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Organic nanomaterials, as nanocarrier platforms, have tremendous potential for biomedical applications. The authors successfully prepared novel two‐dimensional covalent organic nanosheets (CONs) that can be used as efficient in vivo bioimaging probes by condensing 1,3,5‐triformylglucinol (Tp) and 2,7‐diaminopyrene (Py) to produce TpPy covalent organic frameworks (COFs). TpPy COFs are then subjected to a liquid exfoliation process to obtain TpPy CONs (< 200 nm in size and < 1.7 nm in thickness). TpPy CONs disperse well in water to provide a stable, homogeneous colloidal suspension, which shows favorable photoluminescence properties. Cell viability tests using MDA‐MB‐231 and RAW 264.7 cells reveal that TpPy CONs are low in cytotoxicity. Confocal microscopy reveals clear fluorescent cell images after incubation with TpPy CONs for 24 h, without reduction in cell activity or cytosolic aggregation. To investigate the biological behavior of the TpPy CONs, the authors perform an in vivo fluorescence imaging study using MDA‐MB‐231 tumor‐bearing mice. After intravenous injection of TpPy CONs disperse in phosphate‐buffered saline (PBS), persistent and strong fluorescence signals are observed in the tumor region, with low background signals from normal tissues at 1, 3, 12, and 24 h after injection. Furthermore, these in vivo imaging results concurred with ex vivo biodistribution and histological results. [ABSTRACT FROM AUTHOR]

Transforming carbon dots (CDs) fluorescent materials into smart materials with complex functions is a topic of great interest to nanoscience. However, designing CDs with regulating fluorescence/phosphorescence that can be visually monitored with the environment changes in real‐time remains a challenge. Here, a very simple strategy, one‐step solvent‐free catalytic assistant strategy, which is low cost, facile, environment‐friendly, and high throughput, is put forward. Hydrogen bond is used to manipulate nanostructure of CDs, and the obtained carbon dots (M‐CDs) show a series of attractive properties including matrix‐free room‐temperature phosphorescence, time‐dependent fluorescence, and near‐infrared emissive characteristics. Different from the traditional aggregation caused quenching or aggregation‐induced emission fluorescent materials, M‐CDs exhibit unprecedented and unique dispersion induced redshift fluorescence phenomenon, promoting the studies of fluorescence from static to dynamic. The causes of this phenomenon are further analyzed in detail. As a kind of intelligent fluorescent materials, this new designed CDs greatly enrich the basic recognition of CDs by illustrating the relationship between redshift fluorescence behaviors and the dispersion states, and may provide with an opportunity for solid‐state fluorescent materials, anti‐counterfeiting, cellular imaging, and hopefully many others. [ABSTRACT FROM AUTHOR]

Transforming carbon dots (CDs) fluorescent materials into smart materials with complex functions is a topic of great interest to nanoscience. However, designing CDs with regulating fluorescence/phosphorescence that can be visually monitored with the environment changes in real‐time remains a challenge. Here, a very simple strategy, one‐step solvent‐free catalytic assistant strategy, which is low cost, facile, environment‐friendly, and high throughput, is put forward. Hydrogen bond is used to manipulate nanostructure of CDs, and the obtained carbon dots (M‐CDs) show a series of attractive properties including matrix‐free room‐temperature phosphorescence, time‐dependent fluorescence, and near‐infrared emissive characteristics. Different from the traditional aggregation caused quenching or aggregation‐induced emission fluorescent materials, M‐CDs exhibit unprecedented and unique dispersion induced redshift fluorescence phenomenon, promoting the studies of fluorescence from static to dynamic. The causes of this phenomenon are further analyzed in detail. As a kind of intelligent fluorescent materials, this new designed CDs greatly enrich the basic recognition of CDs by illustrating the relationship between redshift fluorescence behaviors and the dispersion states, and may provide with an opportunity for solid‐state fluorescent materials, anti‐counterfeiting, cellular imaging, and hopefully many others. [ABSTRACT FROM AUTHOR]

A lipid droplet (LD) core of a cell consists mainly of neutral lipids, triacylglycerols and/or steryl esters (SEs). The structuration of these lipids inside the core is still under debate. Lipid segregation inside LDs has been observed but is sometimes suggested to be an artefact of LD isolation and chemical fixation. LD imaging in their native state and in unaltered cellular environments appears essential to overcome these possible technical pitfalls. Here, imaging techniques for ultrastructural study of native LDs in cellulo are provided and it is shown that LDs are organized structures. Cryo soft X‐ray tomography and deep‐ultraviolet (DUV) transmittance imaging are showing a partitioning of SEs at the periphery of the LD core. Furthermore, DUV transmittance and tryptophan/tyrosine auto‐fluorescence imaging on living cells are combined to obtain complementary information on cell chemical contents. This multimodal approach paves the way for a new label‐free organelle imaging technique in living cells. [ABSTRACT FROM AUTHOR]

Saccharomyces cerevisiae is a well-established model organism to study the mechanisms of longevity. One of the two aging paradigms studied in yeast is termed chronological lifespan ( CLS). CLS is defined by the amount of time non-dividing yeast cells can survive at stationary phase. Here, we propose new approaches that allow rapid and efficient quantification of survival rates in aging yeast cultures using either a fluorescent cell counter or microplate imaging. We have generated a software called analysr ( Analytical Algorithm for Yeast Survival Rates) that allows automated and highly reproducible analysis of cell survival in aging yeast cultures using fluorescent data. To demonstrate the efficiency of our new experimental tools, we tested the previously characterized ability of caloric restriction to extend lifespan. Interestingly, we found that this process is independent of the expression of three central yeast heat shock proteins (Hsp26, Hsp42, Hsp104). Finally, our new assay is easily adaptable to other types of toxicity studies. Here, we assessed the toxicity of various concentrations of acetic acid, a known contributor of yeast chronological aging. These assays provide researchers with cost-effective, low- and high-content assays that can serve as an efficient complement to the time-consuming colony forming unit assay usually used in CLS studies. [ABSTRACT FROM AUTHOR]

A quinoline-thiooxorhodamine conjugate fluorescent sensor (1) has been synthesized. Sensor 1 exhibits high selectivity and sensitivity to Hg2+ in H2O/DMSO (95/5, v/v, HEPES 20 mM, pH = 7.4) solution with fluorescence detection. Other tested metal ions do not induce any significant fluorescence intensity changes. Sensor 1 interacts with Hg2+ through a 1:1 binding stoichiometry with a good anti-inference ability. In addition, fluorescent imaging of Hg2+ in Hela cells is also successfully demonstrated. [ABSTRACT FROM AUTHOR]

Development of biocompatible multifunctional nanocarriers is necessary for the success of theranostics. Here, we report a novel hybrid nanorod with self-fluorescent property, high drug loading capacity, and good biocompatibility. Fluorescent hydroxyapatite (fHA) nanorod was ensheathed with mesoporous silica (mSi). The mSi shell was uniformly layered and was tunable in thickness (10-30 nm) over the fHA nanorod. Highly mesoporous structure of mSi shell facilitated the loading of a large quantity of biological molecules, as confirmed with fluorescein isothiocynate; ~1% loading for fHA increased to ~10% loading for fHA@mSi. The self-fluorescent property of the fHA resulting from CO2⋅- radicals was well preserved in the fHA@mSi hybrid, as analyzed by photoluminescence and electron paramagnetic resonance property. Cellular toxicity of the fHA@mSi hybrid nanorod showed favorable cell viability (>90% viability of control) up to a concentration of ~40 µg/mL. Intracellular uptake rate of the hybrid nanorod was as high as 80-90%, as analyzed by fluorescent-assisted cell sorter. Results demonstrate the newly developed fHA@mSi nanocarriers have great potential for the effective loading of therapeutic molecules and delivery within intracellular compartments in concert with a capacity for in situ imaging. [ABSTRACT FROM AUTHOR]

Red/near‐infrared (NIR) emissive carbon nanodots (CNDs) with photoluminescence (PL) quantum yield (QY) of 57% are prepared via an in situ solvent‐free carbonization strategy for the first time. 1‐Photon and 2‐photon cellular imaging is demonstrated by using the CNDs as red/NIR fluorescence agent due to the high PL QY and low biotoxicity. Further study shows that the red/NIR CNDs exhibit multiphoton excited (MPE) upconversion fluorescence under excitation of 800–2000 nm, which involves three NIR windows (NIR‐I, 650–950 nm; NIR‐II, 1100–1350; NIR‐III, 1600–1870 nm). 2‐Photon, 3‐photon, and 4‐photon excited fluorescence of the CNDs under excitation of different wavelengths is achieved. This study develops an in situ solvent‐free carbonization method for efficient red/NIR emissive CNDs with MPE upconversion fluorescence, which may push forward the application of the CNDs in bioimaging. [ABSTRACT FROM AUTHOR]

Fluorogenic labeling enables imaging cellular molecules of interest with minimal background. This process is accompanied with the notable increase of the quantum yield of fluorophore, thus minimizing the background signals from unactivated profluorophores. Herein, the development of a highly efficient and bioorthogonal nitroso‐based Diels–Alder fluorogenic reaction is presented and its usefulness is validated as effective and controllable in fluorescent probes and live‐cell labeling strategies for dynamic cellular imaging. It is demonstrated that nitroso‐based cycloaddition is an efficient fluorogenic labeling tool through experiments of further UV‐activatable fluorescent labeling on proteins and live cells. The ability of tuning the fluorescence of labeled proteins by UV‐irradiation enables selective activation of proteins of interest in a particular cell compartment at a given time point, while leaving the remaining labeled molecules untouched. [ABSTRACT FROM AUTHOR]