Studies On The Hydrogelation Process Of Regenerated Silk Fibroin Solution

Compared with traditional wound dressings, hydrogel can directly contact with bodytissues, improve the micro environment of the wound, prevent microbial infection in vitro,inhibit fluid loss, transport oxygen to the wound urging epithelial cell growth, thus it canaccelerate capillaries’ proliferation. Quaternary ammonium salt cationic surfactants’ effectson the structure and performance of silk fibroin hydrogel during the gel formation werestudied in the current paper. A novel antibacterial silk fibroin hydrogel which could beformed instantaneously and reveal excellent elasticity were introduced. The reason whyand how quaternary ammonium salt cationic surfactants instantaneously induce silk fibroinhydrogelation was preliminarily explored expecting its using as medical dressings.Results showed that as gel accelerator, quaternary ammonium salt cationic surfactantswith both bromine and chlorine can trigger silk fibroin solution instantaneously turn toelastic fluid performing typical gel structure, and improve the fracture strain of thehydrogel to a certain extent. As the hydrophobic hydrocarbon chain stretches and theconcentration increases, it is available to the instantaneous hydrogelation of silk fibroin. Itseemed that the instantaneous formation of hydrogels was based on the strong hydrophobicand electrostatic effects, the two effects together induced the self-assembly of silkmolecule chains into micro-nanofilament structure and restrained the secondary structuretransition of silk fibroin from non-crystalline structures (random coil, a-helix) to crystalstructures (Silk I and Silk II). A great deal of water were stored in the hydrogels, this kindof structure would give hydrogels excellent elastic properties. As time went on,hydrophobic effect began to play a leading part inducing condensation of fibroin moleculesinto clusters, finally presented porous network structure which was similar to pure silkhydrogel.Quaternary ammonium salt cationic surfactant induced silk fibroin hydrogel has goodbiodegradation performance. Degradation usually occurred in amorphous area at first, andthen crystalline region began to disintegrate until the hydrogel structure completely shattered. Quaternary ammonium salt represented amorphous or metastable state in silkfibroin hydrogel, thus it could easily spread out and displayed obvious antibacterial effect,which provided basis for the research and development of in-situ antibacterial hydrogeldressings.The mechanism of silk fibroin hydrogel was further studied by adding cation andsurfactant into silk fibroin solution to see whether it could form hydrogel or not. From theresult we knew that the instantaneous formation of silk fibroin hydrogel was mainlyascribed to the synergistic effect of charge and surface tension. Once the small moleculewith positive charge and able to reduce the surface tension of water below40mN/m wasadded, silk fibroin molecules could unite and form gel network rapidly.