Elgazzar, ElsayedAttala, KhaledAbdel-Atty, ShimaaAbdel-Raoof, Ahmed M....
9页
查看更多>>摘要：A new chemically disposable screen-printed modified electrode with yttrium doped manganese oxide (Mn2O3/Y2O3) nanocomposite at screen printed electrode was mainly constructed to quantify xylometazoline hydrochloride (XMZ). The crystallographic parameters were estimated from the XRD spectrum, suggesting that Mn2O3 of cubic phase with average grain size similar to 77 nm. The SEM images revealed that Y3+ dopants had improved the surface topology. The findings indicate that morphological features play a vital role in improving the electronic properties of the fabricated electrode. Augmentation of Six Sigma (SS) with molecular dynamics simulation (MD) as a theoretical study was widely adopted to improve the current process as a quality management methodology by measuring the process capability to determine if the process meets the desired specification limits. Process capability is determined through measuring the variability in the process output and comparing these variations with the desired specifications. Also, it assures a robust method specification at a high level of targeted performance and statistical confidence. A greenness assessment procedure utilizing the eco-scale algorism was conducted to prove the greenness of the proposed methodology. Additionally, the proposed sensor presented a high sensitivity over the concentration range (1x10(-6)-1x10(-2) mol L-1) of a detection limit 3.93 x 10(-7) mol L-1 with the Nernstian cationic slope of 58.18 +/- 0.76 mV decade 1 at 25 +/- 1 degrees C.
查看更多>>摘要：Cadmium ion (Cd (II)) is a highly toxic heavy metal usually found in natural water. Exposure to Cd (II) can produce serious effects in human organs such as Itai-Itai disease. Therefore, the maximum allowance levels of Cd (II) in drinking water and herbal medicines imposed by the World Health Organization (WHO) are 3 mu g L-1 and 300 mu g kg(-1), respectively. In this work, nitrogen-doped graphene quantum dots (N-GQDs) as a fluorescent sensor for Cd (II) determination was developed in both solution-based and paper-based systems. N-GQDs were synthesized from citric acid (CA) and ethylenediamine (EDA) via the hydrothermal method. The synthesized NGQDs emitted intense blue fluorescence with a quantum yield (QY) of up to 80%. The functional groups on the surface of N-GQDs measured by FTIR were carboxyl (COO-), hydroxyl (OH-), and amine (NH2) groups, suggesting that they could be bound to Cd (II) for complexation. The fluorescence intensity of N-GQDs was gradually enhanced with the increase of Cd (II) concentration. This phenomenon was proved to result from the fluorescence enhancement (turn-on) based on the chelation enhanced fluorescence (CHEF) mechanism. Under the optimum conditions in the solution-based and paper-based systems, the limits of detection (LODs) were found to be 1.09 and 0.59 mu g L-1, respectively. Furthermore, the developed sensors showed relatively high selectivity toward Cd (II) over ten other metal cations and six other anions of different charges. The performance of the sensor in real water and herbal medicine samples exhibited no significant difference as compared to the results of the validation method (ICP-OES). Therefore, the developed sensors can be used as fluorescent sensors for Cd (II) determination with high sensitivity, high selectivity, short incubation time (5 min). As such, the paper-based strategy has excellent promising potential for practical analysis of Cd (II) in water and herbal medicine samples with a trace level of Cd (II) concentrations.
查看更多>>摘要：Single-cell impedance analysis can provide valuable information for characterizing and discriminating cells. In this paper, a cost-effective portable microfluidic impedance cytometer (MIC) was proposed to realize the broadband impedance analysis of cells by using maximum length sequence (MLS) and viscoelastic focusing. The MIC comprised a microfluidic chip with a straight microchannel, two indium tin oxide (ITO) electrodes, and a home-made platform performing maximum length sequence technique. The viscoelastic focusing enabled cells to focus into a single train to eliminate the influence of cell position variation on acquired electrical signals and allow the cells to pass through the detection region one by one. The MLS technique realized the fast broadband impedance detection of single cells at a low hardware cost. The impedance data under multiplex frequencies was obtained to uncover the dielectric properties of white blood cells (WBCs) and MCF-7 cancer cells. The machine learning was used to train the impedance data and to identify cell types. The results indicated that 98.98% of MCF-7 cells and 98.65% of WBCs were correctly identified. Our MIC showed a potential to be developed as a cost-effective and portable device for point-of-care testing of circulating tumor cells from patients' peripheral blood.
查看更多>>摘要：It is generally accepted that glucose oxidase (GOx) shows unique specificity in 13-D-glucose catalysis. However, it has been found that GOx can catalyze diverse monosaccharides. Therefore, the sensing accuracy for glucose biosensors using GOx as probes will be largely compromised by the presence of other monosaccharides. Herein, multifunctional bi-nanospheres (Fe3O4@Au NCs), which show both peroxidase-like and catalase-like catalytic activities in different working conditions, are successfully constructed and served as desirable platform with huge surface area for the immobilization of large amount of GOx probes. In acidic environment, hydroxyl radicals could be generated via the cascaded catalysis of beta-D-glucose by Fe3O4@Au-GOx, and then employed to initiate the polymerization of boric acid derivative to prepare molecularly imprinted polymers (MIPs) on the surface of GOx using beta-D-glucose as template. Then, the molecularly imprinted GOx are immobilized on the surface of highly oriented pyrolytic graphite (HOPG) electrode and an electrochemical biosensor (Fe3O4@Au-GOx-HOPG) for glucose sensing is successfully obtained. Interestingly, the as-prepared biosensors could selectively detect glucose in the range of 10.0 mu M -5.0 mM with a LOD = 5.0 mu M with the help of MIPs, which is comparable or better than other glucose sensors reported recently.
查看更多>>摘要：Intensive production of nanomaterials, especially metallic nanoparticles (MNPs), and their release into the environment pose several risks for humans and ecosystem health. Consequently, high-efficiency analytical methodologies are required for control and characterization of these emerging pollutants. Single-particle inductively coupled plasma - mass spectrometry (SP-ICP-MS) is a promising technique which allows the determination and characterization of MNPs. However, several elements or isotopes are hampered by spectral interferences, and dynamic-reaction cell (DRC) technology is becoming a useful tool for free interference determination by ICP-MS. DRC-based SP-ICP-MS methods using ammonia as a reaction gas (either on-mass approach or mass-shift approaches) have been developed for determining titanium dioxide nanoparticles (TiO2 NPs), copper oxide nanoparticles (CuO NPs), copper nanoparticles (Cu NPs), and zinc oxide nanoparticles (ZnO NPs). The effects of parameters such as ammonia flow rate and dwell time on the peak width (NP transient signal in SP-ICP-MS) were comprehensively studied. Influence of NP size and nature were also investigated.
Teglia, Carla M.Gutierrez, Fabiana A.Goicoechea, Hector C.
9页
查看更多>>摘要：This work reports for the first time the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multi-wall carboxylated carbon nanotubes (MWCNTs-COOH) using a mixture of a natural deep eutectic solvent (NADES LGH/lactic acid-glucose-water), ethylene glycol (EG) and water (GCE/MWCNT-LGH-EG) for the determination and N-(4-hydroxyphenyl) acetamide (paracetamol) (APAP) in urine samples. The optimization of both dispersion and measurement conditions was carried out using experimental design. The modified electrode exhibited enhanced current responses, demonstrating excellent electrochemical response towards APAP oxidation compared to MWCNTs-LGH, MWCNTs-EG, MWCNTs-H2O-EtOH and MWCNTs-H2O. The linear dependence between the anodic peak currents and the square root of scan rates over the range of 0.010-0.300 Vs(-1) demonstrates that the electro oxidation of APAP occurs under diffusional control. The MWCNT-LGH-EG modified GCE displayed an analytical sensitivity of 10.72 mL mu g(-1) (r = 0.9994) and a detection limit of 100 ng mL(-1) for the selective determination of APAP in urine samples. The proposed electrochemical sensor was successfully applied for quantifying APAP in urine samples in the presence of uric acid. In addition, the accuracy and precision of the method was contrasted against a HPLC reference method.
查看更多>>摘要：A fast and efficient dsDNA library-immobilized magnetic bead-based SELEX technique was employed for selection of the aptamers against polysialic acid (PSA). Overall twelve rounds of screening, the pooled library was subjected to high-throughput sequencing. Five aptamer candidates with low Gibbs binding free energy and high abundance were selected for affinity evaluation. Apt3 was demonstrated to be the optimal aptamer for PSA with Kd of 114.0 nM. Furthermore, an ultrasensitive fluorescence resonance energy transfer (FRET)-based biosensor for PSA was constructed by employing the newly selected aptamer and catalytic hairpin assembly (CHA) amplification strategy. The linear detection range for PSA is from 10 pM to 1 mu M and the limit of detection is 0.63 pM. The fluorescent biosensor is able to detect the target in the complex biological samples, which indicates that Apt3 has good application prospect for the biological detection and clinical diagnostics.
查看更多>>摘要：Various signal amplification strategies have been developed for microRNA (miRNA) detection, but most of these amplification strategies always need some enzymes. In this work, we have constructed an enzyme-free signal amplification method for miRNA determination via target-triggered catalytic hairpin assembly (CHA). Two hairpin probes (H1 and H2) were ingeniously designed, and fluorescein (FAM)-labeled H1 (as a signal reporter) was conjugated on the gold nanoparticles (AuNPs) surface. In the presence of target miRNA, the cyclic self assembly took place between H1 and H2 on the AuNPs, resulting in amplification of the fluorescence signal. Using miRNA-21 as a model analyte, the linear concentration range for miRNA-21 detection was from 0.1 nM-10 nM under the optimized experimental conditions (25 mu L AuNPs (3 nM), 100 nM H2, 25 degrees C, pH 7.4). The fluorescence method exhibited high sensitivity to with a 10 pM detection limit. The recoveries in 2% normal human serum were in the range of 96.4%-103.6%. What's more, it was found that the addition of ten thymine bases (T-10) as spacer between H1 and AuNPs could significantly accelerate the CHA reaction. A complete analysis for the determination of miRNA could be accomplished within 45 min, which is faster than a number of previous reports.
Kim, SeokjoonHan, JinjooPark, Jung SooKim, Jung Ho...
9页
查看更多>>摘要：Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths worldwide. The standard methods for diagnosing CRC, endoscopy and tissue biopsy, are invasive and timeconsuming. Herein, we propose a novel method for the accurate and non-invasive diagnosis of CRC based on the analysis of exosomes that are circulating in biological fluids using a DNA barcode-based nucleic acid lateral flow assay (NALFA). Our technology combines reverse transcription using a stem-loop primer with DNA barcodebased NALFA. A colorimetric signal is generated only in the presence of the target exosomal miRNA, which can be determined even with the naked eye. The proposed system successfully detected miR-92a and miR-141, which are overexpressed in CRC exosomes. Moreover, when applied to plasma samples from CRC patients, our system simultaneously detected multiple markers in one strip. By combining these markers, we achieved high analytical performance with a sensitivity and a specificity of 95.24% and 100.0%, respectively, demonstrating that the proposed assay can be a simple diagnostic platform for the detection of exosomal miRNA.
查看更多>>摘要：Characterization of serum glycoprotein N-glycans with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) in positive-ion mode needs a derivatization step to stabilize and neutralize the negative charge on sialic acids. The acidic sugars are attached to the end of glycoproteins, glycolipids or gangliosides. Here, we present a method for sialic acid stabilization via modification based on derivatization of carboxylic acid group activated with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) with methylamine. DMTMM substitutes in many processes N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide (EDC/NHS) as activation reagent due to its better performance and higher stability in water. Glycosylated proteins are used as solid phase support for glycan derivatization and purification from excess of derivatization reagents. We evaluated our glycan analysis method in murine sera and intestinal lavages. The stabilization of sialic acid enables a complete conservation of the glycan structures, in contrast to other methods where sialic acids are partially lost. In BALB/c mouse sera, we detected predominantly mono-and di-sialylated N-glycans with mostly N-Glycolylneuraminic acid (Neu5Gc) and only trace amounts of N-Acetyl neuraminic acid (Neu5Ac). BALB/c mouse intestinal lavages glycoproteins contained asialo N-glycans. DMTMM-mediated methylamidation of N-glycans for MALDI mass spectrometry analysis is a fast and cheap method for structurally conserved glycan derivatization.
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Elsevier