selenous acid that released in the cell can generate intracellular ROS,which is responsible for impairment of mitochondrial function and cell death.This study offers an appealing candidate that holds great promise for synergistic cancer treatment.