Birefringent Silk Fibroin Hydrogel Constructed via Binary Solvent-Exchange-Induced Self-Assembly

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Biophysics

Background:

• Birefringent hydrogels are crucial for biomedical and optical applications due to their ability to control anisotropy.
• Creating hydrogels with tissue-like hierarchical structures and mechanical properties remains a significant challenge.

Purpose of the Study:

• To develop a novel strategy for producing birefringent silk fibroin hydrogels (SFHs) with controllable structures and properties.
• To investigate the self-assembly mechanism of silk fibroin in binary solvent systems for hydrogel formation.

Main Methods:

• A "binary solvent-exchange-induced self-assembly (BSEISA)" strategy was employed using silk fibroin (SF) in an ionic liquid solution.
• Molecular simulations were used to evaluate the efficacy of different solvents (methanol, formic acid, water) in promoting beta-sheet formation.
• The self-assembly process was controlled by manipulating the solvent exchange rate to influence SF conformation and orientation.

Main Results:

• The BSEISA method successfully produced transparent and birefringent SFHs with a stable 3D network structure.
• Methanol was identified as a highly effective solvent for driving beta-sheet formation, which acts as physical cross-links.
• The mechanical properties of the resultant hydrogels closely resemble those of soft biological tissues like cartilage and lens.
• Experimental observations of birefringent fringes correlated well with finite element analysis of stress distribution.

Conclusions:

• The BSEISA strategy offers a controllable method for fabricating advanced birefringent silk fibroin hydrogels.
• These hydrogels exhibit promising mechanical and optical properties, making them suitable for mimicking biological tissues.
• The developed hydrogels are valuable for applications in tissue engineering and as models for studying mechanical responses in biological systems.