A 7-nitrobenz-2-oxa-1,3-diazole based highly sensitive and selective turn-on chemosensor for copper(ii) ion with intracellular application without cytotoxicity

Abstract

A 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived turn-on fluorescent probe (1) exhibits a reversible binding to Cu²⁺ ion in presence of other metal ions, giving ∼20 fold increase in fluorescence intensity. The apparent association constant (K_a) for Cu²⁺ was found to be 2.62 × 10⁴ M⁻¹. The intracellular Cu²⁺ imaging behaviour of chemosensor 1 on HeLa cells studied by fluorescence microscopy revealed that after incubation with 1 cells exhibited intensive fluorescence when exogenous Cu²⁺ was introduced into the cell. Thus this probe features the ready availability, high sensitivity and selectivity towards Cu²⁺ in MeCN–H₂O (1 : 1, v/v) with cell imaging possibilities with no or negligible cytotoxicity.