2,4,5-Triaryl imidazole probes for the selective chromo-fluorogenic detection of Cu(II). Prospective use of the Cu(II) complexes for the optical recognition of biothiols

Lysosome-Targeting Fluorescence Sensor for Sequential Detection and Imaging of Cu2+ and Homocysteine in Living Cells

A conjugated polymer-based fluorescence sensor, namely, PTNPy, was constructed on the basis of a polythiophene scaffold coupled with dimethylpyridylamine (DPA) groups in side chains for the consecutive detection and quantification of Cu²⁺ and Hcy in a perfect aqueous medium. A dramatic fluorescence quenching of PTNPy by the addition of Cu²⁺ was observed in Tris-HCl buffer solution (2 mM, pH 7.4), demonstrating a quick (<1 min) and highly selective response to Cu²⁺ with a low limit of detection of 6.79 nM. Subsequently, the Cu²⁺-quenched fluorescence of PTNPy can be completely recovered by homocysteine (Hcy), showing excellent selectivity to Hcy over other competitive species such as cysteine and glutathione. Thanks to the low cytotoxicity and lysosomal targeting ability of PTNPy, it was further applied as an optical sensor for the sequential imaging of Cu²⁺ and Hcy in HeLa cells. More importantly, Hcy concentration was linearly related to the fluorescence intensity of PTNPy in living cells, demonstrating huge potential for real-time monitoring the fluctuation of Hcy levels in living cells.

Ruthenium(II) Complexes with (3-Polyamino)phenanthrolines: Synthesis and Application in Sensing of Cu(II) Ions

This work deals with the development of water-soluble optical sensors based on ruthenium(II) tris(diimine) complexes that exhibit high molar absorptivity and are emissive in aqueous media. Palladium-catalyzed arylation of polyamines with 3-bromo-1,10-phenanthroline (Brphen) and [Ru(bpy)2(Brphen)](PF6)2 (bpy = 2,2’-bipyridine) was explored to prepare Ru2+ complexes with 1,10-phenanthrolines (phen) substituted by linear polyamines (PAs) at position 3 of the heterocycle ([Ru(bpy)2(phen⎼PA)](PF6)2). The most convenient synthetic pathway leading to the target molecular probes includes the preparation of phen⎼PA ligands, followed by ruthenium complexation using cis-Ru(bpy)2Cl2. Complexes bearing a polyamine chain directly linked to phenanthroline core are emissive in aqueous media and their quantum yields are comparable to that of parent [Ru(bpy)3](PF6)2. Their structure can be easily adapted for detection of various analytes by modification of amine groups. As an example, we prepared the emissive complex Ru(N2P2phen) which is suitable for the dual channel (spectrophotometry and luminescence (ON–OFF probe)) selective detection of Cu2+ ions at the physiological pH levels with limits of detection (LOD) by spectrophotometry and fluorescence spectroscopy equal to 9 and 6 μM, respectively, that is lower than the action level in drinking water for copper as prescribed by the US Environmental Protection Agency.

Organic-inorganic hybrid sol-gel materials doped with a fluorescent triarylimidazole derivative

The development of sensors for pH monitoring is of extreme importance in the monitoring of concrete and reinforced concrete structures. Imidazole derivatives are promising probes for pH sensing due to the amphoteric nature of their heterocyclic ring, which can be protonated/deprotonated upon pH changes. In this work, a triarylimidazole was synthesised and used as a dopant in an organic–inorganic hybrid (OIH) sol–gel matrix to obtain a pH-sensitive membrane for further application in optical fibre sensors (OFS). The triarylimidazole probe shows fluorimetric response in pH between 9 and 13, which is the desired range for monitoring carbonation of concrete. This degradation process lowers the highly alkaline pH of concrete (12.5–13) to values below 9, which creates favourable conditions for corrosion of concrete reinforcement. The OIH membranes used were based on Jeffamine THF170 and 3-glycidoxypropytrimethoxysilane precursors, which had already been shown to be suitable and resistant in contact with cement-based materials. The OIHs were doped with three different contents of the triarylimidazole and the structural, dielectric, thermal and optical properties of the pure and doped OIH materials were evaluated. The structural analysis showed that the presence of the triarylimidazole did not change the structural properties of the OIH material. Electrochemical impedance spectroscopy showed that in the doped samples the conductivity increased with the imidazole concentration. The ε_r obtained for the doped samples ranged approximately from 11 to 19 and for the pure matrices was 8. Thermal analysis showed that these materials are stable up to 350 °C and that the presence of the probe did not change that feature. The optical properties showed that the prepared OIH materials have promising properties to be used as pH sensitive fluorimetric probes.

OIH sol–gel materials based on Jeffamine THF-170 and GPTMS, doped with triarylimidazole, were synthesized. The ε_r obtained for the OIH doped samples ranged between 11 and 19. The OIHs are thermally stable for fresh concrete purposes.

A novel fluorescent sensor for specific recognition of GSH based on the copper complex and its bioimaging in living cells

Given the important role of biothiols in various physiological processes, there is a need to develop novel fluorescent sensors for detecting them. Herein, a novel "on-off-on" fluorescent sensor (E)-N'-((7-(diethylamino)-2-oxo-2H-chromen-3-yl)methylene)-6-((quinolin-8-yloxy)methyl)picolinohydrazide (PQC) was synthesized and its absorbance and fluorescence properties were characterized. The sensor PQC could form a stable complex and showed a significant fluorescence quenching response to Cu²⁺ with a quenching efficiency of approximately 100%, and the PQC-Cu²⁺ complex showed a fluorescence enhancement response to GSH with a higher recovery rate of above 80% in a CH₃OH/HEPES (9:1 v/v, pH = 7.23) buffer system. Its detection limits were determined to be 0.17 μM for Cu²⁺ and 0.20 μM for GSH, and the binding stoichiometry of PQC-Cu²⁺ was determined to be 1: 1 by Job's plot method. Importantly, the sensor PQC can be used for filter paper strip tests and bioimaging in living cells.