Prepare Silk Fibroin

Silk fibroin is a protein secreted by silkworms and can be collected from cocoons. Known for its biocompatibility and durable mechanical properties, silk fibroin has been attracting attention from a variety of industries, from textile to medical engineering. How, then, is it prepared for industrial use after getting extracted from a cocoon? Read below to follow the steps of preparing silk fibroin for use!

1. Combine distilled water, calcium chloride, and ethanol together. The resulting solution is called an Ajisawa’s reagent.
2. Pack 5 g of degummed silk fibroin tightly into a 50 mL beaker.
3. Pour 20 mL of the Ajisawa’s reagent into the beaker, making sure the silk fibroin is completely submerged.
4. Place the beaker in the oven at 60°C for 4 hours or until all the fibroin has dissolved. 
5. Cut the dialysis tubing so that it fits into the beaker, and then hydrate it in the beaker containing the silk fibroin. Clamp one end tightly with a dialysis clamp.
6. Let the solution cool, then carefully pour the solution into the dialysis tubing and clamp the other end.
7. Dialyze against 1 L of distilled water.  Change the water after 1 hour, 4 hours, that evening, the next morning and night, as well as in the morning on the following day (six changes total within 48 hrs).
8. Place silk in a 50 ml conical tube. You may need to split it between two tubes if it is more than 40 ml, alternatively you can fill one tube and use a counterbalance of water.
9. Centrifuge to remove impurities.  Place in a centrifuge and spin at 9,000 r.p.m. (~12,700g) at 4 °C for 20 min.

The final product is a purified silk fibroin solution that is ready for industrial use!