Intrinsically Bioactive Tannic Acid-Grafted Succinoglycan for Self-Healing and Stimuli-Responsive Drug Delivery Hydrogels

Tannic acid grafting provides a practical strategy for introducing bioactive phenolic functionality into microbial polysaccharides for multifunctional hydrogel design. Herein, tannic acid-modified succinoglycan (SG-TA) was prepared through an ascorbic acid/ H2O2-mediated free-radical process. Spectroscopic, thermal, and purification-control analyses were consistent with covalent incorporation of tannic acid-derived moieties into SG, while characteristic structural features of the SG framework remained evident after modification. SG-TA exhibited tannic acid-equivalent phenolic contents of up to 321.9 mg TAE/g and markedly enhanced antioxidant and antibacterial activities compared with native SG. SG-TA was subsequently incorporated into a poly(vinyl alcohol) (PVA)/borax network to form dynamic SG-TA/PVA/borax (STPB) hydrogels based on reversible interactions. The hydrogels exhibited composition-dependent viscoelasticity, rapid rheological recovery, macroscopic self-rejoining, enhanced deformability, antioxidant and antibacterial functionality, and preliminary cytocompatibility. Time-dependent phenolic release showed that SG-TA-derived phenolic species were partially released from the network, indicating contributions from both matrix-associated and releasable functionality. The reversible network also enabled pH- and glucose-responsive release of 5-fluorouracil as a model small-molecule drug. These findings demonstrate the potential of SG-TA as an intrinsically bioactive microbial polysaccharide for multifunctional, self-healing, and stimuli-responsive drug-delivery hydrogels.