Preparation And Evaluation Of Three-dimensional Chitosan-baesd Porous Composite Scaffolds Material

Bone defect is one of the most common and intractable diseases in the clinical medicine.Bone tissue engineering has a unique advantage to repair the bone lesions or defects.The scaffold materials plays a vital role in bone tissue engineering,which not only transport the seed cells and growth factors to bone defect sites,but also support the new-grown bone tissue.In recent years,biodegradable polymer materials are widely used in bone tissue engineering.Chitosan(CS)as a natural polymer material,has good biocompatibility and biological activity.The polysaccharide skeleton structure and its unique chemical properties can promote cell adhesion and proliferation.Hydroxyapatite is the main inorganic component of human bone tissue with excellent biological activity and bone conduction performance,which can provide biologic cues for cells adhesion,growth and differentiation.However,it is still a big challenge to improve the biological mechanical al performance of chitosan/nanohydroxyapatite(nHA)composite scaffolds to satisfy the requirements of clinical application.Graphene and its derivates have excellent mechanical properties,large specific surface area,and good biocompatibility,which can improve not only the mechanical properties of chitosan-based scaffolds,but also their biological activities.In this paper,GO was prepared using Hummer's method and functionally modified by carboxylation.The reaults of FT-IR and XPS characterizations confirmed the carboxylation of cGO.nHA was synthesized using sodium polyphosphate and calcium hydroxide as the raw materials through a hydrothermal process.SEM images showed that the nHA was uniform with an average diameter of 40-60 nm.Secondly,three-dimensional(3D)CS scaffolds were perpared by lyophilization.Several parameters,including the chitosan concentration and pre-freezing temperature,on the microstructures of the CS porous scaffolds were studied.Subsequently,CS/cGO scaffolds were prepared through covalent bonding between the carboxyl groups of cGO and amino groups of CS in the presence of EDC and NHS.The results indicated that the surfaces of pore walls become rougher with the increase of cGO content and the addition of cGO in CS matrix improved the mechanical properties when the cGO content was less than 2.5 wt.%.Furthermore,the CS/cGO/nHA porous composite scaffolds were prepared using the same precedures and characterized by mechanical properties,SEM,EDAX,FT-IR,swelling properties,porosity,and in vitro degradation.The results showed that the addition of nHA significantly decreased the the mechanical performance,swelling ratio,and porosity of the scaffolds.Finally,the cytocompatibility of the CS-based scaffolds was evaluated using bone marrow mesenchymal stem cells(BMSCs).The results show that CS/cGO/nHA porous scaffold promoted the growth and proliferation of BMSCs through the synergistic effect derived from cGO and nHA.