Study On Fabrication And Properties Of 3D Porous Bone Tissue Engineering Scaffolds

Bone tissue engineering is a science that applies the principles and methods of biology and engineering to develop functional substitutes for damaged tissue.The research and development of bone tissue engineering make up the shortage of traditional bone graft in clinic,and provide a new way to repair bone defect.3D porous scaffold is the key point of tissue engineering bone which exerts the function as the extracellular matrix,such as withstanding pressure from surrounding tissues,guiding cell adhesion,and promoting the transport of cells and metabolites.Biodegradable composite scaffolds have been widely studied in the repair of human bone defects due to their good biodegradability,biocompatibility,proper mechanical properties and pore structure similar to cancellous bone.However,the immature bone tissue engineering theory and the incomplete composite scaffold fabrication technology make the presently developed scaffolds for bone tissue engineering present more or less unsatisfied aspects for clinical application,among which the most crucial ones are: insufficient mechanical properties,failling to meet the requirements for bearing bone repair;uncontrollable degradation rate,mismatching with the new bone regeneration rate;cell activity deletion,lack of cell recognition site for scaffold with synthetic polymers as matrix.Based on the above problems,three scaffolds were prepared by the modified methods in our work.Their structures and related properties were investigated in detail,and the above mentioned problems were further elaborated.(1)Fabrication and its mechanical properties of poly(lactic acid)/ethyl cellulose/hydroxyapatite(PLA/EC/HA)composite scaffolds.Insufficient mechanical properties of the scaffold will lead to premature failure during its application.In this chapter,PLA/EC/HA composite scaffolds were fabricated by a combined technology of high concentration solvent casting,particulate leaching,and room temperature compression molding.PLA and EC were used as matrix,and HA acted as reinforcing agent and bioactive substance.The purpose of adding EC in the matrix was to improve the hydrophilicity and mechanical properties of PLA.HA,a major component of natural bone,has been shown to have good biocompatibility and osteoconductivity and plays an important role in the repair of bone damage.Thermogravimetric(TG)analyses,contact angle and water absorption tests,and in vitro degradation tests showed that the composite scaffolds had good thermal stability,hydrophilicity and degradability.More importantly,the micromorphology observation and mechanical tests showed that high concentration solvent casting and room temperature compression molding process made the scaffold a compact and stable structure,which improved the compression performance of the scaffold,and the compressive strength of the P8H2 composite scaffold with the optimal compression performance was 1.57 ± 0.09 MPa,which reached the range of compressive strength of the cancellous bone,thus favorably achieving the requirement of the mechanical properties for repairing the load-bearing bone.(2)Fabrication and its in vitro degradation of poly(lactic acid)/lignocellulose/hydroxyapatite/58 S bioactive glass(PLA/LG/HA/BG)composite scaffolds.How to easily regulate the degradation rate of scaffold is a hot topic in the field of bone tissue engineering.Herein,a novel PLA/LG/HA/BG composite scaffold was fabricated by a simple process combining solvent casting/particle leaching and sol-gel method.PLA worked as the matrix,HA and LG acted as zero-dimensional and one-dimensional reinforcing agents,HA and BG endowed the scaffold with the biological activity.The microstructure morphology,mechanical properties and surface bioactivity of the composite scaffolds were investigated.Specially,the degradation behavior of the developed scaffolds were evaluated by the in vitro degradation test.The results showed that the scaffolds had good mechanical properties,and the compressive strength of P20B1 composite scaffold with the optimal compression performance was 1.76 ± 0.15 MPa;The bone-like apatite deposition in SBF was greatly promoted by the incorporation of BG in the scaffold;Obviously,with the increase of BG content,the degradation of the scaffolds were gradually accelerated.In theory,bone reconstruction could be achieved by matching the degradation rate of the composite scaffold implanted in the defect with the growth rate of the new bone.That was to say,the controllable degradation of the scaffold was achieved by simply adjusting the content of BG.In the whole,a novel bone tissue engineering scaffold with suitable 3D porous structure,excellent mechanical properties,controllable degradation and good surface bioactivity was developed.(3)Fabrication and its cytocompatibility of polycaprolactone/58 S bioactive glass-sodium alginate/gelatin(PCL/BG-SA/Gel)hybrid scaffolds.Natural-synthetic hybrid combines the excellent cell activity of natural polymers and the outstanding mechanical properties of synthetic polymers,and owns unique properties that a single polymer does not possess.Herein,we selected SA and Gel from natural polymers,PCL from synthetic polymers,and BG from inorganic materials to fabricate a novel PCL/BG-SA/Gel hybrid scaffold.The use of Gel in the scaffold would enhance cellular activities-including attachment and proliferation-through interactions between the Arg-Gly-Asp(RGD)domains of Gel and the integrin receptors in the cell membrane.As the scaffold struts were still PCL/BG composite,the scaffold exhibited excellent compression performance,and the compressive strength of HS-3 scaffold with the optimal compression performance was 1.44 ± 0.02 MPa,which met the mechanical requirement for cancellous bone repair.Specially,it was worth mentioning that a modified melt molding method was used.SA/Gel composite microsphere was prepared by a simple syringe dropwise method,and then it was used as porogen during the subsequent melting casting process to prepare porous scaffolds.The newly-developed technology in this work was a simple and feasible method and was of great significance for the further development of natural-synthetic material.