C6-Modifications on chitosan to develop chitosan-based glycopolymers and their lectin-affinities with sigmoidal binding profiles

Strategies for the Preparation of Chitosan Derivatives for Antimicrobial, Drug Delivery, and Agricultural Applications: A Review

Chitosan has received much attention for its role in designing and developing novel derivatives as well as its applications across a broad spectrum of biological and physiological activities, owing to its desirable characteristics such as being biodegradable, being a biopolymer, and its overall eco-friendliness. The main objective of this review is to explore the recent chemical modifications of chitosan that have been achieved through various synthetic methods. These chitosan derivatives are categorized based on their synthetic pathways or the presence of common functional groups, which include alkylated, acylated, Schiff base, quaternary ammonia, guanidine, and heterocyclic rings. We have also described the recent applications of chitosan and its derivatives, along with nanomaterials, their mechanisms, and prospective challenges, especially in areas such as antimicrobial activities, targeted drug delivery for various diseases, and plant agricultural domains. The accumulation of these recent findings has the potential to offer insight not only into innovative approaches for the preparation of chitosan derivatives but also into their diverse applications. These insights may spark novel ideas for drug development or drug carriers, particularly in the antimicrobial, medicinal, and plant agricultural fields.

Preparation and evaluation of a novel chlorine dioxide preservative based on citric acid grafted carboxymethyl chitosan

Instrument-free chlorine dioxide (ClO₂) preservative for fruit and vegetable has gained great attention due to its convenience and safety. In this study, a series of carboxymethyl chitosan (CMC) with citric acid (CA) substituents were synthesized, characterized, and further used to prepare a novel ClO₂ slow-releasing preservative for longan. UV-Vis and FT-IR spectra revealed that CMC-CA#1-3 were successfully prepared. Further potentiometric titration showed that the mass ratios of CA grafted in CMC-CA#1-3 were 0.18:1, 0.42:1, and 0.42:1, respectively. The composition and concentration of ClO₂ slow-releasing preservative were optimized, and the best formulation was as follows: NaClO₂:CMC-CA#2:Na₂SO₄:starch = 3:2:1:1. The maximum ClO₂ release time of this preservative reached >240 h at 5-25 °C, and the maximum release rate always occurred at 12-36 h. Longan treated with 0.15-1.2 g ClO₂ preservative had significantly (p < 0.05) higher L* and a* values but lower respiration rate and total microbial colony counts than the CK group (0 g ClO₂ preservative). After 17 days of storage, longan treated with 0.3 g ClO₂ preservative had the highest L* value of 47.47 and lowest respiration rate of 34.42 mg·kg^-1·h^-1, showing the best pericarp color and pulp quality. This study provided a safe, effective, and simple solution for longan preservation.

A Review of the Preparation, Characterization, and Applications of Chitosan Nanoparticles in Nanomedicine

Chitosan is a fibrous compound derived from chitin, which is the second most abundant natural polysaccharide and is produced by crustaceans, including crabs, shrimps, and lobsters. Chitosan has all of the important medicinal properties, including biocompatibility, biodegradability, and hydrophilicity, and it is relatively nontoxic and cationic in nature. Chitosan nanoparticles are particularly useful due to their small size, providing a large surface-to-volume ratio, and physicochemical properties that may differ from that of their bulk counterparts; thus, chitosan nanoparticles (CNPs) are widely used in biomedical applications and, particularly, as contrast agents for medical imaging and as vehicles for drug and gene delivery into tumors. Because CNPs are formed from a natural biopolymer, they can readily be functionalized with drugs, RNA, DNA, and other molecules to target a desired result in vivo. Furthermore, chitosan is approved by the United States Food and Drug Administration as being Generally Recognized as Safe (GRAS). This paper reviews the structural characteristics and various synthesis methods used to produce chitosan nanoparticles and nanostructures, such as ionic gelation, microemulsion, polyelectrolyte complexing, emulsification solvent diffusion, and the reverse micellar method. Various characterization techniques and analyses are also discussed. In addition, we review drug delivery applications of chitosan nanoparticles, including for ocular, oral, pulmonary, nasal, and vaginal methodologies, and applications in cancer therapy and tissue engineering.

Fabrication and functionalization of biocompatible carboxymethyl chitosan/gelatin membranes via anodic electrophoretic deposition

A biocompatible CMC/G membrane for titanium substrates has been fabricated in an eco-friendly manner and could be a promising carrier for negatively charged agents.

Effects of citronellol grafted chitosan oligosaccharide derivatives on regulating anti-inflammatory activity

In order to improve the anti-inflammatory activity of chitosan oligosaccharide (COS), chitosan oligosaccharide graft citronellol derivatives (COS-g-Cit1-3) were successfully synthesized via grafting citronellol (Cit) onto COS backbone. The degrees of substitution (DS) of COS-g-Cit1-3 were 0.165, 0.199 and 0.182, respectively. The structure of COS-g-Cit1-3 was confirmed by UV-vis, FT-IR, ¹H NMR and elemental analysis. The in vivo anti-inflammatory activity evaluation results displayed that COS-g-Cit1-3 drastically reduced the paw swelling, and the oedema inhibitions were 22.58 %, 29.03 % and 25.81 %, respectively. The results indicated that the anti-inflammatory effects of COS-g-Cit1-3 were significantly higher than COS and COS-g-Cit2 exhibited the highest anti-inflammatory ability. The results also presented that COS-g-Cit1-3 reduced the expression levels of TNF-α by promoting the secretion of IL-4 and IL-10. Moreover, western blot analysis data proved that COS-g-Cit1-3 inactivated the NF-κB signaling pathway via inhibiting the phosphorylation of p65, IKBα and IKKβ.

Cationic chitosan derivatives as potential antifungals: A review of structural optimization and applications

The increasing resistance of pathogen fungi poses a global public concern. There are several limitations in current antifungals, including few available fungicides, severe toxicity of some fungicides, and drug resistance. Therefore, there is an urgent need to develop new antifungals with novel targets. Chitosan has been recognized as a potential antifungal substance due to its good biocompatibility, biodegradability, non-toxicity, and availability in abundance, but its applications are hampered by the low charge density results in low solubility at physiological pH. It is believed that enhancing the positive charge density of chitosan may be the most effective approach to improve both its solubility and antifungal activity. Hence, this review mainly focuses on the structural optimization strategy of cationic chitosan and the potential antifungal applications. This review also assesses and comments on the challenges, shortcomings, and prospect of cationic chitosan derivatives as antifungal therapy.

Glycosylated cellulose derivatives with regioselective distributions of pendant glucose moieties

Inspired by the presence of diverse carbohydrates on the surface of biological systems, we present herein a method for the synthesis of sugar-bearing polymers derived from renewable cellulose. In this paper, novel glycosylated cellulose derivatives were successfully synthesized containing a series of subsequent reactions: (1) synthesis of cellulose derivatives with pendant hydroxyl groups via nucleophilic substitution; (2) further sequential reactions containing a novel TEMPO/[bis(acetoxy)iodo]benzene (BAIB)-mediated oxidation of pendant hydroxyl groups, Schiff base formation and reduction in one-pot reaction; and (3) thiol-ene click reaction as an efficient tool to generate cellulose derivatives with pendant glucosyl groups. Furthermore, the glucosyl groups were only linked with the C6 position of anhydroglucose units (AGUs) of cellulose. Moreover, the glycosylated cellulose derivatives could be reversibly cross-linked by 1,4-phenylenediboronic acid at pH 10 and dissociated into single polymer chains by using glucose, which allow such glycolated cellulose derivatives to be interesting responsive materials.

Synthesis and antioxidant action of chitosan derivatives with amino-containing groups via azide-alkyne click reaction and N-methylation

Amino functionality has been paid growing attention in chemical modification of polysaccharides due to their potential biomedical applications. Here, the preparation of novel antioxidant materials based on chitosan derivatives bearing amino-containing groups equipped with 1,2,3-triazole and 1,2,3-triazolium by Cuprous-catalyzed azide-alkyne cycloaddition and N-methylation was described for the first time. The structural characteristics of the synthesized derivatives were examined by FTIR, ¹H NMR, and elemental analysis. The antioxidant activities of the chitosan derivatives were assessed in vitro. The results indicated that chitosan derivatives bearing 1,2,3-triazoles displayed superior antioxidant activity over pristine chitosan, especially against superoxide anion radical. Moreover, antioxidant efficiency of chitosan derivatives further enhanced after N-methylation of 1,2,3-triazole moieties with iodomethane, which is comparative to that of ascorbic acid. Notably, of all chitosan derivatives bearing 1,2,3-triazole or 1,2,3-triazolium moieties, acylhydrazine-functionalized and amino-functionalized chitosan showed the stronger antioxidant capacity than hydroxyl-modified chitosan at the test concentration. Besides, the cytotoxicities of them were also evaluated in vitro on HaCaT cells. These results suggested that amino and acylhydrazine-functionalized chitosan derivatives with 1,2,3-triazolium could be used as novel antioxidant biomaterials.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.