Effect of Woven Structure and Ratios of Warp and Weft Density on Water Permeability and Thickness of Woven Polyimide Vascular Grafts

Textile vascular grafts are often used to treat the cardiovascular diseases.Scholars continue to search for new materials for the development of vascular grafts with excellent properties,polyimide(PI)fiber is a material suitable for making vascular grafts with high strength,radiation resistance and stable property,as well as non-cytotoxic and satisfying blood compatibility.This study investigated the tensile strength and hydrolytic degradation properties of PI,polyester(PET)and nylon(PA).The results suggested that the PI is suitable for preparing vascular grafts.And influences of different weaves and ratios of warp and weft density on the water permeability,thickness and porosity of PI vascular grafts were analyzed.Vascular grafts with six weaves and two ratios of warp and weft density were designed and prepared.The surface morphology,permeability and thickness were characterized to optimize the structure of the vascular grafts.The results showed that the wall thickness of all the samples is less than 100μm except for the sample with the ratio 2∶3 and 1/3 twill pattern.Permeability is mainly determined by the weave and the ratio of warp and weft density.The samples in plain weave have the lowest water permeability compared with other samples.

A biomimetic basementmembrane consisted of hybrid aligned nanofibers andmicrofibers with immobilized collagen IV and laminin for rapid endothelialization

Rapid formation of a continuous endothelial cell(EC)monolayer with healthy endothelium function on the luminal surface of vascular implants is imperative to improve the longtime patency of small-diameter vascular implants.In the present study,we combined the contact guidance effects of aligned nanofibers,which enhance EC adhesion and proliferation because of its similar fiber scale with native vascular basement membranes,and aligned microfibers,which could induce EC elongation effectively and allow ECs infiltration.It was followed by successive immobilization of collagen IV and laminin to fabricate a biomimetic basement membrane(BBM)with structural and compositional biomimicry.The hemolysis assay and platelet adhesion results showed that the BBM exhibited excellent hemocompatibility.Meanwhile,the adhered human umbilical vein endothelial cells(HUVECs)onto theBBMaligned along the orientation of the microfibers with an elongated morphology,and the data demonstrated that the BBM showed favorable effects on EC attachment,proliferation,and viability.The oriented EC monolayer formed on the BBM exhibited improved antithrombotic capability as indicated by higher production of nitric oxide and prostacyclin(PGI2).Furthermore,fluorescence images indicated that HUVECs could infiltrate into the BBM,implying theBBM’s ability to enhance transmural endothelialization.Hence,theBBMpossessed the properties to regulate ECbehaviors and allow transmural ingrowth,demonstrating the potential to be applied as the luminal surface of small-diameter vascular implants for rapid endothelialization.

Conductive fibers for biomedical applications

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues.Thus,various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration,or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals.Benefiting from the outstanding advantages of flexibility,structural diversity,customizable mechanical properties,and tunable distribution of conductive components,conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment,in return to ensure stable functioning of such constructs during physiological deformation.Herein,this review starts by presenting current fabrication technologies of conductive fibers including wet spinning,microfluidic spinning,electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies.To provide an update on the biomedical applications of conductive fibers and fiber assemblies,we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration,implantable healthcare bioelectronics,and wearable healthcare bioelectronics.To conclude,current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Ultrastretchable and wearable conductive multifilament enabled by buckled polypyrrole structure in parallel

Stretchable conductive fibers have attracted much attention due to their potential use in wearable electronics.However,the ultrahigh strain insensitive conductivity is hindered by mechanical mismatch in Young’s modulus and failure of stretchable structures under large deformation.This challenge is addressed with a conductive and elastic multifilament made of the polyurethane monofilaments that are surface-coated with buckled polypyrrole(PPy)of which flexibility is improved by sodium sulfosalicylate.Such parallel conductive monofilaments with PPy buckling on surface reduce the influence of cracks in the conductive coating on the overall conductivity,displaying an ultra-high strain insensitive behavior(quality factor Q=10.9).Remarkably,various complex forms of wearable electronic textiles made by this conductive multifilament maintain the strain-insensitive behavior of the original multifilament,even upon the large deformation of human joint.This multifilament with wrinkled PPy has attractive advantages in the application of super-stretched wearable electronic devices.

人工血管与药物

人工血管的成功取决于多种因素,包括材料的化学、物理性质和结构设计。本文通过回顾人工血管的历史发展和作者的一些工作,在一定程度上总结过去的经验,希望对人工血管的进一步发展能够有所帮助。