A Highly Selective Fluorescent Probe for Hg²⁺ Based on a 1,8-Naphthalimide Derivative

Area of Science:

• Analytical Chemistry
• Environmental Science
• Biochemistry

Background:

• Mercury ions (Hg2+) pose significant environmental and ecological risks.
• Sensitive and selective detection methods for mercury are crucial for biological and environmental monitoring.
• Existing methods may lack the required sensitivity or selectivity for complex samples.

Purpose of the Study:

• To develop a novel "turn-on" fluorescent probe for the selective and sensitive detection of mercury ions (Hg2+).
• To utilize a specific Hg2+-triggered thioacetal deprotection reaction for probe design.
• To demonstrate the probe's applicability in environmental and cellular imaging.

Main Methods:

• Design and synthesis of a naphthalimide-based fluorescent probe incorporating a 1,2-dithioalkyl recognition site.
• Investigation of the probe's fluorescence response to Hg2+ in solution, including colorimetric changes.
• Evaluation of the probe's sensitivity, selectivity, and performance across a wide pH range.
• Determination of the linear detection range and limit of detection for Hg2+.
• Assessment of the probe's cell viability and its application in confocal imaging of intracellular Hg2+.

Main Results:

• The probe exhibited weak fluorescence in the absence of Hg2+ (light yellow solution).
• Upon addition of Hg2+, the probe underwent specific thioacetal deprotection, producing strong fluorescence emission (light green solution).
• The probe demonstrated high sensitivity and selectivity towards Hg2+.
• A linear correlation between fluorescence intensity and Hg2+ concentration was observed from 2.5 × 10^-7 to 1.0 × 10^-5 M, with a detection limit of 4.0 × 10^-8 M.
• The probe functioned effectively over a broad pH range and showed minimal cytotoxicity, enabling successful imaging of Hg2+ in PC-12 cells.

Conclusions:

• A novel, highly sensitive, and selective "turn-on" fluorescent probe for Hg2+ detection has been successfully developed.
• The probe's design, based on specific Hg2+-triggered thioacetal deprotection, allows for reliable mercury ion monitoring.
• The probe's broad pH applicability and successful application in cellular imaging highlight its potential for environmental and biological analyses.