Enzymatically-mineralized double-network hydrogels with ultrahigh mechanical strength, toughness, and stiffness.

Background

Synthetic hydrogels are commonly mechanically weak which limits the scope of their applications.

Methods

In this study, we synthesized an organic-inorganic hybrid hydrogel with ultrahigh strength, stiffness, and toughness via enzyme-induced mineralization of calcium phosphate in a double network of bacterial cellulose nanofibers and alginate-Ca2+.

Results

Cellulose nanofibers formed the first rigid network via hydrogen binding and templated the deposition of calcium phosphate, while alginate-Ca2+ formed the second energy-dissipating network via ionic interaction. The two networks created a brick-mortar-like structure, in which the "tortuous fracture path" mechanism by breaking the interlaced calcium phosphate-coated bacterial cellulose nanofibers and the hysteresis by unzipping the ionic alginate-Ca2+ network made a great contribution to the mechanical properties of the hydrogels.

Conclusion

The optimized hydrogel exhibited ultrahigh fracture stress of 48 MPa, Young's modulus of 1329 MPa, and fracture energy of 3013 J/m2, which are barely possessed by the reported synthetic hydrogels. Finally, the hydrogel represented potential use in subchondral bone defect repair in an ex vivo model.