A highly sensitive fluorescent probe based on simple pyrazoline for Zn2+ in living neuron cells

A Review on Pyrazolines as Colorimetric Fluorescent Chemosensors for Cu2

The Pyrazoline derivatives display promising potential as sensitive and selective chemosensors for detecting Cu2+ ions. It has undergone screening for its sensing behavior with various metals using absorption, emission spectroscopic techniques. Their unique structure incorporates both donating and accepting sites, characterized by delocalized orbitals. These derivatives exhibit notable chromogenic and fluorogenic capabilities facilitated by intramolecular charge transfer. The sensors based on pyrazoline demonstrate exceptional selectivity, low detection limits, and precise detection of metal ions, particularly Cu2+. This review offers a comprehensive summary of recent discoveries concerning as pyrazoline-based "On-Off" chemosensors. The discussion places emphasis on exploring the design and photophysical properties of these chemosensors, with the primary objective of detecting Cu2+ metal ions. The unique features of pyrazoline derivatives make them promising candidates for practical applications in environmental and biological monitoring, showcasing their potential significance in advancing sensing technologies.

Synthesis of Fluorescent Pyrazoline Sensors as Versatile Tool for Zinc ion Detection: A Mini-Review

Zinc ions are one of the 2nd most abundant mineral after iron and it is important for immune system, enzymatic catalysis, DNA synthesis, and maintaining structural integrity in humans. But, monitoring the Zn levels in human body poses more challenges. This review paper investigates (paper from 2010 to 2023) the synthesis of pyrazoline derivatives by different methods, including conventional methods and green chemistry protocol. These Pyrazoline derivatives highlighted for their potential application as chemo-sensor for Zn2+ ions recognition. Pyrazoline compounds exhibit excellent sensitivity & selectivity and emitting blue-light with high quantum yields and electroluminescence, along with a superior limit of detection. These derivatives are stable bioactive molecule, with well-known diverse biological activities. This review not only gives valuable insights into the essential role of Zinc in human physiology but also provides a practical method for accurate Zinc detection in various samples. Which holds the potential for advancements in health diagnostics and environmental monitoring. Because of their significant biological application and selectivity as sensors, researchers have much more attention to prepare green environmentally-friendly pyrazoline derivatives.

Novel pyrazoline and pyrazole "turn on" fluorescent sensors selective for Zn2+/Cd2+ at λem 480 nm and Fe3+/Fe2+ at λem 465 nm in MeCN

A small series of simple pyrazoline and pyrazole based sensors, all derived from the same chalcone precursors, were synthesised, characterised and screened for their fluorescence "turn on" properties in the presence of multiple metals. Pyrazole 8 displayed an excellent fluorescence profile with approx. 20× fold increase in λem 480 nm with Zn2+ compared to a 2.5× fold increase with Cd2+. Pyrazole 9 displayed a 30× fold increase at λem 465 nm for Fe3+ compared to Fe2+ with a Fe3+ limit of detection of 0.025 μM. The corresponding pyrazolines displayed contrasting properties with important implications for future pyrazoline and pyrazole sensor design.

Novel Bis-pyrazoline Fluorescent Probe for Cu2+ and Fe3+ Detection and Application in Cell Imaging

A fluorescent probe Y((1,1'-([1,1'-biphenyl]-4,4'-diylbis(3-(2-hydroxyphenyl)-4,5-dihydro-1H-pyrazole-5,1-diyl)) bis(ethan-1-one))) was designed and synthesized, which could be used to Cu2+ and Fe3+ sensors. Through the study of optical properties, the probe Y shows good selectivity and sensitivity to Cu2+ and Fe3+ in aqueous tetrahydrofuran solution [10.0 mM HEPES, pH 7.4, THF-H2O = 9:1(v/v)] with has excellent anti-interference performance, and its detection limits were 0.931 uΜ for Cu2+ and 0.401uΜ for Fe3+. The coordination mechanism of probe Y with Cu2+ and Fe3+ was speculated and verified at DFT level and HRNM. By Hela cytotoxicity and imaging tests, probe Y not only has good biocompatibility, but also can be used for sensing Cu2+ in cells.

Design of a Highly Selective Benzimidazole-Based Derivative for Optical and Solid-State Detection of Zinc Ion

A novel series of benzimidazole-based molecules mimicking biological receptors, which exhibit selective coordination with zinc ions, were designed and synthesized. The photochromic behavior of these derivatives with various metal ions suggests a selective interaction of one of the receptors 2-(pyridin-2-yl)-4,7-di(thiophen-2-yl)-3H-benzo[d]imidazole (2c) with zinc ion. The lower limit of detection by photoluminescence quenching was determined to be 16 nM. The mechanism of selective complexation was elucidated by ¹H nuclear magnetic resonance titrations and dynamic light scattering analysis. The stoichiometry of the formation of the Zn(2c)₂ complex was evaluated by single-crystal X-ray diffraction and mass spectral techniques and calculated to be 2:1 (L:M). A change in the electronic energy levels on the sensor analyte interaction was observed by both ultraviolet photoelectron spectroscopy analysis and by density functional theory calculations, suggesting an electroactive semiconductor behavior. A symmetric Schottky structured sensor device was fabricated using the receptor 2c as the active sensing layer. A distinct change in current-voltage characteristics between the receptor and the complex suggests that the fabricated device could be used as a solid-state sensor for detecting zinc ion.

Recent Progress in Fluorescent Probes For Metal Ion Detection

All forms of life have absolute request for metal elements, because metal elements are instrumental in various fundamental processes. Fluorescent probes have been widely used due to their ease of operation, good selectivity, high spatial and temporal resolution, and high sensitivity. In this paper, the research progress of various metal ion (Fe³⁺,Fe²⁺,Cu²⁺,Zn²⁺,Hg²⁺,Pb²⁺,Cd²⁺) fluorescent probes in recent years has been reviewed, and the fluorescence probes prepared with different structures and materials in different environments are introduced. It is of great significance to improve the sensing performance on metal ions. This research has a wide prospect in the application fields of fluorescence sensing, quantitative analysis, biomedicine and so on. This paper discusses about the development and applications of metal fluorescent probes in future.

Pyrazoline Hybrids as Promising Anticancer Agents: An Up-to-Date Overview

Pyrazolines are five-membered heterocycles possessing two adjacent nitrogens. They have attracted significant attention from organic and medicinal chemists due to their potent biological activities and the numerous possibilities for structural diversification. In the last decade, they have been intensively studied as targets for potential anticancer therapeutics, producing a steady yearly rise in the number of published research articles. Many pyrazoline derivatives have shown remarkable cytotoxic activities in the form of heterocyclic or non-heterocyclic based hybrids, such as with coumarins, triazoles, and steroids. The enormous amount of related literature in the last 5 years prompted us to collect all these published data from screening against cancer cell lines, or protein targets like EGFR and structure activity relationship studies. Therefore, in the present review, a comprehensive account of the compounds containing the pyrazoline nucleus will be provided. The chemical groups and the structural modifications responsible for the activity will be highlighted. Moreover, emphasis will be given on recent examples from the literature and on the work of research groups that have played a key role in the development of this field.

Recent progress in chemosensors based on pyrazole derivatives

Colorimetric and fluorescent probes based on small organic molecules have become important tools in modern biology because they provide dynamic information concerning the localization and quantity of the molecules and ions of interest without the need for genetic engineering of the sample. In the past five years, these probes for ions and molecules have attracted great attention because of their biological, environmental and industrial significance combined with the simplicity and high sensitivity of absorption and fluorescence techniques. Moreover, pyrazole derivatives display a number of remarkable photophysical properties and wide synthetic versatility superior to those of other broadly used scaffolds. This review provides an overview of the recent (2016-2020) findings on chemosensors containing pyrazole derivatives (pyrazoles, pyrazolines and fused pyrazoles). The discussion focuses on the design and physicochemical properties of chemosensors in order to realize their full potential for practical applications in environmental and biological monitoring (sensing of metal ions, anions, explosives, and biomolecules). We also present our conclusions and outlook for the future.

A pyrazoline-based fluorescent chemosensor for Al3+ ion detection and live cell imaging

The pyrene appended pyrazoline compounds were designed and synthesized for selective detection of Al³⁺ ion.

Crystal structure of 4-bromo-2-(1H-pyrazol-3-yl)phenol, C9H7BrN2O

C9H7BrN2O, triclinic, C2/c (no. 15), a = 16.255(3) Å, b = 4.4119(9) Å, c = 25.923(5) Å, β = 107.99(3)°, V = 1768.2(7) Å3, Z = 8, R gt(F) = 0.0450, wR ref(F 2) = 0.0960, T = 150 K.

A new pyrazoline-based probe of quenched fluorescent reversible recognition for Cu2+ and its application in cells

A new pyrazoline-based probe D was designed and synthesized, which can be used as a highly sensitive, selective and reversible recognizing fluorescent to detect Cu²⁺. The recognition properties of this compound was investigated by UV-vis absorption and fluorescence spectrophotometry. The results showed that the probe D forms a 1:1 complex with Cu²⁺ and displayed a linear fluorescence response to Cu²⁺ with a detection limit of 1.94×10^-7M. In addition, the probe have a good biocompatibility in living cells.

Unveiling a versatile heterocycle: pyrazoline – a review

The design and synthesis of novel fluorescent heterocyclic dyes is a “hotspot” research area, due to their favourable photophysical and electronic properties, which could allow huge advances in the fields of physics, chemistry and biology.

Imine-functionalized thioether Zn(ii) turn-on fluorescent sensor and its selective sequential logic operations with H2PO4−, DFT computation and live cell imaging

Thioether Schiff base (H₂L), a nontoxic Zn²⁺-sensor (LOD, 0.050 μM) has shown selective ON–OFF emission following INHIBIT logic circuit with H₂PO₄⁻and useful agent for the identification of Zn²⁺and H₂PO₄⁻in intracellular fluid in living cells.

Synthesis of novel boron chelate complexes and proposed mechanism of new rearrangement

We synthesized novel boron chelate complexes by the reaction of pyrazoline derivatives and boron trifluoride diethyl etherate followed by a new rearrangement. The structures of the compounds were characterized by IR, NMR and HRMS, especially, a typical compound 3c was confirmed by X-ray single crystal analysis. We proposed a mechanism of the rearrangement. Moreover, the absorption and fluorescence spectroscopy of these compounds were measured.

Novel pyrazoline-based selective fluorescent probe for the detection of hydrazine

A novel pyrazoline-based fluorescent probe, 2-[4-(3,5-diphenyl-4,5-dihydro-pyrazol-1-yl)-benzylidene]-malononitrile, with a simple structure and low detection limit (6.16×10(-6)M) for the detection of hydrazine is designed and synthesized. The probe responds selectively to hydrazine over other molecules with marked fluorescence enhancement. The probe can detect hydrazine effectively at pH 5.0-9.0 with a special emission wavelength at 520nm. Moreover, the probe can be used to detect hydrazine from variety of natural source water.

Novel pyrazoline-based fluorescent probe for detecting thiols and its application in cells

A new compound, N-(4-(1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl)phenyl)-acrylamide (probe L), was designed and synthesized as a highly sensitive and selective fluorescent probe for recognizing and detecting thiol from other amino acids. On being mixed with thiol in buffered DMSO:HEPES=1:1 solution at pH 7.4, the probe exhibited the blue emission at 474 nm. This probe is very sensitive and displayed a linear fluorescence off-on response to thiol. The fluorescence emission of the probe is pH independent in the physiological pH range. Living cell imaging of HeLa cells confirmed its cell permeability and its ability to selectively detect thiol in cells. The structure of the probe was characterized by IR, NMR and HRMS spectroscopy analysis.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

Biologically targeted probes for Zn2+: a diversity oriented modular "click-SNAr-click" approach†Electronic supplementary information (ESI) available: Full experimental details including characterisation of all novel compounds can be found in the ESI. See DOI: 10.1039/c4sc01249f

We describe a one-pot strategy for the high yielding, operationally simple synthesis of fluorescent probes for Zn2+ that bear biological targeting groups and exemplify the utility of our method through the preparation of a small library of sensors. Investigation of the fluorescence behaviour of our library revealed that although all behaved as expected in MeCN, under biologically relevant conditions in HEPES buffer, a plasma membrane targeting sensor displayed a dramatic switch on response to excess Zn2+ as a result of aggregation phenomena. Excitingly, in cellulo studies in mouse pancreatic islets demonstrated that this readily available sensor was indeed localised to the exterior of the plasma membrane and clearly responded to the Zn2+ co-released when the pancreatic beta cells were stimulated to release insulin. Conversely, sensors that target intracellular compartments were unaffected. These results demonstrate that this sensor has the potential to allow the real time study of insulin release from living cells and exemplifies the utility of our simple synthetic approach.

A new turn-on fluorescence probe for Zn(2+) in aqueous solution and imaging application in living cells

We designed and synthesized a new pyrazoline-based turn-on fluorescence probe for Zn(2+) by the reaction of chalcone and thiosemicarbazide. The structure of the probe was characterized by IR, NMR and HRMS spectroscopy. The probe (L) exhibits high selectivity and sensitivity for detecting Zn(2+) in buffered EtOH/HEPES solution (EtOH/HEPES=1/1, pH 7.2) with 80-fold fluorescence enhancement, which is superior to previous reports. Job's plot analysis revealed 1:1 stoichiometry between probe L and Zn(2+) ions. The association constant estimated by the Benesi-Hildebrand method and the detection limit were 3.92×10(3)M(-1) and 5.2×10(-7)M, respectively. A proposed binding mode was confirmed by (1)H NMR titration experiments and density functional theory (DFT) calculations. The probe is cell-permeable and stable at the physiological pH range in biological systems. Because of its fast response to Zn(2+), the probe can monitor Zn(2+) in living cells. Moreover, the selective binding of L and Zn(2+) was reversible with the addition of EDTA in buffered EtOH/HEPES solution and Zn(2+) could be imaged in SH-SY5Y neuron cells.

Discovery of a novel fluorescent HSP90 inhibitor and its anti-lung cancer effect

A novel fluorescent HSP90 inhibitor with strong growth inhibitory effects on lung cancer cells was developed.

A new Schiff base fluorescent probe for imaging Cu2+ in living cells

A novel probe based on ferrocenyl-1,3,4-thiadiazol-containing Schiff base was synthesized by the reaction of 5-ferrocenyl-1,3,4-thiadiazol-2-amine and 4-(diethylamino)salicylaldehyde, and characterized by IR, NMR, HRMS and X-ray analysis. UV-vis spectral and fluorescence property of the probe were investigated. The probe can be used to colorimetric sensitive and selective fluorescent recognition of Cu(2+) in buffer solution. Moreover, the probe can detect Cu(2+) by electrochemical method. Additionally, the Schiff base was successfully used as a selective and sensitive fluorescent probe for monitoring Cu(2+) ions in living cells.

A new thiophenyl pyrazoline fluorescent probe for Cu2+ in aqueous solution and imaging in live cell

A new thiophenyl pyrazoline probe for Cu(2+) in aqueous solution was synthesized and characterized by IR, NMR, HRMS and X-ray analysis. The probe displays remarkably high selectivity and sensitivity for Cu(2+) with a detection limit of 1.919 × 10(-7) M in aqueous solution (EtOH:HEPES = 1:1, v/v, 0.02 M, pH = 7.2). In addition, the probe is further successfully used to image Cu(2+) in living cells and the probe possesses good reversibility.

8-Aminoquinoline-based ratiometric zinc probe: unexpected binding mode and its application in living cells

PMQA, an 8-aminoquinoline-based ratiometric fluorescent sensor, demonstrates the Zn(2+)-induced red-shift of emission (85nm), and was successfully applied to image zinc in living cells. Compared to 2:1 stoichiometry in PMQA-Zn(2+), PMQA-Cu(2+) shows 1:1 composition. Both nitrogen atoms from the aminoquinoline are missing in binding of zinc, while they are critically involved in Cu(2+) chelation. The structure difference between PMQA-Zn(2+) and PMQA-Cu(2+) might shed light in designing novel zinc probes without suffering from copper interference.