Selective Fluorescence Imaging Research Articles

High selective fluorescence imaging of cesium distribution in Arabidopsis using a bis(trihydroxyphenyl)-appended fluorescent probe with a turn-on system

The bis(trihydroxyphenyl)-appended ligand 1 was found to display dramatically enhanced fluorescence upon the addition of Cs+, but not with any other metal ions.

A multifunctional probe with aggregation-induced emission characteristics for selective fluorescence imaging and photodynamic killing of bacteria over mammalian cells.

A multifunctional probe aggregation-induced emission-Zinc(II)-dipicolylamine (AIE-ZnDPA) is developed for selective targeting, fluorescence imaging, and photodynamic killing of both Gram-positive and Gram-negative bacteria over mammalian cells. The probe has significant advantages in simple probe design, enhanced fluorescence upon bacteria binding, excellent photostability, and broad-spectrum antibacterial activity with almost no harm to mammalian cells.

Spatially Selective Holographic Photoactivation and Functional Fluorescence Imaging in Freely Behaving Mice with a Fiberscope

Correlating patterned neuronal activity to defined animal behaviors is a core goal in neuroscience. Optogenetics is one large step toward achieving this goal, yet optical methods to control neural activity in behaving rodents have so far been limited to perturbing all light-sensitive neurons in a large volume. Here we demonstrate an all-optical method for precise spatial control and recording of neuronal activity in anesthetized and awake freely behaving mice. Photoactivation patterns targeted to multiple neuronal somata, produced with computer-generated holography, were transmitted to the mouse brain using a micro-objective-coupled fiber bundle. Fluorescence imaging through the same device, via epifluorescence, structured illumination, or scanless multipoint confocal microscopy, allowed imaging of neurons and recording of neuronal activity. The fiberscope was tested in mice coexpressing ChR2-tdTomato and GCaMP5-G in cerebellar interneurons, delivering near-cellular resolution photoactivation in freely behaving mice.

ROS-Responsive Activatable Photosensitizing Agent for Imaging and Photodynamic Therapy of Activated Macrophages

The optical properties of macrophage-targeted theranostic nanoparticles (MacTNP) prepared from a Chlorin e6 (Ce6)-hyaluronic acid (HA) conjugate can be activated by reactive oxygen species (ROS) in macrophage cells. MacTNP are nonfluorescent and nonphototoxic in their native state. However, when treated with ROS, especially peroxynitrite, they become highly fluorescent and phototoxic. In vitro cell studies show that MacTNP emit near-infrared (NIR) fluorescence inside activated macrophages. The NIR fluorescence is quenched in the extracellular environment. MacTNP are nontoxic in macrophages up to a Ce6 concentration of 10 μM in the absence of light. However, MacTNP become phototoxic upon illumination in a light dose-dependent manner. In particular, significantly higher phototoxic effect is observed in the activated macrophage cells compared to human dermal fibroblasts and non-activated macrophages. The ROS-responsive MacTNP, with their high target-to-background ratio, may have a significant potential in selective NIR fluorescence imaging and in subsequent photodynamic therapy of atherosclerosis with minimum side effects.

Multifunctional Nanoplatforms for Targeted Multidrug-Resistant-Bacteria Theranostic Applications

The emergence of multidrug-resistant-bacteria (MDRB) infection poses a major burden to modern healthcare. Early detection in the bloodstream and a new strategy development for MDRB infection treatment without antibiotics are clinically significant to save millions of lives every year. To tackle the MDRB challenge, the current manuscript reports the design of "multifunctional nanoplatforms" consisting of a magnetic core-plasmonic shell nanoparticle, a methylene blue-bound aptamer, and an MDRB Salmonella DT104 specific antibody. The reported "multifunctional nanoplatform" is capable of targeted separation from a blood sample and sensing and multimodal therapeutic killing of MDRB. Experimental data using an MDRB-infected whole-blood sample show that nanoplatforms can be used for selective magnetic separation and fluorescence imaging. In vitro light-triggered photodestruction of MDRB, using combined photodynamic and photothermal treatment, shows that the multimodal treatment regime can enhance MDRB killing significantly. We discussed the possible mechanisms on combined synergistic therapy for killing MDRB. The "multifunctional nanoplatform" reported in this manuscript has great potential for the imaging and combined therapy of MDRB in clinical settings.

Highly Selective Recognition and Fluorescence Imaging of Adenosine Polyphosphates in Aqueous Solution

The design and synthesis of chemosensors for the recognition of a certain nucleoside polyphosphate among various structurally similar nucleoside polyphosphates remain a fundamental challenge. Herein, we report the new fluorescent chemosensor [Zn2L](ClO4)4 (1; L = (3,6,10,13,17,20,24,27-octaaza-1,15(2,6)-dipyridina-8,22(9,10)-dianthracenacyclooctacosaphane), which can selectively recognize adenosine polyphosphates (ATP and ADP) among various nucleoside polyphosphates, with a large fluorescence enhancement (Fmax/F0 = 70 and 80 for ATP and ADP, respectively) and strong binding affinity (K = 3.1 × 10(11) M(-1) for [Zn2HL(H-1ATP)2](-), 2.8 × 10(11) M(-1) for [Zn2L(H-1ATP)2](2-), and 1.5 × 10(13) M(-1) for [Zn2L(H-1ADP)2](2-)) in aqueous solution at physiological pH 7.40. The structure of [Zn2L](P2O7) (2) was investigated, which shows that μ2-pyrophosphate anions alternately link [Zn2L](4+) cations to generate a 1D coordination polymer. The results of (31)P NMR studies and DFT calculations reveal that the two Zn(II) ions in 1 can interact with ATP/ADP anions through coordination interactions between Zn(II) and the polyphosphate groups, and two anthracene moieties in 1 can interact with adenine groups from two ATP or ADP anions through stacking interactions to form a sandwichlike structure. These multiple recognition interactions between 1 and ATP/ADP enhance the affinity and selectivity of 1 toward ATP/ADP. Due to its highly selective and sensitive ability to detect adenosine polyphosphates, 1 was successfully applied to fluorescence imaging for ATP and ADP in living cells, demonstrating the potential utility of 1 as a fluorescent chemosensor for detecting ATP and ADP.

NIR Photoresponsive Crosslinked Upconverting Nanocarriers Toward Selective Intracellular Drug Release

An NIR-responsive mesoporous silica coated upconverting nanoparticle (UCNP) conjugate is developed for controllable drug delivery and fluorescence imaging in living cells. In this work, antitumor drug doxorubicin (Dox) molecules are encapsulated within cross-linked photocaged mesoporous silica coated UCNPs. Upon 980 nm light irradiation, Dox could be selectively released through the photocleavage of theo-nitrobenzyl (NB) caged linker by the converted UV emission from UCNPs. This NIR light-responsive nanoparticle conjugate demonstrates high efficiency for the controlled release of the drug in cancer cells. Upon functionalization of the nanocarrier with folic acid (FA), this photocaged FA-conjugated silica-UCNP nanocarrier will also allow targeted intracellular drug delivery and selective fluorescence imaging towards the cell lines with high level expression of folate receptor (FR).

Nontoxic concentrations of PEGylated graphene nanoribbons for selective cancer cell imaging and photothermal therapy

Reduced graphene oxide nanoribbons functionalized by amphiphilic polyethylene glycol (rGONR–PEG) were applied to attach arginine-glycine-aspartic acid (RGD)-based peptide and cyanine dye 3 (cy3) for targeting ανβ3 integrin receptors on human glioblastoma cell line U87MG and its selective fluorescence imaging, respectively. The rGONR–PEG suspension with a concentration of 100 μg mL−1 showed ∼14 and 2.4-fold higher near infrared (NIR) absorption at 808 nm than GONR (with dimensions of ∼80 nm × 1 μm) and rGO–PEG sheets (with lateral dimensions of ∼2 μm), respectively. The rGONR–PEG–cy3–RGD exhibited highly efficient NIR photothermal therapy performance (concentrations ≥1.0 μg mL−1 resulted in ≥97% cell destruction in vitro under 7.5 W cm−2 NIR irradiation for 8 min). However, the rGONR–PEG exhibited concentration-dependent cyto- and geno-toxicity, so that it initiated at 1.0 μg mL−1 and presented strong effects at concentrations ≥100 μg mL−1 (resulting in >72% cell destruction and >29% DNA fragmentation after 24 h in the dark). Therefore, the concentration of 1.0 μg mL−1 (with <11% cell destruction and 7% DNA fragmentation) is the most effective concentration which can present low cyto- and especially geno-toxic effects. This work can provide insights for simultaneously efficient and biocompatible applications of nano-sized graphene in future photothermal nanotherapy.

Design of a multinuclear Zn(ii) complex as a new molecular probe for fluorescence imaging of His-tag fused proteins

A Zn(II) complex (Zn(II)-Ida) was designed as the new fluorescent probe for His-tag fused proteins. Thanks to the tight binding ability to histidine-rich sequences and bright fluorescence property of the Cy5-appended Zn(II)-Ida probes, selective and clear fluorescent imaging of the His-tag fused G-protein coupled receptors on live cell surfaces was carried out.

Visible–Near‐Infrared and Fluorescent Copper Sensors Based on Julolidine Conjugates: Selective Detection and Fluorescence Imaging in Living Cells

We present novel Schiff base ligands julolidine-carbonohydrazone 1 and julolidine-thiocarbonohydrazone 2 for selective detection of Cu(2+) in aqueous medium. The planar julolidine-based ligands can sense Cu(2+) colorimetrically with characteristic absorbance in the near-infrared (NIR, 700-1000 nm) region. Employing molecular probes 1 and 2 for detection of Cu(2+) not only allowed detection by the naked eye, but also detection of varying micromolar concentrations of Cu(2+) due to the appearance of distinct coloration. Moreover, Cu(2+) selectively quenches the fluorescence of julolidine-thiocarbonohydrazone 2 among all other metal ions, which increases the sensitivity of the probe. Furthermore, quenched fluorescence of the ligand 2 in the presence of Cu(2+) was restored by adjusting the complexation ability of the ligand. Hence, by treatment with ethylenediaminetetraacetic acid (EDTA), thus enabling reversibility and dual-check signaling, julolidine-thiocarbonohydrazone (2) can be used as a fluorescent molecular probe for the sensitive detection of Cu(2+) in biological systems. The ligands 1 and 2 can be utilized to monitor Cu(2+) in aqueous solution over a wide pH range. We have investigated the structural, electronic, and optical properties of the ligands using ab initio density functional theory (DFT) combined with time-dependent density functional theory (TDDFT) calculations. The observed absorption band in the NIR region is attributed to the formation of a charge-transfer complex between Cu(2+) and the ligand. The fluorescence-quenching behavior can be accounted for primarily due to the excited-state ligand 2 to metal (Cu(2+)) charge-transfer (LMCT) processes. Thus, experimentally observed characteristic NIR and fluorescence optical responses of the ligands upon binding to Cu(2+) are well supported by the theoretical calculations. Subsequently, we have employed julolidine-thiocarbonohydrazone 2 for reversible fluorescence sensing of intracellular Cu(2+) in cultured HEK293T cells.

A copper(ii) rhodamine complex with a tripodal ligand as a highly selective fluorescence imaging agent for nitric oxide

A copper(II) complex CuRBT with a ring-closed rhodamine-containing tripodal ligand was synthesized as a highly selective fluorescent imaging agent for nitric oxide (NO). It featured a 700-fold fluorescent enhancement toward NO from a dark-background with the detection limit of NO about 1 nM in aqueous solution and could be applied for monitoring intracellular NO.

A Highly Selective Low-Background Fluorescent Imaging Agent for Nitric Oxide

We introduce a novel sensing mechanism for nitric oxide (NO) detection with a particular easily synthesized embodiment (NO(550)), which displays a rapid and linear response to NO with a red-shifted 1500-fold turn-on signal from a dark background. Excellent selectivity was observed against other reactive oxygen/nitrogen species, pH, and various substances that interfere with existing probes. NO(550) crosses cell membranes but not nuclear membranes and is suitable for both intra- and extracellular NO quantifications. Good cytocompatibility was found during in vitro studies with two different cell lines. The high specificity, dark background, facile synthesis, and low pH dependence make NO(550) a superior probe for NO detection when used as an imaging agent.

Fluorescent Magnetic Nanoprobes for in vivo Targeted Imaging and Hyperthermia Therapy of Prostate Cancer

It has been a challenging task to develop nontoxic nanoprobes for targeted-imaging and selective therapy of prostate cancer. Herein, fluorescent superparamagnetic nanoparticles with a diameter of 50 nm were conjugated with single-chain Fv antibody against g -seminoprotein. The resultant nanoprobes showed highly selective targeting, fluorescent imaging, and magnetic resonance imaging. The cytotoxicity effects were investigated on the prostate cancer cells and solid tumors under in vitro alternating magnetic field irradiation. It was found that the as-prepared nanoprobes did not show signs of toxicity within the used maximal dosage . It was also observed that the tumors implanted in nude mice were significantly reduced in size and disappeared gradually due to thermal treatment. The lifespan of post-therapeutic mice loaded with prostate cancer was considerable prolonged. High-performance single-chain Fv antibody against g -seminoprotein-conjugated fluorescent magnetic nanoparticles may have great potential in applications such early detection and localized thermal therapy of prostate cancer.

Protein Design Provides Lead(II) Ion Biosensors for Imaging Molecular Fluxes around Red Blood Cells

Metalloprotein design and semiconductor nanoparticles have been combined to generate a reagent for selective fluorescence imaging of Pb(2+) ions in the presence red blood cells. A biosensor system based on semiconductor nanoparticles provides the photonic properties for small molecule measurement in and around red blood cells. Metalloprotein design was used to generate a Pb(2+) ion selective receptor from a protein that is structurally homologous to a protein used previously in this biosensing system. Parameters for the Pb(2+) ion binding site were derived from crystallographic structures of low molecular weight Pb(2+) ion complexes that contain a stereoactive lone pair. When the designed protein was produced and attached to ZnS-coated CdSe nanoparticles, two Pb(NO(3))(2)-associated binding events were observed (2-fold emission decrease; K(A1) = 1 x 10(9) M(-1); K(A2) = 3.5 x 10(6) M(-1)). The fluorescence response had a 100 pM Pb(NO(3))(2) detection limit, while no response was observed with Ca(2+) ions (10 mM), Zn(2+) ions (100 muM), or Cd(2+) ions (100 muM). Metal ion selectivity presumably comes from the coordination geometry selected to favor lone pair formation on Pb(2+) ions and electrostatically disfavor tetrahedral coordination. Replacement of ZnS-coated CdSe with ZnS-coated InGaP nanoparticles provided similar biosensors (100 pM limit of detection; K(A1) = 1 x 10(9) M(-1); K(A2) = 1 x 10(7) M(-1)) but with excitation/emission wavelengths longer than the major absorbance of red blood cell hemoglobin (>620 nm). The InGaP nanoparticle-based biosensors provided a 5 nM Pb(NO(3))(2) detection limit in the presence of red blood cells. The modularity of the biosensor system provides exchangeable Pb(2+) ion detection around red blood cells.

Selective fluorescent imaging of superoxide in vivo using ethidium-based probes

The putative oxidation of hydroethidine (HE) has become a widely used fluorescent assay for the detection of superoxide in cultured cells. By covalently joining HE to a hexyl triphenylphosphonium cation (Mito-HE), the HE moiety can be targeted to mitochondria. However, the specificity of HE and Mito-HE for superoxide in vivo is limited by autooxidation as well as by nonsuperoxide-dependent cellular processes that can oxidize HE probes to ethidium (Etd). Recently, superoxide was shown to react with HE to generate 2-hydroxyethidium [Zhao, H., Kalivendi, S., Zhang, H., Joseph, J., Nithipatikom, K., Vasquez-Vivar, J. & Kalyanaraman, B. (2003) Free Radic. Biol. Med. 34, 1359-1368]. However, 2-hydroxyethidium is difficult to distinguish from Etd by conventional fluorescence techniques exciting at 510 nm. While investigating the oxidation of Mito-HE by superoxide, we found that the superoxide product of both HE and Mito-HE could be selectively excited at 396 nm with minimal interference from other nonspecific oxidation products. The oxidation of Mito-HE monitored at 396 nm by antimycin-stimulated mitochondria was 30% slower than at 510 nm, indicating that superoxide production may be overestimated at 510 nm by even a traditional superoxide-stimulating mitochondrial inhibitor. The rate-limiting step for oxidation by superoxide was 4x10(6) M-1.s-1, which is proposed to involve the formation of a radical from Mito-HE. The rapid reaction with a second superoxide anion through radical-radical coupling may explain how Mito-HE and HE can compete for superoxide in vivo with intracellular superoxide dismutases. Monitoring oxidation at both 396 and 510 nm of excitation wavelengths can facilitate the more selective detection of superoxide in vivo.