Probing Silk Fibroin Micro-Gel Nanostructure

The nanostructure of SF µgels was examined with a cold field emission Scanning Electron Microscope (SEM Jeol JSM-7500FA, Tokyo, Japan). Briefly, SF µgels were dehydrated in graded ethanol series (50, 70, 90, 95, and 100%), then transferred into a critical point dryer (CPD, K850WM, Quorum Technologies, Lewes, UK) and rinsed 5 times with CO₂ under supercritical conditions. Samples were mounted onto conductive carbon tape, gold-sputtered, and examined using an accelerating voltage of 10 kV. Fiber and pore dimensions were quantified on SEM images using ImageJ (https://imagej.nih.gov/ij/).
The chemical structure of SF gels was assessed by Fourier Transformed Infrared Spectroscopy (FTIR) performed on a Vertex 70 v FTIR (Bruker, MA, USA) equipped with a MIRacleATR accessory (PIKE Technologies, WI, USA). Spectra were measured in the range from 400 cm⁻¹ to 4000 cm⁻¹ with a resolution of 4 cm⁻¹ and a 64 scan-acquisition. Quantification of SF secondary structure (β-sheets content) was performed by the self-deconvolution of the Amide I region according to the literature [35 (link), 38 (link)].