A highly selective turn-on fluorescent sensor for Cu(ii) based on an NSe2 chelating moiety and its application in living cell imaging

Abstract

In this study, a boron-dipyrromethene (BODIPY)-based fluorescent chemosensor CBS was developed for metal ion sensing. It was found that CBS containing an NSe₂ moiety exhibited high selectivity for Cu²⁺ detection while CBS in the presence of Cu²⁺ displayed significant fluorescence enhancement. However, the metal ions Ag⁺, Ca²⁺, Co²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Hg²⁺, K⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in the fluorescence values of the system. The binding constant (K_a) of Cu²⁺ binding to CBS was found to be 7.28 × 10³ M⁻¹. The binding ratio of CBS–Cu²⁺ complexes was determined from the Job plot to be 1 : 1. The maximum fluorescence enhancement caused by Cu²⁺ binding to CBS was observed over the pH range 5.0–9.0. Additionally, the methyl thiazolyl tetrazolium (MTT) assay demonstrated the CBS to have low cytotoxicity. Confocal fluorescence microscopy imaging using RAW264.7 cells showed that CBS could be used as an effective fluorescent probe for detecting Cu²⁺ in living cells.