Injectable gelatin-oligo-catechol conjugates for tough thermosensitive bioadhesion

Extracellular matrix-derived biomaterials, such as gelatin-based hydrogels, are attractive candidates for sealing internal leakages. However, gelatin derivatives are brittle and suffer from poor adhesion. Modifications of gelatin with adhesive catechol moieties have been limited to low degrees of substitution. Here, we propose oxidative oligomerization of catecholic compounds (namely, caffeic acid [CA]) prior to the coupling reaction to augment the number and availability of grafted catechol groups per carbodiimide conjugation reaction, thereby achieving robust bioadhesion. Ex vivo adhesion tests on pig lungs suggests ∼3× improvement in adhesion strength compared with gelatin methacryloyl controls due to their enhanced cohesion (i.e., ∼5.3× and ∼11.5× improvements in stretchability and toughness, respectively). Functionalization of gelatin with CA oligomers enables rapid formation of physical gels upon exposure to room temperature, tunes the viscosity of the gelatin-caffeic acid pre-gel solution for controllable injectability onto multiply curved tissues, and boosts the antioxidant effects of CA.