Abstract: To mimic the dynamic viscoelasticity of the extracellular matrix, the development of artificial materials with mechanical properties similar to those of biological tissues has become an important research direction in the fields of tissue engineering and regenerative medicine. In this study, hydrogels with tunable viscoelasticity were constructed using dextran and polyethylene glycol(PEG) as polymer backbones, crosslinked through dynamic acylhydrazone bonds formed between aldehyde groups and benzoylhydrazide. To better understand and regulate their mechanical behavior, the effects of key parameters such as pH, component ratios, PEG molecular weight, and solid content on the gel's viscoelasticity were systematically investigated. The results showed that gelation occurred fastest under acidic conditions at pH =5(gelation time approximately 13 min); increasing the content of oxidized dextran enhanced the hydrogel's viscoelasticity, as indicated by faster stress relaxation(τ1/2, the time required for the stress to relax to half of its original value, as low as 246 s) and increased creep deformation; while increasing the PEG content reduced the hydrogel's viscoelasticity; at the same solid content, a higher PEG molecular weight also helped to strengthen the hydrogel's viscoelasticity. Benefiting from the reversible breaking and reconstruction of dynamic acylhydrazone bonds, the hydrogel exhibited excellent energy dissipation capability and showed a stable mechanical response under cyclic loading; at the same time, this dynamic bonding mechanism enabled efficient self-healing at room temperature, with damage interfaces completely disappearing within 6 hours. Additionally, the system displayed good shear-thinning behavior and injectability, allowing for smooth extrusion through fine needles, providing significant convenience for applications in minimally invasive implantation and localized delivery in biomedical scenarios.

Key words: Dynamic covalent bond, Acylhydrazone bond, Viscoelasticity, Self-healing, Injectable property