A Pyridoindole-Based Multifunctional Bioprobe: pH-Induced Fluorescence Switching and Specific Targeting of Lipid Droplets (original) (raw)
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European Journal of Organic Chemistry, 2018
Lipid droplets (LDs) have been recognized as highly dynamic cellular organelles involved in important biological functions for the survival of organisms such as supplying food or energy. Nevertheless, lipid storage must be tightly controlled, since both its excess and the inability to store lipids can be detrimental to the organism, resulting in metabolic diseases or multifaceted systemic problems. Visualization and monitoring the concentration of LDs is essential to understand these processes. Commercially available LD dyes such as nile red and BODIPY offer several advantageous characteristics but can be limiting in multicolor imaging since most ready-made fluorescent reporter constructs fluoresce in the green to red region of the visible spectrum. Nile red emits between green and red, and BODIPY can be photoconvertable from green to red fluorescent, limiting its ability to utilize it for time lapse imaging of living cells. Here, we report the design and synthesis, the photophysical characterization, and biological results with two easily prepared series of new blue fluorescing dyes as markers for LDs. Confocal fluorescence microscopy results show an interesting correlation between the chemical structure of these fluorescent probes and the specific staining pattern. The pyrazole-based structure (6c) is specific for LDs, whereas the pyrrole-based structure (5d) resulted in prominent dyeing of the membranous cell organelles.
Non-fused Phospholes as Fluorescent Probes for Imaging of Lipid Droplets in Living Cells
Frontiers in chemistry, 2017
Molecular tools for fluorescent imaging of specific compartments in cells are essential for understanding the function and activity of cells. Here, we report the synthesis of a series of pyridyl- and thienyl-substituted phospholes and the evaluation of these dyes for fluorescent imaging of cells. The thienyl-substituted phospholes proved to be successful for staining of cultured normal and malignant cells due to their fluorescent properties and low toxicity. Co-staining experiments demonstrated that these probes target lipid droplets, which are, lipid-storage organelles found in the cytosol of nearly all cell types. Our findings confirm that thienyl-substituted phospholes can be utilized as fluorescent tools for vital staining of cells, and we foresee that these fluorescent dyes might be used in studies to unravel the roles that lipid droplets play in cellular physiology and in diseases.
Dyes and Pigments
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Bioconjugate chemistry, 2017
Altered lipid metabolism and extensive lipid storage in cells have been associated with various medical disorders, including cancer. The development of fluorescent probes that specifically accumulate in lipid deposits is therefore of great interest in order to study pathological processes that are linked to dysregulated lipogenesis. In the present study, we present a small fluorescent benzothiadiazole dye that specifically stains lipid droplets in living and fixated cells. The photophysical characterization of the probe revealed strong solvatochromic behavior, large Stokes shifts, and high fluorescent quantum yields in hydrophobic solvents. In addition, the fluorophore exhibits a nontoxic profile and a high signal-to-noise ratio in cells (i.e., lipid droplets vs cytosol), which make it an excellent candidate for studying lipid biology using confocal fluorescent microscopy.
A judicious structural modification of molecular building units imparts significant variation in the evolution dynamics of supramolecular self-assembled architectures and their functional properties. The incorporation of alkyl chains into the rigid and π-conjugated molecular backbone not only directs the self-assembly but also enhances the hydrophobicity of the probe, facilitating specific interactions with hydrophobic organelle like lipid droplets (LDs). Such a fluorescent molecular probe is ideally suited for elucidation of complex self-assembly processes and to decipher the intracellular dynamics of LDs. Invoking the concept, the main skeleton of 1,4-bis(1H-phenanthro[9,10-d]imidazol-2-yl)benzene abbreviated as BPIB, was functionalized with a varying number of octyl chains to obtain BPIB1 and BPIB2. The alkyl chains were crucial to circumvent the π-π stacking leading to the strong fluorescence in aggregates and solid-state. Contrary to BPIB and BPIB2, intermolecular interactions-...
Imidazo[1,5-a]pyridine-Based Fluorescent Probes: A Photophysical Investigation in Liposome Models
Molecules
Imidazo[1,5-a]pyridine is a stable scaffold, widely used for the development of emissive compounds in many application fields (e.g., optoelectronics, coordination chemistry, sensors, chemical biology). Their compact shape along with remarkable photophysical properties make them suitable candidates as cell membrane probes. The study of the membrane dynamics, hydration, and fluidity is of importance to monitor the cellular health and to explore crucial biochemical pathways. In this context, five imidazo[1,5-a]pyridine-based fluorophores were synthesized according to a one-pot cyclization between an aromatic ketone and benzaldehyde in the presence of ammonium acetate and acetic acid. The photophysical features of prepared compounds were investigated in several organic solvents and probes 2–4 exhibited the greatest solvatochromic behavior, resulting in a higher suitability as membrane probes. Their interaction with liposomes as artificial membrane model was tested showing a successful i...
Light-Up Lipid Droplets Dynamic Behaviors Using a Red-Emitting Fluorogenic Probe
Analytical Chemistry, 2020
Intracellular lipid metabolism occurs in lipid droplets (LDs), which is critical to the survival of cells. Imaging LDs is an intuitive way to understand their physiology in live cells. However, this is limited by the availability of specific probes that can properly visualize LDs in vivo. Here, an LDs-specific red-emitting probe is proposed to address this need, which is not merely with an ultrahigh signal-to-noise (S/N) ratio and a large Stokes shift (up to 214 nm) but also with superior resistance to photobleaching. The probe has been successfully applied to real-time tracking of intracellular LDs behaviors, including fusion, migration, and lipophagy processes. We deem that the proposed probe here offers a new possibility for deeper understanding of LDs-associated behaviors, elucidation of their roles and mechanisms in cellular metabolism, and determination of the transition between adaptive lipid storage and lipotoxicity as well.
Journal of Photochemistry and Photobiology A-chemistry, 2009
Fluorescence properties of the antitumoral methyl 3-(benzo [b]thien-2-yl)-benzothieno[3,2-b]pyrrole-2carboxylate (BTP) were studied in solution and in lipid bilayers of dipalmitoyl phosphatidylcholine (DPPC), dioleoyl phosphatidylethanolamine (DOPE) and egg yolk phosphatidylcholine (Egg-PC). BTP presents good fluorescence quantum yields in all solvents studied (0.20 ≤˚F ≤ 0.32) and a bathochromic shift in polar solvents. The results indicate an ICT character of the excited state, with an estimated dipole moment of e = 7.38 D.
Fluorescence imaging of pyrene-labeled lipids in living cells
Biochimica et Biophysica Acta ( …, 2000
Microscopic imaging of fluorescent lipid derivatives is a powerful tool to study membrane organization and lipid trafficking but it is complicated by cellular autofluorescence background and photobleaching of the fluorophore as well as by the difficulty to selectively image membranes stacked on top of each other. Here we describe protocols that strongly alleviate such problems when pyrene-labeled lipids are being used. First, photobleaching of these lipids is virtually eliminated when oxygen is depleted from the medium by using a gentle and simple enzymatic method. Second, an image practically free of cellular autofluorescence contribution can be obtained simply by subtracting from the pyrene image the background image obtained at a slightly different excitation wavelength. This type of background subtraction more properly accounts for the typically uneven distribution of cellular background fluorescence than other, commonly used methods. Third, it is possible to selectively image the pyrene lipids in the plasma membrane by using plasma membrane-specific quencher trinitrophenyl lysophosphatidylethanolamine and image subtraction. Importantly, either the outer or the inner leaflet can be selectively imaged by labeling the cells with pyrene phosphatidylcholine or phosphatidylserine, respectively. These protocols should be of considerable help when studying organization of the plasma membrane or intracellular lipid trafficking.