Monofunctional near-infrared fluorochromes for imaging applications

In this report, the development of a new class of monocarboxylate functionalized cyanine derivatives using improved synthetic procedures is detailed. The employed synthetic strategy relies on efficient nucleophilic attack of alkyl-thiols on cyanine dyes bearing chloro-substituted polymethinic linkers. Monocarboxylate derivatized fluorochromes (CyTE dyes) can be prepared in one step in greater than 90% yield without the need for additional purification. Several of the fluorochromes synthesized by this route show no tendency to aggregate in aqueous solution and have excitation and emission maxima greater than 800 nm. The potential utility of the CyTE fluorochromes was demonstrated through direct labeling of phage displaying a vascular cellular adhesion molecule-1 (VCAM-1) targeting peptide. Endothelial cell internalization of the VCAM-1 targeted phage was monitored via near-infrared fluorescence microscopy.