Biaxial stretching of polytetrafluoroethylene in industrial scale to fabricate medical ePTFE membrane with node-fibril microstructure

Abstract

Expanded polytetrafluoroethylene (ePTFE) is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties. However, ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect, which poses a major problem in industrial-scale fabrication. To solve this problem, we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides, so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched. The as-fabricated ePTFE membrane has, as designed, uniform thickness and node-fibril microstructure. In addition, we examine the effects of mass ratio of lubricant to PTFE powder, biaxial stretching ratio, and sintering temperature on the performance of the resultant ePTFE membranes. Particularly, the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed. Besides stable mechanical properties, the sintered ePTFE membrane exhibits satisfactory biological properties. We make a series of biological assessments including in vitro hemolysis, coagulation, bacterial reverse mutation and in vivo thrombosis, intracutaneous reactivity test, pyrogen test, and subchronic systemic toxicity test; all of the results meet the relevant international standards. The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated in industrial scale. Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.

Epithelial-Mesenchymal Transition of Cancer Cells on Micropillar Arrays

“…The interaction between cells and materials is a fundamental issue in the fields of biomaterials and tissue regeneration. − Micropillar arrays provide a unique kind of topological surfaces to regulate cell-material interactions. − Cell nuclei undergo severe deformation on micropillar arrays with an appropriate dimension, which influenced cell behaviors . Nuclear deformation can also cause chromatin condensation and chromosome relocalization within the nucleus and alter gene expression of the cells. − It has been demonstrated that actomyosin and microtubule may synergistically regulate nuclear deformation and chromatin remodeling, finally modulating gene expression .…”

Wet 3D printing of biodegradable porous scaffolds to enable room-temperature deposition modeling of polymeric solutions for regeneration of articular cartilage

“…Raw materials for tissue repair and regenerative medicine have been widely investigated [9], for example, polymers like poly (lactide-co-glycolide) (PLGA) [10][11][12][13], poly (lactic acid) [14,15], gelatin [6,16,17] and polytetrafluoroethylene [18,19], metals like iron [20][21][22], magnesium [23] and titanium [24], and other inorganic materials like calcium phosphate ceramics [25,26] and even carbon nanotubes [27]. The fabricating strategy should adapt to the nature of the raw Figure 1.…”