Effect of nano titanium dioxide on mechanical properties of regenerated silk

Abstract

Silk and spider silk have excellent mechanical properties, and their superior physical properties are closely related to their complex structure. Here, we reported the wet spinning behavior of nanomaterials mixed with silk proteins and study the effect of the different sizes of TiO2 nanoparticles (NPs) on the mechanical properties of regenerated silk. Our study retained silk protein nanofibers in CaCl2-FA solution, and optimized the wet spinning process, and produced high-quality regenerated silk fiber (RSF) with excellent mechanical properties by using TiO2 NPs. Among them, when the TiO2 NPs of 5-10 nm was 4 mg/g(TiO2 NPs/Silk Fibroin(SF)), the tensile stress of the RSF reached at 312.44 ± 20.31 MPa, which is 113.11% higher than the control group; the tensile strain reached 46.55 ± 2.76%, which is 152.85% higher than the control group. And the secondary structure conformation of RSF tended to transform from silk I to silk II, and its β-sheet content was 47.27 ± 0.25%. We found that the mechanical properties of RSF decreased with the size of TiO2 NPs increased. This may be due to the smaller the size of TiO2 NPs and the larger the specific surface area, which can provide more binding sites between TiO2 NPs and silk proteins, and also transformed the RSF conformation from silk I to silk II. The characteristics of this spinning method are simple operation, environmentally friendly, low cost, and large-scale industrialization potential. The method of producing RSF has great potential in the production of textiles and multifunctional materials.