A Naphthalimide-Based Hypochlorous Acid-Selective Fluorescent Probe and Its Application in Cell Imaging

A novel naphthalimide-based fluorescence probe ethyl (E)-3-(2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-5-yl)-2-cyanoacrylate (NAEC) containing C=C double bond group with intramolecular charge transfer (ICT) effect for hypochloric acid detection was synthesized, which could selectively and sensitively respond to hypochloric acid within 10 s in phosphate buffer saline (PBS) buffer solution [N,N-dimethylformamide (DMF)/PBS (V:V=1:19), pH= 7.4]. The mechanism is that the C=C double bond in the probe can be oxidized and turned to aldehyde group, then the original ICT effect of probe is destroyed, and the fluorescence of naphthalimide restores. The spectroscopic properties of the probe NAEC towards ClO- were studied through UV-vis absorption and fluorescence emission spectroscopies. The results showed that the probe NAEC possessed a large pseudo Stokes shift (100 nm) and the limit of detection (LOD) for NAEC has been estimated to be 2.4 nmol/L. In addition, the probe exhibited good response and anti-interference performance for hypochloric acid in the presence of 22 kinds of interferences, such as other reactive oxygen, small molecule biosulphol and common anions. And probe NAEC exhibited good cell permeability and was successfully applied in living cells by fluorescence imaging. The method is expected to be extended to the diagnosis of diseases and the detection in environmental samples, etc.