An activatable NIR turn-on fluorescent probe for copper (II) ion and live cell imaging

Herein we have reported a fluorescent probe (MB-M) based on MB derivative for Cu²⁺ ions detection. The probe was well characterized by ¹H NMR, ¹³C NMR and HR-MS spectrum. Probe MB-M showed naked-eyes recognition to Cu²⁺ as color change from colorless to indigo. The probe exhibited promising features such as high fluorescence and UV-vis selectivity, fast response (5 mint), workable at pH 2-7, and low limit of detection (LOD = 0.33 µM). Probe MB-M was also used for Cu²⁺ ions imaging in HepG-2 cells and detection in daily life (Test Strip and lake water). Moreover, non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analysis were used to study the interaction between MB-M and Cu²⁺ ions. By examining the electronic characteristics of the complex using natural bond orbital (NBO), electron density difference (EDD), and frontier molecular orbital (FMO) analysis, the sensitivity of MB-M towards Cu²⁺ ions were investigated. The results illustrated that the interactions between MB-M and Cu²⁺ ions involved chemisorption.