Ternary hydrogel with tunable mechanical and self-healing properties based on the synergistic effects of multi-dynamic bonds

Considering the good biocompatibility, the composite hydrogel of gelatin (Gel) and oxidized sodium alginate (OSA) is often used in biomedical fields. However, the typical utility of borax and weak mechanical property are not preferred either in cell environment or as a supporting scaffold. Herein, poly (vinyl alcohol) (PVA) was mixed with Gel and OSA to construct a ternary hydrogel Gel-OSA-PVA so as to improve the mechanical properties and reduce toxicity. The hydrogel possessed tunable mechanical properties by adjusting the concentrations of PVA and the oxidized degrees of OSA, related closely to the dynamic imine bonds and multiple hydrogen bonds among these macromolecules. In terms of the effects of OSA, its aldehyde group content played a more important role in enhancing the compressive modulus of hydrogel compared with its change of molecular weight/chain length. These multi-dynamic bonds also imparted the Gel-OSA-PVA hydrogel with good self-healing performance. Interestingly, the hydrogels presented great conductivity due to the existence of free ions, varying with the deformation of hydrogels, and had great potential in promoting osteogenesis. Together with no cytotoxicity and antibacterial property, the hydrogel was potential in the biomedical fields.