Selective Fluorescence Imaging Research Articles

COX-2 targeting indomethacin conjugated fluorescent probe

The COX-2 targeting indomethacin-conjugated fluorescent probe IQ-1 was synthesized newly for selective fluorescence imaging of cancer cells over normal cells. IQ-1 caused stronger fluorescencc imaging of COX-2 overexpressing cancer cells (OVCAR3, HepG2 and Hela cells) than of normal cell lines (RAW 246.7 and fibroblast cells). LPS, an oxidative stress agent, treated inflamed cell lines inducing high COX-2 levels also revealed an enhanced fluorescence. In inhibitory studies, a markedly reducd fluorescence intensity was observed in cancer cells co-treated with an inhibitor, such as indomethacin and aceclofenac. Therefore, IQ-1 can be used as a selective bioimaging agent for cancer cells over normal cells, and could be developed for efficient diagnosis and therapeutic monitoring in precision medicine.

Spectrally selective fluorescence imaging of Chlorobaculum tepidum reaction centers conjugated to chelator-modified silver nanowires

A polyhistidine tag (His-tag) present on Chlorobaculum tepidum reaction centers (RCs) was used to immobilize photosynthetic complexes on a silver nanowire (AgNW) modified with nickel-chelating nitrilo-triacetic acid (Ni-NTA). The optical properties of conjugated nanostructures were studied using wide-field and confocal fluorescence microscopy. Plasmonic enhancement of RCs conjugated to AgNWs was observed as their fluorescence intensity dependence on the excitation wavelength does not follow the excitation spectrum of RC complexes in solution. The strongest effect of plasmonic interactions on the emission intensity of RCs coincides with the absorption spectrum of AgNWs and is observed for excitation into the carotenoid absorption. From the absence of fluorescence decay shortening, we attribute the emission enhancement to increase of absorption in RC complexes.

A Strategy for Specific Fluorescence Imaging of Monoamine Oxidase A in Living Cells

AbstractMonoamine oxidase (MAO) has two isoforms, MAO‐A and MAO‐B, which show different functions, and thus selective fluorescence imaging is important for biological studies. Currently, however, specific detection of MAO‐A remains a great challenge. Herein, we report a new strategy for specific imaging of MAO‐A through the design of fluorogenic probes combining the characteristic structure of an inhibitor of the target enzyme along with propylamine as a recognition moiety. The high specificity of our representative probe is demonstrated by imaging MAO‐A in different live cells such as SH‐SY5Y (high levels of MAO‐A) and HepG2 (high levels of MAO‐B), and further validated by western blot analyses. The superior specificity of the probe may enable the accurate detection of MAO‐A in complex biosystems. Importantly, the use of the characteristic structure of an inhibitor, as demonstrated in this work, may serve as a general strategy to design specific recognition moieties for fluorogenic probes for enzymes.

A Strategy for Specific Fluorescence Imaging of Monoamine Oxidase A in Living Cells.

Monoamine oxidase (MAO) has two isoforms, MAO-A and MAO-B, which show different functions, and thus selective fluorescence imaging is important for biological studies. Currently, however, specific detection of MAO-A remains a great challenge. Herein, we report a new strategy for specific imaging of MAO-A through the design of fluorogenic probes combining the characteristic structure of an inhibitor of the target enzyme along with propylamine as a recognition moiety. The high specificity of our representative probe is demonstrated by imaging MAO-A in different live cells such as SH-SY5Y (high levels of MAO-A) and HepG2 (high levels of MAO-B), and further validated by western blot analyses. The superior specificity of the probe may enable the accurate detection of MAO-A in complex biosystems. Importantly, the use of the characteristic structure of an inhibitor, as demonstrated in this work, may serve as a general strategy to design specific recognition moieties for fluorogenic probes for enzymes.

Ruthenium complexes/polypeptide self-assembled nanoparticles for identification of bacterial infection and targeted antibacterial research.

Bacterial infection has been a threat to human health, and so early diagnosis and treatment of bacterial infection is an urgent problem that needs to be solved. In this work, a multifunctional theranostic selenium nanoplatform (Se@PEP-Ru NPs) with early imaging diagnosis and efficient treatment of bacterial infections was designed and constructed. First, the antibacterial peptide UBI29-41 (PEP) was linked to functionalized Selenium nanoparticles (NPs), which enhanced the stability of the antimicrobial peptide and also caused the nanocomposites to specifically target bacterial infection. Ruthenium complexes with good antibacterial activity and fluorescence properties were then coated on to their outer layers. It was worth mentioning that, when the resulting nanoprobe was injected into mice by intravenous injection it was found to be sensitive to sites of bacterial infection for selective fluorescence imaging and targeted therapy. Thus, it can be used to distinguish between bacterial infection, inflammation, and tumor-induced tissue infection with high specificity. In the further antibacterial activity experiments, Ruthenium complexes showed synergistic antimicrobial activity with Se NPs, which indicated that the antibacterial activity of Se@PEP-Ru NPs was the strongest that could promote wound healing. Thus, Se@PEP-Ru NPs appears to be a promising antimicrobial with good biocompatibility, excellent selectivity, and potent antimicrobial activity.

Front Cover: Redox Center Modification of Lapachones towards the Synthesis of Nitrogen Heterocycles as Selective Fluorescent Mitochondrial Imaging Probes (Eur. J. Org. Chem. 26/2017)

Front Cover: Redox Center Modification of Lapachones towards the Synthesis of Nitrogen Heterocycles as Selective Fluorescent Mitochondrial Imaging Probes (Eur. J. Org. Chem. 26/2017)

Redox Center Modification of Lapachones towards the Synthesis of Nitrogen Heterocycles as Selective Fluorescent Mitochondrial Imaging Probes

We describe herein a synthetic strategy for the synthesis of new fluorescent imidazole and phenazine derivatives synthesized from lapachol, a naturally occurring naphthoquinone isolated from Tabebuia species (ipê tree). The photophysical properties and computational details of these compounds have been studied, aiming at gaining a complete understanding of the potential of these derivatives as probes capable of staining mitochondria selectively. Cell imaging experiments proved the capacity of the imidazole derivatives as selective fluorescent mitochondrial imaging probes. These heterocycles present the same staining patterns as MitoTracker Red, corroborating the potential of these compounds as new mitochondria markers permeable to the cell membrane.

An excited-state intramolecular photon transfer fluorescence probe for localizable live cell imaging of cysteine

Small molecule probes suitable for selective and specific fluorescence imaging of some important but low-concentration intracellular reactive sulfur species such as cysteine (Cys) pose a challenge in chemical biology. We present a readily available, fast-response fluorescence probe CHCQ-Ac, with 2-(5′-chloro-2-hydroxyl-phenyl)-6-chloro-4(3 H)-quinazolinone (CHCQ) as the fluorophore and acrylate group as the functional moiety, that enables high-selectivity and high-sensitivity for detecting Cys in both solution and biological system. After specifically reacted with Cys, the probe undergoes a seven-membered intramolecular cyclization and released the fluorophore CHCQ with excited-state intramolecular photon transfer effect. A highly fluorescent, insoluble aggregate was then formed to facilitate high-sensitivity and high-resolution imaging. The results showed that probe CHCQ-Ac affords a remarkably large Stokes shift and can detect Cys under physiological pH condition with no interference from other analytes. Moreover, this probe was proved to have excellent chemical stability, low cytotoxicity and good cell permeability. Our design of this probe provides a novel potential tool to visualize and localize cysteine in bioimaging of live cells that would greatly help to explore various Cys-related physiological and pathological cellular processes in cell biology and diagnostics.

Aggregation‐Induced Emission for Highly Selective and Sensitive Fluorescent Biosensing and Cell Imaging

ABSTRACTFluorescent bioprobes are powerful analytical tools for studying biological activities in living systems. Fluorogens with aggregation‐induced emission (AIE) characteristics have recently emerged as a new class of fluorescent bioprobes for biosensing and cell imaging. As discovered by Tang, AIE fluorogens are nearly nonemissive in molecular states with their intermolecular rotations being not restricted whereas their fluorescence is turned on by binding with certain biomolecules, leading to highly selective turn‐on fluorescent probes for specific biomolecules and fluorescent cell imaging with a high signal‐to‐background noise ratio. By introducing the AIE characteristics into polymeric materials, AIE polymers could possess a good solubility and biocompatibility, excellent structural diversity, and ease for functionalization useful for efficient biosensing and cell imaging. Herein, we highlight a few recently published articles on small and macromolecular AIE molecules to provide a fundamental understanding of the AIE mechanism and illustrate the working principle for AIE based biosensing and cell imaging. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 653–659

Correction: Enzyme-responsive reporter molecules for selective localization and fluorescence imaging of pathogenic biofilms.

Correction for 'Enzyme-responsive reporter molecules for selective localization and fluorescence imaging of pathogenic biofilms' by Junxin Aw et al., Chem. Commun., 2017, 53, 3330-3333.

Enzyme-responsive reporter molecules for selective localization and fluorescence imaging of pathogenic biofilms.

Pathogenic bacteria and their biofilm formation are responsible for a broad spectrum of microbial infections. A novel enzyme-responsive reporter molecule (ERM-1), which can specifically recognize AmpC β-lactamase (Bla) in drug resistant bacteria, has been developed to enable the selective localization of biofilms.

MicroRNA-Responsive Drug Release System for Selective Fluorescence Imaging and Photodynamic Therapy In Vivo.

Photodynamic therapy (PDT) is a noninvasive strategy to treat diseases by light-triggered activation of a photosensitizer (PS). One aim of the recent researches on PDT is to overcome the limitation of conventional PDT by improving selective activation of PS on targeted region. Here, a microRNA (miRNA)-responsive drug activation system is developed which focuses on the role of endogenous miRNA as an internal cancer specific stimulus for initiating drug release in cancer treatment. The present system consists of PS chlorin e6 (Ce6) conjugated to peptide nucleic acid (PNA) having complementary sequence to cancer specific miRNA and dextran coated reduced graphene oxide nanocolloid (Dex-RGON). In the presence of oncogenic miR-21 in cancer cells, Ce6-PNA drug gets hybridized with miR-21, resulting in the release of Ce6-PNA from Dex-RGON and subsequent recovery of Ce6 fluorescence and activation of Ce6 as a photosensitizer under near IR irradiation. It is demonstrated that the Ce6-PNA/Dex-RGON complex shows sequence-specific fluorescence in response to miR-21 and selective cytotoxic effect for tumor growth inhibition. The present study will pave a new way for utilizing PDT in cancer treatment with tightly regulated activation of a photosensitizer by oncogenic miRNA as an internal stimulus to reduce potential risk associated with conventional PDT.

A triphenylamine as a fluorophore and maleimide as a bonding group selective turn-on fluorescent imaging probe for thiols

With the biological importance of biothiols, the development of probes for thiols has been an active research area in recent years. Here, we report a novel thiol-reactive fluorescent probe based on Michael addition reaction for selectively detecting thiols over other relevant biological species. The thiol adduct was characterized using NMR and mass spectroscopy and detection mechanism was further confirmed. This sensor with excellent selectivity for biothiols over other amino acids features a rapid signal response time, a good linearity range and a low detection limit. For the practical application of the sensor, it can be used to monitor thiol in live cells with turn-on fluorescence imaging.

Functional surface engineering of quantum dot hydrogels for selective fluorescence imaging of extracellular lactate release

Selective and sensitive detection of extracellular lactate is of fundamental significance for studying the metabolic alterations in tumor progression. Here we report the rational design and synthesis of a quantum-dot-hydrogel-based fluorescent probe for biosensing and bioimaging the extracellular lactate. By surface engineering the destabilized quantum dot sol with Nile Blue, the destabilized Nile-Blue-functionalized quantum dot sol cannot only self-assemble forming quantum dot hydrogel but also monitor lactate in the presence of nicotinamide adenine dinucleotide cofactor and lactate dehydrogenase through fluorescence resonance energy transfer. Notably, the surface engineered quantum dot hydrogel show high selectivity toward lactate over common metal ions, amino acids and other small molecules that widely coexist in biological system. Moreover, the destabilized Nile-Blue-functionalized quantum dots can encapsulate isolated cancer cells when self-assembled into a hydrogel and thus specifically detect and image the extracellular lactate metabolism. By virtue of these properties, the functionalized quantum dot hydrogel was further successfully applied to monitor the effect of metabolic agents.

Cu-Au alloy nanostructures coated with aptamers: a simple, stable and highly effective platform for in vivo cancer theranostics.

As a star material in cancer theranostics, photoresponsive gold (Au) nanostructures may still have drawbacks, such as low thermal conductivity, irradiation-induced melting effect and high cost. To solve the problem, copper (Cu) with a much higher thermal conductivity and lower cost was introduced to generate a novel Cu-Au alloy nanostructure produced by a simple, gentle and one-pot synthetic method. Having the good qualities of both Cu and Au, the irregularly-shaped Cu-Au alloy nanostructures showed several advantages over traditional Au nanorods, including a broad and intense near-infrared (NIR) absorption band from 400 to 1100 nm, an excellent heating performance under laser irradiation at different wavelengths and even a notable photostability against melting. Then, via a simple conjugation of fluorophore-labeled aptamers on the Cu-Au alloy nanostructures, active targeting and signal output were simultaneously introduced, thus constructing a theranostic platform based on fluorophore-labeled, aptamer-coated Cu-Au alloy nanostructures. By using human leukemia CCRF-CEM cancer and Cy5-labeled aptamer Sgc8c (Cy5-Sgc8c) as the model, a selective fluorescence imaging and NIR photothermal therapy was successfully realized for both in vitro cancer cells and in vivo tumor tissues. It was revealed that Cy5-Sgc8c-coated Cu-Au alloy nanostructures were not only capable of robust target recognition and stable signal output for molecular imaging in complex biological systems, but also killed target cancer cells in mice with only five minutes of 980 nm irradiation. The platform was found to be simple, stable, biocompatible and highly effective, and shows great potential as a versatile tool for cancer theranostics.

Curcumin analogues as selective fluorescence imaging probes for brown adipose tissue and monitoring browning.

Manipulation of brown adipose tissue (BAT) and browning of white adipose tissue (WAT) can be promising new approaches to counter metabolic disorder diseases in humans. Imaging probes that could consistently monitor BAT mass and browning of WAT are highly desirable. In the course of our imaging probe screening, we found that BAT could be imaged with curcumin analogues in mice. However, the poor BAT selectivity over WAT and short emissions of the lead probes promoted further lead optimization. Limited uptake mechanism studies suggested that CD36/FAT (fatty acid transporter) probably contributed to the facilitated uptake of the probes. By increasing the stereo-hindrance of the lead compound, we designed CRANAD-29 to extend the emission and increase the facilitated uptake, thus increasing its BAT selectivity. Our data demonstrated that CRANAD-29 had significantly improved selectivity for BAT over WAT, and could be used for imaging BAT mass change in a streptozotocin-induced diabetic mouse model, as well as for monitoring BAT activation under cold exposure. In addition, CRANAD-29 could be used for monitoring the browning of subcutaneous WAT (sWAT) induced by β3-adrenoceptor agonist CL-316, 243.

Photodynamic Therapy: A Multifunctional Probe with Aggregation‐Induced Emission Characteristics for Selective Fluorescence Imaging and Photodynamic Killing of Bacteria Over Mammalian Cells (Adv. Healthcare Mater. 5/2015)

Photodynamic Therapy: A Multifunctional Probe with Aggregation‐Induced Emission Characteristics for Selective Fluorescence Imaging and Photodynamic Killing of Bacteria Over Mammalian Cells (Adv. Healthcare Mater. 5/2015)

Carbon dots (C-dots) from cow manure with impressive subcellular selectivity tuned by simple chemical modification.

Improved cellular selectivity for nucleoli staining was achieved by simple chemical modification of carbon dots (C-dots) synthesized from waste carbon sources such as cow manure (or from glucose). The C-dots were characterized and functionalized (amine-passivated) with ethylenediamine, affording amide bonds that resulted in bright green fluorescence. The new modified C-dots were successfully applied as selective live-cell fluorescence imaging probes with impressive subcellular selectivity and the ability to selectively stain nucleoli in breast cancer cell lineages (MCF-7). The C-dots were also tested in four other cellular models and showed the same cellular selection in live-cell imaging experiments.

Highly selective fluorescence imaging of zinc distribution in HeLa cells and Arabidopsis using a naphthalene-based fluorescent probe

2-(N,N-Dimethylamino)naphthalene-based probe 1 was found to exhibit a dramatic enhancement in fluorescence upon addition of Zn(2+), but not with any other metal ions. Probe 1 as a chemoprobe enabled high-resolution fluorescence imaging of zinc ions in HeLa cells and Arabidopsis.

A Pilot Study of Fluorescent Imaging of Colorectal Tumors Using a γ-Glutamyl-Transpeptidase-Activatable Fluorescent Probe

Backgrounds/Aim: Colorectal laterally spreading tumors (LSTs) are sometimes difficult to visualize even with image-enhanced endoscopy. γ-Glutamyl-transpeptidase (GGT) is a cell surface-associated enzyme that is overexpressed in various types of human cancers. Furthermore, GGT expression is higher in colorectal cancer cells than in normal colorectal mucosa. γ-Glutamyl hydroxymethyl rhodamine green (gGlu-HMRG), an activatable fluorescent probe, is nonfluorescent under a neutral pH and normal cellular environment; however, it turns highly fluorescent upon reaction with GGT. We evaluated ex vivo fluorescent imaging of colorectal LSTs using this GGT-activatable fluorescent probe. Methods: Between March 2013 and March 2014, 30 endoscopically resected colorectal LSTs were prospectively included in this study. Each was analyzed by first taking a baseline image before spraying, then spraying with gGlu-HMRG onto the freshly resected specimen, and finally taking fluorescent images 15 min after spraying with a dedicated imaging machine. Results: Of the LSTs, 67% rapidly showed positive fluorescent activity. These activities were shown in adenoma (54%) and carcinoma in adenoma (76%), and in LST-granular type (80%) and LST-nongranular type (40%). Conclusion: Topically spraying gGlu-HMRG enabled rapid and selective fluorescent imaging of colorectal tumors owing to the upregulated GGT activity in cancer cells.