Imaging-Guided Delivery of a Hydrophilic Drug to Eukaryotic Cells Based on Its Hydrophobic Ion Pairing with Poly(hexamethylene guanidine) in a Maleated Chitosan Carrier

Imaging-guided delivery is developed for hydrophobic drugs, and to a much lesser extent, hydrophilic ones. In this work we have designed a novel strategy for real-time monitoring of hydrophilic drug delivery. Traditionally, the drug and the dye are covalently attached to a nanocarrier or are electrostatically adsorbed. Recently, we found an efficient way to bind the drug by ion-paring with an appropriate counter-ion to form the aggregate that embeds a hydrophobic dye with a considerable fluorescence enhancement. We synthesized a series of carbocyanine dyes of hydrophobicity sufficient for solubilization in hydrophobic ion pairs, which restores their emission in the near-infrared (NIR) region upon the formation of the ternary aggregates. To avoid using toxic surfactants, we applied an amphiphilic polymer-oligomer poly(hexamethylene guanidine) (PHMG) as a counter-ion. Сeftriaxone was used as a model hydrophilic drug ensuring the highest fluorescent signal. The so-formed drug–counter-ion–dye aggregates were encapsulated into a cross-linked maleated chitosan carrier. Confocal laser scanning microscopy (CLSM) studies have demonstrated internalization of the encapsulated model drug by breast adenocarcinoma cells at 40 min after treatment. These results suggest the potential application of hydrophobic ion pairs containing an NIR dye in imaging-guided delivery of hydrophilic compounds.

A Simple Small Molecule with Synergistic Passive and Active Dual-Targeting Effects for Imaging-Guided Photothermal Cancer Therapy

Photothermal therapy allows spatiotemporal control of the treatment effect only at the site of the disease and provides promising opportunities for imaging-guided precision therapy. However, the development of photothermal transduction agents (PTAs) for tumor-specific accumulation and precision imaging, avoiding toxicity to the surrounding healthy tissue, is still challenging. Herein, a cyclooxygenase-2-specific small-organic-molecule-based PTA (Cy7-TCF-IMC) is developed, which can self-assemble into nanosaucers having unique photothermal and photoacoustic properties. Specifically, the self-assembling nature of Cy7-TCF-IMC affords preferential accumulation in tumors arising from synergistic passive enhanced permeability and retention effects and active targeting for precision theranostics. Antitumor therapy results show that these Cy7-TCF-IMC nanosaucers are highly photoacoustic imaging-guided PTAs for tumor ablation. These findings suggest the self-assembled Cy7-TCF-IMC nanosaucer represents a new paradigm as a single-component supramolecular medicine that can synergistically optimize passive and active targeting, thereby improving the therapeutic index of cancer and future clinical outcomes.

Structure-Based Design of a Selective Class I Histone Deacetylase (HDAC) Near-Infrared (NIR) Probe for Epigenetic Regulation Detection in Triple-Negative Breast Cancer (TNBC)

Abnormally high levels of class I histone deacetylases (HDACs) are associated with triple-negative breast cancer (TNBC) proliferation, malignant transformation, and poor prognosis of patients. Herein, we report a near-infrared imaging probe for TNBC detection via visualizing class I HDACs. Conjugating Cy5.5 to a cyclic depsipeptide inhibitor, we obtained the probe (20-Cy5.5) that retained desirable class I HDAC affinity and selectivity. Then, this probe could visualize epigenetic changes by class I HDACs in TNBC MDA-MB-231 cells and in xenograft tumor models in real time. Treatment with suberoylanilide hydroxamic acid (SAHA) significantly reduced the uptake of the probe in tumors, suggesting its potential use in evaluation of therapeutic responses of HDACi-mediated therapy. Moreover, 20-Cy5.5 could detect class I HDAC expression in TNBC lung metastasis. This novel NIR probe that achieves tumor class I HDAC imaging not only leads to a better understanding of epigenetic regulation in tumors but also has great potential for improving the TNBC diagnosis and treatment.

Explorations into the Effect of meso-Substituents in Tricarbocyanine Dyes: A Path to Diverse Biomolecular Probes and Materials

Polymethine cyanine dyes have been widely recognized as promising chemical tools for a range of life science and biomedical applications, such as fluorescent staining of DNA and proteins in gel electrophoresis, fluorescence guided surgery, or as ratiometric probes for probing biochemical pathways. The photophysical properties of such dyes can be tuned through the synthetic modification of the conjugated backbone, for example, by altering aromatic cores or by varying the length of the conjugated polymethine chain. Alternative routes to shaping the absorption, emission, and photostability of dyes of this family are centered around the chemical modifications on the polymethine chain. This Minireview aims to discuss strategies for the introduction of substituents in the meso-position, their effect on the photophysical properties of these dyes and some structure-activity correlations which could help overcome common limitations in the state of the art in the synthesis.

A near-infrared fluorescent probe based on a hemicyanine dye with an oxazolidine switch for mitochondrial pH detection

A near-infrared fluorescent probe (AH+) has been prepared by incorporating an oxazolidine switch into a near-infrared hemicyanine dye. The probe shows fast and sensitive responses to pH from an oxazolidine switch to the hemicyanine dye upon pH decreases from 10.0 to 5.0. The probe shows good photostability, low cytotoxicity, and reversible fluorescence responses to pH changes with a pKa value of 7.6. It has been successfully used to determine pH changes in mitochondria.

Fluorous Soluble Cyanine Dyes for Visualizing Perfluorocarbons in Living Systems

The bioorthogonal nature of perfluorocarbons provides a unique platform for introducing dynamic nano- and microdroplets into cells and organisms. To monitor the localization and deformation of the droplets, fluorous soluble fluorophores that are compatible with standard fluorescent protein markers and applicable to cells, tissues, and small organisms are necessary. Here, we introduce fluorous cyanine dyes that represent the most red-shifted fluorous soluble fluorophores to date. We study the effect of covalently appended fluorous tags on the cyanine scaffold and evaluate the changes in photophysical properties imparted by the fluorous phase. Ultimately, we showcase the utility of the fluorous soluble pentamethine cyanine dye for tracking the localization of perfluorocarbon nanoemulsions in macrophage cells and for measurements of mechanical forces in multicellular spheroids and zebrafish embryonic tissues. These studies demonstrate that the red-shifted cyanine dyes offer spectral flexibility in multiplexed imaging experiments and enhanced precision in force measurements.

Sterically Shielded Heptamethine Cyanine Dyes for Bioconjugation and High Performance Near-Infrared Fluorescence Imaging

The near-infrared window of fluorescent heptamethine cyanine dyes greatly facilitates biological imaging because there is deep penetration of the light and negligible background fluorescence. However, dye instability, aggregation, and poor pharmacokinetics are current drawbacks that limit performance and the scope of possible applications. All these limitations are simultaneously overcome with a new molecular design strategy that produces a charge balanced and sterically shielded fluorochrome. The key design feature is a meso-aryl group that simultaneously projects two shielding arms directly over each face of a linear heptamethine polyene. Cell and mouse imaging experiments compared a shielded heptamethine cyanine dye (and several peptide and antibody bioconjugates) to benchmark heptamethine dyes and found that the shielded systems possess an unsurpassed combination of photophysical, physiochemical, and biodistribution properties that greatly enhance bioimaging performance.

The investigation of unique water-soluble heptamethine cyanine dye for use as NIR photosensitizer in photodynamic therapy of cancer cells

In this paper, a unique water-soluble heptamethine cyanine dye as NIR photosensitizer was synthesized to explore its properties associated with potential applications in photodynamic therapy (PDT). In the strategy of designing this photosensitizer, a sulfonic acid was used as a water soluble functional group and linked to the fluorophore through alkyl chains. 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl(Tempo) moiety was used as the a nitroxide spin label in obtaining biochemical reaction information in vivo due to it could greatly increase the inter-system crossing (ISC) process for triplet-state photosensitizers and low toxicity. As expected, the photosensitizers performed well in vitro photodynamic therapy. There were a remarkable absorbance band located at 692 nm and emission peaks falls at 762 nm, the quantum yield (Φ_f) was calculated to be 12.12% in pure aqueous solution using ICG as standards. The photosensitizer also has high singlet oxygen quantum yield (Φ_△) for 16.96% with NIR LED irradiation. This photosensitizer can rapidly produce singlet oxygen and exhibit high phototoxicity under NIR light irradiation. It has excellent cellular uptake ability and better cell compatibility. It was also successfully applied in Near-infrared fluorescence imaging and AO/EB staining. In a whole, the organic dye based on Heptamethine cyanine used as photosensitizer has great potential in vivo cancer treatment.

Protein labelling and albumin binding characteristics of the near-IR Cy7 fluorophore, QuatCy

Free cysteine residues react with QuatCy 1, by simply mixing the protein and dye in aqueous buffer at 37 °C. Another dye, MHI-148, can be used for a similar labelling protocol, but QuatCy reacts faster with all proteins studied, except albumin; it emerges here that this is because MHI-148 instantly forms of a non-covalent complex with albumin, but QuatCy does not. Labelling with QuatCy has advantages insofar as it is over five times brighter, and much more photostable, than MHI-148, and combination labelling with this dye pair will allow multiplexing in the near-IR region.

QuatCy: A Heptamethine Cyanine Modification With Improved Characteristics

A major restriction on optical imaging techniques is the range of available fluorophores that are compatible with aqueous media without aggregation, absorb light above 750 nm with high extinction coefficients, fluoresce with relatively high quantum yields, and resist photodecomposition. Indocyanine green (ICG or A in this paper) is an important example of a fluorophore that fits this description. Other dyes that are becoming increasingly prevalent are select heptamethine cyanine dyes (Cy7) which feature a cyclohexyl framework to rigidify the conjugated alkenes, and meso-chlorine substitution; MHI-148 (B) is one example. Methods: Research described here was initiated to uncover the consequences of a simple isoelectronic substitution to MHI-148 that replaces a cyclohexyl methylene with a dialkyl ammonium fragment. Solubility experiments were carried out in aqueous and cell culture media, photophysical properties including fluorescence quantum yields, brightness and stability were measured. Moreover, in vivo pharmacokinetics, distribution and tumor seeking properties were also explored. Results: Modification to incorporate dialkyl ammonium fragment leads to a brighter, more photostable fluorophore, with a decreased tendency to aggregation, complementary solubility characteristics, and a lower cytotoxicity. Conclusion: All the above-mentioned parameters are favorable for many anticipated applications of the new dye we now call quaternary cyanine-7 or QuatCy.

Zwitterionic Cross-Linked Biodegradable Nanocapsules for Cancer Imaging

Zwitterionic cross-linked biodegradable nanocapsules (NCs) were synthesized for cancer imaging. A polylactide (PLA)-based diblock copolymer with two blocks carrying acetylenyl and allyl groups respectively was synthesized by ring-opening polymerization (ROP). Azide-alkyne "click" reaction was conducted to conjugate sulfobetaine (SB) zwitterions and fluorescent dye Cy5.5 onto the acetylenyl-functionalized first block of the diblock copolymer. The resulting copolymer with a hydrophilic SB/Cy5.5-functionalized PLA block and a hydrophobic allyl-functionalized PLA block could stabilize miniemulsions because of its amphiphilic diblock structure. UV-induced thiol-ene "click" reaction between a dithiol cross-linker and the hydrophobic allyl-functionalized block of the copolymer at the peripheral region of nanoscopic oil nanodroplets in the miniemulsion generated cross-linked polymer NCs with zwitterionic outer shells. These NCs showed an average hydrodynamic diameter ( D_h) of 136 nm. They exhibited biodegradability, biocompatibility and high colloidal stability. In vitro study indicated that these NCs could be taken up by MIA PaCa-2 cancer cells. In vivo imaging study showed that, comparing to a small molecule dye, NCs had a longer circulation time, facilitating their accumulation at tumors for cancer imaging. Overall, this work demonstrates the applicability of zwitterionic biodegradable polymer-based materials in cancer diagnosis.

Efficient Synthesis of Light-Triggered Circular Antisense Oligonucleotides Targeting Cellular Protein Expression

Light-activated ("caged") antisense oligonucleotides are powerful molecules for regulating gene expression at submicron spatial resolution through the focal modulation of endogenous cellular processes. Cyclized caged oligos are particularly promising structures because of their inherent stability and similarity to naturally occurring circular DNA and RNA molecules. Here, we introduce an efficient route for cyclizing an antisense oligodeoxynucleotide incorporating a photocleavable linker. Oligo cyclization was achieved for several sequences in nearly quantitative yields through intramolecular copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Caging stability and light activation were characterized by FRET efficiency, denaturing gel assay, and melting temperature measurements. Finally, a cyclized caged oligo was designed to target gfap, and it gave a tenfold reduction in glial fibrillary acidic protein upon photoactivation in astrocytes.

Ratiometric Near-Infrared Fluorescent Probes Based On Through-Bond Energy Transfer and π-Conjugation Modulation between Tetraphenylethene and Hemicyanine Moieties for Sensitive Detection of pH Changes in Live Cells

In this paper, we present three ratiometric near-infrared fluorescent probes (A-C) for accurate, ratiometric detection of intracellular pH changes in live cells. Probe A consists of a tetraphenylethene (TPE) donor and near-infrared hemicyanine acceptor in a through-bond energy transfer (TBET) strategy, while probes B and C are composed of TPE and hemicyanine moieties through single and double sp2 carbon-carbon bond connections in a π-conjugation modulation strategy. The specific targeting of the probes to lysosomes in live cells was achieved by introducing morpholine residues to the hemicyanine moieties to form closed spirolactam ring structures. Probe A shows aggregation-induced emission (AIE) property at neutral or basic pH, while probes B and C lack AIE properties. At basic or neutral pH, the probes only show fluorescence of TPE moieties with closed spirolactam forms of hemicyanine moieties, and effectively avoid blind fluorescence imaging spots, an issue which typical intensity-based pH fluorescent probes encounter. Three probes show ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with TPE fluorescence decreases and hemicyanine fluorescence increases, because acidic pH makes the spirolactam rings open to enhance π-conjugation of hemicyanine moieties. However, probe A shows much more sensitive ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with remarkable ratio increase of TPE fluorescence to hemicyanine fluorescence up to 238-fold than probes B and C because of its high efficiency of energy transfer from TPE donor to the hemicyanine acceptor in the TBET strategy. The probe offers dual Stokes shifts with a large pseudo-Stokes shift of 361 nm and well-defined dual emissions, and allows for colocalization of the imaging readouts of visible and near-infrared fluorescence channels to achieve more precisely double-checked ratiometric fluorescence imaging. These platforms could be employed to develop a variety of novel ratiometric fluorescent probes for accurate detection of different analytes in applications of chemical and biological sensing, imaging, and diagnostics by introducing appropriate sensing ligands to hemicyanine moieties to form on-off spirolactam switches.

A cyanine-based fluorescent cassette with aggregation-induced emission for sensitive detection of pH changes in live cells

An aggregation-induced emission (AIE) cyanine-based fluorescent cassette with a large pseudo-Stokes shift was designed and prepared to sensitively image pH changes in live cells via through-bond energy transfer (TBET) from a tetraphenylethene (TPE) donor to a cyanine acceptor.

Development of cyanine probes with dinitrobenzene quencher for rapid fluorogenic protein labelling

A multicolour protein labelling technique using a protein tag and fluorogenic probes is a powerful approach for spatio-temporal analyses of proteins in living cells. Since cyanine fluorophores have attractive properties for multicolour imaging of proteins, there is a huge demand to develop fluorogenic cyanine probes for specific protein labelling in living cells. Herein, we develop fluorogenic cyanine probes for labelling a protein tag by using a dinitrobenzene fluorescence quencher. The probes enhanced fluorescence intensity upon labelling reactions and emitted orange or far-red fluorescence. Intramolecular interactions between the cyanine fluorophores and the dinitrobenzene quencher led not only to fluorescence quenching of the probes in the free state but also to promotion of labelling reactions. Furthermore, the probes successfully imaged cell-surface proteins without a washing process. These findings offer valuable information on the design of fluorogenic cyanine probes and indicate that the probes are useful as novel live-cell imaging tools.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

Imaging of radicals following injury or acute stress in peripheral nerves with activatable fluorescent probes

Peripheral nerve injury evokes a complex cascade of chemical reactions including generation of molecular radicals. Conversely, the reactions within nerve induced by stress are difficult to directly detect or measure to establish causality. Monitoring these reactions in vivo would enable deeper understanding of the nature of the injury and healing processes. Here, we utilized near-infrared fluorescence molecular probes delivered via intra-neural injection technique to enable live, in vivo imaging of tissue response associated with nerve injury and stress. These initially quenched fluorescent probes featured specific sensitivity to hydroxyl radicals and become fluorescent upon encountering reactive oxygen species (ROS). Intraneurally delivered probes demonstrated rapid activation in injured rat sciatic nerve but minimal activation in normal, uninjured nerve. In addition, these probes reported activation within sciatic nerves of living rats after a stress caused by a pinprick stimulus to the abdomen. This imaging approach was more sensitive to detecting changes within nerves due to the induced stress than other techniques to evaluate cellular and molecular changes. Specifically, neither histological analysis of the sciatic nerves, nor the expression of pain and stress associated genes in dorsal root ganglia could provide statistically significant differences between the control and stressed groups. Overall, the results demonstrate a novel imaging approach to measure ROS in addition to the impact of ROS within nerve in live animals.

Synthesis of nitric oxide probes with fluorescence lifetime sensitivity

We present the rationale, synthesis and evaluation of the first activatable fluorescent probe that utilizes fluorescence lifetime change for detection of nitric oxide. The new probe DAP-LT1 features a near-infrared polymethine skeleton with a diaminobenzene functionality incorporated into the meso-position. The probe is partially quenched, and upon reaction with nitric oxide shows an increase in the fluorescence lifetime from 1.08 ns to 1.24 ns.

A fluorogenic probe for β-galactosidase activity imaging in living cells

A cell permeable fluorescence turn-on probe, AcGQCy7, was developed to image β-galactosidase activity in living cells. Once internalized by β-galactosidase-expressing cells, the probe was hydrolyzed into a highly fluorescent molecule, and the fluorescent signal was retained in mitochondria for several days. This resulted in a long-lasting and strong β-galactosidase-dependent intracellular fluorescent signal with little background fluorescence in the culture media.

Efficient construction of PET/fluorescence probe based on sarcophagine cage: an opportunity to integrate diagnosis with treatment

PURPOSE

Due to the shortage of established platforms/methods for multimodality probe construction, in this study, we developed a heterofunctional chelator, BaAn(Boc)Sar, from sarcophagine cage as a general platform for dual-modality probe construction.

PROCEDURES

A dual-modality probe for positron-emission tomography (PET) and fluorescence imaging was synthesized using the developed BaAn(Boc)Sar chelator. The c(RGDyK)(2) peptide (denoted as RGD(2)) and fluorescence dye Cy5.5 were conjugated with BaAn(Boc)Sar to form BaAnSar-RGD(2)-Cy5.5. Then, BaAnSar-RGD(2)-Cy5.5 was labeled with (64)Cu in ammonium acetate buffer. PET and fluorescent imaging were carried out to evaluate (64)Cu-BaAnSar-RGD(2)-Cy5.5 in nude mice bearing U87MG glioblastoma xenograft.

RESULTS

The BaAnSar-RGD(2)-Cy5.5 was labeled with (64)Cu very efficiently in 0.1 M NH(4)OAc buffer within 10 min at 37 °C in the yield of 86.7 ± 4.4 % (n = 3). The specific activity of (64)Cu-BaBaSar-RGD(2) was controlled at 50-200 mCi/μmol for the consideration of both PET and optical imaging. MicroPET quantification analysis shows that the U87MG tumor uptake is 6.41 ± 0.28, 6.51 ± 1.45, and 5.92 ± 1.57 %ID/g at 1, 4, and 20 h postinjection, respectively. Good correlation was obtained between the tumor to muscle ratios measured by the radioactivity and fluorescence intensity. As a proof of concept, an animal surgery study demonstrated that this dual-modality probe would greatly benefit the patients because the PET moiety could be used for tumor detection, and the fluorescent moiety would allow image-guided surgery.

CONCLUSIONS

Our findings demonstrated the effectiveness and feasibility of preparing dual-modality imaging probes based on the sarcophagine scaffold. The resulting PET and fluorescent imaging probe also holds a great potential for clinical translation.

Synthesis and validation of cyanine-based dyes for DIGE

The application of difference gel electrophoresis (DIGE), in particular its most common "minimal labeling" variety, utilizes N-hydroxysuccinimide esters of Cy2, Cy3, and Cy5 dyes, which are commercially available. We describe methods for the efficient synthesis of all three dyes from relatively inexpensive and commercially available precursors in only a few steps and with relatively high yields. In model DIGE experiments, the newly synthesized dyes proved to be indistinguishable from commercially available ones and have been shown to be stable for years while stored under argon as dry solids or after being dissolved in N,N-dimethylformamide.

Synthesis of a new beta-naphthothiazole monomethine cyanine dye for the detection of DNA in aqueous solution

Novel monomethine cyanine dye (MC) derived from beta-naphthothiazole and benzothiazole has been prepared and characterized by (1)H and (13)C NMR, FTIR, ESIMS, elemental analyses, absorption and fluorescence spectroscopy. The dye was conveniently synthesized by the condensation of two sulfate heterocyclic quaternary salts. The interaction between calf thymus DNA (ct-DNA) in tris(hydroxymethyl)aminomethane-HCl (Tris-HCl) aqueous buffer solution and MC has been studied with spectral fluorescence method. The binding constant value has been determined by fluorescence titration of MC with ct-DNA concentrations. The result obtained is consistent with an intercalative binding interaction between MC and ct-DNA. Compared with ethidium bromide (EB), MC showed a huge fluorescence enhancement upon mixing with ct-DNA.

Microwave synthesis of cyanine dyes

Heptamethine cyanine dyes are a class of near infrared (NIR) dyes that have captured the interest of the scientific community. Although applications that utilize NIR fluorescence technology are rapidly expanding, progress is limited by the lack of availability and cost of suitable compounds that can be utilized as labels and/or probes. Herein, we report the use of microwave assisted organic synthesis of five NIR cyanine dyes in yields ranging from 64-83% with a significant reduction in solvent use. Spectra characteristics including absorbance and emission spectra, molar absorptivity, quantum yield, fluorescence lifetime, and redox potentials were determined for each synthesized NIR cyanine dye.

Validation of self-made fluorescent cyanine dyes for 2D gel-based multi-fluorescence protein analysis

Two-dimensional gel electrophoresis (2-DE) in combination with quantitative multi-fluorescence protein analysis (MFA) is the most versatile methodical tool for differential analysis of protein mixtures or even complex proteomes. It is based on covalent labelling of proteins with fluorescent cyanine dyes (Ethyl-Cy2, Propyl-Cy3 or Methyl-Cy5) before isoelectric focussing, enabling differential tagging of up to three samples which are finally separated on the same 2-D gel. To minimize costs and to increase the number of possible experiments, the cyanine dye NHS esters were synthesized in our own lab according to a protocol published by Jung and Kim (2006) . Self-made cyanine dyes were tested by studying their labelling and fluorescent properties and possible effects on the electrophoretic mobility of labelled proteins. To validate the potential use as labels in 2-DE/MFA experiments, dyes were used for the differential analysis of the proteome of thrombin-stimulated human vascular smooth muscle cells (VSMCs).

Novel, Monomeric Cyanine Dyes as Reporters for DNA Helicase Activity

The dimeric cyanine dyes, YOYO-1 and TOTO-1, are widely used as DNA probes because of their excellent fluorescent properties. They have a higher fluorescence quantum yield than ethidium homodimer, DAPI and Hoechst dyes and bind to double-stranded DNA with high affinity. However, these dyes are limited by heterogeneous staining at high dye loading, photocleavage of DNA under extended illumination, nicking of DNA, and inhibition of the activity of DNA binding enzymes. To overcome these limitations, seven novel cyanine dyes (Cyan-2, DC-21, DM, DM-1, DMB-2OH, SH-0367, SH1015-OH) were synthesized and tested for fluorescence emission, resistance to displacement by Mg(2+), and the ability to function as reporters for DNA unwinding. Results show that Cyan-2, DM-1, SH-0367 and SH1015-OH formed highly fluorescent complexes with dsDNA. Of these, only Cyan-2 and DM-1 exhibited a large fluorescence enhancement in buffers, and were resistant to displacement by Mg(2+). The potential of these two dyes to function as reporter molecules was evaluated using continuous fluorescence, DNA helicase assays. The rate of DNA unwinding was not significantly affected by either of these two dyes. Therefore, Cyan-2 and DM-1 form the basis for the synthesis of novel cyanine dyes with the potential to overcome the limitations of YOYO-1 and TOTO-1.

New amino and acetamido monomethine cyanine dyes for the detection of DNA in agarose gels

Some new monomethine cyanine dyes derived from quinoline and benzothiazole have been prepared and characterized by (1)H and (13)C NMR, FTIR, FABHRMS, and visible spectroscopy. The dyes containing amino and acetamido groups were conveniently synthesized by the condensation of two p-toluenesulfonate heterocyclic quaternary salts and were obtained in the forms of iodide, bromide, and tosylate counteranions. These dyes were compared to ethidium bromide as stains for DNA in electrophoretic gels. The overall results obtained for the sensitivity of these dyes suggest the suitability of acetamido moiety over the amine one and bromide as the counteranion when compared with iodide and tosylate, with a similar capacity of DNA detection in relation to the ethidium bromide stain over the concentration range of 1-3ng.

Heptamethine cyanine dyes with a robust C-C bond at the central position of the chromophore

Novel, highly fluorescent, monofunctional, water-soluble heptamethine cyanine dyes containing a robust C-C bond at the central position of the near-infrared fluorophore system were prepared by the Suzuki-Miyaura method. The reaction proceeded efficiently to replace the meso-chlorine atom with a carboxy-functionalized aryl moiety and afforded the desired compounds in high yields. This methodology is particularly attractive due to its versatility and the utilization of environmentally friendly water as solvent. The new compounds possess excellent spectral properties and readily label bioactive molecules on solid support. The results demonstrate the potential of using the new compounds as fluorescent antennae for molecular imaging, spectroscopy, microscopy, and chemical or biological molecular recognition studies.

Preparation of an ordered array of cyanine complex microdomes by a simple dewetting method

We demonstrate a simple method for fabricating a two-dimensional array of microdomes that consist of cyanine dye complexes. Investigation of the morphology and the fluorescence emission of microdomes was carried out before/after annealing. The principal of microdome formation is "dewetting," which is a self-organization phenomena. Generally, one can observe dewetting when a liquid film breaks spontaneously on a nonwettable substrate, leaving droplets or patterns on the substrate. A cyanine dye complex was prepared from a cationic cyanine dye and an anionic amphiphile, or vice versa, an anionic dye and a cationic amphiphile. When a chloroform solution of the cyanine complex was spread on a glass substrate by a roller, microdomes of the cyanine dye complex formed in dewetted films. The roller draws the three-phase line (the air-solid-liquid boundary of the droplet of the chloroform solution) with a constant rate. Thus dewetting can be controlled and leads to a two-dimensional ordered array of uniform sized microdomes. The diameter and height of microdomes decrease with increasing roller speed. Fluorescence microscopy shows that the cyanine dye complex formed J-aggregates. Annealing caused transformation of the dome morphology and a change of the fluorescence spectra. The microdome transformed into anisotropic crystals or became amorphous depending on the molecular structure of the cyanine dye.

Novel Water-Soluble Near-Infrared Cyanine Dyes: Synthesis, Spectral Properties, and Use in the Preparation of Internally Quenched Fluorescent Probes

In this paper, we describe the synthesis and the photophysical properties of two novel near-infrared (NIR) cyanine dyes (NIR5.5-2 and NIR7.0-2) which are water soluble potential substitutes of the commercially available Cy 5.5 and Cy 7.0 fluorescent labels respectively. For each one of these cyanine dyes, the synthetic strategy relies on the postsynthetic derivatization of a cyanine precursor in order to introduce the key functionalities required for bioconjugation of these NIR fluorophores. For NIR5.5-2, a reactive amino group was acylated with an original trisulfonated linker for water solubility. For NIR7.0-2, a vinylic chlorine atom was derivatized through a SRN1 reaction for the introduction of a monoreactive carboxyl group for labeling purposes. Unexpectedly, when these two fluorophores were closely associated within a peptidic architecture, mutual fluorescence quenching between NIR5.5-2 and NIR7.0-2 was observed both at 705 (NIR5.5-2) and 798 nm (NIR7.0-2). On the basis of this property, a novel internally quenched caspase-3-sensitive NIR fluorescent probe was prepared.

Immobilization of Aprotinin to Fibrinogen as a Novel Method for Controlling Degradation of Fibrin Gels

The goal of this work was to demonstrate that aprotinin conjugated to fibrinogen could (1) maintain its function and (2) control fibrin degradation. Using the chick chorioallantoic membrane (CAM) assay, we found that blood vessels did not directly invade fibrin constructs containing immobilized fibroblast growth factor-2. Because the fibrin quickly degraded within approximately 5 days, we hypothesized that controlling fibrinolysis may improve direct blood vessel invasion. Aprotinin, a protease inhibitor typically added to slow fibrinolysis, is a small protein and can diffuse out of the gel resulting in the loss of fibrinolysis protection. Therefore, using a novel synthesis strategy, aprotinin and a fluorescent reporter, Cy3, were chemically conjugated to fibrinogen. In vitro microplate absorbance assays showed that the conjugated aprotinin was able to inhibit plasmin-mediated fibrin degradation and that its activity was comparable to equimolar levels of soluble, nonconjugated aprotinin. Additionally, we found that fibrinolysis rates could be tuned by varying the level of conjugated aprotinin within the gel. The conjugated aprotinin also demonstrated functionality in vivo. In the chick CAM assay, fibrin gels containing conjugated aprotinin were approximately 5 times larger than gels containing soluble aprotinin after 4 days. Also, in support of our hypothesis, we found that immobilized aprotinin within fibrin gels demonstrated substantial blood vessel invasion.

Fluorescent fructose derivatives for imaging breast cancer cells

Breast cancer cells are known to overexpress Glut5, a sugar transporter responsible for the transfer of fructose across the cell membrane. Since Glut5 transporter is not significantly expressed in normal breast cells, fructose uptake can potentially be used to differentiate between normal and cancerous cells. Fructose was labeled with two fluorophores at the C-1 position: 7-nitro-1,2,3-benzadiazole (NBD) and Cy5.5. The labeling site was chosen on the basis of the presence and substrate specificity of the key proteins involved in the first steps of fructose metabolism. Using fluorescence microscopy, the uptake of the probes was studied in three breast cancer cell lines: MCF 7, MDA-MB-435, and MDA-MB-231. Both fluorescent fructose derivatives showed a very good uptake in all tested cell lines. The level of uptake was comparable to that of the corresponding glucose analogs, 2-NBDG and Cy5.5-DG. Significant uptake of 1-NBDF derivative was not observed in cells lacking Glut5 transporter, while the uptake of the 1-Cy5.5-DF derivative was independent of the presence of a fructose-specific transporter. While 1-NBDF showed Glut5-specific accumulation, the coupling of a large fluorophore such as Cy5.5 likely introduces big structural and electronic changes, leading to a fructose derivative that does not accurately describe the uptake of fructose in cells.

A fluorescent photoprobe for the imaging of endothelin receptors

A novel fluorescent photoprobe for the imaging of endothelin A receptors (ET(A)R) was developed. Based on the nonpeptidyl, high-affinity, and selective ET(A)R antagonist 3-benzo[1,3]dioxol-5-yl-5-hydroxy-5-(4-methoxyphenyl)-4-(3,4,5-trimethoxybenzyl)-5H-furan-2-one (PD 156707), a modification of the lead structure with a PEG-spacer containing an amino moiety was performed. Labeling of this precursor with the fluorescent marker Cy 5.5 NHS-ester was accomplished by adaption of common peptide labeling procedures. The affinity of the Cy 5.5-labeled receptor antagonist was evaluated using human carcinoma cell lines with different degrees of ET(A)R expression. Fluorescence microscopy revealed that ET(A)R-positive MCF-7 human breast adenocarcinoma and HT-1080 human fibrosarcoma cells effectively bind the photoprobe at very low doses (nM), while ET(A)R-negative MDA-MB-435 human breast cancer cells showed no fluorescence signal. Binding specificity of the probe could be demonstrated by predosing with a specific ET(A)R antibody or the parent antagonist PD 156707 as a competing inhibitor. The results suggest that the modified photoprobe tightly binds to ET(A) receptors and thus may be a possible candidate for the imaging of ET(A)R-overexpressing tissues in vivo.

Modulation of nuclear internalization of Tat peptides by fluorescent dyes and receptor-avid peptides

The nuclear internalization of biomolecules by Tat peptide provides a mechanism to deliver drugs to cells. However, translocation of molecular imaging probes to the nucleus may induce undesirable mutagenesis. To assess the feasibility of retaining its cell permeating effect without nuclear translocation, Tat-peptide was conjugated with a somatostatin receptor (STR)-avid ligand (Oct) and labeled with fluorescent dyes. The results show that Tat-Oct-5-FAM (fluorescein 5'-carboxylic acid) remained in the cytoplasm of STR-positive AR42J cells. Co-incubation of Tat-Oct-5-FAM with ATP induced nuclear translocation. These data suggest that both dye and Oct-STR endocytosis complex could modulate nuclear internalization of Tat peptides.

New hexamethine–hemicyanine dyes for the development of integrated optochemical sensors

New far-visible absorbing anilino-cyanine dyes have been synthesised for future application as chromoionophores in integrated waveguide absorbance optodes based on bulk optodes. The effect of the heterocycle, of the substitution of the heterocyclic nitrogen and of the type of heptamethine central ring on the pKa values (4.3-8.2 in ethanol-water solutions and 9.5-11.0 in plasticised PVC membranes), on the spectroscopic characteristics of the dye and on photostability is discussed. pH-selective bulk optodes have been formulated as a first approach to develop ion-selective optodes, and sensitivity, repeatability, lifetime and response time have been determined. The dyes show good analytical behaviour for use as chromoionophores for the development of ion-selective optodes. Reversible (80-87%), fast (tr90%=0.94-2.28 min) and pH-sensitive membranes (slopes of 0.09-0.23 DeltaAbs.pHdec-1, absorbance range 0.19-0.53) have been obtained. Moreover, they exhibit good spectroscopic features for employment with integrated optochemical sensors: absorption maxima of the acidic species in plasticised PVC membranes matched those of 650-670-nm LEDs, high molar absorption coefficients (epsilonacidic=3.5x10(4)-9.3x10(4) L mol-1 cm-1 and epsilonbasic=1.9x10(4)-6.7x10(4) L mol-1 cm-1) and fluorescence.

6,6'-Disubstituted benzothiazole trimethine cyanines--new fluorescent dyes for DNA detection

The influence of methyl-, 2-hydroxyethyl-, dimethyl-, diethyl- and benzoyl-amino substituents in the 6,6'-positions of benzothiazole heterocycle of trimethine cyanines on their spectral-luminescent properties and behavior in presence of DNA, RNA and BSA was studied. It was shown that incorporation of 6,6'-substituents generally leads to the increase in dyes tendency to aggregation, resulting in the considerable decrease in the emission intensity of the disubstituted dyes as compared to the unsubstituted ones. Emission of the studied 6,6'-disubstited dyes in DNA presence is considerably more intensive than in presence of RNA, that points on the existing of DNA binding preference for the mentioned dyes. Insertion of benzoyl-amino groups into the 6,6'-positions permitted us to design the DNA-sensitive dyes on the basis of symmetric trimethine cyanines with unsubstituted polymethine chain, while typically such dyes slightly respond on the presence of biopolymers. 6,6'-Benzoyl-amino-disubstituted trimethine cyanines are proposed as efficient dyes for DNA detection.

Synthesis of a red-shifted fluorescence polarization probe for Hsp90

The synthesis of a red-shifted cy3B-GM ligand and its evaluation as a fluorescence polarization probe for Hsp90 is presented.

Design, synthesis, and evaluation of near infrared fluorescent multimeric RGD peptides for targeting tumors

Molecular interactions between RGD peptides and integrins are known to mediate many biological and pathological processes. This has led to an increased interest in the development of RGD compounds with high affinity and improved selectivity for integrin receptors. In this study, we synthesized and evaluated a series of multimeric RGD compounds constructed on a dicarboxylic acid-containing near-infrared (NIR) fluorescent dye (cypate) for tumor targeting. An array of NIR fluorescent RGD compounds was prepared efficiently, including one RGD monomer (cypate-(RGD)(2)-NH(2)), two RGD dimers (cypate-(RGD)(2)-NH(2) and cypate-(RGD-NH(2))(2)), one trimer (cypate-(RGD)(3)-NH(2)), two tetramers (cypate-(RGD)(4)-NH(2) and cypate-[(RGD)(2)-NH(2)](2)), one hexamer (cypate-[(RGD)(3)-NH(2)](2)), and one octamer (cypate-[(RGD)(4)-NH(2)](2)). The binding affinity of the multimeric RGD compounds for alpha(v)beta(3) integrin receptor (ABIR) showed a remarkable increase relative to the monomer cypate-RGD-NH(2). Generally, the divalent linear arrays of the multimeric RGD units bound the ABIR with slightly higher affinity than their monovalent analogues. These results suggest that the receptor binding affinity was not only dependent on the number of RGD moieties but also on the spatial alignments of the pendant peptides. Internalization of the compounds by ABIR-positive tumor cells (A549) was monitored by NIR fluorescence microscopy. The data showed that endocytosis of the octameric RGD derivative was significantly higher by comparison to other compounds in this study. In vivo noninvasive optical imaging and biodistribution data showed that the compounds were retained in A549 tumor tissue. These results clearly demonstrated that an array of simple RGD tripeptides on a NIR fluorescent dye core can be recognized by ABIR. Optimization of the spatial alignment of the RGD moieties through careful molecular design and library construction could induce multivalent ligand-receptor interactions useful for in vivo tumor imaging and tumor-targeted therapy.

Novel Heptamethine Cyanine Dyes with Large Stokes’ Shift for Biological Applications in the Near Infrared

A series of novel functionalized, water-soluble, pH-unsensitive, highly photostable heptamethine cyanine dyes (HCDs) has been synthesized. The aim of the synthesis was to obtain novel effective probes for fluorescence detection in the near infrared. Synthesis and characterization of a special HCD with large Stokes' shift (>100 nm), bioconjugation to IgG and effect of pH upon the new structure are presented.

Fluorescence Probe with a pH-Sensitive Trigger

Acid-catalyzed hydrolysis was used as the mechanism to design a new type of environmentally sensitive fluorescence probe. A mild and selective periodate oxidation of the 2-amino alcohol of serine in the presence of a disulfide bond was developed to prepare dialdehyde peptides. Two identical fluorochrome hydrazide derivatives were then linked to the dialdehyde peptide forming an acid-labile hydrazone linkage. This self-quenched probe is weakly fluorescent at a physiological pH of 7.4 but shows more than 3-fold fluorescence enhancement at pH 4.5.

Multivalent carbocyanine molecular probes: synthesis and applications

Synergistic multivalent interactions can amplify desired chemical or biological molecular recognitions. We report a new class of multicarboxylate-containing carbocyanine dye constructs for use as optical scaffolds that not only serve as fluorescent antennas but also participate in structural assembly of the multivalent molecular construct. Three generations of carboxylate-terminating multivalent near-infrared carbocyanine probes from a dicarboxylic acid precursor dye (cypate) were prepared via its imino diacetic acid derivatives. Conjugation of the probes with D-(+)-glucosamine afforded dendritic arrays of the carbohydrates on an inner NIR chromophore core. All the multicarboxylate probes and their glucosamine conjugates have similar NIR spectral properties because conjugation occurred at distal positions to the inner chromophore core, thereby providing consistent and predictable spectral properties for their biological applications. Although light-induced photodamage equally affected the precursor dye, multicarboxylate probes, and their glucosamine derivatives, we observed that octacarboxylcypate (multivalent probe) was remarkably stable in different mediums at physiologically relevant temperatures relative to cypate, especially in basic mediums. Biodistribution studies in tumor-bearing nude mice show that all the glucosamine conjugates localized in the tumor but cypate was almost exclusively retained in the liver at 24 h postinjection. The tumor uptake does not correlate with the number of glucosamine tether on the multicarboxylate probe. Overall, the triglucosamine derivative appears to offer the best balance between high tumor uptake and low retention in nontarget tissues. These results suggest that multivalent molecular beacons are useful for assessing the beneficial effects of multivalency and for optimizing the biological and chemical properties of tissue-specific molecular probes.

Proteomic analysis of redox- and ErbB2-dependent changes in mammary luminal epithelial cells using cysteine- and lysine-labelling two-dimensional difference gel electrophoresis

Differential protein expression analysis based on modification of selected amino acids with labelling reagents has become the major method of choice for quantitative proteomics. One such methodology, two-dimensional difference gel electrophoresis (2-D DIGE), uses a matched set of fluorescent N-hydroxysuccinimidyl (NHS) ester cyanine dyes to label lysine residues in different samples which can be run simultaneously on the same gels. Here we report the use of iodoacetylated cyanine (ICy) dyes (for labelling of cysteine thiols, for 2-D DIGE-based redox proteomics. Characterisation of ICy dye labelling in relation to its stoichiometry, sensitivity and specificity is described, as well as comparison of ICy dye with NHS-Cy dye labelling and several protein staining methods. We have optimised conditions for labelling of nonreduced, denatured samples and report increased sensitivity for a subset of thiol-containing proteins, allowing accurate monitoring of redox-dependent thiol modifications and expression changes. Cysteine labelling was then combined with lysine labelling in a multiplex 2-D DIGE proteomic study of redox-dependent and ErbB2-dependent changes in epithelial cells exposed to oxidative stress. This study identifies differentially modified proteins involved in cellular redox regulation, protein folding, proliferative suppression, glycolysis and cytoskeletal organisation, revealing the complexity of the response to oxidative stress and the impact that overexpression of ErbB2 has on this response.

Cell-permeable near-infrared fluorogenic substrates for imaging beta-lactamase activity

This communication describes a design of cell-permeable near-infrared fluorogenic substrates for imaging beta-lactamase expression in living mammalian cells. This design is based on fluorescence energy transfer resonance and utilizes a peracetylated d-glucosamine to facilitate the transport of the near-infrared probe across cell membranes. This new type of fluorogenic probe may also be applied to image gene expression in living animals.

Solid-Phase Methods for the Synthesis of Cyanine Dyes

We report here a series of studies that explore solid-phase methodologies for the synthesis of various cyanine dyes. The scope of the previously reported catch-and-release method using sulfonyl chloride resin(1) has now been extended to include pentamethine and water-soluble cyanine dyes. We also report a new and chemically distinct synthetic strategy, employing the stepwise attack of heterocyclic carbon nucleophiles on immobilized polyene-chain precursors, allowing the clean synthesis of hydrophobic and hydrophilic trimethine and pentamethine dyes from more easily obtained starting materials. Overall, both approaches appear to be robust and versatile strategies to delivering a wide range of cyanine-based dyes in high purity.

Cy3B: improving the performance of cyanine dyes

The spectral properties of a rigidified trimethine cyanine dye, Cy3B have been characterised. This probe has excellent fluorescent properties, good water solubility and can be bioconjugated. The emission properties of this fluorophore have also been investigated upon conjugation to an antibody. This study compared the conjugated emission properties of Cy3B with other commercially available fluorophores emitting at similar wavelengths.

Synthesis and antimicrobial activity of meso-substituted polymethine cyanine dyes

The condensation reaction of equivalent amounts of 2-cyanomethyl benzooxazole or its derivatives with variously substituted aromatic aldehydes gave 2-cyano-styryl benzooxazole or its derivatives. The subsequent reaction of the 2-cyano-styryl benzooxazoles with 2(4)-methyl substituted heterocyclic quaternary salts afforded meso-substituted styryl-2(4)-polymethine cyanines. The condensation reaction of 2-cyanomethyl benzooxazole or its derivatives with alpha-nitroso-beta-naphthol followed by reaction with 2(4)-methyl substituted heterocyclic quaternary salts gave meso-substituted aza-2(4)-polymethine cyanines. The reaction of 2-cyanomethyl benzooxazole or its derivatives with N-methyl heterocyclic quaternary salts followed by the reaction with 2-methylquinolinium methiodide afforded the corresponding meso-substituted trimethine cyanine dyes. Elemental analyses, visible absorption, IR, (1)H NMR spectroscopy, and mass spectra established the structures of these compounds. The relationship between the structure and properties of these dyes has been studied and the solvatochromic behavior of some selected cyanine dyes in organic solvents is discussed. Finally, the antimicrobial activity of selected novel dyes was investigated in vitro using a wide spectrum of microbial strains.

Synthesis, Spectroscopy, and Electrochemistry of Tetra-tert-butylated Tetraazaporphyrins, Phthalocyanines, Naphthalocyanines, and Anthracocyanines, together with Molecular Orbital Calculations

Tetraazaporphyrins (TAPs), phthalocyanines (Pcs), naphthalocyanines (Ncs), and anthracocyanines (Acs) with four tert-butyl groups attached at similar positions have been synthesized, and their electronic absorption, magnetic circular dichroism (MCD), IR, and voltammetric properties were studied and interpreted with the help of quantum-mechanical calculations. Through the preparation of a series of compounds with the same number of the same substituent, the effects of the increase in the size of the ring system were clearly derived. The main results may be summarized as follows. 1) The Q band shifts to longer wavelength and its intensity increases, but with decreasing degree of change with increasing molecular size. If the size of the effect of benzene directly fused to the TAP skeleton is set at unity, the effects of the second and third benzene units are roughly 0.8 and 0.5, respectively. 2) The splitting of the Q bands in metal-free compounds decreases with increasing molecular size, so that the Q bands of H2Nc and H2Ac appear as single bands. 3) The magnitude of the orbital angular momentum of the excited state of the ligand decreases with increasing molecular size. 4) Interestingly, the ring current, as judged from the positions of pyrrole proton signals in the 1H NMR spectrum, appears to decrease with increasing molecular size. 5) The first reduction potential becomes less negative, but only slightly, whereas the first oxidation potential shows a marked shift to less positive values with increasing molecular size, indicating that the HOMO destabilizes significantly as the molecule becomes larger. 6) In 5), the extent of the HOMO destabilization with molecular size differs depending on the central metal, so metals producing smaller destabilization effects can allow larger macrocycles. Of the metals studied, the most effective is cobalt, and the practical size limit is represented by the Acs. 7) The IR spectra become simpler the larger the molecule, and the main bands were assigned by DFT calculations. 8) The trend in experimentally determined redox potentials and electronic absorption and MCD spectra were reasonably reproduced by MO calculations using the ZINDO/S Hamiltonian. 9) EPR data for several metallocomplexes are also reported.

Improved photostability and fluorescence properties through polyfluorination of a cyanine dye

[structure: see text] A polyfluorinated cyanine dye has been synthesized and characterized. Compared with the nonfluorinated analogue, the dye exhibits significantly reduced aggregation in aqueous media, enhanced fluorescence quantum yield, greater resistance to photobleaching upon direct irradiation, and reduced reactivity toward singlet oxygen. All of these properties are favorable for use of cyanine dyes as fluorescent labels and point toward fluorination as a general strategy for improving performance in imaging applications.

Synthesis and reactions of N-methylbenzylammonium fluorochromate(VI) on silica gel, a selective and efficient heterogeneous oxidant

N-Methylbenzylammonium fluorochromate(VI) (MBAFC) is easily synthesized by addition of N-methylbenzylamine to an aqueous solution of CrO3 and HF. MBAFC shows selectivity in the oxidation of aryl alcohols to their corresponding aldehydes and ketones under mild conditions. The durability, ease of work up and efficiency of MBAFC are considerably increased upon its absorption on silica gel.

Polyvalent carbocyanine molecular beacons for molecular recognitions

Polyvalent carboxylate-terminating near-infrared (NIR) carbocyanine molecular beacons were prepared by homologation of reactive carboxyl groups of the beacon with imino diacetic acid. Their conjugation with unprotected d-(+)-glucosamine gave dendritic arrays of the carbohydrate on an inner NIR chromophore core. In vivo evaluation of the dendritic glucosamine constructs shows enhanced uptake in proliferating tumor cells relative to surrounding normal tissue. The structural framework of these polyvalent beacons permits the amplification by synergistic effects of a variety of bioactive motifs or chemical sensors in molecular recognition interactions without dramatic change of their desirable NIR spectral properties.