Gelatin-Based Adhesive Hydrogels with Self-Healing, Injectable and Temperature-Triggered Detachable Properties

Adhesive hydrogels are emerging as attractive functional materials for various fields, such as tissue engineering, wound healing, E-skins, etc. However, the removal of adhesive hydrogels from covered area may be painful and cause a secondary damage. In the current study, gelatin-based hydrogels are prepared by cross-linking with tannic acid and 4-formylphenyl boronic acid, through simultaneous dynamic covalent boronic ester and imine bond formations. The obtained hydrogels not only present self-healing and injectable properties, but also show tunable adhesiveness that regulated by temperature and oxidation degrees of tannic acid. The maximum adhesion strength of the hydrogels with medium oxidation degree at 37 degrees C can be measured up to 30 kPa on porcine skin, while the value decreased to approximate to 10 kPa at lowered temperature of 25 degrees C, facilitating the unpainful removal of the hydrogels from skins. This work provides a new approach for the design of functional hydrogels with tailorable adhesiveness.