Study On Photothermal Nanoparticles Functionalized Bombyx Mori Silk Fibroin Composites

Silk fibroin has excellent cell compatibility,biodegradability,and permeability,which can be made from waste silk and textiles,and is widely used in tissue engineering,biomedical,and other new materials.However,regenerated silk fibroin（RSF）materials have poor mechanical properties and low added value.Using wet spinning and tape casting methods,RSF materials with different functions were prepared by blending functional nanoparticles,which can not only improve the mechanical properties of RSF materials,but also offer them new functions and enrich their application value.At present,the research on the modification of RSF by two-dimensional nanoparticles（2D NPs）and the application of its composite materials in the photothermal fabrics and drug delivery of refractory wounds are novel fields,there are few studies,especially in the wet spinning process.In this thesis,the performance modification of RSF was studied by using the unique2D NPs（WS₂NPs,Mo S₂NPs,Fe Mo S₂NPs,and Mo O₂NPs）.Two kinds of photothermal fabrics and two drug release materials based on RSF/2D NPs were constructed.The high toughness mechanism of 2D NPs modified RSF fibers and the’silk house’inference in mechanical properties of different RSF materials were revealed.The main contents were as follows:1.Firstly,four kinds of high toughness RSF/2D NPs hybrid fibers were successfully fabricated by wet spinning.Among them,the breaking strength and elongation at break of0.04 wt%RSF/Mo O₂NPs hybrid fibers were the best,which were 311.62±10.52 MPa and153.81±6.21%,respectively.Their breaking strength was higher than that of RSF fibers（156.65±14.29 MPa）and close to that of natural silks（362 MPa）.More importantly,their elongation at break was much higher than that of RSF fibers（42.75±5.11%）,natural silks（21%）,and other hybrid fibers prepared by wet spinning.SEM showed that the 2D NPs had no obvious effect on the morphology of the hybrid fibers,and did not cause voids.The average diameter of the RSF/2D NPs hybrid fibers was larger than that of RSF fibers.The dispersion of 2D NPs might influenced on the mechanical properties of RSF fibers.2.Secondly,the high toughness mechanism of 2D NPs modified RSF hybrid fibers was revealed from three forms of RSF（RSF/2D NPs solution,RSF/2D NPs freeze-dried,RSF/2D NPs hybrid fibers）.It was found that 2D NPs limited the self-assembly movement of RSF chain and hindered the transformation ofα-helix/random coil toβ-sheet in RSF fibers,resulting in a decrease in the content ofβ-sheet and a corresponding decrease in the transformation ofβ-sheet toβ-crystal.As a result,the crystallinity andβ-crystal growth of RSF were limited and more uniform refined crystals appeared in unit volume.At the same time,the 2D NPs were easy to form hydrogen bonds with the RSF chain,so the 2D NPs could also act as a network node role similar to theβ-crystal,increased the crystal density of the fiberβ-crystal network.Such moreα-helix/random coil and more phase boundaries due to grain refinement endowed RSF hybrid fibers with greater plasticity resistance,and ultimately significantly improved the toughness of RSF/2D NPs hybrid fibers.3.The’silk house’hypothesis in the mechanical properties of different RSF materials was proposed.Firstly,the secondary structure of RSF materials had a great influence on their mechanical properties.Secondly,theβ-sheet（orα-helix/random coil）in RSF materials was not the more,the better.The mechanical properties of RSF materials could be optimized only when they maintained an ideal domain value.The ideal domain values of different types of RSF materials were different.Finally,during the preparation of different types of RSF materials,the factors and degrees of influence on the mesoscopic structure of RSF were different（including nanoparticles）.However,as long as the mesoscopic structure of the materials could be closed to the ideal domain value of this type of RSF material,nanoparticles could improve the mechanical properties of this type of material.4.Two kinds of RSF/WS₂NPs and RSF/Mo S₂NPs photothermal fabrics were constructed,which had broad application prospects for warm fabrics,especially in cold regions and military fields.Under simulated sunlight irradiation,the temperature of 2 wt%RSF/Mo S₂NPs hybrid fibers reached 98.60oC in 10 mins,and that of 0.8 wt%RSF/WS₂NPs hybrid fibers reached 108.30oC in 10 mins.TGA and DSC tests showed that the photothermal conversion efficiencies of RSF/WS₂NPs and RSF/Mo S₂NPs hybrid fibers were 2.78 and 3.97 times higher than those of RSF fibers,respectively,and both of them had good thermal stability.The RSF/WS₂NPs hybrid fibers were modified by 4 wt%UV329and 4 wt%K1010,which effectively improved their UV resistance and oxidation resistance,and made them easier to store.The RSF/Mo S₂NPs hybrid fibers and RSF/WS₂NPs hybrid fibers had antibacterial activity against E.coli and S.aureus.Finally,the temperature of RSF/Mo S₂NPs and RSF/WS₂NPs fabrics increased to 81.40oC and 116.80oC,respectively,after simulated sunlight irradiation for 10 mins.After 15 mins of natural sunlight in winter,the hand temperature of RSF/WS₂NPs fabrics reached 38.30oC,which was higher than that of pure RSF fabrics（26.40oC）and ambient temperature（12.00oC）.5.A kind of RSF/TH/Fe Mo S₂NPs composite fiber with antibacterial activity,good biocompatibility,and NIR responsive drug release function was constructed,which can be applied to new wound suture.The results of SEM and EDS showed that TH could uniformly adhere to the hybrid fibers.FTIR and WAXD results showed that TH did not destroy the secondary structure and crystal structure of RSF fibers,and its high toughness conformed to the toughening mechanism of hybrid fibers.When TH content was less than4 wt%,the composite fibers could maintain high toughness.The breaking strength and elongation at break of 2 wt%RSF/TH/Fe Mo S₂NPs composite fibers were 253.14±9.31MPa and 96.34±5.27%,respectively.Under simulated sunlight,2 wt%RSF/Fe Mo S₂NPs hybrid fibers reached 92.60oC in 10 mins.After irradiation by 2 W/cm²808 nm NIR for 5mins,the temperature of the hybrid fibers reached 130.30oC.The RSF/TH/Fe Mo S₂NPs composite fibers had NIR responsive drug release and long-term drug release characteristics.The sustained release time of the composite fiber in the buffer system（p H7.4）was 48 h,and the maximum cumulative drug release rate was 45.41%.Under NIR irradiation for 40 mins,the cumulative drug release rate was 51.46%,much higher than that of RSF fibers（29.74%）.The drug encapsulation efficiency of the composite fiber was97.67%,and the drug loading rate was 1.69%.These properties were suitable for drug burst release requirements in the general wound and specific clinical environments.The RSF/TH/Fe Mo S₂NPs composite fibers had antibacterial activity against E.coli and S.aureus.They had no toxicity to HSEC cells and 293T cells,and had good biocompatibility.The degradation residual rate of the composite fibers in PBS,simulated intestinal fluid,and simulated tissue fluid remained above 45%within 14 d,which was conducive to the long-term release of drugs.6.An RSF/TH/Mo O₂NPs composite film with antibacterial activity and multiple response drug release functions was prepared,which has great potential for application in refractory wound dressings.The results of SEM and EDS showed that TH could uniformly adhere to the composite films.FTIR and WAXD results showed that Mo O₂NPs promoted the formation ofβ-sheet structure in RSF/Mo O₂NPs composite films,and had higher crystallinity and larger crystal volume.The 0.8 wt%RSF/Mo O₂NPs composite films had the best mechanical properties.Its breaking strength and elongation at break reached10.92±0.63 MPa and 273.17±13.12%,respectively.Its toughness was equivalent to 1 m and could be stretched to 3.73 m.Under simulated sunlight,0.8 wt%RSF/Mo O₂NPs films reached 74.80oC in 10 mins.After irradiation by 2 W/cm²808 nm NIR for 5 mins,the 8wt%RSF/TH/Mo O₂NPs films reached 101.00oC,the temperature of 0.8 wt%RSF/Mo O₂NPs films reached 69.90oC.The RSF/TH/Mo O₂NPs films had NIR and p H sensitive controlled release and long-term drug release characteristics.The sustained release time of the composite films in the buffer system（p H 7.4）was 48 h,and the maximum cumulative drug release rate was 69.56%.Under NIR irradiation for 40 mins,the cumulative drug release rate was 72.76%,much higher than that of RSF films（52.27%）.The drug encapsulation efficiency of the composite films was 98.54%,and the drug loading rate was 7.50%.The drug release mechanism of the films was Fickian diffusion.The above properties made it controllable and long-term release of drugs in refractory wound tissues,thus promoted wound healing.Moreover,the composite films were successfully applied to the skin trauma experiment in mice.The RSF/TH/Mo O₂NPs films had antibacterial activity against E.coli and S.aureus.They had no toxicity to HSEC cells and 293T cells,and had good biocompatibility.The degradation residual rate of the composite films in PBS,simulated intestinal fluid,and simulated tissue fluid remained above 70%within 14 d,which was conducive to the long-term release of drugs.In summary,this study not only provided a theoretical basis for the mechanical modification of RSF materials,but also lent some support for its application in photothermal fabrics and drug delivery for refractory wounds.This broadened the application range of functional nanomaterials in textiles,offered reference for the high value-added development of RSF,and also reduced serious social problems such as resource waste and environmental pollution caused by waste silk products.