Functionalization of an Alginate-Based Material by Oxidation and Reductive Amination

This research focused on the synthesis of a functional alginate-based material via chemical modification processes with two steps: oxidation and reductive amination. In previous alginate functionalization with a target molecule such as cysteine, the starting material was purified and characterized by UV-Vis, H-1-NMR and HSQC. Additionally, the application of FT-IR techniques during each step of alginate functionalization was very useful, since new bands and spiked signals around the pyranose ring (1200-1000 cm(-1)) and anomeric region (1000-750 cm(-1)) region were identified by a second derivative. Additionally, the presence of C-1-H-1 of beta-D-mannuronic acid residue as well as C-1-H-1 of alpha-L-guluronic acid residue was observed in the FT-IR spectra, including a band at 858 cm(-1) with characteristics of the N-H moiety from cysteine. The possibility of attaching cysteine molecules to an alginate backbone by oxidation and post-reductive amination processes was confirmed through C-13-NMR in solid state; a new peak at 99.2 ppm was observed, owing to a hemiacetal group formed in oxidation alginate. Further, the peak at 31.2 ppm demonstrates the presence of carbon -CH2-SH in functionalized alginate-clear evidence that cysteine was successfully attached to the alginate backbone, with 185 mu mol of thiol groups per gram polymer estimated in alginate-based material by UV-Visible. Finally, it was observed that guluronic acid residue of alginate are preferentially more affected than mannuronic acid residue in the functionalization.

Automated summary

This research successfully synthesized a functional alginate-based material through oxidation and reductive amination processes, confirming the successful attachment of cysteine molecules to the alginate backbone. The preferential impact of guluronic acid residue over mannuronic acid residue in the functionalization process of alginate was observed.