Induction Of Nano-pores Structure In Silk Biomiatcrials And The Effects On Tissue Repair

The structure and morphology of biomaterials at the nanoscale have an important impact on the mechanical properties,biocompatibility,and degradation properties.Among them,because of controlled degradation,no inflammatory reaction,and good mechanical properties,silk fibroin has been prepared into a variety of biological materials and applied in the field of biomedicine.Nano-pores structure have been extensively studied in drug delivery,and tissue engineering,especially for those with diameter of less than 100 nm,therefore having significant size,surface effects,and improve material permeability and cell adhesion.Although there have been methods for preparing silk fibroin nano-pore structures,most of them require the use of chemical reagents as porogens,and there are problems with a large pore size distribution range and residual reagents.Therefore,it is of great research value to develop green,safe and efficient methods for preparing nano-pores.In this paper,through the synergistic effect of temperature and pressure,such as autoclaving(121℃,20 min),and by controlling the pH,concentration,molecular weight and other conditions of the silk fibroin solution,silk fibroin solution containing nanoparticles was prepared;wherein the diameter of the nanoparticles had a range distribution of 50-300 nm,and the fibroin protein showed a random coil-dominated structure.The preparation of the nanoparticle-contained silk fibroin solution does not involve organic solvents,and can be directly used for preparing various silk fibroin materials without additional purification treatment.After drying the autoclaved silk fibroin solution(pH 7.4)at room temperature to form a film,and through adopting different water-insoluble treatment methods,a nanoporous structure with 50-300 nm was successfully formed in the film.Subsequently,the mechanical properties,in vitro degradation,permeability,and biocompatibility of the films were tested,and it was found that the nano-porous structure could significantly improve the permeability of the silk fibroin films,and at the same time,its mechanical properties did not decrease significantly.Cell experiments showed that the nano-porous films could better support cell growth and proliferation when compared with the plan silk film(control).The pH 7.4 silk fibroin solution after autoclaving was freeze-dried to fabricate a soluble sponge,and then induce the β-sheet structure with polyethylene glycol(PEG 400)to make a water-insoluble scaffold(ASF-PEG-S).By controlling the silk secondary structure,the nano-pores with a diameter of 50-300 nm could be prepared on the wall of silk sponge.Subsequently,the microporous and nano-pores sponge had high water absorption capacity(about 40 times)and excellent shape recovery.When human fibroblasts were inoculated on ASF-PEG-S and were cultured for 11 days,it was found that cell attachment,distribution,and growth consistency were improved as compared to those on the regular silk sponge without nano-pores,indicating the potential applications of nano-pores silk sponges in tissue engineering and tissue repair.Finally,the nano-pores films and sponges were applied to rats for repairing the full-thickness defects.The results clearly demonstrated the ability of nano-pores films and sponges in promoting angiogenesis and wound healing,again suggesting the future applications in the field of tissue engineering and tissue repair.In summary,silk fibroin solution containing nanoparticles with different sizes were prepared by synergistic methods of high temperature and high pressure.According to the needs of different tissues,biodegradable materials with different mechanical properties,microstructures and forms were constructed,which laid the theoretical and material foundation for the application of silk fibroin in different tissue engineering.