Development and characterization of DNA aptamers against florfenicol: Fabrication of a sensitive fluorescent aptasensor for specific detection of florfenicol in milk

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Atefeh Sarafan Sadeghi, Mohammad Mohsenzadeh, Khalil Abnous, Seyed Mohammad Taghdisi, Mohammad Ramezani
Specific ssDNA aptamers for the antibiotic florfenicol (FF) were developed from an enriched nucleotide library using magnetic beads-based SELEX (Systematic Evolution of Ligands by EXponential enrichment) technique with high-binding affinity. After 12 rounds of selection, thirty-six sequences were obtained that were then divided into five major families, according to the primary sequence similarity. Binding affinity analyses of three fluorescently tagged aptamers belonging to different families demonstrated that the dissociation constants (Kd) were in the low nanomolar range (Kd = 52.78–211.4 nmol L⁻¹). Furthermore, to verify the potential application of the aptamers, a fluorescent aptasensor was fabricated for detecting the FF residue in raw milk samples based on the energy transfer between graphene oxide as the acceptor and fluorescently tagged FF-specific aptamer as the donor. Under optimal conditions, the aptasensor displayed a wide linear range from 5 to 1200 nmol L⁻¹ and a detection limit of 5.75 nmol L⁻¹ with excellent selectivity in milk. The recovery rate in the milk was between 101% ± 0.14% and 110% ± 2.8%, indicating high accuracy. This fluorescent aptasensor possessed considerable potential for rapid analysis of FF in raw milk because of its simplicity of detection. Moreover, the interaction between the aptamer and FF was studied using molecular modeling.

Graphical abstract

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Dual-target recognition sandwich assay based on core-shell magnetic mesoporous silica nanoparticles for sensitive detection of breast cancer cells

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Weiwei Wang, Suqin Liu, Chengjie Li, Yan Wang, Chao Yan
A novel dual-target recognition sandwich strategy for selective capture and detection of MCF-7 breast cancer cells based on core-shell magnetic mesoporous silica (Fe3O4@nSiO2@mSiO2@apt) nanoparticles was developed. Fe3O4@nSiO2@mSiO2@apt nanoparticles, which were prepared by a layer-by-layer method and were used for the first time to capture cancer cells, have large surface areas, particularly accessible mesochannels, and good biocompatibility, enabling aptamers to be compactly anchored onto the surface of the core-shell magnetic nanoparticles. A mucin 1 protein (MUC1)-targeted Fe3O4@nSiO2@mSiO2@apt nanoparticle was used as an affinity magnetic isolate material to capture target MCF-7 cells selectively and to reduce interference through affinity interaction between the anti-MUC1 aptamer and the MUC1 protein over-expressed on the surface of the MCF-7 cells. Meanwhile, a folate receptor (FR)-targeted affinity fluorescent probe (FA-BSA-FITC) was developed by coupling folic acid and FITC to the surface of BSA, enabling high sensitivity, selective fluorescent labeling of FR over-expressed MCF-7 cells. A dual-target recognition sandwich assay was developed based on the MUC1-targeted magnetic nanoparticles and the FR-targeted fluorescent probes. Under optimum conditions, a quantitative assay of MCF-7 cells was achieved with a dynamic range of 10²–10⁵ cells/mL (R² = 0.9991). This assay showed high specificity and sensitivity to the target MCF-7 cells. Finally, the proposed strategy could be extended to detect MCF-7 cells in human plasma and whole blood with a recovery range of 86.1–104.0% and a RSD range of 1.2–8.4%, respectively. This indicates that the dual-target recognition method developed in this research exhibits good selectivity, anti-interference capability, and reliability even in plasma and whole blood samples and is more suitable for complex samples than previous targeted assays. Therefore, the approach proposed here may have great potential for early breast cancer diagnosis.

Graphical abstract

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Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy for the noninvasive analysis of transparent samples and gemstones

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): C. Koral, M. Dell'Aglio, R. Gaudiuso, R. Alrifai, M. Torelli, A. De Giacomo
In this paper, Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy is applied to transparent samples and gemstones with the aim to overcome the laser induced damage on the sample. We propose to deposit a layer of AuNPs on the sample surface by drying a colloidal solution before ablating the sample with a 532 nm pulsed laser beam. This procedure ensures that the most significant fraction of the beam, being in resonance with the AuNP surface plasmon, is mainly absorbed by the NP layer, which in turn results the breakdown to be induced on NPs rather than on the sample itself. The fast explosion of the NPs and the plasma induction allow the ablation and the transfer in the plasma phase of the portion of sample surface where the NPs were placed. The employed AuNPs are prepared in milliQ water without the use of any chemical stabilizers by Pulsed Laser Ablation in Liquids (PLAL), in order to obtain a strict control of composition and impurities, and to limit possible spectral interferences (except from Au emission lines). Therefore with this technique it is possible to obtain, together with the emission signal of Au (coming from atomized NPs), the emission spectrum of the sample, by limiting or avoiding the direct interaction of the laser pulse with the sample itself. This approach is extremely useful for the elemental analysis by laser ablation of high refractive index samples, where the laser pulse on an untreated surface can otherwise penetrate inside the sample, generate breakdown events below the superficial layer, and consequently cause cracks and other damage. The results obtained with NELIBS on high refractive index samples like glasses, tourmaline, aquamarine and ruby are very promising, and demonstrate the potentiality of this approach for precious gemstones analysis.

Graphical abstract

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Rapid and robust analytical protocol for E. coli STEC bacteria subspecies differentiation using whole cell MALDI mass spectrometry

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Kevin Mclean, Javier Palarea-Albaladejo, Carol G. Currie, Lisa H.J. Imrie, Erin D.T. Manson, Douglas Fraser-Pitt, Frank Wright, Colin J. Alexander, Kevin G.J. Pollock, Lesley Allison, Mary Hanson, David G.E. Smith
Whole cell MALDI is regularly used for the identification of bacteria to species level in clinical Microbiology laboratories. However, there remains a need to rapidly characterize and differentiate isolates below the species level to support outbreak management. We describe the implementation of a modified preparative approach for MALDI-MS combined with a custom analytical computational pipeline as a rapid procedure for subtyping Shigatoxigenic E. coli (STEC) and accurately identifying strain-specifying biomarkers. The technique was able to differentiate E. coli O157:H7 from other STEC. Within O157 serotype O157:H7 isolates were readily distinguishable from Sorbitol Fermenting O157 isolates. Overall, nine homogeneous groups of isolates were distinguished, each exhibiting distinct profiles of defining mass spectra features. This offers a robust analytical tool useable in reference/diagnostic public health scenarios.

Graphical abstract

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Two-dimensional liquid chromatography consisting of twelve second-dimension columns for comprehensive analysis of intact proteins

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Jiangtao Ren, Matthew A. Beckner, Kyle B. Lynch, Huang Chen, Zaifang Zhu, Yu Yang, Apeng Chen, Zhenzhen Qiao, Shaorong Liu, Joann J. Lu
A comprehensive two-dimensional liquid chromatography (LCxLC) system consisting of twelve columns in the second dimension was developed for comprehensive analysis of intact proteins in complex biological samples. The system consisted of an ion-exchange column in the first dimension and the twelve reverse-phase columns in the second dimension; all thirteen columns were monolithic and prepared inside 250 µm i.d. capillaries. These columns were assembled together through the use of three valves and an innovative configuration. The effluent from the first dimension was continuously fractionated and sequentially transferred into the twelve second-dimension columns, while the second-dimension separations were carried out in a series of batches (six columns per batch). This LCxLC system was tested first using standard proteins followed by real-world samples from E. coli. Baseline separation was observed for eleven standard proteins and hundreds of peaks were observed for the real-world sample analysis. Two-dimensional liquid chromatography, often considered as an effective tool for mapping proteins, is seen as laborious and time-consuming when configured offline. Our online LCxLC system with increased second-dimension columns promises to provide a solution to overcome these hindrances.

Graphical abstract

http://ift.tt/2EICGnS

A compact and low-cost laser induced fluorescence detector with silicon based photodetector assembly for capillary flow systems

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Xuhui Geng, Meng Shi, Haijing Ning, Chunbo Feng, Yafeng Guan
A compact and low-cost laser induced fluorescence (LIF) detector based on confocal structure for capillary flow systems was developed and applied for analysis of Her2 protein on single Hela cells. A low-power and low-cost 450 nm laser diode (LD) instead of a high quality laser was used as excitation light source. A compact optical design together with shortened optical path length improved the optical efficiency and detection sensitivity. A superior silicon based photodetector assembly was used for fluorescence detection instead of a photomultiplier (PMT). The limit of detection (LOD) for fluorescein sodium was 3 × 10^–12 M or 165 fluorescein molecules in detection volume measured on a homemade capillary electroosmotic driven (EOD)-LIF system, which was similar to commercial LIFs. Compared to commercial LIFs, the whole volume of our LIF was reduced to 1/2–1/3, and the cost was less than 1/3 of them.

Graphical abstract

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An electrochemical immunosensor for cardiac Troponin I using electrospun carboxylated multi-walled carbon nanotube-whiskered nanofibres

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Babak Rezaei, Ahmad Mousavi Shoushtari, Mohammad Rabiee, Lokman Uzun, Wing Cheung Mak, Anthony P.F. Turner
A sandwich-type nanostructured immunosensor based on carboxylated multi-walled carbon nanotube (CMWCNT)-embedded whiskered nanofibres (WNFs) was developed for detection of cardiac Troponin I (cTnI). WNFs were directly fabricated on glassy carbon electrodes (GCE) by removing the sacrificial component (polyethylene glycol, PEG) after electrospinning of polystyrene/CMWCNT/PEG nanocomposite nanofibres, and utilised as a transducer layer for enzyme-labeled amperometric immunoassay of cTnI. The whiskered segments of CMWCNTs were activated and utilised to immobilise anti-cTnT antibodies. It was observed that the anchored CMWCNTs within the nanofibres were suitably stabilised with excellent electrochemical repeatability. A sandwich-type immuno-complex was formed between cTnI and horseradish peroxidase-conjugated anti-cTnI (HRP-anti-cTnI). The amperometric responses of the immunosensor were studied using cyclic voltammetry (CV) through an enzymatic reaction between hydrogen peroxide and HRP conjugated to the secondary antibody. The nanostructured immunosensor delivered a wide detection range for cTnI from the clinical borderline for a normal person (0.5–2ngmL⁻¹) to the concentration present in myocardial infarction patients (> 20ngmL⁻¹), with a detection limit of ~ 0.04ngmL⁻¹. It also showed good reproducibility and repeatability for three different cTnI concentration (1, 10 and 25ngmL⁻¹) with satisfactory relative standard deviations (RSD). Hence, the proposed nanostructured immunosensor shows potential for point-of-care testing.

Graphical abstract

http://ift.tt/2GvAzjC

A simple and economical spectrofluorimetric alternative for Al routine analysis in seafood

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): José A. López-López, Carlos Borrego-Corchado, Manuel P. Mánuel, Estrella Espada-Bellido
A simple and economical spectrofluorimetric alternative for aluminium determination in bivalve mollusks based on the fluorescent blue-green colour complex between Al(III) and salicylaldehyde picolinoylhydrazone (SAPH) has been studied. The factors that are most likely to affect were optimized with a Box-Behnken design. Optimum conditions were: pH 6.6, 0.9 mol L⁻¹ acetic acid/acetate buffer, 3.0 mmol L⁻¹ SAPH, and 50% ethanol. Detection and quantitation limits were found to be 2.7 μg L⁻¹ and 9.1 μg L⁻¹, respectively. The upper limit of application was assessed through the limit of linearity which was set as 300 μg L⁻¹. Intra-day repeatability and inter-day repeatability were evaluated showing an excellent precision for the fluorescence method (both < 5%). The method was sensitive enough for the satisfactory determination of aluminium in several bivalve mollusk samples both fresh and canned seafood. The results showed that commercial fresh wild products presented the smallest Al concentration (6–27 mg per 100 g dry weight), while bivalves preserved in cans the concentration was considerably higher (75 mg per 100 g dry weight). Thus, differences between Al concentration related to processing were identified. The study shows a simple, cost-effective and reliable tool for routine aluminium determination in seafood for food quality control.

Graphical abstract

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An overview of the main foodstuff sample preparation technologies for tetracycline residue determination

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Michael Pérez-Rodríguez, Roberto Gerardo Pellerano, Leonardo Pezza, Helena Redigolo Pezza
Tetracyclines are widely used for both the treatment and prevention of diseases in animals as well as for the promotion of rapid animal growth and weight gain. This practice may result in trace amounts of these drugs in products of animal origin, such as milk and eggs, posing serious risks to human health. The presence of tetracycline residues in foods can lead to the transmission of antibiotic-resistant pathogenic bacteria through the food chain. In order to ensure food safety and avoid exposure to these substances, national and international regulatory agencies have established tolerance levels for authorized veterinary drugs, including tetracycline antimicrobials. In view of that, numerous sensitive and specific methods have been developed for the quantification of these compounds in different food matrices. One will note, however, that the determination of trace residues in foods such as milk and eggs often requires extensive sample extraction and preparation prior to conducting instrumental analysis. Sample pretreatment is usually the most complicated step in the analytical process and covers both cleaning and pre-concentration. Optimal sample preparation can reduce analysis time and sources of error, enhance sensitivity, apart from enabling unequivocal identification, confirmation and quantification of target analytes. The development and implementation of more environmentally friendly analytical procedures, which involve the use of less hazardous solvents and smaller sample sizes compared to traditional methods, is a rapidly increasing trend in analytical chemistry. This review seeks to provide an updated overview of the main trends in sample preparation for the determination of tetracycline residues in foodstuffs. The applicability of several extraction and clean-up techniques employed in the analysis of foodstuffs, especially milk and egg samples, is also thoroughly discussed.

Graphical abstract

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High-throughput quantification of sodium saccharin in foods by ambient flame ionization mass spectrometry

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Zhongquan Li, Fang Zhang, Junbo Zhao, Xiaopan Liu, Xiuping Chen, Yue Su, Yinlong Guo
Ambient flame ionization (AFI) coupled with triple quadrupole tandem mass spectrometry was developed for quantitative analysis of sodium saccharin (SAC) in various food samples. Typically, the micro-flame by the combustion of n-butane provided a heating zone for fast desorption and ionization of analytes in milliseconds. Then high ion abundance of analyte could be produced in a short time, which made AFI-MS possess a very high sensitivity for SAC detection and was particularly appropriate for the quantification in multiple reaction monitor (MRM) mode. Liquid samples were introduced into outer flame using dip-it tips in order to facilitate a rapid and high-throughput analysis. Saccharin-d4 was used as the internal standard to compensate for the variations of the ion intensities. With a minimal sample preparation, a linear range of 4–100 μg/mL was developed with all linear relationships of different matrices (including coke, juice, liquors, sunflower seeds and sweetmeats) greater than 0.992. Recoveries for coke and apple matrices were ranged from 88.4% to 108.9% at the concentration of 5, 20, 80 μg/mL and the limits of detection (LODs) were in the range of 0.12–0.21 μg/mL. Furthermore, the feasibility of this method was exhibited by the quantification analysis of SAC in seventeen real samples. These results indicated that AFI-MS was a valuable strategy for rapid screening detection and precise quantification analysis of SAC in food.

Graphical abstract

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Untargeted screening of phase I metabolism of combretastatin A4 by multi-tool analysis

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Karol Jaroch, Paulina Zofia Goryńska, Krzysztof Goryński, Tomasz Stefański, Barbara Bojko
The aim of the current study was to apply different strategies for generation of metabolites of combretastatin A4 (CA4) and subsequent identification of the unknown products of phase I metabolism. CA4 is a potent anti-tubulin agent currently undergoing clinical trials. The multi-tool analytical approach was based on electrochemistry (EC), in silico predictions, and in vitro studies with the use of rat liver microsomes. With the latter, two different analytical sample preparation methods were applied: protein precipitation and solid phase microextraction, both hyphenated to the liquid chromatography-high-resolution mass spectrometry platform (LC-HRMS). The EC was coupled directly to HRMS. Conventional techniques using enzyme fractions pooled from human or animals remain a method of choice for determinations of phase I of drug metabolism, EC and in silico methods, which enable determinations of metabolism patterns, are in turn considered to have great potential as fast alternatives to in vitro assays. While individual findings attained via employment of these four methods showed high similarity in relation to generated metabolic pathways for CA4, each method was found to provide unique features not identified with other approaches. In this paper, these differences are reviewed in view of potential artifacts and true metabolite production via various metabolism patterns under different experimental conditions. In addition, the reliability, applicability, MS compatibility issues, and potential of each of these technologies are discussed.

Graphical abstract

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Renewable chemiluminescence optosensors based on implementation of bead injection principle with multicommutation

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Juan C. Domínguez-Romero, Bienvenida Gilbert-López, Miriam Beneito-Cambra, Antonio Molina-Díaz
In this work, the implementation of Bead Injection with multicommutation-based flow systems is reported. A surface renewable chemiluminescence (CL) flow sensor is presented based on the use of CL reaction of luminol with H2O2. Dowex 1 × 8 beads with immobilized luminol onto them were injected in the flow system by means of a six-port rotary valve and were accommodated into a 1 mm optical glass flow cell placed just in front of the rectangular photosensor window with the same size than the cell wall. Automatic computer-controlled manipulation of both reagents and sample solutions was undertaken using a multicommutated flow system which comprises five three-way solenoid valves, a home-made electronic interface and a Java-written software. Once the chemiluminescence signal was registered, sensing beads were automatically discarded out with a six-port rotary valve without needing to reverse or stop the flow. As a proof of concept and example, the enhancement of the chemiluminescence signal produced by Co(II) on the luminol-H2O2 reaction in alkaline medium was used for illustrating this implementation determining vitamin B12 in pharmaceutical preparations (after mineralization for releasing Co(II)). The analytical performance of the approach was satisfactory, showing a linear dynamic range from 1.7 to 50 µg L⁻¹, a detection limit of 0.5 µg L⁻¹, RSD (%) of 5.3%, with a sampling frequency of 11 h⁻¹. The proposed approach was applied to different samples and the results were consistent with those obtained with a reference method based on ICP-MS. Based on the same reaction (or re-configuring the system to accommodate it to reaction requirements) the approach can also be applied to the determination of other metal ions such as Cr(III) and Fe(II) and appropriately extended to molecules of bioanalytical interest based e.g. in CL immunoassays, given its versatility.

Graphical abstract

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A novel strategy for discriminating marine oils by using the positional distribution (sn-1, sn-2, sn-3) of omega-3 polyunsaturated fatty acids in triacylglycerols

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Pedro Araujo, Ephrem Tilahun, Yingxu Zeng
A novel strategy for discriminating genuine and adulterated marine oils is proposed. The strategy consists of i) determining the stereospecific distribution (sn-1, sn-2 and sn-3) of omega 3 polyunsaturated fatty acids (ω−3 PUFA) on the backbone of triacylglycerols by using liquid chromatography tandem mass spectrometry; ii) transforming the qualitative stereospecific information into quantitative data by means of a novel strategy; iii) analyzing the transformed data by principal component analysis. The proposed strategy was tested on pure oils (seal, salmon, cod liver, sandeel, blue whiting, herring), a mixture of blue whiting, herring, sandeel and Norway pout and some intentionally adulterated oils. In addition, some published krill oil data were analyzed to confirm the reliability of the new approach.

Graphical abstract

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A new electrochemical immunoassay for prion protein based on hybridization chain reaction with hemin/G-quadruplex DNAzyme

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Xiaoyu Li, Junjing Li, Caixia Zhu, Xiaohua Zhang, Jinhua Chen
In this work, a new electrochemical immunosensor was developed for prion protein assay based on hybridization chain reaction (HCR) with hemin/G-quadruplex DNAzyme for signal amplification. In this amplification system, the hemin/G-quadruplex DNAzyme simultaneously mimicked the biocatalytic functions for H2O2 reduction and L-cysteine oxidation. In the presence of L-cysteine, the hemin/G-quadruplex catalyzed the oxidation of L-cysteine to L-cystine. At the same time, H2O2 was produced under the oxygen condition. Then, the hemin/G-quadruplex could quickly catalyze the reduction of H2O2, mimicking the catalytic performance of horseradish peroxidase (HRP). Under the optimal conditions, the immunosensor showed a wide linear response range from 0.5 pg/mL to 100 ng/mL with the low detection limit of 0.38 pg/mL (3σ). By changing the specific antibody, this strategy could be easily extended to detect the infectious isoform of prion (PrP^Sc) and other proteins. Based on its good analytical performance, the developed method shows great potential applications in diagnosis of prion diseases at presymptomatic stage and bioanalysis.

Graphical abstract

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Covalent functionalization of MoS2 nanosheets synthesized by liquid phase exfoliation to construct electrochemical sensors for Cd (II) detection

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Xiaorong Gan, Huimin Zhao, Kwok-Yin Wong, Dang Yuan Lei, Yaobin Zhang, Xie Quan
Surface functionalization is an effective strategy in the precise control of electronic surface states of two-dimensional materials for promoting their applications. In this study, based on the strong coordination interaction between the transition-metal centers and N atoms, the surface functionalization of few-layer MoS2 nanosheets was successfully prepared by liquid phase exfoliation method in N, N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone, and formamide. The cytotoxicity of surface-functionalized MoS2 nanosheets was for the first time evaluated by the methylthiazolyldiphenyl-tetrazoliumbromide assays. An electrochemical sensor was constructed based on glass carbon electrode (GCE) modified by MoS2 nanosheets obtained in DMF, which exhibits relatively higher sensitivity to Cd²⁺ detection and lower cytotoxicity against MCF-7 cells. The mechanisms of surface functionalization and selectively detecting Cd²⁺ were investigated by density functional theory calculations together with various spectroscopic measurements. It was found that surface-functionalized MoS2 nanosheets could be generated through Mo-N covalent bonds due to the orbital hybridization between the 5 s orbitals of Mo atoms and the 2p orbitals of N atoms of the solvent molecules. The high selectivity of the sensor is attributed to the coordination reaction between Cd²⁺ and O donor atoms of DMF adsorbed on MoS2 nanosheets. The robust anti-interference is ascribed to the strong binding energy of Cd²⁺ and O atoms of DMF. Under the optimum conditions, the electrochemical sensor exhibits highly sensitive and selective assaying of Cd²⁺ with a measured detection limit of 0.2 nM and a linear range from 2 nM to 20 μM.

Graphical abstract

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Fabrication of Pd-decorated TiO2/MoS2 ternary nanocomposite for enhanced benzene gas sensing performance at room temperature

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Dongzhi Zhang, Chuanxing Jiang, Xiaoyan Zhou
A high-performance benzene gas sensor based on Pd-decorated TiO2/MoS2 ternary nanocomposite was demonstrated in this paper. The morphologies, microstructures and composition of the Pd-TiO2/MoS2 nanocomposite were sufficiently examined by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS), confirming its successful preparation and reasonability. The benzene-sensing performances of the Pd-TiO2/MoS2 sensor were investigated upon exposure to various concentrations of benzene vapor from 100 ppb to 100 ppm at room temperature. The experimental results showed that the sensor has a high response, short response-recovery time, good repeatability and selectivity toward benzene gas, which is largely superior to that of the pure TiO2 and MoS2 sensors. In addition, the influence of Pd loading in the nanocomposite on the benzene-sensing was investigated. The sensing mechanism of the Pd-TiO2/MoS2 sensor was attributed to the synergistic effect of the ternary nanostructures, combining the modulation of potential barrier with electron transfer. This work indicates that the synthesized Pd-TiO2/MoS2 ternary nanocomposite is an excellent candidate for constructing high-performance benzene sensor for various applications.

Graphical abstract

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A multifunctional molecularly imprinted polymer-based biosensor for direct detection of doxycycline in food samples

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Jon Ashley, XiaoTong Feng, Yi Sun
In this study, we developed a new type of multifunctional molecularly imprinted polymer (MIP) composite as an all-in-one biosensor for the low-cost, rapid and sensitive detection of doxycycline in pig plasma. The MIP composite consisted of a magnetic core for ease of manipulation, and a shell of fluorescent MIPs for selective recognition of doxycycline. By simply incorporating a small amount of fluorescent monomer (fluorescein-O-acrylate), the fluorescent MIP layer was successfully grafted onto the magnetic core via a surface imprinting technique. The resultant MIP composites showed significant doxycycline-dependent fluorescence quenching in an aqueous environment. Good linearity ranging from 0.2 to 6 µM was achieved, and the limit of detection was determined to be 117 nM. The biosensor also showed good selectivity towards doxycycline when compared to other common antibiotic residues. The multifunctional MIP composites were used to directly extract doxycycline from spiked pig plasma samples and quantify the antibiotics based on the quenched fluorescence signals. Recoveries of doxycycline were found in the range of 88–107%.

Graphical abstract

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Analysis of metallic nanoparticles and their ionic counterparts in complex matrix by reversed-phase liquid chromatography coupled to ICP-MS

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Yuan Yang, Li Luo, Hai-Pu Li, Qiang Wang, Zhao-Guang Yang, Zhi-Peng Qu, Ru Ding
Developing quantification and characterization methodology for metallic nanoparticles (MNPs) and their ionic component in complex matrix are crucial for the evaluation of their environmental behavior and health risks to humans. In this study, reversed phase high performance liquid chromatography combined ICP-MS was established for the characterization of MNPs in complex matrix. The ionic component could be separated from NPs with the optimized parameters of aqueous mobile phase. Good linear relationship between average diameter and retention time of NPs was obtained using HPLC-ICP-MS and the size smaller than 40 nm could be determined with this method, the detected results were in accordance with TEM results. The low detection limit of AuNPs and Au(Ⅲ) (both in sub-μg/L level) showed that this method was promising for the characterization of AuNPs and Au(Ⅲ) in environmental water. The mass concentration of ionic Au(Ⅲ) in environmental water could be detected using the proposed HPLC-ICP-MS and the concentration of AuNPs was obtained by subtracting the Au(Ⅲ) concentration from the total Au (The concentration of total Au was detected by ICP-MS after microwave digestion). Furthermore this proposed HPLC-ICP-MS method and single particle-ICPMS (SP-ICP-MS) was used for the analysis of the Ag speciation in commercial antibacterial products.

Graphical abstract

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A novel cerium oxide nanoparticles–based colorimetric sensor using tetramethyl benzidine reagent for antioxidant activity assay

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): F. Ayca Ozdemir Olgun, Ayşem Üzer, Birsen Demirata Ozturk, Reşat Apak
Antioxidant activity (AOA) assays using nanotechnology are recently developed utilizing nanoparticles of transition metal oxides, especially nanoceria that can switch between trivalent and tetravalent oxidation states of cerium. Cerium oxide nanoparticles (CeO-NPs) may act as both an oxidant and an antioxidant, depending on the preparation method and particle size. A novel colorimetric sensor for AOA assay is proposed with the use of poly(acrylic acid) sodium salt (PAANa)˗coated CeO-NPs. PAANa˗coated CeO-NPs oxidized tetramethyl benzidine (TMB), a peroxidase substrate, in a slightly acidic solution at pH 4.0 to a blue charge-transfer complex. Antioxidants decreased the color intensity of the nanoceria suspension, and were indirectly determined by absorbance difference. Detection limits, linearity, additivity and precision were calculated, e.g., quercetin quantification with the proposed assay showed a detection limit of 8.25 × 10⁻⁹ mol L⁻¹. The trolox equivalent antioxidant capacities of hydrophilic and lipophilic antioxidants were compatible with those of conventional antioxidant assays. Potential interferents such as glucose, citric acid, mannitol, sorbitol and benzoic acid did not adversely affect AOA determination. The developed sensor is more sensitive and selective than similar colorimetric sensors relying on the intrinsic color change of nanoceria. The measurement wavelength is sufficiently red-shifted, preventing possible interferences from plant pigments.

Graphical abstract

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Light-assisted preparation of vancomycin chiral stationary phase based on diazotized silica and its enantioseparation evaluation by high-performance liquid chromatography

Publication date: 15 May 2018
Source:Talanta, Volume 182
Author(s): Bing Yu, Shuai Zhang, Guoling Li, Hailin Cong
Owing to enantiomers' identical physical and chemical properties, separation work in the chiral environments is still a great challenge.and chemical properties. Chromatographic techniques employing chiral stationary phases (CSPs) have been developed as powerful tools for the chiral analysis and preparation of pure enantiomers. Here we report a facile synthesis of vancomycin stationary phase based on diazotized silica. Monodisperse silica particles were synthesized by a modified Stöber method. The obtained silica particles were modified by self-assembly photosensitive diazoresin (DR) and vancomycin on the surface. After treatment with UV light, the ionic bonding was converted into covalent bonding through a unique photochemistry reaction of DR. Baseline separation of chiral drugs was achieved by using the vancomycin@SiO2 particles as packing materials in high performance liquid chromatography (HPLC). The effects of separation parameters including elution mode, flow rate and analyte mass on the enantioselectivity of the CSP were investigated in detail. Due to the replacement of highly toxic and moisture sensitive silane agent by water soluble non-toxic DR in the modification of silica microspheres, this method provides a green and easy way to manufacture packing materials for chromatography applications.

Graphical abstract

http://ift.tt/2HyOUx4