| In recent years, artificial blood vessels, artificial joints, heart valves, hernia patch and other substitutes have been used in clinical and fully demonstrated the great superiority of repairing organ damages, however, artificial bile duct was still significantly lagging behind. In medicine, the lesions of common bile duct after excision repair or reconstruction have been one of the main problems in the biliary tract surgery. According to the clinical needs, artificial bile ducts or substitutes have been given more and more attentions. Currently, the artificial bile ducts prepared with biological polymer materials for repair and reconstruction of bile ducts have become the hot spot of research in related fields.In this paper, researches made by us are as three aspects, included preparation of complex artificial bile duct with the non-degradable polymers, preparation of biodegradable bile ducts and support brackets and preparation of biliary stents by electrospinning method. Firstly, the complex artificial bile duct with polytetrafluoroethylene (PTFE) as the base material was prepared by plasma modification, heat treatment and coating process; after the animal experiments, it could meet the clinical requirements as a preliminary exploratory research. Then, the biodegradable artificial bile duct and the support bracket using polylactic acid (PLLA) and polycaprolactone(PCL) as materials were prepared by impregnation method and melt spinning. Finally, disordered and ordered PLLA/PCL composite fibrous scaffolds were prepared by electrospinning, the surface of fibrous scaffolds was modified, and the biliary epithelial cells were cultivated to assess the compatibility of scaffolds with cells. The main contents are as follows:1. Cold plasma technology was applied for the surface modification of porous polytetrafluoroethylene (PTFE) film to improve the hydrophilicity. The influences of treating gas,power and time on the surface roughness, chemical groups and hydrophilic were discussed.Studies found that, after plasma treatment, PTFE surface roughness increased in varying degrees,and the F/C ratios changed; after helium (He) plasma treatment, the oxygen groups were induced on the membrane surface which improved the surface activity of PTFE. Under the same conditions, He-plasma treatment could improve the hydrophilicity of PTFE membrane significantly.2. He-plama-treated PTFE mentioned above was grafted with acrylic acid (AAc), and the changes of the AAc-grafted PTFE on the surface properties were studied. The results showed that a hydrophilic layer was formed on the membrane surface, and the permanent oxygen-containing reactive groups were introduced on the surface to avoid the shortcomings of the instable surface properties of the plasma-modified membrane, and the hydrophilicity of the surface has been greatly improved.3. The artificial bile ducts with PTFE as the material were prepared through heat stretching,high temperature heat-setting, plasma treatment and fluorine rubber coating process. The crystalline properties, surface structures, contact angles, tube permeability and mechanical properties of different samples were tested, the results showed that plasma treatment on PTFE surface could effectively improve the bonding property and the hydrophilic property; the crystallinity of PTFE material changed after stretching and heat-setting procresses, and the tensile strength multipliedly increased; fluorine rubber coated on the plasma-modified PTFE tube could effectively closed the pores of the surface and weaken the water permeability; the tensile strength of the samples coated with fluorine rubber increased with the increasing coating thickness, and the elongation at break also increased.4. The complex-type artificial bile ducts mentioned above were implanted in the pigs to do the in-vivo animal experiments, and results showed that complex artificial bile duct after 90 days implantation still had a good tension and no bile sediments attached on the inside wall; pathology and transmission electron microscopy (TEM) showed no significant inflammatory changes occured in surrounding tissues; as the bile duct alternatives, there was no bile leakage and bile duct stenosis.5. The PLLA/PCL composite biliary stent and bile duct support bracket were prepared by impregnation method, melt spinning and fiber-weaving method. It was found that different mass ratio of PLLA and PCL influnced on the morphology, crystalline property, thermal and mechanical properties of PLLA/PCL blend samples. The compatibility of PLLA and PCL blends was not well,and the PCL content could affect the degree of crystallization of the blends. Thermogravimetric(TG) curves provided temperature range for melt spinning and the differential scanning calorimetry (DSC) tests. PCL was added to improve the toughness of the whole materials. And different stretching temperatures and draw ratios have great influnces on the fibers. The maximum radial force of the woven PLLA/PCL support bracket could be comparable to the currently used metal stents.6. PLLA/PCL disordered fibrous scaffolds were prepared by electrostatic spinning, the characterizations of fibers were tested and the cell compatibility experiment was done. The possibility of these fibrous scaffolds applied in the field of tissue-engineering bile duct was discussed. The mass ratio of PLLA and PCL in the spinning solution had great influences on the morphology of the generated sub-micron fibers. It also affected the crystallization of the composite fibers. The results of in-vitro degradation showed that the weight loss rate and the water absorption of the fibrous membrane reduced with PCL content increasing. After 30 days degradation, the fibers became messy, part of the fibers fractured and piled together.7, The surface modification of PLLA/PCL fibrous membrane improved the hydrophilic properties of the membrane surface. The results showed that, He-plasma-treated fiber surface became rough. After plasma pretreatment, the gelatin spreaded well on the fiber surface, and a mesh structure formed on the surface of the gelatin-grafted fibers. He-plasma-treated samples exposed to the air caused the introduction of oxygen and a very small amount of nitrogen on the surface; and gelatin-grafted fibrous membrane had amide bond formed on the surface. Dynamic contact angle data showed that the hydrophilicity of the modified fibrous membrane has been greatly improved. Cell compatibility experiments confirmed that the PLLA/PCL fibrous membrane was suitable for the growth of biliary epithelial cells, and the gelatin-grafted fibrous membrane was more conducive to the adhesion and growth of the biliary epithelial cells due to the hydrophilic improvement.8. Aligned PLLA/PCL fibrous scaffolds were collected by electrostatic spinning rotation method. The winding speed of the roller had great influences on the surface morphology of the electrospun fibers. With the improvement of the roller surface speed, the fibers arranged in order and the fiber diameters decreased gradually; the increasing winding speed significantly improved the degree of orientation of the ordered fibrous membrane in the crystalline region, and it affected the degree of crystallization of the fibers. With the winding speed increasing, the storage modulus of the fibers increased significantly, while the loss tangent decreased gradually. The degradation rate of the aligned fibrous membrane was lower than that of the static receiving fibrous membrane;under the same degradation time, the weight loss rate of the fibrous membrane reduced with the winding speed increasing. The cytocompatibility confirmed that the aligned fibrous scaffold could effectively simulate the structure and properties of the extracellular matrix, which was suitable for the growth and proliferation of biliary epithelial cells. Finally, the surface was modified by plasma treatment and gelatin grafting to improve the hydrophilic property, after the oxygen plasma pretreatment, gelatin was grafted onto the surface, and the modified fibrous membrane was with better hydrophilicity. |
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