Figure 3.

Proton Nuclear Magnetic Resonance (¹H NMR) spectra of hydrogels. (A): gelatin; (B): gelatin methacrylamide (GelMA); (C): hyaluronic acid (HA); (D): hyaluronic acid methacrylate (HAMA). Areas of interest are inset within each frame. Aromatic peaks in gelatin/GelMA are present at ~chemical shift ($\mathsf{\delta }$) 7.4 ppm, with the two free protons on the methacrylate groups present at $\mathsf{\delta }$ 5.6 and $\mathsf{\delta }$ 5.8 ppm respectively. In HA, the peak from the n-acetyl protons is present at ~$\mathsf{\delta }$ 2.1 ppm, with the methacrylate protons used for degree of functionalization (DOF) measurements present in HAMA at $\mathsf{\delta }$ 5.8 and $\mathsf{\delta }$ 6.3 ppm.