Super-ductile, injectable, fast self-healing collagen-based hydrogels with multi-responsive and accelerated wound-repair properties

Collagen-based hydrogels have been regarded as one of the most popular biomaterials for applications in biomedical engineering as scaffolds, cell or drug carriers and medical implants. Despite numerous studies on collagen-based hydrogels, their applications are still extremely limited due to lack of multi-functionalities. Herein, we present a facile method to prepare a multifunctional, extremely soft collagen-based hydrogel via the introduction of collagen (COL), guar gum (GG), poly(N-isopropylacrylamide) (PNIPAM), graphene oxide (GO) and borax through the formation of both reversible and permanent networks. The resultant hydrogels (COL–GG–PNIPAMs) exhibited desirable properties, including processability, injectability and remoldability. Remarkably, the COL–GG–PNIPAMs stretched manually up to 50 times their initial length before rupturing (from 2 to 100 cm), indicating their super-ductile deformation; when cut, the hydrogels self-healed within a short time period (less than 3 min) without any external stimuli. In addition, the COL–GG–PNIPAMs showed excellent thermal sensitivity and NIR-responsive properties. The potential application of ionic conductive COL–GG–PNIPAMs for strain sensing was also tested by monitoring real-time large-scale movements of the human body or facial micro-expressions. Moreover, the COL–GG–PNIPAMs exhibited a healing ratio of 81.0% for mouse skin wounds, which was higher than that of the blank group (63.6%), demonstrating an enhanced skin wound repair effect. These prominent features of COL-GG-PNIPAMs will broaden versatile collagen-based hydrogels for a variety of applications.