Ultrasensitive detection of butyrylcholinesterase activity based on self-polymerization modulated fluorescence of sulfur quantum dots.

Butyrylcholinesterase (BChE) is an important clinical diagnosing index for liver dysfunction and organophosphate toxicity. However, the current assays for BChE activity are suffering from the relative poor detection sensitivity. In this work, an ultrasensitive fluorescence assay for BChE activity was developed based on the self-polymerization modulated fluorescence of sulfur quantum dots (S-dots). The luminescence of S-dots can be quenched by the self-polymerized dopamine. The hydrolysate of substrates, thiocholine, under the catalysis of BChE can reduce dopamine, which results in the inhibition of self-polymerization and the fluorescence recovery of S-dots. BChE can be quantitatively detected by recording the recovered fluorescence of S-dots, and a linear relationship is observed between the ratio of fluorescence and the concentration of BChE in the range from 0.01 to 10 U/L. A limit of detection as low as 0.0069 U/L calculated, which is the lowest number so far. The assay also shows excellent selectivity towards various interference species and acetylcholinesterase. These features allowed the direct detection of BChE activity in human serum, demonstrating the great practical applications of our assay.

Glutathione modulated fluorescence quenching of sulfur quantum dots by Cu2O nanoparticles for sensitive assay.

Sulfur quantum dots (S-dots) show great potential for applications in various field, due to their favorable biocompatibility, high stability, and antibacterial properties. However, the use of S-dots in chemical sensing is limited by the lack of functional groups on the surface. In this work, a fluorescence glutathione (GSH) assay is developed based on the GSH modulated quenching effect of Cu2O nanoparticles (NP) on S-dots. The fluorescence of S-dots is effectively quenched after forming complex with Cu2O NP through a static quenching effect (SQE). Introducing of GSH can trigger the decomposition of Cu2O NP into GSH-Cu(I) complex, which leads to the weaken of SQE and the partial recover of the fluorescence. The intensity of recovered fluorescence shows a positive correlation with the concentration of GSH in the concentration range of 20 to 500 µM. The fluorescence GSH assay shows excellent selectivity and robustness towards various interferences and high concentration salt, which endow the successful detection of GSH in human blood sample. The presented results provide a new door for the design of fluorescence assays, which also provides a platform for the applications in nanomedicine and environmental science.

Ratiometric sensing of butyrylcholinesterase activity based on the MnO2 nanosheet-modulated fluorescence of sulfur quantum dots and o-phenylenediamine.

Butyrylcholinesterase (BChE) can modulate the expression level of cholinesterase, which emerges as an important clinical diagnose index. However, the currently reported assays for BChE are suffering from the problem of interferences. A ratiometric fluorescence assay was developed based on the MnO2 nanosheet (NS)-modulated fluorescence of sulfur quantum dots (S-dots) and o-phenylenediamine (OPD). MnO2 NS can not only quench the fluorescence of blue emissive S-dots, but also enhance the yellow emissive OPD by catalyzing its oxidation reactions. Upon introducing BChE and substrate into the system, their hydrolysate can reduce MnO2 into Mn2+, leading to the fluorescence recovery of S-dots and failure of OPD oxidation. BChE activity can be quantitatively detected by recording the change of fluorescence signals in the blue and yellow regions. A linear relationship is observed between the ratio of F435/F560 and the concentration of BChE in the range 30 to 500 U/L, and a limit of detection of 17.8 U/L has been calculated. The ratiometric fluorescence assay shows an excellent selectivity to acetylcholinesterase and tolerance to various other species. The method developed  provides good detection performances in human serum medium and for screening of  inhibitors.

Photoluminescence investigations of sulfur quantum dots synthesized by a bubbling-assisted strategy.

Sulfur quantum dots (S-dots) emerge as promising luminescent materials owing to their remarkable optical properties. However, the mechanisms of their formation and photoluminescence remain concealed. We reveal these mechanisms by the bubbling-assisted synthesis and spectroscopic study of S-dots formed from sulfur ions produced by the alkaline oxidation of bulk sulfur under the passivation of PEG. The emission colour of the S-dots depends on the size, explained by the quantum confinement effect. The dots' luminescent quantum efficiency is strongly affected by the surface sulfur species, which is optimized by the proper surface oxidation. The simple synthesis, excellent luminescence properties, and metal-free nature attract S-dots to optoelectronic and electroluminescence applications.

Heterogeneous Structured Bi2S3/MoS2@NC Nanoclusters: Exploring the Superior Rate Performance in Sodium/Potassium Ion Batteries.

Bismuth-based materials have attracted increasing attention in the research field of sodium/potassium-ion batteries owing to the high theoretical capacity. Unfortunately, the large volume variation and poor electrical conductivity limit their electrochemical performance and applications. Herein, we report a composite of heterostructured Bi2S3/MoS2 encapsulated in nitrogen-doped carbon shell (BMS@NC) obtained by a solvothermal reaction as a novel anode material for sodium/potassium-ion batteries. The coating of the carbon layer could effectively relieve structural strains stemmed from the large volume change and improve electrical conductivity. More importantly, by skillfully constructing the heterostructure, an internal electric field formed on the heterointerface provides a rapid diffusion of ion and charge. As a consequence, the BMS@NC composite showed an excellent electrochemical performance for both sodium-ion batteries (a capacity of 381.5 mA h g-1 achieved at a current density of 5.0 A g-1 and 412 mA h g-1 at 0.5 A g-1 after 400 cycles) and potassium-ion batteries (a high specific capacity of 382.8 mA h g-1 achieved after 100 cycles at 0.1 A g-1). The design of the Bi2S3/MoS2 heterostructure provides an effective strategy to develop energy storage materials with good electrochemical properties.

Ultrasensitive detection of butyrylcholinesterase activity based on the inner filter effect of MnO2 nanosheets on sulfur nanodots.

Butyrylcholinesterase (BChE) activity is an important index for a variety of diseases. In this work, a "turn-on" assay is proposed based on controlling the inner filter effect (IFE) of MnO2 nanosheets (NSs) on sulfur nanodots (S-dots). The fluorescence of S-dots is effectively quenched by the MnO2 NSs, due to the wide overlap of the emission spectrum of S-dots and absorption spectrum of MnO2 NSs, together with the superior light absorption capability of MnO2 NSs. BChE can catalyze acetylthiocholine and produce thiocholine, which effectively decomposes the MnO2 NSs into Mn2+, resulting in the disappearance of the IFE and recovery of fluorescence of S-dots. Two-stage linear relationships between the ratio of fluorescence intensity and concentration of BChE are observed from 0.05 to 10 and from 10 to 500 U L-1. A limit of detection of 0.035 U L-1 is achieved, which is the best performance so far. The as-proposed assay is robust enough for practical detection in human serum, and it can avoid interference from its sister enzyme (acetylcholinesterase) and glutathione at the micromolar level. The presented results provide a clue for the functionalization of S-dots, and offer a powerful tool as an analytic technique for nanomedicine and environmental science.

Hydrogen Peroxide Assisted Synthesis of Highly Luminescent Sulfur Quantum Dots.

An H2 O2 -assisted top-down approach is used to synthesize brightly luminescent, color-tunable sulfur quantum dots (SQDs), with a photoluminescence quantum yield of up to 23 %. The formation of SQDs involves dissolution of bulk sulfur powder into small particles in an alkaline environment in the presence of polyethylene glycol, followed by H2 O2 -assisted etching of polysulfide species, which has the advantage of the passivation of surface states. This synthetic strategy allows us to simultaneously control the final size of SQDs, to tune their emission color, and to improve their emission quantum yield by eliminating surface traps. Down-conversion white light emitting diodes were also fabricated using blue emissive SQDs and orange emissive copper nanoclusters, with CIE color coordinates of (0.33, 0.32) and a high color rendering index of 91. The water-soluble, highly luminescent SQDs are promising luminescent materials that can be produced from abundant precursor materials.

MicroRNA-451 dictates the anoikis resistance of osteosarcoma by targeting Rab14.

Cancer cells have developed anoikis resistance and thereby survive after detachment from their primary site and while traveling through the circulation. However, the mechanisms underlying resistance to anoikis in osteosarcoma (OS) remain largely unknown. MicroRNAs (miRNA) have been reported to contribute to malignant phenotypes of cancer cells. To investigate the roles of miRNAs in anoikis resistance of OS cells, the implications of 9 well-characterized miRNAs that dysregulated in OS on cell anoikis were screened. As a result, miR-451 was identified as a crucial factor involved in anoikis resistance and anchorage-independent growth of OS cell. MiR-451 was down-regulated in OS cells, re-expression of miR-451 significantly promoted cell anoikis of three OS cell lines and inhibition of miR-451 protected HOS cells from anoikis under anoikis condition. Subsequently, bioinformatics prediction and luciferase reporter assay indicated that Rab14 was a direct target of miR-451, and Rab14 could be down-regulated by miR-451 at both mRNA and protein levels. Genetic silencing of Rab14 recapitulated the role of miR-451 on anoikis resistance and restoration of Rab14 largely abrogated the tumor suppressor function of miR-451. Finally, overexpression of miR-451 remarkably suppressed the lung metastasis of OS cells. Collectively, our findings suggest that the miR-451/Rab14 axis might serve as a novel mechanism of resistance to anoikis in OS.

Transglutaminase-2 is Involved in Cell Apoptosis of Osteosarcoma Cell Line U2OS Under Hypoxia Condition.

Osteosarcoma is the most common type of solid bone cancer, which is the second leading cause of cancer-related death. Hypoxia is an ordinary phenomenon in solid tumor tissues and can induce cell apoptosis but the specific molecular mechanism remains unclear. In this study, we explored the effect and the molecular mechanism of Transglutaminase 2 (TG2) on cell apoptosis in osteosarcoma U2OS cells under hypoxia. We found the enzymatic activity of TG2 is significantly increased and the expression of TG2 is remarkably up-regulated under hypoxia condition. Cell apoptotic rate is markedly increased upon knockdown of TG2 by siRNA under hypoxia. We further investigated the mechanism of cell apoptosis and found Bax protein is significantly increased after depletion of TG2 under hypoxia. Moreover, our data also show that cytochrome C (Cyt C) is significantly increased in cytoplasm and markedly decreased in mitochondria of U2OS cells after depletion of TG2 under hypoxia. Our results suggest that TG2 can inhibit tumor cell apoptosis through down-regulation of Bax and prevention of release Cyt C from mitochondria into cytoplasm.

[Microanalysis study of the inspirable nano-particles into lungs by SEM and XREDS].

Inspirable nano-particles into lungs in the atmosphere were studied in this paper. Field emission scanning electron microscope (FSEM) and X-ray energy dispersive spectrometer were used to investigate the morphology and major constituents of inspirable nano-particles into lungs systematically. The results showed that most of the inspirable nano-particles in the atmosphere are spherical and ellipsoidal, with smooth surface and dense structure. The smaller nano-particles are clustered into loose floccule, with the sizes in the range of 30 to 100 nm. The constant elements in the nano-particles are close consistent with the large particle pollutants, which mainly contain C, O, Al, Si, Na, Mg, K, Ca, Fe, S and Cl etc. The point Analysis of EDS confirmed that the element content of Cl and S in some nano-particles is significantly increased, while others mainly contain C and O. It is believed that the surface of nano inorganic dust particles was adsorbed by the organic pollutants to form the core-shell structure nano-particles pollutants in the process of aerosol formation. Thus, reducing anthropogenic emissions of organic pollutants has great influence on the formation of inspirable nano-particles.

[Microanalysis study of Co-doped ZnO DMS crystal by SEM and XREDS].

In the present paper,with CoCl2 x 6H2O used as precursor, Co-doped ZnO diluted magnetic semiconductor (DMS) crystals were synthesized by hydrothermal method with KOH as mineralizer. The morphology, and the relative content and distribution uniformity of the surface and inner Co element of synthesized crystals were investigated by scanning electron microscope (SEM) and X-ray energy dispersive spectrometry (XREDS), respectively. It was found that Co-doped ZnO crystals with different morphology were yielded, while the bigger crystals showed polar growth charactertistics, and the Co content in the crystal depended on its morphology. The exposed face also changed with crystal morphology. There was more Co in bigger crystals than in smaller ones. Moreover, more Co located in +c (10 11)compared to +c (10 10) exposed face, especially for cone crystals. In addition, it was observed that there was a little amount of cobalt oxide cluster in inner crystal,and the distribution of Co content was relative uniform in both the surface and inner part of the crystal. Cobalt oxide cluster may have effect on the magnetic properties of Co-doped ZnO diulted magnetic semiconductor since Co2+ possesses magnetic property.

[Synthesis and luminescent properties of novel red phosphor SrO . Y2O3 : Eu].

A novel red-emitting phosphor SrO . Y2O3 : Eu was synthesized by glycine combustion process. The phases and structure, the size and morphology, and the luminescent properties of the samples were investigated respectively by XRD, SEM and fluorescence spectrophotometer (FL). The results show that the samples include two phases, SrY2O4 and Y2O3, which belong to orthorhombic system and cubic system respectively. The particles of SrO . Y2O3 : Eu obtained at 1 200 degrees C are nearly spherical in shape, and the mean grain size is in the range of 100-200 nm. The excitation spectrum of SrO . Y2O3 : Eu phosphor shows a broad band with a main peak around 280 nm, which is due to the charge-transfer (CT) in the excitation of an electrons from the oxygen 2p state to an Eu3+ 4f state. Excited with a radiation of 280 nm, the phosphor emits strong red fluorescence, and the main emission peak is around 592 nm, which can be assigned to the transition of 5D0 -->7 F1 of Eu3+ ion. Another strong emission peak is at 614 nm, which can be assigned to the transition of 5D0 --> 7 F2 Of Eu3+ ion. Moreover, it was found that the ratio of glycine to nitrate ion, calcinations temperature and the concentration of Eu3+ have significant effect on the luminescent intensity of SrO . Y2O3 : Eu.

[Synthesis of the red long afterglow phosphor Gd2O2S: Eu, Mg, Ti by microwave radiation method and its luminescent properties].

Gd2O2S: Eu, Mg, Ti, a novel red long afterglow phosphor, was synthesized in microwave field. The synthesized phosphors were investigated respectively by XRD, SEM and fluorescence spectrophotometer. The results show that Gd2O2S: Eu, Mg, Ti phosphors possess hexagonal crystal structure, which is similar to that of Gd2O2S. The particles of Gd2O2S: Eu, Mg, Ti phosphors are basically spherical in shape, with good dispersing. The mean particle size is 1-2 microm. The excitation spectrum is a broad band and the main peak is at 360 nm. Moreover, excitation peaks at 400, 422 and 472 nm were found in the excitation spectrum. The emission spectrum shows that Gd2O2S: Eu, Mg, Ti has narrow emission peaks. The emission peaks are ascribed to Eu3+ ions transition from 5 D(J) (J = 0, 1, 2) to 7F(J) (J = 0, 1, 2, 3, 4). With the increase in Eu3+ molar ratio, the emission peaks at 586, 557, 541, 513, 498, 471 and 468 nm in the blue and green region weaken gradually relative to the main emission peak at 627 nm. Therefore the red emitting at 627 nm becomes strong gradually. When the molar ratio is 6%, the red emitting becomes the strongest. The Ti and Mg co-doping can obviously improve its long-afterglow property.

[Preparation of nanocrystal Gd2O3: Eu by EDTA complexing sol-gel process and spectroscopic study].

Gd2O3: Eu nanocrystal was synthesized by EDTA complexing sol-gel process at relatively low temperature, in which ethylene-diamine-tetraacetic acid (EDTA) and polyethylene glycol (PEG) were used as the chelating agent and disperser respectively. The properties of the nanocrystal were investigated by XRD, SEM, EDS, and fluorescence spectrophotometer. The results show that nanosized, homogenous and pure cubic phase Gd2O3: Eu has been produced after the precursor calcined at 800 degrees C for 2 h. The particles of the Gd2O3: Eu are basically spherical in shape and about 30 nm in size. The main emission peak of Gd2O3: Eu nanocrystal is at 611 nm, resulting in a red emission. Compared with micron scale Gd2O3: Eu phosphors prepared by a conventional method, a clear red shift occurs in the excitation spectrum of Gd2O3: Eu nanocrystal prepared by the present work, and the quenching concentration of Eu has been raised. For this type of nanophosphor, quenching starts at an Eu concentration of 8% (mol%), while a value of 6% was obtained for the conventional one.