Physical dynamic double-network hydrogels as dressings to facilitate tissue repair.

Double-network hydrogels can be tuned to have high mechanical strength, stability, elasticity and bioresponsive properties, which can be combined to create self-healing, adhesive and antibacterial wound dressings. Compared with single-network hydrogel, double-network hydrogel shows stronger mechanical properties and better stability. In comparison with chemical bonds, the cross-linking in double networks makes them more flexible than single-network hydrogels and capable of self-healing following mechanical damage. Here, we present the stepwise synthesis of physical double-network hydrogels where hydrogen bonds and coordination reactions provide self-healing, pH-responsive, tissue-adhesive, antioxidant, photothermal and antibacterial properties, and can be removed on demand. We then explain how to carry out physical, chemical and biological characterizations of the hydrogels for use as wound dressings, yet the double-network hydrogels could also be used in different applications such as tissue engineering scaffolds, cell/drug delivery systems, hemostatic agents or in flexible wearable devices for monitoring physiological and pathological parameters. We also outline how to use the double-network hydrogels in vivo as wound dressings or hemostatic agents. The synthesis of the ureido-pyrimidinone-modified gelatin, catechol-modified polymers and the hydrogels requires 84 h, 48 h and 1 h, respectively, whereas the in vivo assays require 3.5 weeks. The procedure is suitable for users with expertise in biomedical polymer materials.