One-Step Formed Janus Hydrogel with Time-Space Regulating Properties for Suture-Free and High-Quality Tendon Healing

Janus hydrogels have promising applications in tendon healing and anti-peritendinous adhesions. However, their complicated preparation methods, weak mechanical properties, and unstable adhesion interfaces have severely limited their application in suture-free and high-quality tendon healing. In this work, by controlling the interfacial distribution of free -COOH groups and cationic-π structures on both sides of the hydrogels, a series of PZBA-EGCG-ALC Janus hydrogels with varying degrees of asymmetric properties are successfully prepared using a simple and efficient one-step synthesis method. The tensile strength and elongation at the break of the Janus hydrogel are as high as 0.51 ± 0.04 MPa and 922.89 ± 28.59%. In addition, the Janus hydrogel can achieve a high difference in adhesion strength (nearly 20-fold) while maintaining a strong adhesion strength on their bottom sides (up to 524.8 ± 33.1 J m^-2). In the spatial dimension, its excellent mechanical compliance and one-sided adhesion behavior can provide effective mechanical support and physical barriers for the injured Achilles tendons. More importantly, the Janus hydrogel can also minimize early inflammation generation in the time dimension via its ROS-responsive PZBA-EGCG prodrug macromolecules. This study provided a more effective and convenient suture-free strategy for constructing Janus hydrogels to promote high-quality tendon healing.