*2.3. Raw Materials Characterization* 2.3.1. FTIR Analysis

Fourier Transform Infrared Spectroscopy (FTIR) was used to characterize the presence of specific chemical groups in the VG-3D and VG-RGD hydrogels (Figure 1a). VG-3D and VG-RGD (300 µL) solutions were dehydrated using a freeze dryer (Labconco, FreeZone 2.5 Plus, Kansas City, MO, USA) for two days. VG-based material powders were analyzed and compared with sodium alginate powder. All FTIR spectra were obtained in the wavenumber range from 4000 to 600 cm−<sup>1</sup> during 64 scans, with 4 cm−<sup>1</sup> resolutions (Shimadzu IRAffinity-1, Duisburg, Germany). The FTIR spectra were plotted using OriginPro 8.5 (OriginLab, Northampton, MA, USA).
