Electrospinning Of Polycaprolactone Nanofibrous Scaffolds By Using Ethylene Carbonate/Glacial Acetic Acid Solvent System

Polycaprolactone(PCL)has been widely used in tissue engineering because of its excellent biocompatibility and bioabsorbability.Solution electrospinning technology was usually utilized to fabricate PCL nanofibrous scaffolds which could mimic the structures of native extracellular matrix.However,the use of highly toxic organic solvents and the poor PCL solution stability hinder the development of the solution electrospinning process.At present,the use of low-toxic Glacial acetic acid(GAC)as a benign solvent for PCL by electrospinning could only obtain microfibers or beaded fibers.Thus,Ethylene carbonate(EC)as a low-toxic and low-volatile solvent was added into the PCL/GAC system and the PCL/GAC/EC solution was extremely stable to successfully prepare nanofibers.In the paper,the electrospinning studies were carried out from new solution system,the characterization of fiber scaffolds,the hydrophilic optimization of fiber scaffolds and the exploration of fiber scaffolds with macroscopic 3D structure.(1)PCL/GAC/EC solution was researched as the object.The relationship was established among them by measuring the properties of the solution,conducting the experiments of electrospinning process and observing the morphology of the electrospun fiber.It was found the solution properties were extremely stable to successfully fabricate the PCL nanofibrous scaffold.Then,the process parameters which affected the morphology of PCL fibers were studied in detail.(2)The difference in properties between the PCL nanofibrous scaffold and the PCL microfibrous scaffold were compared and analyzed.The results showed that the crystal configurations of both scaffolds were consistent and no GAC and EC remain on the surface of these scaffolds;the specific surface area of the PCL nanofibrous scaffold was increased by about 3.5 times,and the tensile stress of that was higher but tensile strain of that was smaller,in comparation with the PCL microfibrous scaffold;MC3T3-E1 cells on the PCL nanofibrous scaffolds exhibited a better enhancement on cell proliferation.(3)A small amount of Pluronic(F127)was blended in PCL/GAC/EC solution system to optimize the hydrophilicity of the PCL composite fiber scaffold.The results showed that F127 reduced the viscosity of the solution system and the electrospun fiber diameter was smaller;F127 existed in an amorphous form in the PCL composite fiber scaffold and improved the wettability of the scaffold.(4)The 3D fiber scaffold with a specific ‘honeycomb' was successfully electrospun under appropriate environmental parameters and process conditions.Based on the residual charge accumulation effect,the mechanism of the generation and evolution of the ‘honeycomb' was proposed.The effect of electrospinning time,the thickness of the scaffold and the content of EC on ‘honeycomb' were analyzed.The above conjecture was verified by directly changing the local electric field.