Cellular uptake and distribution of cobalt complexes of fluorescent ligands

Abstract

The development of complexes that allow the monitoring of the release and distribution of fluorescent models of anticancer drugs initially bound to cobalt(III) moieties is reported. Strong quenching of fluorescence upon ligation to cobalt(III) was observed for both the carboxylate- and the hydroximate-bound fluorophores as was the partial return of fluorescence following addition of ascorbate and cysteine. The extent of the increase in the fluorescence intensity observed following addition of these potential reductants is indicative of the fluorophore being displaced from the complex by the action of ascorbate or cysteine, by ligand exchange. The cellular distribution of the fluorescence revealed that coordination to cobalt can dramatically alter the subcellular distribution of a bound fluorophore. This work shows that fluorescence can be an effective means of monitoring these agents in cells, and of determining their sites of activation. The results also reveal that the cytotoxicity of such agents correlates with their uptake and distribution patterns and that these are influenced by the types of ligands attached to the complex.

Cobalt derivatives as promising therapeutic agents

“…Fluorescence return from a Co(III)/cyclam complex of coumarin-343 (c343) was observed in the same region as the fluorescently labeled hypoxic cells located within the core of the tumor models. This suggests that the release of the fluorophore payload is occurring at the correct site, validating the use of bioreductive Co(III) complexes for delivering anticancer agents to the target site [50,51*]. …”

“…The fluorescence of fluorophores such as coumarin-343 is quenched upon coordination to Co(III) but returns upon ligand release following reduction [50]. Kim et al .…”

Application of Metal Coordination Chemistry To Explore and Manipulate Cell Biology

“…Given the promise of using cobalt as a drug chaperone and the clear need to understand its mechanisms of cellular distribution and prodrug activation in order to rationally design effective agents, complexes with fluorescent ligands such as 54 were developed 234. In the example shown, a hydroxamic acid derivative of coumarin-343 mimics the hydroxamic acid motif of marimistat.…”

RoboSCell: an automated single cell arraying and analysis instrument

“…Detecting and analyzing the uptake or expression of biomolecules is an important analysis technique in biological experiments. This particular assay has been previously used to: determine cell viability (Dogan et al 2004, Holm et al 2006 or analyze the cytoxicity response of a cell to a compound (Yamamoto et al 2008) or detect cell morphologies (Eilken et al 2009). …”