Controlled assembly of gold and rare-earth upconversion nanoparticles for ratiometric sensing applications

In this paper, the Au nanoparticles and rare-earth (RE) upconversion nanoparticles (NPs) were respectively synthesized by using polyelectrolyte as the capping agents. Since the synthesized Au NPs and RE NPs had the similar size and surface conditions, Their mixture were employed in a pH sensing application. Benefited from the good spectral overlap between the RE upconversion emission bands and pH-tunable surface plasmon bands of the Au NPs, the pH-induced manipulation of green-to-red emission intensity ratio of the upconversion fluorescence was achieved in the Au-RE mixture. The results demonstrate a rapid ratiometric approach for pH sensing, which is more efficient than traditional sensing methods that depend on single intensity-based responses to analytes.     

Synthesis and characterization of Au@Pt nanoparticles

Aucore-Ptshell （Au@Pt） nanoparticles were synthesized at room temperature by reducing K2PtCl6 with hydrogen in the solution containing Au colloids and polyvinylpyrrolidone （PVP）. The particles obtained were characterized with UV-Vis, TEM and XPS techniques. UV-Vis spectra show that the surface plasmon absorption feature of Au colloids is significantly reduced with increasing the amount of reduced Pt. TEM images that the metals are found always appear as spherical nanoparticles and their sizes grow apparently due to the reduction of PtCl6^2- ions, indicating that Pt is deposited from solution onto Au particle surface and forms a Pt-layer with uniform thickness. In the XPS spectra, the signals of Au metal decrease due to the reductive deposition of Pt on the surface of the Au colloids. UV-Vis and XPS data are consistent in showing that when the amount of Pt in the AuPt colloids is increased to reach an overall atomic ratio of Pt/Au=2, the Pt deposits form a shell covering completely the surface of Au particles, demonstrating the core-shell structure of the synthesized AuPt particles.     

A near-infrared fluorescent probe for fluorine ions and its application in the imaging of HepG2 cells

In this study, we have designed and synthesized a new near-infrared (NIR) fluorescent probe (BODIPY-Se) to detect fluorine ions (F-) using a B-Se bond to connect the fluorescent dye BODIPY and benzotrifluoride. The probe exhibited a highly selective fluorescence response to F- with a detection limit of 7.4×108 mol/L. The excitation and emission spectra of the probe in the NIR region avoid background fluorescence interference present in biological systems. The fluorescent imaging of HepG2 cells demonstrated ...     

Study of the interaction of DNA and histones by spin-stretching and droplet evaporation

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, DNA-histone complexes are stretched on a hydrophobic polymethyl methacrylate (PMMA) surface and observed directly. We have developed a new method to stretch single DNA-histone complexes, termed spin-stretching. The results show that the histones markedly enhance DNA binding to the PMMA surface. DNA winds around the histones and therefore decreases in length. The number of histones that bind to each DNA molecule is found to correlate with the histone concentration. The combed DNA-histone complexes are found to depend on two factors: the binding force on the surface and the centrifugal force at its local position. Na+ ions should compete with histones for binding to DNA; however, the observed competitive binding effect of Na+ ions at low concentrations was negligible.     

Progress in modifications and applications of fluorescent dye probe

This review summarizes the labeling technology and applications of fluorescent dye probe in biology, especially the characteristics, modifications and applications of cyanine dyes. Based on the currently available modification methods of fluorescent dye probe, we discuss the studies of enhancing the water-solubility,improving the degree of biocompatibility and target-labeling, increasing the sensitivity and decreasing the toxicity of fluorescent dye. We also give a brief introduction on the modification method, that the fluorescent dye is directly introduced onto cell surfaces by amine derivatives or azides to intensify the transferring information of aberrant cells. We suggest that fluorescent dye modified with chitosan oligosaccharide can obviously increase the degree of biocompatibility and target-labeling, and decrease the degree of toxicity.     

Detection and analysis system for hybridization images of lab-in-a-tube microarray

A lab-in-a-tube microarray system is developed for sample inspection and signal detection by fabricating a fiat transparent window cap of the Eppendorf tube. The oligonucleotide microarray is immobilized on the inner surface of the cap. A small vessel is placed in an Eppendorf tube for storing hybridization solutions. With the microarray system, the full biochemical processes, including gene fragment amplification, fluorescence labeling, hybridization, and fluorescence detection, have been performed in the sealed tube without opening the cap. The images are obtained from a fluorescence microscope and captured by a CCD, and the data are transported to a computer through the universal serial bus （USB）. After noise reduction, signal intensity is determined from hybridization image and the presence of gene fragments is identified. The final data output includes sample information, process steps, and hybridization results. A lab-ina-tube microarray system for detecting ten respiratory viruses at a single detection is designed. High detection throughput and accuracy have been demonstrated with the system.     

Dissolution behavior and dissolution mechanism of palygorskite in HCl solution

The 1 mol/L, 3 mol/L and 5 mol/L HCl solutions were employed to leach two palygorskites with different trioctahedral contents in their crystal structure for different period of time. The results of the dissolution experiments show that the dissolution process could be divided into three steps, and that this dissolution behavior can be attributed to its higher Mg2+ content, and is restricted by the extraction behavior of Si4+. The preferential extraction for Mg2+ promotes the extraction behavior of Si4+ from Si-O framework. Because the Si4+ in the form of amorphous SiO2 is adsorbed onto the surface of palygorskite fibre, the reaction between palygorskite and acid is obstructed. With the elapsing of time, or the increasing of the acid concentration, the amorphous SiO2 flocculates, and then the channels of chemical reaction are reopened. The ratio value of Mg2+/(Fe3++Al3+) in leaching solution tends to a fixed value, showing that the acid attacks not only the surface but also the structural channels. There are no obvious three steps observed during the acid attack on the palygorskite with a lower trioctahedral content. The differential behavior for two palygorskites is discussed.     

New Synthesis of Pt-Ru Nanoparticles on Surface Modified Carbon Vulcane XC-72 as an Effective Catalyst for Direct Methanol Fuel Cell

1 Results Pt-Ru nanoparticles are synthesised on the surface oxidized carbon Vulcane XC-72 as catalyst support by chemically anchoring Pt and Ru onto the surface of modified carbon vulcane XC-72 (by refluxing in 70% HNO3 at 120 ℃ for 12 h to introduce surface functional groups) .The nanoparticles of Pt and Ru are synthesized by reduction of H2PtCl6 and K4Ru(CN)6 with sodium borohydride in a 5.5 buffer solution of sodium citrate,the complexation of citrate with metal ions is beneficial to the formation of nanoparticles.The electro-oxidation of liquid methanol as a thin layer of this catalyst on glassy carbon electrode is investigated at room temperature by cyclic voltammetry.The results demonstrate that the prepared catalyst is more active than ordinarily carbon-supported Pt and Pt-Ru catalysts[1,2].TEM images and SEM are also carried out.     

Preparation and Adsorption Ability of Polysulfone Microcapsules Containing Modified Chitosan Gel

Chemically modified chitosan beads containing polyethyleneimine （PEI） were prepared to improve the metal ion adsorption capacity of the chitosan beads and their mechanical stability and to limit their biodegradability. The modified beads were encapsulated with the polymer material polysulfone by a novel surface coating method named the emulsion phase inversion method. The adsorption properties of the modified beads and the microstructures of the polysulfone coating layer were then analyzed. The experimental results showed that the PEI was successfully linked onto the chitosan beads. The density of the -NH2 groups in the modified beads was significantly increased, while the water content was reduced. The coating layer thickness was about 200 pm. The modified chitosan gel beads had excellent Cu（ll） adsorption capacity, with a maximum Cu（ll） adsorption capacity 1.34 times higher than that of the unmodified beads. The results show that even with the polysulfone coating the adsorption kinetics of the modified beads is still better than those of the unmodified beads. The modifications improve the mass transfer performance of the chitosan beads as well as the bead stability.     

罗丹明6G与罗丹明6G酰肼测汞的对比研究

以罗丹明6G(R6G)为原料合成了罗丹明6G酰肼(R6GH),并通过荧光法考察了R6G和R6GH酰肼选择性识别金属离子、适合的缓冲溶液体系、最佳缓冲溶液pH及浓度、R6G和R6GH的浓度、Hg~(2+)的浓度以及阳离子的干扰等七个因素的影响。实验确定了R6G测定Hg~(2+)的最佳条件为:0.01mol/L醋酸缓冲体系(pH=4.60),R6GH测定Hg~(2+)的最佳条件为:0.005 mol/L醋酸缓冲体系(pH=4.60)。通过14种阳离子的干扰实验发现,阳离子对R6G测定Hg~(2+)的影响大于对R6GH测定Hg~(2+)的影响。实验结果表明:R6GH比R6G能更好的识别Hg~(2+),最低检出限为5.0×10~(-12) mol/L。     

Preparation of fluorescent hyperbranched polymer materials by end-capping approach

Two kinds of novel fluorescent hyperbranched polymers were synthesized by the end-capping approach. The fluorescent hyperbranched polyether (FPEOTM) was obtained by end capping the hyperbranched poly(hydroxyl ether) (PEOTM) with guest molecules N,N-dimethylaminobenzaldehyde (DMABA). In addition, in the presence of triethylamine, the hyperbranched polysulfone-amine with terminal double bonds (HPSA) was synthesized by polyaddition of a new AB₂ type monomer (SAP, sulfone amine piperazine) at 40°C for 60 h in chloroform solution. Then the fluorescent hyperbranched polysulfone-amine (FHPSA) was prepared by addition of guest molecules N, N-dimethylaminoanilines (DMAA) with the terminal double bonds of HPSA. The two resulting polymers fluoresce yellow-green color in both solid and solution states. The maximum emission wavelength is (460±10) nm and (470±10) nm, respectively. A novel “complex quenching effect” for hyperbranched polymer was observed. The fluorescence can be quenched by transition metal cations such as Ag⁺, cu²⁺ and Fe³⁺, while alkali and alkaline earth metal cations almost have no influence on the fluorescence intensity.     

Label-free selective sensing of Pb2+ lead(II) sensors based on the aggregation of a pyrene fluorescent probe

In the present work, we report a label-free fluorescence turn-on approach for the sensitive and selective sensing of Pb²⁺. Pyrene with one positive charge was used as the fluorescent probe, and thrombin aptamer (TBA), which was a G-rich oligonucleotide, was employed to form G-quadruplex with lead(II). When TBA and Pb²⁺ were mixed with lead(II) in an aqueous solution, it was folded into a stable G-quadruplex. Subsequently, a single-stranded nucleic acid-specific nuclease S1 was added. The G-quadruplex stabilized by Pb²⁺ lead(II) had markedly a significant resistant ability to nuclease S1 digestion. However, in the absence of Pb²⁺ lead(II), no quadruplex or less stable quadruplex was formed and TBA was digested by nuclease S1 in 3 min under the optimized experimental conditions. Finally, pyrene probe was mixed with oligonucleotide in Pb²⁺ lead(II). Electrostatic interactions between oligonucleotide (a polyanion) and the probe induced the aggregation of the probe, which in turn produced strong emission of the strong pyrene excimer emission. The intensity of the induced excimer emission was directly proportional to the amount of Pb²⁺ added. Our approach shows good selectivity and sensitivity for the detection of Pb²⁺ with a limit of detection limit as low as 800 nmol/L.     

Spectroscopic investigation of the interactions between gold nanoparticles and bovine serum albumin

The interactions between bovine serum albumin(BSA) and gold nanoparticles(AuNPs) ,and the conformational changes of BSA induced by this interaction,were investigated by UV-visible absorption spectroscopy,fluorescence spectroscopy,and Fourier transform infrared in combination with attenuated total reflection spectroscopy(ATR-FTIR) .The critical adsorption density for preventing AuNP aggregation in 0.1 mol/L phosphate buffered saline(pH 7.2) was 23 BSA molecules per gold particle or 3.8×1012 BSA molecules/cm2.BSA bound to the AuNPs with high affinity(binding constant Ks=7.59×108 L/mol) ,and the intrin-sic fluorescence of BSA was quenched by the AuNPs in accordance with the static quenching mechanism.Both fluorescence spectroscopy and ATR-FTIR showed that AuNPs induced conformational changes in BSA,which resulted in it becoming less compact and increased the polarity of the microenvironment around the tryptophan residue Trp-212.     

基于纳米金/氮掺杂石墨烯的电化学适配体传感器检测汞离子的研究

以离子液体修饰碳糊电极(CILE)为工作电极,利用直接滴涂法将氮掺杂石墨烯(NG)固定于CILE表面后,利用恒电位法将纳米金(AuNPs)沉积在电极表面,再通过自组装法将适配体(aptamer)固定在AuNPs/NG/CILE表面制得一种新型电化学适配体传感器(aptamer/AuNPs/NG/CILE)。利用示差脉冲伏安法(DPV)对修饰电极进行表征,建立了汞离子(Hg~(2+))的电化学适配体检测方法,线性范围为1.0×10~(-9)～3.0×10~(-7)mol/L,检测限为3.33×10~(-10)mol/L。     

Spectrofluorimetric determination of tetracycline using Eu3+ chelation and cetyltrimethylammonium bromide

The fluorescence of tetracycline was greatly enhanced by chelation with Eu³⁺ in Tris-HCl buffer (pH8.5). The addition of cetyltrimethylammonium bromide, a cationic surfactant, further enhanced the fluorescence of tetracycline-Eu³⁺ chelates. This spectrofluorimetric method for the determination of tetracycline yielded a linear responses in the range of 10 nmol/L–10 μmol/L. The detection limit was 5 nmol/L (or 2.22 ng/mL). The recovery of tetracycline spiked in serum at levels of 1 and 0.09 μg/mL was 97.9% and 97.8%, respectively. This method is fast, sensitive and suitable for the determination of tetracycline in biological specimens. Foundation item: Supported by the National Natural Science Foundation of China Biography: Huang Zu-yun (1963-), male, Ph D.     

Voltammetric detection of nanomolar levels of hypoxanthine in the presence of copper (II) at glassy carbon electrode

Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper (II) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine-Cu⁺ is shown to be adsorbed on the electrode surface in the presence of an excess of copper(II). After accumulation period, hypoxanthine-Cu⁺ was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(I) to Cu(II) was measured. A linear calibration curve in the range of 5 nmol/L-1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained. Supported by State Key Laboratories of Transducer Technology, Chinese Academy of Sciences Hu Shengshui: born in 1946, Associate professor     

壳聚糖絮凝剂处理废水中的Ag+

研究了利用壳聚糖絮凝剂絮凝除Ag的方法.考察了pH值、离子溶液浓度、絮凝剂用量以及絮凝时间对去除率的影响.实验结果表明:壳聚糖絮凝除银的适宜pH为7~8;当pH=7~8时,用壳聚糖吸附银离子,水样银质量浓度低于20 mg/L时,除银率达100%.即使高浓度含银水样,其除银率也在99.9%以上;絮凝除银时间4 h为宜,其去除率达99.98%;壳聚糖的加入量过多过少都会影响除银效果.分析了壳聚糖絮凝除银的机理.     

Polymerization of fluorescent analogue of plant actinin vitro andin vivo

Maize pollen actin has been labeled with Oregon Green 488 iodoacetamide. A yield of 3 mg fluorescent actin analogue has been obtained from 10 mg of maize pollen actin, which is 99% in purity and the dye/protein ratio is 72%. In the presence of Mg²⁺ and K⁺, the fluorescent actin analogue polymerized into filamentsin vitro. Green fluorescent filaments were observed when the fluorescent actin was introduced into living plant cells by microinjection, indicating that the fluorescent actin analogue functions similarly to the native actin.