Biopolymeric Films of Amphiphilic Derivatives of Chitosan: A Physicochemical Characterization and Antifungal Study

Abstract

The chemical modification of chitosan has been an active subject of research in order to improve the physicochemical and antifungal properties of chitosan-based films. The aim of this study was to evaluate the physiochemical and antifungal properties of films prepared with chitosan and its derivatives containing diethylaminoethyl (DEAE) and dodecyl groups (Dod). Chitosans and selected derivatives were synthesized and characterized, and their films blended with glycerol and sorbitol (5%, 10%, and 20%). They were studied by means of the evaluation of their mechanical, thermal, barrier, and antifungal properties. The collected data showed that molecular weight (Mw), degree of acetylation, and grafting with DEAE and Dod groups greatly affected the mechanical, thickness, color, and barrier properties, all of which could be tailored by the plasticizer percentage. The antifungal study against Aspergillus flavus, Alternaria alternata, Alternaria solani, and Penicillium expansum showed that the films containing DEAE and Dod groups exhibited higher antifungal activity than the non-modified chitosans. The mechanical properties of highly soluble films were improved by the plasticizers at percentages of 5% and 10%, indicating these derivatives as potential candidates for the coating of seeds, nuts and fruits of various crops.

DEAE/Catechol–Chitosan Conjugates as Bioactive Polymers: Synthesis, Characterization, and Potential Applications

“…The absorbance measurements at 600 nm for Cs–DEAE showed values close to 0.0 in pH conditions under 8.3, without the appearance of precipitates until the solution was adjusted to pH = 11.3 (absorbance 600 nm = 0.20). The highest water solubility of Cs–DEAE is attributable to the contribution of the p K a ∼ 10.0 of the tertiary amino group of DEAE . On the other hand, it is observed that the Cs–DC solutions only slightly increase their absorbance at 600 nm to ∼0.06, even at pH = 11.3.…”

“…Cs–Ca and Cs–DC conjugates were synthesized using EDC coupling chemistry by forming amide bonds between a primary amine group in Cs or Cs–DEAE and a carboxylic acid group in HCA . Since the EDC chemistry is more propitious for the non-protonated amino groups, the conjugation took place at pH 5.5 to prevent the precipitation of the Cs (p K a = 6.2–6.4) and limit amino protonation . It is important to note that the incorporation of specific chemical groups can increase the polymer’s solubility at a higher pH range compared to the unmodified Cs.…”

“…48 Since the EDC chemistry is more propitious for the non-protonated amino groups, the conjugation took place at pH 5.5 to prevent the precipitation of the Cs (pK a = 6.2−6.4) and limit amino protonation. 49 It is important to note that the incorporation of specific chemical groups can increase the polymer's solubility at a higher pH range compared to the unmodified Cs. Remarkably, the benefit of DEAE groups depends on its tertiary amine, whose pK a (∼10.0) allows complete solubilization of the polysaccharide in neutral aqueous media.…”

“…The highest water solubility of Cs−DEAE is attributable to the contribution of the pK a ∼ 10.0 of the tertiary amino group of DEAE. 49 On the other hand, it is observed that the Cs−DC solutions only slightly increase their absorbance at 600 nm to ∼0.06, even at First, the incorporated groups have pK a values higher than those of Cs, which positively increases the effective pK a of the conjugate polymer, contributing to its enhanced solubility in an aqueous medium. Second, the chemical modifications break the intra-and inter-hydrogen bonds of Cs, which reduces the rigidity of the molecular arrangement, improving the solubility, as has been previously described.…”

Prevention and Treatment of Fungal Skin Infections Using Cationic Polymeric Films

“…Inspired by work on protective polymeric films for the coating of plant seeds [ 11 , 12 , 13 ], we envisaged a novel strategy to tackle fungal skin infections by using film-forming agents. These are typically polymers that can form a continuous thin layer on biotic or abiotic surfaces.…”