Synthesis Of Ba/Mg Co-doped Hydroxyapatite And Its Research In Bone Repair

In healthy conditions,bones have a unique ability to heal without inducing scar tissue formation.However,clinically complex or large defect fractures(i.e.,fractures that exceed the critical size and severely damage the surrounding environment)may not heal naturally,leading to nonunion.Diabetes,genetic factors,and poor lifestyle(such as smoking or alcohol use)increase the risk of delayed and non-healing.In addition,inappropriate early treatment of fractures may lead to complications and nonunion.These poor health conditions usually result in poor vascularization/disruption around the bone and insufficient progenitor cells to form new bone,leading to failure of the natural healing process.There are other indications that require bone tissue healing,such as bone defects due to tumor clearance,infections,and the increasing need for prosthetic limbs.In addition,low back pain has become a common burden on society as a whole,and is often associated with osteoarthritis and degenerative diseases of the lumbar spine,where severely impaired joints and degenerative diseases may require interbody fusion.Arthropathies are most common in the spine,hands,and ankles.All of these conditions require bone tissue fillers and bone bridging.At X present,the main surgical intervention measures mainly rely on autograft or allograft,but both of them have certain risks.Autologous bone graft requires additional surgery,and has the risk of postoperative infection and donor site complications,while allograft has the risk of transmission of disease and immune rejection.Biodegradable polymer materials such as PLGA continue to develop,especially their composition of HA(hydroxyapatite)composite materials show a good prospect for bone tissue engineering.These materials are biocompatible,easy to process and can replace bone repair or damaged bone tissue.In recent years,HA/PLGA has attracted a lot of attention due to its good biocompatibility,bone conductivity and degradability.Bone implants not only meet the bone conductivity,but also need to have certain osteoinduction properties.HA only has certain biocompatibility and biological activity,but it is insufficient in inducing osteogenic differentiation,while PLGA only has biocompatibility.As the main material of bone nails and plates widely used in clinic,magnesium metal has good biocompatibility and bioactivity.Magnesium doped with hydroxyapatite can significantly improve the osteoinduction of HA and promote osteogenic differentiation.After implantation in vivo,X-ray observation is often needed for postoperative monitoring.Pure PLGA scaffolds had a low density and could not be detected under X-ray.A high mass fraction ratio is required for the HA/PLGA composite to achieve the desired X-ray imaging function,which prevents the HA/PLGA composite scaffold from forming during injection.To solve this problem,the metal Ba element was doped into the hydroxyapatite crystal cells.As a metal element,Ba is often used as a contrast agent in clinical practice in the form of barium sulfate compound for intestinal detection because of its good imaging function.The imaging function of HA can be significantly enhanced by doping the metal Ba element into HA.The main metal ion of HA is Ca ion,and the co-doping method of metal ions can introduce both Ba/Mg elements into HA at the same time,so that HA can have the functions of two elements at the same time,so as to achieve the effect of both promoting osteogenic differentiation and imaging function.In this study,Ba/Mg ion co-doped nanometer HA was prepared by means of metal ion co-doping and phase conversion,and Ba/Mg@HA/PLGA composite material was successfully prepared by using the phase conversion method with NMP(N-methylpyrrolidone)as the solvent.Firstly,the morphology of Ba/Mg@HA nanoparticles was analyzed,and its composition was explored by XRD,IR and ICP analysis.At the same time,the morphology,ICP,degradation and mineralization of Ba/Mg@HA /PLGA scaffolds were analyzed.The imaging ability of Ba/Mg@HA /PLGA scaffolds was detected by X-ray.Secondly,in vivo experiments on Ba/Mg@HA /PLGA were carried XII out to explore the cytotoxicity,cell proliferation and cell adhesion of this new material,and then to explore the protein expression and gene expression in the process of promoting osteoblastic differentiation of the material.The osteogenic differentiation efficiency of the material was confirmed by alkaline phosphatase and alizarin red experiments.Finally,different groups of Ba/Mg@HA /PLGA scaffolds were applied to the model of tibial plateau defect in rats.The biocompatibility of Ba /Mg@HA/PLGA scaffolds and their role in osteogenesis were proved by experiments.The above studies confirmed that Ba/Mg@HA/PLGA has certain X-ray imaging ability and good osteogenic activity,so it can be used as a new bone repair material.Part ?: Preparation and characterization of Ba/Mg@HA nanoparticles and Ba/Mg@HA/PLGA scaffolds.The ion co-doped Ba/Mg@HA nanoparticles were prepared by hydrothermal method.The particle size distribution was nm level.The X-ray diffraction spectra,functional groups and elemental composition of the nanoparticles were analyzed.At the same time,the micromorphology of Ba/Mg@HA/PLGA composite scaffold,the change of p H value during degradation,the release of ions and the surface morphology after mineralization were analyzed.The results show that the upper limit of ion doping is low for single element doping.This may be because the radius of different metal ions is not consistent.HA begins to transform like amorphous calcium phosphate when 2Ba is doped.This may be because the radius of Ba ion is larger than that of Ca in HA.However,by introducing equal proportion of Ba and Mg in the double-doping method,the distortion degree of the lattice can be reduced.Because half of the sum of the radii of Ba and Mg is similar to that of Ca,we observed this result through the lattice analysis of XRD.When 2Ba was doped,the overall peak of hydroxyapatite shifted to the left,while 2Ba/Mg@HA still maintained a good XRD characteristic peak.X-ray detection of Ba/Mg@HA /PLGA composite scaffolds found that the imaging characteristics of 2Ba/Mg@HA /PLGA composite scaffolds were the most obvious,while the imaging characteristics of pure HA/PLGA composite scaffolds and PLGA scaffolds were weak.Part ?: Observe the biological effects of Ba/Mg@HA/PLGA complex and Ba /Mg@HA in vivo.By cell extraction experiments,it was found that all components of the extract reached 100% proliferation efficiency in 16 times dilution solution.After 1,3 and 7 days of CCK experiments,it was found that the cell proliferation of the components with Mg element was more obvious than that with the same Ba content,and the proliferation result of 2Ba/Mg@HA/PLGA was the highest.We verified the results of cell proliferation by 1?3?7 day cell death staining.From the fluorescence staining of calcein,it was found that2Ba/Mg@HA/PLGA component had the highest number of cell proliferation thanks to the doping of magnesium ions.Correlative results of immunofluorescence also showed that the secretion of osteoblast differentiation related proteins in the components containing Mg was higher than that in the components with the same Ba element doping,and the expression level of 2Ba/Mg@HA/PLGA was the highest.PCR results showed that there was no significant difference among OCN components,which might be due to the end of OCN expression peak,while BMP and OCN results showed that the doping of magnesium promoted the expression of genes related to osteogenic differentiation.Finally,we observed the effects of the materials on cell differentiation through alkaline phosphatase and alizarin red staining.The effect of the Mg-doped materials on promoting ALP and promoting the formation of calcium nodules was due to the fade of the Ba doped components,and the effect of 2Ba/Mg@HA/PLGA was the best.Part ?: In vivo osteogenic study of Ba/Mg@HA /PLGA composite scaffolds.In this chapter,we studied the osteogenic effect of Ba/Mg@HA/PLGA composite scaffold in rats with tibial defect model.The results show that the content of Mg ion in the scaffold determines the efficiency of bone repair.The osteogenic effect of 2Ba/Mg@HA/PLGA component was higher than that of other components.Moreover,the inflammatory response of tissues was demonstrated through tissue sections of different parts,which proved that 2Ba/Mg@HA/PLGA had no toxic effect on animal tissues...