Wet tissue adhesive hydrogel toughened by wheat gluten

Tissue adhesives made of natural polymers like protein have good biocompatibility but low adhesion in wet environments. Gluten is a rich naturally occurring protein with a highly soft and stretchable "loop and train" model network. To benefit from this remarkable feature, it was composited with poly(acrylic acid) (PAA) to make a tough double-network wet tissue adhesive hydrogel (G-PAA). The hydrogen bonds and electrostatic interactions between gluten and PAA rendered it with high tensile strength, toughness, energy dissipation capacity and fatigue resistance (stress: ∼5.1 MPa, strain: ∼274 %, and toughness: ∼8.3 MJ/m³). The gluten network imparted additional adhesive functional groups (-NH₂, -OH and -COOH) and hydrophobic moieties to the G-PAA hydrogel. The hydrogel could adhere to various wet biological tissues including porcine skin, liver, kidney and heart. And the adhesion strength of G_5.5-PAA₈₀ in the lap-shear test and the interfacial toughness in the 180° peel test on wet porcine skin can reach 82 kPa and 97 J/m², respectively. Furthermore, G-PAA hydrogel demonstrated tissue sealing, on-demand detachment and biocompatibility. Therefore, this study provides new formulas and structure for the design of adhesive hydrogel with good wet tissue adhesion.