Long Wavelength Phototriggering: Ruthenium-Based Caged Compounds

Abstract

Here we describe the use of Ru polypyridine compounds as caging agents for a variety of molecules. The photorelease of the caged molecule can be triggered using visible light (450-500 nm) with a high quantum yield. These caged compounds are very stable in aqueous environments and yield the molecule of interest intact in a single step without secondary reactions. The affinity of the Ru polypyridine for amine groups allows the caging of a variety of molecules, including neurochemicals and neurotransmitters like 4-aminopyridine, glutamate, gamma aminobutyric acid, glycine, serotonin, dopamine, and nicotine. These caged molecules have been used to elicit the response of neurons, both in vitro and in vivo experiments. Besides neurotransmitters other types of molecules, like antiproliferative drugs, can also be caged. In addition, sulfur-containing molecules, such as methylthiogalactose, can also be caged by this fragment. Another interesting application of the Ru polypyridine fragment is the caging of fluorescent dyes which can be uncaged using visible light. All of these applications can also be implemented using infrared light, as one of the distinctive advantages of Ru polypyridines as caging agents is their ability to be triggered in a two-photon regime, allowing the use of high power IR pulses to uncage the desired molecule.