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Red-Emitting Fluorescence Sensors for Metal Cations: The Role of Counteranions and Sensing of SCN- in Biological Materials

. 2019 Jun 28 ; 4 (6) : 1552-1559. [epub] 20190530

Language English Country United States Media print-electronic

Document type Journal Article, Research Support, Non-U.S. Gov't

The spatiotemporal sensing of specific cationic and anionic species is crucial for understanding the processes occurring in living systems. Herein, we developed new fluorescence sensors derived from tetrapyrazinoporphyrazines (TPyzPzs) with a recognition moiety that consists of an aza-crown and supporting substituents. Their sensitivity and selectivity were compared by fluorescence titration experiments with the properties of known TPyzPzs (with either one aza-crown moiety or two of these moieties in a tweezer arrangement). Method of standard addition was employed for analyte quantification in saliva. For K+ recognition, the new derivatives had comparable or larger association constants with larger fluorescence enhancement factors compared to that with one aza-crown. Their fluorescence quantum yields in the ON state were 18× higher than that of TPyzPzs with a tweezer arrangement. Importantly, the sensitivity toward cations was strongly dependent on counteranions and increased as follows: NO3- < Br- < CF3SO3- < ClO4- ≪ SCN-. This trend resembles the chaotropic ability expressed by the Hofmeister series. The high selectivity toward KSCN was explained by synergic association of both K+ and SCN- with TPyzPz sensors. The sensing of SCN- was further exploited in a proof of concept study to quantify SCN- levels in the saliva of a smoker and to demonstrate the sensing ability of TPyzPzs under in vitro conditions.

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