Peroxidase‐Mimicking Catalytic Activity of Hemin–Alginate Conjugates for In Situ Hydrogelation of Phenolic Polymers

ABSTRACT Horseradish peroxidase (HRP)‐mediated oxidative crosslinking of phenolic polymers is widely employed for in situ hydrogel formation but is limited by high cost and poor oxidative stability. In this study, a hemin‐based polymeric conjugate, alginate–histamine–hemin (Alg–His–He), was developed as a peroxide‐tolerant HRP mimic for phenol crosslinking. Histamine was covalently grafted onto alginate via amide bond formation (70.6% substitution), followed by coordination of hemin through Fe–N(imidazole) interactions to form a polysaccharide–ligand–metal conjugate with tunable hemin content. Structural characterization by FT‐IR, Raman, UV–Vis, and XRD confirmed successful conjugate formation. Alg–His–He exhibited significant peroxidase‐like activity toward guaiacol and pyrogallol, with catalytic performance dependent on the Alg–His/He ratio. Although its activity under mild conditions was lower than that of native HRP, Alg–His–He showed substantially higher tolerance to H 2 O 2 , maintaining catalytic function at peroxide concentrations that rapidly inactivated HRP. The conjugate efficiently catalyzed the oxidative crosslinking of gelatin–tyramine, enabling rapid and controllable hydrogelation. The resulting hydrogels displayed interconnected porous structures, good stability under physiological conditions, controllable enzymatic degradation, and excellent cytocompatibility. These findings highlight Alg–His–He as a biocompatible and peroxide‐resistant HRP mimic for injectable hydrogels and other biomaterial applications.