Tissue‐engineered hydrogels have received extensive attention as their mechanical properties, chemical compositions, and biological signals can be dynamically modified for mimicking extracellular matrices (ECM). Herein, the synthesis of novel double network (DN) hydrogels with tunable mechanical properties using combinatorial screening methods is reported. Furthermore, nanoengineered (NE) hydrogels are constructed by addition of ultrathin 2D black phosphorus (BP) nanosheets to the DN hydrogels with multiple functions for mimicking the ECM microenvironment to induce tissue regeneration. Notably, it is found that the BP nanosheets exhibit intrinsic properties for induced CaP crystal particle formation and therefore improve the mineralization ability of NE hydrogels. Finally, in vitro and in vivo data demonstrate that the BP nanosheets, mineralized CaP crystal nanoparticles, and excellent mechanical properties provide a favorable ECM microenvironment to mediate greater osteogenic cell differentiation and bone regeneration. Consequently, the combination of bioactive chemical materials and excellent mechanical stimuli of NE hydrogels inspire novel engineering strategies for bone‐tissue regeneration.

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Underwater adhesives (UAs) have promising applications in diverse areas. However, traditional UAs have several drawbacks such as weak and irreversible adhesion behaviors as well as poor performance in biological environments. To address these challenges, we engineered a novel synthetic adhesive based on dynamic hydrophilic and hydrophobic moieties, which shows very strong underwater adhesion strength (30–110 kPa) and debonding energy (20–100 J/m2) to diverse substrates. Interestingly, the UAs could also be switched reversibly and repeatedly by the dynamic exchange of hydrophilic and hydrophobic moieties under alternating temperatures. We also demonstrate the versatile functions and practical value of the UAs for clinical applications as tissue sealants and hemostatic dressing in emergency rescue operations. This general and efficient strategy may be generalized to develop additional next generation UAs for many emerging technological and medical applications.