Light Irradiation On The Dissolution Of Silk Fibroin And Its Film Formation Properties

Silk fibroin which consists of 18 kinds of amino acids is a natural silk produced by degumming silkworm cocoon.It is widely used in the textile field because of its good air permeability,high luster,and the advantages of softness.Fiber materials,scaffolds,membranes and other tissue engineering materials can be prepared using silk fibroin as a raw material.Membranes are among the most widely studied materials.Due to the poor mechanical properties of silk fibroin membranes,it is limited to its wide application.Therefore,in this paper,ionic liquids were used as solvents to dissolve silk fibroin by light irradiation.The aim was to find a suitable light condition and prepare a silk fibroin membrane with excellent properties.In this paper,the ionic liquid was used as a solvent,and the fibroin was dissolved by ultraviolet light at 254 nm,and the structure of the fibroin protein after dissolution was characterized.According to the X-ray diffraction pattern,the raw silk fibroin has an α-helix structure,and the silk fibroin with non-light irradiated is α-helix and β-sheet structure,while the silk fibroin with irradiated by light is only a β-sheet structure.This shows that light irradiation promotes the conversion of the structure of silk fibroin from an α-helical structure to a β-sheet structure.Different anions and cations in ionic liquids have little effect on the structure of silk fibroin.Under light irradiation,the dissolution rate of silk fibroin in the ionic liquid is accelerated and the solution viscosity increases.The peptide chain segments in the β-sheet structure of silk fibroin are well-arranged,and the adjacent segments are tightly bound by strong hydrogen bonds and intermolecular forces,which lays the foundation for the preparation of silk fibroin films with excellent properties.Using ionic liquid as a solvent,different light source distances,different irradiation times,and different wavelengths of light were used to irradiate silk fibroin,and appropriate light conditions were selected to prepare silk fibroin films with excellent mechanical properties.Compared with non-irradiation,based on the mechanical properties of silk fibroin film,when the light conditions were 254 nm,the light source distance was 11 cm,and the irradiation time was 6 h,the average rupture strength of the silk fibroin film was 21.73 MPa.Under this light condition,silk fibroin film has the best mechanical properties.Compared with non-irradiation,the swelling and thermal stability of the silk fibroin film were improved.XPS showed that the content of oxygen-containing groups on the surface of silk fibroin film increased after light irradiation,resulting in increased wettability.Therefore,proper UV irradiation of silk fibroin dissolves,and the prepared silk fibroin film has excellent performance and expands its application in the biological field.