Near infrared active heptacyanine dyes with unique cancer-imaging and cytotoxic properties

Three near-infrared fluorescent heptacarbocyanine dyes have been synthesized using a facile one-pot synthetic approach. The reaction methodology afforded a mixture of three symmetric and unsymmetric heptacyanines containing various N-indolenine substituents, a dicarbocyclic acid (DA), a monoester (ME), and a diester (DE). These compounds were isolated, purified, characterized and biologically investigated for tumor cell cytotoxicity and uptake selectivity. Using cell viability and in vitro proliferation assays, we found that the esterified dyes (monoester, ME and diester, DE) were selectively cytotoxic to cancer cells and spared normal fibroblast cells. Additionally, confocal fluorescence imaging confirmed selective uptake of these dyes in cancer cells, thus suggesting tumor cell targeting.