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The conveniently obtained water-soluble small-molecule L1–5 were selective for RNA with remarkable “off–on” two-photon fluorescence responses in vitro and in vivo, showing that L1–5 can surprisingly stain mitochondria or nucleoli individually with orange fluorescence under different focal lengths. Compounds L6–8 were prepared, for comparison, to further explore the mechanism of the binding of L1–5 with RNA, which revealed that the synergistic effect of the amino group and the pyridinium cation played a significant role in distinct cell imaging. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are important subcellular organelles that play a huge role in cell metabolism and growth. In this study, we synthesized two LDs fluorescent probes with benzothiadiazole (BTH) as electron acceptor and triphenylamine (TPA) as electron donor, which named as TPA-BTH1 and TPA-BTH2 , respectively. Meanwhile, we introduced long alkyl chain to the probe as a shielding group and LDs targeting enhancement group. The results showed that the two probes were too sensitive to solvents' polarity because of the D-A structures possessed twisted intramolecular charge-transfer (TICT) effect. Furthermore, we prepared the two probes into nanoprobes by nanoprecipitation, which named as TPA-BTH1-20 and TPA-BTH2-20 , respectively. The nanoprobes also had excellent fluorescence emission abilities and biocompatibility, as well as high photostability and accurately target LDs ability, which could be successfully applied in cell fluorescence imaging experiments. Two liquid fluorescent probes targeted LDs were named TPA-BTH1 and TPA-BTH2, which showed a response to polarity of solvent. Then we prepared them into FONs by wrapping with PLGA through nanoprecipitation, and the FONs all owned excellent fluorescence emission efficiency, photostability, good dispersion in water, and better stability in cells, including photostability and resistance to photobleaching. [Display omitted] • The fluorescent probes and their nanoprobes all had high luminescence efficiency • The nanoprobes possessed excellent continuous and stable luminescence capability • The nanoprobe had precisely targeting ability to LDs [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) have attracted much attention due to their unique structure and key connections with various organelles in cells. Here, we constructed a reactive oxygen species (ROS) -generating system by carefully designing photosensitizers (TT2CN) with proper lipophilicity, excellent light stability and cell imaging ability. In detail, TT2CN can selectively accumulate into LDs (as carriers for TT2CN) and then a subcellular photo-inducible ROS-generating system was formed. Confocal fluorescence imaging revealed the contact behavior of dynamic LDs with other organelles in the cells and the photo-produced ROS can induce multiple organelle damages. Flow cytometry, AM / PI and 3D multicellular tumor spheres (3D MCTs) experiments further verified and demonstrated its promising biological application. This work not only uncovers the communication behavior between LDs and other organelles, but also provides a new anticancer strategy of LDs-mediated photodynamic therapy. [Display omitted] • TT2CN has excellent photostability and cell imaging ability. • Constructing ROS-generating system, viz, TT2CN -loaded LDs. • Confocal fluorescence imaging revealed the contact behavior of this ROS-generating system with other organelles. • ROS-generating system outstanding capability to mediate multiple subcellular organelle damage. [ABSTRACT FROM AUTHOR]

Abstract A series of compounds (W1 - W8) based on triphenylamine with -C=N- or -NH- group, were designed and studied by fluorescence emission spectra and DFT/TDDFT calculations. Probes W1 - W4 were selectively leveraged to sensitively detect glutathione by two distinct reaction mechanisms, thereinto, W1 - W2 featured a convenient detection for glutathione using hydrolysis and W3 - W4 utilized displacement to probe glutathione possessing sensitivity and practicability. Compound W5 - W8 here provided an avenue for understanding structure-property relationship. Taken considerations for toxicity and biocompatibility together, W1 - W4 showed great advance for endogenously and exogenously imaging GSH in living cells. Graphical abstract Image 1 Highlights • A series of fluorescent probes for monitoring glutathione were synthesized. • Structural relation adjustment introduced two distinct reaction mechanisms: hydrolysis and replacement. • The probes had a good advantage for further endogenously and exogenously monitoring glutathione in vivo. [ABSTRACT FROM AUTHOR]

Abstract Mitochondria and glutathione (GSH) play crucial roles in human pathologies. To better understand the disease mechanisms, two-photon fluorescence probes responding to mitochondria and glutathione were urgently pursued. Here, a series of two-photon fluorescence probes (5a, 5b and 5c) were prepared, which could detect GSH as well as target mitochondria. The probes delivered high and rapid selectivity towards GSH among the various biothiols and qualitatively monitored the endogenous cellular GSH in real-time via a two-photon laser confocal fluorescence microscopy. Furthermore, the theoretical understanding of high selectivity in two-photon fluorescence probes were also performed. The combined results demonstrated that the probes would function as efficient tools in bio-imaging and biological diagnosis. Graphical abstract Image 1 Highlights • A series of two-photon fluorescence probes (5a , 5b and 5c) exhibited high selectivity and sensitivity for GSH. • 5a-c could accumulate on the mitochondria based on the membrane potential. • 6a-c complex could qualitatively monitor the endogenous GSH in real-time via two-photon fluorescence microscopy. [ABSTRACT FROM AUTHOR]

With the increasing of human activities, the issue of environmental pollution is currently more and more serious, such as Al 3+ (Cu 2+ ) pollutants which deeply influenced the growth of animal and plant life. Meantime, detecting them in living tissues are largely restricted by biocompatibility of probes. Herein, we use triphenylamine fluorophore and salicylaldehyde moiety to construct a dendrimer-like probe L which has a sensitive and selective detection of Al 3+ and Cu 2+ in single solvent simultaneously. These critical attributes such as good selectivity, high sensitivity, low cytotoxicity, high photostability that encourage us to further explore the potential in living cells and deep-tissues. The experiments demonstrate that L not only can image the intracellular Al 3+ and Cu 2+ but visualize them accumulated in zebra fish and Arabidopsis at the organelle level, which indicate L has micrometer-level analysis towards Al 3+ and Cu 2+ . [ABSTRACT FROM AUTHOR]

Small-molecules with large two-photon (2P) action cross-section, superb biocompatibility and specificity are extremely demanded for two-photon bioimaging. Herein, a coumarin derivative ( L ) containing S-benzyldithiocarbazate group has been investigated both experimentally and theoretically as an efficient two-photon biosensor for lipophilic substances. The results revealed that compound L possessed a very large 2P action cross-section (Φs) up to 260 GM. Further, in cellulo studies demonstrated that compound L was capable of effectively labeling membrane-rich endoplasmic reticulum (ER) in living cells. Moreover, live/dead bacteria assessment using L indicated that such compound could serve as a highly fluorescent probe for bacteria mortality, which is of great importance for monitoring the viability change of bacteria under storage, evaluating disinfection efficiency, as well as for studying the pharmacokinetic and pharmacodynamic properties of antibiotics. [ABSTRACT FROM AUTHOR]

Two similar structural triphenylamine-based Schiff bases “off-on” fluorescent probes for detecting Al 3+ through naked eye manner were prepared by changing their bridging groups, one via styrene ( LW1 ), the other via phenethyl ( LW2 ). This modification affected the performance remarkably in terms of selectivity, sensitivity and efficiency as well as recognition mechanism. The experimental results showed probe LW1 can selectively detect trivalent ion especially for Al 3+ by hydrolysis-chelation-enhanced fluorescence with a detection limit of 1.22 × 10 −7 M. However, probe LW2 can only highly selectively detect for Al 3+ by the direct chelation-enhanced fluorescence with a detection limit of 2.99 × 10 −7 M. Furthermore, benefiting from their good water solubility and biocompatibility, cell imaging and real-time monitoring of Al 3+ in living HepG2 cells were successfully achieved. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe for Zn 2+ has been designed and synthesized based on a dipicolylamine group connected by a benzimidazole amide backbone. A comprehensive analysis of the recognition ability of the probe towards metal ions was conducted by ultraviolet absorption and fluorescence emission spectroscopy. Results demonstrated that the probe showed selective and sensitive fluorescence turn-on signaling behavior toward Zn 2+ in HEPES buffered (pH = 7.4) aqueous solution. The detection limit of this probe was calculated to be 5.10 × 10 −8 M for Zn 2+ . Fluorescent imaging inside HepG2 cells indicated potential application of the probe for detecting Zn 2+ ions in living cell imaging. [ABSTRACT FROM AUTHOR]

Cis-trans isomer and polymorphism of 9-(4-(4-nitrostyryl)phenyl)-9H-carbzole (Dye 1 ) were obtained unexpectedly. Each isomer has two polymorphs, which was characterized by X-ray single crystal diffraction. Polymorphs T1 and T2 are trans -configuration and both crystallize in monoclinic space group P 21/c. Polymorphs C1 and C2 are cis -configuration and crystallize in triclinic space group P -1 and monoclinic space group P 21/c, respectively. Trans -isomer shows better stability and higher density than that of cis -isomer, but cis -isomer displays better solubility than that of trans -isomer. The molecular structures and packing arrangements of the four kinds of crystals show different features. The twisted conformation of cis -isomer effectively avoids π-π interactions and close packing. Both the trans and cis isomers show remarkable aggregation-induced emission effect in the acetonitrile/water mixture. In addition, fluorescence cell imaging experiment proves the potential application of the two isomers of dye 1 . [ABSTRACT FROM AUTHOR]

A series of novel complexes bearing high fluorescence quantum yields and showing the peak two-photon absorption (2 PA) cross-sections in the near-infrared region, Zn(SCN) 2 L 2 (1) , [Cd(SCN) 2 L 2 ] n (2) , Co(SCN) 2 L 4 (3) , Ni(SCN) 2 L 4 (4) , [CdHgL 2 (SCN) 4 ] n (5) and [MnHg(SCN) 4 L 2 ] n (6) , containing functional chromophore ( L = (E)-(4-diethyl anilinostyryl)pyridine), were synthesized in high yields. Crystal structures of all the complexes were confirmed. Hetero-metal complexes ( 5 , 6 : L:M = 1:1) present much higher two-photon absorption (2 PA) cross-sections (σ) in comparison with those of the homo-metal complexes (L:M = 4:1 in 3 and 4 , L:M = 2:1 in 1 and 2 ) and the free ligand ( L ) which may due to the fact that the hetero-metal complexes have more bridged anions (SCN − ), conjugated subunits –[Hg(SCN) 2 M]– and –[Hg 2 (SCN) 4 M 2 ]–. In addition, the results revealed that 2 PA response was much enhanced for the Zn(SCN) 2 L 2 and two-photon fluorescence cell imaging experiment proved its potential application. [ABSTRACT FROM AUTHOR]

Two Schiff base derivatives based on diaminomaleonitrile were synthesized and characterized. Both of the two compounds displayed a highly selective UV and off-on type fluorescent response to Cu 2+ in acetonitrile solution. The mixtures of Cu 2+ with 1 or 2 showed great potential application in bioimaging. Two different polymorphs of compound 1 were obtained from ethanol and ethyl acetate, respectively, which exhibit obvious differences in the wavelength and intensity of the fluorescence emission. This interesting phenomenon may originate from the tightness of packing and π–π interactions in the stacking structure. Compound 2 was aggregation-enhanced emission (AEE)-active in tetrahydrofuran (THF)/water mixtures. Moreover, compound 2 in a solid amorphous state was collected though special methods, which showed completely different fluorescence compared with that of the crystal due to the irregular molecular aggregation pattern. [ABSTRACT FROM AUTHOR]

A coumarin-based colorimetric and fluorescence off–on probe (L) containing diaminomaleonitrile unit was synthesized. The probe can detect Cu 2+ in acetonitrile solution with high sensitivity and selectivity. The single crystal structures of probe L and L-Cu 2+ complex showed that Cu 2+ played dual roles of coordination center and catalyst that catalyzed the ring-closing of diaminomaleonitrile moiety in the recognition process based on addition reaction. Moreover, this probe can successfully detect Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

Abstract: Two novel aza-crown ether derivatives based on stilbene were synthesized and characterized. Their linear photophysical properties were systematically investigated in various solvents. The nonlinear photophysical properties were investigated by two-photon induced fluorescence method. The two-photon absorption cross sections values measured by two-photon excited fluorescence were determined to be 328.2 GM and 246.55 GM for the dyes derived from monoaza 15-crown-5 and 18-crown-6, respectively, which accorded with dipole moment changes under photoexcitation. In addition, a single-photon fluorescence cell imaging experiment proved that dye derived from monoaza 15-crown-5 was suitable for biomedical imaging. [Copyright &y& Elsevier]

A series of benzoxazole-pyridinium salt derivatives with two-photon excited fluorescence performance were synthesized and fully characterized. Among them, compounds 2 , 3 and 4 were the isomers with different positions of pyridine N, while compounds 4N , 4S , 4P , 4F and 4B were derived from compound 4 through anion exchanging reaction. Their photophysical properties had been systematically investigated, and the results indicated that the position of pyridine N and the type of anions had a significant influence on their optical properties and bio-imaging application. Transforming the position of pyridine N could affect their fluorescence quantum obviously; the maximum fluorescence quantum is 0.21 for compound 3 in DMF. Meanwhile, we found that the altering anions might be used to regulate their two-photon fluorescence performance, only compounds 4N , 4P and 4B possessed excellent two-photon excited fluorescence emissions, and the highest two-photon cross-section was 1868.69 GM for compound 4B in DMF. In addition, two-photon fluorescence cell imaging experiment demonstrated the potential bio-application of partial compounds with good photostability and low cytotoxicity. A series of water solubility of benzoxazole-pyridium salt derivatives including compounds 2 , 3 , 4 , 4N , 4F , 4P , 4S and 4B with excellent two-photon excited fluorescence performance were synthesized and applied in biological imaging. The structure-property relationship study showed that the position of pyridine N and the type of anions have a significant influence on their optical properties and bio-imaging application. [Display omitted] •The structure of target compounds was determined by HR MS with positive and negative ion model. •Counter anions had a influence on the two-photon excited fluorescence emissions. •The position isomerization of pyridine N affected their biological imaging performance. [ABSTRACT FROM AUTHOR]

In this study, a water-soluble and upconverting PSI OAm -modified Sr 2 LaF 7 : 20%Yb3+/6%Er3+ (abbreviated as SLF@PSI OAm) with a small size of ~10 nm was designed and prepared for bioimaging. The optimum and intensest red-light emission at 640–690 nm was modulated via 6% Er3+ doped under irradiation at 980 nm, and the ratio of red and green emission intensely (I red / I green) was as high as 1.378. Interestingly, biological experimental results showed that SLF@PSI OAm with low toxicity and excellent cell/tissues permeability could not only be applied to cells imaging, but also successfully visualize lipid-rich tissues in living zebrafish. Therefore, it can be anticipated that the as-prepared material would be a potential tool for upconversion fluorescence bioimaging. SLF@PSI OAm with small size, intense red emission, low toxicity and excellent cell/tissues permeability could not only be applied to cells imaging, but also successfully visualize lipid-rich tissues in living zebrafish. Image 1 • A new upconverting bio-probe folic acid-modified PSI OAm -modified Sr 2 LaF 7 : 20%Yb3+/6%Er3+ (abbreviated as SLF@PSI OAm) was designed and prepared. • SLF@PSI OAm exhibits the optimum and intensest red-light emission via modulating the doped content of Er3+. • SLF@PSI OAm was successfully used to in vitro/vivo UCL imaging of living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Fluorescence probe 1 with high specificity towards foreign protein BSA delivered "turn on" fluorescence. Furthermore, the probe 1 accomplished the visualization of the foreign protein BSA ingested into cells under the confocal laser scanning microscopy (CLSM), which exhibited targeting ability towards subcellular organelles related with proteins such as endoplasmic reticulum, lipids droplets, and lysosome. • Probe 1 for illumining foreign protein BSA was developed successfully via fine-tuning of structure. • Mechanism between BSA and probe 1 was studied deeply via 1H NMR titration experiment and molecular docking simulation. • Visualization processes among subcellular organelles related with proteins were realized. Traditional biotechnology, taking advantage of fluorescent protein (FP) to investigate the foreign protein, was difficult to visualize and image accurately in living cells. Herein, bovine serum albumin (BSA) was illumined in virtue of the prepared probe 1 , which could monitor the foreign protein of the intracellular recognition, transportation and metabolism under confocal microscopy. Verified by 1H NMR titration experiment and molecular docking simulation, the probes bonded to BSA mainly through hydrogen bond and suitable hydrophobicity, realizing the visualization and high-fidelity imaging of the foreign protein in living cells. The results provided the beneficial approach and methodology for further understanding protein metabolism. [ABSTRACT FROM AUTHOR]