Preparation And Properties Of SF/PLA Composite Nanofibrous Membranes

On account of improving the mechanical properties of silk fibroin(SF) and meet the different need of structures of different tissue engineering scaffold fields. First of all, random regenerated silk fibroin/poly-L-lactide blend nanofibrous membranes were prepared via electrospinning, and then it was treated with methanol. The morphology、structure、thermal properties and mechanical properties of blend nanofibrous membranes were characterized and tested then. The results show that the diameter of the fibers increased with the addition of poly-L-lactide, and the thermal properties and mechanical properties of the blend fibers were improved effectively. The diameter of blend nanofibrous membranes increased after treatment with methanol and the secondary structure of regenerated silk fibroin changed from random to order after treatment of methanol. The methanol treatment improved the mechanical properties of blend nanofibrous membranes significantly.For the sake of further improving the mechanical properties of regenerated silk fibroin/poly-L-lactide blend system and meanwhile preparing the nano-fibers with a certain orientation to meet the mechanical properties and structure requirements of different tissue engineering scaffolds, a surface modified Multi-walled carbon nanotubes was made into regenerated silk fibroin/poly-L-lactide composite nanofibrous membranes via electrospinning, using a rotating mandrel. The effects of fiber orientation、MWNTs reinforcement and methanol treatment on the mechanical properties of the blend system was study. The results show that the fiber was significantly aligned, the diameter of the fibers decreased and the orientation increased with the collector speed increased. The diameter of the fibers with0.1%MWNTs decreased and the orientation increased slightly under the same speed, and also observed the alignment of MWNTs along the fiber axis. The diameter increased after the methanol treatment and it will lead silk change into β-sheet conformation. The thermal properties and mechanical properties of the composite nanofibrous membranes both were improved with the alignment of the fibers and the MWNTs contents increased.The article also explored a different spinning process path that aligned regenerated silk fibroin/poly-L-lactide shell-core structured composite nanofibrous membranes were prepared by coaxial electrospinning, using a rotating mandrel. The effect of morphology and mechanical properties of the composite nanofibrous membranes were discussed by the core、shell concentration and the collector speed. The results show that the diameter of the fibers increased with the increase of single core or shell spinning solution content. The fiber was significantly aligned and the diameter of the fibers decreased with the collector speed rising to2000rpm. The typical shell-core structure of the composite nanofibrous membranes would be found by observing the images of TEM and fracture surface SEM. With the fibers becoming aligned, the tensile strength of the composite nanofibrous membranes increased obviously, but the failure strain decreased.Finally, prospecting that how to control the mechanical properties of the tissue materials, especially understanding the the mechanics performance of the materials, and meanwhile considering the complex application environments of the membrane materials (one-way or two-way equivalent stress, two-way unequivalent stress and the stress is not stable, etc), this article preliminary attempted to a biaxial stretching method, and introduced the working principle of the new biaxial tensile test by analyzing the mechanical properties simply. The paper choosed the five kinds of matching (100/0,75/25,50/50,25/75,0/100) of electrospun SF/PLA blending nanofibrous made above to analyze the biaxial mechanical properties under two-way equivalent stress and research the biaxial mechanical response behaviors of the electrospun membrane materials in cyclic load by using the biaxial tensile instrument equipment. The results show that with the PLA content of the SF/PLA blending system increased, the tensile strength and failure strain of the biaxial direction both increased. When the ratio of50/50of the SF/PLA membrane materials was stretched by three times, we found the biaxial tensile stress-strain curve of biaxial direction of the SF/PLA membrane materials showed obvious inelastic and nonlinear characters.