A gadolinium(iii) complex based dual-modal probe for MRI and fluorescence sensing of fluoride ions in aqueous medium and in vivo

Abstract

A novel Gd(iii) complex, Gd(TTA)-DPPZ, was designed and assembled as a dual-modal probe for the simultaneous fluorescence and magnetic resonance imaging (MRI) detection of fluoride ions in aqueous media and in vivo. In this system, the Gd(iii) center is not only serving as a MRI signal output unit, but also as a binding site for fluoride ions. When appropriate equivalents of fluoride ions were added into the solution of Gd(TTA)-DPPZ, the replacement of the coordination water led to a decrease of the longitudinal relaxivity (r) as well as distinct spectroscopic changes, by which MRI/fluorescence dual-modal fluoride ion sensing was achieved. In the presence of fluoride ions, a 2-fold fluorescence emission enhancement of Gd(TTA)-DPPZ, and a notable decrease of the UV-vis absorption spectrum were observed. The fluorescence detection limit for fluoride ions was established at 70 nM. Gd(TTA)-DPPZ also exhibits about 75% decrease of the longitudinal relaxivity (r) upon addition of fluoride ions in aqueous medium. The appropriate blood circulation time of Gd(TTA)-DPPZ allows its potential application in MRI in vivo. The results demonstrated that Gd(TTA)-DPPZ could serve as a potential MRI/fluorescence bimodal imaging agent for the specific and high-sensitive sensing of fluoride ions in vivo.

Receptor‐Spacer‐Fluorophore Based Coumarin‐Thiosemicarbazones as Anion Chemosensors with “Turn on” Response: Spectroscopic and Computational (DFT) Studies

“…And while many such instrument‐based methods exist, the area of small molecule chemosensors for selective fluoride ion detection is relatively under‐explored. A range of different types of molecules having urea, imidazole, pyrrole, indole and thiourea moiety have been reported as chemosensors for various type of anions/cations ,. Thiosemicarbazone moiety, by virtue of having acidic NH protons, shows a very strong binding interaction with small anions particularly F̄ ions.…”

Fluorescent “Turn-Off” Detection of Fluoride and Cyanide Ions Using Zwitterionic Spirocyclic Meisenheimer Compounds

“…In this sense, there are several promising anion chemosensors based on colorimetric changes or change in fluorescence. These gadolinium (III) organometallic complex-based sensors found promising use for in vivo imaging and fluorescence detection of biologically harmful fluoride ions [ 12 , 13 , 14 ]. Note that excess fluoride ions in biological fluids and tissues can lead to fluorosis and osteoscaroma, whereas a fluoride deficiency causes osteoporosis and poor dental health [ 15 ].…”

Recent developments in multimodality fluorescence imaging probes

“…However, the probe accumulation in the tumors were only detected by OFI, but not MRI, suggesting the necessity for further improvement of the local concentration of MRI contrast agents. Gadolinium(III)-fluorescent dye complexes can also function as activatable MRI and OFI probes for ion detection through ion exchange reaction 58 , 59 , 60 . During the process, the fluorescent dye changes from coordination with Gd(III) to free state or complexation with another metal cation, and generates fluorescence change.…”