Electrospinning Nanofiber Yarn Based On-Airflow Twisting And Its Application On Tissue Engineering

With the development of science and technology,fibers with diameters ranging from a few nanometers to several hundred nanometers can be processed through nanotechnology.Nanofibers can be reprocessed into continuous yarns andintegrated into the wider,more meaningful traditional textiles of the marketby using textile techniques to reprocess,such as weaving,knitting,and weaving,with higher value-added applications.In recent years,nanofibers have been widely used in tissue engineering,textile and garment fields due to their high specific surface area and porosity.In this paper,a new technology for continuous mass production of nanofiber yarns was presented,and the application of nanofiber yarn in tissue engineering was discussed.A double conjugate electrospinning system was designed regarding the problems of low output,poor continuity and mechanical properties in the process of preparation of electrospinning nanofiber yarn to achieve the controllable orientation,and continuous large-scale preparation of nanofiber yarns.The yarn forming mechanism of electrospinning nanofiber yarn was also studied by numerical simulation and experiment.By observing the morphology and testing the mechanical properties of the nanofibers yarn,the effects of the spinning principle,process andthe spinning parameters such as voltage and metal horn speed on the diameter and mechanical properties of the nanofibers yarn were analyzed,and the optimum spinning parameters were determined.The results showed that the yarn twist was uniform and had a good continuity as the voltage,the distance between positive and negative nozzles,the total flow rate of solution and the flow ratio of positive and negative electrodes were 18 kv,17.5 cm,3.2 ml/h and 5:3,respectively.In addition,it was found that the twist of nanofibre yarn and its strength and elongation increased with the increase of horn speed.Twisting mode was one of the important parameters affecting yarn quality.In traditional mechanical twisting,the strength of nanofibers is weak and the surface effect is large,as well as the direct contact between machine parts and fibers could cause fiber damage,which directly affects yarn evenness and yarn quality.However,air twisting could not only avoid this situation,but also had the advantages of low cost,high speed and environmental protection.In this paper,a new airflow twisting spinning method was proposed based on double conjugate electrospinning device and a nozzle twister was designed to twist nanofibre bundles through three-dimensional high-speed airflow in order to obtain nanofibre yarns with uniform twist and orientation alignment.The results showed that the regular three-dimensional high-speed rotating airflow was formed in the nozzle.The velocity increases with the increase of pressure whose distribution was approximately axisymmetric.The pressure at the entrance of the nozzle was the highest,and at the exit of the nozzle decreases rapidly to the minimum.With the increase of jet pressure,the twist of yarn increased,the strength and elongation at break also increased.The twist angle reached the maximum value of 73.9° when the injection pressure was 4×105 Pa.Thus,nanofibers yarns with different quality requirements could be developed via the designed double conjugate electrospinning system based on three-dimensional high-speed air twisting.There are orderly oriented nanofibers in the main tissues of organisms such as skeleton,blood vessel and tendon which is very similar to the alignment structure of fibers in nanofibers yarn,which makes electrospun fibers yarn had special advantages in biomimetic construction of tissue engineering scaffolds.Therefore,nanofiber fabrics had been prepared and applied in bone tissue engineering.Firstly,PLA/TSF nanofiber yarns were spun by conjugate electrospinning technology and weaved into multi-layer nanofiber fabrics.Then,biomimetic bone tissue engineering scaffolds with hierarchical structure were constructed by simulating body fluid(SBF)biomimetic mineralization.The results showed that the addition of TSF could induce nucleation and directional growth of hydroxyapatite mineral crystals(HA)on the surfaces of PLA nanofibers.As compared with non-mineralized nanofibers or mats,the mechanical properties of mineralized multi-layer nanofibers fabrics were significantly improved,with compressive modulus and strength increased by 32.8 and 3.0 times,respectively.Additionally,PLA/TSF nanofiber fabric bone biomimetic materials showed good blood compatibility.Biological experiments showed that the mineralized nanofabric composite exhibits the excellent cell compatibility,promotes cell proliferation and adhesion,and accelerates the differentiation of bone marrow mesenchymal stem cells into osteoblasts.In addition,the three-dimensional ordered hierarchical structure of nanofibers could provide a better biomimetic environment,which was conducive to the expression of osteogenic activity.Therefore,the nanofibers fabrics were expected to be the new bone repair materials in bone tissue engineering.Additionally,the application of nanofibre yarn in vascular tissue engineering was also studied.In order to imitate truly the structure and composition of natural blood vessel,nanofiber core-spun yarn was spun with nylon line as the core yarn,PLCL/TSF as the inner layer and PCL/TSF as outer layer based on airflow twisting electrospinning technology.The small-caliber vascular tissue engineering scaffold with tubular structure could be obtained by extracting the nylon line.The results showed that the PLCL/PCL/TSF nanofiber scaffolds had a compact double-layer structure,with an inner diameter of 700 nm and an outer diameter of 1.1 micron,and showed good mechanical properties.The tensile strength and burst pressure of the PLCL/PCL/TSF nanofibers scaffolds were 7±0.26 Mpa Mpa and 14590±254 mmHg,respectively.Cell experiments showed that the adhesion and proliferation of smooth muscle cells or endothelial cells could be accelerated by grafting of TSF via plasma-treated.It could be seen that this high biomimetic double-layer micro-caliber nanofibre tubular scaffold would be an excellent substitute material for human blood vessels.