Bioinspired Self-Healing of Kinetically Inert Hydrogels Mediated by Chemical Nutrient Supply.

Dynamic stability and self-healing ability are two inherently compatible properties for living organisms. By contrast, kinetic stability and intrinsic healability are two desired but mostly incompatible properties for synthetic materials. This is because the healing of these materials heavily relies on the kinetic lability of the chemical bonds or physical interactions in materials. Inspired by the hierarchically and temporally controlled wound healing in biological systems, here, we report the intrinsic healing of kinetically stable hydrogels, regulated by the consumption of chemical nutrients. The acylhydrazone-based polymer hydrogels with preinstalled urease and urea were formed at a low initial pH, followed by in situ enzymatic generation of a base to deactivate the dynamic bonds, allowing efficient fabrication of kinetically stable hydrogels. The healing of damaged hydrogels was effective when fed with proper chemical nutrients (i.e., acidic urea solutions), in which case a transient acidic pH state was temporally programmed by combining a fast acidic activator (for structural healing) with the slow, biocatalytic generation of a base (for property recovery). The ability to regulate both hydrogel fabrication and healing via a single enzymatic reaction could provide a new approach to create kinetically stable materials capable of healing damages on demand.