Study On Surface Modification And Biocompatibility Of PHBV Cartilage Tissue Engineering Scaffolds

Articular cartilage,one of the most vulnerable tissue,is limited with the self-repair ability.Tissue engineering aims to reconstruct the physiological functions of damaged cartilage by constructing cartilage in vitro.Therefore,tissue engineering is expected to provide a new therapeutic method for clinical repair of articular cartilage defects.Scaffold material is the foundation of tissue eng ineering,for it not only provides structural support for the active cells,but also plays a role in the template to guide tissue regeneration and contr ol tissue structure.So it is important to study and develop suitable scaffold materials for cartilage tissue engineering.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV),a natural bacterial polyester,has good biocompatibility,biodegradability,thermal stability and mechanical properties and is widely used in the field of tissue engineering as the scaffold material.However,PHBV is hydrophobic and lack of cell recognition reaction sites on the surface,which seriously affect the cell adhesion,growth and proliferation.Surface modification is an economical and effective method to improve the biocompatibility of materials.In this study,the surface modification of PHBV was performed by the excellent hydrophilic natural biological macromolecule poly(?-glutamic acid)(?-PGA)and hyaluronic acid(HA)to improve the surface activity and biocompatibility of PHBV.Electrospinning technique was used for the preparation of PHBV fibrous scaffold.Then the surface modification of PHBV electrospun fibrous scaffold was performed firstly by introducing free amino groups,which provided reaction sites for the furth er immobilization of ?-PGA and HA macromolecules.The results of FTIR showed that 1,6-hexanediamine,?-PGA and HA modified PHBV fibrous scaffolds were successfully achieved.Determination of the ninhydrin method results revealed that the surface amine group density on PHBV increased with the increase of aminolysis time,and reached its maximum at 50 minutes.The morphology observed by SEM showed that PHBV fibrous scaffolds prepared by electrospinning has a smooth surface without obvious beads defects and its fiber diameter unif ormly distributed,furthermore PHBV fibers diameter slightly increased after the immobilization of ?-PGA and HA macromolecules,but there is no significant difference between them.Water contact angle measurements demonstrated that the water contact angle significantly decreased after immobilization of ?-PGA and HA,indicating that the hydrophilicity of PHBV scaffolds obviously improved after surface modification with hydrophilic natural biological macromolecule.TMA test proved that the ultimate tensile strength and Young's modulus of PHBV fibrous scaffolds modified with ?-PGA were significantly improved.The cell culture in vitro results illustrated that PHBV-grafted-?-PGA fibrous scaffolds could obviously promote bone marrow mesenchymal stem cells attachment while the fibrous structure of PHBV-grafted-HA scaffolds is in favor of adhesion and growth of chondrocytes.The Alamar Blue assay manifested that the PHBV fibrous scaffold modified by ?-PGA significantly promoted the proliferation of stem cells in vitro and which grafted with HA could obviously improve the proliferation activity of chondrocytes.In summary,the physicochemical properties and biocompatibility of PHBV fibrous scaffolds were effectively improved after immobilization of ?-PGA and HA natural bioactive macromolecules.Therefore,the ?-PGA and HA modified PHBV fibrous scaffolds are expected to be applied in the field of cartilage tissue engineering.