Application Of Self-assembling Nano-peptide Hydrogels For The Sustained Delivery Of RhBMP2 To Enhance The Osteogenic Properties Of CHACC

Objective: 1.Analysis of the characterization and structure of coral hydroxyapatite artificial bone,that it is the ideal scaffold material,2 rhBMP2/RADA16/CHACC composite artificial bone in vivo osteogenic process,efficacy,and its biocompatibility and biodegradability,which provide a theoretical basis for the clinical application of CHACC.Methods: the macroscopic and microscopic structure,pore size distribution,pore size and pore wall of CHACC were observed by SEM.The phase structure was analyzed by XRD;The biomechanical properties of CHACC artificial bone were measured,and the porosity was measured by Archimedes drainage method;Preparation of 1.5cm bone defect model of rabbit radial shaft.The experimental group was implanted with rhBMP2/RADA16/CHACC composite artificial bone,and compared with the blank group and control group with CHACC alone.Samples were taken at 4,8 and 12 weeks respectively.The gross observation,X-ray and Micro-CT imaging analysis,mechanical test and histological observation were performed.Result:XRD detection of CHACC main components of hydroxyapatite and calcium phosphate;SEM cross-section observation,we can see its internal three-dimensional porous structure,pore diameter of 100-200μm,the surface covered with hydroxyapatite crystals;drainage method measured porosity of 65.02%;in vitro mechanical test:compressive strength is(6.8 + 0.85)MPa,the elastic modulus is(335.75 + 13.55)MPa;After the RADA16 is formed,it has a fibrous network structure.After loading on CHACC,RADA16 can be attached to the CHACC hole wall at different cross sections in the SEM mirror.The animal experiment,4 weeks after operation,gross observation,experimental group,the bone graft showed a large amount of bone callus formation,radial shaft diameter thickening material closely with new bone callus,the control group only a thin layer of bone graft bone wrapped;the experimental group at 8 weeks the material begins to disintegrate,the callus of the control group than before increased;the experimental group at 12 weeks softened,fragmentation and disintegration,partial degradation,control group material integrity,reduce the amount of bone callus around.The blank group was not repaired,and the medullary cavity closed at 12 weeks.Imaging examination,Lane-Sandhu image score gradually increased with time,4weeks score in the experimental group was significantly better than that in the control group,but there was no significant difference between the experimental group and the control group(P > 0.05);Micro-CT assessment,the incidence of callus formation in the experimental group was significantly higher than that in the control group after 4weeks(P <0.05),the control group callus formation is slow,the peak of the 8 week.Histological observation,there were more callus in the experimental group at 4 weeks,and the callus was close to the material,the control group has a gap between the material and the callus.At 12 weeks,the experimental group was disintegrated and the control group was intact.12 weeks biomechanical test,the experimental group of radial bending strength is better than the control group(P <0.05).