| Electrospinning is a simple and effective processing technique to prepare the fibers with diameter ranging from nanometer to submicron.Due to its good connectivity,high porosity,and large surface area to volume ratio,electrospinning fibers can be widely used in biomedicine,catalysis,filtration and optoelectronic devices et al.However,the fibers prepared by the conventional electrospinning are randomly disordered,resulting in a small pore size of electrospinning scaffold,which is difficult to meet the different pore size requirements for different applications.It is very necessary to prepare the fiber scaffold with controllable morphology and structure.Appropriately reducing the working distance and voltage during the conventional electrospinning process,so that the electrostatic jet can move steadily in a straight line(also be called electrospinning in a direct-writing way),therefore the deposition position of fibers can be effectively controlled.In this paper,we studied the effects of various parameters during the electrospinning in a direct-writing way on the fiber morphology and deposition precision,and prepared several scaffolds with controllable structure,and then explored its feasibility as a drug release carrier and cell culture scaffold.The influence of process parameters on fiber morphology was systematically studied by using orthogonal experimental design.The results showed that the fiber diameter first increased and then decreased with temperature and needle size increasing,and the fiber diameter first decreased and then increased with flow rate increasing,and the fiber diameter decreased with collector speed increasing.The collector speed was the most influential factor and needle size was the least influential factor in determining the fiber diameter.The influencing factors affecting the position of fiber deposition during electrospinning in a direct-writing way were studied,and verified by electric field simulation and calculation that the main reason affecting the accuracy of fiber deposition was the local electric field changed by deposited fiber.Then two possible solutions were proposed.One was to deposit the fibers in a staggered arrangement,and the other one was to use a self-made composite collector to collect the fibers.The above two methods could improve the deposition precision of the fibers.The PEG/PCL/Cip composite fiber mats with different structures and ratios were prepared by blending method.The results showed that the water absorption increased with the PEG content increasing.The composite fiber mats exhibited obvious burst release in the initial stage,and the amount of burst release increased with the water absorption increasing.The release mechanism of the PCL/Cip fiber mat was non-Fick diffusion,and the release behavior was more consistent with the Hixson-Crowell model.While the release mechanism of PEG/PCL/Cip composite fiber mats were dominated by Fick diffusion,and its release behavior was more consistent with the Weibull distribution model.The composition of the composite fiber mats could not only change the release behavior of the drug,but also change its release mechanism,and the structure of the composite fiber mats could only change the release behavior of the drug,and has no effect on its release mechanism.The HA/PCL composite scaffolds with large pore size were prepared by layer-by-layer stacking to satisfy the growth of osteoblasts,and the pore size of the composite scaffolds were controlled by adjusting the spacing of the monolayer fiber mesh and the fiber stacking mode.The prepared scaffold exhibited good connectivity,and that the average pore size was 167 μm,which could meet the growth requirements of osteoblasts.The HA/PCL composite scaffolds had good biocompatibility in vitro and in vivo.The addition of HA could promote the proliferation and differentiation of osteoblasts.When the HA content is low,the adhesion between cells and composite scaffolds were realized by slab pseudopods.When the HA content is high,the adhesion mode was changed to filopodia.The degradation rate of the HA/PCL composite scaffold accelerates as the content of HA increases.In conclusion,this paper summarized the basic rules of affecting the fiber morphology during the melt electrospinning in a direct-writing way process,and analyzed the reasons that affect the accuracy of fiber deposition,and discussed the feasibility of electrospinning direct-writing fiber as drug release carrier and cell culture scaffold.It laid a solid theoretical foundation for the application of electrospining in a direct writing way in the field of biomedicine. |
