Dual functional quaternary chitosans with thermoresponsive behavior: structure-activity relationships in antibacterial activity and biocompatibility

Cationically modified chitosan derivatives exhibit a range of appealing characteristics, with a particular emphasis on their antimicrobial potential across a broad spectrum of biomedical applications. This study aimed to delve deeper into quaternary chitosan (QC) derivatives. Through the synthesis of both homogeneously and heterogeneously dual-quaternized chitosan (DQC), utilizing AETMAC ([2-(acryloyloxy)ethyl]-trimethylammonium chloride) and GTMAC (glycidyl trimethylammonium chloride), a permanent charge was established, spanning a wide pH range. We assessed structural differences, the type of quaternary functional group, molecular weight (Mw), and charge density. Intriguingly, an upper critical solution temperature (UCST) behavior was observed in AETMAC-functionalized QC. To our knowledge, it is a novel discovery in cationically functionalized chitosan. These materials demonstrated excellent antimicrobial efficacy against model test organisms E. coli and P. syringae. Furthermore, we detected concentration-dependent cytotoxicity in NIH-3T3 fibroblasts. Striking a balance between antimicrobial activity and cytotoxicity becomes a crucial factor in application feasibility. AETMAC-functionalized chitosan emerges as the top performer in terms of overall antibacterial effectiveness, possibly owing to factors like molecular weight, charge characteristics, and variations in the quaternary linker. Quaternary chitosan derivatives, with their excellent antibacterial attributes, hold significant promise as antibacterial or sanitizing agents, as well as across a broad spectrum of biomedical and environmental contexts.

Review: chitosan-based biopolymers for anion-exchange membrane fuel cell application

Chitosan (CS)-based anion exchange membranes (AEMs) have gained significant attention in fuel cell applications owing to their numerous benefits, such as environmental friendliness, flexibility for structural alteration, and improved mechanical, thermal and chemical durability. This study aims to enhance the cell performance of CS-based AEMs by addressing key factors including mechanical stability, ionic conductivity, water absorption and expansion rate. While previous reviews have predominantly focused on CS as a proton-conducting membrane, the present mini-review highlights the advancements of CS-based AEMs. Furthermore, the study investigates the stability of cationic head groups grafted to CS through simulations. Understanding the chemical properties of CS, including the behaviour of grafted head groups, provides valuable insights into the membrane's overall stability and performance. Additionally, the study mentions the potential of modern cellulose membranes for alkaline environments as promising biopolymers. While the primary focus is on CS-based AEMs, the inclusion of cellulose membranes underscores the broader exploration of biopolymer materials for fuel cell applications.

Preparation of chitosan derivatives containing aromatic five-membered heterocycles for efficient antimicrobial and antioxidant activities

In this study, nine chitosan derivatives containing aromatic five-membered heterocycles were prepared and the effects of different grafting methods on the biological activities of chitosan derivatives were investigated. The structures of all the compounds were characterized by Fourier Transform Infrared (FT-IR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy, while the antioxidant, antifungal and antibacterial activities of the chitosan derivatives were tested. The experimental data suggested that the chitosan derivatives had outstanding inhibitory ability against Fusarium graminearum, Fusarium oxysporum f.sp.cucumbrum, Staphylococcus aureus and Escherichia coli. At the same time, some of the compounds showed strong scavenging ability against DPPH radical and superoxide radical. Cytotoxicity experiments have demonstrated that some chitosan derivatives are non-toxic to L929 cells. More importantly, compared to chitosan, these chitosan derivatives have good water solubility and can be used as potential polymers for antifungal and antibacterial biomaterials in agriculture.

Quaternized Chitosan Derivatives as Viable Antiviral Agents: Structure-Activity Correlations and Mechanisms of Action

Cationic polysaccharides have demonstrated significant antimicrobial properties and have great potential in medical applications, where the antiviral activity is of great interest. As of today, alcohols and oxidizing agents are commonly used as antiviral disinfectants. However, these compounds are not environmentally safe, have short activity periods, and may cause health issues. Therefore, this study aimed to develop metal-free and environmentally friendly quaternary chitosans (QCs) with excellent long-lasting virucidal activity. To evaluate this, both single and double QCs were obtained using AETMAC ([2-(acryloyloxy)ethyl]-trimethylammonium chloride) and GTMAC (glycidyl trimethylammonium chloride) quaternary precursors. Further, this study investigated the influence of the quaternary functional group, charge density, and molecular weight (M_w) on the antiviral properties of QCs. It is proposed that the higher charge density, along with the length of alkyl linkers, and hydrophobic interactions affected the antiviral activity of QCs. The findings demonstrated that heterogeneously functionalized chitosan exhibited excellent antiviral activity against both the enveloped virus φ6 and the nonenveloped viruses φX174 and MS2. These quaternized chitosan derivatives have promising potential as viable antiviral agents, as hand/surface sanitizers, or in other biomedical applications.

Determination of the degree of quaternization of N,N,N-trimethylchitosan by CP-MAS 13C NMR

Chitosan is used in several fields such as medicine, environment and advanced functional materials. The N-alkylation of chitosan into N,N,N-trimethylchitosan (TMC) allows to improve some properties. The current quantification methods of the degree of quaternization (DQ) like titration and ¹H NMR spectroscopy require the solubilization of TMC. In this study, a solid-state ¹³C NMR quantification method was developed for insoluble TMCs. For this purpose, four TMC derivatives acting as reference were synthesized and their degrees of quaternization, N,N-dimethylation (DD) and acetylation (DA) were determined in solution by ¹H NMR. CP-MAS ¹³C NMR spectra of those derivatives were deconvolved with Lorentz functions. Several ratios of the ¹³C NMR peak areas were correlated with the degrees of substitution obtained in ¹H NMR. The best quantification method of DQ involved the correlation of the carbon signal of methyl groups. The method was also applied for the determination of the DD and DA of TMCs.