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

Abstract

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, 1H-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 C1-H1 of β-D-mannuronic acid residue as well as C1-H1 of α-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 13C-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 μmol 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.

The Content, Antioxidant Activity, and Structural Characteristics of Sodium Alginate Extracting from Sargassum polycystum Grew in Vietnam: Effect of Various Extraction Conditions

“…7). The significant difference in the chemical shifts of carbon atoms in the current study and the previous reports on the NMR of alginate did not appear because the differences were lower than 0.05 ppm [25], describled by Hans et al (1977) [26] and Peter (1988) [27]. The absorbance of the British standard solution (1mg/ml) is D=0.473.…”

Characterization of Sodium Alginate Hydrogels Reinforced with Nanoparticles of Hydroxyapatite for Biomedical Applications

“…This signal disappeared in sample SAHA-60 due to a minor amount of alginate; peaks at δ 3.81, 3.80, and 3.7 ppm ascribed to the hydrogen atoms linked to the C-2, C-3, and C-4 carbons of the M residue. The alginate calcium/hydroxyapatite showed some additional characteristic peaks appearing at a range of δ 0.83-2.3 ppm, indicating that the alginate polymer microstructure was strongly dependent on the crosslinking calcium ion and the atoms of the hydroxyapatite structure [23][24][25].…”

Physicochemical Characterization of Nanobiocomposites

“…A small increment of the absorption between 2900 and 3000 cm À1 , and the increased CdH stretch of the methyl group of IEM indicates functionalization [24]. Similar studies that reported the use of IR in confirming functionalization include alginate [25], methoxylated pectin and amidated LMP [13], chitosan functionalization with the PNIPAAm [26], cellulosepropargylated chitosan [27], Melamine-Functionalized Chitosan: [28], etc.…”

“…On the other hand, HSQC ( 1 Hd 13 C) can also be used to study the interaction between hydrogen and carbon atoms within a biopolymer. Huamani-Palomino et al utilized the HSQC spectrum to confirm the purification process of alginate (Figure 9B) by observing the coupling bands of the alginate monomers (glucoronic acid and mannuronic acid) [25]. Representative 1H-NMR spectra of hydrogels (a) with higher water content 1q, 2 t and (b) lower water content 3d, 4d, recorded over time (from up to down: 1, 7, 15, and 22 days) [40].…”