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Mikrochimica Acta

Jianyong Huang, Fenglan Li, Rubin Guo, Yuyuan Chen, Zhenzhen Wang, Chengfei Zhao, Yanjie Zheng, Shaohuang Weng, Xinhua Lin
Amino-modified carbon dots (C-dots) with positively charged surface were prepared. They display strong blue fluorescence and are shown to act as quenchers of the green fluorescence of FAM-labeled ssDNA such as the F-probe used in this work that was immobilized on the C-dots. On the addition of highly negatively charged heparin (Hep), it will interact with the C-dots and displace the F-probe from C-dots. Once the F-probe is displaced by Hep, its green fluorescence is restored. The intrinsic blue fluorescence of the C-dots remains stable after addition of Hep...
April 21, 2018: Mikrochimica Acta
Xinhui Yu, Yaohui Lin, Xusheng Wang, Liangjun Xu, Zongwen Wang, FengFu Fu
An exonuclease-assisted multicolor aptasensor was developed for the visual detection of ochratoxin A (OTA). It is based on the etching of gold nanorods (AuNRs) mediated by a G-quadruplex-hemin DNAzyme. A DNA sequence (AG4-OTA) was designed that comprises a hemin aptamer and an OTA aptamer. OTA binds to AG4-OTA to form an antiparallel G-quadruplex, which halts its digestion by exonuclease I (Exo I) from the 3'-end of AG4-OTA. Thus, the retained hemin aptamer can bind to hemin to form a G-quadruplex-hemin DNAzyme...
April 21, 2018: Mikrochimica Acta
Hong Wei, Dawei Pan, Xueping Hu, Ming Liu, Haitao Han, Dazhong Shen
Anodic stripping voltammetric determination of copper ions was accomplished at a glassy carbon disk electrode modified with core-shell microspheres of the gold@manganese dioxide (Au@MnO2 ) type. These were synthesized via electrochemical deposition. The gold nanoparticles (AuNPs) were electrochemically deposited and employed as an active support material for the growth of MnO2 to yield Au@MnO2 core-shell particles with unique and regular spherical morphology. The microspheres have a diameter of 200-250 nm and scrolled edges like a cactus...
April 21, 2018: Mikrochimica Acta
Minghui Wang, Huanshun Yin, Yunlei Zhou, Jingrui Han, Tingqun He, Lin Cui, Shiyun Ai
A photoelectrochemical biosensor is described for sensitive detection of microRNA-162a. A multiple amplification strategy is employed that involves (a) isothermal strand displacement polymerase reaction; (b) terminal deoxynucleotidyl transferase-mediated extension, (c) amplification of streptavidin-coated gold nanoparticles, and (d) biotin functionalized alkaline phosphatase. Graphite-like C3 N4 (g-C3 N4 ) nanosheets were used as photoactive material. By using these amplification strategies, the detection limit is as low as 0...
April 20, 2018: Mikrochimica Acta
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...
April 19, 2018: Mikrochimica Acta
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)...
April 14, 2018: Mikrochimica Acta
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...
April 14, 2018: Mikrochimica Acta
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...
April 13, 2018: Mikrochimica Acta
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...
April 13, 2018: Mikrochimica Acta
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...
April 12, 2018: Mikrochimica Acta
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...
April 7, 2018: Mikrochimica Acta
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...
April 6, 2018: Mikrochimica Acta
Danfeng Zhang, Lei Zhang, Tong Liu
3D magnetic hollow porous CdFe2 O4 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 CdFe2 O4 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...
April 5, 2018: Mikrochimica Acta
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...
April 4, 2018: Mikrochimica Acta
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...
April 3, 2018: Mikrochimica Acta
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...
April 2, 2018: Mikrochimica Acta
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...
April 2, 2018: Mikrochimica Acta
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 H2 O2 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...
April 2, 2018: Mikrochimica Acta
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 (Fe3 O4 @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...
April 2, 2018: Mikrochimica Acta
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...
March 27, 2018: Mikrochimica Acta
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