Bioadhesion

Bioadhesion describes the attachment of biological materials to surfaces or to other tissues. It encompasses cell-cell adhesion, mediated by cell adhesion molecules such as cadherins, integrins, and selectins, and cell-matrix interactions, including binding to extracellular matrix proteins. Bioadhesion also refers to attachment of tissues or organisms to biomaterials and mucosal surfaces. Natural examples include mussel adhesive proteins that function in wet environments and, conceptually, dry adhesives inspired by geckos. In research and medicine, bioadhesion is studied to understand tissue cohesion and to design compatible interfaces with living systems.

Adhesion arises from covalent bonds in some bioadhesives and from non-covalent interactions such as electrostatic forces, hydrogen bonding, hydrophobic effects, and van der Waals interactions. Mechanical interlocking with surface roughness and disruption of hydration layers also contribute, particularly on wet surfaces. Adhesion performance depends on surface chemistry, topography, moisture, pH, ionic strength, and temperature, as well as the properties of the interacting materials. Natural bioadhesives are adapted to aqueous environments, whereas synthetic systems aim for biocompatibility, tunable strength, biodegradability, and controlled degradation.

Applications include mucoadhesive drug delivery, tissue sealants and wound closure, and scaffolds that promote tissue integration. Common methods to assess bioadhesion in the lab include lap shear, peel, and tensile strength tests, as well as burst pressure for seals, and measurements of surface energy. Challenges include achieving durable adhesion in dynamic, wet biological conditions, avoiding immune reactions, and balancing strength with biodegradability. Ongoing research integrates biology and materials science to understand adhesion mechanisms and to develop new bioadhesive technologies.