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In vivo blood vessels imaging is crucial to study blood vessels related diseases in real-time. For this purpose, fluorescent based imaging is one of the utmost techniques for imaging a living system. The discovery of a new near-infrared probe (CyA-B2) by screening chemical probe library in our previous report which showed the most specific binding on the blood capillaries of the 3D-tissue models give us interest to study more about the binding site of this probe to the surface of endothelial cells main component cell of blood capillaries. By studying the competition assays of CyA-B2 using several potential surface markers of endothelial cells found through the chemical database (ChEMBL) and manually selected, CD133 gave the lowest IC50 (half maximal inhibitory concentration) value. Hence, CD133 protein which is expressed on the endothelial cell membrane was postulated to be the binding site due to the suppression of CyA-B2 on the blood capillaries by the competition assays. Since, CD133 is also expressed on many types of cancer cells, it would be useful to use CyA-B2 as a bioprobe to monitor or diagnostic tumor growth.

The development of organelle-specific fluorescent probes has been impeded by the absence of a comprehensive understanding of the relationship between the physicochemical properties of fluorescent probes and their selectivity towards specific organelles. Although a few machine learning models have suggested several physicochemical parameters that control the target organelle of the probes and have attempted to predict the target organelles, they have been challenged by low accuracy and a limited range of applicable organelles. Herein, we report a multi-organelle prediction QSAR model that is capable of predicting the destination of probes among nine categories, including cytosol, endoplasmic reticulum, Golgi body, lipid droplet, lysosome, mitochondria, nucleus, plasma membrane, and no entry. The model is trained using the Random Forest algorithm with a dataset of 350 organelle-specific fluorescent probes and 786 descriptors, and it is able to predict the target organelles of fluorescent probes with an accuracy of 75%. The MDI analysis of the model identifies 38 key parameters that have a significant impact on the organelle selectivity of the probes, including LogD, pKa, hydrophilic-lipophilic balance (HLB), and topological polar surface area (TPSA). This prediction model may be useful in developing new organelle-specific fluorescent probes by providing crucial variables that determine the destination of the probes.

The identification of T and B lymphocytes has relied on using antibodies against different biomarkers as the gold standard. Emerging small molecule-based fluorescent probes have the potential to replace antibodies. Herein, we report the first human-T-cell-selective fluorescent probe, Mito thermo yellow (MTY), achieving the live T cells’ distinction from B cells, which was previously impossible without the help of antibodies. The unexpected cell selectivity of MTY is attributed to the higher mitochondria mass and membrane potential of T cells over B cells. This study enriches the toolbox for live cell distinction from complex cell communities.

Intracellular viscosity is a fundamental physical parameter that indicates the functioning of cells. In this work, we developed a simple boron-dipyrromethene (BODIPY)-based probe, BTV, for cellular mitochondria viscosity imaging by coupling a simple BODIPY rotor with a mitochondria-targeting unit. The BTV exhibited a significant fluorescence intensity enhancement of more than 100-fold as the solvent viscosity increased. Also, the probe showed a direct linear relationship between the fluorescence lifetime and the media viscosity, which makes it possible to trace the change of the medium viscosity. Furthermore, it was demonstrated that BTV could achieve practical applicability in the monitoring of mitochondrial viscosity changes in live cells through fluorescence lifetime imaging microscopy (FLIM).

We report the development of a small fluorescent molecule, BDNCA3-D2, herein referred to as PT-Yellow. Soaking zebrafish embryos in PT-Yellow or intraperitoneal injection into adults results in non-toxic in vivo fluorescent labeling of the renal proximal tubules, the major site of blood filtrate reabsorption and a common target of injury in acute kidney injury. We demonstrate the applicability of this new compound as a rapid and simple readout for zebrafish kidney filtration and proximal tubule reabsorption function. [ABSTRACT FROM AUTHOR]

Screening of bead-based peptide libraries against fluorescent dyelabeled target proteins was found to be significantly influenced by the dye characteristics. Commercially available red fluorescent dyes with net negative charges adversely showed strong interactions with library beads. The introduction of zwitterionic dyes significantly reduced the unwanted interactions, which sheds light upon using the right fluorescent probe for acquisition of reliable results in various fluorescence-assisted applications. [ABSTRACT FROM AUTHOR]

The dynamics of cellular heat production and propagation remains elusive at a subcellular level. Here we report the first small molecule fluorescent thermometer selectively targeting the endoplasmic reticulum (ER thermo yellow), with the highest sensitivity reported so far (3.9%/°C). Unlike nanoparticle thermometers, ER thermo yellow stains the target organelle evenly without the commonly encountered problem of aggregation, and successfully demonstrates the ability to monitor intracellular temperature gradients generated by external heat sources in various cell types. We further confirm the ability of ER thermo yellow to monitor heat production by intracellular Ca2+ changes in HeLa cells. Our thermometer anchored at nearly-zero distance from the ER, i.e. the heat source, allowed the detection of the heat as it readily dissipated, and revealed the dynamics of heat production in real time at a subcellular level. [ABSTRACT FROM AUTHOR]

''Aggregation-caused signal change'' is a well-established mechanism by now and has been widely used as the basis for optical probe and sensor development. Compared to aggregation, its reverse process, disaggregation, has received much less attention and is not properly discussed in the literature so far. With the less established paradigm or mechanism, although some of the reported sensors and probes seem to work through disaggregation phenomena, the proper interpretation of the results and applying the concept to novel probe development is seriously hampered. The process from aggregation to disaggregation generally causes a recovery or enhancement of fluorescence signals, and thus provides an interesting new path to design ''turn-on'' probes. This tutorial review will provide the balanced comparison between aggregation and disaggregation mechanism, and focuses on the less explored advantages of ''disaggregation'' as a novel sensing mechanism and its recent applications in probe development. [ABSTRACT FROM AUTHOR]

The development of a fluorescent probe capable of detecting and distinguishing the wide diversity of G-quadruplex structures is particularly challenging. Herein, we report a novel BODIPY-based fluorescent sensor (GQR) that shows unprecedented selectivity to parallel-stranded G-quadruplexes with exposed ends and four medium grooves. Mechanistic studies suggest that GQR associates with G-quadruplex grooves close to the end of the tetrad core, which may explain the dye's specificity to only a subset of parallel structures. This specific recognition favours the disaggregation of GQR in aqueous solutions thereby recovering the inherent fluorescence of the dye. Due to its unique features, GQR represents a valuable tool for basic biological research and the rapid discovery of novel, specific ligands that target similar structural features of G-quadruplexes [ABSTRACT FROM AUTHOR]

Fluorescent small molecules have become indispensable tools for biomedical research along with the rapidly developing optical imaging technology. We report here a neural stem cell specific borondipyrromethane (BODIPY) derivative compound of designation red 3 (CDr3), developed through a high throughput/content screening of in-house generated diversity oriented fluorescence library in stem cells at different developmental stages. This novel compound specifically detects living neural stem cells of both human and mouse origin. Furthermore, we identified its binding target by proteomic analysis as fatty acid binding protein 7 (FABP7), also known as brain lipid binding protein) which is highly expressed in neural stem cells and localized in the cytoplasm. CDr3 will be a valuable chemical tool in the study and applications of neural stem cells. [ABSTRACT FROM AUTHOR]

We report here a novel fluorescent chemical probe CDy5 which stains distinct neural stem/progenitor cells (NSPCs) by binding to acid ceramidase in mouse neurospheres. CDy5 is distributed evenly or unevenly to the daughter cells during multiple mitoses enabling the live imaging of symmetric and asymmetric divisions of isolated NSPCs. [ABSTRACT FROM AUTHOR]

Visualization of macrophages in live animals has been of great interest for a better understanding of inflammation. We developed a near infrared (NIR) probe CDnir7 that can selectively detect macrophages and visualize inflammation in vivo using the IVIS spectrum, Fluorescence Molecular Tomography (FMT) and Multi-Spectral Optoacoustic Tomography (MSOT). [ABSTRACT FROM AUTHOR]

The article describes the first combinatorial synthesis of a rosamine library and its use as a fluorescent probe for monitoring the cellular concentration of glutathione. Solid-phase chemistry was incorporated to generate the final product rosamine. Initially, three different 3-amino-6-nitro-9H-xanthone derivatives were synthesized. The library compounds were screened for fluorescence intensity change toward a variety of biorelevant analytes.

Bacterial biofilms are responsible for a wide range of persistent infections. In the clinic, diagnosis of biofilm-associated infections relies heavily on culturing methods, which fail to detect nonculturable bacteria. Identification of novel fluorescent probes for biofilm imaging will greatly facilitate diagnosis of pathogenic bacterial infection. Herein, we report a novel fluorescent probe, CDy11 (compound of designation yellow 11), which targets amyloid in the Pseudomonas aeruginosa biofilm matrix through a diversity oriented fluorescent library approach (DOFLA). CDy11 was further demonstrated for in vivo imaging of P. aeruginosa in implant and corneal infection mice models. [ABSTRACT FROM AUTHOR]

Aggregation of amyloid β-peptide (Aβ) is implicated in the pathology of Alzheimer's disease (AD), with the soluble, Aβ oligomeric species thought to be the critical pathological species. Identification and characterization of intermediate species formed during the aggregation process is crucial to the understanding of the mechanisms by which oligomeric species mediate neuronal toxicity and following disease progression. Probing these species proved to be extremely challenging, as evident by the lack of reliable sensors, due to their heterogeneous and transient nature. We describe here an oligomer-specific fluorescent chemical probe, BoDipy-Oligomer (BD-Oligo), developed through the use of the diversity-oriented fluorescent library approach (DOFLA) and high-content, imaging-based screening. This probe enables dynamic oligomer monitoring during fibrillogenesis in vitro and shows in vivo Aβ oligomers staining possibility in the AD mice model. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCI), as a highly potent oxidant, is well-known as a key "killer" for pathogens in the innate immune system. Recently, mounting evidence indicates that intracellular HOCI plays additional important roles in regulating inflammation and cellular apoptosis. However, the organelle (s) involved in the distribution of HOCI remain unknown, causing difficulty to fully exploit its biological functions in cellular signaling pathways and various diseases. One of the main reasons lies in the lack of effective chemical tools to directly detect HOCI at subcellular levels due to low concentration, strong oxidization, and short lifetime of HOCI. Herein, the first two-photon fluorescent HOCI probe (TP-HOCl 1) and its mitochondria- (MITO-TP) and lysosome- (LYSO-TP) targetable derivatives for imaging mitochondrial and lysosomal HOCI were reported. These probes exhibit fast response (within seconds), good selectivity, and high sensitivity (<20 nM) toward HOCI. In live cell experiments, both probes MITO-TP and LYSO-TP were successfully applied to detect intracellular HOCI in corresponding organelles. In particular, the two-photon imaging of MITO-TP and LYSO-TP in murine model shows that higher amount of HOCI can be detected in both lysosome and mitochondria of macrophage cells during inflammation condition. Thus, these probes could not only help clarify the distribution of subcellular HOCI, but also serve as excellent tools to exploit and elucidate functions of HOCI at subcellular levels. [ABSTRACT FROM AUTHOR]

Successful identification of nodal metastases in patients with cancer is crucial to prescribe suitable treatment regimens that can improve recurrence-free survival. Although some new imaging technologies for nodal staging have been developed, such as nanoparticle-enhanced MRI and quantum-dot--based fluorescence imaging, sound technologies for intraoperative differentiation of metastatic and inflamed lymph nodes remain lacking. In this study, we illustrate the feasibility of using a macrophage-specific fluorescent probe (MFP) to visualize sentinel lymph nodes during surgery, highlighting abnormalities related to inflammation and tumor infiltration with signal enhancement and reduction methods using this technology. MFP was identified by high-throughput screening of fluorescent small-molecule libraries synthesized with a diversity-oriented approach. It selectively visualized monocyte and macrophage cell populations in vitro, by live-cell imaging and flow cytometry, as well as in vivo, for imaging-guided surgery. Collectively, this study provides preclinical proof of concept for an intraoperative imaging platform to accurately assess lymph node status, eliminating the need for invasive nodal dissections that can contribute to complications of cancer therapy. [ABSTRACT FROM AUTHOR]

A focused fluorescent probe library for metal cations was developed by combining metal chelators and picolinium/quinolinium moieties as combinatorial blocks connected through a styryl group. Furthermore, metal complexes derived from metal chelators having high binding affinities for metal cations were used to construct a focused probe library for phosphorylated biomolecules. More than 250 fluorescent probes were screened for identifying an ultraselective probe for dTTP. [ABSTRACT FROM AUTHOR]

The article discusses the combinatorial strategies in the development of fluorescent probe. It states that the combinatorial approaches which were first exploited in drug discovery to gain structurally related drug candidates have boosted the optimization and generation of fluorescent probe. It says that the combinatorial strategies have widened the scope of fluorescent probes to targets which were not accessible including cell differentiation stages, cell phenotypes, and macrostructures.

A correction to the article "Focused Fluorescent Probe Library for Metal Cations and Biological Anions" that was published in the previous issue is presented.