Natural polysaccharide-based injectable hydrogels with tunable mechanical and electrical properties enabled by phytic acid.

A fully natural polysaccharide-based hydrogel with tunable mechanical and electrical properties was developed by introducing phytic acid (PA) into a dynamic Schiff-base network formed between chitosan (CS) and oxidized sodium alginate (OSA), using a simple and scalable post-treatment strategy. Unlike conventional methods that require complex chemical modifications or synthetic conductive additives, this approach leverages the inherent multifunctionality of PA to simultaneously achieve structural reinforcement and ionic conductivity enhancement through a single, mild, and chemical-free immersion process, representing a significant advancement in hydrogel design. The incorporation of PA significantly enhanced the mechanical strength of the hydrogel (12.6 kPa up to 881.8 kPa), reduced swelling (from 9185.6 ± 127.0 % to 135.2 ± 26.0 %), and improved degradation resistance (mass loss reduced from 93.2 ± 3.1 % to 7.5 ± 0.9 %). Moreover, the presence of dissociated phosphate groups from PA introduced mobile ionic species, leading to increased ionic conductivity and stable strain-responsive electrical signals. The hydrogel also exhibited excellent cytocompatibility, low hemolysis ratios (<5 %), and strong antioxidant activity, particularly at optimized PA concentrations. These enhancements were attributed to PA-mediated multi-point hydrogen bonding and electrostatic interactions, which reinforced the network structure and promoted ionic mobility. This work not only demonstrates an effective strategy for modulating hydrogel properties in a green and scalable manner, but also expands the application potential of natural polysaccharide hydrogels by offering a previously underexplored yet highly efficient route for achieving multifunctionality.