Tea eggs-inspired high-strength natural polymer hydrogels

Natural polymer (NP) hydrogels are an irreplaceable class of biomaterials owing to their identified biosafety; however, the intrinsic poor mechanical strengths severely limit their applications as structural tissue engineering scaffolds. Inspired by the stiffening albumen gel of tea eggs, a traditional Chinese snack, high-strength NP hydrogels are constructed by simply soaking in aqueous solution of tea polyphenols (TP), an active ingredient extracted from tea. The TP-treated representative NP hydrogels exhibit considerably enhanced multifaceted mechanical properties with maximum 19-/30-, 8.4-, 6.1-, 72-fold increases in tensile/compressive strengths, Young's modulus, elongation at break and facture toughness, respectively, compared with pristine hydrogels, primarily due to the hydrogen bonding interactions between TP and NP chains. The TP-treated NP hydrogels can resist different large deformations, which cannot be achieved by their original species at all. In aqueous solution, the TP-treated NP hydrogels can still maintain robust mechanical performances, in spite of somewhat decline in strengths with release of TP, which just favorably affords increased water contents, antibacterial and antioxidant activities. GelMA-TP hydrogel is shown to facilitate wound healing in a full-thickness skin defect model. Importantly, the weak 3D printed GelMA scaffolds are significantly strengthened by TP treatment, broadening the possibility for customizing individualized bioscaffolds.