| The natural valve leaflets are composed of fibrous layer,spongy layer and ventricular layer,of which the fibrous layer as the main structural layer and the bearing layer provide mechanical integrity for the valve.The ventricular layer structure is more flexible than the fibrous layer.And the spongy layer connects the fibrous layer and the ventricular layer together while acting as a cushion for shock absorption.Based on this,this study fabricated the micro-nanofiber membranes of biomimetic fiber layer and the biomimetic ventricular layer by electrospinning technology,and the biomimetic sponge layer was prepared by hydrogel.These two kinds of fibrous membranes were composited together by the adhesion of the hydrogel,which forming the fiber membrane/hydrogel composite scaffold with the three layers structure of "fiber membrane/hydrogel/fiber membrane".And the physicochemical properties,mechanical properties and cytocompatibility of each layer and the composite of the multilayer biomimetic structure fiber-based heart valve scaffold were tested and characterized.The relationship between the structure and properties of the composite was explored,and the induced regeneration performance of the composite scaffold was preliminarily explored.This study aimed to design a multilayer biomimetic structural fiber-based heart valve scaffold and implant the scaffold into animals subcutaneously to explore its regenerative inducing properties.The main research contents and conclusions are as follows:(1)PPDO fiber membrane and wavy and fluffy PPDO fiber membrane(PPDO-W-F fiber membrane)were prepared by electrospinning technology and post processing.The PPDO-W-F fiber membrane has a fluffy corrugated wavy fiber with bionic natural collagen fiber buckling structure,which caused the fiber gap increased,the water contact angle decreased to 93.16±7.06°,and the hydrophilicity improved significantly.The longitudinal tensile strength of PPDO-W-F fiber membrane increased to 5.31±0.32 Mpa,and the transverse tensile strength increased to0.25±0.02 Mpa,indicating that PPDO fiber membrane and PPDO-W-F fiber membrane have mechanical anisotropy and the latter has better mechanical properties.(2)PLGA fiber membrane was prepared by electrospinning technology,and PLGA gelatin blended fiber membrane(PLGA-GEL fiber membrane)was prepared by multi-channel cospinning method.The addition of GEL fiber in PLGA-GEL fiber membrane significantly reduced the water contact angle of the fiber membrane to 54.18±15.11°,and its hydrophilicity was effectively improved.The longitudinal tensile strength of PLGA-GEL fiber membrane is reduced to 7.03± 0.23 MPa,while the transverse tensile strength is significantly enhanced to 1.71±0.08 MPa.And the tensile strength of bionic fiber membrane is twice that of bionic ventricular fiber membrane.These results indicate that PLGA fiber membrane and PLGA-GEL fiber membrane have better tensile mechanical strength and can be used as biomimetic fiber layer to provide sufficient mechanical support for multilayer biomimetic structural fiber-based heart valve scaffold.(3)The COM-C composite scaffold with "PLGA/GEL/PPDO" structure was prepared based on PLGA fiber membrane and PPDO fiber membrane,and the COM-T composite scaffold with "PLGA-GEL/GEL/PPDO-W-F" structure was prepared based on PLGA-GEL fiber membrane and PPDO-W-F fiber membrane.And the thickness of the complex scaffolds were301.557±23.592 μm and 326.249±12.789 μm,which were in the range of natural valve thickness.The fiber membranes adhered by the hydrogel on both sides had good hydrophilicity.The radial tensile strength of COM-T in wet condition is 0.90±0.25 MPa,and the circumferential tensile strength is 1.26±0.54 MPa,both of which are significantly better than COM-C.In addition,the COM-T complex in the wet state has similar mechanical properties to natural valve tissue,which can meet the mechanical requirements of valve tissue engineering scaffolds.Also,The radial flexural stiffness of COM-T decreases to 0.13±0.05 m N·cm and the circumferential flexural stiffness decreases to 0.03±0.02 m N·cm under wet condition,showing better flexural elasticity.It illustrated that COM-T in the wetted state has the potential to be applied to prosthetic heart valve tissue engineering scaffolds.(4)After the two complexes COM-C and COM-T were implanted in rats,effective tissue regeneration and remodeling were formed at the implant sites,the tissue structure around the complexes was intact and no inflammatory tissues were observed.It means that the materials of the two complexes had good biocompatibility.After 30 days of embedding of the complex,more cells,collagen fibers and glycosaminoglycan components could be observed inside the complex,indicating that the cells and ECM components in the regenerated tissue could gradually infiltrate and grow into the complex with the increase of implantation time.Compared with the complex COM-C,the cells,collagen fibers and glycosaminoglycans inside the complex COM-T were more widely distributed,indicating that the looser and fluffier fiber membranes on both sides of the complex COM-T were more conducive to the infiltration of cells and ECM components.It is proved that complex COM-T has good structure-inducing regeneration properties,and can induce tissue regeneration to form a tissue structure similar to natural valve leaflets. |
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