Preparation Of Modified SF/PCL Nanofibrous Mats And Their Applications In Skin Or Bone Engineering

Part I Preparation and characterization of SF nanofibers,PCL nanofibers and SF/PCL nanofibersIt has been reported that the mechanical properties of neat silk fibroin?SF?electrospun nanofibers are not ideal,while SF/polycaprolactone?PCL?composite nanofibers showed excellent biological and mechanical properties.Therefore,in this part of the present study,SF,PCL and SF/PCL nanofibrous mats were prepared under the same electrospinning condition,aiming to compare their biomedical properties.Scanning electron microscope?SEM?images demonstrated that the three kinds of nanofibrous mats all had good morphology and three-dimensional structure.Besides,X-ray photoelectron spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?and X-ray diffraction spectroscopy?XRD?analyses confirmed the existences of SF and PCL in SF/PCL nanofibers,and suggested that compared with the SF molecules in pure SF nanofibers,the SF molecules in SF/PCL nanofibers had better crystallinity.In addition,tensile strength and water contact angle tests showed that compared to SF nanofibrous mats,SF/PCL nanofibrous mats possessed significantly improved mechanical properties and the same good hydrophilic surface.Furthermore,cytocompatibility tests indicated that normal human dermal fibroblasts?NHDFs?adhered and grew well on all the prepared mats.But,SF and SF/PCL nanofibrous mats seemed to be more conducive to cell adhesion,growth and proliferation,and no significant differences was observed between the two.In summary,this part of the research suggested that SF/PCL nanofibrous scaffold could be a good alternative when pure SF nanofibrous mats is difficult to efficiently prepared or high mechanical properties of nanofibrous scaffolds are required.Part II Preparation of CS/COL assembled SF/PCL nanofibrous mats using LBL technique and their applications in dermal wound healing of ratsDeveloping an ideal wound dressing material which could accelerate wound closure and achieve scarless wound healing was the ultimate goal of numerous researchers.In this part of the study,biomimetic silk fibroin?SF?/polycaprolactone?PCL?matrices were fabricated via co-electrospinning and positively charged chitosan?CS?and negatively charged type I collagen?COL?were deposited on the nanofibrous mats through electrostatic layer-by-layer self-assembly?LBL?technique.Scanning electron microscopy?SEM?images indicate that the average fiber diameter of SF/PCL nanofibers became larger and more and more irregular protuberances were observed on their surfaces with the increase of LBL bilayers.Besides,the chemical structure and composition investigations further verified the successful deposition of CS/COL.Additionally,tensile strength and water contact angle tests showed the LBL modified mats had enhanced mechanical properties and good hydrophilicity.Moreover,antibacterial assay and cytocompatibility tests pointed that LBL structured mats acquired excellent antibacterial activity and better ability to promote cell attachment,growth and proliferation.Finally,in vivo wound healing assay in rat models revealed that LBL structured mats could reduce the wound closure time,increase collagen production and mitigate excessive scar formation through TGF-?/Smad signaling pathways,which demonstrated the potential application of the nanofibrous mats in skin regeneration.Part III Preparation of SF/PCL nanofibrous mats with n Ti O₂/n HA interlayers via electrospraying and their effects on osteoblast differentiation of MC3T3-E1In order to prepare a barrier membrane for guiding bone tissue regeneration?GBR?with good antibacterial properties and osteogenesis ability,in this part of the study,silk fibroin?SF?/polycaprolactone?PCL?nanofibrous mats incorporating Ti O₂nanoparticles?n Ti O₂?interlayers and/or HA nanoparticles?n HA?interlayers were successfully fabricated combining electrospinning and electrospray techniques.Scanning electron microscopy?SEM?images indicate that n Ti O₂ and n HA adhered or embedded on the surface of SF/PCL nanofibers,thereby,the surface roughness and diameter of the fibers increased.Fourier transform infrared spectroscopy?FT-IR?confirmed the presence of Ti O₂ and HA in the prepared composite nanofibers,and suggested the improved crystallinity of them.And tensile strength tests showed that the introduction of n Ti O₂ significantly improved the mechanical properties of nanofibrous mats with n Ti O₂ interlayers,while contact angle test pointed that nanofibrous mats with n HA interlayers achieved better surface wettability.Besides,antibacterial tests suggested that n Ti O₂ imparted antibacterial properties to the prepared composite matrices.In addition,cytoskeletal staining images showed the good growth state of MC3T3-E1 cells on the surfaces of different mats.Finally,the results of alkaline phosphatase?ALP?activity staining,alizarin red staining,real-time quantitative polymerase chain reaction?RT-q PCR?and Western blotting experiments verified that the introduction of n Ti O₂ and/or n HA interlayers greatly improved the ability of SF/PCL nanofibrous mats to promote osteogenic differentiation of MT3C3-E1.It is noteworthy that compared to nanofibrous mats incorporating only n Ti O₂ or n HA interlayers,nanofibrous mats with both n Ti O₂ and n HA interlayers exhibited greater application potential in bone tissue regeneration.