The effect of degumming conditions on the functionality of silk fibroin films

Abstract

Degumming with an aqueous alkaline solution, such as sodium carbonate (Na2CO3), is the initial step in purifying a silk fibroin (SF) aqueous solution from Bombyx mori silkworm cocoons. While essential for sericin removal, this process affects the molecular state of the SF, impacting factors such as the molecular chain length and weight distribution. In this study, we aimed to investigate the physical and biological properties of films prepared from different aqueous SF solutions obtained through degumming with Na2CO3 at various concentrations, followed by water solubilization and dialysis. Higher concentrations of Na2CO3 resulted in broader distributions of molecular weights in the purified SF aqueous solutions. An SF film containing a greater proportion of low-molecular-weight chains (below 100 kDa) exhibited a faster degradation rate and lower fibroblast adhesion compared with a film containing predominantly high-molecular-weight chains. In a rat abdominal adhesion model, the former inhibited postoperative adhesion, whereas the latter promoted adhesion at wound sites. These results highlight the importance of the initial degumming process in regulating the functionality of resulting SF products for medical applications. Aqueous SF solution is purified through degumming with Na2CO3 aqueous solution, followed by water solubilization and dialysis. In the preparation of SF film, the aqueous SF solution is cast into a mold and subjected to a drying process. Throughout this process, intermolecular interactions played a crucial role in film formation. The molecular state of the SF, including its chain length and molecular weight distribution, affected the properties of the resulting film.