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  • Truncated aptamers for total and glycated hemoglobin, and their integration into a graphene oxide-based fluorometric method for high-throughput screening for diabetes
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-19
    Abrar Yousef Almusharraf, Shimaa Eissa, Mohammed Zourob

    The authors describe the identification of an effective binding region of aptamers against glycated (HbA1c) and total haemoglobin (tHb) by using a fluorometric assay. Truncation of the originally selected aptamers from 60 to 46 and 34 nucleotides for HbA1c and tHb, respectively, enhances the affinity for their targets. Moreover, shortening the aptamer sequences leads to a better conformational change after target binding which enabled the integration of the aptamers in a graphene oxide (GO)-based fluorometric assay. First, fluorescein-labelled truncated aptamers were physically absorbed onto the surface of GO surface via π−stacking interaction. This leads to quenching of fluorescence. Once the truncated aptamers bind the target protein, a conformational change is induced which results (a) )in the release of the aptamers from the surface of GO and (b) in the restoration of green fluorescence that is measured at 515 nm. The assay can be carried out in a microtiter plate format in homogeneous solution, this avoiding the steps of immobilization, incubation, and washing that are often necessary in immunoassays. This also reduces the time and the costs of the overall assay and allows for high throughput screening for diabetes. HbA1c can be detected in the range from 5.4 to 10.6%. The assay is selective for HbA1c over other proteins that commonly exist in blood. The results obtained by using this method compare well with those of a turbidimetric immunoassay that is typically applied in clinical laboratories.

    更新日期:2018-04-19
  • Study of carbon nanotube-rich impedimetric recognition electrode for ultra-low determination of polycyclic aromatic hydrocarbons in water
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-14
    Jose Muñoz, Cristina Navarro-Senent, Nuria Crivillers, Marta Mas-Torrent

    Carbon nanotubes (CNTs) have been studied as an electrochemical recognition element for the impedimetric determination of priority polycyclic aromatic hydrocarbons (PAHs) in water, using hexocyanoferrate as a redox probe. For this goal, an indium tin oxide (ITO) electrode functionalized with a silane-based self-assembled monolayer carrying CNTs has been engineered. The electroanalytical method, which is similar to an antibody-antigen assay, is straightforward and exploits the high CNT–PAH affinity obtained via π–interactions. After optimizing the experimental conditions, the resulting CNT-based impedimetric recognition platform exhibits ultra-low detection limits (1.75 ± 0.04 ng·L−1) for the sum of PAHs tested, which was also validated by using a certified reference PAH mixture.

    更新日期:2018-04-14
  • Fluorometric aptamer based assay for ochratoxin A based on the use of exonuclease III
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-14
    Renjie Liu, Hua Wu, Lei Lv, Xiaojiao Kang, Chengbi Cui, Jin Feng, Zhijun Guo

    This study describes an aptamer based assay for the mycotoxin ochratoxin A (OTA). The method is based on the use of an OTA-specific aptamer, exonuclease (Exo) III, SYBR Gold as a fluorescent probe, and a complementary strand that specifically combines with the aptamer. In the presence of OTA, the aptamer and OTA hybridize, thereby resulting in the formation of ssDNA, which is not digested by Exo III. Intense fluorescence is observed after addition of SYBR Gold (best measured at excitation/emission wavelengths of 495/540 nm). Fluorescence increases linearly with the log of the OTA concentration in the range from 8 to 1000 ng·mL−1. The detection limit is 4.7 ng·mL−1. The assay was applied to the determination of OTA in diluted [2%(v/v)] red wine, and recoveries and RSDs ranged between 93.5% and 113.8%, and between 3.2% and 5.7%, respectively.

    更新日期:2018-04-14
  • Aptamer based label free thrombin assay based on the use of silver nanoparticles incorporated into self-polymerized dopamine
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-13
    Qingjun Xu, Guixiang Wang, Mingming Zhang, Guiyun Xu, Jiehua Lin, Xiliang Luo

    The authors describe an electrochemical aptasensor for thrombin that is based on the use of a glassy carbon electrode (GCE) modified with polydopamine that is loaded with silver nanoparticles (PDA/AgNPs). The use of AgNPs improves the conductivity of the film and increases the surface area of the GCE. PDA was deposited on the GCE via self-polymerization, and the thrombin binding aptamer was grafted onto the PDA-modified GCE by a single step reaction. Residual electrode surface was blocked with 6-mercapto-1-hexanol. On exposure to thrombin, the electrochemical impedance of the modified electrode increases gradually. Response is linear in the 0.1 pM to 5.0 nM thrombin concentration range, and the limit of detection is as low as 36 fM. The method is selective and capable of detecting thrombin in diluted human serum. In our perception, such a GCE modified with AgNP in a PDA matrix may be applied to many other analytes for which appropriate aptamers are available.

    更新日期:2018-04-13
  • Microwave-assisted synthesis of carbon dots for "turn-on" fluorometric determination of Hg(II) via aggregation-induced emission
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-13
    Yuan Xu, Huiyu Li, Bo Wang, Haochi Liu, Li Zhao, Tianyu Zhou, Meitong Liu, Ning Huang, Yi Li, Lan Ding, Yanhua Chen

    A fluorescent probe is presented for sensitive determination of Hg(II). It is based on aggregation induced enhancement effect (AIEE) of carbon dots co-doped with nitrogen and sulfur (N,S-CDs). The N,S-CDs were prepared by a one-pot microwave-assisted method using glycerol as the reaction solvent, and cystine as the source for C, N and S. The resulting CDs are well soluble in water and have a turn-on fluorescence response to Hg(II). The incubation time and ratio of raw materials were optimized. Fluorescence, best measured at excitation/emission wavelengths of 325/385 nm, increases linearly in the 1–75 μM Hg(II) concentration range, and the detection limit is 0.5 μM. The method performed successfully when detecting Hg(II) in spiked tap and lake waters, with recoveries between 92 and 106%.

    更新日期:2018-04-13
  • Amperometric determination of ascorbic acid with a glassy carbon electrode modified with TiO 2 -gold nanoparticles integrated into carbon nanotubes
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-12
    Jessica Scremin, Eduardo César Melo Barbosa, Carlos Alberto Rossi Salamanca-Neto, Pedro Henrique Cury Camargo, Elen Romão Sartori

    A glassy carbon electrode was modified with a TiO2-gold nanoparticle hybrid integrated with multi-walled carbon nanotubes in a dihexadecylphosphate film (TiO2-Au NP-MWCNT-DHP/GCE) and applied to amperometric determination of ascorbic acid (AA). The modified sensor displays fast charge transfer and shows an irreversible anodic behavior for AA by cyclic voltammetry. Under optimal experimental conditions and using amperometry at 0.4 V, the analytical curve presented a statistical linear concentration range for AA from 5.0 to 51 μmol L−1, with a limit of detection of 1.2 μmol L−1. The electrode was successfully applied to the determination of AA in pharmaceutical and fruit juice without the need for major pretreatment of samples.

    更新日期:2018-04-12
  • Nonenzymatic determination of glucose at near neutral pH values based on the use of nafion and platinum black coated microneedle electrode array
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-07
    Somasekhar R. Chinnadayyala, Ilhwan Park, Sungbo Cho

    The authors report on a microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose. It consists of 3 × 5 sharp stainless steel microneedles micromachined from a stainless steel substrate. The microneedles are 600 and 100 μm in height and width, respectively. Nafion and platinum black were sequentially coated onto the tip of gold-coated microneedles and used for nonenzymatic (direct) sensing of glucose. Attractive features of the modified microneedle electrode include (a) a low working potential (+0.12 V vs. Ag/AgCl), (b) a linear response in the physiologically relevant range (1–40 mM), (c) a sensitivity as high as 175 μA mM−1 cm−2, (d) a 23 μM detection limit, and (e) a response time of 2 s. The sensor also exhibits good reproducibility and stability. The sensor is selective for glucose even in the presence of 10-fold higher concentrations of ascorbic acid, lactic acid, dopamine, uric acid, and acetaminophen.

    更新日期:2018-04-08
  • Poly(3,4-ethylenedioxythiophene) doped with engineered carbon quantum dots for enhanced amperometric detection of nitrite
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-06
    Mingxia Jiao, Zimeng Li, Yun Li, Min Cui, Xiliang Luo

    An electrochemical sensor for nitrite was fabricated by modifying a glassy carbon electrode (GCE) with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that is doped with carbon quantum dots (CQDs). The negatively charged CQDs were doped into PEDOT via electrodeposition to form a conducting polymer nanocomposite on the GCE. The electrode surface has a flake-like nanostructure and a large specific surface area. The elemental mapping analysis revealed that the CQDs are uniformly distributed across the whole nanocomposite. As a result of the superior catalytic activity of CQDs and the good conductivity of PEDOT, the modified GCE displays excellent electrocatalytic activity towards the oxidation of nitrite, and the oxidation peak current is ten times higher than that of a PEDOT modified GCE without CQDs. Under optimum conditions and at a working voltage of 0.80 V (vs. Ag/AgCl), the sensor has a linear response in the 0.5–1110 μM nitrite concentration range, and an 88 nM limit of detection (at S/N = 3). Three different electrodes prepared under the same experimental conditions were applied for the detection of nitrite, and the RSD was 3.1%. The same sensor was employed to quantify nitrite in three replicate measurements, and the RSD was 2.2%.

    更新日期:2018-04-07
  • 3D hollow porous CdFe 2 O 4 microspheres as viable materials for magnetic solid-phase extraction of azo colorants
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-05
    Danfeng Zhang, Lei Zhang, Tong Liu

    3D magnetic hollow porous CdFe2O4 microspheres (3D MHPS-CdFe2O4) were prepared by a one-step and template-free hydrothermal method. The material was applied for magnetic solid phase extraction of three azo colorants (Acid Red, Congo Red, Sunset Yellow). Compared to conventional CdFe2O4 nanoparticles, the new 3D material exhibits superior extraction capability because of its unique hollow porous structure, high specific surface area, and the strong interaction between 3D microspheres and the colorants. A magnetic solid phase extraction (MPSE) combined with HPLC was established for simultaneous detection of the three azo colorants in food samples. Under optimum conditions, the detection limits are 0.54–1.00 ng mL-1, and good recoveries of 87.0–100.7% were obtained with spiked samples, with relative standard deviation of ≤ 3.8%. The combination of using the new 3D material and MPSE-HPLC results in an efficient, sensitive and inexpensive method for simultaneous determination of such colorants.

    更新日期:2018-04-05
  • Molecularly imprinted polymers for the detection of illegal drugs and additives: a review
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-04
    Deli Xiao, Yue Jiang, Yanping Bi

    This review (with 154 refs.) describes the current status of using molecularly imprinted polymers in the extraction and quantitation of illicit drugs and additives. The review starts with an introduction into some synthesis methods (lump MIPs, spherical MIPs, surface imprinting) of MIPs using illicit drugs and additives as templates. The next section covers applications, with subsections on the detection of illegal additives in food, of doping in sports, and of illicit addictive drugs. A particular focus is directed towards current limitations and challenges, on the optimization of methods for preparation of MIPs, their applicability to aqueous samples, the leakage of template molecules, and the identification of the best balance between adsorption capacity and selectivity factor. At last, the need for convincing characterization methods, the lack of uniform parameters for defining selectivity, and the merits and demerits of MIPs prepared using nanomaterials are addressed. Strategies are suggested to solve existing problems, and future developments are discussed with respect to a more widespread use in relevant fields.

    更新日期:2018-04-04
  • Amperometric determination of L-cysteine using a glassy carbon electrode modified with palladium nanoparticles grown on reduced graphene oxide in a Nafion matrix
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-03
    Norazriena Yusoff, Perumal Rameshkumar, An’amt Mohamed Noor, Nay Ming Huang

    An amperometric sensor for L-Cys is described which consists of a glassy carbon electrode (GCE) that was modified with reduced graphene oxide placed in a Nafion film and decorated with palladium nanoparticles (PdNPs). The film was synthesized by a hydrothermal method. The PdNPs have an average diameter of about 10 nm and a spherical shape. The modified GCE gives a linear electro-oxidative response to L-Cys (typically at +0.6 V vs. SCE) within the 0.5 to 10 μM concentration range. Other figures of merit include a response time of less than 2 s, a 0.15 μM lower detection limit (at signal to noise ratio of 3), and an analytical sensitivity of 1.30 μA·μM−1·cm−2. The sensor displays selectivity over ascorbic acid, uric acid, dopamine, hydrogen peroxide, urea, and glucose. The modified GCE was applied to the determination of L-Cys in human urine samples and gave excellent recoveries.

    更新日期:2018-04-03
  • Silver microspheres coated with a molecularly imprinted polymer as a SERS substrate for sensitive detection of bisphenol A
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-02
    Xiaohui Ren, Emily C. Cheshari, Jingyao Qi, Xin Li

    An efficient approach is demonstrated for preparing particles consisting of a silver core and a shell of molecularly imprinted polymer (Ag@MIP). The MIP is prepared by using bisphenol A (BPA) as the template and 4-vinylpyridine as the functional monomer. The Ag@MIP fulfills a dual function in that the silver core acts as a SERS substrate, while the MIP allows for selective recognition of BPA. The Ag@MIP is characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis and Raman spectroscopy. The Raman intensity of Ag@MIP is higher than that of bare silver microspheres. The detection limit for BPA is as low as 10−9 mol·L−1.

    更新日期:2018-04-02
  • MnO nanoparticles with unique excitation-dependent fluorescence for multicolor cellular imaging and MR imaging of brain glioma
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-02
    Junxin Lai, Tingjian Wang, Hao Wang, Fengqiang Shi, Wei Gu, Ling Ye

    The authors describe MnO nanoparticles (NPs) with unique excitation-dependent fluorescence across the entire visible spectrum. These NPs are shown to be efficient optical nanoprobe for multicolor cellular imaging. Synthesis of the NPs is accomplished by a thermal decomposition method. The MnO NPs exhibit a high r1 relaxivity of 4.68 mM−1 s−1 and therefore give an enhanced contrast effect in magnetic resonance (MR) studies of brain glioma. The cytotoxicity assay, hemolysis analysis, and hematoxylin and eosin (H&E) staining tests verify that the MnO NPs are biocompatible. In the authors’ perception, the simultaneous attributes of multicolor fluorescence and excellent MR functionality make this material a promising dual-modal nanoprobe for use in bio-imaging.

    更新日期:2018-04-02
  • A multifunctional probe based on the use of labeled aptamer and magnetic nanoparticles for fluorometric determination of adenosine 5’-triphosphate
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-02
    Xiaojie Liu, Bixia Lin, Ying Yu, Yujuan Cao, Manli Guo

    A multifunctional fluorescent probe is synthesized for the determination of adenosine 5′-triphosphate (ATP). The 6-carboxyfluorescein-labeled aptamer (FAM-aptamer) was bound to the surface of magnetite nanoparticles coated with polydopamine (Fe3O4@PDA) by π-π stacking interaction to form the multifunctional probe. The probe has three functions including recognition, magnetic separation, and yielding a fluorescent signal. In the presence of ATP, FAM-aptamer on the surface of the probe binds to ATP and returns to the solution. Thus, the fluorescence of the supernatant is enhanced and can be related to the concentration of ATP. Fluorescence intensities were measured at excitation/emission wavelengths of 494/526 nm. Response is linear in the 0.1–100 μM ATP concentration range, and the detection limit is 89 nM. The probe was applied to the quantitation of ATP in spiked human urine and serum samples, with recoveries ranging between 94.8 and 102%.

    更新日期:2018-04-02
  • A nanoporous palladium(II) bridged coordination polymer acting as a peroxidase mimic in a method for visual detection of glucose in tear and saliva
    Microchim. Acta (IF 4.58) Pub Date : 2018-04-02
    Vinita, Narsingh R. Nirala, Madhu Tiwari, Rajiv Prakash

    A nanoporous coordination polymer (NPCP) was prepared from palladium(II) chloride and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole and is shown to act as a peroxidase mimetic. It can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 which is formed on enzymatic oxidation of glucose by glucose oxidase. Based on these findings, a sensitive glucose test was worked out at 652 nm where the intensity if the greenish-blue product is related to the actual concentration of glucose. Figures of merit include (a) rather low Km value (30 μM) which evidences the strong binding affinity of the NPCP toward glucose, (b) a high v(max) (8.5 M·s−1), (c) a 47 nM detection limit, (d) a lifetime of a month, (e) a wide working pH range (2–10), and (f) a 25–80 °C temperature range. The assay was applied to non-invasive determination of glucose assay in tear, saliva where the detection limits are found to be 61 and 91 nM, respectively.

    更新日期:2018-04-02
  • Expression of Concern: Magnetic mesoporous polymelamine-formaldehyde resin as an adsorbent for endocrine disrupting chemicals
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-27
    Otto S. Wolfbeis

    Abstract The Editor-in-Chief is issuing an editorial expression of concern regarding the article Microchim Acta (2018) 185: 19.

    更新日期:2018-03-27
  • MoS 2 quantum dots modified with a labeled molecular beacon as a ratiometric fluorescent gene probe for FRET based detection and imaging of microRNA
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-27
    Xinsheng Yu, Lianzhe Hu, Feng Zhang, Min Wang, Zhining Xia, Weili Wei

    A dual-channel ratiometric nanoprobe is described for detection and imaging of microRNA. It was prepared from MoS2 quantum dots (QDs; with blue emission and excitation/emission peaks at 310/398 nm) which acts as both the gene carrier and as a donor in fluorescence resonance energy transfer (FRET). Molecular beacons containing loops for molecular recognition of microRNA and labeled with carboxyfluorescein (FAM) were covalently attached to the MoS2 QDs and serve as the FRET acceptor. In the absence of microRNA, the nanoprobe exhibits low FRET efficiency due to the close distance between the FAM tag and the QDs. Hybridization with microRNA enlarges the distance between QD and beacon. This results in an enhancement of the FRET efficiency of the nanoprobe. The ratio of green and blue fluorescence (I520/I398) increases linearly in the 5 to 150 nM microRNA concentration range in both aqueous solution and diluted artificial cerebrospinal fluid. The limit of detection (LOD) is as low as 0.38 nM and 0.52 nM, respectively. Other features of this nanoprobe include (a) excellent resistance to nuclease-induced false positive signals and (b) the option to use it for distinguishing different cell lines by in-situ imaging of intracellular microRNAs.

    更新日期:2018-03-27
  • The mechanism of the adsorption of dsDNA on citrate-stabilized gold nanoparticles and a colorimetric and visual method for detecting the V600E point mutation of the BRAF gene
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-27
    Zhen Liu, Menik Hettihewa, Yang Shu, Chunqiong Zhou, Qian Wan, Lihong Liu

    A study is presented on the binding kinetics and mechanism of the adsorption of dsDNA on citrate-capped gold nanoparticles (AuNPs). Methods include fluorescence titration, isothermal calorimetry (ITC) titration, dynamic light scattering and gel electrophoresis. It is found that the fluorescence of probe DNA (labeled with Rhodamine Green and measured at excitation/emission peaks of 498/531 nm) is quenched by addition of AuNPs. The Stern-Volmer quenching constant (Ksv) is 1.67 × 10^9 L·mol−1 at 308 K and drops with increasing temperature. The quenching mechanism is mainly static. The results of both fluorescence titrations and ITC show negative values for ΔH and ΔS values. This shows ion-induced dipole-dipole interaction to be the main attractive forces between dsDNA and AuNPs, while electrostatic interactions result in repulsion. The repulsive forces lead to a lower affinity between dsDNA and AuNPs (compared to single-strand DNA). It is also found that dsDNA can prevent the aggregation of AuNPs which is accompanied by a color change from red into blue. The visual detection limit with bare eyes for dsDNA1 is 36 pM. Based on these findings, a colorimetric method was developed to detect the proto-oncogene of serine/threonine-protein kinase B-Raf V600E point mutation in HT29, Ec109, A549, Huh-7 and SW480 cell lines.

    更新日期:2018-03-27
  • Nanosized aptameric cavities imprinted on the surface of magnetic nanoparticles for high-throughput protein recognition
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-27
    Elham Shoghi, Seyede Zohreh Mirahmadi-Zare, Razieh Ghasemi, Matine Asghari, Mansour Poorebrahim, Mohammad-Hossein Nasr-Esfahani

    The authors introduce a new kind of surface artificial biomimetic receptor, referred to as aptameric imprinted polymer (AIP), for separation of biological macromolecules. Highly dispersed magnetic nanoparticles (MNPs) were coated with silica and then functionalized with methacrylate groups via silane chemistry. The aptamer was covalently immobilized on the surface of nanoparticles via a “thiol-ene” click reaction. Once the target analyte (bovine serum albumin; BSA) has bound to the aptamer, a polymer is created by 2-dimensional copolymerization of short-length poly(ethylene glycol) and (3-aminopropyl)triethoxysilane. Following removal of BSA from the polymer, the AIP-MNPs presented here can selectively capture BSA with a specific absorbance (κ) as high as 65. When using this AIP, the recovery of BSA from spiked real biological samples is >97%, and the adsorption capacity is as high as 146 mg g−1. In our perception, this method has a wide scope in that it may be applied to the specific extraction of numerous other biomolecules.

    更新日期:2018-03-27
  • Three kinds of lateral flow immunochromatographic assays based on the use of nanoparticle labels for fluorometric determination of zearalenone
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-24
    Shi-jie Li, Wei Sheng, Wenjun Wen, Ying Gu, Jun-ping Wang, Shuo Wang

    Colloidal gold, quantum dots and polystyrene microspheres were used as labels in three kinds of lateral flow immunochromatographic assays (ICAs) for the detection of zearalenone (ZEN) in cereal samples. The assays allow ZEN to be quantified within 20 min. The LODs are 10 μg·L−1 of ZEN for the colloidal gold-based ICA, and 1 μg·L−1 for both the quantum dot and polystyrene microsphere based ICAs. The respective data are 60 μg·kg−1, 6 μg·kg−1 and 6 μg·kg−1, respectively, for spiked samples and cereals. Only minor cross-sensitivity occurred between ZEN and fusarium toxins, and no cross-sensitivity if found for aflatoxin B1, T-2 mycotoxin, ochratoxin A, deoxynivalenol, and fumonisin B1. LODs of the three assays are lower than the maximum limits of ZEN set by most standardization agencies.

    更新日期:2018-03-24
  • Synthesis of Er(III)/Yb(III)-doped BiF 3 upconversion nanoparticles for use in optical thermometry
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-23
    Peng Du, Jae Su Yu

    The authors describe an ethylene glycol assisted precipitation method for synthesis of Er(III)/Yb(III)-doped BiF3 nanoparticles (NPs) at room temperature. Under 980-nm light irradiation, the NPs emit upconversion (UC) emission of Er(III) ions as a result of a two-photon absorption process. The temperature-dependent green emissions (peaking at 525 and 545 nm) are used to establish an unambiguous relationship between the ratio of fluorescence intensities and temperature. The NPs have a maximum sensitivity of 6.5 × 10−3 K−1 at 619 K and can be applied over the 291–691 K temperature range. The results indicate that these NPs are a promising candidate for optical thermometry.

    更新日期:2018-03-23
  • Colorimetric detection of Hg(II) by measurement the color alterations from the “before” and “after” RGB images of etched triangular silver nanoplates
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-22
    Li Li, Laiping Zhang, Yan Zhao, Zhengbo Chen

    It is shown that triangular silver nanoplates (TAgNPs) are viable colorimetric probes for the fast, sensitive and selective detection of Hg(II). Detection is accomplished by reducing Hg(II) ions to elemental Hg so that an Ag/Hg amalgam is formed on the surface of the TAgNPs. This leads to the inhibition of the etching TAgNPs by chloride ions. Correspondingly, a distinct color transition can be observed that goes from yellow to brown, purple, and blue. The color alterations extracted from the red, green, and blue part of digital (RGB) images can be applied to the determination of Hg(II). The relationship between the Euclidean distances (EDs), i.e. the square roots of the sums of the squares of the ΔRGB values, vary in the 5 nM to 100 nM Hg(II) concentration range, and the limit of detection is as low as 0.35 nM. The color changes also allow for a visual estimation of the concentrations of Hg(II). The method is simple in that it only requires a digital camera for data acquisition and a Photoshop software for extracting RGB variations and data processing.

    更新日期:2018-03-22
  • Dual approach for the colorimetric determination of unamplified microRNAs by using citrate capped gold nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-22
    Ahmed Ibrahim Nossier, Hana Abdelzaher, Marwa Matboli, Sanaa Eissa

    The authors describe a method for the colorimetric determination of unamplified microRNA. It is based on the use of citrate-capped gold nanoparticles (AuNPs) and, alternatively, a microRNA-probe hybrid or a magnetically extracted microRNA that serve as stabilizers against the salt-induced aggregation of AuNPs. The absorbance ratios A525/A625 of the reacted AuNP solutions were used to quantify the amount of microRNA. The assay works in the range of 5–25 pmol microRNA. The lower limit of detection (LOD) is 10 pmol. The performance of the method was tested by detection of microRNA-210-3p in totally extracted urinary microRNA from normal, benign, and bladder cancer subjects. The sensitivity and specificity for qualitative detection of urinary microRNA-210-3p using the assay are 74% and 88% respectively, which is consistent with real time PCR based assays. The assay was applied to the determination of specific microRNA by using its specific oligo targeter or following magnetic isolation of the desired microRNA. The method is simple, cost-efficient, has a short turn-around time and requires minimal equipment and personnel.

    更新日期:2018-03-22
  • Fluorometric determination of dopamine by using molybdenum disulfide quantum dots
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-20
    Xinnan Liu, Wentao Zhang, Lunjie Huang, Na Hu, Wei Liu, Yingnan Liu, Sihang Li, Chengyuan Yang, Yourui Suo, Jianlong Wang

    A method is described for the rapid fluorometric determination of dopamine (DA) by using molybdenum disulfide quantum dots (MoS2 QDs) that were fabricated via an ammonium hydroxide etching method. The probe has a fluorescence (with excitation/emission peaks at 267/380 nm) that is quenched by DA with high selectivity over various interferences. This is attributed to a reaction that occurs between DA and the molybdate ions in pH 9 solutions of MoS2 QDs. The formation of organic molybdate complexes and of dopamine-quinone results in strong quenching of the fluorescence of the QDs which is due to both electron transfer and an inner filter effect. Under the optimum conditions, the assay works in the 0.1–100 μM DA concentration range, with two linear ranges and a 10 nM detection limit. The method was applied to the determination of DA in spiked artificial urine samples, where it gave recoveries ranging from 97.6 to 102.2%, demonstrating that the method a promising tool for rapid and selective detection of DA.

    更新日期:2018-03-20
  • Polydopamine nanodots are viable probes for fluorometric determination of the activity of alkaline phosphatase via the in situ regulation of a redox reaction triggered by the enzyme
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Qin Xue, Xuanyu Cao, Cuiling Zhang, Yuezhong Xian

    The authors describe an environmentally friendly and fast (~14 min) method for the synthesis of homogeneously distributed fluorescent polydopamine nanodots (PDA-NDs) using KMnO4 as the oxidant. Alkaline phosphatase (ALP) catalyzes the hydrolysis of ascorbic acid 2-phosphate to release free ascorbic acid which undergoes an in-situ redox reaction with KMnO4. Depending on the activity of ALP, more or less KMnO4 is consumed, and this affects the formation of the PDA-NDs. Based on this finding, a sensitive method was worked out to quantify the activity of ALP via real-time formation of fluorescent PDA-NDs. The fluorometric signal (best measured at excitation/emission peaks of 390/500 nm) is linear in the 1 to 50 mU·mL−1 ALP activity range, and the limit of the detection is as low as 0.94 mU·mL−1 (based on 3 σ/m). The method was successfully applied to the determination of ALP activity in spiked human serum and in MCF-7 cell lysates. It was also applied in a method to screen for inhibitors of ALP.

    更新日期:2018-03-19
  • Zwitterion-functionalized polymer microspheres as a sorbent for solid phase extraction of trace levels of V(V), Cr(III), As(III), Sn(IV), Sb(III) and Hg(II) prior to their determination by ICP-MS
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Xiaoyu Jia, Dirong Gong, Junyi Zhao, Hongyun Ren, Jiani Wang, Xian Zhang

    This paper describes the preparation of zwitterion-functionalized polymer microspheres (ZPMs) and their application to simultaneous enrichment of V(V), Cr(III), As(III), Sn(IV), Sb(III) and Hg(II) from environmental water samples. The ZPMs were prepared by emulsion copolymerization of ethyl methacrylate, 2-diethylaminoethyl methacrylate and triethylene glycol dimethyl acrylate followed by modification with 1,3-propanesultone. The components were analyzed by elemental analyses as well as Fourier transform infrared spectroscopy, and the structures were characterized by scanning electron microscopy and transmission electron microscopy. The ZPMs were packed into a mini-column for on-line solid-phase extraction (SPE) of the above metal ions. Following extraction with 40 mM NH4NO3 and 0.5 M HNO3 solution, the ions were quantified by ICP-MS. Under the optimized conditions, the enrichment factors (from a 40 mL sample) are up to 60 for the ions V(V), As(III), Sb(III) and Hg(II), and 55 for Cr(III) and Sn(IV). The detection limits are 1.2, 3.4, 1.0, 3.7, 2.1 and 1.6 ng L−1 for V(V), Cr(III), As(III), Sn(IV), Sb(III) and Hg(II), respectively, and the relative standard deviations (RSDs) are below 5.2%. The feasibility and accuracy of the method were validated by successfully analyzing six certified reference materials as well as lake, well and river waters.

    更新日期:2018-03-19
  • Porous Ni 3 N nanosheet array as a catalyst for nonenzymatic amperometric determination of glucose
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Junjun Luo, Dan Zhao, Minghui Yang, Fengli Qu

    A glassy carbon electrode was modified with an array of porous Ni3N nanosheets (Ni3N NA) and studied for its use in non-enzymatic electrochemical detection of glucose. The morphology and structure of the Ni3N NA were characterized by scanning electron microscopy and X-ray diffraction. Electrochemical studies demonstrated that the Ni3N NA acts as an efficient catalyst for the electro-oxidation of glucose at pH 13, best at a working voltage of 0.55 V (vs. Ag/AgCl). Figures of merit include (a) high sensitivity (39 μA·mM−1·cm−2), (b) a low limit of detection (0.48 μM), and (c) a linear range that extends from 2 μM to 7.5 mM. The sensor was applied to the determination of glucose levels in human serum, and satisfactory results were obtained.

    更新日期:2018-03-19
  • Water-soluble MoS 2 quantum dots are a viable fluorescent probe for hypochlorite
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Yi Wang, Pu Zhang, Qing Lu, Yue Wang, Wensheng Fu, Qin Tan, Weiping Luo

    A method is described for the fluorometric determination of hypochlorite. It is making use of molybdenum disulfide quantum dots (MoS2 QDs) as a fluorescent probe. The QDs are prepared by hydrothermal reaction of sodium molybdate with glutathione. They possess diameters typically ranging from 1.4 to 3.8 nm, excellent stability in water, and blue photoluminescence (with excitation/emission peaks located at 315/412 nm and a quantum yield of 3.7%). The fluorescence of the QDs is statically quenched by hypochlorite, and the Stern-Volmer plot is linear. Hypochlorite can be detected in the 5–500 μM concentration range with a 0.5 μM detection limit. The method has been successfully applied to the determination of hypochlorite in spiked samples of tap water, lake water, and commercial disinfectants.

    更新日期:2018-03-19
  • Enantiomeric separation of adrenaline, noradrenaline, and isoprenaline by capillary electrophoresis using streptomycin-modified gold nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Chunye Liu, Jingshu Zhang, Xuejiao Zhang, Lingzhi Zhao, Shuang Li

    Enantiomeric separations of the adrenergic compounds adrenaline, noradrenaline, and isoprenaline were studied. Electromigrative separations were performed in uncoated fused silica capillaries using streptomycin-modified gold nanoparticles (ST-AuNPs) as an additive to the background electrolyte. The ST-AuNPs are shown to serve as an effective chiral selector. The modified AuNPs were characterized in terms of size and zeta potential, and by IR and UV-vis spectra. The effects of ST-AuNP concentration, pH value, temperature, and separation voltage on the separations were systematically studied. Under optimized experimental conditions, racemic mixtures of the respective adrenergic drugs were baseline-separated within 7 min with a resolution of up to 7.5. The relative standard deviations of the resolution in inter-day and intra-day studies (n = 5) were generally <5%.

    更新日期:2018-03-19
  • Voltammetric chiral discrimination of tryptophan using a multilayer nanocomposite with implemented amino-modified β-cyclodextrin as recognition element
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-19
    Jinyi Song, Chengcheng Yang, Jiao Ma, Qian Han, Peiyao Ran, Yingzi Fu

    An electrochemical chiral multilayer nanocomposite was prepared by modifying a glassy carbon electrode (GCE) via opposite-charge adsorption of amino-modified β-cyclodextrin (NH2-β-CD), gold-platinum core-shell microspheres (Au@Pts), polyethyleneimine (PEI), and multi-walled carbon nanotubes (MWCNTs). The modified GCE was applied to the enantioselective voltammetric determination of tryprophan (Trp). The Au@Pts enable an effective immobilization of the chiral selector (NH2-β-CD) and enhance the electrochemical performance. Scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, FTIR and electrochemical methods were used to characterize the nanocomposite. Trp enantiomers were then determined by differential pulse voltammetry (DPV) (with a peak potential of +0.7 V vs. Ag/AgCl). The recognition efficiency was expressed by an increase in peak height by about 32% for DPV determinations of L-Trp compared to D-Trp in case of a 5 mM Trp solution of pH 7.0. Response was linear in the 10 μM to 5.0 mM concentration range, and the limits of detection were 4.3 μM and 5.6 μM with electrochemical sensitivity of 43.5 μA·μM−1·cm−2 and 34.6 μA·μM−1·cm−2 for L-Trp and D-Trp, respectively (at S/N = 3).

    更新日期:2018-03-19
  • Solid-phase microextraction of sulfonylurea herbicides by using borate-reinforced multiple monolithic fibers
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-16
    Xiaojia Huang, Xiangyu Zhu, Miao Pei

    Boron-nitrogen coordination is a useful interaction for use in the extraction of amino-nitrogen-containing compounds. A new monolithic adsorbent is described here that consisted of poly(acrylamidophenyl boronic acid/vinyl-3-octylimidazolium tetrafluroborate-co-divinylbenzene/ethylene dimethacrylate) polymer. It was synthesized with the aim to obtain a new kind of extraction phase for multiple monolith based fiber solid-phase microextraction of sulfonylurea herbicides. Results indicate that boron-nitrogen coordination interaction plays a key role in the efficient extraction. It is also found that soaking the sorbent in a borate solution further improves the enrichment performance. The preparation conditions and extraction parameters were optimized. Following extraction with the adsorbent, the sulfonylurea herbicides were submitted to quantitation by HPLC with DAD detection. The limits of detection are in the range of 9.0–18 ng·L−1. The method was applied to monitor the herbicides in samples of tap, river and waste waters. Recoveries at spiking levels of 1.0, 10 and 100 μg·L−1 are in the range of 70.1–108%, and the values for relative standard deviation are less than 10% for all analytes in all cases.

    更新日期:2018-03-16
  • Determination of protein kinase A activity and inhibition by using hydroxyapatite nanoparticles as a fluorescent probe
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-16
    Kaina Zhang, Ke Zeng, Congcong Shen, Shiyu Tian, Minghui Yang

    The authors describe a fluorometric method for the determination of the activity and inhibition of protein kinase A (PKA). In the presence of ATP, PKA catalyzes the transfer of phosphate groups from ATP to a peptide, and the generated phosphorylated peptide quenches the fluorescence (measured at excitation/emission peaks of 340/440 nm) of the hydroxyapatite nanoparticles (HAP-NPs). A linear logarithmic relationship of PKA concentrations with fluorescence intensity in the range from 1 to 50 U·L−1 was obtained, and the lower limit of detection (LOD) is 0.5 U·L−1. This is much lower than LODs reported in the literature. The PKA inhibitor H-89 was studied, and the inhibition plot has a sigmoidal shape with a half-maximal inhibitory concentration of around 750 nM of H-89. At a 4.5 nM level of H-89, fluorescence of HAP-NPs fell to levels of no PKA controls, demonstrating that the assay is a viable tool to screen for kinase inhibitors. An assay with Hela cell lysates in combination with forskolin (an activator of adenylyl cyclase) and IBMX (a phosphodiesterase inhibitor used to activate the cellular activity of PKA) resulted in decreased fluorescence of HAP-NPs. This suggests that the assay can be applied for testing in vitro cell kinase activity. In our perception, this method will enable high-throughput screening for kinase-related drugs and fluorometric enzymatic detection in various areas.

    更新日期:2018-03-16
  • Quick colorimetric determination of choline in milk and serum based on the use of MoS 2 nanosheets as a highly active enzyme mimetic
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-16
    Narsingh R. Nirala, Vinita, Rajiv Prakash

    The authors have synthesized molybdenum disulfide nanosheets (MoS2 nanosheets) by using a bottom-up hydrothermal method. The nanosheets display strong catalytic (enzyme mimetic) activity in catalyzing the oxidation of peroxidase substrate of 3,3′,5,5′-tetramethylbenzidine (TMB) in presence of H2O2 to produce a blue product. The peroxidase mimicking properties of MoS2 nanosheets depend on temperature, H2O2 concentration and pH value. A choline assay was worked out where choline was oxidized by choline oxidase in presence of oxygen to produce H2O2 which is colorimetrically detected, best at 652 nm. The method works in the 1 to 180 μM choline concentration range with a 0.4 μM detection limit. Color changes may also be detected visually. The assay is simple, highly sensitive, selective and rapid. It was applied in the determination of choline in (spiked) milk and serum.

    更新日期:2018-03-16
  • Hollow carbon dots labeled with FITC or TRITC for use in fluorescent cellular imaging
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-14
    Menghuan Tang, Ping Teng, Yijuan Long, Xiliang Wang, Liping Liang, Dongjun Shen, Jie Wang, Huzhi Zheng

    Hollow carbon dots (HCDs) were prepared by a solvothermal method and conjugated to either tetramethyl rhodamine isothiocyanate (TRITC) or fluorescein-5-isothiocyanate (FITC). This resulted in HCDs with bright red or green fluorescence, with excitation/emission peaks at 550/580 and 491/520 nm, respectively. The nanocomposites are well water-soluble, remarkably photostable and biocompatible. In addition, the fluorescence of the composites is more stable in a reactive oxygen environment than the free dyes. Confocal images indicate that the nanoparticles quickly enter A549 cells and mainly accumulate in the cytoplasm. The wavelength of functionalized HCDs can be regulating via coupling the HCDs to different dyes. These results demonstrate that these composite materials can be very promising reagents for biological labeling and imaging.

    更新日期:2018-03-14
  • A two-wavelength fluorescence recovery method for the simultaneous determination of aureomycin and oxytetracycline by using gold nanocrystals modified with serine and 11-mercaptoundecanoic acid
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-14
    Yaning Mao, Yufeng Wu, Yongyin Nie, Jun Wang, Yuanyuan Liu, Shenghao Xu, Xiliang Luo

    A method is described for rapid (1 h) synthesis of gold nanoclusters (AuNCs) co-functionalized with serine and 11-mercaptoundecanoic acid. The co-functionalized AuNCs exhibit good stability towards temperature, pH values, and over time. They were characterized by atomic force microscopy, high-resolution transmission electron microscopy, dynamic light scattering, and by fluorescence, IR and X-ray photoelectron spectroscopies. The fluorescence of the AuNCs is quenched by Hg(II) and restored on subsequent addition of aureomycin (CTC) or oxytetracycline (OTC). A fluorescent turn-on assay was worked out for simultaneous detection of CTC and OTC based on recording the change of the restored fluorescence measured at 420 and 500 nm under 340 nm photoexcitation. The detection limits are 20 and 9 nM for CTC and OTC, respectively. The concentrations of CTC and OTC can also be visualized by UV illumination. The nanoprobe was successfully applied to the simultaneous determination of CTC and OTC in spiked human urine.

    更新日期:2018-03-14
  • Improving the sensitivity of immunoassays by reducing non-specific binding of poly(acrylic acid) coated upconverting nanoparticles by adding free poly(acrylic acid)
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-13
    Satu Lahtinen, Annika Lyytikäinen, Nina Sirkka, Henna Päkkilä, Tero Soukka

    Upconverting nanoparticles (UCNPs) are attractive reporters in immunoassays because of their outstanding detectability. However, non-specific binding of antibody-UCNP conjugates on protein coated solid support results in background, which limits the immunoassay sensitivity. Thus, the full potential of UCNPs as reporters cannot be fully exploited. The authors report here a method to improve the sensitivity of UCNP-based immunoassays by reducing the non-specific binding of antibody-UNCP conjugates on the protein coated solid support. In the assays studied here, poly(acrylic acid) (PAA) coated NaYF4:Yb3+,Er3+ type UCNPs were conjugated to two different antibodies against cardiac troponin I (cTnI) and thyroid stimulating hormone (TSH). The two-step heterogeneous sandwich immunoassays were performed in microtitration wells, and the green luminescence of antibody-UCNP conjugates was measured at 540 nm upon 980 nm excitation. Non-specific binding of antibody-UCNP conjugates was reduced by mixing free PAA with PAA coated UCNPs before adding the UCNPs to the wells. The free PAA in the buffer reduced the background in both cTnI and TSH immunoassays (compared to the control assay without free PAA). The limits of detection decreased from 2.1 ng·L−1 to 0.48 ng·L−1 in case of cTnI and from 0.070 mIU·L−1 to 0.020 mIU·L−1 in case of TSH if PAA is added to the buffer. Presumably, the effect of free PAA is due to blocking of the surface areas where PAA coated UCNP would bind proteins non-specifically. The method introduced here is likely to be applicable to other kinds of PAA-coated nanoparticles, and similar approaches conceivably work also with other nanoparticle coatings.

    更新日期:2018-03-13
  • Voltammetric determination of 5-hydroxytryptamine based on the use of platinum nanoparticles coated with molecularly imprinted silica
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-13
    Yiwen Yang, Yanbo Zeng, Chuangui Tang, Xudong Zhu, Xing Lu, Lingyu Liu, Zhidong Chen, Lei Li

    The authors describe an electrochemical sensor for the determination of 5-hydroxytryptamine (5-HT; serotonin). It is based on the use of platinum nanoparticles (PtNPs) coated with molecularly imprinted silica (MIS). The MIS-coated PtNPs were prepared from 5-HT, PtNPs, phenyltrimethoxysilane and tetraethoxysilane that act as template, support, functional monomer and cross-linker, respectively. The MIS-coated PtNPs were characterized by Fourier transfer infrared spectroscopy and transmission electron microscopy. The MIS-coated PtNPs were drop-cast onto a glassy carbon electrode (GCE) to obtain an electrochemical sensor for 5-HT which exhibited fast response and high recognition ability for 5-HT. The imprinting factor of this electrode for 5-HT is 4.12, which is higher than that for its analogs. Under optimized conditions and at a typical working potential of 0.29 V (vs. Hg/Hg2Cl2), the electrode has a linear response in the 0.05–80 μM 5-HT concentration range and a 0.02 μM detection limit. The electrode was successfully applied to the determination of 5-HT in human serum samples.

    更新日期:2018-03-13
  • Gold nanorods for in-drop colorimetric determination of thiomersal after photochemical decomposition
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-13
    Manuel Martín-Alonso, Francisco Pena-Pereira, Isela Lavilla, Carlos Bendicho

    This work reports on the implementation of gold nanorods (AuNRs) in headspace solvent microextraction for colorimetric determination of volatile analyte derivatives in a single drop. The exposure of AuNRs to both H2Se and elemental mercury (Hg0) results in a shift of the longitudinal plasmonic band, unlike a number of volatiles. Accordingly, a method is reported for the determination of Hg0 with potential applicability to the determination of thiomersal (sodium ethylmercurithiosalicylate). It is based on the photochemical decomposition of thiomersal into Hg(II) and subsequent exposure of AuNRs-containing microdrop to in situ generated Hg0. Colorimetric analysis of the enriched drop was carried out without dilution by means of a cuvetteless microvolume UV-vis spectrometer. Under optimal conditions, the limit of detection was 0.5 ng mL−1 (as Hg). The repeatability, expressed as relative standard deviation, was 8.4% (for n = 10). AuNRs exposed to increasing concentrations of the analyte were characterized by means of transmission electron microscopy and UV-vis spectrophotometry to ascertain the mechanism of detection. The method was finally applied to the determination of thiomersal in various pharmaceutical samples and showed quantitative recoveries.

    更新日期:2018-03-13
  • Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-12
    Mahmoud Roushani, Faezeh Shahdost-fard

    The authors describe a highly sensitive method for the aptamer (Apt) based impedimetric determination of cocaine. The surface of a screen-printed electrode (SPE) was modified with a nanocomposite of dendrimer and silver nanoparticles (AgNPs). The cocaine-binding Apt was attached to a dendrimer/AgNP/SPE surface, forming a sensitive layer for the determination of cocaine. The incubation with the analyte resulted in the formation of a cocaine/Apt complex on the electrode surface. As a consequence, folding and conformational change in the aptamer structure was induced, this resulting in a change in the impedimetric signal. The aptaassay exhibits highly efficient sensing characteristics with a good linearity of 1 fmol L−1 to 100 nmol L−1 (with two linear ranges) and a limit of detection (LOD) of 333 amol L−1. Its excellent specificity and high sensitivity suggest that this kind of aptamer-based assay may be applied to detect other targets in this field.

    更新日期:2018-03-12
  • A colorimetric gold nanoparticle aggregation assay for malathion based on target-induced hairpin structure assembly of complementary strands of aptamer
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-12
    Khalil Abnous, Noor Mohammad Danesh, Mohammad Ramezani, Mona Alibolandi, Ahmad Sarreshtehdar Emrani, Parirokh Lavaee, Seyed Mohammad Taghdisi

    The authors describe a method for the colorimetric determination of the pesticide malathion. It is based on the use of a hairpin structure consisting of a complementary strand of aptamer and a double-stranded DNA (dsDNA) structure to protect gold nanoparticles (AuNPs) against salt-induced aggregation. In the absence of malathion, the dsDNA structure is preserved on the surface of AuNPs and the color of the AuNPs in solutions containing NaCl remains red. However, in the presence of malathion, a hairpin structure of complementary strand is formed. The Aptamer/Malathion complex and the complementary strand are released from the surface of the AuNPs. As a result, the AuNPs undergo salt-induced aggregation which is accompanied by a color change to blue. The assay allows malathion to be quantified within 35 min (A650/A520 was measured). The detection limit is 1 pM, and response is linear in the 5 pM to 10 nM malathion concentration range. The method is specific and was successfully applied to the determination of malathion in spiked human serum samples.

    更新日期:2018-03-12
  • A ratiometric upconversion nanoprobe for fluorometric turn-on detection of sulfite and bisulfite
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-12
    Shuailiang Wang, Xiaozheng Cao, Tang Gao, Xiaobo Wang, Hui Zou, Wenbin Zeng

    A nanoprobe is described for the ratiometric fluorometric determination of sulfite ions. Upconversion nanoparticles (UCNPs) of the type β-NaYF4:Yb(III),Er(III),Tm(III) were covalently modified with the molecular probe HIAN which is a hydroxynaphthalimide fluorophore modified with a (cationic) indolinium moiety. Under excitation at 980 nm, the green emission of the UCNPs (peaking at 543 nm) is almost totally quenched, while the NIR emission (peaking at 802 nm) remains unaffected. In the presence of sulfite or bisulfite (hydrogen sulfite), the green fluorescence is restored and can be visually observed. A ratiometric method was worked out by measurement of the ratio of the green and NIR emissions. The analytical range extends from 10 to 250 μM, the limit of detection is 0.14 μM, and the assay can be performed within 40 s.

    更新日期:2018-03-12
  • A glassy carbon electrode modified with cerium phosphate nanotubes for the simultaneous determination of hydroquinone, catechol and resorcinol
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-12
    Zhen Li, Yuhua Yue, Yanjun Hao, Shun Feng, Xianli Zhou

    A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM−1 cm−2. The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC.

    更新日期:2018-03-12
  • Voltammetric determination of the Escherichia coli DNA using a screen-printed carbon electrode modified with polyaniline and gold nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-12
    Nahid Shoaie, Mehdi Forouzandeh, Kobra Omidfar

    The authors describe an electrochemical assay for fast detection of Escherichia coli (E. coli). It is based on a dual signal amplification strategy and the use of a screen-printed carbon electrode (SPCE) whose surface was modified with a polyaniline (PANI) film and gold nanoparticles (AuNPs) via cyclic voltammetry (CV). In the next step, avidin was covalently immobilized on the PANI/AuNP composite on the SPCE surface. Subsequently, the biotinylated DNA capture probe was immobilized onto the PANI/AuNP/avidin-modified SPCE by biotin-avidin interaction. Then, DNA of E.coli, digoxigenin-labeled DNA detector probe and anti-digoxigenin-labeled horseradish peroxidase (HRP) were placed on the electrode. 3,3′,5,5′-Tetramethylbenzidine (TMB) and H2O2 solution were added and the CV electrochemical signal was generated at a potential of −0.1 V (vs. Ag/AgCl) and a scan rate 50 mV.s−1. The assay can detect 4 × 106 to 4 CFU of E. coli without DNA amplification. The biosensor is highly specific over other pathogens including Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, Staphylococcus haemolyticus and Pseudomonas aeruginosa. It can be concluded that this genosensor has an excellent potential for rapid and accurate diagnosis of E.coli inflicted infections.

    更新日期:2018-03-12
  • A review on chemiresistive room temperature gas sensors based on metal oxide nanostructures, graphene and 2D transition metal dichalcogenides
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-10
    Nirav Joshi, Takeshi Hayasaka, Yumeng Liu, Huiliang Liu, Osvaldo N. Oliveira, Liwei Lin

    Room-temperature (RT) gas sensing is desirable for battery-powered or self-powered instrumentation that can monitor emissions associated with pollution and industrial processes. This review (with 171 references) discusses recent advances in three types of porous nanostructures that have shown remarkable potential for RT gas sensing. The first group comprises hierarchical oxide nanostructures (mainly oxides of Sn, Ni, Zn, W, In, La, Fe, Co). The second group comprises graphene and its derivatives (graphene, graphene oxides, reduced graphene oxides, and their composites with metal oxides and noble metals). The third group comprises 2D transition metal dichalcogenides (mainly sulfides of Mo, W, Sn, Ni, also in combination with metal oxides). They all have been found to enable RT sensing of gases such as NOx, NH3, H2, SO2, CO, and of vapors such as of acetone, formaldehyde or methanol. Attractive features also include high selectivity and sensitivity, long-term stability and affordable costs. Strengths and limitations of these materials are highlighted, and prospects with respect to the development of new materials to overcome existing limitations are discussed.

    更新日期:2018-03-10
  • An “off-on” colorimetric and fluorometric assay for Cu(II) based on the use of NaYF 4 :Yb(III),Er(III) upconversion nanoparticles functionalized with branched polyethylenimine
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-07
    Hong Shao, Dan Xu, Yadan Ding, Xia Hong, Yichun Liu

    The authors describe an “off-on” colorimetric and fluorometric assay for the determination of Cu(II). It is based on the use of upconversion nanoparticles (UCNPs) of type NaYF4:Yb(III),Er(III) that were functionalized with branched polyethylenimine (BPEI). A color change from colorless to blue occurs within 2 s after addition of Cu(II) to a solution of the modified UCNPs. The color change can be visually detected at Cu(II) concentrations down to 80 μM. The upconversion fluorescence of the modified UCNPs, measured at excitation wavelength of 980 nm, is reduced due to the predominant inner filter effect caused by the formation of the BPEI-Cu(II) complex. Normalized fluorescence intensity drops linearly in the 50 nM to 10 μM Cu(II) concentration range, and the fluorometric detection limit is 45 nM. Both the color and the fluorescence are recovered on addition of EDTA. Excellent selectivity over other metal ions and anions is achieved.

    更新日期:2018-03-07
  • Gold nanoparticle-based colorimetric ELISA for quantification of ractopamine
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-07
    Shuaijuan Han, Tianjiao Zhou, Bingjie Yin, Pingli He

    The work describes a gold nanoparticle-based colorimetric enzyme-linked immunosorbent assay (ELISA) for ractopamine. The ELISA is based on an indirect competitive approach. In the presence of ractopamine, gold(III) ions are oxidized by H2O2 to form red AuNPs. On the other hand, the AuNP in solution are purple-blue due to aggregation if the sample does not contain ractopamine. The absorption, best measured at 560 nm, increases linearly in the 2 to 512 ng·mL−1 ractopamine concentration range, and the detection limit is as low as 0.35 ng·mL−1 in urine. Ractopamine can also be detected visually, even in the presence of other β-agonists and antibiotics. The results obtained by this method are consistent with those obtained by LC-MS/MS as demonstrated by analysis of sheep urine. The ELISA method described here is inexpensive, easy-to-use, and suitable for rapid screening of ractopamine in animal samples.

    更新日期:2018-03-07
  • Detection of nucleic acids and elimination of carryover contamination by using loop-mediated isothermal amplification and antarctic thermal sensitive uracil-DNA-glycosylase in a lateral flow biosensor: application to the detection of Streptococcus pneumoniae
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-07
    Yi Wang, Yan Wang, Dongxun Li, Jianguo Xu, Changyun Ye

    The authors report on a loop-mediated isothermal amplification (LAMP) scheme that uses antarctic thermally sensitive uracil-DNA-glycosylase (AUDG) for simultaneous detection of nucleic acids and elimination of carryover contamination. It was applied in a lateral flow assay (LFA) format. The assay has attractive features in that it does not require the use of labeled primers or probes, and can eliminate false-positive results generated by unwanted hybridization between two labeled primers or between a labeled primer and probe. LAMP amplification and AUDG digestion are conducted in a single pot, and the application of a closed-tube reaction prevents false-positives due to carryover contamination. The method was applied to the detection of the human pathogen Streptococcus pneumoniaein in pure cultures and spiked blood samples. This LFA can detect S. pneumoniae in pure cultures with a 25 fg.μL−1 detection limit and in spiked blood samples with a 470 cfu.mL−1 detection limit. Conceivably, this assay can be applied to the detection of various other targets if the specific LAMP primers are available.

    更新日期:2018-03-07
  • A voltammetric immunosensor for clenbuterol based on the use of a MoS 2 -AuPt nanocomposite
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-06
    Renyue Ji, Shuai Chen, Wei Xu, Zhen Qin, Jing Fu Qiu, Chao Rui Li

    An ultrasensitive immunosensor for the direct detection of the illegally used livestock feed clebuterol (CLB) is described. It is based on the use of a glassy carbon electrode modified with an MoS2-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS2-AuPt accelerates electron transfer, and this leads to a sharp increase in the electrochemical signal for the electrochemical probe hydrogen peroxide. Differential pulse voltammetry was used to record the current signal at a peak potential of −0.18 V (vs SCE). Under optimal conditions, the electrode has a linear response in the 10 pg·mL−1 to 100 ng·mL−1 CLB concentration range and a 6.9 pg·mL−1 detection limit (based on the 3σ criterium). This immunosensor is sensitive, highly specific and acceptably reproducible, and thus represents a valuable tool for the determination of CLB in pork.

    更新日期:2018-03-06
  • Magnetic nanoparticles coated with a molecularly imprinted polymer doped with manganese-doped ZnS quantum dots for the determination of 2,4,6-trichlorophenol
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-05
    Xiao Wei, Miaomiao Yu, Chen Li, Xinghui Gong, Fang Qin, Zhenhong Wang

    The authors describe a multifunctional magnetic molecularly imprinted phosphorescent nanoparticle probe for the selective determination of 2,4,6-trichlorophenol (2,4,6-TCP). The probe consists of a magnetite (Fe3O4) core that is coated with a molecularly imprinted polymer doped with Mn-doped ZnS quantum dots (QDs). The MIP was obtained by copolymerization of acrylamide, ethylene glycol dimethacrylate, and 2,4,6-TCP. The resulting nanoprobe shows strong phosphorescence (with excitation/emission peaks at 320/594 nm) due to the presence of the QDs, good magnetism, and high selectivity for 2,4,6-TCP. Under optimal detection condition, response is linear in the 0.1–30 μmol L−1 2,4,6-TCP concentration range. The imprinting factor is 8.84, and the detection limit is 35 nmol L−1. The method was successfully applied to the determination of 2,4,6-TCP in spiked river water and waste water.

    更新日期:2018-03-06
  • A fluorescent DNA based probe for Hg(II) based on thymine-Hg(II)-thymine interaction and enrichment via magnetized graphene oxide
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-03
    Meng-Ke Li, Liu-Yin Hu, Cheng-Gang Niu, Da-Wei Huang, Guang-Ming Zeng

    The authors describe a fluorometric assay for the determination of Hg(II). A naphthalimide derivative is used as a label for a thymine (T) rich ssDNA, and graphene oxide magnetized with Fe3O4 nanoparticles acts as a quencher and preconcentrators. In the absence of Hg(II), the labeled ssDNA does not separate from the magnetized graphene oxide. As a result, fluorescence is fully quenched. In the presence of Hg(II), a T-Hg(II)-T link is formed dues to the highly affinity between T and Hg(II). Hence, fluorescence is restored. The assay has a linear response in the 1.0 to 10.0 nM Hg(II) concentration range, and a 0.65 nM detection limit. The method is selective and sensitive. It was applied to the analysis of spiked environmental water samples, and data agreed well with those obtained by atomic fluorescence spectrometry.

    更新日期:2018-03-06
  • Determination of vanillin by using gold nanoparticle-modified screen-printed carbon electrode modified with graphene quantum dots and Nafion
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-03
    Gema M. Durán, Eulogio J. Llorent-Martínez, Ana M. Contento, Ángel Ríos

    A voltammetric analytical assay for the selective quantification of vanillin is described. It is based on the use of a gold nanoparticle-modified screen-printed carbon electrode (SPCE) modified with graphene quantum dots (GQD) in a Nafion matrix. The GQD were synthesized by an acidic thermal method and characterized by UV-Vis, photoluminescence, and FTIR spectroscopy. The modified SPCE displays a strongly enhanced response to vanillin. Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) were applied to optimize the methods. The analytical assay has linear responses in the 13 to 660 μM and 0.66 to 33 μM vanillin concentration ranges. The detection limits are 3.9 μM and 0.32 μM when using LSV and DPV, respectively. The analytical assay is selective and stable. It was applied to the determination of vanillin in several food samples with satisfactory results. Recoveries from spiked samples ranged between 92.1 and 113.0%.

    更新日期:2018-03-06
  • Folic acid modified copper nanoclusters for fluorescent imaging of cancer cells with over-expressed folate receptor
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-03
    Jun-Mei Xia, Xing Wei, Xu-Wei Chen, Yang Shu, Jian-Hua Wang

    Water-soluble and functional copper nanoclusters (CuNCs) were prepared by using folic acid (FA) that serves both as a reducing reagent and a stabilizer. FA also acts as a functional ligand on the surface of the CuNCs, and this can be exploited to target the folate receptor which is over-expressed on the surface of HeLa cells. The FA-modified CuNCs nanoclusters have an average size of ca. 0.9 nm and are stable in aqueous medium for 30 days. Under photoexcitation at λex 270 and 350 nm, the FA-CuNCs display strong blue fluorescence with an emission peak at 440 nm. The FA-CuNCs exhibit low cytotoxicity and favorable biocompatibility as demonstrated by an MTT assay. A cell viability of >80% is found when incubating HeLa cells for 20 h with FA-CuNCs at levels of up to 200 μg mL−1. The targeting capability of the FA-CuNCs is demonstrated by live cell imaging. It is shown that HeLa cells with over-expressed folate receptor are much brighter than A549 cells where the receptor is not over-expressed. This is further corroborated by the fact that the copper content in HeLa cells (1.5 pg/cell) is 6.5-fold higher than that of A549 cells (0.23 pg/cell), both measured after the same incubation time of 3 h. If free FA is introduced into the cell culture medium, the folate receptors will be preoccupied with FA, and this results in a significant decrease in the cellular uptake of the FA-CuNCs by HeLa cells.

    更新日期:2018-03-06
  • Voltammetric determination of attomolar levels of a sequence derived from the genom of hepatitis B virus by using molecular beacon mediated circular strand displacement and rolling circle amplification
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-03
    Shan Huang, Mengmeng Feng, Jiawen Li, Yi Liu, Qi Xiao

    The authors describe an electrochemical method for the determination of the single-stranded DNA (ssDNA) oligonucleotide with a sequence derived from the genom of hepatitis B virus (HBV). It is making use of circular strand displacement (CSD) and rolling circle amplification (RCA) strategies mediated by a molecular beacon (MB). This ssDNA hybridizes with the loop portion of the MB immobilized on the surface of a gold electrode, while primer DNA also hybridizes with the rest of partial DNA sequences of MB. This triggers the MB-mediated CSD. The RCA is then initiated to produce a long DNA strand with multiple tandem-repeat sequences, and this results in a significant increase of the differential pulse voltammetric response of the electrochemical probe Methylene Blue at a rather low working potential of −0.24 V (vs. Ag/AgCl). Under optimal experimental conditions, the assay displays an ultrahigh sensitivity (with a 2.6 aM detection limit) and excellent selectivity. Response is linear in the 10 to 700 aM DNA concentration range.

    更新日期:2018-03-06
  • A hollow porous molecularly imprinted polymer as a sorbent for the extraction of 7 macrolide antibiotics prior to their determination by HPLC-MS/MS
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-01
    Shunli Ji, Tengfei Li, Wen Yang, Chang Shu, Duo Li, Yan Wang, Li Ding

    A hollow porous molecularly imprinted polymer (HPMIP) is described for use in dispersive solid phase extraction of macrolide antibiotics (MACs). The HPMIP was prepared by using spiramycin as the template, methacrylic acid as the functional monomer, and mesoporous MCM-41 (Mobile Composition of Matter No. 41; with a size of about 100 nm) as a sacrificial support. The sorbent was characterized by Fourier transform infrared spectrometry, transmission electron microscopy, nitrogen adsorption and thermo-gravimetric analysis. Several parameters affecting the extraction efficiency were optimized. The material has a large surface area (359 m2·g−1), and most recognition sites are located on the surface of the HPMIPs. This results in high binding capacity (120 μmol·g−1) and fast binding (20 min) in comparison to either MCM-41-core surface MIPs or solid MIPs. The method was applied to the extraction of the MACs azithromycin, spiramycin, tilmicosin, tylosin, clarithromycin, roxithromycin and josamycin from spiked honey. The recoveries, determined by HPLC-MS/MS, ranged from 88.0% to 117% at the three spiking levels tested (1, 5 and 20 μg·kg−1). Intra-day and inter-day assay precision at three spiking levels are <10.7% (for n = 6) and 12.6% (n = 3), respectively. The limits of detection are between 3 and 17 ng·kg−1. This indicates the superiority of the method in selective extraction of macrolides even from complex matrices.

    更新日期:2018-03-01
  • Ultrasensitive amperometric aptasensor for the epithelial cell adhesion molecule by using target-driven toehold-mediated DNA recycling amplification
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-01
    Qinhua Chen, Wanbao Hu, Bing Shang, Jian Wei, Long Chen, Xiaojun Guo, Fengying Ran, Wei Chen, Xueru Ding, Ying Xu, Yinhua Wu

    An amperometric aptasensor is reported for the electrochemical determination of the epithelial cell adhesion molecule (EpCAM). It is based on a combination of EpCAM-driven toehold-mediated DNA recycling amplification, the specific recognition of EpCAM aptamer, and its binding to EpCAM. Hairpin probe 1 (Hp1) with a toehold region was modified with a 5′-thiol group (5’-SH) and self-assembled onto the surface of a gold electrode. Upon addition of EpCAM, the probe A (a 15-mer) is liberated from the aptamer/probe A complex and then hybridizes with the toehold domain of Hp1. This results in the exposure of another toehold for further hybridizing with hairpin probe 2 (Hp2) to displace probe A in the presence of Hp2 that was labeled with the electrochemical probe Methylene Blue (MB). Subsequently, liberated probe A is hybridized again with another Hp1 to start the next round of DNA recycling amplification by reusing probe A. This leads to the formation of plenty of MB-labeled DNA strands on the electrode surface and generates an amplified current. This 1:N probe-response amplification results in ultrasensitive and specific detection of EpCAM, with a 20 pg·mL−1 detection limit. The electrode is highly stable and regenerable. It was successfully applied to the determination of EpCAM in spiked human serum, urine and saliva, and thus provides a promising tool for early clinical diagnosis.

    更新日期:2018-03-01
  • Ratiometric fluorometric determination of the anthrax biomarker 2,6-dipicolinic acid by using europium(III)-doped carbon dots in a test stripe
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-01
    Mingcong Rong, Xiangzhou Deng, Siting Chi, Longzhen Huang, Youbin Zhou, Yune Shen, Xi Chen

    Europium(III)-doped carbon dots (Eu-CDs) were prepared from citric acid and europium nitrate via a one-pot pyrolytic method. The Eu-CDs emit intense blue fluorescence (with excitation/emission peaks at 365/465 nm), are water soluble and biocompatible. On addition of 2,6-dipicolinic acid (DPA; an anthrax biomarker), ligand-to-ion energy transfer occurs from DPA to Eu(III) which has a red emission peaking at 615 nm. This results in an increase of the intensity of the red fluorescence. DPA can be detected by the ratio of fluorescence intensities at 616 and 475 nm. The method has an analytical range that extends from 5 to 700 nmol·L−1, with a 5 nmol·L−1 detection limit. The Eu-CDs also were incorporated into a test paper for visual detection of DPA with a portable UV lamp and a smartphone. In this case, the detection limit is 1 μmol·L−1. The Eu-CDs internalize well into HeLa cells, and this paves the way to bioimaging.

    更新日期:2018-03-01
  • Nanoparticle assisted laser desorption/ionization mass spectrometry for small molecule analytes
    Microchim. Acta (IF 4.58) Pub Date : 2018-03-01
    Hani Nasser Abdelhamid

    Nanoparticle assisted laser desorption/ionization mass spectrometry (NPs-ALDI-MS) shows remarkable characteristics and has a promising future in terms of real sample analysis. The incorporation of NPs can advance several methods including surface assisted LDI-MS, and surface enhanced LDI-MS. These methods have advanced the detection of many thermally labile and nonvolatile biomolecules. Nanoparticles circumvent the drawbacks of conventional organic matrices for the analysis of small molecules. In most cases, NPs offer a clear background without interfering peaks, absence of fragmentation of thermally labile molecules, and allow the ionization of species with weak noncovalent interactions. Furthermore, an enhancement in sensitivity and selectivity can be achieved. NPs enable straightforward analysis of target species in a complex sample. This review (with 239 refs.) covers the progress made in laser-based mass spectrometry in combination with the use of metallic NPs (such as AuNPs, AgNPs, PtNPs, and PdNPs), NPs consisting of oxides and chalcogenides, silicon-based NPs, carbon-based nanomaterials, quantum dots, and metal-organic frameworks.

    更新日期:2018-03-01
  • Determination of the activity of telomerase in cancer cells by using BSA-protected gold nanoclusters as a fluorescent probe
    Microchim. Acta (IF 4.58) Pub Date : 2018-02-27
    Yujuan Xu, Peng Zhang, Zhen Wang, Shaoping Lv, Caifeng Ding

    Gold nanoclusters (AuNCs) protected with a bovine serum albumin (BSA) coating are known to emit red fluorescence (peaking at 650 nm) on photoexcitation with ultraviolet light (365 nm). On addition of Cu(II) ions, fluorescence is quenched because Cu(II) complexes certain amino acid units in the BSA chain. Fluorescence is, however, restored if pyrophosphate (PPi) is added because it will chelate Cu(II) and remove it from the BSA coating on the AuNCs. Because PPi is involved in the function of telomerase, the BSA@AuNCs loaded with Cu(II) can act as a fluorescent probe for determination of the activity of telomerase. A fluorescent assay was worked out for telomerase that is highly sensitive and has a wide linear range (10 nU to 10 fM per mL). The fluorescent probe was applied to the determination of telomerase activity in cervix carcinoma cells via imaging. It is shown that tumor cells can be well distinguished from normal cells by monitoring the differences in intracellular telomerase activity.

    更新日期:2018-02-27
  • Visual and colorimetric determination of H 2 O 2 and glucose based on citrate-promoted H 2 O 2 sculpturing of silver nanoparticles
    Microchim. Acta (IF 4.58) Pub Date : 2018-02-27
    Chenghua Zong, Bo Li, Jing Wang, Xiaojun Liu, Wenfeng Zhao, Qingquan Zhang, Xinming Nie, Yang Yu

    Isotropic silver nanoparticles (iAg NPs) can be easily prepared at low costs, have a low electrochemical potential and high extinction coefficient. An effective colorimetric assay for H2O2 is reported here based on the finding that H2O2 can induce the shape transformation of citrate-capped iAg NPs with the help of citrate. The substantial shape variation affords an apparent surface plasmon resonance (SPR) shift, accompanied by a vivid color change from light yellow to mauve. The color change can be observed visually if the concentration of H2O2 is 2 μM or higher. A good linear relationship was obtained over the concentration range of 0.2–32 μM with a limit of detection of 90 nM. By making use of glucose oxidase, the method is further extended to glucose detection. Glucose at a concentration as low as 10 μM can be well determined with bare eyes. Benefitting from the high selectivity, the detection of glucose in human serum is realized, and the results are in good agreement with those provided by a clinical analyzer.

    更新日期:2018-02-27
  • Surface enhanced Raman detection of the colon cancer biomarker cytidine by using magnetized nanoparticles of the type Fe 3 O 4 /Au/Ag
    Microchim. Acta (IF 4.58) Pub Date : 2018-02-26
    Yuan Xiang, Hanru Yang, Xiaoyu Guo, Yiping Wu, Ye Ying, Ying Wen, Haifeng Yang

    Cytidine is regarded as an early marker of colon cancer. The authors describe a surface enhanced Raman scattering (SERS) technique to detect trace levels of cytidine in urine. The Raman band at 784 cm−1 can be acquired best. Compared to earlier methods, an improvement in detection sensitivity by a factor of 6.2 × 105 is achieved by using a magnetically induced method in which cytidine is captured in the vicinity of the SERS hot spots of the type Fe3O4/Au/Ag. Cytidine can be quantified at 1 nM levels by this method which is simple and reliable.

    更新日期:2018-02-26
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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