High nuclearity carbonyl clusters as near-ir contrast agents for photoacoustic in vivo imaging

High nuclearity carbonyl clusters of ruthenium and osmium are found to exhibit good photoacoustic (PA) activity in the near-IR (NIR) region. Their potential as PA contrast agents for full body imaging has been demonstrated for the first time with mice; intravenous administration of the osmium carbonyl cluster Na-2[Os-10(mu(6)-C)(CO)(24)] afforded up to a four-fold enhancement of the PA signal in various tissues. The cluster exhibits low toxicity, high stability and superior PA stability compared to the clinically approved NIR dye, indocyanine green