Development Of Nanofiber Small-Diameter Vascular Grafts Loaded Photosensitizer

Co-existence drawback of all artificial blood vessels was that the problem of restenosis. Despite there have done so many works, for examples, the choice of polymer materials, the improvement of processes, the use of antiproliferative agents and anti-clotting drugs, but still couldn't overcome the problem, So that the new strategies and methods need to been proposed.This subject combines with nanotechnology, modern textile technology and Photodynamic Therapy (PDT). The photosensitizer was loaded into the nano fibers evenly. The free radicals which was produced by PDT could diffuse feely in the nano fibers while the polymer materials degrading. When a laser with certain wavelength irradiated the fibers, the free radicals would target to the thrombosis tissue, and eliminated the thrombosis tissue.In this subject, the preparation of small-diameter artificial blood vessels and the analysis of performance were the main researches. The polylactic acid (PLLA) has been choosen as the main material, because it was non-toxic, biocompatible, high strength and relatively slow degradation. Sub-porphyrin has been choosen as the photosensitizer, it was provided by Professor Chen Zhilong, Donghua University.Electrospinning was one of the most convenient ways that could produce nanoscale fibers directly and continuously. So that it has been choosen to make the loading system. A small-diameter (d=5mm) PLLA tubular scaffold containing Sub-porphyrin (0.1%) was fabricated via electrospinning which was performed on a high-speed rotating mandrel-type collector. The PLLA were dissolved in the mixture of chloroform and actone (2:1 in volume) to make evens spinning solution. Through the optimization of design and analysis, the optimal electrospinning parameters has been obtained:PLLA mass fraction of 5%, voltage of 20KV, spinning distance 15cm, solution extrusion rate of 1.1ml/h, pinhole diameter of 0.8mm, the rotating speed of 1000r/min.The influences of Surface Morphology by various Electrospinning parameters were researched in this subject. The morphology of the nanofibers was characterized by scanning electron micrograph (SEM) and digital camera photos. The nano fibers were Uniform thickness. There have no effects on spinning performance after loading Sub-porphyrin. Aligned fibers could be obtained by the high-speed rotation of the roller. Infrared spectroscopy (FTIR) analysis showed that photosensitizer and PLLA were good compatibility. Interaction wasn't occurred between the two in the spinning process. Differential scanning calorimetry (DSC) analysis showed that the drug has no effect on the thermal properties of nanofabric membrane before and after loading Sub-porphyrin. The good compatibility between photosensitizer and PLLA were further validated by DSC. The crystalline structure of the nanofabric membrane was characterized by X-ray diffraction(XRD). The XRD showed that the crystallinity of nanofabric was increased after loading the drug. It was conducive to the improvement of mechanical properties.The axial and radial strength of the electrospinning tubes of different thickness were tested. It showed that the strength was measured increased with increasing thickness. The porosity of the electrospinning tubes of different rotating speed were calculated. The results showed that the small-diameter electrospinning tube has good porosity, they were all more than 80%.Finally, the cancer cells were cultured on the nanofibrics membrane which was loading Sub-porphyrin, After a period of time, the cells were irradiated by a laser light with special wavelength. The morphology and death of the cells were compared before and after irradiating. The experimental results showed that the abnormal cells would be inhibited and killed through photodynamic therapy. So that it could be used in the treatment of restenosis.In summary, the small-diameter artificial blood vessel loading photosensitizer was prepared successfully. And the cell toxicity was verified through the cells experiments. A new approach to improve the patency of small-diameter artificial blood vessel was provided.