*2.5. Stability of GZ2 in Aqueous Solutions*

The stability of cross-linked fibers in aqueous solution was studied by taking GZ2 as an example. Specifically, GZ2 was cut into a 2 × 0.5 × 0.2 cm<sup>3</sup> shape (20 mg) and placed in a bottle containing 10 mL phosphate buffer saline (PBS, 0.01 M, pH = 7.2–7.4). Then, the bottles were placed in the oven at 37 ◦C and recorded every 24 h. The experiment was done in triplicate.
