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Analytica Chimica Acta (v.751, #)
Fluorescent nanoparticles for intracellular sensing: A review by Maria J. Ruedas-Rama; Jamie D. Walters; Angel Orte; Elizabeth A.H. Hall (pp. 1-23).
Display Omitted► Analytical applications of fluorescent nanoparticles (NPs) in intracellular sensing. ► Critical review on performance of QDots, metal NPs, silica NPs, and polymer NPs. ► Highlighted potential of fluorescence lifetime imaging microscopy (FLIM).Fluorescent nanoparticles (NPs), including semiconductor NPs (Quantum Dots), metal NPs, silica NPs, polymer NPs, etc., have been a major focus of research and development during the past decade. The fluorescent nanoparticles show unique chemical and optical properties, such as brighter fluorescence, higher photostability and higher biocompatibility, compared to classical fluorescent organic dyes. Moreover, the nanoparticles can also act as multivalent scaffolds for the realization of supramolecular assemblies, since their high surface to volume ratio allow distinct spatial domains to be functionalized, which can provide a versatile synthetic platform for the implementation of different sensing schemes. Their excellent properties make them one of the most useful tools that chemistry has supplied to biomedical research, enabling the intracellular monitoring of many different species for medical and biological purposes. In this review, we focus on the developments and analytical applications of fluorescent nanoparticles in chemical and biological sensing within the intracellular environment. The review also points out the great potential of fluorescent NPs for fluorescence lifetime imaging microscopy (FLIM). Finally, we also give an overview of the current methods for delivering of fluorescent NPs into cells, where critically examine the benefits and liabilities of each strategy.
Keywords: Quantum Dots; Gold nanoparticles; Silica nanoparticles; Intracellular sensing; FLIM
Sensing colorimetric approaches based on gold and silver nanoparticles aggregation: Chemical creativity behind the assay. A review by Diana Vilela; María Cristina González; Alberto Escarpa (pp. 24-43).
Display Omitted► Visual detection based gold and silver nanoparticles aggregation. ► Functionalized and non-functionalized nanoparticles. ► High selectivity and sensitivity. ► No complex instrumentation is required/chemical creativity for analyte detection.Localized surface plasmon resonance (LSPR) is one of the most remarkable features of gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs). Due to these inherent optical properties, colloidal solutions of Au and Ag NPs have high extinction coefficients and different colour in the visible region of the spectrum when they are well-spaced in comparison with when they are aggregated. Therefore, a well-designed chemical interaction between the analyte and NPs surroundings leads to a change of colour (red to blue for Au NPs and yellow to brown for Ag NPs from well-spaced to aggregated ones, respectively) allowing the visual detection of the target analyte.These approaches have exhibited an excellent analytical performance with high sensitivities due to the strong LSPR and excellent selectivity strategically driven by the interaction analyte-NPs surroundings involving mainly electrostatic and hydrogen bond interactions as well as donor–acceptor chemical reactions, among others. In addition, this kind of colorimetric assays has received considerable attention in the analytical field because of their simplicity and low cost since they do not require any expensive or complex instrumentation. As a consequence of this, detection of molecules with a high significance in the bio-medical, clinical, food safety and environmental fields including DNA, proteins and a wide spectrum of organic molecules as well as inorganic ions have been impressively reported in the most relevant literature using these assays.This timely review offers a rational vision of the main achievements yielded in the relevant literature according to this exciting and creative analytical field.
Keywords: Abbreviations; AA; Amino Acids; Aden; Adenosine; ALP; Alkaline Phosphatase; ATP; Adenosine triphosphate; CD; Ciclodextrin; Ce; Crown; Coc; Cocaine; CIAP; Calf Intestine Alkaline Phosphatase; Cys; Cysteine; Cyst; Cysteamine; DNA; Deoxyribonucleic acid; ds; Double Stranded; DSL; Dynamic Light Scattering; dT; Deoxythymidylic; DTC; Dithiocarbamate; DAB; Diaminobenzenes; EREs; Estrogen Response Elements; Gluc; Glucose; GOD; Glucose Oxidase; HA; Hyaluronic acid; His; Histidine; HSA; Human serum albumin; Hep; Heparin; hERs; Human Estrogen Receptors; ICP-MS; Inductively coupled plasma mass spectrometry; LCD; Linear concentration dependence; LOD; Limit of Detection; Lysz; Lysozyme; Mel; Melamine; MTA; (11-mercapto-undecyl)-trimethyl ammonium; Ngn3; Neurogenin3; Op; Optunal; PCR; Polymerase chain reaction; PKA; Protein kinase A; p-NA; p-Nitroanilina; poly-Tn; poly-Thyminen; PRLS; Plasmon Resonance Light Scattering; pSC; 6; p-sulfonatocalix; SNPs; Single Nucleotide Polymorphisms; ss; Single stranded; TEM; Transmission electron microscopy; Thr; Thrombin; TNBS; 2, 4, 6-Trinitrobenzenesulfonic; Tryp; Trypsin; UCA; Uracil-5-carboxylic Acid; FT-IR; Fourier transform infrared spectroscopy; UV; UltravioletGold and silver nanoparticles aggregation; Functionalized and non-functionalized nanoparticles; Colorimetric assays
Validation of analytical methods involved in dissolution assays: Acceptance limits and decision methodologies by E. Rozet; E. Ziemons; R.D. Marini; B. Boulanger; Ph. Hubert (pp. 44-51).
Display Omitted► Novel methodology to validate analytical methods involved in dissolution tests. ► Valid methods will ensure to make the correct decisions with high probability. ► A Quality by Design compliant validation methodology for dissolution assays. ► Analytical Target Profile is defined for dissolution assays. ► Application to the validation of a HPLC–UV analytical method.Dissolution tests are key elements to ensure continuing product quality and performance. The ultimate goal of these tests is to assure consistent product quality within a defined set of specification criteria. Validation of an analytical method aimed at assessing the dissolution profile of products or at verifying pharmacopoeias compliance should demonstrate that this analytical method is able to correctly declare two dissolution profiles as similar or drug products as compliant with respect to their specifications. It is essential to ensure that these analytical methods are fit for their purpose. Method validation is aimed at providing this guarantee. However, even in the ICHQ2 guideline there is no information explaining how to decide whether the method under validation is valid for its final purpose or not. Are the entire validation criterion needed to ensure that a Quality Control (QC) analytical method for dissolution test is valid? What acceptance limits should be set on these criteria? How to decide about method's validity? These are the questions that this work aims at answering. Focus is made to comply with the current implementation of the Quality by Design (QbD) principles in the pharmaceutical industry in order to allow to correctly defining the Analytical Target Profile (ATP) of analytical methods involved in dissolution tests. Analytical method validation is then the natural demonstration that the developed methods are fit for their intended purpose and is not any more the inconsiderate checklist validation approach still generally performed to complete the filing required to obtain product marketing authorization.
Keywords: Quality by Design; Tolerance intervals; Method validation; Analytical Target Profile; Acceptance limits; Dissolution methods
Nanoplatinum-enclosed gold nanocores as catalytically promoted nanolabels for sensitive electrochemical immunoassay by Jun Zhou; Dianping Tang; Li Hou; Yuling Cui; Huafeng Chen; Guonan Chen (pp. 52-58).
Display Omitted► We report a new sandwich-type electrochemical immunoassay of biomarkers. ► Nanoplatinum-enclosed gold nanocores as catalytically promoted nanolabels. ► Dual amplification of electrochemical signal. ► The catalytic reaction of the products.Here we designed a new electrochemical immunoassay protocol for determination of carcinoembryonic antigen (CEA) using nanoplatinum-enclosed gold nanocores (Pt@Au) as catalytically promoted nanolabels on the carbon nanospheres and graphene-modified immunosensor. The Pt@Au nanolabels were synthesized and functionalized with monoclonal anti-CEA antibodies and glucose oxidase (GOx). Using the functional Pt@Au nanolabels as molecular tags, the assay was implemented relative to glucose–hydroquinone system with a sandwich-type immunoassay. Initially, the added glucose was oxidized to gluconolactone and H2O2 by the labeled GOx, and then the generated H2O2 was reduced with the help of platinum nanoparticles, leading to the production of oxygen. The self-produced oxygen could promote the re-oxidation of the glucose, thus resulting in the dual amplification of the electrochemical signal. Several nanolabels, such as multiarmed star-like platinum nanowires, hollow platinum nanospheres and Pt@Au nanostructures, were investigated for CEA detection and improved analytical features were obtained with the Pt@Au nanostructures. Under optimal conditions, the Pt@Au-based immunoassay displayed a wide working range from 0.001 to 120ngmL−1 with a low detection limit of 0.5pgmL−1 CEA at 3 sB. Intra- and inter-assay coefficients of variation were <10.9%. The system was evaluated with 10 clinical serum samples, receiving good accordance with results from enzyme-linked immunosorbent assay method.
Keywords: Electrochemical immunosensor; Nanoplatinum-enclosed gold nanocores; Nanolabels; Carcinoembryonic antigen; Carbon nanospheres-graphene hybrid nanostructures
Poly(methylene blue) functionalized graphene modified carbon ionic liquid electrode for the electrochemical detection of dopamine by Wei Sun; Yuhua Wang; Yuanyuan Zhang; Xiaomei Ju; Guangjiu Li; Zhenfan Sun (pp. 59-65).
Display Omitted► Poly(methylene blue) functionalized graphene was electrodeposited on the electrode. ► The fabricated electrode showed better electrochemical performances. ► Dopamine was sensitive detected by the modified electrode.An ionic liquid 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was used as the substrate electrode and a poly(methylene blue) (PMB) functionalized graphene (GR) composite film was co-electrodeposited on CILE surface by cyclic voltammetry. The PMB–GR/CILE exhibited better electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behavior of dopamine (DA) was further investigated by cyclic voltammetry and a pair of well-defined redox peaks appeared with the peak-to-peak separation (Δ Ep) as 0.058V in 0.1molL−1 pH 6.0 phosphate buffer solution, which proved a fast quasi-reversible electron transfer process on the modified electrode. Electrochemical parameters of DA on PMB–GR/CILE were calculated with the electron transfer number as 1.83, the charge transfer coefficients as 0.70, the apparent heterogeneous electron transfer rate constant as 1.72s−1 and the diffusional coefficient ( D) as 3.45×10−4cm2s−1, respectively. Under the optimal conditions with differential pulse voltammetric measurement, the linear relationship between the oxidation peak current of DA and its concentration was obtained in the range from 0.02 to 800.0μmolL−1 with the detection limit as 5.6nmolL−1 (3 σ). The coexisting substances exhibited no interference and PMB–GR/CILE was applied to the detection of DA injection samples and human urine samples with satisfactory results.
Keywords: Graphene; Poly(methylene blue); Carbon ionic liquid electrode; Electrochemistry; Dopamine
Voltammetric detection of the α-dicarbonyl compound: Methylglyoxal as a flavoring agent in wine and beer by Sanghamitra Chatterjee; Aicheng Chen (pp. 66-70).
Display Omitted► Synergistic electrocatalytic effect of Pt nanoparticles and single-wall carbon nanotubes on the reduction of methylglyoxal. ► Novel electrochemical Pt/SWNT/GCE sensor designed for the determination of methylglyoxal. ► Excellent analytical performance with low detection limit and high sensitivity. ► The developed methylglyoxal sensor shows promising process control, clinical and, biomedical applications.A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were cast on a glassy carbon electrode (GCE) substrate, is presented in this paper. This modified electrode exhibited excellent catalytic activity in the electroreduction of methylglyoxal, showing much higher peak currents than those measured on an unmodified GCE. The effects of different experimental and instrumental parameters, such as solution pH and square wave frequency, were examined. The reduction peak current showed a linear range of from 0.1×10−6 to 100×10−6M with a 0.9979 correlation coefficient; and a low detection limit of 2.8×10−9M was also obtained. The proposed methodology was successfully applied to the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal.
Keywords: Methylglyoxal; Single wall carbon nanotubes; Platinum nanoparticles; Glassy carbon electrode; Wine; Beer
Liquid–liquid–solid microextraction and detection of nerve agent simulants by on-membrane Fourier transform infrared spectroscopy by Prabhat Garg; Ajay Purohit; Vijay K. Tak; Ajeet Kumar; D.K. Dubey (pp. 71-78).
Display Omitted► A novel liquid–liquid–solid microextraction technique has been optimised. ► Markers of CWA have been detected by FTIR spectroscopy avoiding elution step. ► A chemometric PLS approach has been applied for the quantitation of mixture. ► Developed method was validated using unknown sample of official proficiency test.A coupling of novel liquid–liquid–solid microextraction (LLSME) technique based on porous hydrophobic membrane and Fourier-transform infrared spectroscopy has been presented for the detection, identification and quantification of markers and simulants of nerve agents. Two isomers O, O′-dihexyl methylphosphonate (DHMP) and O, O′-dipentyl isopropylphosphonate (DPIPP) were chosen as model analytes for the study. In the present technique, organic phase was immobilised within the pores of membrane after fixing it in an assembly, which was then immersed into aqueous sample of target analytes for extraction. The analytes were directly determined on the surface of membrane by FTIR spectroscopy without elution. On comparison with solid phase microextraction (SPME), LLSME was found to be much more efficient. The method was optimised and quantitative analyses were performed using calibration curves obtained via Beer's law and employing processing of spectra obtained, via a multivariate calibration technique partial least square (PLS). Relative standard deviations (RSDs) for intraday repeatability and interday reproducibility were found to be in the range of 0.20–0.50% and 0.20–0.60%, respectively. Limit of detection (LOD) was achieved up to 15ngmL−1. Applicability of the method was tested with an unknown real sample obtained in an international official proficiency test (OPT).
Keywords: Chemical warfare agents; Liquid–liquid–solid phase microextraction; Infrared; Organophosphonates
Emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography by Behnam Ebrahimpour; Yadollah Yamini; Ali Esrafili (pp. 79-85).
A new on-line emulsification liquid phase microextraction coupled to high performance liquid chromatography is introduced based on a novel idea for the separation of dispersed organic phase from aqueous phase.Display Omitted► A new on-line emulsification liquid phase microextraction coupled HPLC is introduced. ► The dispersed organic solvent was separated from water sample using in-line filter. ► Filter was located in injection position and the analytes were transferred to HPLC. ► It was applied for extraction and determination of trace amounts of some parabens. ► PFs and LODs were obtained in the ranges of 289–595 and 0.05–0.2μgL−1.An emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography (HPLC) is introduced based on a novel idea for the separation of dispersed organic phase from aqueous phase. In this method, the dispersed organic extraction phase was filtered using an in-line filter and it was separated from the water sample. The new approach is simple and, in addition to improving some limitations of the conventional emulsification liquid phase microextraction, eliminates the need for centrifugation in the phase separation step.To demonstrate the applicability of the method, it was applied for the extraction and determination of trace amounts of selected parabens as model analytes. In this procedure, 30μL of 1-octanol was injected slowly into 10mL of the aqueous sample inside the ultrasonic water bath. Then, the emulsion formed was passed through the in-line filter located in the loop of the HPLC valve and the organic extraction phase was separated and it was retained in the filter. By changing the position of the valve, the filter was located in the mobile phase pass and the retained organic phase was eluted and transferred to the separation column. The effects of some important parameters such as types of extraction solvent and its volume, ionic strength, and ultrasonication time on extraction efficiency were investigated and optimized. Under optimal conditions, preconcentration factors and limits of detection for the compounds studied were obtained in the ranges of 289–595 and 0.05–0.2μgL−1, respectively. Finally, the method was successfully applied to determine selected parabens in some water and cosmetic samples.
Keywords: On-line microextraction; Emulsification liquid phase microextraction; Emulsion filtration; High performance liquid chromatography
New needle packed with polydimethylsiloxane having a micro-bore tunnel for headspace in-needle microextraction of aroma components of citrus oils by Hyun-Hwa Son; Sunyoung Bae; Dong-Sun Lee (pp. 86-93).
Display Omitted► We demonstrate the first in-needle microextraction using a needle packed polydimethylsiloxane having a micro-bore tunnel. ► This new method was theoretically and experimentally evaluated. ► The extraction parameters have been optimized along with the validation of method performance. ► It was successfully applied for the analysis of aroma components emitted from citrus essential oils.A novel in-needle microextraction (INME) for headspace sampling evaluated in this study has significantly higher extraction speed and the practical merits of a durable stainless steel needle to overcome some exposed fiber related drawbacks. A prototype stainless steel needle (Hamilton 90022, 22gauge bevel tip, 51mm length) packed with polydimethylsiloxane (PDMS, 0.413mm O.D., 10mm length) having a micro-bore (200μm I.D.) tunnel was prepared as a new INME device. This needle with a barrel and a plunger is then inserted and exposed into the headspace over the sample. Headspace sampling can be speeded up by an automatic reciprocating pump. The extraction parameters have been optimized along with the validation of method performance. The methodology has been applied for the analysis of volatile aroma active components emitted from eight kinds of citrus essential oils by GC-FID or GC/MS. The proposed method showed excellent linearity, reproducibility, and low detection limit. This solventless technique is simple to operate, inexpensive to fabricate, and provides a facile means for collecting and introducing volatile aroma active components of essential oils.
Keywords: In-needle microextraction; Polydimethylsiloxane; Micro-bore tunnel; Citrus essential oils; Aroma components; GC/MS
A method to detect metal–drug complexes and their interactions with pathogenic bacteria via graphene nanosheet assist laser desorption/ionization mass spectrometry and biosensors by Hani Nasser Abdelhamid; Hui-Fen Wu (pp. 94-104).
Display Omitted► Probe transition metals-complexes based on noncovalent functionalized graphene for MALDI-MS. ► Study interaction of transition metals complexes with pathogenic bacteria. ► Propose a new biosensor for two pathogenic bacteria.A new method was proposed to probe the interactions between transition metals of Fe(II), Fe(III), Cu(II) with a non steroidal anti-inflammatory drug (NSAID), flufenamic acid (FF) using graphene as a matrix for Graphene assisted laser desorption ionization mass spectrometry (GALDI-MS). Metal–drug complexation was confirmed via UV absorption spectroscopy, fluorescence spectroscopy, pH meter, and change in solution conductivity. The optimal molar ratios for these complexation interactions are stoichiometry 1:2 in both Cu(II) and Fe(II) complexes, and 1:3 in Fe(III) complexes at physiological pH (7.4). Metal complexation of the drug could enhance fluorescence for 20 fold which is due to the charge transfer reaction or increase rigidity of the drug. The main interaction between graphene and flufenamic acid is the П–П interaction which allows us to probe the metal–drug complexation. The GALDI-MS could sensitively detect the drug at m/z 281.0Da (protonated molecule) with detection limit 2.5pmol (1.0μM) and complexation at m/z 661.0, 654.0 and 933.0Da corresponding to [Cu(II)(FF)2(H2O)2+H]+, [Fe(II)(FF)2(H2O)2+H]+ and [Fe(III) (FF)3(H2O)2+H]+, respectively (with limit of detection (LOD) 2.0pmol (10.0μM). Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) spectra show change in the protein profile of intact pathogenic bacteria ( Pseudomonas aeroginosa, Staphylococcus aureus). The change in the ionization ability (mainly proton affinity) of pathogenic bacteria may be due to the interactions between the bacteria with the drug (or its complexes). Shielding carboxylic group by metals and increase the hydrophilicity could enhance the biocompatibility of complexes toward the pathogenic bacteria which can be used as biosensors with high sensitivity and lowest detectable concentrations are in the range of 3.3×103–3.9×104cfumL−1 with large linear dynamic range.
Keywords: Graphene; NSAID; Co-ordination chemistry; MALDI-MS; Pathogenic bacteria; Fluorescence; BiosensorAbbreviations; MALD-MS; matrix assisted laser desorption ionization mass spectrometry; GALDI-MS; graphene assisted laser desorption ionization mass spectrometry; GONPs; graphene oxide nanoparticles; LDI-MS; laser desorption ionization mass spectrometry; ESI-MS; electrospray ionization mass spectrometry; FF; flufenamic acid; SA; sinapinic acid, 3-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-enoic acid(IUPAC name); 2,5-DHB; 2,5-dihydroxybenzoic acid; NSAIDs; non-steroidal anti-inflammatory drugs
A set of triple-resonance nuclear magnetic resonance experiments for structural characterization of organophosphorus compounds in mixture samples by Harri Koskela (pp. 105-111).
Display Omitted► New1H,13C,31P triple-resonance NMR pulse experiments. ► Analysis of organophosphorus (OP) compounds in complex matrix. ► Selective extraction of1H,31P, and13C chemical shifts and connectivities. ► More precise NMR identification of OP nerve agents and their degradation products.The1H,13C correlation NMR spectroscopy utilizes JCH couplings in molecules, and provides important structural information from small organic molecules in the form of carbon chemical shifts and carbon-proton connectivities. The full potential of the1H,13C correlation NMR spectroscopy has not been realized in the Chemical Weapons Convention (CWC) related verification analyses due to the sample matrix, which usually contains a high amount of non-related compounds obscuring the correlations of the relevant compounds. Here, the results of the application of1H,13C,31P triple-resonance NMR spectroscopy in characterization of OP compounds related to the CWC are presented. With a set of two-dimensional triple-resonance experiments the JHP, JCH and JPC couplings are utilized to map the connectivities of the atoms in OP compounds and to extract the carbon chemical shift information. With the use of the proposed pulse sequences the correlations from the OP compounds can be recorded without significant artifacts from the non-OP compound impurities in the sample. Further selectivity of the observed correlations is achieved with the application of phosphorus band-selective pulse in the pulse sequences to assist the analysis of multiple OP compounds in mixture samples. The use of the triple-resonance experiments in the analysis of a complex sample is shown with a test mixture containing typical scheduled OP compounds, including the characteristic degradation products of nerve agents sarin, soman, and VX. The viability of the approach in verification analysis is demonstrated in the analysis of the 30th OPCW Proficiency Test sample.
Keywords: Two-dimensional NMR spectroscopy; 1; H,; 13; C,; 31; P triple-resonance; Band-selective; Chemical Weapons Convention; Mixture sample analysis; Organophosphorus compounds
Rapid, on-site identification of explosives in nanoliter droplets using a UV reflected fiber optic sensor by Xin Li; Qiang Li; Hong Zhou; Hongxia Hao; Tongzhou Wang; Songmin Zhao; Ying Lu; Guoliang Huang (pp. 112-118).
Display Omitted► We design a portable system for the on-site detection of explosives. ► The system is capable of rapid, costless detection with low sample consumption. ► We develop a novel algorithm capable of identifying explosives. ► Seven explosives and a PETN–RDX mixture are detected and identified. ► Real world samples are identified and the results are validated by LC/MS/MS.A portable UV (190–400nm) spectrophotometric based reflected fiber optic sensor system is presented for the on-site detection and identification of explosives. A reflected fiber optic sensor for explosives analysis was developed, with low sample consumption (20–100nL) and a wide concentration quantification range (1.1–250mgL−1). Seven common explosives [pentaerythritol tetranitrate (PETN), trinitrophenylmethylnitramine (CE), trinitrotoluene (TNT), dinitrotoluene (DNT), picric acid (PA), cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetrinitramine (RDX)] and a PETN–RDX mixture (to simulate the Semtex used in many terrorist bombings) were quantitatively analyzed and identified by the proposed system in less than 3s per test, with limits of detection (LOD) of 0.3mgL−1. Due to chemical interference problems in the UV wavelengths range, a novel feature matching algorithm (FMA) was proposed for explosive identification, which was proved to have higher specificity and better anti-interference ability. Real post-blast debris samples were analyzed by the proposed method, and the results were validated against an LC/MS/MS method. The rapid, cost-effective detection with low sample consumption and wide applicability achieved by this system is highly suitable for homeland security on-site applications, such as rapid sample screening in post-blast debris.
Keywords: Explosive; On-site; Fiber optic sensor; Ultraviolet spectrophotometry
A highly sensitive and selective immunoassay for the detection of tetrabromobisphenol A in soil and sediment by Ting Xu; Jia Wang; Shang-zhong Liu; Cong Lü; Weilin L. Shelver; Qing X. Li; Ji Li (pp. 119-127).
Display Omitted► The developed ELISA is highly sensitive and selective to TBBPA. ► Accuracy of this ELISA for TBBPA in environmental matrices were reasonable. ► TBBPA levels found in environmental samples showed variation. ► ELISA for TBBPA in real samples correlated well with LC–MS/MS method.Tetrabromobisphenol A is the most widely used brominated flame retardant. A sensitive and selective enzyme-linked immunosorbent assay (ELISA) for the detection of tetrabromobisphenol A was developed. The limit of detection and the inhibition half-maximum concentration of tetrabromobisphenol A in phosphate buffered saline with 10% methanol were 0.05 and 0.87ngmL−1, respectively. Cross-reactivity values of the ELISA with a set of important brominated flame retardants including tetrabromobisphenol A-bis(2,3-dibromopropylether), 2,2′,6,6′-tetrabromobisphenol A diallyl ether, hexabromocyclododecane, 1,2-bis(pentabromodiphenyl) ethane, 1,2-bis(2,4,6 tribromophenoxy) ethane, bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate, and polybrominated diphenyl ethers were <0.05%. Concentrations of tetrabromobisphenol A determined by ELISA in the soils from farmlands, the soils from an e-waste recycling site, and the sediments of a canal were in the range of non-detectable–5.6ngg−1, 26–104ngg−1 and 0.3–22ngg−1dw, respectively, indicating the ubiquitous pollution of tetrabromobisphenol A. The results of this assay for 16 real world samples agreed well with those of the liquid chromatography–tandem mass spectrometry method, indicating this ELISA is suitable for screening of tetrabromobisphenol A in environmental matrices.
Keywords: Tetrabromobisphenol A; Enzyme-linked immunosorbent assay; Environmental pollution; Soil; Sediment
A gel-based visual immunoassay for non-instrumental detection of chloramphenicol in food samples by Meng Yuan; Wei Sheng; Yan Zhang; Junping Wang; Yijin Yang; Shuguang Zhang; Irina Yu. Goryacheva; Shuo Wang (pp. 128-134).
A gel-based non-instrumental immuno-affinity assay was developed for the rapid screening of chloramphenicol (CAP) in food samples with the limit of detection (LOD) of 1μgL−1. The immuno-affinity test column (IATC) consisted of a test layer containing anti-CAP antibody coupled gel, and a control layer with anti-HRP antibody coupled gel. Based on the direct competitive immuno-reaction and the horseradish peroxidase enzymatic reaction, the test results could be evaluated visually. Basically, blue color development represented the negative results, while the absence of color development represented the positive results. In this study, CAP spiked samples of raw milk, pasteurized milk, UHT milk, skimmed milk powder, acacia honey, date honey, fish and shrimp were tested. Little or none sample pretreatment was required for this assay. The whole procedure was completed within 10min. In conclusion, the gel-based immuno-affinity test is a simple, rapid, and promising on-site screening method for CAP residues in food samples, with no instrumental requirement.
Keywords: Chloramphenicol; Immunoassay; Immuno-affinity test column; Non-instrumental; Visual detection
A fluorescence reagent for the highly selective recognition and separation of lead ion (II) from aqueous solutions by Li-Jun Ma; Yuhua Yan; Liping Chen; Weiguang Cao; Hongwei Li; Liting Yang; Yuqing Wu (pp. 135-139).
A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7μgL−1) and specific selectivity for Pb2+ over other metal ions examined in aqueous solutions. It could also be used to remove Pb2+ from aqueous solutions by filtering the insoluble1–Pb2+ complex with sufficient reversibility.Display Omitted► A new fluorescence reagent (1) for Pb2+ was synthesized. ► The fluorescence sensor shows a low detection limit (20.7μgL−1) for Pb2+. ► The sensor exhibits a specific selectivity for Pb2+ in aqueous solution. ► The reagent can remove Pb2+ with a good reversibility from aqueous solution.A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7μgL−1) and specific selectivity for Pb2+ over other metal ions examined in aqueous solutions. It could also be used to remove Pb2+ from aqueous solutions by filtering the insoluble1–Pb2+ complex with sufficient reversibility.
Keywords: Fluorescence reagent; Pb; 2+; High sensitivity; Selective removal; High selectivity
Palladium@gold bimetallic nanostructures as peroxidase mimic for development of sensitive fluoroimmunoassay by Yogesh Nangia; Bipul Kumar; Jyotsna Kaushal; C. Raman Suri (pp. 140-145).
Display Omitted► Peroxidase like property of palladium–gold bimetallic nanostructures has been demonstrated. ► Pd@AuNS based fluoro-immunoassay using fluorogenic peroxidase substrate is developed. ► High sensitivity for fluoro-immunoassay (IC50∼1.55ngmL−1) for bensulfuron detection. ► Pd@AuNS can be readily used for the detection of H2O2 for various applications.In this paper, gold nanoparticles coated with palladium dots (Pd@Au) bimetallic nanostructures have been reported to have a peroxidase like activity which is not found in their monometallic counterparts. Based on this finding, we have developed an immunoassay in which antibody-modified Pd@Au nanostructure catalyzes the dimerization of a fluorogenic substrate for peroxidase, 3-(4-dihydroxy phenyl) propionic acid (HPPA), to generate high fluorescence signal. Specific antibodies against bensulfuron-methyl were generated by using a well characterized bensulfuron–protein conjugate as an immunogen, and the assay was performed in a competitive immunoassay format where Pd@Au nanostructure was bound to secondary antibody to show the peroxidase like activity. The developed immunoassay exhibited an excellent sensitivity showing a dynamic response range from 0.001 to 100ngmL−1 for herbicide bensulfuron-methyl with a detection limit of 0.01ngmL−1 ( n=3). The newly synthesized bimetallic nanostructure shows the advantages of low cost, easy synthesis and tunable catalytic activity, making it a promising substitution of enzyme peroxidase in different applications.
Keywords: Bimetallic nanoparticles; Enzyme mimics; Fluoro-immunoassay; Bensulfuron
Multiplex detection platform for tumor markers and glucose in serum based on a microfluidic microparticle array by Qingdi Zhu; Dieter Trau (pp. 146-154).
Display Omitted► Microparticle array on gel microstructures which can sustain microfluidic flow. ► Quantitative microfluidic microbead-based immunoassay for serum tumor marker. ► Quantitative microfluidic microparticle-based enzymatic assay for serum glucose. ► Multiplexed immunoassay for tumor markers with spatially encoded microbead array. ► Simultaneous immune- and enzymatic assays with microfluidic microparticle arrays.We present a multiplex detection platform based on a microfluidic microparticle array to detect proteins and glucose in serum simultaneously. Multiplex detection of proteins and glucose was performed using biofunctionalized microparticles arrayed on gel-based microstructures integrated in microfluidics. The microparticles immobilized on these microstructures showed high stability under microfluidic flow conditions. With arrays of antibody-coated microbeads, microfluidic quantitative immunoassays for two protein tumor markers, human chorionic gonadotropin (hCG) and prostate specific antigen (PSA) were performed in serum samples with detection limits bellow the cut-off values for cancer diagnosis. Parallel to the immunoassays, quantitative enzymatic assays for glucose in the physiological concentration range were performed. Multiplex detection was achieved by using a spatially encoded microarray. By patterning antibody-coated microbeads and enzyme-containing microparticles on a novel mixed structure array, we successfully demonstrated simultaneous immunoassays (binding based assay) for proteins and an enzymatic assay (reaction kinetic based assay) for glucose. Our microparticle arrays could be potentially used for the detection of multiple categories of biomolecules (proteins, small metabolites and DNA) for clinical diagnostics and other biological applications.
Keywords: Microparticle array; Multiplexing; Spatial encoding; Gel-based microstructures; Tumor markers; Glucose
Droplet-based microscale colorimetric biosensor for multiplexed DNA analysis via a graphene nanoprobe by Xia Xiang; Ming Luo; Liyang Shi; Xinghu Ji; Zhike He (pp. 155-160).
With a microvalve manipulate technique combined with droplet platform, a microscale fluorescence-based colorimetric sensor for multiplexed DNA analysis is developed via a graphene nanoprobe.Display Omitted► A quantitative detection for multiplexed DNA is first realized on droplet platform. ► The DNA detection is relied on a simple fluorescence-based colorimetric method. ► GO is served as a quencher for two different DNA fluorescent probes. ► This present work provides a rapid, sensitive, visual and convenient detection tool for droplet biosensor.The development of simple and inexpensive DNA detection strategy is very significant for droplet-based microfluidic system. Here, a droplet-based biosensor for multiplexed DNA analysis is developed with a common imaging device by using fluorescence-based colorimetric method and a graphene nanoprobe. With the aid of droplet manipulation technique, droplet size adjustment, droplet fusion and droplet trap are realized accurately and precisely. Due to the high quenching efficiency of graphene oxide (GO), in the absence of target DNAs, the droplet containing two single-stranded DNA probes and GO shows dark color, in which the DNA probes are labeled carboxy fluorescein (FAM) and 6-carboxy-X-rhodamine (ROX), respectively. The droplet changes from dark to bright color when the DNA probes form double helix with the specific target DNAs leading to the dyes far away from GO. This colorimetric droplet biosensor exhibits a quantitative capability for simultaneous detection of two different target DNAs with the detection limits of 9.46 and 9.67×10−8M, respectively. It is also demonstrated that this biosensor platform can become a promising detection tool in high throughput applications with low consumption of reagents. Moreover, the incorporation of graphene nanoprobe and droplet technique can drive the biosensor field one more step to some extent.
Keywords: Droplet; Biosensor; Fluorescence-based colorimetric method; Graphene oxide; DNA detection
Towards an integrated biosensor array for simultaneous and rapid multi-analysis of endocrine disrupting chemicals by Viviana Scognamiglio; Italo Pezzotti; Gianni Pezzotti; Juan Cano; Ivano Manfredonia; Katia Buonasera; Fabiana Arduini; Danila Moscone; Giuseppe Palleschi; Maria Teresa Giardi (pp. 161-170).
Display Omitted► A multitask biosensor for the detection of endocrine disrupting chemicals is proposed. ► The sensing system employ an array of biological recognition elements. ► Amperometric and optical transduction methods are provided in an integrated biosensor together with flow control systems. ► The biosensing device results in an integrated, automatic and portable system for environmental and agrifood application.In this paper we propose the construction and application of a portable multi-purpose biosensor array for the simultaneous detection of a wide range of endocrine disruptor chemicals (EDCs), based on the recognition operated by various enzymes and microorganisms. The developed biosensor combines both electrochemical and optical transduction systems, in order to increase the number of chemical species which can be monitored. Considering to the maximum residue level (MRL) of contaminants established by the European Commission, the biosensor system was able to detect most of the chemicals analysed with very high sensitivity. In particular, atrazine and diuron were detected with a limit of detection of 0.5nM, with an RSD% less than 5%; paraoxon and chlorpyrifos were revealed with a detection of 5μM and 4.5μM, respectively, with an RSD% less than 6%; catechol and bisphenol A were identified with a limit of detection of 1μM and 35μM respectively, with an RSD% less than 5%.
Keywords: Endocrine disrupting chemicals; Multi-array; Biosensor; Amperometric; Optical; Integrated biosensing system
An acyclic, dansyl based colorimetric and fluorescent chemosensor for Hg(II) via twisted intramolecular charge transfer (TICT) by Vairaperumal Tharmaraj; Kasi Pitchumani (pp. 171-175).
A highly selective, simple, acyclic, dansyl based bipodal on–off fluorescence chemosensor for Hg2+ ion is reported. The system exhibits visible color change from colorless to gray upon Hg2+ binding via TICT mechanism. Hg2+-ion detection limit (as low as 5.0×10−10molL−1) is reported. This system can also be applied in real samples.Display Omitted► A highly selective, simple, acyclic, dansyl based bipodal on–off fluorescence chemosensor for Hg2+ ion is reported. ► The system exhibits visible color change from colorless to gray upon Hg2+ binding via TICT mechanism. ► Hg2+-ion detection limit (as low as 5.0×10−10molL−1) is reported. ► This system can also be applied in real samples.An efficient fluorescent chemosensor for Hg2+ ion, based on 5-(dimethylamino)- N-(2-mercaptophenyl)naphthalene-1-sulfonamide, has been developed. It exhibits Hg2+-selective on–off fluorescence quenching behavior via twisted intramolecular charge transfer (TICT) mechanism, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The system exhibits visible color change from colorless to gray upon Hg2+ binding with very high selectivity and sensitivity (as low as 5.0×10−10molL−1) over other metal ions such as K+, Na+, Ag+, Mn2+, Ca2+, Ba2+, Fe2+, Zn2+, Pb2+, Cu2+, Sn2+, Cd2+, Ni2+ and Co2+. The present sensing system is also successfully applied for the detection of Hg2+ ion in real samples.
Keywords: Hg; 2+; sensing; Colorimetric and fluorescent chemosensor; Twisted intramolecular charge transfer (TICT); Real water samples; Time dependent density functional theory calculations
Analysis of cytokinin nucleotides by capillary zone electrophoresis with diode array and mass spectrometric detection in a recombinant enzyme in vitro reaction by Tibor Béres; Markéta Gemrotová; Petr Tarkowski; Markus Ganzera; Vítězslav Maier; David Friedecký; Marco A. Dessoy; Ludger A. Wessjohann; Lukáš Spíchal; Miroslav Strnad; Karel Doležal (pp. 176-181).
Display Omitted► We describe a capillary electrophoresis based enzymatic assay. ► Cytokinin mono-, di- and triphosphates were separated by CE for the first time. ► The products of enzymatic reactions were unambigously identified by HPLC-QqTOF-MS. ► Undesirable changes in substrates/products were observed.A capillary zone electrophoresis (CZE) method for separation of adenosine and N6-isopentenyladenosine (cytokinin) nucleotides was developed, optimized and validated. Aqueous solutions of several amino acids were evaluated as the background electrolyte constituents. Separation of six nucleotides in less than 20min with high theoretical plate number (up to 400000 for isopentenyladenosine triphosphate) was achieved using a 100mM sarcosine/ammonia buffer at pH 10.0. The detection limits of the CZE-UV method are in the low micromolar range (0.69–1.27μmolL−1). Good repeatability of migration times (within 1.3%), peak areas (within 1.8%) and linearity ( R2>0.999) was achieved over the concentration range 5–1000μmolL−1. The method was used to assay the activity of the recombinant Arabidopsis thaliana isopentenyltransferase 1 ( AtIPT1). Baseline separation of isopentenylated nucleotides by CE–ESI-MS using a volatile buffer (30mM ammonium formate; pH 10.0) was accomplished. The identities of the reaction products – isopentenyladenosine di- and triphosphate were confirmed by HPLC-QqTOF-MS. Dephosphorylation of ATP was observed as a parallel reaction.
Keywords: Cytokinin nucleotides; Capillary electrophoresis; Isopentenyltransferase; Cytokinin biosynthesis
Effectiveness of in-needle extraction device for liquid samples by Monika Pietrzyńska; Adam Voelkel; Károly Héberger; Katarzyna Bielicka-Daszkiewicz; Mariusz Kaczmarek (pp. 182-188).
Display Omitted► Modeling of functioning for in-needle extraction device. ► Selection of working conditions for prediction of liquid flow velocity. ► New P IN parameter indicates the efficient working conditions.In this work in-needle technique as the method for liquid samples preparation which faces with the problem of high flow resistance produced by a sorbent layer is considered. The influence of parameters (needle size, sorbent particle size and length of sorbent layer) of in-needle device on the flow rate was examined. Acceptable sampling conditions were selected on the basis of experiments and their chemometric evaluation. Darcy law was used to describe flow velocity through sorbent in the needle. Kozeny–Carman model and Brinkman model led to results significantly different from those obtained experimentally. Baaren model gave the most realistic results. Diameter of grain, porosity and a constant termed C were taken into account in this model. Incorporation of an additional parameter – “constant C” provides the completion of the model and allows predicting effectively the permeability of the extraction system. The so-called “constant C” is not constant but characteristic for a given system.The range for geometrical characteristics of the sorbent has been determined, where the extraction system works properly. To estimate suitability of a given extraction system, a new parameter P IN expressing the geometry of the system was proposed. The usefulness of the range of P IN parameter was confirmed experimentally. This tool might be used in designing and preparation of a number of in-needle devices having similar ability of liquid transportation.
Keywords: Solid phase extraction; Liquid transportation; Permeability; Chemometrics; Multiple linear regression; ANOVA