Mechanisms of Silk Fibroin Sol−Gel Transitions

Abstract

Silk fibroin sol-gel transitions were studied by monitoring the process under various physicochemical conditions with optical spectroscopy at 550 nm. The secondary structural change of the fibroin from a disordered state in solution to a beta-sheet-rich conformation in the gel state was assessed by FTIR and CD over a range of fibroin concentrations, temperatures, and pH values. The structural changes were correlated to the degree of gelation based on changes in optical density at 550 nm. No detectable changes in the protein secondary structure (FTIR, CD) were found up to about 15% gelation (at 550 nm), indicating that these early stages of gelation are not accompanied by the formation of beta-sheets. Above 15%, the fraction of beta-sheet linearly increased with the degree of gelation. A pH dependency of gelation time was found with correlation to the predominant acidic side chains in the silk. Electrostatic interactions were related to the rate of gelation above neutral pH. The overall independencies of processing parameters including concentration, temperature, and pH on gel formation and protein structure can be related to primary sequence-specific features in the molecular organization of the fibroin protein. These findings clarify aspects of the self-assembly of this unique family of proteins as a route to gain control of material properties, as well as for new insight into the design of synthetic silk-biomimetic polymers with predictable solution and assembly properties.

Comparison of Gelation Time and Polyalcohol Effect on Hydrogels from Domestic and Wild Silk Fibroins

“…Pure A. pernyi SF can also gelate quicker than that of B. mori SF with 500 wt% PEG (gelation time is 103.1 h). The structure of the SF hydrogels was stabilized due to the formation of β-sheets, which served as physical cross-links [22,23]. A. pernyi SF is rich in amino acids having polarity and ionogenic pendant groups, which more easily forms reactions with other polar molecules and functional groups.…”

Synthesis and Properties of Silk Fibroin/Konjac Glucomannan Blend Beads

“…If the CH 2 OH and COOH do not participate in the hydrogen bonding, the domain of the random coil conformation should be increased. However, as results show through the increasing of β-sheet, such groups may participate in the intermolecular bonds with the NH group of SF [33][34][35]. …”

Vascular Implants Reinforced with Natural Silk Yarns

“…Many international scientific studies confirm the suitability of natural silk material in surgery and medicine [7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”