2.2 Preparation of silk protein fibroin (SF) solution
The purified SF was prepared as described in Yan et al . (19). Briefly, SF was dissolved in lithium bromide (9.3 M), followed by dialysis against distilled water for 48 h before concentrating it using a 20 wt% poly(ethylene glycol) solution. SF solution of 16 wt% concentration was used for further hydrogel preparation.