Microwave-assisted one-pot synthesis of water-soluble rare-earth doped fluoride luminescent nanoparticles with tunable colors.

Polyethyleneimine (PEI) functionalized multicolor luminescent LaF(3) nanoparticles were synthesized via a novel microwave-assisted method, which can achieve fast and uniform heating under eco-friendly and energy efficient conditions. The as-prepared nanoparticles possess a pure hexagonal structure with an average size of about 12 nm. When doped with different ions (Tb(3+) and Eu(3+)), the morphology and structure of the nanoparticles were not changed, whereas the optical properties varied with doped ions and their molar ratio, and as a result emission of four different colors (green, yellow, orange and red) were achieved by simply switching the types of doping ions (Eu(3+) versus Tb(3) +) and the molar ratio of the two doping ions.

[Biosynthesis of CdS quantum dots in Saccharomyces cerevisiae and spectroscopic characterization].

In the present work, CdS quantum dots (QDs) were successfully biosynthesized at room temperature by using saccharomyces cerevisiae yeast as a carrier. Fluorescence emission spectra, ultraviolet-visible (UV/Vis) absorption spectra, and inverted fluorescence microscope images confirmed that saccharomyces cerevisiae can be used to biosynthesize CdS QDs. The as-prepared CdS QDs show the fluorescence emission peak at 443 nm and emit blue-green fluorescence under UV light (with excitation at 365 nm). Transmission electron microscopy (TEM) was applied to characterize the as-prepared CdS QDs and the TEM results showed that the as-prepared CdS QDs had the structure of hexagonal wurtzite. Fluorescence emission spectrum and UV/Vis absorption spectrum were used as the performance indicatiors to study the effects of saccharomyces cerevisiae yeast incubation times, reactant Cd2+ concentrations and reaction times on CdS QDs synthesis. Saccharomyces cerevisiae yeast grown in early stable phase can get the highest fluorescence intensity of CdS QDs when they were co-cultured with 0.5 mmol x L(-1) of Cd2+ with 24 h incubation time. Furthermore, much more CdS QDs can be obtained by changing the culture medium during the synthesis process.

Study on the sonodynamic activity and mechanism of promethazine hydrochloride by multi-spectroscopic techniques.

In this paper, the bovine serum albumin (BSA) was selected as a target molecule, the sonodynamic damage to protein in the presence of promethazine hydrochloride (PMT) and its mechanism were studied by the means of absorption, fluorescence and circular dichroism (CD) spectra. The results of hyperchromic effect of absorption spectra and quenching of intrinsic fluorescence spectra indicate that the ultrasound-induced BSA molecules damage is enhanced by PMT. The damage degree of BSA molecules increases with the increase of ultrasonic irradiation time and PMT concentration. The results of synchronous fluorescence, three-dimensional fluorescence and CD spectra confirmed that the synergistic effects of ultrasound and PMT induced the damage of BSA molecules. The results of oxidation-extraction photometry with several reactive oxygen species (ROS) scavengers indicate that the damage of BSA molecules could be mainly due to the generation of ROS and both (1)O(2) and OH are the important mediators of the ultrasound-induced BSA molecules damage in the presence of PMT.

The influence of ultrasound on the fluoroquinolones antibacterial activity.

In this work, the antibacterial effect of fluoroquinolones (FQs) upon Escherichia coli (E.coli) was measured with and without application of 40 kHz ultrasound (US) stimulation. The research results demonstrated that simultaneous application of 40 kHz US apparently enhanced the antibacterial effectiveness of FQs. That is, the synergistic effect was observed and the bacterial viability was reduced when FQs and US were combined. In addition, various influencing factors, such as FQs drug concentration, US irradiation time and solution temperature, on the inhibition of E.coli were also investigated. The antibacterial activity was enhanced apparently with increasing of FQs drug concentration, US irradiation time and solution temperature. Furthermore, we discussed preliminarily the mechanism of US enhanced antibacterial activity. Results show that US can activate FQs to produce reactive oxygen species (ROS) indeed, which are mainly determined as superoxide radical anion (·O(2)(-)) and hydroxyl radical (·OH).

Spectroscopic investigation on the synergistic effects of ultrasound and dioxopromethazine hydrochloride on protein.

The bovine serum albumin (BSA) was selected as a target molecule, the sonodynamic damage to protein in the presence of dioxopromethazine hydrochloride (DPZ) and its mechanism were studied by means of absorption and fluorescence spectra. The results of hyperchromic effect of absorption spectra and quenching of intrinsic fluorescence spectra indicated that the synergistic effects of ultrasound and DPZ could induce the damage of BSA molecules. The damage degree of BSA molecules increased with the increase of ultrasonic irradiation time and DPZ concentration. The results of synchronous fluorescence and three-dimensional fluorescence spectra further confirmed that the synergistic effects of ultrasound and DPZ induced the damage of BSA molecules. The results of oxidation-extraction photometry with several reactive oxygen species (ROS) scavengers indicated that the damage of BSA molecules could be mainly due to the generation of ROS, in which both (1)O(2) and ·OH were the important mediators of the ultrasound-inducing BSA molecules damage in the presence of DPZ.

Spectroscopic investigation on protein damage by ciprofloxacin under ultrasonic irradiation.

In recent years, sonodynamic activities of many drugs have attracted more and more attention of researchers. The correlative study will promote the development of sonodynamic therapy (SDT) in anti-tumor treatment. In this work, bovine serum albumin (BSA) was used as a protein model to investigate the intensifying effects of ciprofloxacin (CPFX) ultrasonically induced protein damage by UV-vis and fluorescence spectra. Meanwhile, the conformation of BSA is changed upon the addition of CPFX and metal ions under ultrasound (US) so that the damaging site of BSA is considered. Various influencing factors, such as US irradiation time, metal ions, solution temperature and ionic strength, on the ultrasonically induced BSA damage are discussed. It was showed that CPFX could enhance ultrasonically induced BSA damage. The damage degree of BSA was aggravated with the increasing of US irradiation time, solution temperature, ionic strength as well as the addition of metal ions. Furthermore, the reactive oxygen species (ROS) in reaction system were detected by oxidation-extraction photometry (OEP). Experimental results also showed that US could activate CPFX to produce ROS, which were mainly determined as superoxide radical anion (.O2-) and hydroxyl radical (.OH).

Synthesis and characterization of polymer eight-coordinate (enH2)[YIII(pdta)(H2O)](2)·10H2O as well as the interaction of [YIII(pdta)(H2O)]2(2-) with BSA.

The eight-coordinate (enH2)[YIII(pdta)(H2O)](2)·10H2O (en=ethylenediamine and H4pdta=1,3-propylenediamine-N,N,N',N'-tetraacetic acid) was synthesized, meanwhile its molecular and crystal structures were determined by single-crystal X-ray diffraction technology. The interaction between [Y(III)(pdta)(H2O)]2(2-) and bovine serum albumin (BSA) was investigated by UV-vis and fluorescence spectra. The results indicate that [YIII(pdta)(H2O)]2(2-) quenched effectively the intrinsic fluorescence of BSA via a static quenching process with the binding constant (Ka) of the order of 10(4). Meanwhile, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. Results indicate that the hydrophobic environments around Trp and Tyr residues were all slightly changed. The thermodynamic parameters (ΔG=-25.20 kJ mol(-1), ΔH=-26.57 kJ mol(-1) and ΔS=-4.58 J mol(-1) K(-1)) showed that the reaction was spontaneous and exothermic. What is more, both ΔH and ΔS were negative values indicated that hydrogen bond and Van der Waals forces were the predominant intermolecular forces between [YIII(pdta)(H2O)]2(2-) and BSA.

Spectrometric studies on the sonodynamic damage of protein in the presence of levofloxacin.

Taking bovine serum albumin (BSA) as typical molecules, the sonodynamic damage of protein in the presence of Levofloxacin (LVFX) and its mechanism were studied by fluorescence and UV-vis spectra. Various influencing factors such as ultrasonic irradiation time, pH value, ionic strength and solution temperature on the damage of BSA were also discussed. The results showed that ultrasound can enhance the damage of LVFX on BSA. The damage degree of BSA was aggravated with the increase of ultrasonic irradiation time, solution temperature and ionic strength, whereas decreased with the increase of solution pH value. Furthermore, the reactive oxygen species (ROS) in reaction system were studied by oxidation and extraction photometry. Experimental results showed that the amounts of superoxide anion radical (·O(2)(-)) and hydroxyl radical (·OH) were significantly more than that of singlet oxygen ((1)O(2)) in the presence of LVFX under ultrasonic irradiation.

[Preparation of GSH capped CdSe/CdS core-shell QDs and labeling of human T-lymphocyte].

Two kinds of L-glutathione capped highly fluorescent CdSe/CdS core-shell quantum dots (QDs) emitting green and orange fluorescence at 350 nm excitation were firstly prepared by an aqueous approach and used as fluorescent labels, to link mouse anti-human CD3 which was expressed on human T-lymphocyte. UV-Vis absorption and fluorescence emission spectra of the as-prepared CdSe/CdS core-shell QDs were studied. Compared with the CdSe QDs, a remarkable enhancement in the emission intensity and a red shift of emission wavelength of CdSe/CdS core-shell QDs was observed for the two kinds of QDs emitting green and orange fluorescence. The TEM results showed that the as prepared CdSe and CdSe/CdS QDs dispersed well in aqueous solution, and their shape was approximately spherical, and the CdSe/CdS QDs nano particles emitting green fluorescence are of about 5 nm in diameter. The two kinds of CdSe/CdS QDs were linked with mouse anti-human CD3 to image human T-lymphocyte. The fluorescent microscopical images of human T-lymphocyte labeled with CdSe/CdS QDs-CD3 and FITC-CD3 demonstrated that the fluorescent CdSe/CdS QDs exhibited much better photo stability and brighter fluorescence than FITC, showing a good application potential in the immuno-labeling of cells.

[Determination of DNA using Eu-PPA as fluorescence probe by time-resolved fluorescence].

In the Tris-HCl buffer solution, europium ion combined with pipemidic acid (PPA) to form a Eu-PPA complex. The fluorescence intensity was dramatically enhanced when herring sperm DNA was added in the Eu-PPA system. Furthermore, the fluorescence intensity was increased linearly with the concentrations of added DNA within a proper range. Based on this, a simple new method for the determination of herring sperm DNA was developed. Time-resolved fluorescence excitation and emission spectra and the fluorescence lifetime of the system were studied in detail and compared with that from conventional fluorescence method. The experimental results indicated that the time-resolved fluorescence method was superior over the conventional fluorescence method. The reaction conditions, measurement parameters and the adding order of reactants were optimized. The best concentration of both europium ion standard solution and PPA standard solution was 1.00 x 10(-5) mol x L(-1) in the Tris-HCl buffer solution of 0.005 mol x L(-1) with the optimal pH value of 7.2. A detection limit (3 s) of 0.03 mg x L(-1) was obtained with a RSD of 0.3% (4.0 mg x L(-1), n = 11). The linear relationship between deltaI = 89.58c (mg x L(-1)) +0.920 5 and the regression factor of 0.999 6 was obtained in the range of 0.1-6 mg x L(-1). This method was applied to the determination of DNA in synthetic samples. The results and recoveries of spiked standard solution in the sample were satisfied.

Immunoassay of goat antihuman immunoglobulin G antibody based on luminescence resonance energy transfer between near-infrared responsive NaYF4:Yb, Er upconversion fluorescent nanoparticles and gold nanoparticles.

Near-infrared (NIR) light can penetrate biological samples and even tissues without causing sample damage and avoid autofluorescence from biological samples in fluorescence detection. Thus, a luminescence resonance energy transfer (LRET)-based immunoassay that can be excited by NIR irradiation is a promising approach to the analysis of biological samples. Here we demonstrate the use of NIR-to-visible upconversion nanoparticles (UCNPs) as an energy donor, which can emit a visible light upon the NIR irradiation, and gold nanoparticles (Au NPs) as an energy acceptor, which can absorb the visible light emitted from the donor, to develop a sandwich-type LRET-based immunoassay for the detection of goat antihuman immunoglobulin G (IgG). Amino-functionalized NaYF(4):Yb, Er UCNPs and Au NPs were first prepared and then conjugated with the human IgG and rabbit antigoat IgG, respectively. The NIR-excited fluorescence emission band of human IgG-conjugated NaYF(4):Yb, Er UCNPs (lambda(max) = 542 nm) partially overlaps with the visible absorption band of the rabbit antigoat IgG-conjugated colloidal Au NPs (lambda(max) = 530 nm), satisfying the requirement of spectral overlap between donors and acceptors for LRET. A LRET system was then formed when goat antihuman IgG was added to a mixture of human IgG-modified NaYF(4):Yb, Er UCNPs (donor) and rabbit antigoat IgG-modified Au NPs (acceptor). The sandwich-type immunoreactions between the added goat antihuman IgG (primary antibody) and the two different proteins (antigen and secondary antibody on the surface of the donors and acceptors, respectively) cross-bridge the donors and acceptors and thus shorten their spacing, leading to the occurrence of LRET from UCNPs to Au NPs upon NIR irradiation. As a result, the quenching of the NIR-excited fluorescence of the UCNPs is linearly correlated to the concentration of the goat antihuman IgG (in the range of 3-67 microg x mL(-1)) present in the system, enabling the detection and quantification of the antibody. Such sandwich-type LRET-based approach can reach a very low detection limit of goat antihuman IgG (0.88 microg x mL(-1)), indicating that this method is applicable for the trace protein detection. This approach is expected to be extended to the detection of other biological molecules once the donor and acceptor nanoparticles are modified by proper molecules that can recognize the target biomolecules.

Immunolabeling and NIR-excited fluorescent imaging of HeLa cells by using NaYF(4):Yb,Er upconversion nanoparticles.

Upconversion fluorescent nanoparticles can convert a longer wavelength radiation (e.g., near-infrared light) into a shorter wavelength fluorescence (e.g., visible light) and thus have emerged as a new class of fluorescent probes for biomedical imaging. Rare-earth doped beta-NaYF(4):Yb,Er upconversion nanoparticles (UCNPs) with strong UC fluorescence were synthesized in this work by using a solvothermal approach. The UCNPs were coated with a thin layer of SiO(2) to form core-shell nanoparticles via a typical Stober method, which were further modified with amino groups. After surface functionalization, the rabbit anti-CEA8 antibodies were covalently linked to the UCNPs to form the antibody-UCNP conjugates. The antibody-UCNP conjugates were used as fluorescent biolabels for the detection of carcinoembryonic antigen (CEA), a cancer biomarker expressed on the surface of HeLa cells. The successful conjugation of antibody to the UCNPs was found to lead to the specific attachment of the UCNPs onto the surface of the HeLa cells, which further resulted in the bright green UC fluorescence from the UCNP-labeled cells under 980 nm near-infrared (NIR) excitation and enabled the fluorescent imaging and detection of the HeLa cells. These results indicate that the amino-functionalized UCNPs can be used as fluorescent probes in cell immunolabeling and imaging. Because the UCNPs can be excited with a NIR light to exhibit strong visible fluorescence and the NIR light is safe to the body and can penetrate tissue as deep as several inches, our work suggests that, with proper cell-targeting or tumor-homing peptides or proteins conjugated, the NaYF(4):Yb,Er UCNPs can find potential applications in the in vivo imaging, detection, and diagnosis of cancers.

[Synthesis and characterization of NaYF4 : Yb, Er upconversion fluorescent nanoparticles via a co-precipitation method].

Monodisperse NaYF4 : Yb, Er upconversion fluorescent nanoparticles were firstly synthesized via a co-precipitation method in the presence of diethylenetriamine pentoacetic acid (DTPA). The nanoparticles were characterized by using of X-ray diffraction (XRD), transmission electron microscope (TEM), fluorescence (FL) spectrum, and thermogravimetry-differential scanning calorimetry (TG-DSC) analysis. The as-prepared nanoparticles were uniform, and their size could be controlled in a range of 20 to 120 nm by varying the amount of DTPA. During the precipitation reaction, DTPA molecules could form a complex with the rare earth ions, and then the rare earth ions were released slowly to react with F- ions, which slowed down the speed of the reaction. In addition, DTPA molecules could also be capped on surface of the growing nanoparticles, which prevented the nanoparticles from aggregation. After annealing, the nanoparticles were transformed from cubic phase to hexagonal phase, and their upconversion fluorescence intensity was enhanced remarkably. The synthesis conditions including the amount of chelating agents and temperature for annealing, which showed great influence on the size, phase and upconversion fluorescence intensity of the nanoparticles, were also discussed. It was confirmed by XRD and TG-DSC analysis that the presence of DTPA suppressed the cubic-to-hexagonal phase transition of the nanoparticles. However, while the small nanoparticles were obtained with well control, the annealed crystals synthesized by adding DTPA could still emit strong fluorescence under a low exciting power, which could well fulfill the demand for bio-labeling. These nanoparticles are envisioned to find potential applications in biological detections.

[Determination of trace copper (II) based on fluorescence quenching of NaGdF4 : Eu nanoparticles].

Water-soluble NaGdF4 : Eu fluorescent nanoparticles modified by citrate were synthesized by hydrothermal method with stable fluorescent properties. It was found that the fluorescence of the solution of as-prepared particles could be quenched by Cu2+, and thus a new mathod to determine trace Cu2+ using NaGdF4 : Eu as fluorescent probe was established. A pH 10.0 and the concentration 1.0 x 10(-3) mol x L(-1) of NaGdF4 : Eu were selected for measurement Besides, the effect of some foreign ions on the fluorescence signals was investigated and the interference of Fe3+ was found, which was eliminated by adding triethanolamine. The regression equation of standard curve was I = 532-0.685c with the correlation coefficient of -0.998 4 when the concentration of Cu2+ was in the range of 3.33 x 10(-6) -1.33 x 10(-4) mol x L(-1), and the detection limit of 8.9 x 10(-7) mol x L(-1) and a RSD of 0.62% for 11 replicates of a 6.0 x 10(-5) mol x L(-1) Cu2+ solution were obtained, which suggest a wide linear analytical range, high sensitivity and high precision. Analytical applicability of the particles was demonstrated by tea sample analysis and the results of Cu2+ determination were in good agreement with those obtained by atomic absorption spectrometry. The reason for fluorescence quenching by Cu2+ can be explained in terms of combination of Cu2+ with citrate on the surface of NaGdF4 : Eu particles leading to a change in surface structure and the composition.

[Synthesis and absorption spectra properties of Au-Ag alloy nanoparticles using gallic acid as reductant].

Gold-silver alloy nanoparticles with a homogeneous size distribution and good stability were synthesized in aqueous solution by one-step reduction with gallic acid as reductant in the absence of other stabilizers for the first time. The absorption spectra of as prepared gold-silver alloy nanoparticles under different reaction temperatures and with various gold-silver mole ratios were studied. The absorption spectra exhibit only one single peak with the maximum wavelength located between the absorption peaks of Au nanoparticles and Ag nanoparticles, however, the absorption spectrum of the physical mixtures of Au nanoparticles and Ag nanoparticles exhibits two absorption peaks coming from their corresponding monometallic metal nanoparticles, suggesting primarily the formation of the alloy nanoparticles. The maximal absorption peaks of alloy nanoparticles showed gradually a blue-shift with the rising of reaction temperature companying with the increase in absorbance and the narrowing of peak shape. The maximum absorption wavelengths of alloy nanoparticles showed a red-shift with increasing Au/Ag molar ratio in a linear fashion, further indicating the formation of alloy nanoparticles. HRTEM images showed that the as-prepared alloy nanoparticles with Ag/Au molar ratio of 1:1 are close to sphere in shape, homogeneous in size distribution and without capping phenomenon. EDX analysis suggested the present of Au and Ag in individual nanoparticles, and the Au/Ag mole ratio value of a sample with a nominal element composition was found to be close to the nominal value.

A glass microfluidic chip for continuous blood cell sorting by a magnetic gradient without labeling.

This paper presents a microfluidic chip for highly efficient separation of red blood cells (RBCs) from whole blood on the basis of their native magnetic properties. The glass chip was fabricated by photolithography and thermal bonding. It consisted of one inlet and three outlets, and a nickel wire of 69-microm diameter was positioned in the center of a separation channel with 149-microm top width and 73-microm depth by two parallel ridges (about 10 microm high). The two ridges were formed simultaneously during the wet etching of the channels. The nickel wire for generating the magnetic gradient inside the separation channel was introduced from the side of the chip through a guide channel. The external magnetic field was applied by a permanent magnet of 0.3 T placed by the side of the chip and parallel to the main separation channel. The RBCs were separated continuously from the 1:40 (v/v) diluted blood sample at a flow rate in the range 0.12-0.92 microL/min (9-74 mm/min) with the chip, and up to 93.7% of the RBCs were collected in the middle outlet under a flow rate of 0.23 microL/min. The cell sedimentation was alleviated by adjusting the specific density of the supporting media with bovine serum albumin. Quantum dot labeling was introduced for visual fluorescence tracking of the separation process. The uneven distribution phenomenon of the blood cells around the nickel wire was reported and discussed.

[Applications of quantum dots to biological probes].

Quantum dots (QDs) have shown unique optical properties compared with traditional organic dyes. Now, more and more attention has been paid to them, especially in the fields of biological medicine and materials. Much work about QDs application in biology has been done by many researchers. In resent years, QDs have been widely used as biological probes. By observing the conjugation site between QDs and target molecules or tracking the movement of QDs in live cells, some information about transferring signals mechanism may be obtained, therefore, offering apparent evidence for controlling cell's growth and finding the factors in the deterioration of cancer. In the present paper, interactions among macro molecules are introduced with fluorescence resonance energy transfer (FRET), fluorescent labeling of biological macro molecules, labeling and imaging of cells and tissues, and imaging in vivo. Furthermore, some developments and problems in application are summarized. Thirty seven references are cited.

[Study of autofluorescence spectra of protoporphyrin IX in human serum].

The fluorescence spectra of protoporphyrin IX (PPIX) solutions and human serum samples were measured and analyzed under physiological conditions. The experimental results showed that the fluorescence of PPIX in human serum was mainly derived from PPIX-serum albumin complex. Moreover, the effects of serum albumin and PPIX on the PPIX emission fluorescence were also investigated. Compared with pure PPIX solution, not only a red-shift of PPIX fluorescence peak was found for PPIX+albumin solution, but also albumin had a fluorescence enhancement effect on protoporphyrin IX. For the mixture of PPIX+albumin, with the increase of PPIX the wavelength of the PPIX emission peak will increased a little when its concentration was less than 0.8 x 10(-5) mol x L(-1), but was nearly invariable when its concentration was more than 0.8 x 10(-5) mol x L(-1).

[Spectroscopy study of aqueous CdTe quantum dots synthesized by microwave irradiation method].

Water-soluble CdTe nanocrystals capped with cysteamine were synthesized rapidly in aqueous solution by microwave irradiation with controllable temperature. Absorption and fluorescence spectra showed that these prepared CdTe quantum dots had good optical properties. The structure and diameter were characterized by the transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The effects of heating temperature, irradiation time and the concentrations of cysteamine on the growing velocity of CdTe QDs synthesized were also investigated. With the increase in the temperature and concentration of cysteamine, the nanoparticles grow faster, and for a longer reaction time, the maximum emission wavelength of the nanoparticles shows a red shift. Compared with the conventional aqueous synthesis, the microwave irradiation method showed some advantages such as the rapid velocity, good dispersibility and uniformity, narrow FWHM (full width at half maximum) and high quantum yield.

[Determination of As, Pb, Sn, Sb and Bi in high temperature iron and nickel-based alloy by graphite furnace atomic absorption spectrometry combined with liquid-liquid extraction].

A method was developed for the determination of As, Pb, Sn, Sb and Bi in high temperature iron and nickel-based alloy by graphite furnace atomic absorption spectrometry combined with liquid-liquid extraction. These elements formed complexes with I- ions and were subsequently extracted into MIBK to be separated from matrix elements. The effects of remnant matrix elements were studied in detail. Meanwhile, the interferences of other elements, such as W, Nb and Ta, were eliminated with masking method. The recovery rates for As, Pb, Sn, Sb and Bi are in the range of 93%-99%, and the relative standard deviations are from 8.8% to 12%.