| Electrohydrodynamic(EHD)technologies,mostly the electrospinning and EHD jet printing,have been widely studied in tissue engineering(TE)applications because they could fabricate nano to micro fibrous scaffolds that mimic the structures of native extracellular matrix with biopolymers in convenient and effective way.However,the common strategies for improving the physico-chemical properties of scaffolds were using the high toxic and volatile solvents or melting process to achieve specific spinning condition.The solvents with low toxic and low volatile properties were seldom studied for marginal process windows and methods to promote the functions of the scaffolds.Thus,it had great scientific meaningful to propose new strategies on utilizing the environment friendly solvents for fabrication of bio-mimic TE scaffolds with EHD technologies.In this thesis,it was taken the Polycaprolactone(PCL)and glacial acetic acid(GAC)as the matrix materials.The strategies from “green” solvent systems,polymer composites and equipment configurations were implemented to improve the biocompatibility of the PCL scaffolds basing on the characteristics and limitations of the low toxic and low volatile solvents in processing of EHD technologies.First of all,the water was used as an additive to increase the conductivity of the solutions.The effects of water on solution properties and fibers morphologies were investigated.The results showed that water could increase the conductivity and stretching strength obviously which yielded nano scale fibers.Then,the Strontium ranelate(SR)was firstly incorporated into the PCL fibers basing on this system to study the potential for local drug delivery.The drug existing status,release curve and biocompatibility were investigated.The results showed that the drug with amorphous status was homogeneous distribution in the fibrous scaffolds and the fibers with drug of 2% could sustain release for several days to promote the cell proliferation and osteogenic differentiation.Secondly,it was firstly to prepare PCL/Pluronics hydrophilic composite fibrous scaffold with single solvent of GAC.The effects of F127 on solution properties,fiber morphologies and cell reactions were investigated and the results showed that the blending of F127 decreased the solution viscosity and fiber diameters,but improve the wettability significantly.However,the scaffolds with F127 count less than 1% exhibited better cell adhesion,proliferation and spreading.Then,in consideration of the low volatile and high melting point of GAC,the surface porous fibers were firstly prepared by cryogenic electrospinning which replaced the traditional metal collector to cold plate basing on the fact that the polymer jet suffered phase separation to be solidified under cold temperature.And the effect of the surface topographical structure on osteogenesis of mesenchymal stem cells was also investigated.The results showed that,under the same condition,rough fibrous scaffold decreased the proliferation rate of cells,but it increased the differentiation of stem cells to osteoblasts and showed better alkaline phosphatase activity.Finally,a novel technology named as cryogenic EHD jet printing(CE-jetting)was developed by combined the EHD jet printing with cryogenic controller.The macro and micro morphologies of scaffolds build with this new method under high speed and low speed jet were well investigated.The results showed that this new technique could successfully prepared PCL scaffolds with the height about 3-5 mm and clearly side gap.Moreover,the resulting scaffolds exhibited alignment and nano roughness surface topography which was firstly reported on these kinds of technologies.As a conclusion,the functional fibrous scaffolds could be prepared by using low toxic and low volatile solvents under suitable conditions and methods.The proposed strategies in the studies were not only showing their friendly to environment and products,but also developing new technologies. |
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