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To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD. [Display omitted] [ABSTRACT FROM AUTHOR]

A fluorescent probe ( 1 ) for distinguishing amongst biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), is developed based on different cascade reactions. The key design feature of fluorescent probe 1 is the integration of two potential reaction groups for the thiol and amino groups of biothiols in one molecule. By reacting with the halogen atom and α, β-unsaturated malonitrile in probe 1 , Cys, Hcy and GSH can generate a total of three main products with distinct photophysical properties. Probe 1 shows a strong fluorescence turn-on response to Cys with blue–green emission by using an excitation wavelength of 390 nm. At an excitation wavelength of 500 nm, probe 1 responds to GSH over Cys and Hcy and emits strong orange fluorescence. The discrimination of biothiols can be demonstrated by cell imaging experiments, indicating that probe 1 can be a useful tool for the selective imaging of Cys and GSH in living cells. [ABSTRACT FROM AUTHOR]

The 4−N,N-dimethyl-1,8-naphthalimide based fluorescent probes have been explored for selective detection of Au 3+ . Both probes show a pronounced fluorescence enhancement response to Au 3+ . Hydroxy is introduced as ligand of Au 3+ for Probe 1 and the newly designed Probe 2 contains an alkyne moiety to recognize Au 3+ through an irreversible C≡C bond hydrolysis reaction. Probe 1 exhibits higher performance such as faster response, lower detection limit of 0.050 μM and the better responsive effect in 99.5% water system compared with most of probes published. The Probe 2 displays high stability to pH, suitable water solubility, wider linear range (0–100 μM) to Au 3+ , and live-cells imaging with low cytotoxicity. [ABSTRACT FROM AUTHOR]

Phosphorus and nitrogen doped carbon dots (PN-CDs) were conveniently prepared by carbonization of adenosine-5′-triphosphate using a hydrothermal treatment. The PN-CDs with P/C atomic ratio of ca. 9.2/100 emit blue luminescence with high quantum yields of up to 23.5%. The PN-CDs were used as a novel sensing platform for live cell imaging of reactive oxygen species (ROS) and reactive nitrogen species (RNS), including ClO − , ONOO − , and NO in macrophages. The nanosensor design is based on our new finding that the strong fluorescence of the PN-CDs can be sensitively and selectively quenched by ROS and RNS both in vitro and in vivo. These results reveal that the PN-CDs can serve as a sensitive sensor for rapid imaging of ROS and RNS signaling with high selectivity and contrast. [ABSTRACT FROM AUTHOR]

A naphthalimide-based fluorescent probe CP has been synthesized with simple steps. It can selectively and sensitively recognize copper ions (Cu 2+ ) in HEPES buffer (50 mM, pH 7.2). The fluorescence intensity of CP is linearly proportional to the concentration of Cu 2+ ranging from 0–8.3 μM (correlation coefficient R 2 =0.9808). The resulted complex CP@Cu can serve as a turn-on fluorescent probe for the detection of histidine and histidine rich proteins in broad pH application range. Upon the addition of histidine, the fluorescence intensity of CP@Cu exhibits a linear correlation with the concentration of histidine ranging from 0–200 μM (correlation coefficient R 2 =0.9912). Moreover, CP@Cu has potential for imaging histidine in vitro experiments and has promise in real sample applications with great validity. [ABSTRACT FROM AUTHOR]

Abstract: Acrylic acid 3-acetyl-2-oxo-2 H-chromen-7-yl ester (ACA) was rationally designed and synthesized as a simple and effective fluorescent probe for sensing cysteine with high selectivity and naked-eye detection. The probe can detect cysteine by fluorescence spectrometry with a detection limit of 0.657μM and can be used with calf serum and in live cell imaging. The conjugate addition/cyclization sequence mechanism of the reaction between ACA and cysteine was confirmed by ESI-MS and fluorescence spectra. [Copyright &y& Elsevier]

Abstract: We report a novel colorimetric and red-emitting fluorescent probe for hydrazine detection based on resorufin platform. This OFF–ON fluorescent probe shows a large (117nm) red-shifted absorption spectrum and the color changes from colorless to red upon addition of hydrazine in the aqueous solution, which can serve as a “naked-eye” probe for hydrazine. Moreover, this probe also shows a significant fluorescence increase (~16 folds) and excellent linear relationship at physiological pH. Utilizing this sensitive and selective probe, we have successfully detected hydrazine in living cells. [Copyright &y& Elsevier]

Abstract: The 4-propargylamino-1,8-naphthalimide based fluorescent probe 1 has been explored as a sensor for selective detection of Au3+. 4-Amino-1,8-naphthalimides, that possess typical intramolecular charge transfer (ICT) electronic characteristics, have been widely used as versatile platforms for fluorescent probes. The newly designed probe 1 contains a propargylamine moiety at C-4 of the naphthalimide chromophore that reacts with Au3+ to generate a product that has distinctly different electronic properties from 1. Specifically, the probe undergoes a remarkable change in its absorption spectrum upon addition of Au3+ that is associated with a distinct color change from yellow to light pink. In addition, a blue shift of ca. 56nm also takes place in the emission spectra of the probe. Consequently, 1 serves as a reaction-based sensor or so called chemodosimeter for Au3+. Importantly, surfactants enhance the rate of reaction of 1 with Au3+, thus, enhancing its use as a real time sensor. Finally, the results of studies probing its application to bioimaging of Au3+ in live cells show that the probe 1 has a unique ability to sense Au3+ in cells and, in particular, in lipid droplets within cells. [Copyright &y& Elsevier]

Abstract: A new fluorescent nanoprobe, 4-amino-2,2,6,6-tetramethylpiperidine oxide (AT)-functionalized CdTe quantum dots (QDs–AT), was synthesized, for selective detection of nonprotein thiols based on electron transfer (ET). In the presence of nonprotein thiols, the nitroxide radicals in QDs–AT were converted to hydroxylamines, resulting in the fluorescence recovery of the quenched QDs. The detection mechanism of the probe was investigated using Rh-Se-2 probe. The nanoprobe has high sensitivity toward glutathione (GSH) with a detection limit of 7.1×10−8 M. The fluorescent imaging of living cells showed that QDs–AT could distinguish the concentration differences of GSH in HL-7702 and HepG2 cells. [Copyright &y& Elsevier]