Fabrication of highly stretchable hydrogel based on crosslinking between alendronates functionalized poly-γ-glutamate and calcium cations

We report a highly stretchable hydrogel based on the crosslinking structure between calcium cations and alendronates (ALN) conjugated with poly-γ-glutamate (γ-PGA), a typical biodegradable polymer. γ-PGA with ALN (γ-PGA-ALN) forms the hydrogel in the aqueous solution containing CaCl2. The hydrogel shows 2000% of stretchability and reversible stretching without failure at a strain of 250%. The fracture strain and stress are tunable by varying the concentration of either γ-PGA-ALN or CaCl2, indicating the importance of fine-tuning of the density of the cross-linkage to control the mechanical properties of the hydrogel. We believe the biodegradable polymer based highly stretchable hydrogel has potential for use in various fields such as tissue engineering.