On chitosan-agarose-gelatin hydrogels functionalized with tannic acid and metallic ions for regenerative medicine

Tissue defects resulting from trauma and related diseases continue to pose a significant clinical challenge due to their limited capacity for self-healing. Conventional grafts and substitutes remain limited, highlighting the strong demand for affordable, bioactive materials capable of responding to the complex physicochemical conditions of tissue regeneration. Biopolymer-based hydrogels are promising candidates, although their clinical translation requires optimized design. In this study, multifunctional chitosan-agarose-gelatin hydrogels were developed through dual cross-linking and subsequently functionalized with tannic acid (TA) and/or TA-metal complexes (Sr²⁺, Cu²⁺, or both). The physicochemical, mechanical, and thermal properties, as well as the biodegradation, hemocompatibility, and cytocompatibility, were investigated. Results show the formation of a dual-architecture structure at both macro- and micro-porosity levels. TA-only functionalization led to insufficient hydrogel stability, whereas incorporation of metal ions significantly improved it, with degradation rates ranging from ~13-25 % at 30 days. Depending on formulation, compressive strengths ranged from 10 to 30 kPa, and Young's Modulus from 50 to 100 kPa, reflecting the different coordination modes of TA-metal complexes. The biological evaluation confirmed satisfactory outcomes for all functionalized hydrogels. TA + Cu²⁺/Sr²⁺ functionalization with a short incubation time emerged as the most promising strategy, achieving an interesting compromise between physicochemical properties, degradation, and mechanical performance. Overall, the developed hydrogels represent a versatile and tunable platform with high potential for application in regenerative medicine.