Preparation, Structure And Properties Of Two Kinds Of Biodegradable Composites

Biodegradable materials have excellent biocompatibility and physical-chemical properties. It has been extensively applied in the biomedical fields. In this thesis, we fabricated two types of biodegradable materials with natural biodegradable material (silk fibroin) and synthetic biodegradable aliphatic polyester-based materials (Poly(butylene succinate) and Poly(L-lactic acid).Silk fibroin hydrogel is a kind of medical materials with good biodegradability and biocompatibility. It has been widely used as a biomedical material in recent years. Its poor mechanical properties and thermal stability restrict its application in medical field. Therefore, we first fabricated silk fibroin hydrogel reinforced by nano-Fe3O4 particles. By blending nano-Fe3O4 particles with silk fibroin solution, the SF/nano-Fe3O4 composite hydrogel was prepared, and its properties and structures were characterized. A cylindrical SF/nano-Fe3O4 composite hydrogel was obtained. The composite were characterized by high porosity, which were favorable parameters for cell growth and proliferation. Microstructural analysis indicated that fibroin mainly has silk II structure in all types of silk fibroin hydrogel. The mechanical properties of SF/nano-Fe3O4 composite hydrogel were markedly improved with increasing the silk fibroin or nano-Fe3O4 content in the composites.PBS and PLLA are two kinds of synthetic biodegradable materials with good biodegradability and biocompatibility. It has been extensively applied in biomaterial fields. But pure PBS film is frangible and has low biodegradation rate. Meanwhile, PLLA has poor mechanical properties and thermal stability. In order to improve the properties of both PLLA and PBS, we fabricated ultrafine PLLA/PBS fiber non-woven by electrospinning, and studied its properties and structures. Furthermore, the influence of blend ratio, electrostatic voltage, collection distance, aperture of injector nozzle and flow rate on the spinnability of PLLA/PBS solutions and morphology of electrospun PLLA/PBS ultrafine fibers were investigated. An optimal electrospinning condition was obtained in producing uniform cylindrical fibers. The experimental results first showed that the mixture solution of PBS/PLLA has good miscibility, and the viscosity, compatibility and spinnability of the mixture solution increased with increasing the PLLA content. Second, the diameter of PLLA/PBS composite fibers was about 0.213-7.784μm. Along with the viscosity of spinning solution increasing, the composite fibers' average diameter increased from 0.41μm to 2.16μm, and the standard deviation of average diameter was also increased.Along with the increasing voltage, the composite fibers' average diameter was first increased and then decreased, but its standard deviation was first decreased and then increased. When the content of PLLA increased, the shape of fiber changed from beaded fibers to smooth fibers, but then high PLLA content made the morphology of the fibers worse. Under the technical parameters of blend ratio of 6:4, voltage of 30kv, needle-orifice of 1.2mm diameter, flow rate of 2.89 mL/h, electrode distance of 17cm, the electrospun ultrafine fibers had narrower diameter distributions and best morphology. FT-IR and TGA analysis indicated that there was no new chemical bond formed between the molecules of PLLA and PBS. The thermal stability of electrospun PLLA/PBS ultrafine fibers was markedly improved with increasing the PBS content in the composites. Mechanical test showed that along with the PLLA content increasing, the elastic modulus and tensile strength of composite film was increased, and the elongation and fracture toughness of film was also increased. When the blend ratio was 8:2, the composite film has the best mechanical properties.