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Analytica Chimica Acta (v.764, #)
Determination of gadolinium-based MRI contrast agents in biological and environmental samples: A review by Lena Telgmann; Michael Sperling; Uwe Karst (pp. 1-16).
Display Omitted► All major methods for the analysis of Gd-based MRI contrast agents are discussed. ► Biological and environmental samples are covered. ► Pharmacokinetics and species transformation can be investigated. ► The figures of merit as limit of detection and analysis time are described.The development of analytical methods and strategies to determine gadolinium and its complexes in biological and environmental matrices is evaluated in this review.Gadolinium (Gd) chelates are employed as contrast agents for magnetic resonance imaging (MRI) since the 1980s. In general they were considered as safe and well-tolerated, when in 2006, the disease nephrogenic systemic fibrosis (NSF) was connected to the administration of MRI contrast agents based on Gd. Pathogenesis and etiology of NSF are yet unclear and called for the development of several analytical methods to obtain elucidation in this field. Determination of Gd complex stability in vitro and in vivo, as well as the quantification of Gd in body fluids like blood and urine was carried out. Separation of the Gd chelates was achieved with high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). For detection, various methods were employed, including UV–vis absorbance and fluorescence spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS).A second challenge for analysts was the discovery of high concentrations of anthropogenic Gd in surface waters draining populated areas. The source could soon be determined to be the increasing administration of Gd complexes during MRI examinations. Identification and quantification of the contrast agents was carried out in various surface and groundwater samples to determine the behavior and fate of the Gd chelates in the environment. The improvement of limits of detection (LOD) and limits of quantification (LOQ) was and still is the goal of past and ongoing projects.
Keywords: MRI contrast agents; Biomedical analysis; Environmental analysis; Separation techniques; Mass spectrometry; Hyphenated techniques; Speciation analysis
Near infrared spectroscopy and multivariate analysis to evaluate wheat flour doughs leavening and bread properties by Mario Li Vigni; Marina Cocchi (pp. 17-23).
Display Omitted► Dough leavening is studied by means of multi-way methods and NIR spectroscopy. ► Trends of variability of the NIR signal with time (leavening profiles) are obtained. ► Bread properties (e.g. volume) can be predicted from its behavior during leavening. ► Model interpretability is improved through nested mode biplots of PARAFAC loadings.A mixture design of experiment approach was followed to explore formulation effects on the technological properties of wheat flours optimized for industrial bread-making purposes. Ten different flour mixtures were investigated by means of near infrared spectroscopy (NIRS) to obtain information on flour performance in a critical phase such as dough leavening. For each mixture, a laboratory-scale bread making experiment was carried out according to a standardized recipe and the leavening phase of each dough sample was monitored by means of NIRS at different times. Parallel factor analysis (PARAFAC) was used to highlight the existence of differences among the mixtures on the basis of NIR spectrum variability with respect to the leavening time. Additionally, the relationship among the 3-way NIR dataset and some parameters measured on the baked bread loaves (dimensions, volume, weight) was investigated by means of the n-way extension of partial least squares regression (nPLS), in order to evaluate product properties from its leavening step and mixture formulation. The results give better insight on the relationships among wheat flour formulation and its performance in the leavening phase and as far as some properties of the final product are concerned, thus offering a way to monitor the leavening phase and give information on its influence on the final product properties.
Keywords: Three-way analysis; Near infrared spectroscopy; Industrial bread-making
Mid-infrared (MIR) metabolic fingerprinting of amniotic fluid: A possible avenue for early diagnosis of prenatal disorders? by Gonçalo Graça; Ana Sofia Moreira; Ana João V. Correia; Brian J. Goodfellow; António S. Barros; Iola F. Duarte; Isabel M. Carreira; Eulália Galhano; Cristina Pita; Maria do Céu Almeida; Ana M. Gil (pp. 24-31).
Display Omitted► First profiling study of amniotic fluid by MIR and multivariate analysis. ► MIR/MIR and MIR/NMR correlation for IR assignment of disease-related metabolites. ► MIR profiling changes related to fetal malformations and preterm delivery. ► Putative interpretation of MIR signatures of fetal malformations/preterm delivery.This work describes a mid-infrared (MIR) metabolic profiling study of 2nd trimester amniotic fluid in relation to selected prenatal disorders, with results focusing on fetal malformations (FM), preterm delivery (PTD) and premature rupture of membranes (PROM), the latter two conditions occurring later in pregnancy. Partial least squares-discriminant analysis (PLS-DA) models were obtained for FM and pre-PTD subject groups, supported by Monte Carlo Cross Validation (MCCV), and identified specific MIR profile changes. For pre-PROM subjects, minor changes were noted. MIR interpretation was assisted by intra- (MIR/MIR) and inter- (MIR/NMR) domain statistical correlation analysis, the results unveiling possible biomarker MIR signatures for FM and pre-PTD subjects. Biofluid MIR metabolic profiling holds enticing possibilities as a low cost, easy to use, rapid method and the results presented have shown its sensitivity to clinically diagnosed conditions such as FM, and to the pre-clinical stages of PTD. Specific improvement needs are discussed, namely regarding sample numbers and experimental reproducibility.
Keywords: Amniotic fluid; Prenatal diagnostics; Preterm; Fetal malformation; Mid-infrared spectroscopy; Multivariate analysis; Statistical correlation spectroscopy; Nuclear magnetic resonance spectroscopy
Values below detection limit in compositional chemical data by J. Palarea-Albaladejo; J.A. Martín-Fernández (pp. 32-43).
Display Omitted► Less-than replacement methods for compositional chemical data. ► New model-based univariate multiplicative replacement method. ► Evaluation of competing methods performance. ► Computer code implementing the methods provided.Samples representing part of a whole, usually called compositional data in statistics, are commonplace in analytical chemistry—say chemical data in percentage, ppm, or μgg−1. Their distinctive feature is that there is an inherent relationship between all the analytes constituting a chemical sample as they only convey relative information. Some compositional data analysis principles and the log-ratio based methodology are outlined here in practical terms. Besides, one often finds that some analytes are not present in sufficient concentration in a sample to allow the measuring instruments to effectively detect them. These non-detects are usually labelled as “less-thans) in the data set, indicating that the values are below known detection limits. Many data analysis techniques require complete data sets. Thus, there is a need of sensible replacement strategies for less-thans. The peculiar nature of compositional data determines any data analysis and demands for a specialised treatment of less-thans that, unfortunately, is not usually covered in chemometrics. Some well-founded statistical methods are revisited in this paper aiming to prevent practitioners from relying on popular but untrustworthy approaches. A new proposal to estimate less-thans combining a log-normal probability model and a multiplicative modification of the samples is also introduced. Their performance is illustrated and compared on a real data set, and guidelines are provided for practitioners. Matlab and R code implementing the methods are made available for the reader.
Keywords: Compositional data; Detection limits; Expectation-Maximisation algorithm; Log-normal distribution; Log-ratio approach; Imputation methods
Cytotoxicity assessment based on the AUC50 using multi-concentration time-dependent cellular response curves by Tianhong Pan; Biao Huang; Weiping Zhang; Stephan Gabos; Dorothy Yu Huang; Vignesh Devendran (pp. 44-52).
Display Omitted► Dose- and time-dependent cellular responses are used to evaluate the cytotoxicity. ► The CI can reflect the cell number, cell viability and morphological change, etc. ► AUC is more relevant to the intensity of the cell treatment. ► AUC50 can be used for cytotoxicity assessment. ► AUC50 combined with RTCA HT assay can achieve a high-throughput screening.Although many indices have been developed to quantify chemical toxicity, substantial shortcoming is inherent in most of them, such as observation time dependence, insufficient robustness, and no comparison with the negative control. To assess the extent of exposure of the tested substance, a cytotoxicity assay named AUC50 was developed to describe the time and concentration-dependent cellular responses. By monitoring the dynamic cytotoxicity response profile of living cells via the xCELLigence real-time cell analysis high-throughput (RTCA HT) system, changes in cell number (named cell index, CI) were recorded and analyzed subsequently. A normalized cell index ( NCI) is introduced to reduce the influence of inter-experimental variations. The log-phase of cellular growth is considered, which alleviates the cell's spontaneous effect. The area between the control line and the assessed time-dependent cellular response curve (TCRC) of the tested substance was calculated, and the corresponding exponential kill model (concentration–response curve) was developed along with exploiting the concept of AUC50. The validation of the proposed method is demonstrated by exposing HepG2 cell line to seven chemical compounds. Our findings suggested that the proposed AUC-based toxicity assay could be an alternative to the traditional single time-point assay, and it has potential to become routine settings for evaluating the cell-based in vitro assay. Furthermore, the AUC50 combined with RTCA HT assay can be used to achieve a high-throughput screening that conventional cellular assay cannot achieve.
Keywords: Time-dependent cellular response curve; Area under the control line; In vitro; cytotoxicity assay; High-throughput screening; Repeatability
Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina by Yuanyuan Zhang; Tian Gan; Chidan Wan; Kangbing Wu (pp. 53-58).
Display Omitted► A facile way to tune morphology and sensing properties of alumina was developed. ► Oxidation activities of amaranth on alumina surface were morphology-dependent. ► Alumina microfibers were more active and greatly increased the signal of amaranth. ► Sensitive, rapid, selective and accurate method was developed for amaranth detection.Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6h to 24h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150nM, and the detection limit was 0.75nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.
Keywords: Amaranth; Electrochemical determination; Morphology tailoring; Alumina microfiber; Signal enhancement
Sensitive detection of human breast cancer cells based on aptamer–cell–aptamer sandwich architecture by Xiaoli Zhu; Jinghua Yang; Min Liu; Yao Wu; Zhongming Shen; Genxi Li (pp. 59-63).
Display Omitted► An electrochemical biosensor for the detection of MCF-7 cells was fabricated. ► An aptamer–cell–aptamer sandwich architecture was constructed on an electrode. ► Dual-recognition and enzyme-linked amplification were well integrated. ► Favorable sensitivity and selectivity can be achieved.Breast cancer is one of the most critical threats to the health of women, and the development of new methods for early diagnosis is urgently required, so this paper reports a method to detect Michigan cancer foundation-7 (MCF-7) human breast cancer cells with considerable sensitivity and selectivity by using electrochemical technique. In this method, a mucin 1 (MUC1)-binding aptamer is adopted to recognize MCF-7 human breast cancer cells, while enzyme labeling is employed to produce amplified catalytic signals. The molecular recognition and the signal amplification are elaborately integrated by fabricating an aptamer–cell–aptamer sandwich architecture on an electrode surface, thus a biosensor for the detection of MCF-7 is fabricated based on the architecture. The detection range can be from 100 to 1×107cells, and the detection limit can be as low as 100 cells. The method is also cost-effective and conveniently operated, implying potential help for the development of early diagnosis of breast cancer.
Keywords: Breast cancer; Michigan cancer foundation-7; Aptamer; Mucin 1; Electrochemistry; Biosensors
Iodine and creatinine testing in urine dried on filter paper by Theodore T. Zava; Sonia Kapur; David T. Zava (pp. 64-69).
Display Omitted► Dried urine iodine and creatinine extract quantitatively correlates well with liquid urine. ► Filter paper strips can be easily shipped and stored. ► Urine iodine and creatinine are stable at ambient temperature when dried on filter paper. ► Dried urine iodine and creatinine are run using a 96-well format.Iodine deficiency is a world-wide health problem. A simple, convenient, and inexpensive method to monitor urine iodine levels would have enormous benefit in determining an individual's recent iodine intake or in identifying populations at risk for iodine deficiency or excess. Current methods used to monitor iodine levels require collection of a large volume of urine and its transport to a testing laboratory, both of which are inconvenient and impractical in parts of the world lacking refrigerated storage and transportation. To circumvent these limitations we developed and validated methods to collect and measure iodine and creatinine in urine dried on filter paper strips. We tested liquid urine and liquid-extracted dried urine for iodine and creatinine in a 96-well format using Sandell–Kolthoff and Jaffe reactions, respectively. Our modified dried urine iodine and creatinine assays correlated well with established liquid urine methods (iodine: R2=0.9483; creatinine: R2=0.9782). Results demonstrate that the dried urine iodine and creatinine assays are ideal for testing the iodine status of individuals and for wide scale application in iodine screening programs.
Keywords: Iodine; Creatinine; Dried urine; Filter paper; Deficiency; Microplate
Development of a generic assay for the determination of total trihydroxybenzoate derivatives based on gold-luminol chemiluminescence by Dimosthenis L. Giokas; Dionysios C. Christodouleas; Ioanna Vlachou; Athanasios G. Vlessidis; Antony C. Calokerinos (pp. 70-77).
Display Omitted► Gold is used as an alternative oxidant to luminol under mild conditions. ► Trihydroxybenzoates are selectively determined in complex mixtures. ► The method is straightforward without any interim steps.A selective assay for the determination of one of the most important class of phenolic compounds, namely trihydroxybenzoates (monomeric and polymeric compounds having at least one gallate moiety) based on their enhancing effect on the chemiluminogenic reaction between gold ions and luminol is described for the first time. In the presence of trihydroxybenzoate derivatives, the light emission generated when alkaline luminol is oxidized by gold ions is amplified several orders of magnitude compared to other common phenolic compounds which exhibit minor reactivity or no reactivity at all (e.g. hydroxycinnamates, flavonols, benzenediols). Based on this property, the experimental conditions were optimized in order to enable the determination of total trihydroxybenzoates in complex mixtures without resorting to separation techniques. The method was applied to samples of different composition (teas, herbal infusions and wines) with satisfactory analytical features yielding detection limits at the 10−7molL−1 level, intra-day precision of 3.1%, inter-day precision less than 10% and recoveries between 88.7 and 97.6%. The strengths and weaknesses of the method were identified and discussed in relation to its application in real samples.
Keywords: Gallic acid derivatives; Trihydroxybenzoates; Gold; Luminol; Flow injection analysis
Visual detection of arginine based on the unique guanidino group-induced aggregation of gold nanoparticles by Wendan Pu; Huawen Zhao; Chengzhi Huang; Liping Wu; Dan Xu (pp. 78-83).
Schematic diagram of visual detection of arginine based on the citrate-capped AuNPs aggregation.Display Omitted► A simple, fast and novel colorimetric method for arginine detection was developed. ► This method showed high sensitivity and selectivity. ► As low as 0.4μM arginine could be easily detected by the naked eye. ► This method was successfully used to detect arginine in real samples.A simple, cost-effective and rapid method for visual detection of arginine based on the citrate-capped gold nanoparticles (AuNPs) aggregation has been developed in this paper. Arginine is the only amino acid with guanidino group, and has the highest isoelectric point (pI) at about 10.8. At pH 9.62, negatively charged citrate-capped AuNPs are well dispersed because of strong electrostatic repulsion. However, positively charged arginine (pHσ/slope) of 16nM. Particularly, as low as 0.4μM arginine can be easily detected by the naked eye without using any complicated or expensive instruments. Furthermore, this method can provide satisfactory results for the determination of arginine in arginine injection and compound amino acid injection samples.
Keywords: Visual detection; Arginine; Gold nanoparticles; Guanidino group; Isoelectric point
A phage-displayed chicken single-chain antibody fused to alkaline phosphatase detects Fusarium pathogens and their presence in cereal grains by Zu-Quan Hu; He-Ping Li; Jing-Bo Zhang; Tao Huang; Jin-Long Liu; Sheng Xue; Ai-Bo Wu; Yu-Cai Liao (pp. 84-92).
A phage-displayed chicken scFv antibody, FvSG7, binds on the surface antigen of conidiospores and the mycelia of F. verticillioides. Its fusion with alkaline phosphatase (AP) through a 218 linker displayed a 4-fold higher affinity compared with the parent scFv antibody and efficiently detected toxigenic Fusarium pathogens in cereal grains.Display Omitted► Generation of a highly reactive scFv antibody against F. verticillioides. ► Localization of the antibody binding to the surface target of F. verticillioides. ► Expression of the antibody–alkaline phosphatase (AP) fusion linked by a 218 linker. ► The antibody–AP fusion has a higher affinity than the parental antibody. ► The antibody–AP fusion detects toxigenic Fusarium pathogens in cereal grains. Fusarium and its poisonous mycotoxins are distributed worldwide and are of particular interest in agriculture and food safety. A simple analytical method to detect pathogens is essential for forecasting diseases and controlling mycotoxins. This article describes a proposed method for convenient and sensitive detection of Fusarium pathogens that uses the fusion of single-chain variable fragment (scFv) and alkaline phosphatase (AP). A highly reactive scFv antibody specific to soluble cell wall-bound proteins (SCWPs) of F. verticillioides was selected from an immunized chicken phagemid library by phage display. The antibody was verified to bind on the surface of ungerminated conidiospores and mycelia of F. verticillioides. The scFv–AP fusion was constructed, and soluble expression in bacteria was confirmed. Both the antibody properties and enzymatic activity were retained, and the antigen-binding capacity of the fusion was enhanced by the addition of a linker. Surface plasmon resonance measurements confirmed that the fusion displayed 4-fold higher affinity compared with the fusion's parental scFv antibody. Immunoblot analyses showed that the fusion had good binding capacity to the components from SCWPs of F. verticillioides, and enzyme-linked immunosorbent assays revealed that the detection limit of the fungus was below 10−2μgmL−1, superior to the scFv antibody. The fusion protein was able to detect fungal concentrations as low as 10−3mgg−1 of maize grains in both naturally and artificially contaminated samples. Thus, the fusion can be applied in rapid and simple diagnosis of Fusarium contamination in field and stored grain or in food.
Keywords: Fusarium; pathogens; Single-chain variable fragment; Phage display; Alkaline phosphatase; Fusion protein; Enzyme-linked immunosorbent assay