Catechol Conjugation for Bioadhesion in Photo-Cross-Linkable Biomaterials

Inspired by mussel adhesion, catechol functionalization of different biomacromolecules has become a popular technique to impart adhesion to biomaterials. However, the bioadhesion capacity of catechol motifs in hydrogels that cross-link through free-radical-based systems is debated. Here, we revisit the bioadhesion efficacy of catechol functionalization in methacryloyl-modified photo-cross-linkable biomaterials. For this purpose, gelatin biomolecules functionalized with caffeic acid (CA) and methacryloyl groups are cross-linked using UV light to assess their cross-linking and bioadhesion. Despite the typical emphasis on wet adhesion of catecholic biomaterials, samples with larger catechol content showed lower adhesion strength, particularly when bioadhesives are cross-linked in situ as injectable sealants. Cross-linking was found to decay toward the interface with the substrates as more catechol groups are introduced to the hydrogels, which further undermines hydrogel integrity and adhesive bonds. Finally, cytotoxic and immunostimulatory effects associated with the catechol groups are evaluated for their translational potential in clinical applications.