Bioinspired bioadhesion: translating nature's adhesive strategies into regenerative medicine

In nature, many organisms, such as mussels, geckos, tree frogs, octopuses, and salamanders, have evolved remarkable bioadhesion strategies, that enable them to attach to wet environments, climb vertical or inverted surfaces, and capture preys. These strategies rely on chemical interactions mediated by secreted bioadhesives as well as physical forces, including but not limited to friction, van der Waals interactions, capillary forces, and vacuum suction, arising from specialized micro- and nanostructures. Chemical bioadhesives, composed of proteins, polysaccharides, or other macromolecules, facilitate strong, reversible or irreversible adhesion to wet or dynamic surfaces, as exemplified by mussel byssal threads and tree frog toe pad mucus. These adhesives act through mechanisms such as covalent bonding, metal coordination, hydrogen bonding, and electrostatic interactions. This review outlines recent advances in both chemical and physical bioadhesion strategies. We examine the adhesion principles used by mussels, geckos, tree frogs, octopuses, and other organisms that secrete adhesive chemicals, emphasizing the roles of micro- and nanostructures, interfacial forces, and soft contact mechanics. We also present design strategies for creating artificial adhesives inspired by these biological systems and describe their applications in regenerative medicine. Finally, we discuss current challenges and future directions in bioinspired and chemically based adhesion.