Fluorescent drug screening based on aggregation of DNA-templated silver nanoclusters, and its application to iridium (III) derived anticancer drugs

We describe a screening method for DNA-targeted anticancer drugs in vitro by using DNA-templated silver nanoclusters (DNA/AgNCs) as a fluorescent probe. It was found that the fluorescence of DNA/AgNCs decreases during the transition of AgNCs from the dispersed to the aggregated state which is the case if the DNA/AgNC-drug complex is formed. The formation of this complex was studied by resonance light scattering (RLS) spectroscopy. The method was applied to a series of organometallic iridium (III) compounds (IrC). Sensitive detection of IrC with the detection limit of 10(-11) molI double dagger L-1 was achieved. The dependence of RLS intensity on IrC amount was successfully utilized to investigate the interactions between IrC and DNA. In addition, assays on cell toxicity and cell apoptosis revealed the anticancer activity of IrC. Specifically, it is found that the iridium (III) bis[2-(4,6-difluorophenyl)pyridinato-N,C-2']-picolinate complex is a promising candidate for further evaluation as a chemotherapeutic agent. This strategy is reliable, sensitive, and may form the basis for rapid screening of libraries for anti-cancer drugs.