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maintaining their biological integrity to the greatest possible extent. Moreover,
enzymatic cross-linking eliminated the need for toxic chemical cross-linking agents,

enhancing the biocompatibility of the final products and making it particularly well-
suited for in vivo applications or the development of advanced biomedical materials. In

addition, the enzymatic reaction exhibited high substrate specificity, enabling

accurately identification and targeting of specific cross-linking sites, thereby achieving

precise regulation of the cross-linking process. This precise regulation not only

preserved the functional activity of the biomaterial, but also significantly reduces the

possible side effects, which provided a strong guarantee for the preparation of high-

performance biomaterials. By integrating 3D printing technology, the 3D structure of

hydrogels could be accurately designed, while enzymatic cross-linking method enabled

rapid and mild stablization of the structure during the printing process, ensuring optimal

mechanical properties and biocompatibility in the final hydrogel constructs.

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Yajie Zhang et al. prepared an injectable hydrogel system that contained type Ⅰ
collagen tyramine (Col-TA) and hyaluronic acid tyramine (HA-TA) using horseradish

peroxidase (HRP) and H2O2. HRP exhibited rapidly catalyze the oxidation of phenolic
hydroxyl groups in Col-TA and HA-TA to generate ROS intermediates within 10s

under physiological conditions, and promoted the formation of covalent diamine cross-

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links between TA molecules. Jessica M. Rosenholm et al. prepared a 3D printed
biocataltic scaffold consisting of mesoporous SiO2 hydrogels suitable for the

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immobilization of enzymes with different properties (Figure 4). Shinji Sakai et al.
used a hydrogel precursor ink containing phenolated CS (CS-Ph) and CS nanofibers

(CS-NF) for 3D print via HRP-mediated hydrogel gelation to prepare wound dressings.

By adjusting the content of CS-Ph and nanofibers, the viscosity of the ink, the gelation

time, and the mechanical performance of the 3D printed hydrogel could be precisely

controlled. While this process enabled the fabrication of hydrogels with enhanced

mechanical robustness, its reliance on H2O2 as an oxidizing agent introduced oxidative

by-products that may compromise biocompatibility and pose cytotoxicity risks. Huang

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et al. utilized transglutaminase (TGase), an enzyme with broad substrate specificity

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