Dissolution of silk fibroin with calciumchloride/ethanol aqueous solution

Abstract

Fibroin was dissolved in a solution of calcium chloride and water (molar ratio 1:8) and a solution of calcium chloride, water and ethanol (molar ratio 1:8:2) which was made by adding 2 mol of ethanol to the former solution. Fibroin insoluble in the calcium chloride aqueous solution at 20 to 30 degrees C (approx room temperature) for 240 to 720 hr, but was dissolved in the solution to which ethanol was added. Such long-term treatment, however,involves cost problems. In order to cope with such problems fibroin was treated with a calcium chloride aqueous solution at 40 to 60 degrees C for 1 hr. The fibroin was dissolved to 0.7 to 3.3%. Treatment in the solution to which ethanol was added at 55 degrees C for 1 hr, resulted in complete dissolution, which was approximately 35 times more likely than with the calcium aqueous solution. Based on these results, the solution of calcium chloride, water and ethanol (molar ratio 1:8:2) was considered to be very promising as a solvent of bio-material fibroin, from a viewpoint of industrial application