Monitoring Hg2+and MeHg+ poisoning in living body with an activatable near-infrared II fluorescence probe

Noninvasively imaging mercury poisoning in living organisms is critical to understanding its toxicity and treatments. Especially, simultaneous fluorescence imaging of Hg2+ and MeHg+ in vivo is helpful to disclose the mysteries of mercury poisoning. The key limitation for mercury imaging in vivo is the low imaging signal-to-background ratio (SBR) and limited imaging depth, which may result in unreliable detection results. Here, we designed and prepared a near-infrared II (NIR II) emissive probe, NIR-Rh-MS, leveraging the spirolactam ring-open tactic of xanthene dyes for in situ visualization of mercury toxicity in mice. The probe produces a marked fluorescence signal at 1015 nm and displays good linear responses to Hg2+ and MeHg+ with excellent sensitivity, respectively. The penetration experiments elucidate that the activated NIR-II fluorescence signal of the probe penetrates to a depth of up to 7 mm in simulated tissues. Impressively, the probe can monitor the toxicity of Hg2+ in mouse livers and the accumulation of MeHg+ in mouse brains via intravital NIR-II imaging for the first time. Thus, we believe that detecting Hg2+ and MeHg+ in different organs with a single NIR-II fluorescence probe in mice would assuredly advance the toxicologic study of mercury poisoning in vivo.

Automated summary

Noninvasively imaging mercury poisoning in living organisms is critical to understanding its toxicity and treatments. Especially, simultaneous fluorescence imaging of Hg2+ and MeHg+ in vivo is helpful to disclose the mysteries of mercury poisoning. A new near-infrared II (NIR II) emissive probe, NIR-Rh-MS, has been designed to visualize mercury toxicity in mice. The probe produces a marked fluorescence signal and displays good sensitivity to Hg2+ and MeHg+. It can penetrate deep into simulated tissues and has successfully monitored the toxicity of Hg2+ in mouse livers and the accumulation of MeHg+ in mouse brains via intravital NIR-II imaging.