Quinoline-based Fluorescent Probe Research Articles

A novel quinoline-based fluorescent probe for real-time monitoring of Cys in glioma.

Cysteine (Cys), a small-molecule biothiol, has recently been identified as a novel Glioblastoma (GBM) biomarker. The highly selective real-time monitoring and fluorescence imaging of Cys levels in vivo is of great significance for the early diagnosis and treatment of GBM. In this work, we reported a highly selective Cys fluorescent probe ZS-C1, based on quinoline according to the mechanism of the conjugate addition cyclization reaction. The Limit of Detection (LOD) of probe ZS-C1 was 1.97 μM, λex = 380 nm; λem = 531 nm. In vitro experiments showed that ZS-C1 could be distinguished from Hcy and GSH significantly, and the fluorescence quantum yield was reduced by 30 times. Further, biological imaging and 3D tumor sphere penetration assay showed that the ZS-C1 could monitor both exogenous and endogenous Cys in the living U87MG cells, and the fluorescence of probe ZS-C1 diffusely distributed inside the U87MG three-dimensional solid cell spheroid (up to 60 μM deep into the solid tumors). This work provided a potential tool for further investigations of Cys in biological samples and critical information for early diagnosis of glioma and guidance for clinical surgery.

"Turn-On" Quinoline-Based Fluorescent Probe for Selective Imaging of Tau Aggregates in Alzheimer's Disease: Rational Design, Synthesis, and Molecular Docking.

Tau aggregation is believed to have a strong association with the level of cognitive deficits in Alzheimer's disease (AD). Thus, optical brain imaging of tau aggregates has recently gained substantial attention as a promising tool for the early diagnosis of AD. However, selective imaging of tau aggregates is a major challenge due to sharing similar β-sheet structures with homologous Aβ fibrils. Herein, four quinoline-based fluorescent probes (Q-tau) were judiciously designed using the donor-acceptor architecture for selective imaging of tau aggregates. In particular, probe Q-tau 4 exhibited a strong intramolecular charge transfer and favorable photophysical profile, such as a large Stokes' shift and fluorescence emission wavelength of 630 nm in the presence of tau aggregates. The probe also displayed a "turn-on" fluorescence behavior toward tau fibrils with a 3.5-fold selectivity versus Aβ fibrils. In addition, Q-tau 4 exhibited nanomolar binding affinity to tau aggregates (Kd = 16.6 nM), which was 1.4 times higher than that for Aβ fibrils. The mechanism of "turn-on" fluorescence was proposed to be an environment-sensitive molecular rotor-like response. Moreover, ex vivo labeling of human AD brain sections demonstrated favorable colocalization of Q-tau 4 and the phosphorylated tau antibody, while comparable limited staining was observed with Aβ fibrils. Molecular docking was conducted to obtain insights into the tau-binding mode of the probe. Collectively, Q-tau 4 has successfully been used as a tau-specific fluorescent imaging agent with lower background interference.

Quinoline-based fluorescent probe for the detection and monitoring of hypochlorous acid in a rheumatoid arthritis model.

The development of effective bioanalytical methods for the visualization of hypochlorous acid (HOCl) in situ in rheumatoid arthritis (RA) directly contributes to better understanding the roles of HOCl in this disease. In this work, a new quinoline-based fluorescence probe (HQ) has been developed for the detection and visualization of a HOCl-mediated inflammatory response in a RA model. HQ possesses a donor–π–acceptor (D–π–A) structure that was designed by conjugating p-hydroxybenzaldehyde (electron donor) and 1-ethyl-4-methylquinolinium iodide (electron acceptor) through a C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C double bond. In the presence of HOCl, oxidation of phenol to benzoquinone led to the red-shift (93 nm) of the adsorption and intense quenching of the fluorescence emission. The proposed response reaction mechanism was verified by high performance liquid chromatography (HPLC) and high-resolution mass spectroscopy (HRMS) titration analysis. The remarkable color changes of the HQ solution from pale yellow to pink enabled the application of HQ-stained chromatography plates for the “naked-eye” detection of HOCl in real-world water samples. HQ featured high selectivity and sensitivity (6.5 nM), fast response time (<25 s) to HOCl, reliability at different pH (3.0 to 11.5) and low cytotoxicity. HQ's application in biological systems was then demonstrated by the monitoring of HOCl-mediated treatment response to RA. This work thus provided a new tool for the detection and imaging of HOCl in inflammatory disorders.

Dual sensing of methionine and aspartic acid in aqueous medium by a quinoline-based fluorescent probe.

A quinoline-based Schiff base sensor, 6-methyl-2-oxo-1,2-dihydro-quinoline-3-carboxaldehyde-4(N)-phenylsemicarbazone (6MPS), has been developed for selective sensing of methionine and aspartic acid in aqueous medium through "on-off-on" type selective detection of copper ion. Fluorescence imaging of 6MPS, 6MPSC, 6MPSCN, 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp has been successfully demonstrated, in which the sensing probes 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp displayed bright green fluorescence in both in vitro and in vivo live cells.

Novel quinoline-based fluorescent bioimaging probe, KSNP117, for sentinel lymph node mapping.

Fluorescent imaging agents with biocompatibility and high sensitivity are urgently required for the accurate detection of sentinel lymph nodes (SLNs). Herein, we report the design of a novel quinoline-based fluorescent probe, designated KSNP117, which can be applied as a biomedical imaging agent in the sensitive and quantitative detection of SLNs. KSNP117 exerted no adverse effects on the proliferation of ovary and immune cells and also showed excellent serum stability with photo-brightening effects. In vivo fluorescent imaging revealed the accumulation of KSNP117 in the SLNs of nude mice within 10 min post injection, without in vivo toxicity, which was consistent with the findings of ex vivo imaging. These results support the potential of KSNP117 as a promising lymphatic tracer for biomedical imaging applications.

A fast-response turn-on quinoline-based fluorescent probe for selective and sensitive detection of zinc (II) and its application

A readily available Schiff base quinoline derivative, quinoline-2-carboxaldehyde (pyridine-2-carbonyl)-hydrazine (QCPCH), has been synthesized via a one-step condensation reaction. It is used as a turn-on fluorescent probe for detecting Zn2+ with high selectivity, sensitivity, and rapid response time of less than 3 s. In addition, the probe QCPCH shows a low detection limit of 72 nM and a large linear detection range (0–180 μM). The mechanism of probe QCPCH for sensing Zn2+ is proposed to be based on the combined effects of chelation-induced enhanced fluorescence (CHEF) and inhibiting photoinduced electron transfer (PET); this is further demonstrated by the Job's plot analysis, Benesi-Hildebrand study, FT-IR spectrum, and 1H NMR titration. Furthermore, the QCPCH is successfully applied to determine Zn2+ in real water samples, and is made into test strips for fast, convenient, quantitative and qualitative detection of Zn2+.

A quinoline-based fluorescent probe for selective detection and real-time monitoring of copper ions - a differential colorimetric approach.

A quinoline moiety was used as a building block for designing a probe for the selective detection of copper ions in a partially aqueous medium. We have developed a molecular sensing system which gives insight into the complex physiological and redox aspects of labile copper. The probe provides a colorimetric approach for distinguishing cuprous and cupric ions along with their simultaneous discrimination from other metal ions in the visible range of the spectrum. The chemosensor showed a remarkable fluorescence enhancement along with a significant bathochromic shift of about 35 nm. The detection limit of the probe was found to be 1.03 μM which is optimally favorable to be applied in real-time monitoring. Fabrication of paper strips with the probe was done to detect the presence of cuprous ions in the real sample. The value of the binding constant (1.37 × 104 M-1) suggests stable complex formation between the metal ion and the sensing probe. The photoluminescence and structural aspects of the chemosensor were characterized by using fluorescence, absorption, ESI-MS, and 1H NMR spectroscopy. Furthermore, the cytotoxic nature and bioimaging properties of the probe were interpreted in vitro on RAW 264.7 macrophage cell lines and peripheral blood mononuclear cells (PBMCs) respectively.

A quinoline-based ratiometric fluorescent probe for discriminative detection of Zn2+ and Cd2+ with different binding modes, and its Zn2+ complex for relay sensing of pyrophosphate and adenosine triphosphate

A new and simple quinoline-based fluorescent probe for discriminative sensing of Zn2+ and Cd2+ has been synthesized by inserting an amide group into the 8-aminoquinoline fluorophore and a propargylamine chelating site. This easily-available chemosensor displayed selective and distinct ratiometric fluorescence responses to Zn2+ in almost totally water solution through its amide tautomer binding form, and to Cd2+ in CH3CN aqueous medium through its imidic acid tautomer binding form, respectively. Moreover, the in situ prepared probe 1–Zn2+ complex could act as a relay fluorescent sensor selectively toward pyrophosphate (PPi) and adenosine 5′-triphosphate (ATP) anions via further complexation. Thus, with good specificity, low detection limits and fast response time, a highly efficient fluorescence platform for simultaneous multi-analyte detection has been developed by using the uncomplicated single molecule. Finally, this multi-functional probe was applied successfully for analysis of all the target ions in the tap water sample and on test paper strips, and bioimaging of Zn2+ in mung bean sprouts with low phytotoxicity.

Quinoline-based ratiometric fluorescent probe for detection of physiological pH changes in aqueous solution and living cells

Herein, a novel quinoline-based fluorescent probe DQPH has been developed for ratiometric detection of subtle pH fluctuation in biosystem. Upon altering the pH from 4.50 to 9.00, the emission spectra exhibit a large hypsochromic shift (57 nm) and the ratio of fluorescence intensity (F531 nm/F588 nm) changes from 0.30 to 1.36 with an ideal pKa value of 7.18 and a linear pH variation range of 6.35–8.00. The ratiometric response is attributed to the protonation-activable resonance charge transfer (PARCT) process, which has been proved by 1H NMR and NOESY experiment. This probe displayed good solubility, low cytotoxicity, anti-interference capability and reversible pH sensing. Furthermore, DQPH was successfully applied for monitoring pH changes in living cells.

A novel “off-on” type fluorescent chemosensor for detection of Zn2+ and its zinc complex for “on-off” fluorescent sensing of sulfide in aqueous solution, in vitro and in vivo

We reported a new quinoline-based fluorescent probe 1 for Zn2+ and S2−. 1 showed a highly selective fluorescence enhancement toward Zn2+ over other metal ions including Cd2+, and the resulting 1-Zn2+ complex could detect only S2− among the various anions. The detection limits (0.09 μM and 0.88 μM) for Zn2+ and S2− were much lower than recommended values (76 μM for Zn2+ and 14.8 μM for S2−) by WHO. Their recognition mechanisms were explained by Job plots, UV–vis titrations, 1H NMR titrations, ESI-mass, and theoretical calculations. Moreover, compound 1 with the great photostability and low biotoxicity showed sequentially off-on-off fluorescent bio-imaging of Zn2+ and S2− in both HeLa cells and live zebrafish larvae.

Quinoline-based highly selective and sensitive fluorescent probe specific for Cd2+ detection in mixed aqueous media

Quinoline-based fluorescent probe as a recognition unit was designed and synthesized in this study. The probe R1 displayed excellent selectivity and sensitivity for cadmium ions (Cd2+) over a wide range of metal ions in acetonitrile-water (MeCN-H2O) mixed solution. In order to better understand the recognition mechanism between probe and Cd2+, the density functional theory calculations were performed. Finally, the colorimetric experiment result was observed and conveniently monitored by the naked eye, and a visual detection limit of 4×10−6molL−1 was achieved. These experimental results indicated the promising potential of the probe to detect Cd2+ in biological system. Furthermore, the probe R1 was successfully used for the highly sensitive detection of Cd2+ in living cells.

A new fluorescent probe based on quinoline for detection of Al3+ and Fe3+ with “off–on–off” response in aqueous solution

A new quinoline-based fluorescent probe has been designed and synthesized. It showed highly selective relay recognition of Al3+ and Fe3+via a fluorescence “off–on–off” mechanism by central metal displacement.

A new quinoline-based fluorescent probe for Cd(2+) and Hg(2+) with an opposite response in a 100% aqueous environment and live cell imaging.

A new quinoline-based fluorescent probe was synthesized and characterized. Probe showed opposite fluorescence responses toward Cd(2+) (turn-on) and Hg(2+) (turn-off) in a 100% aqueous environment. X-ray crystallography analysis and TD-DFT calculations showed the different mechanisms of CHEF-based for -Cd(2+) and PET-based for -Hg(2+) caused by different binding modes and different electronic transfer patterns. The detection limits for the analysis of Cd(2+) and Hg(2+) ions were found to be 3.9 × 10(-8) M and 9.8 × 10(-7) M, respectively. Its in vivo sensitivities to Cd(2+) and Hg(2+) were demonstrated in the EC9706 cell line with the use of a laser scanning fluorescence microscope.

Highly Selective Quinoline-Based Fluorescent Probe for Copper(II) Ions

Highly Selective Quinoline-Based Fluorescent Probe for Copper(II) Ions

A simple quinoline-based fluorescent “turn on” probe with high selectivity for Ag+ in aqueous media

A simple quinoline-based fluorescent probe L for Ag+ has been developed. Probe L shows fluorescence enhancement (turn on) response towards Ag+ with high selectivity in aqueous media (methanol–water, v/v=3:7, pH 7.2, 20mM Tris–HCl) based on a combinational effect of the inhibition of intermolecular photoinduced proton transfer and chelation-enhanced fluorescence. And an obvious fluorescent color change could be observed by naked eyes under the light of 365nm. The binding mode between L and Ag+ has been found to be 1:1 based on the fluorescence/absorption titration, ESI-MS and further confirmed by X-ray crystallography.

Design of quinoline-based fluorescent probe for the ratiometric detection of cadmium in aqueous media

Abstract A new fluorescent probe, DQCd2, based on 4-piperidinoquinoline has been synthesized as a fluorescent probe for Cd 2+ . It can ratiometrically respond to Cd 2+ in PBS buffer by a remarkable emission intensity enhancement (88-fold) and wavelength shift (70 nm).

A simple fluorescent probe for Cd2+ in aqueous solution with high selectivity and sensitivity

A simple quinoline-based fluorescent probe, PBQ, which contained a tweezer-like receptor, was successfully developed via one-step synthesis. PBQ exhibited a 40-fold fluorescence enhancement response to Cd(2+) in aqueous solution. PBQ was found to have excellent selectivity for Cd(2+) over many other metal ions (Ba(2+), Mn(2+), Hg(2+), Ni(2+), Ca(2+), Cu(2+), Co(2+), Pb(2+), Mg(2+), Zn(2+), Fe(2+), Fe(3+), Cr(3+), Ag(+), Li(+), Na(+), K(+)). Significantly, its fluorescence intensity was enhanced in a linear fashion with the concentration of Cd(2+). Thus PBQ can be potentially used for the quantification of Cd(2+). Moreover, a series of model compounds were rationally designed and synthesized in order to explore the binding mode of PBQ with Cd(2+).

Quinoline-based fluorescent probe for ratiometric detection of hydrogen peroxide in aqueous solution

A novel quinoline-based fluorescent probe for detecting H 2 O 2 is described. In aqueous solution, the probe exhibits fluorescence emission at 542 nm originating from the monocationic species. The reaction between the probe and H 2 O 2 causes quenching of the emission at 542 nm and simultaneously yields a significant hypsochromic shift of the emission maximum to 480 nm due to the H 2 O 2 -triggered boronate cleavage process. Thus, a single-excitation, dual-emission ratiometric measurement with a large blue shift in emission (Δ λ = 62 nm) and remarkable changes in the ratio ( F 480 nm / F 542 nm ) of the emission intensity ( R / R 0 up to 8.3-fold) can be established. Moreover, the probe can also afford high selectivity for detecting H 2 O 2 over other biological reactive oxygen species. ► A new fluorescent probe for H 2 O 2 is based on boronate deprotection mechanism. ► The probe can detect H 2 O 2 through turn-on and ratiometric fluorescence signal output. ► This probe can avoid the influence from other reactive oxygen species and pH changes.