# Injectable and Self-Healing Boronic-Acid-Modified Succinoglycan Hydrogels: Dual-Stimuli-Responsive Platforms for Controlled Tannic Acid Release

## TL;DR

This study creates a self-healing hydrogel that can release tannic acid in response to changes in pH and glucose, showing promise for drug delivery and biomedical uses.

## Contribution

The novel contribution is the development of a dual-stimuli-responsive hydrogel using boronic-acid-modified succinoglycan for controlled tannic acid release.

## Key findings

- The SAT hydrogel showed 89.8% DPPH and 96.4% ABTS radical scavenging activity, indicating strong antioxidant properties.
- TA release increased with decreasing pH and increasing glucose concentration, showing dual-stimuli responsiveness.
- The hydrogel exhibited a synergistic double-shock effect when exposed to combined pH and glucose changes.

## Abstract

In this study, succinoglycan (SG), an anionic exopolysaccharide derived from Sinorhizobium meliloti Rm1021, was chemically modified to introduce boronic acid groups, creating a boronic-acid-functionalized polysaccharide (SG-APBA). The degree of substitution varied from 4.24% to 24.3%, depending on APBA concentration, with SG-APBA 2 identified as the optimal formulation. The properties of SG-APBA were characterized using 1H NMR, FTIR, TGA, and XRD, along with rheological analysis to assess changes in the polymer’s behavior. The hydrogel, referred to as SAT, was formed through dynamic boronate-ester bonds and hydrogen bonds between SG-APBA and tannic acid (TA). This hydrogel demonstrated excellent injectability, self-healing capacity, and biocompatibility. Incorporation of boronic acid groups allowed the hydrogel to respond to variations in glucose levels and pH, enabling controlled TA release and enhancing its stimulus-responsive antioxidant and antibacterial activities. Antioxidant performance was confirmed through DPPH and ABTS radical scavenging assays, achieving respective activities of 89.8% and 96.4%. Antibacterial effectiveness was validated via inhibition zone tests. Additionally, the SAT hydrogel exhibited dual responsiveness to pH and glucose, with TA release percentages of 55.4% at pH 9.0, 62.7% at pH 7.4, and 69.9% at pH 5.0; and 62.7% at 0 mM glucose, 68.9% at 5 mM, and 72.5% at 25 mM glucose after 120 h. Moreover, combined alterations in pH and glucose triggered a synergistic double-shock effect, markedly accelerating TA release relative to individual stimuli. Overall, these results indicate that the SG-APBA/TA hydrogel has strong potential as a stimuli-responsive platform for drug delivery and biomedical applications.