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  • A carbon ceramic electrode modified with bismuth oxide nanoparticles for determination of syringic acid by stripping voltammetry
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-13
    Justyna Robak, Krystian Węgiel, Barbara Burnat, Sławomira Skrzypek

    A new type of carbon ceramic electrode modified with bismuth oxide nanoparticles (referred to as Bi-CCE) was fabricated via the sol-gel method. The Bi-CCE was applied to the determination of syringic acid by square wave adsorptive stripping voltammetry. The electrochemical properties of the Bi-CCE and the voltammetric response to syringic acid were investigated by cyclic voltammetry. The effects of the pH value of supporting electrolyte, of accumulation potential, accumulation time, SW mode parameters, and of possible interferents were tested. Under optimized conditions, the oxidation peak current (best measured at 0.8 V vs Ag/AgCl after an accumulation time of 20 s) increases linearly in the 0.4 to 24 μmol·L−1 syringic acid concentration range. Other figures of merit include an LOD of 47 nmol·L−1, a sensitivity of 3.3 μA·μmol−1·L·cm−2, and a relative standard deviation of 4.7% (for n = 5) at 2 μmol·L−1 of syringic acid. The method was successfully applied to the determination of syringic acid in red, white and rose wine as well as water samples.

    更新日期:2017-11-10
  • Non-enzymatic sensing of hydrogen peroxide using a glassy carbon electrode modified with the layered MoS 2 -reduced graphene oxide and Prussian Blue
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-13
    Zhenyu Cheng, Qihui Shen, Huashi Yu, Dandan Han, Fangli Zhong, Yingjie Yang

    The authors describe an electrochemical sensor for hydrogen peroxide (H2O2). It was constructed by consecutive, selective modification of a glassy carbon electrode (GCE) with Prussian Blue (PB), layered molybdenum disulfide (MoS2), and reduced graphene oxide (rGO). The properties of the modified GCE were characterized via high-resolution transmission electron microscopy, UV-vis spectroscopy and X-ray diffraction. The electrochemical properties of the electrode were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The sensor exhibits excellent electrocatalytic activity for the reduction of hydrogen peroxide in comparison to GCEs modified with MoS2-rGO or PB only. Response is linear in the 0.3 μM to 1.15 mM H2O2 concentration range at a working analytical voltage of 0.1 V, with a 0.14 μM detection limit. The electrochemical sensitivity is 2883.5 μA·μM−1·cm−2, and response is fast (<10 s). The sensor is selective, stable and reproducible. This is attributed to the efficient electron transport properties of the MoS2-rGO composite and the high loading with PB.

    更新日期:2017-11-10
  • Non-enzymatic amperometric hydrogen peroxide sensor using a glassy carbon electrode modified with gold nanoparticles deposited on CVD-grown graphene
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-20
    Yawen Yuan, Yiqun Zheng, Jinglei Liu, Hua Wang, Shifeng Hou

    A glassy carbon electrode (GCE) was modified with gold nanoparticles (AuNPs) coated on monolayer graphene (AuNP/MG) by direct in situ sputtering of AuNPs on CVD-generated graphene. This process avoids complicated polymer transfer and polymer cleaning processes and affords AuNPs with a clean surface. The monolayer graphene is ductile and well dispersed. The clean surface of the AuNPs renders this sensor superior to GCEs modified with AuNPs on reduced graphene oxide in terms of the amperometric non-enzymatic determination of hydrogen peroxide. The detection limit is 10 nM (S/N = 3) at 0.55 V (vs. SCE), which is lower than that for similar methods, and the response time is as short as 2 s. Another attractive feature of the sensor is its feasibility for large-scale production via CVD and sputtering.

    更新日期:2017-11-10
  • Off-on-off detection of the activity of acetylcholine esterase and its inhibitors using MoOx quantum dots as a photoluminescent probe
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-19
    Sai Jin Xiao, Zhao Jun Chu, Xiao Jing Zhao, Zhi Bin Zhang, Yun Hai Liu

    The authors describe a fluorometric "off-on-off" method for the determination of the activity of acetylcholine esterase (AChE). Molybdenum oxide quantum dots (QDs) are used as a fluorescent probe having excitation/emission peaks at 405/525 nm. It is found that the photoluminescence of such QDs is quenched by Cu(II) ion but that it can be restored by acetylcholine which is formed by AChE-catalyzed hydrolysis of acetylthiocholine. The effect is due to the strong affinity between Cu(II) and the thiol group of acetylthiocholine. Hence, quenching is increasingly reversed with increasing concentrations of AChE. However, fluorescence is not restored if the activity of AChE is inhibited by an inhibitor. Under optimal conditions, a linear relationship is founded in the 0.05 to 15 mU·mL−1 AChE activity range, with a limit of detection of 35 μU·mL−1 (applying the 3σ/k criterion). Three organophosphate pesticides and propazine were used to validate the assay. All showed strong inhibition, with IC50 values (the concentration required for 50% inhibition to occur) to be 52, 221, 48 and 9 nM for diazinon, chlorpyriphos, monocrotophos and propazine. Benefitting from its sensitivity, specificity and simplicity, the assay in our perception provides a valuable tool for detection of AChE activity and in screening for its inhibitors.

    更新日期:2017-11-10
  • Ultra-sensitive voltammetric simultaneous determination of dopamine, uric acid and ascorbic acid based on a graphene-coated alumina electrode
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-15
    Masoud Taleb, Roman Ivanov, Sergei Bereznev, Sayed Habib Kazemi, Irina Hussainova

    The authors describe the fabrication of an interconnected edge-exposed graphene nanostructure via chemical vapor deposition (CVD) of foliated graphene onto a network of alumina nanofibers. The fibers such obtained are shown to enable ultra-sensitive voltammetric determination of dopamine (DA), uric acid (UA) and ascorbic acid (AA). The electrode displays powerful and persistent electro oxidative behavior and excellent electron transport properties. Cyclic voltammetry and differential pulse voltammetry demonstrate excellent selectively and sensitivity for AA, DA and UA, with typical peaks at −0.08 V, +0.19 V, and +0.34 V (vs. SCE), respectively. Under optimum conditions, the calibration plots are linear in the 1–80 μM range for DA, in the 1–60 μM range for UA, and in the 0.5–60 μM range for UA, with detection limits of 0.47 μM, 0.28 μM and 0.59 μM, respectively. The sensor was successfully applied to the simultaneous determination of DA and UA in the presence of AA in spiked urine sample.

    更新日期:2017-11-10
  • Dual-functional aluminum(III)-based electrochemiluminescent detection of gene mutation
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-15
    Yan Hao, Bin Zhou, Yanjuan Tang, Peihui Yang

    A novel electrochemiluminescent (ECL) method for highly sensitive detection of gene mutations was designed based on the amplification strategy of dual-functional aluminum(III). A film composed of nafion and polyaniline (Nafion-PANI) was placed onto glassy carbon electrode (GCE) in order to improve conductivity and stability, and then cadmium sulfide quantum dots (CdS QDs) were attached as an ECL label. Al(III) was introduced in order to enhance the ECL signal intensity of the CdS QDs by filling the surface electronic defects of CdS QDs. The Al(III) ions also assist by improving sensitivity by promoting the electron transfer at the GCE and by retaining plenty of single-stranded DNA (ssDNA). The ECL is generated at typically −1.5 V in the presence of containing K2S2O8. Compared to conventional ECL based DNA biosensors, the one described here – based on the use of dually functional Al(III) ions – enables ssDNA to be detected in the 1 f. to 10 nM concentration range, with a 6 f. detection limit. This method was applied to the quantitation of target ssDNA with different mismatching status in human serum. In our perception, it represents a highly attractive tool for the detection of ssDNA and has a particular potential in the diagnosis of hereditary diseases.

    更新日期:2017-11-10
  • A glassy carbon electrode modified with carbon nanotubes and reduced graphene oxide decorated with platinum-gold nanoparticles for voltammetric aptasensing of urea
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-19
    Hamed Momenzadeh, Azadeh Azadbakht

    This article reports on a novel aptamer-based platform for the quantitation of urea by using an aptamer with high affinity and selectivity for urea. The surface of a glassy carbon electrode (GCE) was modified by drop casting a cocktail consisting of carbon nanotubes and reduced graphene oxide (rGO) decorated with platinum-gold nanoparticles. The urea aptamer was then immobilized on the nanocomposite via covalent conjugation. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to trace the modification of the GCE. Binding of urea caused the aptamer to be folded, and this result in an inhibition of the interfacial charge transfer rate when using hexacyanoferrate as an electrochemical redox probe. The change in redox current was quantified by differential pulse voltammetry, typically at a working voltage of 0.22 V vs. Ag/AgCl. The assay has a 1.9 pM detection limit, and the response is linear up to 150 nM concentration of urea. The superior selectivity and affinity of aptamer-modified GCE makes it a most useful tool for analysis of urea present in very low concentrations.

    更新日期:2017-11-10
  • Chemoresistive sensor for hydrogen using thin films of tin dioxide doped with cerium and palladium
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-30
    Revathy Deivasegamani, Govardhan Karunanidhi, Chella Santhosh, Tamilselvi Gopal, Divyalakshmi Saravana achari, Ajita Neogi, Ravi Nivetha, Natarajan Pradeep, Uma Venkatraman, Amit Bhatnagar, Soon Kwan Jeong, Andrews Nirmala Grace

    This work reports on the development of thin films of SnO2 doped with cerium and palladium and shows them to be viable materials for chemoresistive sensing of hydrogen (H2). The sensing material was synthesized by a hydrothermal route and with different weight percentage loadings of the dopants. The structural and morphological features were investigated by X-ray diffraction, field emission scanning electron microscopy, FTIR and X-ray photoelectron spectroscopy. Thin films were fabricated by spin coating on a ceramic substrate. The change in the resistance of the film was measured as a function of the concentration of H2. The results show that the amount of loading with Ce and Pd has a large effect on the performance. The Ce doped nanocomposite sensor has a lower detection limit of 50 ppm of H2 and covers the 50 to 500 ppm H2 concentration range if operated at the optimum temperature of 200 °C and a working voltage of 5 V.

    更新日期:2017-11-10
  • Classifying the polarity of organic solvent mixtures by using Hostalene Red adsorbed on nanosized zeolite as a fluorescent probe
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-18
    Peng Li, Tingting Zhao, Huanrong Li

    A method is described for the determination of the polarity of mixed organic solvents by using the fluorescent probe Hostasol Red (HR) desposited on the outer surface of nanosized zeolite L. Organic solvents and their mixtures can be roughly classified according to their polarity with bare eyes and fluorometrically. Emission peaks range from 520 to 640 nm. Some solvents act as quenchers. The method is studied with series of protic and nonprotic solvents, and with selected mixtures of organic solvents.

    更新日期:2017-11-10
  • Detection of cyanide via extended π-conjugation-induced fluorescence enhancement of a metal organic framework composed of terbium(III), bipyridyl and adenosine diphosphate
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-15
    Lude Wang, Shaoxuan Wang, Yang Chen

    A metal-organic framework (MOF) was designed and prepared from luminescent Tb(III), adenosine diphosphate (ADP) and bipyridyl (Bipy). Its green fluorescence at 545 nm is shown to enable the fluorometric detection of cyanide ion based on the principle of π-conjugation-induced fluorescence enhancement. The fluorescence of the probe is strongly increased by cyanide due to extended π-conjugation between probe MOF and cyanide which sensitizes the fluorescence of Tb(III). This effect can be used to quantify cyanide at levels as low as 30 nM in aqueous solution. The method was applied to the determination of cyanide in saliva samples. The lack of interference by acetate and fluoride is a specific feature of this method. The method based on the principle of π-conjugation-induced fluorescence enhancement provides a new sensing way for widely used fluorescence assays.

    更新日期:2017-11-10
  • Integrated microfluidic platform for rapid antimicrobial susceptibility testing and bacterial growth analysis using bead-based biosensor via fluorescence imaging
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-15
    Pooja Sabhachandani, Saheli Sarkar, Paola C. Zucchi, Betsy A. Whitfield, James E. Kirby, Elizabeth B. Hirsch, Tania Konry

    The paper describes a droplet-based microfluidic method for phenotypic-based antimicrobial susceptibility testing (AST). In particular, this micro-droplet-based phenotypic assay evaluates susceptibility of different bacterial strains towards antibiotics by tracking effects on individual bacterial cells, including changes in bacterial cell number and morphology. The platform was validated by applying the method to test the responses of E. coli ATCC 25922 and 6937 (a clinical isolate), in spiked urine samples at a concentration of 5 × 104 cfu mL−1, to the antibiotics ceftazidime and levofloxacin. Both E. coli strains showed dose-dependent inhibition of bacterial replication and morphological alteration. These correlated well with minimal inhibitory concentrations determined by the reference broth microdilution method. Discrete bacterial divisions and morphological changes were observed within 20 min of on-chip incubation, demonstrating performance of rapid AST directly on urine samples. As proof-of-concept, specific bead-based biosensors were tested for capture and detection of E. coli for on-bead proliferation. The method has the attractive feature of allowing the detection of at least one bacterium per bead in less than 30 min. It can potentially be used to isolate a specific bacterial strain directly from patient urine samples for AST monitoring.

    更新日期:2017-11-10
  • Fluorometric determination of microRNA via FRET between silver nanoclusters and CdTe quantum dots
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-20
    Yasaman-Sadat Borghei, Morteza Hosseini, Mohammad Reza Ganjali

    This paper describes a CdTe quantum dot-based fluorescence resonance energy transfer (FRET) based assay for the detection of the breast cancer biomarker microRNA. The method relies on energy transfer between DNA-templated silver nanoclusters (AgNCs) and CdTe QDs. Interaction between double strand oligonucleotide and QDs can be detected qualitatively through gel analysis and quantitatively by the signal amplification from AgNCs to QDs via FRET, best measured at an excitation wavelength of 350 nm and at emission wavelengths of 550 and 590 nm. Three microRNAs (microRNA-21, microRNA-155 and Let-7a) were quantified to verify the feasibility of the method, and a high sensitivity for microRNAs was achieved. Fluorescence intensity increases linearly with the log of the concentration of microRNA 155 in the 5.0 pM to 50 nM range, with a 1.2 pM detection limit.

    更新日期:2017-11-10
  • DNA nanomachine-assisted magnetic bead based target recycling and isothermal amplification for sensitive fluorescence determination of interferon-γ
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-31
    Weiwei Chen, Xueen Fang, Xin Ye, Hua Li, Hongmei Cao, Jilie Kong

    The authors describe a protein-triggered self-assembling DNA nanomachine for the detection of interferon-γ (IFN-γ), an important cytokine associated with immuno response. The DNA nanoprobe exhibits good specificity and sensitivity for interferon-γ (IFN-γ) detection. In the presence of the target (IFN-γ), four functional DNA probes are assembled to form a DNA nanocomplex. It promotes the release of the target for recycling. The captured DNA probe (biotinylated-C1) is then brought into contact with streptavidin-functionalized magnetic beads (sa-MB). These cause the dissociation of the B3 primer signal probe (S1) from the reaction solution which then is available for loop-mediated isothermal amplification (LAMP) analysis. As the deficiency of the B3 primer inhibits the LAMP reaction, the resulting point of inflexion (POI) value (the starting point of LAMP) is increased. In the absence of IFN-γ, the operation of the DNA nanomachine is not triggered, and the LAMP reaction remains unaffected. In this way, the POI values indirectly report the concentration of IFN-γ. The feasibility of the protein-driven DNA nanomachine was first demonstrated by the gel electrophoresis and real-time fluorescence analysis. Then, under optimal conditions, IFN-γ in concentrations as low as 5 ng·mL−1 can be quantified, and the detection limit is 2.3 ng·mL−1. Besides, this strategy can effectively discriminate IFN-γ from other proteins and displayed acceptable recoveries even in serum samples. In our perception, this approach holds great promise as it may be adapted to detect numerous other proteins.

    更新日期:2017-11-10
  • Comparative evaluation of the performance of electrochemical immunosensors using magnetic microparticles and nanoparticles. Application to the determination of tyrosine kinase receptor AXL
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    V. Serafín, R. M. Torrente-Rodríguez, M. Batlle, P. García de Frutos, S. Campuzano, P. Yáñez-Sedeño, J. M. Pingarrón

    Electrochemical sandwich immunoassay strategies involving the use of carboxyl-functionalized magnetic microbeads (cMBs) and magnetic nanoparticles (cMNPs) have been evaluated and compared. The proteolytically cleaved soluble tyrosine kinase receptor sAXL was used as the target analyte. Antibodies against AXL were covalently immobilized on cMBs or cMNPs. Immunobinding of AXL was detected by means of a secondary biotinylated antibody and a streptavidin-horseradish peroxidase conjugate. The electrochemical transduction was accomplished by capturing the cMBs or cMNPs bearing the immunoconjugates onto screen-printed carbon electrodes (SPCEs) by using a small magnet. The amperometric response was measured at −0.20 V (vs the silver pseudo-reference electrode of the SPCE) upon the addition of H2O2 in the presence of hydroquinone as the redox mediator. The calibration plots for AXL extended up to 7.5 ng mL−1 when cMBs were used for the preparation of the immunosensor and up to 40 ng mL−1 in the case of using cMNPs. The respective slope values were 158 (cMBs) and 43 nA mL ng−1 (cMNPs), while the achieved LODs were 74 (cMBs) and 75 pg mL−1 (cMNPs). Although the immunosensors prepared with cMBs provided a shorter range of linearity, they exhibited a 3.7-times larger sensitivity than those constructed with cMNPs. The successful application of the new strategies was demonstrated for the determination of the endogenous content of sAXL in real human serum samples (a cut-off value of 71 ng mL−1 have been established for patients with risk of heart failure). The immunosensors constructed using cMBs or cMNPs can be advanta geously compared, in terms of sensitivity and fabrication time, with the only immunosensor for AXL previously reported. In addition, these new immunosensors took approximately half time than ELISA to perform the assay.

    更新日期:2017-10-13
  • Controlled etching of gold nanorods by the Au(III)-CTAB complex, and its application to semi-quantitative visual determination of organophosphorus pesticides
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-30
    Shuo Wu, Dandan Li, Zhanming Gao, Jiamian Wang

    The authors describe a semi-quantitative colorimetric method for visual detection of organophosphorus pesticides (OPs). It is based on the aspect ratio dependent absorbance of gold nanorods (AuNRs) which is due to the localized surface plasmon resonance. The aspect ratio can be tailored by the Au(III) complex formed with cetyltrimethylammonium bromide (CTAB) which is affected by acetylcholinesterase (AChE) based hydrolysis. OPs act as inhibitors of this reaction. In the absence of OPs, the product (thiocholine) of enzymatic hydrolysis consumes almost all the Au(III) species. In this case, the amount of residual Au(III)-CTAB complexes is small, and etching of the AuNRs does not occur. In the presence of OPs, however, the activity of AChE is inhibited. Hence, only small quantities of (or no) thiocholine is produced, and Au(III) is not consumed. Au(III) is capable of etching AuNRs and to change their aspect ratio. This leads to a color change from brownish to gray, cyan, green, blue, purple, red, and colorless that can be easily observed with bare eyes. The AuNRs were incorporated into cellulose paper to obtain a paper stripe for visual detection of OPs. Under optimal conditions, both methods (AuNRs in aqueous solutions and on paper) allowed various OPs to be determined. Applied to parathion, the method had a detection limit as low as 1.2 ppb and a linear range from 0.01 to 1.84 ppm. It was applied to the analysis of cabbage washing solutions and sea water samples, and acceptable accuracy and good resolution were found. In our preconception, the method represents a valuable tool for on-site detection of OPs in agriculture products and food.

    更新日期:2017-10-13
  • Fluorometric determination of microRNA based on strand displacement amplification and rolling circle amplification
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-30
    Yunlei Zhou, Bingchen Li, Minghui Wang, Jun Wang, Huanshun Yin, Shiyun Ai

    The authors describe a fluorometric assay for microRNA. It is based on two-step amplification involving (a) strand displacement replication and (b) rolling circle amplification. The strand displacement amplification system is making use of template DNA (containing a sequence that is complementary to microRNA-21) and nicking enzyme sites. After hybridization, the microRNA strand becomes extended by DNA polymerase chain reaction and then cleaved by the nicking enzyme. The DNA thus produced acts as a primer in rolling circle amplification. Then, the DNA probe SYBR Green II is added to bind to ssDNA to generate a fluorescent signal which increases with increasing concentration of microRNA. The method has a wide detection range that covers the10 f. to 0.1 nM microRNA concentration range and has a detection limit as low as 1.0 fM. The method was successfully applied to the determination of microRNA-21 in the serum of healthy and breast cancer patients.

    更新日期:2017-10-13
  • Aptamer-based zearalenone assay based on the use of a fluorescein label and a functional graphene oxide as a quencher
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-30
    K. Yugender Goud, Akhtar Hayat, M. Satyanarayana, V. Sunil Kumar, Gaëlle Catanante, K. Vengatajalabathy Gobi, Jean Louis Marty

    A versatile and cost-effective aptamer-based fluorescence quenching assay is described for the detection of the mycotoxin zearalenone (ZEN). Exfoliated functional graphene oxide (FGO) of high water-dispersibility is adopted as an effective fluorescence quencher of the fluorescence of FAM. Quenching properties of graphite, graphene oxide (GO) and FGO were investigated, and FGO is found to be the most efficient quencher. FGO therefore was used in an aptamer-based detection format that allows ZEN to be determined in the concentration range of 0.5 to 64 ng·mL−1 with a limit of detection of 0.5 ng·mL−1. The aptamer assay has good repeatability and reproducibility (n ≥ 4). Selectivity of the aptamer assay against a set of possible interferents is substantiated. This aptasensing assay was successfully applied to the determination of ZEN in (spiked) alcoholic beverage samples, beer and wine, and recovery values in the range of 87 to 96% were obtained for the determination of ZEN at levels as low as 1–16 ng mL−1.

    更新日期:2017-10-13
  • Visual and rapid lateral flow immunochromatographic assay for enrofloxacin using dyed polymer microspheres and quantum dots
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-26
    Wei Sheng, Shijie Li, Yue Liu, Junping Wang, Yan Zhang, Shuo Wang

    The authors describe two kinds of immunochromatographic assays. The first is based on the use of dyed polymer microspheres (MICA), the another on the use of quantum dots (QICA). Both enable visual detection of enrofloxacin (ENR) in animal tissue and milk. Both the MICA and the QICA have visual limits of detection of 1 μg·L−1 when working in buffer, of 5 μg·kg−1 in case of animal tissue, and of 10 μg·L−1 in case of milk. Other quinolones do not interfere. The MICA and QICA described here are convenient and fairly rapid in that the detection process (including sample pretreatment and assay) takes 20 min only which is far less than the commercial enzyme-linked immunosorbent assay (ELISA) test kit which requires 120 min. The MICA and QICA are more sensitive than the immunochromatographic assay using colloidal gold labels and the same polyclonal antibody. The results of analysis of spiked samples via MICA and QICA are in good agreement with those obtained by the commercial ELISA test kit.

    更新日期:2017-10-13
  • Orientation selection of broad-spectrum aptamers against lipopolysaccharides based on capture-SELEX by using magnetic nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    Hua Ye, Nuo Duan, Shijia Wu, Guiliang Tan, Huajie Gu, Jinghong Li, Haitao Wang, Zhouping Wang

    The authors describe a new kind of selection method (referred to as orientation selection) for improved screening for broad-spectrum lipopolysaccharides (LPSs) using unlabeled ssDNA aptamers. The method is based on the capture-SELEX technique using magnetic nanoparticles. LPS from Salmonella enterica serotype typhimurium was chosen as an exemplary target. Once the ssDNA library is preconcentrated to a certain degree, two Gram-negative bacteria were used as orientation molecules in the subsequent selection process. Using this strategy, one optimal aptamer ('EA7') was captured that has a high affinity (Kd = 102 ± 17 nM) for LPS and it was also confirmed that it can recognize three other bacterial LPSs. It is presumed that EA7 binds to the lipid A region of LPS. When using carboxyfluorescein labeled EA7, the observed fluorescence intensity and concentrations of four types of LPSs in drinking water are linearly correlated. The lower detection limit of the LPS is 3 ng·mL−1. Compared to multi-target mixed selection and conventional SELEX methods, the new orientation selection strategy produces results that are less uncertain.

    更新日期:2017-10-13
  • A printed SWCNT electrode modified with polycatechol and lysozyme for capacitive detection of α-lactalbumin
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-29
    Amal Raouafi, Amal Rabti, Noureddine Raouafi

    The authors describe an electrochemical sensor for the breast cancer marker α-lactalbumin (αLA). It is based on the use of printed single-walled carbon nanotube (SWCNT) electrodes that were modified with polycatechol. Impedance-derived electrochemical capacitance spectroscopy (ECS) is applied for detection at an applied potential of −0.14 V vs. Ag/AgCl reference electrode. The electrode was prepared in a two-step process. First, a dispersion of SWCNTs was drop-cast onto the surface of a poly(ethylene terephthalate) substrate to act as the working electrode. Next, catechol was electrochemically polymerized on the SWCNTs, prior to the immobilization of lysozyme. The strong interaction between lysozyme and αLA induced changes in the redox capacitance which are detected by ECS. The latter shows the device to be capable of detecting αLA in the 20 to 80 ng·mL−1 concentration range. The limit of detection is 9.7 ng·mL−1 at an S/N ratio of 3. The device was used to detect αLA in human blood serum with good recovery results.

    更新日期:2017-10-13
  • Visual detection of ultra-trace levels of uranyl ions using magnetic bead-based DNAzyme recognition in combination with rolling circle amplification
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    Xian Cheng, Xinhui Yu, Lian Chen, Hongyan Zhang, Yongning Wu, FengFu Fu

    The authors describe a colorimetric method for the determination of ultra-trace levels of uranyl ion (UO22+) in beverage and milk. It employs (a) DNAzyme-functionalized magnetic beads (MBs) for UO22+ recognition, (b) horseradish peroxidase (HRP)-assisted catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) for signal generation, and (c) rolling circle amplification (RCA) for sensitivity improvement. The employment of DNAzyme-functionalized MBs facilitates the separation and collection of analyte from sample matrix. This results in more convenient operation, better selectivity and more strong resistibility to sample matrix. The RCA strategy realizes one UO22+-to-massive HRP effect, which strongly improves the sensitivity. The method has outstanding advantages including high sensitivity, convenient operation, strong resistibility to complex matrix, and good selectivity. It can be used to detect as low as 20.0 pg·mL−1 (74 pmol·L−1) of UO22+ in milk and beverage by bare eye observation. Even lower concentrations (1.0 pg·mL−1 or 3.7 pmol·L−1) of UO22+ can be detected with the method via UV-visible spectrometry at 650 nm. The method was applied to analyze spiked samples and gave recoveries of 98 to 105% and RSDs of ±7% (n = 6). The visual detection limit is much lower than the maximum allowable level of UO22+ in drinking water as defined by the Environmental Protection Agency of USA. This indicated that the method meets the requirement of simple, rapid and on-site detection of ultra-trace UO22+ in milk and beverage.

    更新日期:2017-10-13
  • Lateral flow test for visual detection of silver(I) based on cytosine-Ag(I)-cytosine interaction in C-rich oligonucleotides
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    Zebin Guo, Yafeng Zheng, Hui Xu, Baodong Zheng, Wanwei Qiu, Guodong Liu

    The authors describe an oligonucleotide-based lateral flow test for visual detection of Ag(I). The assay is based on cytosine-Ag(I)-cytosine [C-Ag(I)-C] coordination chemistry to capture gold nanoparticle (AuNP) tags in the test zone. A thiolated C-rich oligonucleotide probe was immobilized on the AuNPs via gold-thiol chemistry, and a biotinylated C-rich oligonucleotide probe was immobilized on the test zone. The AuNPs labelled with C-rich oligonucleotides are captured by Ag(I) ions in the test zone through the C-Ag(I)-C coordination. The resulting accumulation of AuNPs produces a readily visible red band in the test zone. Under optimized conditions, the test is capable of visually detecting 1.0 ppb of Ag(I) which is 50 times lower than the maximum allowable concentration as defined by the US Environmental Protection Agency for drinking water. Hence, the test is inexpensive and highly sensitive. It was applied to the detection of Ag(I) in spiked samples of tap water and river water. In our perception, the test is a particularly valuable tool in limited resource settings.

    更新日期:2017-10-13
  • An antibacterial microfluidic system with fish gill structure for the detection of Staphylococcus via enzymatic reaction on a chromatic polydiacetylene material caused by lysostaphin
    Microchim. Acta (IF 4.58) Pub Date : 2017-09-18
    Huisoo Jang, Palan Lee, Seokjae Kim, Sun Min Kim, Tae-Joon Jeon

    The authors describe a microfluidic system functionalized with a chromatic nanomaterial (polydiacetylene; PDA) and conjugated to the antimicrobial enzyme lysostaphin (LST) as a means for specific detection of Staphylococcus pathogens and to simultaneously perform antimicrobial functions. The LST-loaded PDA vesicles were deposited in a fish gill-like structure on the inner surface of the microchannels. They undergo a color transition from blue to red and enhancement of fluorescence under external mechanical stimulus that is caused by the interaction between Staphylococcus and LST which has antimicrobial activity against Staphylococcus. Due to its fish gill-mimicking structure, the PDA coated channel has a high surface-to-volume ratio, and this maximizes the binding efficiency between Staphylococcus suspended in the fluid and the LST-PDA coating on the microchannels. Consequently, >80% of the Staphylococcus are eliminated in the channels within a short reaction time. As a result, the LST-PDA-coated channel surfaces undergoes color change from blue to red, and red fluorescence pops up. In contrast, no enzymatic reaction and no color transition is observed when an E. coli suspension is applied. The results show that this multifunctional microfluidic system can specifically detect, and can exert an antimicrobial effect on, Staphylococcus.

    更新日期:2017-10-13
  • Nanoparticles of type Fe 3 O 4 -SiO 2 -graphene oxide and coated with an amino acid-derived ionic liquid for extraction of Al(III), Cr(III), Cu(II), Pb(II) prior to their determination by ICP-OES
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    Weixi Gu, Xiashi Zhu

    An amino acid derived ionic liquid, Fe3O4 nanoparticles and graphene oxide (GO) were used to prepare a material for the magnetic solid phase extraction (MSPE) of the ions Al(III), Cr(III), Cu(II) and Pb(II). The material was characterized by Fourier transform infrared spectral (FT-IR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), magnetic analysis and isoelectric point (pI) analysis. It is shown to be a viable sorbent for the separation of these metal ions. Single factor experiments were carried out to optimize adsorption including pH values, ionic strength, temperature and solution volume. Following desorption with 0.1 M HCl, the ions were quantified by inductively coupled plasma optical emission spectrometry. Under the optimum conditions, the method provides a linear range from 10 to 170 μg· L−1 for Al(III); from 4.0 to 200 μg· L−1 for Cr(III); from 5.0 to 170 μg· L−1 for Cu(II); and from 5.0 to 200 μg· L−1 for Pb(II). The limits of detection (LOD) are 6.2 ng L−1 for Al(III); 1.6 ng L−1 for Cr(III); 0.52 ng L−1 for Cu(II); and 30 ng L−1 for Pb(II). Method performance was investigated by determination of these ions in (spiked) environmental water and gave recoveries in the range of 89.1%–117.8%.

    更新日期:2017-10-13
  • A portable microreactor with minimal accessories for polymerase chain reaction: application to the determination of foodborne pathogens
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-23
    Kieu The Loan Trinh, Nae Yoon Lee

    The authors describe a microreactor for performing a multiplexed polymerase chain reaction (PCR) which is operated with minimal accessories such as a single heater for gene amplification and a hand-held syringe for sample actuation. It was fabricated by wrapping a polytetrafluoroethylene (PTFE) tube around a rectangular poly(dimethylsiloxane) (PDMS) block having a predetermined thickness. The resulting portable microreactor was applied to PCR using a single heater because the rectangular PDMS block spatially segregated the upper and lower arrays of the PTFE tube. This warrants the adjustment of distinct temperatures inside the upper and lower tubes. A hand-held plastic syringe was connected to the inlet of the PTFE tube and used as a portable pump to achieve a homogeneous transport of a sample liquid inside the microreactor. The use of gas-impermeable PTFE prevents the formation of bubbles during thermal cycling. The microreactor was successfully applied to the amplification of typical DNA fragments of three foodborne pathogens in less than 30 min. In our perception, this method paves the way to the construction of a truly portable PCR chip that is applicable to rapid clinical diagnosis and the detection of foodborne pathogens.

    更新日期:2017-10-13
  • Electrochemical glycoprotein aptasensors based on the in-situ aggregation of silver nanoparticles induced by 4-mercaptophenylboronic acid
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-30
    Ning Xia, Cheng Cheng, Lin Liu, Peizhen Peng, Chaoyang Liu, Junxue Chen

    The authors report on an amperometric method for the determination of glycoprotein by using an aptamer as the bioreceptor. The detection scheme is making use of aggregated citrate-capped silver nanoparticles (AgNPs) on a gold electrode. Aggregation is accomplished by addition of 4-mercaptophenylboronic acid (MPBA) which acts as a cross-linker due to the formation of Ag-S bonds and of boronate esters. A thiolated DNA aptamer was then attached to the electrode in order to capture glycoprotein. Once captured, the glycoprotein reacts with MPBA through the formation of boronate esters. The electrochemical signal is thus amplified by the formation of a network of AgNPs which act as redox reporters. To demonstrate the feasibility of the method, prostate specific antigen (PSA) was chosen as a model analyte. The detection limit for PSA is as low as 0.2 pg mL−1. In our preception, this method provides a powerful tool for studying the glycan function in biological and physiological processes.

    更新日期:2017-10-13
  • A nanocomposite containing Prussian Blue, platinum nanoparticles and polyaniline for multi-amplification of the signal of voltammetric immunosensors: highly sensitive detection of carcinoma antigen 125
    Microchim. Acta (IF 4.58) Pub Date : 2017-08-24
    Yun Zheng, Huiqiang Wang, Zhanfang Ma

    The authors describe a method for signal amplification of label-free voltammetric immunosensors. A glassy carbon electrode (GCE) was modified with Prussian Blue-platinum nanoparticles (PB-PtNPs) as a redox-active species that gives a strong amperometric signal at 0.18 V (vs. Ag/AgCl). Benefitting from the excellent electrical conductivity and the strong catalytic activity to H2O2, the modified GCE gives a strongly enhanced signal. The PB-PtNPs were incorporated into a polyaniline (PANI) hydrogel to further enhance the signal. The signal response of the PB-PtNP-PANI/GCE is larger by a factor of 7.6 than that of PB-PtNP/GCE. In order to further improve electrical conductivity and immobilize antibody, gold nanoparticles (AuNPs) were deposited on the surface of the PB-PtNP-PANI hydrogel. The AuNP-PB-PtNP-PANI hydrogel nanocomposite on the GCE was used in an immunosensor for the model analyte carcinoma antigen 125 (CA125), a biomarker for epithelial ovarian cancer, by immobilizing the respective antibody on the modified GCE. A linear response found for the 0.01 to 5000 U mL−1 CA125 concentration range, with a detection limit of 4.4 mU mL−1 (at an S/N ratio of 3). The electrochemical sensitivity is as high as 119.76 μA·(U/mL)−1·cm−2. The detection of CA125 in human serum showed satisfactory accuracy compared to a commercial chemiluminescent microparticle immunoassay (CMIA).

    更新日期:2017-10-13
  • The effect of pore size in an ultrasensitive DNA sandwich-hybridization assay for the Escherichia coli O157:H7 gene based on the use of a nanoporous alumina membrane
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-10
    Weiwei Ye, Tian Chen, Yijie Mao, Feng Tian, Peilong Sun, Mo Yang

    The authors describe a rapid method for the detection of the Escherichia coli O157:H7 (E. coli O157:H7) bacterial gene. The DNA sandwich-hybridization impedimetric assay is based on the use of a nanoporous alumina membrane in combination with gold/silver core/shell nanoparticles (Ag@AuNPs) that act as tags for impedance signal amplification. The probe oligonucleotides were immobilized on the walls of the nanopores. This is followed by hybridization, first with target (analyte), then with reporter oligonucleotides labeled with Ag@AuNP tags. The impedimetric signal results from target oligo hybridization with probe oligos and co-hybridization with labeled reporter oligos, which increases the blocking degree of the nanopores. The assays were tested with membranes in nanopore sizes of 20 nm, 50 nm and 100 nm. The assay performs best in case of 100 nm nanopores where the limit of detection is as low as 11 pM, with a linear detection range that extends from 50 pM to 200 nM. This indicates its potential for rapid and ultrasensitive gene detection.

    更新日期:2017-10-10
  • Ternary heterojunctions composed of BiOCl, BiVO 4 and nitrogen-doped carbon quantum dots for use in photoelectrochemical sensing: effective charge separation and application to ultrasensitive sensing of dopamine
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-07
    Henan Li, Mingyue Zhu, Wei Chen, Kun Wang

    The use of ternary heterojunctions can lead to superior performance in photoelectrochemical (PEC) sensing. This can be ascribed to effective separation and reduced recombination probability of photogenerated electron-hole pairs. The authors describe the rational design of ternary heterojunctions comoposed of BiOCl, BiVO4 and nitrogen-doped carbon quantum dots (N-CDs). They exhibit enhanced photocurrent compared to the use of BiOCl/BiVO4, BiOCl, or BiVO4. The new material was used in a sensor platform for detection of the neurotransmitter dopamine (DA). Under zero voltage and visible light excitation, DA can be detected in the 1 pM to 10 μM concentration range, with a 0.3 pM lower detection limit (at an S/N ratio of 3). The sensor has rapid response and was applied to the determination of DA in spiked serum samples. Notably, this work also may assist in a better understanding of the relationship between kind of ternary heterojunctions and PEC performance. Conceivably, it can be extended to other PEC sensor platform and other photocatalytic system associated with photoactive materials.

    更新日期:2017-10-08
  • A dextran mediated multicolor immunochromatographic rapid test strip for visual and instrumental simultaneous detection of Vibrio cholera O1 (Ogawa) and Clostridium botulinum toxin A
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-07
    Morteza Gharaat, Reza H. Sajedi, Maryam Shanehsaz, Nezam Jalilian, Manouchehr Mirshahi, Mehrdad Gholamzad

    The authors describe a multicolor immunochromatographic test strip format for simultaneous detection of Vibrio cholera O1 (Ogawa) and of the Clostridium botulinum toxin type A. Respective monoclonal antibodies were conjugated to CdTe quantum dots (QDs) with green and orange emission color. Activated dextran is used as a cross-linker. The CD labeled antibodies were then covered with denatured reduced BSA (dBSA-QD). Under illumination, the test gives lines with emission peaks at 540 nm and 570 nm, respectively. This lateral flow assay system can detect V. cholerae down to 1000 cfu·mL−1 levels, and C. botulinum toxin down to 0.8 ng·mL−1. The method allows assays to performed within 10 min without any sample pretreatment.

    更新日期:2017-10-08
  • Gold decorated polystyrene particles for lateral flow immunodetection of Escherichia coli O157:H7
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-05
    Seon-Ah Jin, Yoojung Heo, Li-Kai Lin, Amanda J. Deering, George T. -C. Chiu, Jan P. Allebach, Lia A. Stanciu

    Microstructure of gold-decorated polystyrene (Au-PS) particles and a schematic illustration for the detection of Escherichia coli O157:H7 by a lateral flow immunoassay strip containing the same.

    更新日期:2017-10-05
  • Colorimetric detection of DNA by using target catalyzed DNA nanostructure assembly and unmodified gold nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-05
    Yan Zeng, Dun Zhang, Peng Qi, Laibao Zheng

    The authors describe a strategy for colorimetric detection of DNA. It is making use of a target catalyzed DNA nanostructure assembly and gold nanoparticles. The assay comprises the following steps: (a) A programmed DNA nanostructure is assembled from three auxiliary hairpin structure DNAs and the single stranded DNA (ssDNA; the target/analyte); (b) in the presence of target DNA, these three hairpin DNAs are opened, thereby activating a catalytic self-assembly process via a target assisted toe-hold strand displacement reaction; (c) The formed DNA nanostructures are mixed with gold nanoparticles. As the DNA nanostructure is less stabilized without ssDNA sticky ends, it cannot prevent the gold nanoparticles (AuNPs) to undergo salt-induced aggregation which is accompanied by a color change from purple to blue; (d) The color change of the colloid solution can be read out with bare eyes or instrumentally. The detection limit by using UV–vis spectrometry is 0.6 pM of target DNA. This is comparable to previously AuNP-based methods. Thus, this assay provides free modification detection based on DNA nanostructure without sophisticated procedures. Conceivably, the method can be applied to numerous other DNA targets.

    更新日期:2017-10-05
  • Amperometric sensing of hydroquinone using a glassy carbon electrode modified with a composite consisting of graphene and molybdenum disulfide
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-05
    Huayu Huang, Jiangyi Zhang, Meimei Cheng, Kunping Liu, Xingyu Wang

    Well-dispersed composites of graphene and molybdenum disulfide were synthesized without using a mediator. The composites were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical properties of a glassy carbon electrode (GCE) modified with the graphene/MoS2 composite were investigated by electrochemical impedance spectroscopy and cyclic voltammetry. Hydroquinone was selected as a model target to show the sensing capability of the modified GCE. The GCE, best operated at a working voltage of 0.10 V (vs. Ag/AgCl), exhibits excellent catalytic activity towards hydroquinone, with a linear response in the 0.5 to 300 μM concentration range and a 37 nM detection limit (at an S/N ratio of 3). The superior performance of the GCE is attributed to the synergistic effects of graphene and MoS2.

    更新日期:2017-10-05
  • A screen printed carbon electrode modified with an amino-functionalized metal organic framework of type MIL-101(Cr) and with palladium nanoparticles for voltammetric sensing of nitrite
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-05
    A. T. Ezhil Vilian, Bose Dinesh, Rethinasabapathy Muruganantham, Sang Rak Choe, Sung-Min Kang, Yun Suk Huh, Young-Kyu Han

    The authors describe an electrochemical sensor for nitrite that is based on the use of a screen printed carbon electrode modified with palladium nanoparticles and an amino-functionalized metal-organic framework. The morphology and properties of the resulting material were examined by X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry, FTIR spectroscopy and transmission electron microscopy. Nitrite was chosen as a model analyte to evaluate the electron transfer performance of the modified SPCE. Its preparation conditions were optimized. The response to nitrite was studied via cyclic voltammetry, linear sweep voltammetry, and square wave voltammetry. Under the optimal conditions, the oxidation current (typically measured at −0.86 V vs Ag/AgCl) increases linearly in the 5 to 150 nM nitrite concentration range, and the detection limit is 1.3 nM. The sensor was applied to the detection of nitrite in (spiked) sausage and pickle samples. It is highly selective to nitrite in the presence of high concentrations of other electro-active compounds, stable, and well reproducible. In our perception, the sensor presented here reveals the large potential of MOF-based hybrid materials for use as an electrode material.

    更新日期:2017-10-05
  • Colorimetric immunoassay for rapid detection of Vibrio parahaemolyticus
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-03
    Yushen Liu, Chao Zhao, Xiuling Song, Kun Xu, Juan Wang, Juan Li

    Vibrio parahaemolyticus (V. parahaemolyticus) is one of the most common food-borne pathogens. The authors describe a rapid colorimetric assay for V. parahaemolyticus that is based on a combination of a magnetic bead-based sandwich immunoassay and signal amplification via an enzmye mimic. MnO2 nanoparticles are used as an artificial oxidase that oxidizes 3,3′,5,5′-tetramethylbenzidine in the presence of oxygen to form a blue (and readily visible) product with an absorption maximum at 652 nm. By combining the superior capture efficiency of magnetic beads with the high catalytic activity of the enzmye mimic, this method can detect V. parahaemolyticus concentration in the range between 10 to 105 cfu·mL−1 without pre-enrichment, and the limit of detection is as low as 10 cfu·mL−1. Recoveries ranging from 87.5% to 106.0% are found when analyzing spiked oyster samples. The assay is rapid, sensitive, and specific and specific. In our perception, it shows promise in rapid instrumental and on-site visual detection of V. parahaemolyticus.

    更新日期:2017-10-03
  • Preparation of boron-doped carbon dots for fluorometric determination of Pb(II), Cu(II) and pyrophosphate ions
    Microchim. Acta (IF 4.58) Pub Date : 2017-10-02
    Zhong-Xia Wang, Xian-He Yu, Feng Li, Fen-Ying Kong, Wei-Xin Lv, Da-He Fan, Wei Wang

    The authors report on the synthesis of boron-doped carbon nanodots (B-C-dots) by a hydrothermal method using ascorbic acid and boric acid as the precursors. The dots have an irregular shape with a typical diameter of 10 nm and display strong fluorescence, with excitation/emission maxima of 350/440 nm. Fluorescence is quenched by Cu(II) and Pb(II) ions due to the formation of nonfluorescent metal complexes between chelating oxygen atoms on the surface of the dots. The findings were used to design a fluorometric method for the determination of the two ions. Linear relationships exist between the drop in fluorescence intensity and the concentrations of Cu(II) and Pb(II) ions in the range from 50 nM to 300 μM and from 25 nM to 250 μM, respectively. The fluorescence of the Cu(II)-quenched B-C-dots is restored in addition of pyrophosphate (PPi) as a result of coordination/chelation interactions between these ions and PPi. This was exploited to develop an assay for PPi that works in the of 25 to 500 μM PPi concentration range.

    更新日期:2017-10-02
  • 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
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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