Fabrication And Properties Of Biomimetic Composite Nano-fibrous Scaffolds By A Dual Phase Separation Technique

Fabrication of biomimetic nano-fibrous scaffolds has been attracted much interest recently because of their good performance in enhancing the cell adhesion, proliferation, differentiation and function expression. Collage, the most abundant extracellular matrix (ECM) protein in the human body, possesses a fibrous structure with fiber bundle diameter varying from 50 to 500nm. Hence, engineering nano-fibrous scaffolds mimicking the nano-fibrous ECM structure is good to the cell growth and tissue formation.To engineer a nano-fibrous scaffold with three-dimensional network structure, in this work, chitosan nano-fibers mimicking the natural ECM collagen fibers were prepared by phase separation. The diameter of chitosan nanofibers ranged from 50nm to 500nm, which can be regulated by changing the chitosan concentration, solvent concentration and phase separation temperature.Since CS nano-fibers scaffolds are not enough strong for bone tissue engineering application, in this work, a poly-L-lactic acid/chitosan composite nano-fibrous scaffold (PLLA/CSNF) was prepared by a dual phase separation technique. Firstly, a PLLA nano-fibrous scaffold with a fiber diameter of 50-500nm was fabricated via the first phase separation process. This scaffold was designed to provide good mechanical support. Secondly, CS nano-fibers were introduced into the pores of PLLA scaffold and formed three-dimensional network structure via the second phase separation process. The surface morphology, porosity and compressive modulus of PLLA/CSNF scaffold were characterized by scanning electron microscopy (SEM), density analysis and compression test respectively. The results showed that CS nano-fibers with a diameter of 50-500nm distributed in each pore and formed three-dimensional network structure. The PLLA/CSNF scaffold exhibited a high porosity of over 95% and a good compressive modulus of 146.6±25.3KPa, which may satisfy the general requirements of tissue engineering scaffolds, but can't meet the demand for bone tissue engineering application.In order to engineer a nano-fibrous scaffold suitable for bone tissue engineering, a new propylene carbonate/chitosan composite nano-fibrous scaffold (PPC/CSNF) with excellent mechanical properties was built via the same dual phase separation technique. The mechanical properties, porosity, in vitro degradation, minerization and biocompatibility of PPC/CSNF scaffold were investigated. The results showed that CS nano-fibers with a diameter size of 50-500nm homogeneously distributed in PPC scaffold interconected pores. An exciting compressive modulus up to 14.4±0.65MPa, was achieved as well as a high porosity of over 90%. The degradation data showed that PPC/CSNF scaffold exhibited an appropriate degradation rate with over 80% weight remaining after degradation for ten weeks. It was worthy to mention that PPC/CSNF composite scaffold also exhibited good cytocompatibility, which could promote the adhesion and growth of rabbit bone marrow mesenchymal stem cells. The implants and bone repair experimental results showed that PPC/CSNF composite scaffold had good histocompatibility and bone repair capacity. Therefore, PPC/CSNF is an excellent bone tissue engineering scaffold, which shows promising application in bone tissue engineering field.