Zn²⁺-Triggered Amide Tautomerization Produces a Highly Zn²⁺-Selective, Cell-Permeable, and Ratiometric Fluorescent Sensor

Abstract

It is still a significant challenge to develop a Zn(2+)-selective fluorescent sensor with the ability to exclude the interference of some heavy and transition metal (HTM) ions such as Fe(2+), Co(2+), Ni(2+), Cu(2+), Cd(2+), and Hg(2+). Herein, we report a novel amide-containing receptor for Zn(2+), combined with a naphthalimide fluorophore, termed ZTRS. The fluorescence, absorption detection, NMR, and IR studies indicated that ZTRS bound Zn(2+) in an imidic acid tautomeric form of the amide/di-2-picolylamine receptor in aqueous solution, while most other HTM ions were bound to the sensor in an amide tautomeric form. Due to this differential binding mode, ZTRS showed excellent selectivity for Zn(2+) over most competitive HTM ions with an enhanced fluorescence (22-fold) as well as a red-shift in emission from 483 to 514 nm. Interestingly, the ZTRS/Cd(2+) complex showed an enhanced (21-fold) blue-shift in emission from 483 to 446 nm. Therefore, ZTRS discriminated in vitro and in vivo Zn(2+) and Cd(2+) with green and blue fluorescence, respectively. Due to the stronger affinity, Zn(2+) could be ratiometrically detected in vitro and in vivo with a large emission wavelength shift from 446 to 514 nm via a Cd(2+) displacement approach. ZTRS was also successfully used to image intracellular Zn(2+) ions in the presence of iron ions. Finally, we applied ZTRS to detect zinc ions during the development of living zebrafish embryos.

Colorimetric and fluorescent anion sensors: an overview of recent developments in the use of 1,8-naphthalimide-based chemosensors

“…Similarly, 7 showed large changes in the absorption and the emission spectra of the naphthalimide moiety upon sensing of Cu(II), 47 while the mononaphthalimide analogue has recently been shown to be a sensor for Zn(II). 48 These examples are all based on the use of 4-amino-1,8-naphthalimide structures, where the focus has been on the detection of cations, but the 3-amino-1,8-naphthalimide structures have also been employed in such sensing, as demonstrated elegantly by de Silva et al 49 4-Amino-1,8-naphthalimide-based urea and thiourea sensors for anions…”

A Zinc(II) Photocage Based on a Decarboxylation Metal Ion Release Mechanism for Investigating Homeostasis and Biological Signaling

“…To demonstrate metal ion release, [Zn(NTAdeCage)] − was photolyzed and ZTRS, [32] a fluorescent Zn 2+ sensor (K d = 5.7 nM) was used to monitor increases in available Zn 2+ (Figure S11 and S12). Aliquots from a bulk [Zn(NTAdeCage)] − solution being photolyzed were analyzed owing to ZTRS photobleaching that occurred when the sensor was exposed to the light source for uncaging.…”

A New Luminescent Ruthenium(II) Polypyridine‐derived Dipicolylamine Complex as a Sensor for Cu2+ Ions

“…of Cu 2＋ , also suggesting a ratio of 1∶2 in the bonding between 1 and Cu 2＋ ions (Figure 2, inset a). On the other hand, the binding constant (K s ) was calculated as 5.89 ×10 4 L•mol -1 according to the formula Furthermore, the selectivity of the interaction was also studied using an additional series of metal ions such as Zn [16][17][18][19][20] However, very weak variations of absorption and emission spectra were observed upon addition of 2 equiv. of Zn 2＋ ions and other metal ions ( Figure 3) 27,28 as an elongated octahedral with three N atoms of DPA and three O atoms (from a water, a carbonyl group and a nitrate).…”

“…It is well known that di(2-picolyl)amine (DPA) moiety in particular has been widely employed because of its specificity for Zn 2 ＋ over other metal ions. [16][17][18][19][20] Herein, a Ru(II) polypyridyl complex 1 ([Ru(bpy) 2 (bpy-DPF)](PF 6 ) 2 ) with two DPAs as the recognition group, which are connected to the 4,4'-positions of the bipyridine unit through C＝O, was synthesized and characterized (Scheme 1). Interestingly, this Ru(II) polypyridyl complex demonstrates good selectivity and sensitivity to Cu 2＋ ions by the spectroscopic properties of 1 in response to different metal ions including Zn 23 were prepared by the methods described in the literatures and confirmed by 1 H NMR spectra.…”