Gluing dynamic, wet
biological tissue is important in injury treatment
yet difficult to achieve. Polymeric adhesives are inconvenient to
handle due to rapid cross-linking and can raise biocompatibility concerns.
Inorganic nanoparticles adhere weakly to wet surfaces. Herein, an
aqueous suspension of guanidinium-functionalized chitin nanoparticles
as a biomedical adhesive with biocompatible, hemostatic, and antibacterial
properties is developed. It glues porcine skin up to 3000-fold more
strongly (30 kPa) than inorganic nanoparticles at the same concentration
and adheres at neutral pH, which is unachievable with mussel-inspired
adhesives alone. The glue exhibits an instant adhesion (2 min) to
fully wet surfaces, and the glued assembly endures one-week underwater
immersion. The suspension is lowly viscous and stable, hence sprayable
and convenient to store. A nanomechanic study reveals that guanidinium
moieties are chaotropic, creating strong, multifaceted noncovalent
bonds with proteins: salt bridges comprising ionic attraction and
bidentate hydrogen bonding with acidic moieties, cation−π
interactions with aromatic moieties, and hydrophobic interactions.
The adhesion mechanism provides a blueprint for advanced tissue adhesives.