Calix[4]arene based a NIR-fluorescent sensor with an enhanced stokes shift for the real-time visualization of Zn(II) in living cells

Zinc(II) plays key roles actively involved in fundamental biological functions in the body. However, zinc dysmetabolism results in a number of human diseases. Therefore, miscellaneous techniques are needed to understand the complete biological role of Zn(II) in tissues and cells. Here, we introduce a novel calix[4]arene derivative (CIP), appended with two isophorone units via a 4-bromophenol linker for the fluorescence sensing Zn (II). CIP showed high fluorogenic selectivity for Zn(II) over a wide range of biologically and environmentally relevant metal ions in DMSO/H2O (v/v, 8/2, PBS buffer, 0.5 mM, pH 7.4) and has superior sensitivity of (6.75 nM) for Zn(II). Free CIP has very low emission but demonstrated the distinct "turn-on" emission enhancement response toward Zn(II) at near infrared region. CIP allowed the fabrication of a rapid and convenient TLC strip sensor for Zn(II)-selective detection. Moreover, this is the first report on a calix[4]are derivative used as a NIR fluorescence probe that monitors changes in intracellular Zn(II) levels and can penetrate into living cells.