| The tissue engineering is the interface of myriad research areas including polymerchemistry, materials science, cell and molecular biology, and clinical medicine. At the baselies three components, a scaffold, cells, and soluble factors, and each plays a pivotal part inthe healing and regeneration process. The main role of the scaffold is to provide a structurallyrelevant3D environment that defines the shape of the tissue and allows the cells to adhere. Anideal scaffold there is some characteristics that it must have. It must be highly porous to allowcell penetration. Cellular penetration is critical for tissue ingrowth to occur. On the other hand,the goals of creating a highly porous environment, and using a biocompatible andbiodegradable material are just steps toward the ultimate goal of regenerating the function.Biomimetic scaffolds assist in this goal by reproducing the structure of the naturalextracellular matrix (ECM).The past decade has seen increasingly rapid advances in the field of biodegradablepolymer fibers. Large surface area to volume ratio, flexibility, rate of bio-resorption andhighly permeable properties are some of the advantages that make fibers potential in tissueengineering applications. The technique of electro-spinning has been extensively employed togenerate scaffolds. The nano-scaled and nonwoven structures of electro-spinning fibers withtheir inherent porosity and random arrangement can mimic the extracellular matrix, which ishighly critical for any in vivo tissue engineering applications. However, the average pore sizeobtained is less than1μm and is much smaller than the actual cell size (5–20μm), thus, thelack of penetration of the cells into the nanofibrous scaffolds was inevitable. Moreover, thetoxicity of the solvent used for electro-spinning scaffolds or mats restricted the application formany tissue-engineering applications.Thus, in this study, we were motivated to attain higher pore sizes to facilitate infiltrationand cellular in-growth, while keeping the solvent free. In this work, a cotton-like nonwoven fibers of Poly (lactic acid)(PLA) were fabricated successfully using the centrifugalmelt-spinning device. The effects of the centrifugal melt-spinning parameters on the fibersdiameter distribution were investigated. The physical and mechanical properties, and the cellcompatibility were then studied. Following，the Gelatin/PLA fiber composite scaffolds werefabricated by using the centrifugal melt-spinning PLA fibers. The physical and mechanicalproperties, the cell compatibility and in vivo implantations were studied.1、A cotton-like nonwoven PLA fiber was fabricated by melt spinning for tissueengineering. In this study, ultrafine and cotton-like PLA fibers were successfully fabricated bycentrifugal melt-spinning which is a novel technology to produce nonwoven fiber andscaffold. The processing of centrifugal melt-spinning PLA fiber as well as centrifugal speedswere investigated to analyze the effect of process variables on the properties by the methodsof differential scanning calorimetry (DSC)，Scanning electron microscopy (SEM)，Fouriertransform infrared spectroscopy (FTIR). In addition, the preliminary studies of fibers for cellcompatibility were conducted. We found that the centrifugal speed range from350to1500rpm which were satisfied the need of melt spanning. The centrifugal melt spinning fibers wascotton-like, extensive diameters distribution and three-dimensional structure. The diametersand mechanical properties of the novel PLA fiber are subject to being manipulated bycentrifugal speed and raw material properties. The fiber diameter distributions fall within thenanometer-to-micrometers range. The average diameter of the most finest ones in all sampleswas3.47±3.48μm and the other extreme ones was12.98±16.95μm. In addition, the fibersproduced by our method has lower cytotoxicity and higher proliferation then theelectro-spinning specimens，while there is no significant difference between the centrifugalmelt spinning fibers.2、The preparation and characterization of Gelatin/PLA fiber composite scaffoldsfabricated by using the centrifugal melt-spinning PLA fibers. The preliminary studs providethe centrifugal melt-spinning PLA fibers，and then the Gelatin/PLA fiber composite scaffoldswere prepared by solvent fumigation and surface coating method. The processing of PLAfiber composite scaffolds as well as fumigation time and density of PLA fiber wereinvestigated to analyze the effect of process variables on the properties by the methods of Scanning electron microscopy (SEM) and mechanical testing The porosity of scaffold werecharacterized by ethanol displacement method, and the preliminary studies of PLA fiberscaffolds for cell compatibility were conducted. In addition, The Gelatin/PLA fiber compositescaffolds was immersed into simulated body fluid for3d,5d and7d, respectively.The surfacemorphology of samples were observation by ESEM, quality changes was measured by TGA,Ca and P content of samples were detected by ICP-OES, and evolution process of crystalstructure was investigated by means of XRD method for different immers times. We foundthat the solvent fumigation time range from60min to90min which were satisfied the need ofscaffold preparation. The minimum density of PLA fiber should be0.15g/cm3which have themost advantage of cell permeability. In addition, the minimum concentration of gelatin shouldbe0.5%.3. In vivo implantation of the Gelatin/PLA fiber composite scaffolds. The Gelatin/PLAfiber composite scaffolds were implanted into the bone defect space of rabbit to evaluate thecapacity of bone repair materials. After the postoperative0w,2w,4w,6w,9w and12w,X-ray detection of the amount of bone formation. For the animal test, there was rapid healingin the defects treated with Gelatin/PLA fiber scaffolds and pure PLA fiber scaffolds. |
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