A Nano-Aggregatable Acedan Derivative for Clathrin-Mediated Cellular Uptake and Two-Photon Imaging of Diabetes-Associated Lipid Droplets.

Lipid droplets (LDs), the essential cytosolic fat storage organelles, have emerged as pivotal regulators of cellular metabolism and are implicated in various diseases. The noninvasive monitoring of LDs necessitates fluorescent probes with precise organelle selectivity and biocompatibility. Addressing this need, we have engineered a probe by strategically modifying the structure of a conventional two-photon-absorbing dipolar dye, acedan.

Development of photo- and chemo-stable near-infrared-emitting dyes: linear-shape benzo-rosol and its derivatives as unique ratiometric bioimaging platforms.

Microscopic imaging aided with fluorescent probes has revolutionized our understanding of biological systems. Organic fluorophores and probes thus continue to evolve for bioimaging applications. Fluorophores such as cyanines and hemicyanines emit in the near-infrared (NIR) region and thus allow deeper imaging with minimal autofluorescence; however, they show limited photo- and chemo-stability, demanding new robust NIR fluorophores.

NAD(P)H Quinone Oxidoreductase-1 in Organ and Tumor Tissues: Distinct Activity Levels Observed with a Benzo-rosol-Based Dual-Excitation and Dual-Emission Probe.

NAD(P)H quinone oxidoreductase-1 (NQO1), a protective enzyme against cellular oxidative stress, is expressed abnormally high in solid tumors and thus recognized as a cancer biomarker. To develop a fluorescent NQO1 probe with practicality, we investigated benzo-rosol fluorophores linked with a known self-immolative quinone substrate. Four probe candidates exhibited ratiometric sensing behavior toward the enzyme, satisfying our orbital mismatch stratagem proposed before, under dual-excitation and dual-emission conditions that alleviate the spectral overlap issue commonly observed with the ratiometric probes based on intramolecular charge-transfer change.

A caveat to common hemicyanine dye components and their resolution.

Near-infrared-emitting hemicyanine dyes are widely used in activatable fluorescent probes for various biological analytes; however, they are chemically unstable and show photoinstability, as shown here with naphthalene-based hemicyanines containing a typical hemicyanine moiety, 2-indolium. These issues can be resolved with a 4-pyridinium derivative, which also has good two-photon imaging capability.

Synthesis of Near-Infrared-Emitting Benzorhodamines and Their Applications to Bioimaging and Photothermal Therapy.

Photostable and near-infrared (NIR)-emitting organic fluorophores with large Stokes shifts are in great demand for long-term bioimaging at deeper depths with minimal autofluorescence and self-quenching. Herein, a new class of benzorhodamines and their analogues that are photostable and emit in the NIR region (up to 785 nm) with large Stokes shifts (>120 nm) is reported. The synthesis involves condensation of 7-alkylamino-2-naphthols with 2-[4-(dimethylamino)-2-hydroxybenzoyl]benzoic acid, which leads to bent-shaped benzorhodamines that emit orange fluorescence (≈600 nm); however, introduction of steric hindrance near the condensation site switched the regioselectivity, to provide a linear benzorhodamine system for the first time.

A Benzopyronin-Based Two-Photon Fluorescent Probe for Ratiometric Imaging of Lysosomal Bisulfite with Complete Spectral Separation.

Bisulfite (HSO), which equilibrates with sulfite (SO) and sulfur dioxide (SO) in aqueous media, can be produced endogenously during oxidation of hydrogen sulfide or sulfur-containing amino acids. Lysosomes, known as the scavengers of living cells, play a crucial role in the metabolic process, and bisulfite is often produced inside the lysosomes. Therefore, detection of bisulfite in lysosomes is a subject of significant interest.