Enhanced optical imaging and fluorescent labeling for visualizing drug molecules within living organisms

The visualization of drugs in living systems has become key techniques in modern therapeutics. Recent advancements in optical imaging technologies and molecular design strategies have revolutionized drug visualization. At the subcellular level, super-resolution microscopy has allowed exploration of the molecular landscape within individual cells and the cellular response to drugs. Moving beyond subcellular imaging, researchers have integrated multiple modes, like optical near-infrared II imaging, to study the complex spatiotemporal interactions between drugs and their surroundings. By combining these visualization approaches, researchers gain supplementary information on physiological parameters, metabolic activity, and tissue composition, leading to a comprehensive understanding of drug behavior. This review focuses on cutting-edge technologies in drug visualization, particularly fluorescence imaging, and the main types of fluorescent molecules used. Additionally, we discuss current challenges and prospects in targeted drug research, emphasizing the importance of multidisciplinary cooperation in advancing drug visualization. With the integration of advanced imaging technology and molecular design, drug visualization has the potential to redefine our understanding of pharmacology, enabling the analysis of drug micro-dynamics in subcellular environments from new perspectives and deepening pharmacological research to the levels of the cell and organelles.

Inserting "OFF-to-ON" BODIPY Tags into Cytokines: A Fluorogenic Interleukin IL-33 for Real-Time Imaging of Immune Cells

The essential functions that cytokine/immune cell interactions play in tissue homeostasis and during disease have prompted the molecular design of targeted fluorophores to monitor their activity in real time. Whereas activatable probes for imaging immune-related enzymes are common, many immunological functions are mediated by binding events between cytokines and their cognate receptors that are hard to monitor by live-cell imaging. A prime example is interleukin-33 (IL-33), a key cytokine in innate and adaptive immunity, whose interaction with the ST2 cell-surface receptor results in downstream signaling and activation of NF-κB and AP-1 pathways. In the present work, we have designed a chemical platform to site-specifically introduce OFF-to-ON BODIPY fluorophores into full cytokine proteins and generate the first nativelike fluorescent analogues of IL-33. Among different incorporation strategies, chemical aminoacylation followed by bioorthogonal derivatization led to the best labeling results. Importantly, the BODIPY-labeled IL-33 derivatives-unlike IL-33-GFP constructs-exhibited ST2-specific binding and downstream bioactivity profiles comparable to those of the wild-type interleukin. Real-time fluorescence microscopy assays under no wash conditions confirmed the internalization of IL-33 through ST2 receptors and its intracellular trafficking through the endosomal pathway. We envision that the modularity and versatility of our BODIPY labeling platform will facilitate the synthesis of minimally tagged fluorogenic cytokines as the next generation of imaging reagents for real-time visualization of signaling events in live immune cells.

Novel O-benzylcinnamic acid derivative L26 treats acute lung injury in mice by MD-2

Acute lung injury (ALI) is an inflammation-mediated respiratory disease that is associated with a high mortality rate. In this study, a series of novel O-benzylcinnamic acid derivatives were designed and synthesized using cinnamic acid as the lead compound. We tested the preliminary anti-inflammatory activity of the compounds by evaluating their effect on inhibiting the activity of alkaline phosphatase (ALP) in Hek-Blue-TLR4 cells, in which compound L26 showed the best activity and 7-fold more active than CIN. ELISA, immunoprecipitation, and molecular docking indicated that L26 targeted MD-2 protein and competed with LPS to bind to MD-2, which resulted in the inhibition of inflammation. In the LPS-induced mouse model of ALI, L26 was found to decrease ALP activity and inflammatory cytokine TNF-α release to reduce lung injury by inhibiting the NF-κB signaling pathway. Acute toxicity experiments showed that high doses of L26 did not cause adverse reactions in mice, and it was safe in vivo. Also, the preliminary pharmacokinetic parameters of L26 were investigated in SD rats (T_1/2 = 4.246 h). In summary, L26 exhibited optimal pharmacodynamic and pharmacokinetic characteristics, which suggested that L26 could serve as a potential agent for the development of ALI treatment.

Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging

The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.

Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging

The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.

Solvatochromic Sensitivity of BODIPY Probes: A New Tool for Selecting Fluorophores and Polarity Mapping

This research work is devoted to collecting a high-quality dataset of BODIPYs in a series of 10-30 solvents. In total, 115 individual compounds in 71 solvents are represented by 1698 arrays of the spectral and photophysical properties of the fluorophore. Each dye for a series of solvents is characterized by a calculated value of solvatochromic sensitivity according to a semiempirical approach applied to a series of solvents. The whole dataset is classified into 6 and 24 clusters of solvatochromic sensitivity, from high negative to high positive solvatochromism. The results of the analysis are visualized by the polarity mapping plots depicting, in terms of wavenumbers, the absorption versus emission, stokes shift versus - (absorption maxima + emission maxima), and quantum yield versus stokes shift. An analysis of the clusters combining several dyes in an individual series of solvents shows that dyes of a high solvatochromic sensitivity demonstrate regular behaviour of the corresponding plots suitable for polarity and viscosity mapping. The fluorophores collected in this study represent a high quality dataset of pattern dyes for analytical and bioanalytical applications. The developed tools could be applied for the analysis of the applicability domain of the fluorescent sensors.

BODIPY-Labeled Estrogens for Fluorescence Analysis of Environmental Microbial Degradation

Biodegradation of estrogen hormone micropollutants is a well-established approach toward their remediation. Fluorescently labeled substrates are used extensively for rapid, near-real-time analysis of biological processes and are a potential tool for studying biodegradation processes faster and more efficiently than conventional approaches. However, it is important to understand how the fluorescently tagged surrogates compare with the natural substrate in terms of chemical analysis and the intended application. We derivatized three natural estrogens with BODIPY fluorophores by azide-alkyne cycloaddition click reaction and developed an analytical workflow based on simple liquid-liquid extraction and HPLC-PDA analysis. The developed methods allow for concurrent analysis of both fluorescent and natural estrogens with comparable recovery, accuracy, and precision. We then evaluated the use of BODIPY-labeled estrogens as surrogate substrates for studying biodegradation using a model bacterium for estrogen metabolism. The developed analytical methods were successfully employed to compare the biological transformation of 17β-estradiol (E2), with and without the BODIPY fluorescent tag. Through measuring the complete degradation of E2 and the transformation of BODIPY-estradiol to BODIPY-estrone in the presence of a co-substrate, we found that BODIPY-labeled estrogens are biologically viable surrogates for investigating biodegradation in environmental bacteria.

Exploring BODIPY-Based Sensor for Imaging of Intracellular Microviscosity in Human Breast Cancer Cells

BODIPY-based molecular rotors are highly attractive imaging tools for imaging intracellular microviscosity in living cells. In our study, we investigated the ability to detect the microviscosity of biological objects by using BDP-NO₂ and BDP-H molecular rotors. We describe in detail the optical properties of BDP-NO₂ and BDP-H molecular rotors in aqueous media with and without proteins, together with their accumulation dynamics and localization in live and fixed human breast cancer cells. Furthermore, we investigate the applicability of these molecules to monitor microviscosity in the organelles of human breast cancer cells by fluorescence lifetime imaging microscopy (FLIM). We demonstrate that the BDP-NO₂ molecular rotor aggregates in aqueous media and is incompatible with live cell imaging. The opposite effect is observed with BDP-H which preserves its stability in aqueous media, diffuses through the plasma membrane and accumulates in lipid droplets (LDs) and the cytosol of both live and fixed MCF-7 and MDA-MB-231 cancer cells. Finally, by utilizing BDP-H we demonstrate that LD microviscosity is significantly elevated in more malignant MDA-MB-231 human breast cancer cells, as compared to MCF-7 breast cancer cells. Our findings demonstrate that BDP-H is a water-compatible probe that can be successfully applied to measure microviscosity in the LDs of living cells.

Lessons in Organic Fluorescent Probe Discovery

Fluorescent probes have gained profound use in biotechnology, drug discovery, medical diagnostics, molecular and cell biology. The development of methods for the translation of fluorophores into fluorescent probes continues to be a robust field for medicinal chemists and chemical biologists, alike. Access to new experimental designs has enabled molecular diversification and led to the identification of new approaches to probe discovery. This review provides a synopsis of the recent lessons in modern fluorescent probe discovery.

A BODIPY-O-glycoside based near-infrared fluorescent sensor for serum albumin

Highly sensitive and selective near-infrared fluorescent bioprobes for serum albumin detection and quantification are in high demand for biomedical applications. Herein, we report a near-infrared emitting BODIPY-O-glycoside dye as a turn-on emission sensor for serum albumin. To the best of our knowledge, this is the first report of NIR-emitting BODIPY dyes for serum albumin sensing. Despite the various outstanding photophysical properties of the BODIPY dyes, their insolubility in water/biological media restricts their real biomedical applications. To overcome this issue, highly stable unadulterated BODIPY-O-glycoside nanoparticles (BDP-Glu-NPs) were prepared in aqueous solution by self-assembly of amphiphilic BODIPY-O-glycoside dyes. The BDP-Glu-NPs were characterized by spectroscopic, NMR, DLS and TEM studies. The ability of the BDP-Glu-NPs for the detection and quantification of serum albumin was demonstrated. It showed a 150-fold fluorescence enhancement in the presence of serum albumin, with excellent selectivity over other amino acids, porphyrin, proteins and various inorganic salts. Detection of human serum albumin (HSA) in urine samples showed that the bioprobe is applicable to a clinically significant range of the analytes with very low detection limit. These results suggested that the BDP-Glu-NPs can act as potential bioprobe to quantify albumin in biochemical and clinical samples.

Amphiphilic Near-IR-Emitting 3,5-Bis(2-Pyrrolylethenyl)BODIPY Derivatives: Synthesis, Characterization, and Comparison with Other (Hetero)Arylethenyl-Substituted BODIPYs

A series of 3,5-bis(hetero)arylethenyl-substituted BODIPY derivatives have been prepared by Knoevenagel-type condensation of alkyl-substituted BODIPY with the corresponding aldehydes. 2-Pyrrolylethenyl-substituted derivatives feature near-IR emission (λ_em > 700 nm) with a high fluorescence quantum yield. Both the emission maxima and fluorescence quantum yields are relatively insensitive to solvent polarity, contrary to the corresponding near-IR-emitting 4-(N,N-dimethylaminophenyl)ethenyl derivatives. Alkylation at the N-pyrrolic position of the ethenyl substituent allows for the installation of the hydrophilic PEG group and afforded amphiphilic BODIPY derivatives. Overall, 2-pyrrolylethenyl-substituted BODIPY derivatives appear to be versatile fluorophores with potential applications in near-IR imaging.

Tuning the optical properties of BODIPY dyes by N-rich heterocycle conjugation using a combined synthesis and computational approach

We report a systematic tuning of optical properties of BODIPY dyes by conjugation of nitrogen-rich heterocycles, and underlying nitrogen influence by TDDFT calculations.

Resolving Binding Events on the Multifunctional Human Serum Albumin

Physiological processes rely on initial recognition events between cellular components and other molecules or modalities. Biomolecules can have multiple sites or mode of interaction with other molecular entities, so that a resolution of the individual binding events in terms of spatial localization as well as association and dissociation kinetics is required for a meaningful description. Here we describe a trichromatic fluorescent binding- and displacement assay for simultaneous monitoring of three individual binding sites in the important transporter and binding protein human serum albumin. Independent investigations of binding events by X-ray crystallography and time-resolved dynamics measurements (switchSENSE technology) confirm the validity of the assay, the localization of binding sites and furthermore reveal conformational changes associated with ligand binding. The described assay system allows for the detailed characterization of albumin-binding drugs and is therefore well-suited for prediction of drug-drug and drug-food interactions. Moreover, conformational changes, usually associated with binding events, can also be analyzed.

Advances in the design of cell-permeable fluorescent probes for applications in live cell imaging

Advances in the design strategy of cell-permeable small fluorescent probes are discussed. Their applications in imaging specific cell types and intracellular bioanalytes, as well as the cellular environment in live conditions, are presented.

Chemical Modulation of in Vivo Macrophage Function with Subpopulation-Specific Fluorescent Prodrug Conjugates

Immunomodulatory agents represent one of the most promising strategies for enhancing tissue regeneration without the side effects of traditional drug-based therapies. Tissue repair depends largely on macrophages, making them ideal targets for proregenerative therapies. However, given the multiple roles of macrophages in tissue homeostasis, small molecule drugs must be only active in very specific subpopulations. In this work, we have developed the first prodrug-fluorophore conjugates able to discriminate closely related subpopulations of macrophages (i.e., proinflammatory M1 vs anti-inflammatory M2 macrophages), and employed them to deplete M1 macrophages in vivo without affecting other cell populations. Selective intracellular activation and drug release enabled simultaneous fluorescence cell tracking and ablation of M1 macrophages in vivo, with the concomitant rescue of a proregenerative phenotype. Ex vivo assays in human monocyte-derived macrophages validate the translational potential of this novel platform to develop chemical immunomodulatory agents as targeted therapies for immune-related diseases.

Design and synthesis of the BODIPY-BSA complex for biological applications

A quinoxaline-functionalized styryl-BODIPY derivative (S1) was synthesized by microwave-assisted Knoevenagel condensation. It exhibited fluorescence enhancement upon micro-encapsulation into the hydrophobic cavity of bovine serum albumin (BSA). The S1-BSA complex was characterized systematically using ultraviolet (UV)-visible absorption, fluorescence emission, kinetics, circular dichroism and time-resolved lifetime measurements. The binding nature of BSA towards S1 was strong, and was found to be stable over a period of days. The studies showed that the S1-BSA complex could be used as a new biomaterial for fluorescence-based high-throughput assay for kinase enzymes.

Novel cellulose-based halochromic test strips for naked-eye detection of alkaline vapors and analytes

A simple, portable and highly sensitive naked-eye test strip is successfully prepared for optical detection of gaseous and aqueous alkaline analytes. Novel pH-sensory tricyanofuran-hydrazone (TCFH) disperse colorant containing a hydrazone recognition functional moiety is successfully synthesized via azo-coupling reaction between active methyl-containing tricyanofuran (TCF) heterocycle and diazonium salt of 4-aminobenzaldehyde followed by Knoevenagel condensation with malononitrile. UV-vis absorption spectra display solvatochromism and reversible color changes of the TCFH solution in dimethyl sulfoxide in response to pH variations. We investigate the preparation of hydrophobic cellulose/polyethylene terephthalate composites characterized by their high affinity for disperse dyes. Composite films made from CA, Cell/CA, PET/CA, and Cell/PET-CA are produced via solvent-casting procedure using 10-30% modified cellulose or modified polyethylene terephthalate. The mechanical properties and morphologies of these composite films are investigated. The prepared pH-sensory hydrazone-based disperse dye is then applied to dye the produced cellulose-based composite films employing the high temperature pressure dyeing procedure. The produced halochromic PET-CA-TCFH test strip provide an instant visible signal from orange to purple upon exposure to alkaline conditions as proved by the coloration measurements. The sensor strip exhibits high sensitivity and quick detection toward ammonia in both of aqueous and vapor phases by naked-eye observations at room temperature and atmospheric pressure.

Solvatochromic fluorescent probes for recognition of human serum albumin in aqueous solution: Insights into structure-property relationship

Human serum albumin (HSA) as the most abundant protein in human blood plasma, serves many physiological functions. The dysregulation of HSA in serum or in urine is associated with various diseases, such as cirrhosis of liver, multiple myeloma, and cardiovascular disease. Therefore, to quantify HSA in body fluids with high selectivity and sensitivity is of great significance for disease diagnosis and preventive medicine. We herein developed a series of amide-functionalized flavonoids probes, 1-3, for recognition of human serum albumin. All flavonoids could be easily prepared by a Claisen-Schmidt condensation and Algar-Flynn-Oyamada reaction, and showed positive solvatochromism on their dual emissions. The chemical structure of flavonoids played an important role on their HSA-sensing abilities. Among three probes, the compound 1 showed the highest sensitivity, the remarkable selectivity, and the quantitive response for HSA in aqueous solution. Together with its high tolerance of environmental pH, anti-interference properties, and time-insensitivity, thus it provides a promising sensing method for HSA.

Molecular visualizing and quantifying immune-associated peroxynitrite fluxes in phagocytes and mouse inflammation model

Reactions of peroxynitrite (ONOO^-) with biomolecules can lead to cytotoxic and cytoprotective events. Due to the difficulty of directly and unambiguously measuring its levels, most of the beneficial effects associated with ONOO^- in vivo remain controversial or poorly characterized. Recently, optical imaging has served as a powerful noninvasive approach to studying ONOO^- in living systems. However, ratiometric probes for ONOO^- are currently lacking. Herein, we report the design, synthesis, and biological evaluation of F₄₈₂, a novel fluorescence indicator that relies on ONOO^--induced diene oxidation. The remarkable sensitivity, selectivity, and photostability of F₄₈₂ enabled us to visualize basal ONOO^- in immune-stimulated phagocyte cells and quantify its generation in phagosomes by high-throughput flow cytometry analysis. With the aid of in vivo ONOO^- imaging in a mouse inflammation model assisted by F₄₈₂, we envision that F₄₈₂ will find widespread applications in the study of the ONOO^- biology associated with physiological and pathological processes in vitro and in vivo.

New turn-on fluorescent and colorimetric probe for cyanide detection based on BODIPY-salicylaldehyde and its application in cell imaging

Development of cyanide sensor is important as the anion is harmful to human health and the environment. Herein, a new colorimetric and fluorescent probe GSB based on boron dipyrrole-methene (BODIPY) containing salicylaldehyde group for cyanide detection has been reported. GSB undergoes exclusive colorimetric change from orange to colorless and exhibits selective fluorescence turn-on at 504nm upon the addition of cyanide. Other 13 anions give almost no interference under physiological condition. Detection limit of the new cyanide-sensing GSB is 0.88μM, which is below World Health Organization (WHO) recommended level in drinking water. A calculation by density functional theory (DFT) shows suppression of photoinduced electron transfer (PET) mechanism along with the interruption of π-conjugation between salicylaldehyde and BODIPY core by cyanide anion. Cell imaging studies demonstrated that GSB is compatible and capable of sensing cyanide anion in living cells.

Development of background-free tame fluorescent probes for intracellular live cell imaging

Fluorescence labelling of an intracellular biomolecule in native living cells is a powerful strategy to achieve in-depth understanding of the biomolecule's roles and functions. Besides being nontoxic and specific, desirable labelling probes should be highly cell permeable without nonspecific interactions with other cellular components to warrant high signal-to-noise ratio. While it is critical, rational design for such probes is tricky. Here we report the first predictive model for cell permeable background-free probe development through optimized lipophilicity, water solubility and charged van der Waals surface area. The model was developed by utilizing high-throughput screening in combination with cheminformatics. We demonstrate its reliability by developing CO-1 and AzG-1, a cyclooctyne- and azide-containing BODIPY probe, respectively, which specifically label intracellular target organelles and engineered proteins with minimum background. The results provide an efficient strategy for development of background-free probes, referred to as ‘tame' probes, and novel tools for live cell intracellular imaging.

The success of a fluorescent dye as a molecular probe to monitor the intracellular activity of biomolecules depends on its physicochemical characteristics. Here, the authors use a predictive model to identify key features that allow them to design cell permeable, background-free fluorescent probes.

Interaction of BODIPY dyes with bovine serum albumin: a case study on the aggregation of a click-BODIPY dye

The fluorescence of BODIPY and click-BODIPY dyes was found to substantially increase in the presence of bovine serum albumin (BSA). BSA acted as a solubilizer for dye aggregates, in addition to being a conventional binding scaffold for the click-BODIPY dyes, indicating that disaggregation of fluorophores should be considered when evaluating dye-protein interactions.

A step toward simplified detection of serum albumin on SDS-PAGE using an environment-sensitive flavone sensor

In this study, we report a series of novel flavone-based sensors that exhibit a superior fluorescence response when interacting with serum albumin in real serum samples and in acrylamide gels. The detection limit of probe 4 for serum albumin solution is 0.09 μg mL(-1), and the detectable volume for monkey serum reaches as low as 0.03 μL.

Interaction of BODIPY Dyes with the Blood Plasma Proteins

Photophysical properties of several BODIPY-based fluorescent dyes were investigated in systems containing blood plasma biomolecules and in model system containing bovine serum albumin in terms of electronic absorption and fluorescence spectroscopy. The interaction between the investigated dyes and protein plasma components changes spectral characteristics of the dyes and leads to bathochromic and hypochromic absorption spectra shifts accompanied by changing of fluorescence intensity. The mechanism of fluorescence changing was defined in the terms of Stern-Volmer theory. It was shown that the static factor of molecular dye-biopolymers complex formation prevails at plasma protein concentration up to 1 g/l, while the higher viscosity range is characterized mainly by nonspecific fluorophore interactions. The increase of fluorescent characteristics of phenyl-substituted BODIPY in the presence of proteins caused by resonance energy transfer and change of physicochemical properties of the molecular environment of the fluorophore was shown for the first time.

Boron-containing compounds: chemico-biological properties and expanding medicinal potential in prevention, diagnosis and therapy

INTRODUCTION

Although the medicinal use of boron-containing compounds (BCCs) had long been limited to antiseptics, in the last few decades, these compounds have been used as antibiotics or chemotherapeutic agents. In the last few years, boron has been included in the moieties of many known drugs to improve their capacity in binding to their respective target receptors.

AREAS COVERED

The current review focuses on research and patent literature of the last decade related to the development of BCCs as preventive, diagnostic and therapeutic tools. It explores the possible mechanisms of action of these compounds as well as the advantageous features of their structure and chemico-pharmacological properties.

EXPERT OPINION

Although uncertainties exist about the mechanism of action of BCCs, increasing evidence about their toxicological profile strongly suggests that many can be safely administered to humans. Even stronger evidence exists regarding the capacity of BCCs to reach multiple targets that are involved in the treatment of common diseases. It seems fair to say that some BCCs will reach the market for medicinal use in the near future, not only for targeting microbial or neoplastic systems but also for acting on cell-signaling processes involved in many other disorders.

Multicomponent reactions for de novo synthesis of BODIPY probes: in vivo imaging of phagocytic macrophages

Multicomponent reactions are excellent tools to generate complex structures with broad chemical diversity and fluorescent properties. Herein we describe the adaptation of the fluorescent BODIPY scaffold to multicomponent reaction chemistry with the synthesis of BODIPY adducts with high fluorescence quantum yields and good cell permeability. From this library we identified one BODIPY derivative (PhagoGreen) as a low-pH sensing fluorescent probe that enabled imaging of phagosomal acidification in activated macrophages. The fluorescence emission of PhagoGreen was proportional to the degree of activation of macrophages and could be specifically blocked by bafilomycin A, an inhibitor of phagosomal acidification. PhagoGreen does not impair the normal functions of macrophages and can be used to image phagocytic macrophages in vivo.

Identification of cancer cell-line origins using fluorescence image-based phenomic screening

Universal phenotyping techniques that can discriminate among various states of biological systems have great potential. We applied 557 fluorescent library compounds to NCI's 60 human cancer cell-lines (NCI-60) to generate a systematic fluorescence phenotypic profiling data. By the kinetic fluorescence intensity analysis, we successfully discriminated the organ origin of all the 60 cell-lines.

Synthesis of a novel BODIPY library and its application in the discovery of a fructose sensor

We prepared a new library of 160 compounds by conjugation of a BODIPY core to a collection of aldehydes. This library was screened against 52 biologically relevant analytes and we identified one fluorescent sensor of fructose (Fructose Orange). Fructose Orange showed a 24-fold fluorescence increase upon recognition of fructose and an outstanding selectivity among 24 different saccharides. NMR studies confirmed that five different binding interactions were formed between the sensor and fructose. Furthermore, Fructose Orange was applied to the quantification of fructose in soft drinks, being the most selective fluorescent sensor for fructose reported to date.

Synthesis of pH-activatable red fluorescent BODIPY dyes with distinct functionalities

A series of tunable pH-dependent BODIPY dyes were synthesized and further functionalized in a Knoevenagel condensation reaction with various aldehydes. In this fashion, monofunctional dyes containing an alkyne, azide, or carboxylic acid (masked as its methyl ester) as ligation sites as well as asymmetrical bifunctional dyes were obtained, without compromising their pH-dependency. In addition, fluorescence excitation and emission maxima for these dyes were shown to be significantly red-shifted in comparison to their tetramethyl precursors.

Solid-phase synthesis of BODIPY dyes and development of an immunoglobulin fluorescent sensor

The diversification of the BODIPY scaffold has been hindered by its controversial adaptability to solid-phase chemistry. Herein we report the first solid-phase synthesis of a BODIPY library in high purities. We screened the library against a set of proteins, identified an immunoglobulin fluorescent sensor (Ig Orange) and confirmed its binding by SPR experiments.