Sarkar Sandip, Burriesci Gaetano, Wojcik Adam, Aresti Nicholas, Hamilton George, Seifalian Alexander M
Centre for Nanotechnology, Biomaterials & Tissue Engineering, UCL Division of Surgery & Interventional Science, University College London, London, UK.
J Biomech. 2009 Apr 16;42(6):722-30. doi: 10.1016/j.jbiomech.2009.01.003. Epub 2009 Feb 27.
Long-term patency of expanded polytetrafluoroethylene (ePTFE) small calibre cardiovascular bypass prostheses (<6mm) is poor because of thrombosis and intimal hyperplasia due to low compliance, stimulating the search for elastic alternatives. Wall porosity allows effective post-implantation graft healing, encouraging endothelialisation and a measured fibrovascular response. We have developed a novel poly (carbonate) urethane-based nanocomposite polymer incorporating polyhedral oligomeric silsesquioxane (POSS) nanocages (UCL-NANO) which shows anti-thrombogenicity and biostability. We report an extrusion-phase-inversion technique for manufacturing uniform-walled porous conduits using UCL-NANO. Image analysis-aided wall measurement showed that two uniform wall-thicknesses could be specified. Different coagulant conditions revealed the importance of low-temperature phase-inversion for graft integrity. Although minor reduction of pore-size variation resulted from the addition of ethanol or N,N-dimethylacetamide, high concentrations of ethanol as coagulant did not provide uniform porosity throughout the wall. Tensile testing showed the grafts to be elastic with strength being directly proportional to weight. The ultimate strengths achieved were above those expected from haemodynamic conditions, with anisotropy due to the manufacturing process. Elemental analysis by energy-dispersive X-ray analysis did not show a regional variation of POSS on the lumen or outer surface. In conclusion, the automated vertical extrusion-phase-inversion device can reproducibly fabricate uniform-walled small calibre conduits from UCL-NANO. These elastic microporous grafts demonstrate favourable mechanical integrity for haemodynamic exposure and are currently undergoing in-vivo evaluation of durability and healing properties.
由于顺应性低导致血栓形成和内膜增生，膨体聚四氟乙烯（ePTFE）小口径心血管旁路假体（<6mm）的长期通畅性较差，这促使人们寻找有弹性的替代品。壁孔隙率有利于植入后移植物的有效愈合，促进内皮化和适度的纤维血管反应。我们开发了一种新型的基于聚（碳酸酯）聚氨酯的纳米复合材料聚合物，其中包含多面体低聚倍半硅氧烷（POSS）纳米笼（UCL-NANO），该聚合物具有抗血栓形成性和生物稳定性。我们报告了一种使用UCL-NANO制造均匀壁多孔导管的挤出相转化技术。图像分析辅助的壁测量表明，可以指定两种均匀的壁厚。不同的凝固剂条件揭示了低温相转化对移植物完整性的重要性。尽管添加乙醇或N，N-二甲基乙酰胺会导致孔径变化略有减小，但高浓度乙醇作为凝固剂并不能使整个壁具有均匀的孔隙率。拉伸测试表明移植物具有弹性，强度与重量成正比。所达到的极限强度高于血流动力学条件下预期的强度，由于制造过程存在各向异性。通过能量色散X射线分析进行的元素分析未显示管腔或外表面上POSS的区域变化。总之，自动垂直挤出相转化装置可以从UCL-NANO可重复地制造均匀壁小口径导管。这些弹性微孔移植物在血流动力学暴露方面表现出良好的机械完整性，目前正在进行耐久性和愈合特性的体内评估。
