Sustainable Polysaccharide Hydrogels Based on Dynamic Schiff Base Linkages as Versatile Building Blocks for Fabricating Advanced Functional Materials

Polysaccharides are an idiosyncratic source of organic natural materials apropos structural diversity, functionalities, and abundance. In their indigenous state, few of their functionalities inhabit their material form as hydrogels, consequently proffering molecular tactics to be exploited. Recently, polysaccharide-based hydrogels utilizing the Schiff base bonds or dynamic imine chemistry as crosslinks have been widely explored owing to their high sensitivity, good flexibility, enhanced recyclability, stimuli-responsiveness, and tissue adhesion. The polysaccharide-derived Schiff base hydrogels bestow elementary fabrication, self-healing properties, and injectibility under physiological conditions, resulting in mechanical forces that result in the augmentation of gel precursors. These hierarchical constructs can be tuned for mechanically, morphologically, and biochemically different microenvironments, thus finding numerous applications in a variety of fields. Herein, we comprehensively analyze the constitutive nature, state-of-the-art design principles, gelling mechanism, and structural or mechanical properties of dynamic polysaccharide-Schiff-based hydrogels. In a dynamic covalent bond polysaccharide framework, various interactions such as hydrogen bonding, hydrophobic interactions, and metal–ligand interactions produce toughness, high strength, and environmental responsiveness. We propound that polysaccharide hydrogels based on dynamic Schiff base linkages proffer advantages owing to the dynamic interfacial imine formation that can translate changes in bonding to macroscopic outputs. Emerging strategies that may enhance and ameliorate the properties, current scope and functionalities along with current challenges to the field have been assessed to impart guidelines for the rational design of these dynamic hydrogel systems.