Development of Nanotextiles for Vascular Graft Applications

Abstract

This study investigated the unique properties, fabrication technique and vascular graft applications of woven nanotextiles made from low strength nanoyarns, which are bundles of thousands of nanofibers. These nanoyarns were fabricated by a novel process wherein the electrospun fibers were captured and twisted by a rotating collector with unique design that provided a pressuredriven, localized cotton-wool structure in free space referred to as substrate-less electrospinning . The diameter of the nanoyarns (typically between 100-300 and#956;m) were tuned by changing the process parameters, which were well investigated in this study. In order to convert these nanoyarns to tubular nanotextiles by textile technology, the mechanical strength of the nanoyarns had to be further improved. This was achieved by a post processing technique (heat-stretching) which improved its crystallinity, resulting in higher tensile strength. However, the strength of nanoyarns were not strong enough for them to be processed into tubes via conventional textile machines. Hence, an innovative robotic system was developed to meticulously interweave nanoyarns in longitudinal and transverse directions, resulting in a flexible, but strong woven product. This is the only technique for producing seamless nanotextiles in tubular form from nanofibers. The porosity and mechanical properties of nanotextiles could be substantially tuned by altering the number of nanoyarns per unit area. Investigations into the physical and biological properties of the woven nanotextile revealed remarkable and fundamental differences from its non-woven nanofibrous form and conventional textiles. This enhancement in the material property was attributed to the multitude of hierarchically arranged nanofibers in the woven nanotextiles. This patterned woven nanotextile architecture lead to a superhydrophillic behavior in an otherwise hydrophobic material, which in turn contributed to enhanced protein adsorption and consequent cell attachment and spreading. Short term in vivo testin