Illuminating Tiny Bone Breaks

The first luminescent lanthanide contrast agent capable of imaging microcracks in bone has been developed by chemists in Ireland (J. Am. Chem. Soc., DOI: 10.1021/ja908006r). The cyclen-based europium compound could be used for bone structure analysis, lighting up barely visible fractures caused by repetitive loading and stress. Trinity College Dublin’s Thorfinnur Gunnlaugsson and coworkers constructed the contrast agent so that it contains three iminodiacetate moieties hanging off the cyclen ring. These groups selectively bind to exposed calcium sites in the damaged bone’s hydroxyapatite matrix, and a covalently linked naphthalene antenna sensitizes europium to its excited state. The researchers were able to differentiate polished and scratched bone four hours after exposure to the complex using confocal fluorescence laser-scanning microscopy. Gunnlaugsson tells C&EN that his group is currently developing the imaging agent for use in living systems.