A selective colorimetric and fluorescent sensor for Al3+ ion and its application to cellular imaging

Investigation of Mechanochromic Luminescence of Pyrene-based Aggregation-Induced Emission Luminogens: Correlation between Molecular Packing and Luminescence Behavior

To better understand the correlation between molecular structure and optical properties such as aggregation-induced emission (AIE) and mechanochromic luminescence (MCL) emission, two new pyrene-based derivatives with substitutions at the 4- and 5-positions (1HH) and at the 4-, 5-, 9-, and 10-positions (2HH) were designed and synthesized. Cyano groups were introduced at the periphery of the synthesized compounds (1HCN, 1OCN, 1BCN, 2HCN, 2OCN, and 2BCN) to investigate the influence of these groups on the emission properties of the pyrene derivatives both in solution and in the solid state. The fluorescence emission performance of these compounds in water/acetone mixtures was simultaneously studied, revealing outstanding aggregation-induced emission properties. The typical shift in emission maxima to higher values was attributed to J-aggregate formation in the aggregate state. Careful investigation of the crystal structures demonstrated abundant and intense intermolecular interactions, such as C-H…π and C-H…N hydrogen bonds, contributing to the remarkable mechanochromic luminescence performance of these compounds. The MCL properties of all the compounds were investigated using powder X-ray diffraction, and the remarkable mechanochromic properties were attributed to J-aggregate phenomena in the solid state. These results provide valuable insights into the structure-property relationship of organic MCL materials, guiding the design of efficient organic MCL materials.

A Formyl Chromone Based Schiff Base Derivative: An Efficient Colorimetric and Fluorescence Chemosensor for the Selective Detection of Hg2+ Ions

A novel chromone-based Schiff base L was designed and synthesized by condensing an equimolar amount of 3-formyl chromone and 2,4-dinitro phenyl hydrazine. Schiff base L was developed as a potent colorimetric and fluorescent molecular probe to recognize Hg2+ ions over other competitive metal ions. In the presence of Hg2+, Schiff base L displays a naked-eye detectable color change under day and UV365 nm light. Various UV-Vis and fluorescence studies of L were performed in the absence and presence of Hg2+ to determine the sensitivity and the sensing mechanism. With high selectivity and specificity, the detection limit and association constant of L for Hg2+ were estimated at 1.87 µM and 1.234 × 107 M-1, respectively. The developed sensor L was applied to real soil samples for the detection of Hg2+.

A simple "turn-on" fluorescent sensor for reversible recognition of aluminum ion in living cell

A simple and reliable "turn-on" fluorescent sensor (E)-1-[((2-hydroxyethyl)imino) methyl] naphthalen-2-ol (HNP) has been designed, synthesized, and characterized by ¹H-NMR, ¹³C-NMR, FT-IR, and EI-MS analysis. The binding property of HNP was examined employing UV-Vis and fluorescence spectroscopy. HNP exhibited high selectivity towards Al³⁺ among other cations and anions. The fluorescence titration experiment has established binding stoichiometry of HNP with Al³⁺ is 2:1, which can be further verified by HR-MS. The detection limit of HNP is 2.9 μM, and it can be reversible five-to-seven times to detect Al³⁺ without losing much efficiency which indicates that it can be a reliable probe for Al³⁺. Additionally, HNP was successfully applied for the detection of Al³⁺ in living cells. To achieve the detection of aluminum ion across a simple, reliable, and precise method, we have investigated the reversible detection (which can reversible response to Al³⁺ for five-to-seven times) of Al³⁺ through an extremely simple (requires only one-step reaction) "turn-on" fluorescent probe which enables us to visualize and analyze Al³⁺ with low detection limit (2.9 μM) and high selectivity in living cell without interference from the high abundant small biological molecules.

A Water-Soluble Schiff Base Turn-on Fluorescent Chemosensor for the Detection of Al3+ and Zn2+ Ions at the Nanomolar Level: Application in Live-Cell Imaging

A water-soluble Schiff base, 2,3-bis((E)-(2-hydroxy-3-methoxybenzylidene)amino) propanoic acid (ODA) prepared by condensing o-vanillin and DL-2,3-diaminopropionic acid was evaluated as an efficient "turn on" fluorescent chemosensor for the selective recognition of Al³⁺ and Zn²⁺ ions in presence of several interfering metal ions (detection limit; for Al³⁺ = 1.82 nM, Zn²⁺ = 7.06 nM). The probe also shows a selective chromogenic behavior towards Al³⁺ and Zn²⁺ ions that the naked eye can view. The binding stoichiometry was determined using ¹H-NMR titration and ESI-MS spectrometry. The sensing mechanism is due to the inhibition of ESIPT and isomerization of -C=N of ODA on complexation with Al³⁺/Zn²⁺. The intramolecular hydrogen bonding energy and the critical bond energy in ODA-Al³⁺/Zn²⁺ were calculated using QTAIM analysis. The Thin Layer Chromatography (TLC) plates and strip papers loaded with ODA were used to test the practical applications for sensing Al³⁺ and Zn²⁺ ions. Moreover, the probe has been used for live-cell imaging to detect Al³⁺ and Zn²⁺ ions in hepatoma C3A and human glioblastoma U87 cells.

Multi-site probe for selective turn-on fluorescent detection of Al(III) in aqueous solution: synthesis, cation binding, mode of coordination, logic gate and cell imaging

An easy to make organic probe (hereafter called as R) possessing multiple ligating sites have been synthesized and characterized using spectral techniques. The probe exhibits selective and sensitive turn-on fluorescence response with Al(III) in aqueous dimethylformamide (DMF) (1:1 v/v) solution. Fluorescence titration experiment shows that the probe binds with Al(III) with a 1:1 stoichiometry and a binding constant of 6.6 × 10⁴ M^-1.The mode of coordination of R with Al(III) has been established suing ²⁷Al and ¹H NMR studies and the results suggest formation of an octahedral complex been them. The suggested point of attachment of R with Al(III) corroborates well with Density Functional Theory (DFT) optimized structure and Mulliken charges computed. Chelation-enhanced fluorescence (CHEF) is proposed as the mechanism of enhancement of fluorescence upon addition of Al(III) to R. The probe detects Al(III) in aqueous solution with a detection limit of 0.2 μM, which is much lower than the permissible limit of Al(III) set by the World Health Organization (WHO).The probe works in a wide pH range (4-11) and thus makes it a suitable candidate for environmental and biological applications. The fluorescence signals of R were used to construct an INHIBIT molecular logic gate. The confocal fluorescence microscope experiments show that R could be employed as a fluorescent probe for detecting Al(III) in living cells.

A New “Turn-On” Fluorescence Probe for Al3+ Detection and Application Exploring in Living Cell and Real Samples

An excess of Al3+ will lead to biological disorders and even many diseases. Therefore, detecting the levels of Al3+ in the human body has drawn great attention for health monitoring. The fluorescence method has been broadly applied because of high sensitivity, real-time detection, and intracellular imaging. In this work, a new probe with “turn-on” fluorescence based on Schiff base derivative, 3,6-imine-triphenylamine-(9-ethyl) carbazole (ITEC), has been successfully synthesized and studied. The high selectivity and sensitivity of ITEC to Al3+ were verified by fluorescence spectra and the detection limit was 2.19 nmol/L. A 1:2 stoichiometry of ITEC-Al3+ was obtained by the 1H NMR spectra and Job’s plot. Furthermore, ITEC was successfully applied to the detection of Al3+ with different concentrations in living HeLa cells. The analog experiments about nature contamination of Al3+ in cells and real samples were finished.

A new Al3+ selective fluorescent turn-on sensor based on hydrazide-naphthalic anhydride conjugate and its application in live cells imaging

In this communication, we have developed an optical chemosensor 2-amino N-(6-bromo-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)benzamide (NAPH) for selective detection of Al³⁺ by reacting 4-bromo-1,8-naphthalic anhydride with 2-aminobenzohydrazide. In (DMSO:H₂O, 1:1, v/v) medium, the selective and specific nature of NAPH towards Al³⁺ was observed by the quenching along with a blue-shift in the absorption of NAPH at 465 nm that resulted in the distinct colour change from light brown to colourless. The selective complexation that occurred between NAPH and Al³⁺ was investigated by ¹H NMR and DFT methods. Under similar conditions, the weakly fluorescent receptor NAPH showed a distinct fluorescence enhancement at 555 nm in the presence of Al³⁺ among the other tested metal ions and anions. The NAPH·Al³⁺ complex formation is reversible upon addition of strong chelating agent EDTA. The receptor NAPH can be applied to detect Al³⁺ down to 2.9 μM without any interference from other tested metal ions. In addition, the receptor NAPH was successfully applied to detect Al³⁺ in live HeLa cells.

A rhodamine-based fluorescent chemosensor for Al3+: is it possible to control the metal ion selectivity of a rhodamine-6G based chemosensor?

A rhodamine derivative 3′,6′-bis(ethylamino)-2-(2-(2-hydroxy-5-methylbenzylideneamino)ethyl)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one has been found to be highly selective and sensitive chemosensor for Al³⁺ ion.

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.

A Spectral Probe for Detection of Aluminum (III) Ions Using Surface Functionalized Gold Nanoparticles

A simple green route has been developed for the synthesis of casein peptide functionalized gold nanoparticles (AuNPs), in which casein peptide acts as a reducing as well as the stabilizing agent. In this report, AuNPs have been characterized on the basis of spectroscopic and microscopic results; which showed selective and sensitive response toward Al3+ in aqueous media, and Al3+ induces aggregation of AuNPs. The sensing study performed for Al3+ revealed that the color change from red to blue was due to a red-shift in the surface plasmon resonance (SPR) band and the formation of aggregated species of AuNPs. The calibration curve determines the detection limit (LOD) for Al3+ about 20 ppb (0.067 μM) is presented using both decrease and increase in absorbance at 530 and 700 nm, respectively. This value is considerably lower than the higher limit allowed for Al3+ in drinking water by the world health organization (WHO) (7.41 μM), representing enough sensitivity to protect water quality. The intensity of the red-shifted band increases with linear pattern upon the interaction with different concentrations of Al3+, thus the possibility of producing unstable AuNPs aggregates. The method is successfully used for the detection of Al3+ in water samples collected from various sources, human urine and ionic drink. The actual response time required for AuNPs is about 1 min, this probe also have several advantages, such as ease of synthesis, functionalization and its use, high sensitivity, and enabling on-site monitoring.

A novel colorimetric and turn-on fluorescent chemosensor for iron(III) ion detection and its application to cellular imaging

A novel rhodamine-based dual probe Rh-2 for trivalent ferric ions (Fe(3+)) was successfully designed and synthesized, which exhibited a highly sensitive and selective recognition towards Fe(3+) with an enhanced fluorescence emission in methanol-water media (v/v=7/3, pH=7.2). The probe Rh-2 could be applied to the determination of Fe(3+) with a linear range covering from 3.0×10(-7) to 1.4×10(-5)M and a detection limit of 1.24×10(-8)M. Meanwhile, the binding ratio of Rh-2 and Fe(3+) was found to be 1:1. Most importantly, the fluorescence and color signal changes of the Rh-2 solution were specific to Fe(3+) over other commonly coexistent metal ions. Moreover, the probe Rh-2 has been used to image Fe(3+) in living cells with satisfying results.

A new and highly selective turn-on fluorescent sensor with fast response time for the monitoring of cadmium ions in cosmetic, and health product samples

Cadmium (Cd) which is an extremely toxic could be found in many products like plastics, fossil fuel combustion, cosmetics, water resources, and wastewaters. It is capable of causing serious environmental and health problems such as lung, prostate, renal cancers and the other disorders. So, the development of a sensor to continually monitor cadmium is considerably demanding. Tetrakis(4-nitrophenyl)porphyrin, T(4-NO2-P)P, was synthesized and used as a new and highly selective fluorescent probe for monitoring cadmium ions in the "turn-on" mode. There was a linear relationship between fluorescence intensity and the concentration of Cd(II) in the range of 1.0×10(-6) to 1.0×10(-5)molL(-1) with a detection limit of 0.276μM. To examine the most important parameters involved and their interactions in the sensor optimization procedure, a four-factor central composite design (CCD) combined with response surface modeling (RSM) was implemented. The practical applicability of the developed sensor was investigated using real cosmetic, and personal care samples.

A review of mechanisms for fluorescent ‘‘turn-on’’ probes to detect Al3+ ions

The adverse effect of Al³⁺ ions on human health as well as the environment makes it desirable to develop sensitive and specific techniques for the detection of Al³⁺ ions.