Quaternized polysaccharides: A focused review on molecular engineering, antimicrobial mechanisms, and advanced applications.

The escalating threat of antibiotic resistance has intensified the search for sustainable antimicrobial alternatives. Quaternized polysaccharides, a class of cationic biopolymers derived from renewable biomass, offer significant potential due to their potent broad-spectrum activity, unique non-specific mechanisms, and excellent biocompatibility. This review systematically elucidates the molecular engineering of quaternized polysaccharides, covering diverse chemical modification strategies such as direct quaternization, etherification, graft copolymerization, and green synthesis pathways. A comprehensive analysis of multidimensional synergistic bactericidal mechanisms-encompassing electrostatic adsorption, membrane disruption, and intracellular targeting-is provided, alongside a detailed summary of structure-activity relationships governed by parameters like degree of substitution, alkyl chain length, and molecular weight. Furthermore, application-driven material designs in wound dressings, food packaging, water treatment, and medical coatings are highlighted. The discussion concludes by addressing critical challenges in precision synthesis and industrial translation while envisioning future frontiers, including smart-responsive systems and artificial intelligence-assisted design. This focused review provides a strategic roadmap for the rational design and development of high-performance polysaccharide-based antimicrobial materials.