FTIR spectra (a), XRD patterns (b), CD spectra (c) and elastic modulus G' (d) of different silk nanofiber hydrogels. The samples were as follows: SN-H, silk nanofiber hydrogel; WA-SN-H, water-annealed silk nanofiber hydrogel; MA50-SN-H, 50% methanol-annealed silk nanofiber hydrogel; MA80-SN-H, 80% methanol-annealed silk nanofiber hydrogel.