Nuclear magnetic resonance. The 1 H NMR spectroscopy was used to confirm functionalization of collagen with FGE. Proton NMR spectra of collagen furan solution in D2O (1% (w/v)) was recorded using a JEOL JNM-ECP series FT NMR spectrometer at magnetic field strength of 9.4 T, operating at 400 MHz for 1 H NMR. Experimental conditions were as follows: 400 MHz, number of scans 20000, delay 600 s, and the spectrum was recorded at 45 °C to reduce line broadening.