Calcium-mediated secondary cross-linking of bisphosphonated oligo(poly(ethylene glycol) fumarate) hydrogels

This study demonstrates, for the first time, that synthetic PEG-based hydrogels can be cross-linked reversibly by calcium upon functionalization of the polymer backbone with bisphosphonate groups (BPs) that allow for the formation of strong coordination bonds with divalent metal ions such as Mg(2+) and Ca(2+). More specifically, it is shown that BP-functionalized hydrogels can be shaped by providing calcium ions as reversible physical cross-linkers.