Research Of Rare-earth Elements Doped Hydroxyapatite Nanowires Materials For Hard Tissues Repair

Stoichiometric hydroxyapatite(HA)is very similar to the minerals widely existing in human hard tissues(i.e.,teeth and bone)in both crystal structure and chemical composition,thus it has good biological activity and biocompatibility,which can be used as hard tissues repairing materials.The common available forms of HA are granular,needle-like and rod-shaped,while HA nanowires(HANW)are more attractive for biomedical applications for their one-dimensional morphology.On one hand,HANW can mimic the nanofibrous networks in natural extracellular matrix to create biomimetic microenvironment for tissue regeneration.On the other hand,one-dimensional HANW can be used as fillers for composite resins basing on the concept of multi-scale/multi-dimensional reinforcement to improve the performance for dental restoration.In both the aspects,however,there are difficulties to detect the the in-situ dispersion,location and long-term changes of the HANW.Therefore,the major purpose of this thesis is to develop a kind of fluorescent HANW via the doping of rare earth elements such as Eu3+ and Gd3+ ions,which will endow the resulting HANW with high quantum efficiency,large Stokes shift,long fluorescence lifetime and stable luminescenceIn this thesis,one-dimensional HA nanowire(HANW)were synthesized by hydrothermal method,and different rare earth ions(Eu3+and Gd3+)were doped in the synthesis process to obtain single-doped HA nanowires(HANW:Eu)and double-doped HA nanowires(HANW:Eu/Gd)and allows the HANW to autofluorescence.First,HANW:Eu was filled into the composite resin,and the effect of different mixing modes(kneading,grinding and stirring)on the dispersion of HANW was compared using the autofluorescence property of HANW:Eu.Secondly,HANW:Eu/Gd was used as bone powder to fill the skull defect of rats,and the in vivo tracing study was carried out by autofluorescence of the material.Main tasks as follows:1.Using calcium oleate as raw material,HANW:Eu and HANW:Eu/Gd were synthesized by hydrothermal method,and the optimal doping proportion was explored by testing fluorescence intensity and quantum efficiency.It was found that HANW:5%Eu had the highest fluorescence intensity,but the fluorescence intensity from HANW:5%Eu was not strong enough to penetrate the skin when it was embedded under the skin of nude mice and observed by small animal in vivo imaging system.The total content of rare earth elements should be controlled at 5%.When the ratio of Eu3+ and Gd3+ was 4:1,HANW:4Eu/1 Gd had the highest fluorescence intensity.After the oleic acid in the product was completely removed by high-temperature sintering,it was buried under the skin of nude mice,and the obvious fluorescence could be detected by the in vivo imaging system of small animals.2.The HANW:5%Eu is compounded as a filler with a photocurable resin and dispersed in different mixing modes.The fracture surface was observed by SEM,and the three-dimensional imaging function of LSCM was combined with the flexural strength test to determine that the kneading could obtain a better dispersion state of HANW.However,it was found that the barium glass powder(0.7 ?m)and HANW:5%Eu were combined with the photocurable resin(total content 70%),and even with the kneading method,HANW with a large aspect ratio failed to be mixed uniformly with the bismuth glass powder.As a result,significant HANW agglomerates were observed under LSCM.3.The research of CHANW:4Eu/1Gd as a filling material for bone defects was carried out.Firstly,by extracting cell culture and cell seed culture,combined with SEM after 7 days of co-culture,it was confirmed that CHANW:4Eu/1Gd had no obvious biological toxicity.The alkaline phosphatase activity and type I collagen synthesis of the cells were detected by differentiation assay.It was found that CHANW:4Eu/1Gd can promote osteogenic differentiation of BMSC more than pure HANW.Using a 5 mm defect model of the rat skull,using HANW and Bio-OSS(?)as a comparison,micro-CT and histological staining analysis showed that the bone repair effect of the experimental group filled with CHANW:4Eu/1Gd was significantly better than that of the blank group and the pure HANW group,close to the Bio-Oss(?)group.Through small animal imaging and LSCM of the skull,the filled CHANW:4Eu/lGd was clearly observed,indicating that the degradation of HA materials was slow and persisted in the new tissue,confirming the claim of space-occupying repair.The above studies showed that by doping rare earth elements into HANW and endowing HANW with photofluorescence characteristics,HANW could be used as composite resin filler or bone defect filling material to achieve tracer,providing an in-situ characterization means for its subsequent biological applications.In addition,it was found that the doping of Eu3+ and Gd3+ also improves the osteogenic activity of HANW to a certain extent,which is expected to be used as a guide bone regeneration and repair material in the field of bone tissue engineering.