查看更多>>摘要：Despite continuous efforts to improve the robustness of cardiac valve implants,neither bioprosthetic nor mechanical valves fulfill both hemodynamic and durability requirements.This study discussed novel flexible leaflet designs,focusing on poly-meric materials with proven hemocompatibility,such as polyether ether ketone,of much higher stiffness than native tissue,aiming at optimal valve implants.A biomimetic valve with a single-curvature belly-curve(B-C)was used as a reference for new design variants with a double-curvature B-C with varying radii.Soft(13.2 MPa)and stiff(2.4 GPa)leaflet materials and different thicknesses were studied using lean simulations and in vitro experiments under physiologic hemodynamic con-ditions.The performance was assessed using opening pressure(OP)and orifice area(OA).The latter was determined by a newly developed automatized image processing tool.Experimental trends are in agreement with simulations and demonstrated that a buckling-inspired double-curvature leaflet design significantly enhances the trileaflet valve opening behavior,which is particularly advantageous for stiffer leaflet materials.Compared to the reference,the best-performing variant showed an OP improvement of 47％and 44％based on simulations and experiments,respectively.In contrast,the achieved mean pressure differential was directly comparable to state-of-the-art bioprosthetic valves.The OA was slightly reduced for new variants but still in the satisfying range.
查看更多>>摘要：The recovery and reconstruction of central nervous system function after spinal cord injury(SCI)is a worldwide problem.The difficulty lies in the feasibility issue of new axons passing through the injured area and the negative effect of scarring after injury.As a biological material,the human amniotic membrane(HAM)has the advantages of protecting nerve growth,inhibiting scar formation,and promoting neovascularization,but its weak physical properties are difficult to apply in treating SCI.In this study,HAMs were first decellularized and then chemically grafted with methacrylic anhydride.Next,the composite was photocrosslinked with gelatin methacrylate to prepare a cross-network biological complex.The final complexes prepared by appeal were used for in vitro and in vivo studies of SCI in rats,separately.In the in vitro experiment,the composite scaffold inherited abundant biological factors from the amniotic membrane and had the physical properties of a hydrogel,thus providing a favorable environment for the growth and development of neurons and blood vessels.In the in vivo experiment,the composite reduced scarring and promoted the growth of new nerves.Overall,the composite scaffolds can stably simulate the extracellular microenvironment in SCI defects,regulate pathological changes,and promote the generation of new neurons.Therefore,decellularized HAM hydrogels are promising biocomposite materials for central nerve repair after SCI.
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维普