Effective sericin-fibroin separation from Bombyx mori silkworms fibers and low-cost salt removal from fibroin solution

Abstract

Silk from Bombyx mori has two main proteins: fibroin and sericin. Fibroin is a protein that exhibits good biocompatibility and high surface reactivity, desirable properties for many biomedical applications. Sericin is related with adverse immune response in some medical uses. Therefore, its removal (degumming) is desirable in almost all fields, including the textile industry and biological applications. In this study, three degumming methods (distilled water, liquid neutral detergent and sodium carbonate solution) were evaluated using Raman spectroscopy. Degummed silk treated with sodium carbonate solution exhibits a pattern consistent with previous studies for sericin-free fibroin, and significant differences with the untreated silk pattern. Also, degummed fibroin fibers were dissolved in a calcium chloride solution, in pursuit of a more versatile material. Additionally, different porous membranes of dialysis tubes were tested to remove residual salts, and were compared by conductivity measurements and EDS analysis, identifying good performance for an affordable food cellulose membrane. The results showed that it is possible to obtain fibroin with adequate chemical properties, using low-cost process and membrane of dialysis tubes.

Sustainable Silk-Based Particulate Systems for the Controlled Release of Pharmaceuticals and Bioactive Agents in Wound Healing and Skin Regeneration

“…The early attempts to employ SS in biomedical engineering failed due to immunological response and cytotoxicity [ 85 ]. This phenomenon was later attributed to a lack of suitable extraction and purification techniques [ 86 ]. Until recently, SS was regarded as a byproduct of the textile industry, with tons of leftovers produced each year since the chemical oxygen demand and SS content of the silk degumming wastewaters may be as high as 60 g/L and 30 g/L, respectively [ 87 ].…”

Versatile Potential of Photo-Cross-Linkable Silk Fibroin: Roadmap from Chemical Processing Toward Regenerative Medicine and Biofabrication Applications

“…Studies have indicated that sodium carbonate dissolved in boiling water is the most commonly used method for degumming silk for biomedical applications. Silk fibers which have been degummed are generally dissolved in inorganic salts such as high concentrations of LiCl, LiBr solution, , NaSCN solution, ZnCl 2 solution, or in a ternary solvent mixture comprising CaCl 2 /ethanol/water. ,,, Salts such as these are also capable of breaking hydrogen bonds, ultimately disassembling the β-crystalline structure of degummed silk. Purification is carried out by dialysis against water and removing salts and impurities in order to obtain pure SF .…”

“…Silk fibers which have been degummed are generally dissolved in inorganic salts such as high concentrations of LiCl, LiBr solution, , NaSCN solution, ZnCl 2 solution, or in a ternary solvent mixture comprising CaCl 2 /ethanol/water. ,,, Salts such as these are also capable of breaking hydrogen bonds, ultimately disassembling the β-crystalline structure of degummed silk. Purification is carried out by dialysis against water and removing salts and impurities in order to obtain pure SF . Moreover, SF can be extracted and stored in lyophilized form for long-term storage and, later on, can be dissolved in organic solvents such as HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) and formic acid to produce SF scaffolds in different forms including fibers, gels, or sponges.…”

“…Extracting SF from silk glands or silkworm cocoons can be accomplished in several ways. A key step in this process involves removing sericin from the cocoons (“degumming”) and subsequently dissolving and purifying them. , There are numerous ways that the SF can be degummed, including by acids, , alkalines, soaps, , amines, , enzymes, , urea, sodium carbonate, , ultrasonication, , autoclaving, carbon dioxide (CO 2 ) supercritical fluids, , and boiling, all as shown in Figure . In Table , we provided a list of some of the advantages and disadvantages of each degumming approach.…”

“…Purification is carried out by dialysis against water and removing salts and impurities in order to obtain pure SF. 64 Moreover, SF can be extracted and stored in lyophilized form for long-term storage and, later on, can be dissolved in organic solvents such as HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) 78 and formic acid 79 to produce SF scaffolds in different forms including fibers, gels, or sponges.…”