Interactions between Alginate and Chitosan Biopolymers Characterized Using FTIR and XPS

Abstract

This study investigates alginate-chitosan polyelectrolyte complexes (PECs) in the form of a film, a precipitate, as well as a layer-by-layer (LbL) assembly. The focus of this study is to fully characterize, using the complementary techniques of Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) in combination with solution stability evaluation, the interactions between alginate and chitosan in the PECs. In the FTIR spectra, no significant change in the band position of the two carbonyl vibrations from alginate occurs upon interaction with different ionic species. However, protonation of the carboxylate group causes a new band to appear at 1710 cm(-1), as anticipated. Partial protonation of the amine group of chitosan causes the appearance of one new band ( approximately 1530 cm(-1)) due to one of the -NH3+ vibrational modes (the other mode overlaps the amide I band). Importantly, the position of the two main bands in the spectral region of interest in partly protonated chitosan films is not dependent on the extent of protonation. XPS N 1s narrow scans can, however, be used to assess the degree of amine protonation. In our alginate-chitosan film, precipitate, and LbL assembly, the bands observed in the FTIR correspond to the species -COO- and -NH3+, but their position is not different from each of the single components. Thus, the conclusion of the study is that FTIR cannot be used directly to identify the presence of PECs. However, in combination with XPS (survey and narrow N 1s scans) and solution stability evaluation, a more complete description of the structure can be obtained. This conclusion challenges the assignment of FTIR spectra in the literature.

Preparation and characterization of microcapsules of Pterodon pubescens Benth. by using natural polymers

“…Similar results have been observed by other authors (Lawrie et al, 2007;Pasparakis, Bouropoulos, 2006). According to Czubenko and Druzynska (2009), the vibrations at 2931 cm -1 are attributable to an aliphatic C-H stretch.…”

Interaction of O-acylated chitosans with biomembrane models: Probing the effects from hydrophobic interactions and hydrogen bonding

“…4, whose main bands at 1332/1334 cm −1 assigned to CN stretching (amide III) and at 1540-1560 cm −1 assigned to NH bending (amide II) are related to 2-acetamido-2-deoxy-d-glucopyranose residues (GlcNAc). The bands at 1504 cm −1 and 1531/1535 cm −1 are due, respectively, to symmetric and antisymmetric deformation from protonated amine groups of chitosan [23,29,38] bands at 1720-1750 cm −1 are assigned to the ester carbonyl band (C O) [39]. The broad, intense signal at 1620-1720 cm −1 is ascribed to the bending mode from water, being a result of the difference in reflectivity between covered and uncovered surfaces [40].…”

Controlled release of pentoxifylline from porous chitosan-pectin scaffolds

“…Peak 1630 cm −1 indicates the formation of ionic bonds between chitosan's amino groups and pectin's carboxyl group (Ghaffari et al, 2007). Peak 1554 cm −1 is assigned to amide II overlapping with amine and protonated amine (Lawrie et al, 2007). The intensity of the peak at 1554 cm −1 decreased as the concentration of pectin increased.…”