A
cross-link is a bond that links one
polymer chain to another. They can be
covalent bonds or
ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers (such as
proteins). When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of cross-links to promote a difference in the polymers' physical properties. When "crosslinking" is used in the biological field, it refers to the use of a probe to link proteins together to check for
protein–protein interactions, as well as other creative cross-linking methodologies.