In the present work, high-resolution magic angle spinning (hr-MAS) NMR spectroscopy is applied as a straightforward nondestructive technique to quantify unreacted methacrylamide functionalities in cross-linked gelatin hydrogels. By adjusting several cross-linking parameters including the ultraviolet (UV) irradiation time and the photo-initiator concentration, the cross-linking degree can be easily varied. Remarkably, under all experimental conditions typically applied for hydrogel development, no more than 40% of the methacrylamide moieties present have reacted. The hr-MAS based approach to determine the cross-linking efficiency is shown to provide an innovative and more convenient alternative to the well-established classical techniques. In addition, the results obtained are in good correlation with mechanical analysis data.
Vol. 5, Iss. 14 Virtual Journal for Biomedical Optics
Sandra Van Vlierberghe, Bernd Fritzinger, José C. Martins, and Peter Dubruel, "Hydrogel Network Formation Revised: High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance as a Powerful Tool for Measuring Absolute Hydrogel Cross-Link Efficiencies," Appl. Spectrosc. 64, 1176-1180 (2010)