A multi-ion fluorescent probe for Mg2+/Zn2+ based on a novel chromone-dendron Schiff base

The Monitoring and Cell Imaging of Fe3+ Using a Chromone-Based Fluorescence Probe

A new structurally simple fluorescent CP probe based on chromone was designed and synthesized, and its structure was fully characterized using various analytical techniques. The CP probe displays a high selectivity and sensitivity for sensing Fe3+ with a "turn-off" fluorescence response over other metal ions in a DMSO/H2O (4:1, v/v) solution. The experiment results show that the CP probe is stable over a wide pH range of 2.0-12.0. The detection limit for Fe3+ was calculated to be 0.044 μmol•L-1. The molar ratio method indicated that the binding mode between the CP probe and Fe3+ is a 1:1 complex formation. HR-MS and density functional theory (DFT) calculations were also performed to further confirm the recognition mechanism. Both fluorescence imaging experiments and the MTT assay demonstrated that the CP probe was suitable for detecting intracellular Fe3+ and no significant cytotoxicity in living cells.

Solvent-directed multiple correspondence fluorescent probe for highly selective and sensitive detection of Cu2+ and Mg2

A solvent-directed, new Schiff base multiple correspondence fluorescent probe, (E)-2-(2-hydroxybenzylidene) hydrazine-1-carboxamid (L), was synthesized for selective sensing of Cu2+ and Mg2+ ions. L showed excellent selectivity and high sensitivity toward Cu2+ in "turn off" mode with a detection limit of 40.5 nM in 10 mM, pH = 7.0 PBS buffer. Contrary to that, when acetonitrile was used as the solvent, L exhibited highly selective and sensitive fluorescence sensing ability for Mg2+ in "turn on" mode with a detection limit of 9.5 nM. L can coordinate to Cu2+ and Mg2+ in a 1:1 molar ratio, respectively, evidenced by Job's plot analysis. Their binding modes were investigated by NMR, IR and XPS spectroscopies. Moreover, the satisfied results were obtained when L was used to detect Cu2+ and Mg2+ in real water samples.

A novel polyhedral oligomeric silsesquioxane nanohybrid fluorescent sensor designed based on an osmotic mechanism for specific detection and intelligent scavenging of magnesium ions

BACKGROUND

Mg2+ has long been recognized as one of the most vital cations due to its diverse physiological and pathological roles, making it indispensable in both biomedical and biological research. Organic fluorescent sensors are commonly employed for Mg2+ detection, but they often lack high selectivity and exhibit poor hydrophilicity, limiting their biomedical applications.

RESULTS

Herein, we introduced a novel organic-inorganic hybrid fluorescence sensor, PFHBS, constructed on the POSS nanoplatforms. The efficient connection between PEGylated POSS and the small molecule sensor FHBS through Click chemistry enhances the selectivity and reduces interference, making this chemical sensor ideal for the accurate detection of Mg2+. Furthermore, the incorporation of POSS amplifies the ligand field effect of FHBS, making it more conducive to Mg2+ capture. The modification of PEG chains enhances the sensor's amphiphilicity, facilitating efficient cell penetration and effective Mg2+ detection at the biological level.

SIGNIFICANCE

Finally, relying on spontaneous permeation, coupled with its strong ligand field effect and excellent cell permeability, the chemosensor demonstrates the capability to intelligently remove excess Mg2+ from the body. It has been successfully applied to mitigate renal overload resulting from acute Mg2+ poisoning.

Schiff Base Compounds as Fluorescent Probes for the Highly Sensitive and Selective Detection of Al3+ Ions

Two new Schiff base fluorescent probes (L and S) were designed for selectively detecting Al3+ ions in aqueous medium. Structural characterization of the purely synthesized compounds was acquired by IR, 1H NMR and 13C NMR. Moreover, their photochromic and fluorescent behaviors have been investigated systematically by UV–Vis absorption and fluorescence spectra. The two probes have both high selectivity and sensitivity toward Al3+ ions in aqueous medium. The 2:1 stoichiometry between the Al3+ and probes was verified by Job’s plot. Moreover, the limits of detection (LOD) for Al3+ by L and S were 1.98 × 10−8 and 4.79 × 10−8 mol/L, respectively, which was much lower than most previously reported probes. The possible recognition mechanism was that the metal ions would complex with Schiff base probes because of the prevalence of the species optimal for complex formation, inhibiting the structural isomerization of conjugated double bonds (-C=N-), inhibiting the proton transfer process in the excited state of the molecules and resulting in changes of its color and fluorescence behavior. Furthermore, the probes will have potential applications for selectively, detecting Al3+ ions in the environmental system with high accuracy and providing a new strategy for the design and synthesis of multi-functional sensors.

A New «off-on» Fluorescence Zinc Ion Sensors Based on Iodo- and Bromosubstituted Dipyrromethenes

Monoiodo- and dibromsubstituted dipyrromethenes HL¹ - HL³ were described as a highly sensitive and selective «Off-On» fluorescent chemosensor for Zn²⁺ based on the chelation-enhanced fluorescence (CHEF) effect. Сoordination reactions of HL¹ - HL³ with Zn²⁺ cations are accompanied by a significant (124 to 215-fold) increase in fluorescence intensity against the background of other metal ions in the binary propanol-1/cyclohexane mixture (1:30). The fluorometric detection limit of Zn²⁺ ions using HL¹ - HL³ sensors is from 3.0∙10^-8 to 3.3·10^-9 mol/L. The presence of Na⁺, K⁺, Ca²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Co²⁺, Pb²⁺ cations does not interfere with the detection of Zn²⁺. Complexation reactions are accompanied by a visual change in the color of the solution from yellow-orange to pink-raspberry so that the HL¹ - HL³ ligands can also be used as a «naked-eye» indicators of the presence of Zn²⁺ ions.

A novel peptide-based fluorescent probe for sensitive detection of zinc (II) and its applicability in live cell imaging

In this work, we report SPSS synthesis of a new peptide-based fluorescent probe (L) capable of detecting Zn²⁺ with little interference in 100% aqueous solutions at physiological pH. Furthermore, L showed excellent sensitivity, with a detection limit of 26.77 nM. The 2:1 binding ratio between L and Zn²⁺ was determined using fluorometric titration, Job's plot and ESI-MS analyses. The "off-on-off" type fluorescence change of L was demonstrated by alternately adding Zn²⁺ and EDTA based on a formation-separation process of the complex, indicating that L could serve as a reversible probe. Moreover, MTT studies demonstrated that L has low biotoxicity, and could be successfully used for detection of Zn²⁺ and EDTA in live cells.

Synthesis and fluorescence properties of two dendritic molecules based on naphthalimide and triphenylamine

Artificial light-harvesting systems have attracted great interest in biological photosynthesis and photo-voltaic devices areas due to their unique structures, easy purification, low-cost, and convenient processing abilities. Here, two dendritic molecules based on triphenylamine and naphthalimide have been designed and synthesized, their structures were confirmed by ¹ H NMR, ESI-MS, and high resolution mass spectrometry. In these molecules, triphenylamine units perform as the electron donor moiety, and naphthalimide units perform as the electron acceptor. The obvious quenched fluorescence intensity and considerably shortened lifetime of the dendritic molecules combined with the molecular frontier orbital energy levels proved that the dendritic molecules not only are good candidates as hole-transporting materials but also are two excellent photo-induced electron transfer materials. Therefore, it is believed that these dendritic molecules have potential application value in photo-voltaic devices.

A Schiff base-based fluorescent probe for the quick detection of ClO− ions

A new Schiff base 2-hydroxy-5-[(2,7-dihydroxy-1-naphthyl)methylideneamino]benzoic acid (HNMB) has been designed and synthesized. HNMB was characterized by Fourier-transform infrared spectroscopy (FTIR), electrospray ionization mass spectrometry (ESI–MS), nuclear magnetic resonance spectrometry (NMR), and single crystal X-ray diffraction. Fluorescence spectra show that HNMB could be used as a “turn-on” probe to detect ClO− ions from other anions in DMSO/H2O (v/v = 1:1) with a fast response time of 10 s and a low detection limit of 3.6 × 10−7 mol/L. Moreover, the probe could work in a wide pH range of 4–10. The detection mechanism was studied by ESI–MS.

A benzyl carbazate-based fluorescent chemosensor for detecting Zn2+: Application to zebrafish

A benzyl carbazate-based fluorescent chemosensor BCS was designed and synthesized for detection of Zn²⁺ in aqueous media. BCS displayed a notable fluorescence increase with Zn²⁺. Detection limit (1.12 μM) of BCS for zinc ion was much lower than the standard of World Health Organization. BCS was used to analyze the amounts of Zn²⁺ in water samples. Importantly, sensor BCS could be used to image Zn²⁺ in zebrafish, and a fluorescent test strip of sensor BCS for detecting Zn²⁺ could be useful for practical purpose. Sensing process of Zn²⁺ by BCS was demonstrated by DFT calculations, based on an effect of chelation-enhanced fluorescence.

A selective “turn-on” sensor for recognizing In3+ and Zn2+ in respective systems based on imidazo[2,1-b]thiazole

An imidazo[2,1-b]thiazole-based compound (X) was designed and synthesized as an “off–on–off” sensor for the multiple recognition of In³⁺ and Zn²⁺ in different systems.

A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III)

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al³⁺ with colorimetric and fluorescent responses. Upon addition of Al³⁺ to compound MCIH2 solution, compound MCIH2 could respond to Al³⁺ with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye. Furthermore, a remarkable fluorescence emission enhancement with an "OFF-ON" signal by over 700-fold was triggered, but other various metal ions had no such significant effects on the fluorescence emission. In addition, the detection limit of compound MCIH2 for recognizing Al³⁺ was evaluated to be as low as 1 × 10^-7 M level, which was sufficiently low for sensing Al³⁺ widely distributed in various environmental and biological systems.

A new fluorescent-colorimetric chemosensor based on a Schiff base for detecting Cr3+, Cu2+, Fe3+ and Al3+ ions

A new Schiff base derivative fluorescence-colorimetric chemosensor 2-hydroxy-5-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H₃L), has been designed and synthesized. H₃L displayed high selectivity and sensitivity for detecting Cr³⁺, Cu²⁺, Fe³⁺ and Al³⁺ ions in DMF/H₂O (v/v = 1/1) solution. When Cr³⁺, Cu²⁺ or Fe³⁺ ions were added, the solution of H₃L in DMF/H₂O exhibited different color changes. While with the addition of Fe³⁺ or Al³⁺ ions, the solution of H₃L in DMF/H₂O displayed different fluorescence responses. The bonding modes and bonding ratios of H₃L and metal ions were explored by the Job's plot, ¹H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The detection limits of H₃L with Cr³⁺, Cu²⁺, Fe³⁺and Al³⁺ ions were 3.37 × 10^-7 M, 4.65 × 10^-7 M, 3.58 × 10^-7 M and 4.89 × 10^-7 M, respectively.

A fluorogenic probe based on chelation–hydrolysis-enhancement mechanism for visualizing Zn2+ in Parkinson's disease models

Developing efficient methods for real-time detection of Zn²⁺ level in biological systems is highly relevant to improve our understanding of the role of Zn²⁺ in the progression of Parkinson's disease (PD).