Fabrication And Properties Of The Electrospun Polylactide/Silk Fibroin-Gelatin Composite Tubular Scaffold

Fabricating small-diameter tubular scaffold for tissue engineering blood vessel is a hot research currently.Electrospinning technology could obtain nanoscale to microscale diameter fibers,the fibers can provide a biomimetic environment with high surface area to volume ratio and porosity.There are particular advantages to develop tissue engineering blood vessel via electrospinning,because it not only can provide a biomimetic environment,but also could perform a tubular structure with a needed diameter by adjusting the diameter of the mandrel-type collector.In this thesis,a composite tubular scaffold of PLA fibers(outer layer)and silk fibroin(SF)-gelatin fibers(inner layer)was fabricated by multi-electrospinning using a rotating mandrel-type collector,i.e.,first SF-gelatin and then PLA were sequentially electrospun(PLA/SF-gelatin).Firstly,the author researched the influence of different technical parameters,such as quality ratio,concentration,rotating speed,etc,on the morphology,porosity,microstructure and water-dissolved rate of the SF-gelatin tubular scaffold,and fix on the optimum technical parameters of electrospun SF-gelatin layer. Secondly,the morphology,porosity,biomechanical properties of the PLA tubular scaffold affected by concentration,roataing speed,wall thickness,and ethanol treating,ets,were investigated,and the optimum conditions of the electrospun PLA layer were fixed.Finally, the PLA/SF-gelatin composite tubular scaffold was fabricated with the optimum technical parameters via electrospinning.Morphological and biomechanical properties of the composite scaffold were examined,in particular,the biocompatibility of the scaffolds were evaluated in vitro and in vivo by means of cell culture,hemolysis test and subcutaneous implantation test.The results showed as follows:The optimum technical parameters of electrospun SF-gelatin(quality ratio 70:30)layer and PLA layer were set as follows(listed in the order of voltage,polar distance,flow rate and mandrel rotating speed):(a)SF-gelatin:30kV,13cm,0.2ml/h and 1000 revolutions per minute(rpm);(b)PLA:25kV,15cm,0.1 ml/h and 2000rpm.The electrospun PLA/SF-gelatin composite scaffold possessed a porous structure and excellent biomechanical properties,all the tensile strength,burst pressure strength and suture retention strength of the composite scaffold reached the criterion for vascular graft.After ethanol treatment,the biomechanical properties of the composite scaffold increased remarkablely,and the scaffold could dissolve in the water hardly.Both 3T3 mouse fibroblasts and human umbilical vein endothelial cells(HUVECs)can adhere,grow and proliferate on the composite scaffold. The hemolytic rate of the composite scaffold was 3.2%,which fulfils the need of hemolysis test on biomaterials.The subcutaneous implantation test showed that there were fewer macrophages and lymphocytes were observed,which indicated that the composite scaffold could induce minor inflammatory reactions in vivo.The test results show that the electrospun PLA/SF-gelatin composite tubular scaffold presents appropriate characteristics to be considered a candidate scaffold for tissue engineering blood vessel.