Ruthenium-cross-linked hydrogels for rapid, visible-light protein release.

Ruthenium (Ru) polypyridyl complexes are described that present chemically reactive moieties on one or two photolabile ligands for engineering photoresponsive molecules or materials. Ru-cross-linkers can form hydrogels, with proteins or other biomolecules embedded. In this way, the protein is "caged" until released with light. By varying the coordinated ligands, Ru-cross-linkers have 1-photon absorption maxima that are tunable across the visible spectrum and into the near-infrared, which enables photoactivation at multiple, different wavelengths (i.e., multiplexing).