Chemical modification of Bombyx mori silk with calcium‐salt treatment and subsequent glycerin triglycidyl ether crosslinking

Abstract

In this article, we propose a new modification method for obtaining porous silk fibers with excellent wet elastic resilience and flexibility. Bombyx mori silks were modified by calcium-salt treatment and subsequent epoxy crosslinking with glycerin triglycidyl ether. The effects of temperature, time, and catalyst (sodium carbonate) on the crosslinking reaction of the silk fibers were investigated, and the best conditions of reaction were determined as a temperature of 120 C, a crosslinking agent concentration of 7%, and immersion for 1 h with 2% Na 2 CO 3 solution before the crosslinking reaction. The change in the structure and the physical properties of the silk fibers after calcium-salt treatment and epoxy crosslinking was studied. Separating behavior of the microfibers occurred on the surface of the silk fiber after calcium-salt treatment, and a porous structure formed in the interior of the silk. This porous structure of the silk was enlarged by subsequent epoxy crosslinking, and accordingly, the moisture conduction of the silk fibers improved remarkably. The breaking strength, breaking elongation, and wet elastic resilience of the silk fibers increased evidently after modification, and the modified silks exhibited a better flexibility. The conformation of silk fibroin fibers changed from b sheet to random coil after calcium-salt treatment, whereas the b-sheet content in the silk fibers increased after subsequent epoxy crosslinking. The significant reductions in the crystallinity and crystalline sizes in the silk fibers after the crosslinking reaction indicated that the crosslinking reaction occurred within the crystalline region because the calcium-salt treatment increased the reaction accessibility.

Novel Applications of Silk Proteins Based on Their Interactions with Metal Ions

“…Additionally, silk fibers notably shrunk and curled after being treated with neutral calcium salts (e.g., CaCl 2 ) at specific concentrations, leading to the development of elastic silk materials [159,160]. The shrinkage and curling occur because Ca 2+ chelates with fibroin at the -OH of the serine side chain and the tyrosine side chain of SF macromolecular chains.…”

Prediction of the epichlorohydrin derived cytotoxic substances from the eluent of poly(glycerol glycidyl ether) films

“…The synthesis of the monomer GGE is generally based on the reaction between glycerol and ECH [11,12]. When the bond between oxygen and the least substituted carbon of ECH is attacked under acid or base, 1-2-chlorohydrin intermediates are formed, which undergo ring closure by base treatment companied with dechlorination.…”

“…Notably, the production does not require the oil-based bisphenol A, which is a key compound applied in the industrial synthesis of polyepoxides [9]. However, another oil-based substance, epichlorohydrin (ECH) remains an important precursor in manufacturing glycerol glycidyl ether (GGE), which is monomer for the synthesis of polyGGE via cationic ring-opening polymerization [10][11][12]. Although bio-based glycerol can be used as a renewable feedstock for ECH production [13,14], ECH residues and its organochloride derivatives are still toxic to cells and may limit the cell and tissue compatibility as well as biomedical applications of glycerol-based epoxy networks [15].…”