Real-time tracking and early diagnosis of mercury(II) exposure via a novel NIR-based fluorescent probe based on thiahemicyanine dye.

Ultrasensitive monitoring of mercury(II) (Hg2+) in environmental and biological systems is highly desirable due to the fact that this heavy metal ion is a ubiquitous pollutant worldwide. Despite the existence of numerous readily-available techniques for Hg2+-detection, optical probe-based fluorescence tracking stands out, as this powerful tool can offer the distinct advantages of real-time, noninvasive and particularly in vivo monitoring. Herein, a novel hemicyanine-based fluorescent probe (namely HDS-Hg) with an enhanced turn-on near-infrared (NIR) sensing of fluorescence response upon binding with Hg2+ (λex/λem = 700 nm/765 nm) was constructed, which featured a rapid response, low detection limit, wide pH-tolerance, high sensitivity and selectivity as well as favorable mitochondria-targeting ability. Probe HDS-Hg worked well in monitoring of Hg2+ in environmental water samples, herbs, seafoods and living cells. Notably, HDS-Hg could serve as the first fluorescent probe that can visualize the dynamic fluctuations of Hg2+ levels within tobacco seedling leaves. With the aid of HDS-Hg, real-time monitoring of the Hg2+-induced liver injury in a chronic mercury poisoning mouse model was also achieved. Undoubtedly, the presented work not only provides a robust imaging tool for detecting Hg2+ in complex environmental and in vivo biological samples, but most importantly it offers critical insights into chronic mercury poisoning.