Deep-Red and Near-Infrared Xanthene Dyes for Rapid Live Cell Imaging

In this work, two xanthene dyes (<b>H-hNR</b> and <b>TF-hNR</b>) have been synthesized by a convenient and efficient method. These two dyes exhibited deep-red and near-infrared emissions, high fluorescence quantum yields, and good photostability. Their structure–optical properties were investigated by X-ray crystal structure analysis and density functional theory calculations. Live cell imaging data revealed that <b>H-hNR</b> and <b>TF-hNR</b> could rapidly stain both A549 and HeLa cells with low concentrations. The excellent photophysical and imaging properties render them as promising candidates for use in live cell imaging

Deep-Red Emissive Crescent-Shaped Fluorescent Dyes: Substituent Effect on Live Cell Imaging

A series of crescent-shaped fluorescent dyes (<b>CP1</b>–<b>CP6</b>) were synthesized by hybridizing coumarin and pyronin moieties with different amino substituents at both ends. The molecular structures and photophysical properties of these fluorescent dyes were investigated through X-ray diffraction, absorption spectroscopy, and fluorescence spectroscopy. Results show that the fluorescent dyes exhibited crescent-shaped structures, deep-red emissions (approximately 650 nm), and significant Stokes shifts. In live-cell-imaging experiments, <b>CP1</b> stains mitochondria, whereas <b>CP3</b> and <b>CP6</b> stain the lysosomes in a cytoplasm and the RNA in nucleoli. The relationships between different amino substituent groups and the imaging properties of <b>CP</b> dyes were discussed as well. Additionally, findings from the cytotoxicity and photostability experiments on living cells indicated the favorable biocompatibility and high photostability of the <b>CP</b> dyes

Facile Method for Modification of the Silicon Nanowires and Its Application in Fabrication of pH-Sensitive Chips

A novel, facile, and effective method for modification of SiNWs or SiNW arrays has been developed. In this method, reaction between reductive Si–H bonds on the surface of SiNWs and the aldehyde group containing in organic molecules has been used for immobilization of organic molecules onto the surface of SiNW arrays. The method is time saving and can be operated at room temperature without any other complex reaction requirement. Fluorescence images, XPS, fluorescence spectra, and IR spectra were used for characterization of the modification. Through this method, a SiNW array-based pH sensitive chip was realized by covalently immobilizing 5-aminofluorescein molecules onto the surface of SiNW arrays with glutaraldehyde as linker molecules. Fluorescence intensity of the chip increased with increasing of pH value and a linear relationship between fluorescence intensity and pH values was acquired. In addition, the chip has been successfully used for real-time and in situ monitoring of extracellular pH changes for live HeLa cells and the result exhibited fine resolution of time and space

Coumarin- and Rhodamine-Fused Deep Red Fluorescent Dyes: Synthesis, Photophysical Properties, and Bioimaging in Vitro

A series of deep red fluorescent dyes (<b>CR1</b> to <b>CR3</b>) was developed via introduction of a coumarin moiety into the rhodamine molecular skeleton. The novel dyes possessed the individual advantages of coumarin and rhodamine derivatives, and the emission wavelength was extended to the deep red region (>650 nm) due to the extension of fused-ring conjugate structure simultaneously. To illustrate its value, we designed and conveniently synthesized a series of novel deep red bioimaging dyes (<b>CR1E</b> to <b>CR3E</b>) by esterification of <b>CR1</b> to <b>CR3</b>, which could selectively stain mitochondria. They were superior to the MitoTrackers for mitochondrial staining in terms of large Stokes shift, excellent contrast for imaging, high photostability, and low cytotoxicity. Furthermore, the fluorescence of the coumarin moiety and rhodamine-like fluorophore could be switched like classical rhodamine. Thus, they could be used as an effective platform in constructing fluorescence sensors. Based on this fact, we constructed a novel ratiometric sensor (<b>CR1S</b>) for Hg²⁺ with good selectivity that could be successfully applied to the imaging of Hg²⁺ in living A549 cells. This design strategy is straightforward and adaptable to various deep red dyes and sensing platforms by simply introducing different fluorophores

Aminobenzofuran-Fused Rhodamine Dyes with Deep-Red to Near-Infrared Emission for Biological Applications

Aminobenzofuran-fused rhodamine dyes (<b>AFR</b> dyes) containing an amino group were constructed by an efficient condensation based on 3-coumaranone derivatives. <b>AFR</b> dyes exhibited significantly improved properties, including deep-red and near-infrared emissions, a large Stokes shift, good photostability, and wide pH stability. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2<i>H</i>-tetrazolium assay experiments show that these <b>AFR</b> dyes are biocompatible for their low cytotoxicity to both A549 and HeLa cells. Cell imaging data reveal that <b>AFR1</b>, <b>AFR1E</b>, and <b>AFR2</b> are mainly located in the mitochondria, while <b>AFR3</b> is a lysosome tracker. As far as we know, NIR <b>AFR3</b> is the longest fluorescent rhodamine derivative containing the amino group. These amino group-containing <b>AFR</b> dyes hold great potential in fluorogenic detection, biomolecule labeling, and cell imaging