Preparation And Characteristics Of Chitosan Electrospinning Fibers

The nanofibrous prepared by electrospinning had drawn great interest in multiple biomedical applications because of their properties are unique when compared with fiber produced by conventional methods, such as larger specific surface areas and smaller pores. It had been suggested that very high surface area-to-volume ratio and high porosity can be achieved for better cell incorporation and perfusion. Coaxial electrospinning would provide an alternative and simple method to encapsulate drugs to deliver a biomolecular drug in a sustained fashion. Chitosan(CS) was the second most abundant natural polysaccharide in the world. It was widely studied because of its biological properties, such as biodegradability, bioactivity and antibacterial properties. Hydroxyapatite (HAp) was the clinically established material for the repair and reconstruction of hard tissues because of its inherent osteoconductive behavior and its ability to integrate with bone.In this thesis, nanofibrous biocomposite scaffolds of chitosan, poly(vinyl alcohol)(PVA)and hydroxyapatite(HAp) were prepared by electrospinning. The fiber diameter and tensile strength increased with an increase in nanoHAp content. The increase in tensile strength may be attributed to an increase in rigidity, because HAp is typical of hard inorganic phases. Higher percentage loading of HAp might have resulted in integrating of the nanoHAp powder in the CS/PVA matrix, because failure of the composite materials usually occurs at the interface of the polymer and the HAp. Furthermore, HAp with N-carboxyethyl chitosan (CECS)/PVA scaffolds was obtained via amineralization method with electrospun nanofibrous CECS/PVA scaffolds as an organic matrix. The amount of mineral phase increased with increase of incubation time, whereby a continuous mineral layer was formed on the scaffold surface after 25 days. Cell culture SEM imaging showed that the mouse fibroblast(L929) grew on the surface of nanofibrous structure, and the cell morphology and viability were maintained.Core-shell structured chitosan/ PVA- poly(propylene carbonate)(PPC) fibers were prepared by coaxial electrospinning. The results indicated that the use of chloroform/DMF (1/1) mixed solvents could avoid agglomeration of polymer at the capillary tip during coaxial electrospinning process, and contributed to good morphology. The SEM and TEM observation indicated that the diameter of the CS/PVA(core)-PPC(shell) fibers amounted to about 300nm, whereas the diameter of the core region was about 60nm. The core-shell structure could clearly been seen with a sharp interface between the core and shell fiber. To improve the water resistance of CS-based nanofibers the electrospun fibers (CS/PVA) were crosslinked by the incorporation of photocrosslinking agent poly(ethyleneglycol)-600-dimethacrylate (PEGDMA) and photoinitiator 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-1-propanone (HEPK) into the spinning solutions and a subsequent irradiation by UV light. The water resistance of photocrosslinked CS-based nanofibers was improved obviously and the swelling ratio decreased with the increasing content of PEGDMA/HEPK. When the concentration of crosslinking agent was 20wt%, the swelling ratio value decreased to half of that in none crosslinking CS/PVA nanofiber membranes, further increase concentration of crosslinking agent to 50wt%, the swelling ratio value was one eighth of the none crosslinking CS/PVA nanofiber membranes.