The extraction process takes 4 days. If lyophilized silk is required then an additional 3 days will be needed. Aqueous solutions can also be concentrated within an additional 24 hours. Aqueous silk solutions can be sterilized by a number of methods including sterile filtration, gamma irradiation, and autoclaving. Unfortunately, the more rigorous procedures, such as gamma irradiationand autoclaving (unpublished results), have been shown to degrade the molecular weight of the silk fibroin and therefore irradiation dosing or steam sterilization timing should be worked out for each system. In some cases, it is simpler to sterilize the final product before use. The preferred methods of sterilization for each material format will be noted within each protocol.
The purified silk can then be used for a variety of applications summarized in Figures 3--1111.