The Study Of Preparation And Characterization Of PLGA/N-HA/α-Fe₂O₃ Composite Interface Screws

Objectives:Polylactic acid-polyglycolic acid(PLGA)is a biodegradable material obtai ned by polymerizing polylactic acid(PLA)and polyglycolic acid(PGA)in a certain p roportion.In vivo,it can be hydrolyzed and degraded by ester bond hydrolysis,and t hen converted to CO2 and H2O through the tricarboxylic acid cycle.It has good bioco mpatibility,non-toxicity,and good thermoplasticity.It was easy to combine with tissue,with excellent biocompatibility,osteoconductive properties,so Nano-hydroxyapatite(n-HA)could form composite materials with a variety of natural and artificial polymers.By adding superparamagnetic nano-α-Fe2O3 to the polymers,it could simultaneously ind uce and promote tendon healing after the operation of anterior cruciate ligament reconst ruction under the effect of constant magnetic field.This study investigated the preparat ion process of biomaterial interface screws with superparamagnetism by using n-HA/P LGA and superparamagnetic nano-α-Fe2O3,and compared with common clinical interfac e screws,looking forward to produce a more ideal and appropriate material of interna 1 fixation for anterior cruciate ligament reconstruction.Methods:1.Group A:Accurately weigh PLGA 225 g and n-HA 11.8 g,add methylen e chloride 2000 ml,mix for 4-6 hours after dissolving,vacuum dry to constant weigh t.Then the mixed materials are made into pellets by a torque rheometer.And then th ey are made into the injection molding machine for injection molding.Group B:Accu rately weigh PLGA 225 g,n-HA 11.9 g and α-Fe2O3 2.4 g,add dichloromethane 2000 ml,mix for 4-6 hours after dissolving,and vacuum dry to constant weight.Then the mixed materials are made into pellets by a torque rheometer.And then they are mad e into the injection molding machine for injection molding.Using the MILAGRO(TC P/PLGA)interface screw(US Johnson&Johnson)as the control group C,the torsion al performance,screw-in torque,and axial pullout of the three sets of interface screws are based on the current "China Pharmaceutical Industry Standard YY/T0509" standar d.The output was compared to obtain the mechanical properties of the three sets of i nterface screws.Compare the degradation performance of the two groups of materials in vitro by comparing the degradation rates of three groups of interface screws in pho sphate buffer(PBS).2.Three 6-week-old female New Zealand white rabbits weighing about 2.3 kg were selected and femoral puncture was performed to extract rabbit bone marrow in aseptic environment.The rBMSCs were isolated from femoral marrow bloo d and purified by density gradient centrifugation combined with adherence method,whic h were cultured and passaged in low-glucose DMEM with 10%FBS to the third gene ration then,meanwhile the cell growth of the third-generation rBMSCs were observd.3.The third-generation rBMSCs were cultured respectively with sterilized PLGA/n-HA/α-Fe2O3,PLGA/n-HA,and MILAGRO(TCP/PLGA)interfacial screws in culture mediu m.Precipitation method and CCK-8 method was used to detect the cell adhesion rate and proliferation activity on the surface of the screws.Results:The PLGA/n-HA and P LGA/n-HA/α-Fe2O3 composite interfacial screws prepared by hot melt injection mol din g had good shapes,uniform threads and good three-dimensional structures of aperture.The average maximum torque of the PLGA/n-HA group,the PLGA/n-HA/α-Fe2O3 grou p,and the MILAGRO(TCP/PLGA)group were 1.92 Nm,2.02 Nm,and 1.30 Nm,re spectively.And the mean values of the yield torques were:1.69Nm,1.91Nm,0.83Nm;Spin-in test PLGA/n-HA group,PLGA/n-HA/α-Fe2O3 group,MILAGRO(TCP/PLGA)group,screw-in torque mean:0.76Nm,0.64,respectively Nm,0.30Nm;PLGA/n-HA g roup,PLGA/n-HA/α-Fe2O3 group,and MILAGRO(TCP/PLGA)group in the pull-out experiment,the maximum pull-out force values were:355N,372N,275N;The degrad ation curves of the sets of screws in PBS showed that the degradation rate of PLGA/n-HA/α-Fe2O3 group was significantly higher than that of PLGA/n-HA group,while th e degradation rate of PLGA/n-HA/α-Fe2O3 group and PLGA/n-HA group was signific antly lower than that of the clinical PLGA/TCP group.Precipitation showed that the c ell adhesion rate of rBMSCs in the PLGA/n-HA group was 55.9±1.02%,the PLGA/n-HA/α-Fe2O3 group was 64.1 ± 1.15%,and the clinical screw group was 62.3±1.23%.T he difference above three groups was statistically significant(P<0.05).The cell growth cu rves of rBMSCs on the surface of screws indicated the cell proliferation of the n-HA/PLGA/α-Fe2O3 group was better than the clinical screw group,and the clinical screw group was better than the PLGA/n-HA group.Conclusions:The PLGA/n-HA/α-Fe2O3 c omposite interface screw has better cell adhesion and proliferation activity than the co mmonly used clinic interface screws.It can promote cell proliferation and growth with good cell compatibility.And PLGA/n-HA/α-Fe2O3 composite interface screw has bette r mechanical properties than the other two groups.However,the degradation of the P LGA/n-HA/α-Fe2O3 composite interfacial screw is slow,which needs to be further expl ored by changing the molecular weight of PLGA.Therefore,the PLGA/n-HA/α-Fe2O3 composite interface screw is an interface screw with good mechanical properties and c ell compatibility.