A New Fluorescent Chemosensor for Cobalt(II) Ions in Living Cells Based on 1,8-Naphthalimide

• Main Authors: Yu-Long Liu, Liu Yang, Lu Li, You-Quan Guo, Xiao-Xiao Pang, Ping Li, Fei Ye, Ying Fu
• Format: Article
• Language: English
• Published: MDPI AG 2019-08-01
• Series: Molecules
• Subjects: 1,8-naphthalimide; colorimetric; fluorescent; cobalt(II) ions; live cell imaging
• Online Access: https://www.mdpi.com/1420-3049/24/17/3093

In this work, a highly selective fluorescent chemosensor <i>N</i>-(2-(2-<i>butyl</i>-1,3-dioxo-2,3-dihydro-1<i>H</i>-benzo[<i>de</i>]isoquinolin-6-yl)hydrazine-1-carbonothioyl)benzamide (<b>L</b>) was prepared and characterized. An assay to detect the presence of cobalt(II) ions was developed by utilizing turn-on fluorescence enhancement with visual colorimetric response. Upon treatment with Co²⁺, a remarkable fluorescence enhancement located at 450 nm was visible to naked eyes accompanied with a distinct color change (from pink to colorless) in a CH₃CN/HEPES (4/1, <i>v</i>/<i>v</i>, pH = 7.4) solution due to the formation of a 1:1 complex at room temperature. In addition, the linear concentration range for Co²⁺ was 0&#8722;25 &#181;M with the limit of detection down to 0.26 &#181;M. Thus, a highly sensitive fluorescent method based on chelation-assisted fluorescence enhancement was developed for the trace-level detection of Co²⁺. The sensor was found to be highly selective toward Co²⁺ ions with a large number of coexisting ions. Furthermore, the <b>L</b> probe can serve as a fluorescent sensor for Co²⁺ detecting in biological environments, demonstrating its low toxic properties to organisms and good cell permeability in live cell imaging.