| Micro-and nanostructures of biomaterials could effectively affect their physical,chemical and biological properties, such as mechanical strength, drug delivery, and theadhesion, proliferation and differentiation of tissue cells. In recent years, biomaterials withspecific micropatterns and functional surfaces have shown increasing potential in the field oftissue engineering. The electrospun nanofibrous scaffolds have similarity in morphology andfiber size scale with the native extracellular matrix (ECM). They possess high porosity, goodpore connectivity and high surface area. However, it still remains a significant challenge foraccurately controlling the alignment of the polymer fiber alignment due to their intrinsiclimitations, such as low dielectric constant and the extent of polymerization of the resourcepolymers. Thus, most of studies focus on the preparation of random or single directionalaligned nanofibers, and little effort has been devoted to the development of the nanofiberswith controllable and ordered architecture. In addition, it is unclear how the micro-andnanostructures regulates the physiochemical and biological properties of biomaterials. In thisdissertation, we set out to optimize the material categories and then fabricated electrospunnanofibrous scaffolds with controllable micropatterns. In addition, the physical and chemicalproperties, as well as cell adhesion, proliferation and differentiation of tissue cells on thesescaffolds were systematically investigated. Finally, different patterns of the scaffolds, as drugcarriers, were applied to study the controllable drug delivery. The following results wereachieved. (1) Fabrication and characterization of electrospun nanofibrous scaffolds with controllablepatterns and properties.By optimizing the material categories, the micro-patterned D,L-poly(lacticacid)/poly(e-caprolactone)(PDLLA/PCL) composite scaffolds were successfully fabricatedvia electrospinning. Then, the order degree and contractibility of the scaffolds with differentPDLLA/PCL ratios were investigated. The results showed that the order degree of themicropatterns and in vitro shrinkage behaviors of PDLLA/PCL electrospun scaffolds could befinely tuned by controlling blending ratios. The electrospun scaffolds PDLLA/PCL with aweight ratio of50/50showed the optimal properties with controllable pattern structure andstable dimensional structure for further study.Moreover, the PDLLA/PCL composite eletrospun nanofibrous materials with designedmicropatterns, dimensions, and different orientations were accurately fabricated throughdesigning and controlling the embossments and holes on the surfaces of collectors.(2) The investigation of the bioactivities of cells growing on electrospun nanofibrousscaffolds with different patterns, orientations and dimension.Various electrospun nanofibous scaffolds with controlled patterns, orientations anddimension were successfully fabricated. The adhesion, proliferation, distribution, anddifferentiation of human umbilical vein endothelial cells (HUVECs) in these scaffolds wereinvestigated. The results showed that the micro patterns of the scaffolds significantlyinfluenced the proliferation and distribution of the HUVECs. Comparing to the aligned ornon-woven fibrous surfaces, cells grew faster on the fibrous surfaces with micropatterns.Besides, cells could be guided by the surface structures of materials, which showed patterndistributions mimicking the surfaces of materials, and the distributions could be altered as themicro patterns of the electrospun nanofibous scaffolds changed.Furthermore, cell shapes, cytoskeletons and nucleus of HUVECs exhibit some extent ofpolarization on electrospun nanofibrous scaffolds with different orientations. On the interval regions of the double directional aligned electrospun patterns, the cell shapes, cytoskeletonsand nucleus showed largest degree of polarization along the orientation of the fibers. Incontrast, cells on the embossments of the double directional aligned electrospun patternsshowed much less degree of polarization and the polarity axis was random. Comparing to thenon-woven fibrous surface, cell differentiation was further enhanced on the patterned fibroussurface.The different dimensions of patterns on the electrospun nanofibrous mats could alsoaffect the proliferation and differentiation of HUVECs. The result showed that the cellproliferation and expression of vascular related genes were upregulated with the increasingdimensions of the unit pattern. Especially, the double directional aligned electrospun scaffoldswith an interval length of1500μm had the optimal cell proliferation and differentiation,indicating the potential application as scaffolds in blood vessel engineering.(3) Investigations of the hydrophobicity and drug release of the surfaces modified withdifferent electrospun nanofibrous patterns.The microstructures of electrospun nanofibrous scaffolds and the corresponding surfacehydrophobicity were systematically analyzed and summarized. The results showed that thewater contact angle of PVB films could be controlled over a large range (from80oto153.2o)by changing the density, distribution and the arrangement of the deposited electrospunnanofibers. These different patterned nanofibrous scaffolds were further applied as drugcarriers to control the drug release profile. The results showed that the hydrophobicnanofibrous surface could reduce release kinetic of drugs from the PVB polymer film, and thedrug release profile could be further tuned by changing the pattern arrangement of thenanofibers on the surface of the scaffolds.In summary, in this paper, electrospun nanofibrous scaffolds with various micropatternswere firstly fabricated from optimized polymers. Further studies showed that thephysiochemical, biological dang drug-delivery properties could be effectively regulated by controlling the micropatterns of the scaffolds. The possible mechanisms of these regulationsare summarized and further discussed, which could offer evidence to apply fibrouselectrospun scaffolds in biomedical engineering application. |
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