A redox reversible endoplasmic reticulum-targeted fluorescent probe for revealing the redox status of living cells.

The endoplasmic reticulum (ER) is one of the most important organelles in cells and is involved in protein synthesis, folding and orderly transport. Redox balance is the key to its normal function. In this work, we designed and synthesized an endoplasmic reticulum-targeted fluorescent probe N-Se with selenomorpholine as the redox reversible detection moiety. N-Se could selectively respond to ClO- within only 8 s with a LOD of 28.8 nM. Furthermore, such a response is reversible in the regulation of GSH. Confocal fluorescence imaging confirmed the excellent endoplasmic reticulum targeting ability of N-Se. Thus, it could real-time monitor the dynamic changes of the redox status in the endoplasmic reticulum through the variation of the fluorescence intensity.

A turn-on homodimer fluorescent probe based on homo-FRET for the sensing of biothiols in lysosome: a trial of a new turn-on strategy.

Fluorescence resonance energy transfer (FRET) is often applied to construct fluorescent probes for acquiring high selectivity and sensitivity. According to the FRET theory, a homodimer composed of two identical fluorophores with a small Stokes shift has only weak fluorescence due to homo-FRET between fluorophores, and the fluorescence could be recovered after the destruction of the homodimer. In this study, we designed and synthesized a homodimer fluorescent probe, namely 1,3,5,7-tetramethyl-8-(4'-phenylthiophenol)-boron difluoride-dipyrrole methane dimer (D-TMSPB), based on this turn-on strategy. In D-TMSPB, the disulfide moiety was selected as the response moiety of biothiols, and BODIPY fluorophore was chosen as both donor and acceptor in FRET due to the ultra-small Stokes shifts and obvious overlap of its excitation/emission peak. D-TMSPB exhibited only weak fluorescence. After selective reaction with biothiols, FRET was destroyed and the derivative exhibited strong fluorescence at 514 nm with the limit of detection of about 0.15 µM for GSH. Notably, the derivative of biothiols shows remarkable fluorescence only in acidic conditions, which accords with the internal environment of lysosome. Thus, D-TMSPB was applied to image the biothiols of lysosome in living cells. The turn-on fluorescence of D-TMSPB indicated that homo-FRET is a practical strategy to design turn-on fluorescent probes, particularly for the sensing mechanism based on leaving groups.

Size-controlled synthesis of metal-organic frameworks and their performance as fluorescence sensors.

Metal-Organic Frameworks (MOFs) are of bright promise as new fluorescence sensors because of their accurate framework structure and unique fluorescence properties. Many MOFs have been reported as fluorescence sensors, including bulk-MOF-crystals and nano-MOF-powder. Obviously, the sensing performance of these MOF sensors should be diverse due to their different sizes. However, bulk-MOF-crystals and nano-MOF-powder have completely different dispersibility in solvents, and the effects of this difference on the analytical performance like precision and sensitivity are significant but have not been discussed systematically. To investigate such effects, rodlike bulk-MOFs and nano-MOFs with the same structure but different sizes are required. In this work, we obtained MOFs with a crystal width ranging from 9.7 µm to 170 nm by controlled synthesis, and then proved that they have the same structure by PXRD, SEM, TGA and FTIR analysis. After that, taking folic acid as the target molecule, fluorescent sensing experiments were carried out to compare the sensing performance between bulk-MOFs and nano-MOFs. From the results, we found that nano-MOFs have obviously better dispersity, a lower precipitation speed, a smaller standard deviation, ten times higher fluorescence intensities and a much lower LOD than bulk-MOFs. Finally, we draw a conclusion that nano-MOFs are more in line with the requirements of analytical performance as fluorescence sensors, and the size of MOFs as fluorescence sensors should be as small as possible.

A fluorescent probe for carbon monoxide based on allyl ether rather than allyl ester: A practical strategy to avoid the interference of esterase in cell imaging.

Pd0-mediated Tsuji-Trost reaction is a practical strategy to design fluorescent probes for carbon monoxide (CO) sensing, and in such reaction CO can reduce Pd2+ to Pd0 in-situ and remove allyl groups on fluorophores. In most of these probes, esters are commonly used to link allyl on fluorophores. We found that the ester groups could be hydrolyzed by esterase activity of fetal bovine serum (FBS), while FBS is a requisite in cell culture, and the hydrolysis could interfere the Pd0-mediated Tsuji-Trost reaction. In this study, we synthesized a fluorescent probe (Cou-CO) using allyl ether as reaction site rather than allyl ester. Cou-CO is non-fluorescence, and could react with CO under the presence of Pd0 to form Cou with strong fluorescence, and the maximum excitation and emission wavelengths of Cou are 464 nm and 495 nm respectively. Cou-CO shows excellent selectivity to CO and could avoid the effect of FBS with the limit of detection for CO is 78 nm. Finally, Cou-CO was successfully applied for imaging of CO in living cells.

[Raman spectra and photoluminescence spectra of InGaN/GaN multiquantum wells annealed].

InGaN/GaN multiquantum well, grown by MOCVD on a sapphire substrate and annealed under the conditions of 700 and 900 degrees C x (20 min)(-1), was studied by means of mirco-Raman spectroscopy and photoluminescence. The Raman peak of E2, A1 showed red shift after multiquantum were wells annealed, and the HWHM of Raman peakdecreased imperceptibly. Moreover,the photoluminescence peak of the sample annealed under the condition of 700 degrees x (20 min)(-1) showed a red shift, then appeared a blue shift under the condition of 900 degrees C x (20 min)(-1). These results clearly showed that the sample annealed induced strain stress relief that could explain Raman peak shift, but the piezoelectric field induced the quantum-confined Stark effect, which can't agree with the photoluminescence experiment. Sample annealed could change the width of quantum well and InGa phase segregated; these factors influencing structure of quantum well could explain the results of photoluminescence spectra.