Ultrasensitive Reagent for Ratiometric Detection and Detoxification of iAs III in Water and Mitochondria.

Toxicity induced by inorganic arsenic as AsO 3 3- ( iAs III ) is of global concern. Reliable detection of the maximum allowed contaminant level for arsenic in drinking water and in the cellular system remains a challenge for the water quality management and assessment of toxicity in the cellular milieu, respectively. A new Ir(III)-based phosphorescent molecule ( AS-1 ; λ Ext = 415 nm and λ Ems = 600 nm, Φ = 0.3) is synthesized for the selective detection of iAs III in an aqueous solution with a ratiometric luminescence response even in the presence of iAs V and all other common inorganic cations and anions. The relatively higher affinity of the thioimidazole ligand (HPBT) toward iAs III led to the formation of a fluorescent molecule iAs V -HPBT (λ Ext = 415 nm and λ Ems = 466 nm, Φ = 0.28) for the reaction of iAs III and AS-1 . An improved limit of quantitation (LOQ) down to 0.2 ppb is achieved when AS-1 is used in the CTAB micellar system. Presumably, the cationic surfactants favor the localization of AS-1 @CTAB Micelle in mitochondria of MCF7 cells, and this is confirmed from the images of the confocal laser fluorescence scanning microscopic studies. Importantly, cell viability assay studies confirm that AS-1 @CTAB Micelle induces dose-dependent detoxification of iAs III in live cells. Further, luminescence responses at 466 nm could be utilized for developing a hand-held device for the in-field application. Such a reagent that allows for ratiometric detection of iAs III with LOQ of 2.6 nM (0.5 ppb) in water, as well as helps in visualizing its distribution in mitochondria with a detoxifying effect, is rather unique in contemporary literature.