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  • An aptamer for recognizing the transmembrane protein PDL-1 (programmed death-ligand 1), and its application to fluorometric single cell detection of human ovarian carcinoma cells
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-02
    Rezvan Yazdian-Robati, Mohammad Ramezani, Mostafa Khedri, Najmeh Ansari, Khalil Abnous, Seyed Mohammad Taghdisi

    Programmed death-ligand 1 (PD-L1) is overexpressed in a variety of cancer cells. Using protein SELEX, aptamers against PD-L1 were identified. After 10 rounds of selection, 2 aptamers (Apt5 and Apt33) were chosen. Due to the higher specificity and affinity of Apt5 for PD-L1, this aptamer was characterized in detail. The ATTO 647 N–labeled aptamer readily internalizes into PD-L1 positive A2780 cells where it can detect human ovarian carcinoma. Hence, fluorometry provides a rapid and sensitive quantitative tool for the detection of these cancer cells with limit of detection (LOD) as low as 10 cells.mL−1 and linear response in the range between 50 and 1000 cells.mL−1. In our perception, the Apt 5 aptamer holds great promise for use in cancer diagnosis and therapy.

    更新日期:2017-09-13
  • Aptamer-based fluorometric determination of ATP by using target-cycling strand displacement amplification and copper nanoclusters
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-06
    Yu-Min Wang, Jin-Wen Liu, Lu-Ying Duan, Si-Jia Liu, Jian-Hui Jiang

    A fluorescence aptasensor is described that combines target-cycling strand displacement amplification (TCSDA) and synthesis of copper nanoclusters (CuNCs) templated with double-stranded DNA (dsDNA). Specifically, the detection scheme was applied to the determination of adenosine-5′-triphosphate (ATP) via target-induced structure switching design. The binding of an aptamer hairpin probe (AP) to ATP induces a structural switch from a hairpin shape to an open conformation. This facilitates hybridization with a primer and triggers a TCSDA reaction. This amplification step produces a large quantity of dsDNA that can directly act as a template for the synthesis of fluorescent CuNCs, thereby producing a strong red fluorescence (with excitation/emission maxima at 340/598 nm) that can be used to quantify ATP. The assay has a dynamic range that extends over 4 decades (from 0.01 nM to 100 nM) and a 5 pM detection limit. Conceivably, this detection scheme is applicable to numerous other analytes for which suitable aptamers are available.

    更新日期:2017-09-13
  • A magnetic MoS 2 -Fe 3 O 4 nanocomposite as an effective adsorbent for dispersive solid-phase microextraction of lead(II) and copper(II) prior to their determination by FAAS
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-26
    Neda Baghban, Erkan Yilmaz, Mustafa Soylak

    The authors describe the preparation of a nanocomposite (mag-MoS2-Fe3O4) that was prepared from molybdenum disulfide (MoS2) and magnetic Fe3O4 nanoparticles by a hydrothermal method in an inert atmosphere. The composite is shown to be a viable magnetic adsorbent for dispersive solid phase microextraction of lead(II) and copper(II) ions from water and plant samples. The nanocomposite was characterized by FT-IR, Raman spectroscopy, XRD, SEM, and BET methods. The factors affecting the extraction recovery of the analytes, including the pH value, type of dispersive solvent, sample volume, type and volume of eluent solution, and interfering ions, were optimized. Flame atomic absorption spectrometry was then used for quantitation. Figures of merit of this method include a preconcentration factor of 50 for lead(II) and 35 for Cu(II), LODs of 3.3 μg·L−1 for lead(II) and of 1.8 μg·L−1 for Cu(II), and RSDs of 4.9 and 1.5%, respectively. The method was used to preconcentrate the analytes from plant and water samples prior to their determination by FAAS. It was then validated by analyzing certified reference materials (water and plant), and this resulted in good accuracy.

    更新日期:2017-09-13
  • A glassy carbon electrode modified with reduced graphene oxide for sensitive determination of bumetanide in urine at levels required for doping analysis
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-14
    Felipe Fantinato Hudari, Maria Valnice Boldrin Zanoni

    The dopant bumetanide (BMT) was banned by the World Anti-Doping Agency. The authors describe a voltammetric sensor for the determination of BMT in urine that is based on the use of a glassy carbon electrode modified with reduced graphene oxide (GCE/rGO). The GCE/rGO was prepared by electrodeposition from a solution of GO. The oxidation of BMT occurs best at +0.75 V in the GCE/rGO with an approximately 13-fold gain in the anode current compared to a conventional GCE. The oxidation mechanism was investigated by means of electrolysis, while the analysis of the products was carried out via the LC–MS/MS. Under optimized conditions (scan rate 100 mV s−1; pH 4.0; accumulation time 25 s) and by using linear sweep adsorptive stripping voltammetry, the response covers the 0.26 to 50 μmol L−1 BMT concentration range. The detection limit is 75 nmol L−1. The sensor was successfully applied and validated by LC–MS/MS analysis of spiked urine sample.

    更新日期:2017-09-13
  • Nanographite-based fluorescent biosensing of Salmonella enteritidis by applying deoxyribonuclease-assisted recycling
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-17
    Qizhi He, Huaiqing Luo, Liang Tang, Jia Liu, Keke Chen, Qingfang Zhang, Yi Ning

    The authors describe a low-cost and sensitive method for the fluorometric determination of Salmonella enteritidis (S. enteritidis). It is based on the use of nanographite (NG) as a quencher of fluorescence, and on cyclic signal amplification by using deoxyribonuclease I (DNase I). The probe containing a capture probe and two short sequences (probe 1 and probe 2) labeled with carboxyfluorescein (FAM) are used as the signal probe that is adsorbed on the surface of NG via p-stacking interactions. Adsorption results in quenching of the fluorescence of FAM. If S. enteridis is introduced, fluorescence is restored due to the displacement of the probe from the surface of the NG due competitive binding. The signal is considerably amplified by applying DNase I-mediated target recycling. The assay has a linear response that covers the 1 to 50 nM concentration range, with a 0.5 nM lower limit of detection (LOD). A milk sample spiked with S. enteritidis was analyzed and the detection limit is as low as 50 colony-forming units (CFU) per mL. Accordingly, this biosensor is highly sensitive and selective but also cost-effective. Conceivably, the detection scheme may be extended to the detection of other biomolecules.

    更新日期:2017-09-13
  • A zinc(II) benzenetricarboxylate metal organic framework with unusual adsorption properties, and its application to the preconcentration of pesticides
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-03
    Xuemei Wang, Xiaomin Ma, Huan Wang, Pengfei Huang, Xinzhen Du, Xiaoquan Lu

    The authors describe a zinc(II) benzenetricarboxylate (Zn-BTC) based metal-organic framework (MOF) with chrysanthemum-like structure, and its application to the adsorption of pesticides from real water samples. The Zn-BTC MOF was characterized by XRD, TGA, SEM, nitrogen adsorption-desorption analysis and FT-IR spectroscopy. The MOF was used in dispersive solid-phase extraction of six aromatic pesticides from various wastewater samples prior to their quantification by HPLC. Extraction times, extraction temperature, amount of adsorbent, and oscillation rate were optimized. Under the optimal conditions, the method has relative standard deviations (RSDs) of 6.1–10.1%, and good linearity (correlation coefficients higher than 0.9974). The LODs and LOQs for seven pesticides are found to be 0.20–1.60 μg·L−1 and 0.66–5.28 μg·L−1, respectively. The RSDs of within batch extraction are 1.6–9.5% and 3.9–12%.

    更新日期:2017-09-13
  • A nanocrystalline metal organic framework confined in the fibrous pores of core-shell silica particles for improved HPLC separation
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-07
    Qishu Qu, Yang Si, Han Xuan, Kehua Zhang, Xiaoming Chen, Yi Ding, Shaojie Feng, Han-Qing Yu

    A hybrid material was prepared from a metal-organic framework (MOF) and core-shell silica by using a kinetic controlling approach. The nanocrystalline MOF (HKUST-1) was prepared from 1,3,5-benzenetricarboxylate and copper(II) by tuning the reaction rate via the fraction of ethanol in the solvent. After the reaction rate was reduced to a certain degree, the pore surface would be well covered with Cu(II), which initiated the formation of a nanocrystalline HKUST-1. The resulting hybrid material was packed into a stainless-steel column (4.6 × 150 mm) and used as a stationary phase in high performance liquid chromatography. SiO2@dSiO2-HKUST-1 combined the merits of the high separation performance of the core-shell particles and the unique selectivity of the HKUST-1 nanocrystals. A separation efficiency as high as almost 140,000 plates per meter was achieved for the model analyte styrene. The material was stable and exhibited a highly reproductivity. The relative standard deviations of column-to-column, intra-day, and inter-day reproducibility of the SiO2@dSiO2-HKUST-1 packed columns for the retention time of styrene were 4.7%, 0.3%, and 0.4%, respectively.

    更新日期:2017-09-13
  • Ultrasensitive chemiluminescence assay for the lung cancer biomarker cytokeratin 21-1 via a dual amplification scheme based on the use of encoded gold nanoparticles and a toehold-mediated strand displacement reaction
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-25
    Xu Hun, Bingru Liu, Yan Meng

    A catalytic circuit is described in which the addition of a single input DNA strand leads to the release of more than one output strand. The system consists of (a) a three-stranded substrate complex, (b) fuel DNA, and (c) trigger DNA. The whole network is activated by the trigger DNA in the catalytic circuit, which regenerates the trigger to catalyze another new circuit and releases two kinds of bio-barcoded gold nanoparticles (AuNPs) after toehold-mediated strand displacement. The AuNPs are then dissolved to form Au (III) ions which catalyze the luminol-H2O2 chemiluminescence. Cytokeratin 21-1 (CYFRA21-1), associated with so-called non-small cell lung cancer, was used as the model target. By taking advantage of the above dual amplification scheme, this gene assay works in the 20 f. to 8.0 nM CYFRA21-1 concentration range with a 6 f. detection limit. The method exhibits excellent selectivity even over single-mismatched DNA.

    更新日期:2017-09-13
  • Cascade toehold-mediated strand displacement along with non-enzymatic target recycling amplification for the electrochemical determination of the HIV-1 related gene
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-05
    Dan Yin, Yiyi Tao, Lan Tang, Wei Li, Zhang Zhang, Junlong Li, Guoming Xie

    The authors describe a dual-signal electrochemical biosensor for highly sensitive determination of the HIV-1 related gene. This method is based on the application of cascaded toehold-mediated strand displacement reactions (TMSDRs) in combination with non-enzymatic target recycling amplification (TRA). A DNA machine with two TMSDRs was designed, and this resulted in reusable target and an output of two oligonucleotides, referred to as strand A (AS) labeled with the redox tag methylene blue (MB) and as untagged strand B (BS). A ferrocene (Fc)-modified signal probe (Fc-P1) is immobilized on the gold electrode surface by hybridizing with a thiolated probe (P2). The labeled AS causes the dissociation of Fc molecules and the gathering of MB molecules via strand displacement reaction. The target gene triggers TMSDRs and TRA. This leads to an increase in the distance changes between the redox tags and the gold electrode. The assay works in the 1 pM to 10 nM concentration range. On account of target recycling and dual recognition, the limit of detection is as low as 0.88 pM (at an S/N ratio of 3). The assay also has a remarkable selectivity which is ascribed to the use of both cascaded TMSDRs and dual recognition. In our perception, this assay represents a robust means of wide scope in that it may be applied to the detection of various kinds of nucleic acid even in complex samples.

    更新日期:2017-09-13
  • The fate of iron nanoparticles used for treatment of iron deficiency in blood using mass-spectrometry based strategies
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-03
    Jenifer García-Fernández, Jörg Bettmer, Norbert Jakubowski, Ulrich Panne, Elena Añón, María Montes-Bayón, Alfredo Sanz-Medel

    The release of iron from iron nanoparticles (NPs) used as parenteral formulations appears to be influenced by the size and surface properties of the colloidal iron complex and the matrix. A clinically applied product Venofer® has been used as a model formulation to establish adequate analytical strategies to evaluate the fate of iron nanoparticles (NPs) in blood. First, the preparation was characterized by high resolution transmission electron microscopy (HR-TEM), dynamic light scattering (DLS) and UV-vis absorption spectroscopy. This revealed the presence of monodisperse iron NPs with a hydrodynamic diameter of ∼15 nm and an iron core of ∼4 nm. Venofer® was then incubated with serum and whole blood in a quantitative study on the iron bioavailability from these NPs. Iron was speciated and quantified by using inductively coupled plasma mass spectrometry (ICP-MS). Iron solubilization levels of up to 42% were found in both fluids using isotope dilution of iron for quantification within the first hour of incubation even in the absence of the reticulo-endothelial system. The monitoring of the iron-containing proteins present in serum was conducted by high-performance liquid chromatography with ICP-MS detection. It indicated that the dissolved iron ions are bound to transferrin. Quantitative speciation studies using isotope pattern deconvolution experiments concluded that the released iron saturated almost completely (up to 90%) the metal binding sites of transferrin. The remaining iron appeared also associated to albumin and, to a lesser extent, forming smaller sized particles. Thus, the methods presented here provide new insights into the fate of Venofer® nanoparticles and may be applied to other formulations.

    更新日期:2017-09-13
  • A covalent organic framework-based magnetic sorbent for solid phase extraction of polycyclic aromatic hydrocarbons, and its hyphenation to HPLC for quantitation
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-14
    Rong Wang, Zilin Chen

    A novel covalent organic framework based magnetic adsorbent was developed for magnetic solid phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs). Covalent organic framework-LZU1 (= Lan Zhou University-1) was covalently immobilized onto polyethyleneimine-functionalized magnetic nanoparticles (COF-LZU1@PEI@Fe3O4), and the resulting material was characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The effects of the pH value of sample solution, percentage of acetonitrile, extraction time and sampling volume on MSPE of six PAHs were investigated. The COF-LZU1@PEI@Fe3O4 displays high extraction efficiency for the PAHs such as pyrene, benzo[a]pyrene, fluoranthene, benz[a]anthracene, benzo[a]fluorathene and dibenz[a,h]anthracene. Following desorption with acetonitrile, the PAHs were quantified by HPLC. The MSPE-HPLC method shows low limit of detection (0.2–20 pg mL−1), wide linear range and good reproducibility (relative standard deviations <4.4% for intra-day and inter-day precision). The method was successfully applied to determine PAHs in environmental samples. Good recoveries were obtained, ranging from 90.9 to 107.8% for water samples and 85.1 to 105.0% for soil samples.

    更新日期:2017-09-13
  • Colorimetric determination of mercury(II) based on the inhibition of the aggregation of gold nanorods coated with 6-mercaptopurine
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-26
    Ning Bi, Meihua Hu, Jun Xu, Lei Jia

    The authors describe an optical assay for determination of mercury(II) ion by making use of gold nanorods (AuNRs) which are found to aggregate after addition of 6-mercaptopurine (6-MP) by forming a covalent Au-S bond. Aggregation is accompanied by a color change to blue. However, the 6-MP induced aggregation is inhibited in the presence of Hg(II) results because of the formation of a more stable Hg-S bond. The different degrees of aggregation of the AuNRs is indicated by variations in the absorption spectra and accompanied by a color change from blue to brown. Under the optimal conditions, the ratio of absorbances at 780 and 665 nm varies in the 1–100 nM Hg(II) concentration range. The effect can also be detected with bare eyes. The limit of detection is 0.48 nM. The method is rapid, sensitive, and does not require sophisticated instrumentation. It was successfully applied to the determination of Hg(II) in spiked water samples.

    更新日期:2017-09-13
  • PrFeO 3 -MoS 2 nanosheets for use in enhanced electro-oxidative sensing of nitrite
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-17
    Haiping Huang, Lianlian Lv, Fang Xu, Jinsheng Liao, Suijun Liu, He-rui Wen

    The authors describe the synthesis, characterization and electrochemical sensing performance of a PrFeO3-MoS2 nanocomposite. Graphene-like MoS2 sheets and a perovskite-type PrFeO3 were synthesized via a hydrothermal and a sol-gel method, respectively. Finally, PrFeO3-MoS2 nansheets were synthesized by using sodium molybdate as a source for molybdenum and thiourea as the source for sulfur. The nansheets were characterized by transmission electron microscopy and X-ray diffraction. The electrochemical behavior of the nanosheets deposited on a glassy carbon electrode was studied via electrochemical impedance spectroscopy and cyclic voltammetry. The modified electrodes display strong response to nitrite. At a scan rate of 100 mV·s−1, the current at the oxidation peak at 0.85 V (vs. SCE) increases linearly in the 0.005 to 3 mM nitrite concentration range. The detection limit is 1.67 μmol·L−1 (S/N = 3). The sensor is selective, stable and reproducible. It was successfully applied to the determination of nitrite in (spiked) real samples, and appropriate recoveries were obtained.

    更新日期:2017-09-13
  • In-situ growth of Co 3 O 4 nanoparticles on mesoporous carbon nanofibers: a new nanocomposite for nonenzymatic amperometric sensing of H 2 O 2
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-03
    Yue Ni, Yuan Liao, Mingbo Zheng, Shijun Shao

    The paper describes a nonenzymatic amperometric H2O2 sensor that uses a nanocomposite consisting of Co3O4 nanoparticles (NPs) and mesoporous carbon nanofibers (Co3O4-MCNFs). The Co3O4 NPs were grown in situ on the MCNFs by a solvothermal procedure. The synergetic combination of the electrocatalytic activity of the Co3O4 NPs and the electrical conductivity of MCNFs as an immobilization matrix enhance the sensing ability of the hybrid nanostructure. The oxidation current, best measured at 0.2 V (vs. SCE) is linear in the 1 to 2580 μM H2O2 concentration range, with a 0.5 μM lower detection limit (at an S/N ratio of 3). The sensor is highly selective even in the presence of common electroactive interferents. It was applied to the determination of H2O2 in spiked milk samples.

    更新日期:2017-09-13
  • Gold nanoparticles deposited on mesoporous carbon as a solid-phase sorbent with enhanced extraction capacity and selectivity for anilines
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-22
    Cong-Ying Wen, Jingjing Chen, Mengmeng Li, Yutong Xue, Sobia Aslam, Fazle Subhan, Rusong Zhao, Jianfeng Yu, Jingbin Zeng, Xi Chen

    Gold nanoparticles (AuNPs) were in-situ deposited onto the ordered mesoporous carbon (OMC) to function as a novel SPME coating. The specific area, pore volumes and average pore diameter for OMC and AuNP/OMC were calculated to be 411 and 281 m2 g−1, 0.93 and 0.69 cm3 g−1, 7.1 and 6.8 nm, respectively. The results indicate that the introduction of AuNPs greatly enhances the extraction of anilines, probably due to the strong interaction between gold and amino groups. The composite material was coated onto a fiber which then gave enrichment factors in the range from 1143 to 3420 for anilines, 45 to 845 for alcohols and 86 to 545 for phenols, indicating its extraction selectivity towards aniline. Following desorption, four anilines were quantified by gas chromatography with flame ionization detection. The method has low limits of detection (0.072-0.18 μg L−1) and a good precision (1.9-3.8%). It was successfully applied to the analysis of anilines in river and drinking samples. Recoveries range from 83.9% to 107.7% and 94.0 to 113.1%, respectively.

    更新日期:2017-09-13
  • Extraction of gold, palladium and silver ions using organically modified silica-coated magnetic nanoparticles and silica gel as a sorbent
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-14
    Hossein Vojoudi, Alireza Badiei, Alireza Banaei, Shahriyar Bahar, Soheyla Karimi, Ghodsi Mohammadi Ziarani, Mohammad Reza Ganjali

    Two new adsorbents were synthesized by covalently grafting 2,3-Bis(2-formylphenoxy)-propan-1-ol (BH) onto the surface of silica-coated magnetic nanoparticles and silica gel by a conventional method and a vice-versa method. The morphology and properties of the adsorbents were characterized by FT-IR, XRD, SEM, TEM, VSM, TGA, UV-Vis, Optical microscope and DLS. The materials are shown to be effective adsorbents for the selective extraction of the ions of Au(III), Pd(II) and Ag(I) from aqueous mixed metal ions solution also containing Cu(II), Co(II), Ni(II), Zn(II) and Pb(II). Syringe and batch techniques are compared. The ions can be desorbed with 0.5 M HCl and quantified by FAAS. The maximum adsorption capacity of the MN-Si-NH2-BH and Si-NH2-BH were determined to be 257, 197 mg·g−1 for Au(III), 311, 191 mg·g−1 for Ag(I) and 301, 222 mg·g−1 for Pd(II), respectively. The detection limits (for n = 15 and at an S/N ratio of 2 blank standard deviations) are 0.12, 0.28, and 0.17 μg·L−1 for Au(III), Pd(II) and Ag(I), respectively.

    更新日期:2017-09-13
  • Boronate-affinity based magnetic molecularly imprinted nanoparticles for the efficient extraction of the model glycoprotein horseradish peroxidase
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-05
    Xiao-Yu Sun, Run-Tian Ma, Juan Chen, Yan-Ping Shi

    Magnetic molecularly imprinted nanoparticles (MMIPs) with improved dispersity and an increased number of adsorption sites are described. Uniform silica layers were first deposited on the surface of Fe3O4 nanoparticles (Fe3O4 NPs) in order to improve the dispersity of magnetic nanoparticles. Then, 4-formylphenylboronic acid (FPBA) as functional monomer was immobilized on the magnetic carriers to improve the efficiency of template eluting and rebinding. A thin layer of polyaniline imprinted with horseradish peroxidase (HRP) as a model glycoprotein was then placed on the magnetic nanoparticles to enhance the dispersity of the resultant MMIPs. These exhibit high adsorption capacity (62 mg g−1), a satisfactory imprinting factor ( 3.78) and short adsorption equilibrium time (40 min) toward HRP, and the limit of detection is 18.7 μg L−1. This kind of MMIPs, therefore, is deemed being a useful tool for extracting low-abundance glycoproteins from even complex samples.

    更新日期:2017-09-13
  • Visible light photoelectrochemical sulfide sensor based the use of TiO 2 nanotube arrays loaded with Cu 2 O
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-04
    Yongzhao Su, Siyuan Yang, Weipeng Liu, Long Qiao, Jie Yan, Yingju Liu, Shengsen Zhang, Yueping Fang

    This work describes a photoelectrochemical for sensing sulfide method that is based on TiO2 nanotubes loaded with Cu2O particles (Cu2O/TiNTs). The narrow band gap of Cu2O and the heterostructure at the interface between Cu2O and TiO2 in the Cu2O/TiNTs significantly enhance visible light absorption and charge separation, and these results in an improved photocurrent of the Cu2O/TiNT electrode under irradiation with visible light (> 400 nm). In the presence of sulfide, Cu7S4 is formed on the surface of the Cu2O/TiNT, this leading to a decrease in the photocurrent on the electrode. At a potential of 0.0 V, the photocurrent of the Cu2O/TiNTs before and after immersing it into 300 μM sulfide solution is 1086 and 310 μA cm−2, respectively. The findings were used to design a photoelectrochemical sulfide sensor. Under optimum conditions and at a pH value of 7.0, the change in photocurrent varies linearly in the 1 to 300 μM sulfide concentration range with a 0.6 μM detection limit. The sensor was applied to the determination of sulfide in spiked real water samples.

    更新日期:2017-09-13
  • Bimetallic nanoclusters with strong red fluorescence for sensitive detection of hypochlorite in tap water
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-08
    Pu Zhang, Yi Wang, Ling Chen, Yibing Yin

    Gold-silver nanoclusters (Au-AgNCs) were synthesized by simultaneous chemical reduction of Au(III) and Ag(I) ions in one pot, using bovine serum albumin as both a template and a reductant. The Au-AgNCs have an average size of 2.4 nm and display strong red fluorescence (with an emission peak at 610 nm on excitation at 360 nm). The fluorescence quantum yield can reach 18.6%. Fluorescence is strongly quenched by hypochlorite, while other common anions have minor (or no) effects on fluorescence. Based on these findings, a fluorometric method was developed for the determination of hypochlorite. The method has a linear response in the 0.7 to 15 μM concentration range, with a limit of detection as low as 80 nM. It was successfully applied to the determination of hypochlorite in (spiked) tap water.

    更新日期:2017-09-13
  • Turn-on fluorometric NADPH assay using orange emitting graphene oxide quantum dots
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-12
    Weidan Na, Tianyu Hu, Xingguang Su

    The authors describe a method for synthesizing graphene oxide quantum dots (GOQDs) possessing orange fluorescence with emission wavelength that can be tuned over the range from 537 to 593 nm by variation of the excitation wavelength. The GOQD display peroxidase-mimicking catalytic activity. Specifically, they catalyze the oxidation of dopamine to produce 4-(2-aminoethyl)benzene-1,2-quinone (AQ) which is colored and can quench the fluorescence of GOQDs. However, quenching is reversed by addition of NADP+, but not by its reduced form (NADPH). Based on these findings, an assay was worked out to monitor enzymatic reactions involving NADP+. The method allows NADPH to be detected in the 2–175 μM concentration range, with a 0.6 μM detection limit.

    更新日期:2017-09-12
  • Hierarchical C-N doped NiO with dual-head echinop flowers for ultrasensitive monitoring of epinephrine in human blood serum
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-12
    Mohammed Y. Emran, Hesham Khalifa, Hassanien Gomaa, Mohamed A. Shenashen, Naeem Akhtar, Moataz Mekawy, Ahmed Faheem, Sherif A. El-Safty

    The authors describe nanoelectrodes based on the use of hierarchical carbon-nitrogen nanospheres and dual-head nickel oxide echinop flowers (CN@HDN) placed on indium tin oxide (ITO) electrodes. The modified electrodes enable sensitive detection of catecholamine neurotransmitters, specifically of epinephrine (EPI) in human serum samples. The modified electrodes possess many active sites along the {111} crystal plane and large contact surfaces. This enables a rapid EPI diffusion within a highly active transport surface. The geometrical and morphological structures of the NiO decorated with CN-nanospheres render superior electrocatalytic behavior at a relatively low working voltage of 0.12 V (vs. Ag/AgCl) which makes the sensor relatively specific. The use of CN also increases the electron transfer rate and facilitates mass transfer between electrolyte (EPI sample) and catalytically active sites. The electrode is sensitive, selective and works at near-physiological pH values. It has a detection limit as low as 4 nM of EPI.

    更新日期:2017-09-12
  • Aptamer-based fluorometric determination of norovirus using a paper-based microfluidic device
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-11
    Xuan Weng, Suresh Neethirajan

    The authors describe a rapid and highly sensitive point-of-care device for rapid determination of noroviruses, a leading cause of acute gastroenteritis. The assay is based on the use of a norovirus-specific aptamer labeled with 6-carboxyfluorescein, and of multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO). The fluorescence of the 6-FAM labeled aptamer is quenched by MWCNT or GO. In the presence of norovirus, fluorescence is recovered due to the release of the labeled aptamer from MWCNT or GO. An easy-to-make paper-based microfluidic platform was developed using a nitrocellulose membrane. The quantitation of norovirus was successfully performed. The linear range extends from 13 ng·mL−1 to 13 μg·mL−1 of norovirus. The detection limits are 4.4 ng·mL−1 and 3.3 ng·mL−1, respectively, when using MWCNT or GO. The device is simple and cost-effective, and holds the potential of rapid in-situ visual determination of noroviruses with remarkable sensitivity and specificity. Hence, it provides a new method for early identification of norovirus and a tool for early intervention when preventing the spread of an outbreak.

    更新日期:2017-09-11
  • Amperometric hydrazine sensor using a glassy carbon electrode modified with gold nanoparticle-decorated multiwalled carbon nanotubes
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-11
    Hassan Hamidi, Somayyeh Bozorgzadeh, Behzad Haghighi

    Gold nanoparticles (AuNP) were deposited on the surface of multiwalled carbon nanotubes (MWCNT) by in-situ thermal decomposition of gold acetate under solvent and reducing agent free conditions to obtain a nanohybrid of AuNP-MWCNT. A glassy carbon electrode (GCE) was then modified with the nanohybrid and used for amperometric determination of hydrazine. The modified GCE showed an improved electrocatalytic effect towards hydrazine oxidation at a working potential of about 0.30 V (vs Ag|AgCl,KClsat). The calibration plot for hydrazine is linear in two concentration ranges, viz. from 0.1–100 μM and 0.2–1 mM. The respective sensitivities are 4.98 and 4.00 μA μM−1cm−2, and the limit of detection (at S/N = 3) is about 30 nM.

    更新日期:2017-09-11
  • Determination of glucose by using fluorescent silicon nanoparticles and an inner filter caused by peroxidase-induced oxidation of o-phenylenediamine by hydrogen peroxide
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-08
    Longhua Ding, Zhaojin Gong, Mei Yan, Jinghua Yu, Xianrang Song

    The authors describe a new kind of enzymatic glucose assay. The strategy involves three processes: (a) Generation of H2O2 via glucose oxidase catalyzed oxidation of glucose; (b) production of 2,3-diaminophenazine (DAP) from H2O2 and o-phenylenediamine (OPD) via peroxidase-catalyzed oxidation; and (c) a reduction of the blue fluorescence of SiNPs with emission maxima at 445 nm via an inner filter effect that is caused by DAP which is yellow and has an absorption peak at 450 nm. Fluorescence drops with increasing glucose concentrations in the 0.01 to 7 mM concentration range, and the detection limit is 3.5 μM. The assay was successfully applied to the analysis of glucose in human serum.

    更新日期:2017-09-08
  • Synthesis of an ion-imprinted sorbent by surface imprinting of magnetized carbon nanotubes for determination of trace amounts of cadmium ions
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-08
    Behrooz Zargar, Ali Khazaeifar

    The authors report on the preparation of sol-gel coated magnetized carbon nanotubes whose surface were imprinted with Cd2+ ions and the application of these materials on selective preconcentration of Cd2+ ions in different water samples. Fe3O4 particles and tetraethyl orthosilicate were used as a magnetic ingredient and as a surface modifier for the carbon nanotubes, respectively. The Cd2+-imprinted polymer was prepared by grafting copolymerization of Cd2+ ions as template, methacryloylsulfamethizole and 2-vinylpyridine as polymerizable ligands, methacrylic acid as functional monomer, and ethyleneglycoldimethacrylate as crosslinker. The resulting magnetic nanoparticles were characterized by Fourier transform infrared spectrometry, the Brunauer-Emmett-Teller method, and by scanning electron microscopy. Isothermal absorption, absorption kinetics and selectivity were studied in detail. The experimental conditions were optimized. Figures of merit include (a) a maximum adsorption capacity of 81 mg·g−1; (b) relative selectivity coefficients of 2.41, 2.36, 1.41, 1.66, and 1.70 for Cd2+/Ni2+, Cd2+/Co2+, Cd2+/Zn2+, Cd2+/Cu2+, and Cd2+/Pb2+, respectively; (c) a detection limit of 0.29 ng·mL−1, (d) an enrichment factor of 55.5; (e) an intra-day precisions of 1.13%; and (f) an inter-day precision of 1.39%. The method was successfully applied to the determination of cadmium in spiked samples including feed water of an ammonia production unit, tap water, industrial waste water from a petrochemical plant, river water from the Garrahi River, bay water from Khor Musa, and marsh water from the Shadegan wetland.

    更新日期:2017-09-08
  • Core/shell microcapsules consisting of Fe 3 O 4 microparticles coated with nitrogen-doped mesoporous carbon for voltammetric sensing of hydrogen peroxide
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-07
    Zuojia Qin, Yu Zhao, Li Lin, Ping Zou, Li Zhang, Hui Chen, Ying Wang, Guangtu Wang, Yunsong Zhang

    The authors describe the preparation of core/shell composites consisting of Fe3O4 microparticles coated with nitrogen-doped mesoporous carbon. Synthesis was accomplished by simultaneous reduction of template α-Fe2O3 and pyrolysis of a nitrogen-containing poly(ionic liquids). The mesoporous composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry and adsorption/desorption isotherms. The characterizations prove successful formation of an Fe3O4 core and an outer shell (coating) consisting of nitrogen-doped mesoporous carbon. The material was placed on a glassy carbon electrode and synergistic catalytic effect of of N-doping, the mesoporous, core/shell structure and two types of active sites properties between Fe3O4 core and nitrogen-doped mesoporous carbon shell is shown to result in superior electrochemical activity towards the reduction of hydrogen peroxide. Figures of merit include (a) a sensitivity of 77.1 μA mM−1 cm−2; (b) a linear response over the 50 μM to 33 mM H2O2 concentration range, (c) a 5.9 μM detection limit of (at an S/N ratio of 3), and (d) a low working voltage of −0.4 V (vs. saturated calomel electrode) which makes the method more selective.

    更新日期:2017-09-07
  • A hyperbranched polyamidoamine dendrimer grafted onto magnetized graphene oxide as a sorbent for the extraction of synthetic dyes from foodstuff
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-07
    Zahra Lotfi, Hassan Zavvar Mousavi, S. Maryam Sajjadi

    Graphene oxide nanosheets were modified with magnetite nanoparticles, and a hyperbranched polyamidoamine dendrimer was then covalently attached to their surface. The resulting material is shown to be an efficient sorbent for preconcentration of the synthetic dyes tartrazine, quinoline yellow, sunset yellow and carmoisine via ultrasound-assisted magnetic solid phase extraction. The electrostatic interaction and hydrogen bonding were considered to be the main mechanism for the dyes adsorption. The sorbent was characterized by transmission electron microscopy, field emission scanning electron microscopy, FT-IR, X-ray diffraction and vibrating sample magnetometry. The effects of pH value, sorbent dosage, eluent volume, and sonication time were optimized by central composite design and desirability function. The dyes were quantified by HPLC with detection at 450 nm. Under optimized conditions, the method has a linear response in the 2–3000, 5–2000, 1–5000 and 2–2500 ng.mL−1 concentration range for tartrazine, quinoline yellow, sunset yellow and carmoisine, respectively. The limits of detection are as low as 0.6, 1.5, 0.3 and 0.6 for tartrazine, quinoline yellow, sunset yellow and carmoisine, respectively.

    更新日期:2017-09-07
  • Spider-web-like chitosan/MIL-68(Al) composite nanofibers for high-efficient solid phase extraction of Pb(II) and Cd(II)
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-06
    Mina Asiabi, Ali Mehdinia, Ali Jabbari

    The authors describe the synthesis of spider-web-like chitosan/MIL-68(Al) composite nanofibers, their application to fast solid phase extraction (SPE) of trace levels of Pb(II) and Cd(II), and their quantitation by ICP-OES. The composite nanofibers were characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption experiments and FT-IR. The pH value of sample solutions, amount of sorbent, eluent concentration and type and volume of the eluting solvent were optimized using factorial experimental design. Under the optimum conditions, the detection limits are 0.16 μg L−1, and linear ranges extend from 0.5–50 μg L−1 for both Pb(II) and Cd(II). The intra-day relative standard deviations (RSDs) of <3.8% and inter-day RSDs of <4.3% are quite acceptable. The accuracy of the method was tested by the analysis of the certified reference material IAEA-407 and by recovery measurements on spiked real samples (phylum, gastropoda, Trochus erythraeus mollusks) which demonstrated the good performance of the method for SPE and determination of Pb(II) and Cd(II) ions.

    更新日期:2017-09-06
  • Determination of nickel(II) via quenching of the fluorescence of boron nitride quantum dots
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-06
    Qiuhong Yao, Yufeng Feng, Mingcong Rong, Shaogui He, Xi Chen

    Fluorescent boron nitride quantum dots (BNQDs) were synthesized from boric acid and ammonium hydroxide by a hydrothermal method. Under 305 nm excitation, the BNQDs emit blue fluorescence with a peak at 400 nm and a quantum yield of 32%. The BNQDs are highly photostable and resistant to ionic strength. A rapid fluorometric method for the determination of Ni2+ was developed using the heavy-metal free BNQDs via photo-induced electron transfer. Under optimal conditions, fluorescence varies linearly with the logarithm of the Ni2+ concentration in the range from 0.1 to 100 μmol·L−1. The detection limit is 0.1 μmol·L−1.

    更新日期:2017-09-06
  • A glassy carbon immunoelectrode modified with vanadium oxide nanobelts for ultrasensitive voltammetric determination of the core antigen of hepatitis C virus
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-05
    Akram Valipour, Mahmoud Roushani

    The authors describe a voltammetric immunoassay for the hepatitis C virus core antigen. It is based on the use of vanadium oxide nanobelts that were used to modify a glassy carbon electrode (GCE). The nanobelts have a large specific surface area that can be heavily loaded with antibody against the hepatitis C virus core antigen. Following blocking with BSA and by using riboflavin as an electrochemical probe, the immuno GCE (best operated at a working voltage of −0.45 V vs. Ag/AgCl) has a linear response that covers the 10 fg·mL−1 to 100 ng·mL−1 core antigen concentration range and a limit of detection as low as 1.3 fg mL−1. Compared to the other redox probes, riboflavin is superior because it is oxidized in the negative potential range, where the number of interfering species for riboflavin is small. The method was successfully applied to the determination of hepatitis C virus core antigen in spiked serum. In our perception, the use of a V2O5 nanobelt film as a support for bioreceptors has a wide scope in that in that it may be extended to immunoassays for various other diagnostically significant analytes.

    更新日期:2017-09-05
  • Mediator-free simultaneous determination of acetaminophen and caffeine using a glassy carbon electrode modified with a nanotubular clay
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-05
    J. Kalaiyarasi, S. Meenakshi, Subash C. B. Gopinath, K. Pandian

    The authors describe a voltammetric method for the simultaneous determination of acetaminophen (ACOP) and caffeine (CAF) using a glassy carbon electrode modified with a Nafion® protected halloysite nanotubular clay (GCE). Enhanced electrocatalytic oxidation behavior was observed at pH 4.5 in acetate buffer medium, with oxidation peak potentials of + 0.21 V for ACOP and + 1.0 V for CAF. The peak potential window (~ 800 mV) is quite large and hence differential pulse voltammetry (DPV) can be applied for simultaneous determination of both analytes. The calibration plots of ACOP and CAF are linear in the concentration ranges from 0.6 μM to 14 μM and 0.6 μM to 20 μM, and the detection limits are 1.1 × 10−8 M and 1.73 × 10−7 M, for ACOP and CAF, respectively. The method was applied to the determination of both analytes in drug formulations and human urine samples.

    更新日期:2017-09-05
  • A glassy carbon electrode modified with graphene nanoplatelets, gold nanoparticles and chitosan, and coated with a molecularly imprinted polymer for highly sensitive determination of prostate specific antigen
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    Ya Ma, Xiao-Lei Shen, Qiang Zeng, Li-Shi Wang

    The authors describe an amperometric assay for the detection of prostate specific antigen (PSA) that combines the advantages of using a molecularly imprinted polymer (MIP) and of a nanocomposite composed of  graphene nanoplatelets (graphene sheets; GS), gold nanoparticles (AuNPs) and chitosan (Chit). The GS-AuNP composite was synthesized by a single-step reduction of GS and HAuCl4 solution. The MIP was synthesized by electropolymerization of dopamine and characterized by scanning electron microscopy and differential pulse voltammetry (DPV). Sensitivity is strongly improved by the magnified current obtained by using the GS-AuNP hybrid. Chit was further employed as a film-forming material to prevent the leakage of nanomaterials. Under optimized conditions, the method displays good analytical performance for the detection of PSA by DPV and by using hexacyanoferrate as the electrochemical probe. The peak current (typically measured at 0.16 V vs. SCE) increases linearly in the 1 pg mL−1 to 100 ng mL−1 PSA concentration range, and the detection limit is 0.15 pg mL−1 at a signal to noise ratio of 3. The method was successfully applied to the determination of PSA in serum. The assay is highly selective, sensitive, reproducible and stable. In our perception, it represents an attractive alternative to the commercially available ELISA kits for PSA.

    更新日期:2017-09-04
  • Aptamer-based determination of ATP by using a functionalized impedimetric nanosensor and mediation by a triangular junction transducer
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    Subash C. B. Gopinath, Veeradasan Perumal, S.R. Balakrishnan, M. K. Md Arshad, Thangavel Lakshmipriya, R. Haarindraprasad, Uda Hashim

    The authors describe an impedimetric nanosensor for aptamer-mediated detection of ATP. A triangular junction of polysilicon substrate is used as a transducer. The aptamer was immobilized on the substrate via biotin-streptavidin interaction. ATP can be detected by this method in the 10 to 100 nM concentration range at room temperature and estimated the signal to noise ratio above the range of 3σ. It was applied to the detection of ATP in 1:1000 diluted human urine. The desired transducer is highly reproducible and specific. It is selective over closely related molecules such as guanosine triphosphate, cytidine triphosphate and uridine triphosphate. The method is perceived to represent a valuable tool for the diagnosis for infections and inflammations. The novelties shown in this study compared to other sensors are, consumption of low sample volume (~ 1 μl), non-invasive and suitable with AC and DC currents.

    更新日期:2017-09-04
  • Colorimetric determination of the microcystin leucine-arginine based on the use of a hairpin aptamer, graphene oxide, and Methylene Blue acting as an optical probe
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    Khalil Abnous, Noor Mohammad Danesh, Mohammad Ramezani, Seyed Mohammad Taghdisi

    The authors describe an aptamer-based colorimetric assay for the specific detection of the toxic microcystin leucine-arginine (MC-LR). The method is based on the use of graphene oxide (GO) in a hydrogel matrix, Methylene Blue (MB) acting as an optical probe, streptavidin-modified magnetic particles, and an aptamer (Apt) as a the recognition probe. A complementary strand of the aptamer and adenosine act as promoters in the formation of the GO hydrogel, and the hairpin structure of the aptamer warrants selectivity. In the absence of MC-LR, the gelation of GO sheets is promoted by complementary strand and adenosine, and MB is trapped between GO sheets. Hence, no blue color can be observed in the sample solution. In the presence of MC-LR, GO does not cause the formation of a strong hydrogel structure and a distinct blue color can be observed and measured (at 660 nm) because MB is present in solution. The assay has high selectivity for MC-LR, with a limit of detection (LOD) as low as 219 pM. It was successfully applied to the determination of MC-LR in spiked tap water and serum samples where it gave LODs of 221 and 412 pM, respectively.

    更新日期:2017-09-04
  • Voltammetric determination of Basic Red 13 during its sonoelectrocatalytic degradation
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    Saeid Jafari, Mohammad Dehghani, Navid Nasirizadeh, Hamid Reza Akrami

    The article describes a sensor for the voltammetric determination of the azo dye Basic Red 13 (BR13) during its degradation by using sonoelectrochemistry in the presence of TiO2 nanoparticles. A glassy carbon electrode was modified with silver nanoparticles and graphene oxide sheets. The performance of the method was compared to that of the spectrophotometric assay at 523 nm. The voltammetric sensor, best operated at +0.752 V vs. SCE, has a linear range that covers concentrations from 0.5 to 100.0 μM BR13, which is much wider than that of spectrophotometry. The detection limit is 2.0 μM. The method was successfully applied to BR13 detection in wastewater samples collected a textile plant.

    更新日期:2017-09-04
  • A glassy carbon electrode modified with SnO 2 nanofibers, polyaniline and hemoglobin for improved amperometric sensing of hydrogen peroxide
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    A. K. M. Kafi, Qamar Wali, Rajan Jose, Tapan Kumar Biswas, Mashitah M. Yusoff

    The authors describe a glassy carbon electrode (GCE) modified with a multiporous nanofibers prepared from SnO2, polyaniline and hemoglobin, and its application to the amperometric determination of hydrogen peroxide (H2O2). The SnO2 nanofibers were prepared first and then polymerized with polyaniline. Then, the redox protein hemoglobin was co-immobilized with the nanofibers on the surface of the GCE. Chitosan was finally used to improve the stability of the modified GCE. Direct electrochemistry of Hemoglobin at the modified electrode revealed a pair of well-defined redox peaks, with anodic and cathodic peaks at −0.15 and −0.3 V, respectively. The modified GCE exhibits high catalytic response to hydrogen peroxide. Best operated at −0.4 V (vs Ag/AgCl), it displays a linear amperometric response that covers the 2 to 160 μM H2O2 concentration range, with a lower detection limit of 0.5 μM. The biosensor has good storage stability, reproducibility and repeatability.

    更新日期:2017-09-04
  • Adsorption and specific recognition of DNA by using imprinted polymer layers grafted onto ionic liquid functionalized magnetic microspheres
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-04
    Qingzhou Dai, Yuzhi Wang, Wei Xu, Yanjin Liu, Yigang Zhou

    A molecularly imprinted polymer based on silica modified Fe3O4 microsphere and ionic liquid was prepared for the adsorption and specific recognition of DNA. Water-compatible imidazolium ionic liquids were introduced on the surface of silica-coated Fe3O4 microsphere, then used as the adsorbents, againsting DNA from salmon testes (stDNA) by combining immobilized template and surface imprinting techniques. The imprinted polymer layers were grafted onto ionic liquid functionalized microspheres through sol-gel approach using N-3-(3-triethoxysilylpropyl)-3-aminopropyl imidazolium chloride and N-3-(3-triethoxysilylpropyl)-3-mexyl imidazolium chloride as the functional monomers, and tetraethoxysilane as the cross-linker. Because both imidazolium ionic liquid and DNA are soluble in water, it is mandatory to implement an imprinted process in an aqueous medium to well maintain the integrity of the conformation. Fourier transform infrared spectrometry, thermogravimetric analysis, transmission electron microscopy, X-ray diffraction and vibrating sample magnetometry were employed to characterize the materials. The nanomaterials with multiple imprinting sites and biocompatible cavities exhibit high specific adsorption capacity of DNA (162 mg·g−1) and excellent rebinding selectivity (imprinting factor up to 6.6) against non-imprinted molecules at pH value of 5.10. Moreover, it is feasible to strip DNA from the highly cross-linked polymer network by using aqueous NaCl (1.0 M). The nanomaterials are cap able of capturing DNA from calf whole blood, which might provide a viable tool for DNA preconcentration, separation and recognition.

    更新日期:2017-09-04
  • Ultrasensitive aptasensing of lysozyme by exploiting the synergistic effect of gold nanoparticle-modified reduced graphene oxide and MWCNTs in a chitosan matrix
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-19
    Esmaeil Heydari-Bafrooei, Samira Askari

    The authors describe a lysozyme aptasensor based on the use of gold nanoparticles (AuNP) assembled on the carbon nanotubes, graphene oxide and chitosan. An electrochemical impedance spectroscopic study was performed to demonstrate the synergistic effect of the MWCNT-AuNP, Chit-AuNP and GO-AuNP composites and the order of the layers affect the performance of aptasensing. Different parameters were optimized in order to obtain successful and sensitive detection of lysozyme in urine and saliva samples. A plot of charge-transfer resistance versus the logarithm of the lysozyme concentration is linear in the 0.02 to 250 pM concentration range, with a 9 fM detection limit (at an S/N ratio of 3). The aptasensor is highly specific and selective. Clinical analyses were performed and data were found to be in good agreement with those obtained by HPLC.

    更新日期:2017-08-24
  • A turn-on fluorescent lysine nanoprobe based on the use of the Alizarin Red aluminum(III) complex conjugated to graphene oxide, and its application to cellular imaging of lysine
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-24
    Rumei Cheng, Yu Peng, Congcong Ge, Yexu Bu, Hongyan Liu, Huiying Huang, Shengju Ou, Yuhua Xue, Liming Dai

    The authors describe a rationally designed nanoprobe for the fluorometric determination of lysine. It is based on a ternary complex consisting of graphene oxide, aluminum ions (acting as a bridging agent), and alizarin red (GO-Al-AR). The fluorescence of the complex (with excitation/emission maxima at 440/512 nm) is weak but significantly enhanced upon the addition of lysine, probably due to a photoinduced electron transfer signalling mechanism. The method has a detection limit of 2 mg L−1 of lysine and a linear range from 25 mg L−1 to 250 mg L−1. It was applied to image lysine in human retinal pigment epithelium cells.

    更新日期:2017-08-24
  • Liquid crystal-based detection of DNA hybridization using surface immobilized single-stranded DNA
    Microchim. Acta (IF 4.58) Pub Date : 2017-05-18
    Jia Shen, FengJie He, LongCong Chen, Lu Ding, HuiLong Liu, Ying Wang, XingLiang Xiong

    The authors have investigated (a) the self-assembly of single-stranded DNA (ssDNA) on glass surfaces, and (b) the interaction of DNA with liquid crystals (LCs) on solid surfaces. The results suggest that ssDNA (compared to dsDNA) on the solid interface causes particularly different orientations in LCs. The LC molecules assume a uniform homeotropic orientation on the surface with a typical surface ssDNA coverage of ~2.4 × 1012 molecules per square cm. Once complementary DNA is hybridized on the surface, the homotropic orientation of the LCs becomes disrupted. This orientation transition can be visually observed by using a crossed polarizer. The findings were exploiting to design an assay for target DNA (= analyte DNA) that has an ~0.1 nM detection limit. The assay is highly selective and can easily differentiate target DNA from single-base mismatch and non-complementary DNA. In our perception, it represents a powerful, label-free and portable DNA detection scheme.

    更新日期:2017-08-24
  • Chemiluminescence immunoassay for cardiac troponin T by using silver nanoparticles functionalized with hemin/G-quadruplex DNAzyme on a glass chip array
    Microchim. Acta (IF 4.58) Pub Date : 2017-05-24
    Chen Zong, Duoduo Zhang, Hua Yang, Shumei Wang, Ming Chu, Ping Li

    The authors describe an array for chemiluminescence (CL) based determination of cardiac troponin T (cTnT), an important cardiovascular disease marker. The tracing tag consists of silver nanoparticles (AgNPs) loaded with guanine-rich DNA sequences and detection antibody in a high numerical ratio. The loaded AgNPs were then reacted with hemin to form a hemin/G-quadruplex DNAzyme. A disposable immunosensor array was fabricated by immobilizing capture antibody on corresponding sensing sites on a glass chip. Once a sandwich immunocomplex is formed on the array, the tracing tag catalyzes the CL reaction of the luminol-p-iodophenol and H2O2 system to produce a CL signal, which is collected by a CCD camera. An intuitive CL image is obtained containing all of the spots on the array. Under optimal conditions, the method shows a wide linear range over 4 orders of magnitude (from 0.003 to 270 ng·L−1), a detection limit down to 84 fg·L−1, and a throughput as high as 44 tests·h−1. The results obtained with serum samples are in acceptable agreement with reference values. The AgNP-based tracing tag as well as the immunoassay method shows a promising potential for point-of-care testing for the early clinical diagnosis of cardiovascular disease.

    更新日期:2017-08-24
  • Lab-on-nanoparticle as a multidimensional device for colorimetric discrimination of proteins
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-06
    Feiyang Wang, Yuexiang Lu, Wenjie Jing, Liuying He, XinXin Gao, Yueying Liu

    We report on a method for sensitive detection and discrimination of multiple proteins. The peroxidase-like activity of gold nanoparticles (AuNPs) is employed to catalyze the oxidation of 3′,3′,5′,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Depending on the protein, this produces colorations with different absorbance. The catalytic activity of the reaction system is affected because different proteins are absorbed onto the surface of the AuNPs. The absorbance values at 370, 450, and 650 nm are different in the presence of different proteins. The array can discriminate 8 proteins at 50 nM concentration levels with 100% accuracy. It also can discriminate proteins being present in different concentrations and mixtures with different molar ratios of proteins. Human urine spikes with 8 proteins (Concanavalin A), Cytochrome C, Horseradish peroxidase, Human serum albumin, Myoglobin, Pepsin, Trypsin, Papain) can be differentiated by applying hierarchical cluster analysis. The system also can discriminate proteins at different concentrations and the mixtures with different molar ratios in bovine serum. This indicates that the array has a great potential in terms of analyzing biological fluids.

    更新日期:2017-08-24
  • A bucky gel consisting of Fe 3 O 4 nanoparticles, graphene oxide and ionic liquid as an efficient sorbent for extraction of heavy metal ions from water prior to their determination by ICP-OES
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-20
    Mohammad Kazem Rofouei, Sarah Jamshidi, Shahram Seidi, Abolfazl Saleh

    Bucky gels are gelatinous composite materials consisting of carbon nanotubes and ionic liquids. The authors describe the synthesis of a bucky gel containing Fe3O4 nanoparticles which is shown to be a viable sorbent for the preconcentration of the ions Cu(II), Zn(II), Cd(II), Cr(III), Pb(II) and Co(II) from environmental water samples. The metal ions were first complexed with 1-(2-pyridylazo)-2-naphthol and then extracted by the sorbent. Following magnetic separation, the ions are desorbed from the sorbent with acetonitrile and then submitted to ICP-OES. Experimental design and response surface methodology were applied to optimize the parameters on that affect the performance of the method. Under the optimized conditions, the detection limits for Cd, Co, Cr, Cu, Pb and Zn are 0.5, 0.3, 0.8, 0.1, 1.0 and 0.1 μg L−1, respectively. The enrichment factors are in the range between 17 and 47, and the relative standard deviations (for n = 6 at a 50 μg L−1 level) are <3.2%. Response is linear in the 1.5 to 100 μg L−1 metal ion concentration range. The method was successfully applied to the determination of trace amounts of the analytes in (spiked) water samples. Relative recoveries (RR%) were achieved within the range of 90.5% to 107.5%, corresponding to relative errors of −9.5% to +7.5%.

    更新日期:2017-08-24
  • Impedimetric immunoassay for aflatoxin B1 using a cysteine modified gold electrode with covalently immobilized carbon nanotubes
    Microchim. Acta (IF 4.58) Pub Date : 2017-05-25
    Maurilia P. Costa, Isaac A. M. Frías, Cesar A. S. Andrade, Maria D. L. Oliveira

    The authors describe a label-free electrochemical biosensor based on CNTs for picogram range detection of the food carcinogen aflatoxin B1 (AFB1). A gold electrode was modified with a cysteine (Cys) self-assembled layer, and carboxyl-functionalized carbon nanotubes were covalently attached to Cys for the subsequent tethering of antibody against AFB1 (anti-AFB1). Topographical images of the biosensor surface were acquired by atomic force microscopy throughout the modification and assay procedure. Upon exposure to samples containing AFB1, its binding to anti-AFB1 will result in a change in electrical conductivity. The use of CNT warrants enhanced electrical properties, and the charge-transfer resistance (Rct) can be related to the concentration of AFB1. Biosensor selectivity was tested by using samples containing ochratoxin A. The electrode displays a limit of detection as low as 0.79 pg·g−1, and response is linear in the 0.1 to 20 pg·g−1 concentration range. The assay was applied to the determination of AFB1 in contaminated corn flour at concentrations so low that they cannot be quantified by established ELISAs. In our perception, this method represents a viable point-of-care probe for detection of AFB1.

    更新日期:2017-08-24
  • Covalent attachment of biotinylated molecular beacons via thiol-ene coupling. A study on conformational changes upon hybridization and streptavidin binding
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-01
    Daniel González-Lucas, María-José Bañuls, Jaime García-Rupérez, Ángel Maquieira

    The authors describe a method for the detection of DNA by using immobilized molecular beacons (MBs) on the surface of silicon, with a view on possible application in biosensing. MB hybridization and protein recognition were interrogated on silicon-on-insulator (SOI) surfaces by using fluorescently tagged probes. In order to better understand the conformational changes that occur to MBs upon hybridization, the process was studied by using dual polarization interferometry (DPI). A model system was developed that matches thickness, mass, and density parameters. The results experimentally demonstrate that hybridization promotes the displacement of a protein away from the surface. This finding may be further exploited in techniques such as photonic sensors, thereby paving the way to the design of more sensitive biosensors based on the use of MBs.

    更新日期:2017-08-24
  • Photoelectrochemical dopamine sensor based on a gold electrode modified with SnSe nanosheets
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-08
    Xu Hun, Shanshan Wang, Shuyu Mei, Hongqing Qin, Hui Zhang, Xiliang Luo

    The authors have prepared SnSe nanosheets by a solvothermal method and used them to modify a gold electrode to obtain a photoelectrochemical (PEC) sensor for dopamine (DA) which yields a signal upon irradiation with visible light. On addition of DA, the photocurrent is significantly higher than in the absence of DA, and it increases with increasing DA concentration. A PEC sensor was developed based on this finding which responds linearly to DA in the 0.01 μM to 10 μM concentration range and with a 3 nM detection limit. The application of this PEC sensor in actual samples was also tested. The mechanism of PEC analysis of DA is provided. The electrons of SnSe NSs were excited under irradiation with visible light and transformed from valance band to conduction band. DA as electron donor provided the electrons to SnSe NSs. An enhanced photocurrent was obtained.

    更新日期:2017-08-24
  • Photoelectrochemical amperometric sensing of cyanide using a glassy carbon electrode modified with graphene oxide and titanium dioxide nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-29
    Rahman Hallaj, Nasibeh Haghighi

    The authors describe a modified glassy carbon electrode (GCE) for the amperometric determination of cyanide ions. First, the surface of TiO2 nanoparticles was modified with aminopropyltriethoxysilane (AS). These were then deposited, along with graphene oxide (GO) nanosheets, on the surface of the GCE. The modification steps were followed by reductive deposition of reduced 4-nitrophenol (rNPh). The GO/TiO2-AS-rNPh electrode was used to design a photoelectrochemical amperometric cyanide assay which works in pH 7 solution, best at 0.35 V (vs. Ag/AgCl). Characteristics of merit include a 0.1 μM detection limit, a 165.5 nA·nM−1·cm−2 sensitivity, and a dynamic linear range extending from 0.1 μM to 60 μM. The selectivity of the assay was tested by recording the response of the modified GCE to potentially interfering anions and was found to be very good. The inherent photocatalytic activity, good stability, wide linear analytical range, short response time, low detection limit and good selectivity make this assay highly advantageous

    更新日期:2017-08-24
  • A non-enzymatic sensor for hydrogen peroxide based on the use of α-Fe 2 O 3 nanoparticles deposited on the surface of NiO nanosheets
    Microchim. Acta (IF 4.58) Pub Date : 2017-05-26
    Divyalakshmi Saravana achari, Chella Santhosh, Revathy Deivasegamani, Ravi Nivetha, Amit Bhatnagar, Soon Kwan Jeong, Andrews Nirmala Grace

    This work reports on the synthesis of nanocomposites from NiO and α-Fe2O3 by a hydrothermal route. The material was characterized in terms of structural and morphological features by X-ray diffraction and scanning electron microscopy. The nanocomposites were synthesized by growing α-Fe2O3 nanoparticles on the surface of flower-like NiO nanosheets, and then characterized by cyclic voltammetry and amperometric techniques. A glassy carbon electrode (GCE) modified with the nanocomposite displayed distinctly improved response to H2O2 compared to a GCE modified with bare NiO. The H2O2 sensor, best operated at a voltage of 0.4 V (vs. Ag/AgCl) has a sensitivity of 146.98 μA·μM−1·cm−2, a 0.05 mM lower detection limit, and a linear working range that extends from 0.5 to 3 mM of H2O2. The sensor is reproducible and long-term stable even in the presence of various interfering molecules such as ascorbic acid and uric acid.

    更新日期:2017-08-24
  • A water-stable lanthanide metal-organic framework for fluorimetric detection of ferric ions and tryptophan
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-13
    Hani Nasser Abdelhamid, Antonio Bermejo-Gómez, Belén Martín-Matute, Xiaodong Zou

    The preparation of a highly water stable and porous lanthanide metal-organic framework (MOF) nanoparticles (denoted SUMOF-7II; SU refers to Stockholm University) is described. SUMOF-7II was synthesized starting from the tritopic linker of 2,4,6-tri-p-carboxyphenyl pyridine (H3L2) and La(III) as metal clusters. SUMOF-7II forms a stable dispersion and displays high fluorescence emission with small variation over the pH range of 6 to 12. Its fluorescence is selectively quenched by Fe(III) ions compared to other metal ions. The intensity of the fluorescene emission drops drops linearly in 16.6–167 μM Fe(III) concentration range, and Stern-Volmer plots are linear. The limit of detection (LOD) is 16.6 μM (at an S/N ratio of >3). This indicator probe can also be used for selective detection of tryptophan among several amino acids. Compared to the free linker H3L2, SUMOF-7II offers improved sensitivity and selectivity of the investigated species.

    更新日期:2017-08-24
  • Electrochemical indirect competitive immunoassay for ultrasensitive detection of zearalenone based on a glassy carbon electrode modified with carboxylated multi-walled carbon nanotubes and chitosan
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-09
    Wei Xu, Ying Qing, Shuai Chen, Jun Chen, Zhen Qin, JingFu Qiu, ChaoRui Li

    The authors describe an electrochemical immunoassay for ultrasensitive detection of the mycotoxin zearalenone (ZEA). A nanocomposite was prepared from carboxy-functionalized multi-walled carbon nanotubes and chitosan (cMWCNTs/Chit). The morphology and electrochemical performance of the materials was characterized by field-emission scanning electron microscopy, atomic force microscopy, differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. In this assay, ZEA–BSA conjugated covalently to activated cMWCNTs/Chit film, then the indirect competition between ZEA–BSA and free ZEA when immobilization of excess anti-ZEA. The secondary antibody is labeled with the enzyme alkaline phosphatase which can hydrolyze the substrate 1-naphthylphosphate to produce 1-naphthol which gives a stable and strong anodic electrochemical signal at a low working voltage of 0.3 V (vs. Ag/AgCl). The use of the modified GCE results in a strongly enhanced electrochemical current response. Compared with conventional methods, the established immunosensor exhibited a high level of sensitivity. Under optimal conditions, this immunoassay can quantify ZEA in the 10 pg·mL−1 to 1000 ng·mL−1 concentration range with a detection limit of 4.7 pg·mL−1 and the sensitivity is 0.51 μA·μM−1·cm−2. The method was applied to the determination of ZEA in cereal and feedstuff samples. Results showed satisfactory recovery and good consistency with high-performance liquid chromatography. Therefore, the indirect competitive electrochemical immunosensor provide a viable tool based on bioanalysis.

    更新日期:2017-08-24
  • Screen-printed electrode modified with a composite prepared from graphene oxide nanosheets and Mn 3 O 4 microcubes for ultrasensitive determination of nitrite
    Microchim. Acta (IF 4.58) Pub Date : 2017-07-01
    Akilarasan Muthumariappan, Mani Govindasamy, Shen-Ming Chen, Kogularasu Sakthivel, Veerappan Mani

    The authors describe a screen-printed electrode (SPE) modified with a composite consisting of Mn3O4 microcubes and thin sheets of graphene oxide for use in amperometric determination of nitrite. The composite was prepared by a hydrothermal method, and its morphology, elemental composition, diffraction, impedance and electrochemical properties were studied. The modified SPE displays excellent electrocatalytic activity towards nitrite, and the oxidation peak current (measured typically at 0.70 V vs. Ag/AgCl) is related to the concentration of nitrite in the range between 0.1 and 1300 μM, with a 20 nM detection limit. The method was successfully applied to the determination of nitrite in spiked samples of beef and water.

    更新日期:2017-08-24
  • Amperometric determination of the activity of protein kinase a using a glassy carbon electrode modified with IgG functionalized gold nanoparticles conjugated to horseradish peroxidase
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-06
    Yunlei Zhou, Minghui Wang, Huanshun Yin, Shiyun Ai

    The authors describe the fabrication of an electrochemical immunosensor for the determination of the activity of protein kinase A (PKA). The method involves (a) electrochemical deposition of gold nanoparticles (AuNPs) on a glassy carbon electrode, (b) PKA-induced catalytic phosphorylation of serine, and (c) the use of phosphoserine antibody and horseradish peroxidase conjugated to IgG on gold nanoparticles (HRP-IgG-AuNPs). The use of AuNPs and HRP-IgG-AuNPs results in large amplification so that the method, at a typical working potential as low as 0.08 V (vs. SCE), has a linear range that extends from 0.1 to 50 activity units per mL, and the detection limit is 0.026 units per mL (at an S/N ratio of 3). The assay is selective (not the least due to a rather low working potential) and well reproducible. It may also be applied to screening for PKA inhibitors and to quantify the PKA activity in human cell lysates.

    更新日期:2017-08-24
  • An aptamer based sulfadimethoxine assay that uses magnetized upconversion nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-27
    Xiuying Liu, Tengfei Gao, Xue Gao, Tao Ma, Yiwei Tang, Lijie Zhu, Jianrong Li

    The authors describe an aptamer based method for the determination of the antibiotic sulfadimethoxine (SLF). It is making use of upconversion nanoparticles (UCNPs) that act as an internal fluorophors signals, and of aptamers that can specifically recognize SLF. The UCNPs were deposited on the surface of magnetic nanoparticles (magNPs) functionalized with the aptamer. In the presence of SLF, parts of the UCNPs dissociate from the surface of the magNPs, and this results in decreased fluorescence intensity. The findings were exploited to design a fluorometric assay for SLF that has a 0.11 ng·mL−1 detection limit. The method was successfully applied to the quantification of SLF in spiked samples of perch and catfish. Recoveries range from 80.3% to 92.7%, and RSDs from 2.4% to 3.6%.

    更新日期:2017-08-24
  • Ultrathin two-dimensional MnO 2 nanosheet as a stable coreactant of 3,3′,5,5′-tetramethylbenzidine chromogenic substrate for visual and colorimetric detection of iron(II) ion
    Microchim. Acta (IF 4.58) Pub Date : 2017-06-15
    Hu Song, Yunhan Wang, Guanquan Wang, Hongyuan Wei, Shunzhong Luo

    The authors report on a chromogenic system based MnO2 nanosheet and the chomgenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB). The MnO2 nanosheet can oxidize TMB in acidic environment to form a yellow solution with an absorption peak at 450 nm. The process does not require the presence of an enzyme or H2O2. However, on addition of ferrous ion to the chromogenic system, the MnO2 nanosheet is decomposed via the redox reaction that occurs between Fe(II) and MnO2. As a result, the intensity of the absorption at 450 nm is reduced. This finding is exploited in a photometric method for determination of Fe(II) that shows high selectivity and a 0.3 μM detection limit (based on the 3σ/slope criterion). Fe(II) can also be detected visually in concentrations down to 100 μM. The method was applied to the determination of Fe(II) in spiked water samples and gave satisfactory recoveries.

    更新日期:2017-08-24
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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