Effect of silk degumming on the structure and properties of silk fibroin

Two different silk fibroin samples were obtained by the Na₂CO₃ and urea degumming methods of silk fibers in the same fiber dissolution system, respectively. The molecular weight and viscosity of the fibroin samples were analyzed by the methods of SDS-PAGE, rheological, and etc. Then, different silk fibroin membranes (SFMs) and blank microspheres were prepared, and the effects of degumming methods on the silk fibroin were studied via analyzing the differences of SFMs and blank microspheres of the two samples. The experimental results showed that the viscosity of fibroin solution was positively correlated with its molecular weight. The fibroin prepared by the Na₂CO₃ degumming was lower than the one prepared by the urea degumming in the viscosity of the fibroin solution under the same mass concentration. Degumming with Na₂CO₃ exhibited the obvious effects on the thermal stability and mechanical properties of SFM, tensile strength decreased almost 10% and breaking elongation reduced more than 50%. Blank microspheres prepared from silk fibroin degummed with the different methods showed different particle sizes and its distribution. The microspheres prepared from silk fibroin degummed with the Na₂CO₃ had the smaller particle sizes and more concentrated distribution compared with those with the urea.