The Applied Research Of Collagen-hydroxyapatite Composite Materials For Bone Regeneration

Bone defects caused by disease, trauma, or surgery, increase with years, and threaten the human health. The traditional treatment for bone defects include autografts and allografts, though there are some restrictions, such donor site morbidity and donor shortage for autograft, immunologic response and risk of infecting disease for allografts. Artificial bone substitute materials are also used for bone repair. The biomedical materials used for bone repair and regeneration have developed from the first generation-bioinert materials, the second generation-bioactive materials and biodegradable materials, to the third generation-the biomaterials based on celuller and molecular level. At the same time, the new theories and methods of tissue engineering and in situ tissue regeneration bring the new technology for the treatment of bone defects. The research of the third generation biomedical materials, which combine the bioactivity with biodegradation, is the base for applying the methods of tissue engineering and in situ tissue regeneration for repair of bone defects. So, research and develop osteoinductive and biodegradable bone substitute materials for the need of clinic is the major aspect in the area of biomedical engineering.In this study, simulating the composition and structure of nature bone, we prepared the collagen-hydroxyapaptite(HA) compsite, and incorporated the BMP into the material to develop the biomedical material for bone tissue engineering and in situ tissue regeneration which combine the osteoinduction with biodegradation. The paper includes four parts as following:1.Preparation and characterization of the collagen-HA compositeUsing collagen and HA as main raw material, the collagen-HA composite material was prepared by the process of blending, chemical crosslinking and so on, the structure, physical and chemical properties of the material were characterized, the biocompatibility of the material was evaluated according to GB/T16886 series standard. After the material was contacted with plasma, the capability of the material to absorb plasma protein and effect on calcium(Ca), phosphorus(P) were investigated. SEM photogragh of collagen-HA composite show the material has porous microstructure. It possesses excellent biocompatibility for its chemical, physical and biological properties accord with standards about the biomedical materials. After the material is contacted with plasma, the TP, FiB and FNC in plasma decreased. It indicate the absorption of protein on the surface of the materials, which may benefit for the formation and mineralization of bone. The increasing of Ca and P in plasma is related with the releasing of ions from the material, it may participate in metabolization and accelerate the osteoinduction.2. The ectopic osteoinduction of collagen-HA/BMP compositeThe collagen-HA composite was combined with BMP by absorption, and implanted into the muscle of rat. The ectopic osteoinduction of the material was estimated by histological observation, alkaline phosphatase(ALP) stain and measurement. The results show that Collagen-HA composite and HA which is combined with BMP have obvious ectopic osteoinduction, and the materials which is not combined with BMP have no ectopic osteoinduction.3. New bone formation and segmental bone defects repair with collagen-HA/BMP composite in vivoCollagen-HA/BMP composite was implanted into bone defect about 10mm in the shaft of the radius of rabbits. In order to observe the new bone formation and the degradation process of the material, a series of examination were carried out including blood biochemical test, SEM, biomechanical test and histological observation. The results show that the collagen-HA composite have the capability to repair bone defect and can be biodegraded, incorporation of BMP can accelerate the formation of new bone. The material can be used as the carrier for BMP to sustain its releasing, protect its bioactivity, improve the osteoinduction.4.The research of collagen-HA composite scaffold for bone tissue engineering and the release properties of the scaffold incorporated proteinThe porous collagen-HA scaffolds were prepared by lyophilization. Microstructure and properties of the scaffold was characterized. Chitosan colloid particle carrying model drug BSA was prepared by the method of ionic gelatin, and incorporated into the scaffold. BSA release from the system was studied in vitro and in vivo. The collagen-HA scaffolds used for bone tissue engineering are porous with three-dimension interconnected fiber microstructure, and pore sizes are 50-150μm. Compared with pure collagen, the mechanical property of collagen-HA composite improves significantly. Crosslinking by formaldehyde and EDC both decrease the degradation rate of the scaffold and increase the mechanical property. The scaffold has good biocompatibility and suitable for used as bone tissue engineering.The size of chitosan particle prepared by ion crosslink is 200-300nm. In vivo release studies show that encapsulating BSA by chitosan particle, then incorporating the chitosan particle into the scaffold, would apparently enhance the controlled release effect to prolong the local retention of the protein after implantation. The results of in vitro release studies show good pertinency with respective in vivo results.