Study On Preparation Technology And Performance Of PLAG/nHA/Mg Composite Bone Repair Scaffold

Bone is one of the most important organs in the body,and it is the key organ to support the normal physiological activities of the body.To a certain extent,bone has the characteristics of self-regeneration,but faced with too many bone defects produced by organisms,the selfrepair ability of bone will be severely limited.How to repair large bone defects caused by trauma,hormone and tumor trauma has become a hot research direction in medical field.Autologous and allogeneic bone repair or metal transplantation,which are commonly used in clinical treatment of bone defect diseases,have achieved certain application results,but there are still some problems such as limited sources of materials or serious complications.At present,tissue engineering can provide customized and accurate medical measures for patients through effective material preparation and various preparation methods.In this study,three materials were used as raw materials: polylactic acid-glycolide(PLGA),which is non-toxic,safe and excellent in biocompatibility;nano hydroxyapatite(nHA),which has excellent bone conductivity and calcification;And magnesium(Mg),which has the function of promoting osteoblast growth and reproduction and inhibiting bacteria.The preparation process,performance characterization and in vitro degradation application of a new composite PLGAnHA-Mg scaffold for bone repair and tissue engineering were studied by low temperature deposition manufacturing technology(LDM)with the low temperature deposition manufacturing equipment developed and designed in the laboratory.The main contents of the study are as follows:Design the preparation conditions of(0°45°),(0°90°),(45°135°)scaffold angles,(0.6mm,0.75mm,0.9mm)filling spacing and(5%,10%,20%,30%)pure magnesium ratio,and explore the best LDM through orthogonal experiment.Three-dimensional digital model is established by Solid Works,and the mechanical properties of models under different frame angles and filling distances are discussed by using the finite element analysis software ANSYS.The results show that the scaffold with scaffold angle of(0°90°)has the best stability,and 55.7% of the joints of the scaffold with the scaffold angle of(0°90°)and the filling spacing of 0.75 mm are in the microstrain range beneficial to bone growth.The morphology of the stent was characterized.With the increase of magnesium content,aggregation effect will be formed in the stent,which will affect the pore size range of the stent.Research shows that the packing interval is a key factor that affects the pore size.The ethanol displacement volume experiment verified that the porosity of the prepared scaffolds could meet the porosity requirements of blood vessel growth and osteoblast proliferation in tissue engineering.Through the mechanical performance experiment of the bracket,the structural angle parameters with the best mechanical performance are obtained,and the influence trend of the material content and the filling spacing on the mechanical performance of the bracket is clarified.Morphology,Structure,Characterization and Performance of the scaffold the experimental results finally showed that the performance requirements of PLGA-nHA-Mg scaffold with the filling space of 0.75 mm,the scaffold angle of(0°90°)and the magnesium content of 10%-30% were the most consistent with the human bone implantation conditions.Through degradation experiments,the degradation laws and possible application scenarios of PLGA-nHA-Mg scaffold materials with different magnesium contents were studied.The correlation and law between the magnesium content and the liquid storage rate of the scaffold were obtained.The degradation trend and speed of the scaffold in 28 days,the relationship between the magnesium content and the degradation rate of the scaffold,the rising trend of magnesium ions and the change law of p H in the degradation process were also obtained.The optimal p H of the scaffold was 5%-10%.Through macroscopic and microscopic observation,the causes of scaffold degradation and morphological damage were discussed.