Dissolution of Bombyx mori Silk Fibroin in the Calcium Nitrate Tetrahydrate−Methanol System and Aspects of Wet Spinning of Fibroin Solution

Abstract

There are still several problems associated with the spinning of dialyzed silk fibroin solutions. In this work some of these problems have been examined. The calcium nitrate tetrahydrate-methanol system was used to dissolve the silk fibroin. A compositional phase diagram was constructed at various concentrations of the solvent system. Regenerated fibroin powders from undialyzed fibroin solution in several coagulants showed different conformations. Regenerated powders from several coagulants except methanol and ethanol were resoluble in water. Atomic absorption analysis revealed that the calcium cations strongly interact with fibroin molecules in dialyzed fibroin solution, which may interfere with the regeneration of a strong fiber. Kinetic studies to determine the diffusion coefficient of methanol into dialyzed and concentrated fibroin solution were reported. The properties of both original and regenerated fibroin such as solubility in water and thermal behaviors using DSC were compared. Regenerated fibroin fiber was spun by the wet spinning method. An X-ray diffractogram showed that the regeneration process decreased the crystallinity of regenerated fibroin fiber. SEM images of the surface and cross section of the regenerated fibroin fibers were discussed.

Non‐bioengineered silk gland fibroin protein: Characterization and evaluation of matrices for potential tissue engineering applications

“…On 70% (v/v) ethanol treatment the Tg peak shifts to 105.878C. Due to presence of b-sheet conformation in the ethanol treated films, there was absence of any exothermic peaks as previously seen in case of untreated amorphous films (Ha et al, 2003). It was noteworthy that with ethanol treatment there was subsequent increase in the degradation onset temperature from 142 to 1748C (increase by 328C).…”

Gelation behavior of Antheraea pernyi silk fibroin

“…With the effect of hydrophobic interaction, Ca 2+ promotes the formation of the -sheet construction and results in shorter gelation times for the Ap-SF solution. However, higher concentrations of Ca 2+ generate a large number of binding ligands between Ca 2+ and Ap-SF due to that the oxygen atoms of the carbonyl groups in the peptide bonds of fibroin form coordination bonds with calcium ions, and the water molecules act either as a swelling agent for the silk fibroin or as components of the coordination bonds [34,35], which interferes with the aggregation and the formation of the -sheet structure of Ap-SF and even completes the solvation sheath of the ions, resulting in dissolution of the silk fibroin. This supports the observation that dense salts of Ca 2+ , e.g., Ca(NO 3 ) 2 , could be used to dissolve Ap-SF silk fiber [15,17], and the solution obtained before dialysis for removing the ions is quite stable and will not become denatured or form a gel.…”

Influence of organic solvents on the structural and thermal characteristics of silk protein from the web of Orthaga exvinacea Hampson (Lepidoptera: Pyralidae)

“…The conformational characteristics of the films are influenced by many factors such as the concentration of the solution, the type of solvent, and the drying temperature [16]. The secondary structural characteristics of fibroin can be influenced by low dielectric organic solvents that convert random coils of silk fibroin into a β-sheet conformation [17][18][19][20]. It was reported that methanol had improved the mechanical properties of silk fibroin film.…”