Analytical and Bioanalytical Chemistry (v.408, #1)

E-Health—a topic for analytical chemists? by Günther Gauglitz (1-2).
is Senior Professor at the Eberhard Karls University of Tübingen working in analytical and physical chemistry. He was chairman of the GDCh Division of Analytical Chemistry and chaired the Europt(r)ode VIII meeting. For more than 15 years, his main scientific interests have centered on research and development in chemical and biochemical sensors with special focus on the characterization of interfaces of polymers and biomembrane surfaces, spectroscopic techniques, use of spectral interferometry to monitor changes in optical thickness of thin layers, and effects of Fresnel reflectivity at interfaces. He has been Editor of Analytical and Bioanalytical Chemistry (ABC) since 2002.

has been Full Professor of Analytical Chemistry at the University of Córdoba since 1976. His main research lines are analytical nanoscience and nanotechnology and automatization/miniaturization/quality of (bio)chemical measurement processes. He is the author or coauthor of more than 900 articles indexed in international databases (Hirsch index 50), nine monographs, ten textbooks, and 20 chapters in multiauthor books. He has also been the coordinator of 25 Spanish scientific research projects and 14 international scientific research projects, as well as of 12 contracts with private firms, and has promoted a spin-off company devoted to nanotechnology. He has been supervisor/co-supervisor of 75 doctoral candidates and invited lecturer at 80 international meetings. He is the recipient of numerous national scientific awards (e.g., the Solvay Prize of the Spanish Confederation of Enterprises Organization, 2000; the National Award in Chemistry, 2005; the Maimonides Award, 1993) and international awards (e.g., the Enrich Planquette Award of the Austrian Society of Chemistry, 1996; the Robert Boyle Medal of the Royal Society of Chemistry, UK, 2004; the DAC-EuChemMS Award, 2015). He has also received an honorary doctorate from the University of Valencia (2011, Spain), and has been a full member of the Spanish Royal Academy of Sciences since 2010.

Precision mixology challenge by Juris Meija (7-7).

Solution to rubbery egg challenge by Hervé This (9-10).

Quo vadis, analytical chemistry? by Miguel Valcárcel (13-21).
has been Full Professor of Analytical Chemistry at the University of Córdoba since 1976. His main research lines are analytical nanoscience and nanotechnology, and automatization/miniaturization/quality of (bio)chemical measurement processes. He is the author or co-author of more than 900 articles indexed in international databases (Hirsch index 50), nine monographs, 10 textbooks, and 20 chapters in multi-author books. He has also been the coordinator of 25 Spanish scientific research projects and 14 international scientific research projects, as well as of 12 contracts with private firms, and has promoted a spin-off company devoted to nanotechnology. He has been supervisor/co-supervisor of 75 doctoral candidates, and invited lecturer at 80 international meetings. He is the recipient of numerous national scientific awards (e.g., the Solvay Prize of the Spanish Confederation of Enterprises Organization, 2000; the National Award in Chemistry, 2005; the Maimonides Award, 1993), and international awards (e.g., the Enrich Planquette Award of the Austrian Society of Chemistry, 1996; the Robert Boyle Medal of the Royal Society of Chemistry, UK, 2004; the DAC-EuChemMS Award, 2015). He has also received an honorary doctorate from the University of Valencia, Spain (2011), and has been a full member of the Spanish Royal Academy of Sciences since 2010. This paper presents an open, personal, fresh approach to the future of Analytical Chemistry in the context of the deep changes Science and Technology are anticipated to experience. Its main aim is to challenge young analytical chemists because the future of our scientific discipline is in their hands. A description of not completely accurate overall conceptions of our discipline, both past and present, to be avoided is followed by a flexible, integral definition of Analytical Chemistry and its cornerstones (viz., aims and objectives, quality trade-offs, the third basic analytical reference, the information hierarchy, social responsibility, independent research, transfer of knowledge and technology, interfaces to other scientific–technical disciplines, and well-oriented education). Obsolete paradigms, and more accurate general and specific that can be expected to provide the framework for our discipline in the coming years are described. Finally, the three possible responses of analytical chemists to the proposed changes in our discipline are discussed.
Keywords: Analytical chemistry; Definition; Milestones; Paradigms; Future

Where does flow injection analysis mass spectrometry (FIA-MS) stand relative to ambient mass spectrometry (MS) and chromatography-MS? Improvements in FIA-MS methods have resulted in fast-expanding uses of this technique. Key advantages of FIA-MS over chromatography-MS are fast analysis (typical run time <60 s) and method simplicity, and FIA-MS offers high-throughput without compromising sensitivity, precision and accuracy as much as ambient MS techniques. Consequently, FIA-MS is increasingly becoming recognized as a suitable technique for applications where quantitative screening of chemicals needs to be performed rapidly and reliably. The FIA-MS methods discussed herein have demonstrated quantitation of diverse analytes, including pharmaceuticals, pesticides, environmental contaminants, and endogenous compounds, at levels ranging from parts-per-billion (ppb) to parts-per-million (ppm) in very complex matrices (such as blood, urine, and a variety of foods of plant and animal origin), allowing successful applications of the technique in clinical diagnostics, metabolomics, environmental sciences, toxicology, and detection of adulterated/counterfeited goods. The recent boom in applications of FIA-MS for high-throughput quantitative analysis has been driven in part by (1) the continuous improvements in sensitivity and selectivity of MS instrumentation, (2) the introduction of novel sample preparation procedures compatible with standalone mass spectrometric analysis such as salting out assisted liquid–liquid extraction (SALLE) with volatile solutes and NH4 + QuEChERS, and (3) the need to improve efficiency of laboratories to satisfy increasing analytical demand while lowering operational cost. The advantages and drawbacks of quantitative analysis by FIA-MS are discussed in comparison to chromatography-MS and ambient MS (e.g., DESI, LAESI, DART). Generally, FIA-MS sits ‘in the middle’ between ambient MS and chromatography-MS, offering a balance between analytical capability and sample analysis throughput suitable for broad applications in life sciences, agricultural chemistry, consumer safety, and beyond. Graphical abstract Position of FIA-MS relative to chromatography-MS and ambient MS in terms of analytical figures of merit and sample analysis throughput.
Keywords: Tandem mass spectrometry; Flow injection analysis; High-throughput analysis; Trace-level analysis; Complex matrices; Bio-analysis; Pesticides; Pharmaceuticals

Advances in explosives analysis—part I: animal, chemical, ion, and mechanical methods by Kathryn E. Brown; Margo T. Greenfield; Shawn D. McGrane; David S. Moore (35-47).
The number and capability of explosives detection and analysis methods have increased substantially since the publication of the Analytical and Bioanalytical Chemistry special issue devoted to Explosives Analysis (Moore and Goodpaster, Anal Bioanal Chem 395(2):245–246, 2009). Here we review and critically evaluate the latest (the past five years) important advances in explosives detection, with details of the improvements over previous methods, and suggest possible avenues towards further advances in, e.g., stand-off distance, detection limit, selectivity, and penetration through camouflage or packaging. The review consists of two parts. This part, Part I, reviews methods based on animals, chemicals (including colorimetry, molecularly imprinted polymers, electrochemistry, and immunochemistry), ions (both ion-mobility spectrometry and mass spectrometry), and mechanical devices. Part II will review methods based on photons, from very energetic photons including X-rays and gamma rays down to the terahertz range, and neutrons.
Keywords: Explosives detection; Trace analysis; Explosives; Improvised explosives; Instrumentation; Reviews

Advances in explosives analysis—part II: photon and neutron methods by Kathryn E. Brown; Margo T. Greenfield; Shawn D. McGrane; David S. Moore (49-65).
The number and capability of explosives detection and analysis methods have increased dramatically since publication of the Analytical and Bioanalytical Chemistry special issue devoted to Explosives Analysis [Moore DS, Goodpaster JV, Anal Bioanal Chem 395:245–246, 2009]. Here we review and critically evaluate the latest (the past five years) important advances in explosives detection, with details of the improvements over previous methods, and suggest possible avenues towards further advances in, e.g., stand-off distance, detection limit, selectivity, and penetration through camouflage or packaging. The review consists of two parts. Part I discussed methods based on animals, chemicals (including colorimetry, molecularly imprinted polymers, electrochemistry, and immunochemistry), ions (both ion-mobility spectrometry and mass spectrometry), and mechanical devices. This part, Part II, will review methods based on photons, from very energetic photons including X-rays and gamma rays down to the terahertz range, and neutrons.
Keywords: Explosives detection; Trace analysis; Explosives; Improvised explosives; Instrumentation; Reviews

Digital PCR for direct quantification of viruses without DNA extraction by Jernej Pavšič; Jana Žel; Mojca Milavec (67-75).
DNA extraction before amplification is considered an essential step for quantification of viral DNA using real-time PCR (qPCR). However, this can directly affect the final measurements due to variable DNA yields and removal of inhibitors, which leads to increased inter-laboratory variability of qPCR measurements and reduced agreement on viral loads. Digital PCR (dPCR) might be an advantageous methodology for the measurement of virus concentrations, as it does not depend on any calibration material and it has higher tolerance to inhibitors. DNA quantification without an extraction step (i.e. direct quantification) was performed here using dPCR and two different human cytomegalovirus whole-virus materials. Two dPCR platforms were used for this direct quantification of the viral DNA, and these were compared with quantification of the extracted viral DNA in terms of yield and variability. Direct quantification of both whole-virus materials present in simple matrices like cell lysate or Tris-HCl buffer provided repeatable measurements of virus concentrations that were probably in closer agreement with the actual viral load than when estimated through quantification of the extracted DNA. Direct dPCR quantification of other viruses, reference materials and clinically relevant matrices is now needed to show the full versatility of this very promising and cost-efficient development in virus quantification.
Keywords: Digital PCR; Molecular diagnostics; Direct quantification; Viruses; Virus reference materials; Human cytomegalovirus

One-pot green hydrothermal synthesis of fluorescent nitrogen-doped carbon nanodots for in vivo bioimaging by Tsung-Rong Kuo; Shuo-Yuan Sung; Chun-Wei Hsu; Chih-Jui Chang; Tai-Chia Chiu; Cho-Chun Hu (77-82).
One-pot green synthesis of fluorescent nitrogen-doped carbon nanodots (CNDs) was developed by hydrothermal treatments of biocompatible polyvinylpyrrolidone (PVP) and glycine. The fluorescent nitrogen-doped CNDs exhibited excellent water solubility, low cytotoxicity, and good salt stability for biological imaging. UV-vis spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) spectroscopy, and Raman spectroscopy were applied to confirm the optical and structural characteristics of the CNDs. Fluorescence of the CNDs was tunable from 417 to 450 nm adjusted by different excitation energy. Fluorescent quantum yield of the CNDs (21.43 %) was significantly increased ~47.59 % in comparison to that of the CNDs (14.52 %) without nitrogen doping by glycine. In the in vivo imaging system (IVIS), fluorescence signal of the nitrogen-doped CNDs was obviously observed in the lungs at 12- and 24-h post-injection. Our work has shown the potential applications of the nitrogen-doped CNDs in fluorescence imaging in vivo. Graphical abstract Synthesis of nitrogen-doped carbon nanodots and its application for vivo bioimaging
Keywords: Green synthesis; Carbon nanodots; Nitrogen-doped; Bioimaging

Metabolic footprinting for investigation of antifungal properties of Lactobacillus paracasei by Anders H. Honoré; Stina D. Aunsbjerg; Parvaneh Ebrahimi; Michael Thorsen; Connie Benfeldt; Susanne Knøchel; Thomas Skov (83-96).
is a Principal Scientist at DuPont Nutrition Biosciences ApS with a Ph.D. in microbial metabolomics, LC/MS, and chemometrics. His scientific interests are within optimizing the acquisition and multivariate exploration of data from chromatography–mass spectrometry for investigating food and related systems including microbial and nutritional metabolomics. is a postdoctoral researcher at the Department of Food Science, University of Copenhagen with a Ph.D. in antifungal activity of lactic and propionic acid bacteria. Her scientific interests are bioprotective cultures and antifungal compounds, food microbiology, antimicrobial effect of plant extracts, and microbial characterization of process water in the food industry. is a postdoctoral researcher at the Spectroscopy and Chemometrics Group, University of Copenhagen. During her Ph.D., she focused on studying microbial metabolism by NMR, improving the quality of NMR data for metabolomics studies, and quantifying mold growth and inhibition by multispectral imaging. Her main research interests include metabolomics, multivariate and multiway data analysis, chemometrics, and programming. is a Principal Scientist with an M.Sc. in Organic Chemistry from Aarhus University, Denmark. Since 1986 he has worked for DuPont Nutrition Biosciences ApS (legacy Danisco A/S and Grindsted Products) and has specific expertise within liquid chromatography and mass spectrometry, initially focusing on small molecules and, since 2006, with a focus on protein chemistry and proteomics within food science. is Director of Application Science & Technology in Arla Foods Ingredients Group P/S, and was previously Development Director, Antimicrobials and Antioxidants with DuPont Nutrition Biosciences ApS. She has a background in dairy biochemistry, food technology, and antimicrobials and antioxidants discovery including metabolomics. is Professor and Head of Food Microbiology at the Department of Food Science at University of Copenhagen, Denmark. Her personal research areas involve the impact of food preservation on growth, stress response, and survival of food- and waterborne microorganisms as well as developments in hygiene and sanitation during food processing including biofilm prevention and safe water reuse. An area of interest has also been interactions between microbial populations including the production of antimicrobial compounds and potential development of resistance to these. is an Associate Professor in the Spectroscopy and Chemometrics Section at the University of Copenhagen. His field of research is analysis of data from hyphenated chromatographic systems, pre-processing of chromatographic data in general, metabolomics, foodomics, and recently optimization of industrial biotechnological processes. Lactic acid bacteria with antifungal properties are applied for biopreservation of food. In order to further our understanding of their antifungal mechanism, there is an ongoing search for bioactive molecules. With a focus on the metabolites formed, bioassay-guided fractionation and comprehensive screening have identified compounds as antifungal. Although these are active, the compounds have been found in concentrations that are too low to account for the observed antifungal effect. It has been hypothesized that the formation of metabolites and consumption of nutrients during bacterial fermentations form the basis for the antifungal effect, i.e., the composition of the exometabolome. To build a more comprehensive view of the chemical changes induced by bacterial fermentation and the effects on mold growth, a strategy for correlating the exometabolomic profiles with mold growth was applied. The antifungal properties were assessed by measuring mold growth of two Penicillium strains on cell-free ferments of three strains of Lactobacillus paracasei pre-fermented in a chemically defined medium. Exometabolomic profiling was performed by reversed-phase liquid chromatography in combination with mass spectrometry in electrospray positive and negative modes. By multivariate data analysis, the three strains of Lb. paracasei were readily distinguished by the relative difference of their exometabolomes. The relative differences correlated with the relative growth of the two Penicillium strains. Metabolic footprinting proved to be a supplement to bioassay-guided fractionation for investigation of antifungal properties of bacterial ferments. Additionally, three previously identified and three novel antifungal metabolites from Lb. paracasei and their potential precursors were detected and assigned using the strategy.
Keywords: Untargeted profiling; LC/MS; Multivariate data analysis; Minimal inhibitory concentration; Antifungal

Quantitative profiling of oxylipins in plasma and atherosclerotic plaques of hypercholesterolemic rabbits by Lazar A. Bojic; David G. McLaren; Amy C. Harms; Thomas Hankemeier; Adrie Dane; Sheng-Ping Wang; Ray Rosa; Stephen F. Previs; Douglas G. Johns; Jose M. Castro-Perez (97-105).
Ph.D. is a Senior Scientist at Merck Research Laboratories, where his work focuses on the identification and validation of novel therapies to treat cardiometabolic diseases. He has established an expertise in the development of novel methodologies using mass spectrometry, to aid in the discovery of metabolomic and lipidomic biomarkers of disease state. Ph.D. is a Principal Scientist at Merck Research Laboratories, where his work has focused on the discovery and development of novel therapies to treat cardiometabolic disease. He has specialized in the metabolism of fatty acids and triglycerides and in developing novel, fit-for-purpose methods to measure the activity of lipid metabolizing enzymes in vitro and in vivo using mass spectrometry. has been leading the Biomedical Metabolomics Facility in Leiden since 2010. Major interests include instrumentation, data processing strategies, and quality control. is the Head of the Division of Analytical Biosciences, which is part of the Leiden Academic Centre for Drug Research (LACDR) at Leiden University. He is the Scientific Director of the Netherlands Metabolomics Centre, and is co-founder of MIMETAS, an organ-on-a-chip company, developing predictive cell culture models for better and more reliable customized medicines. Major interests are diagnosis and treatment of metabolic and cardio-/neurovascular diseases, novel analytical technology, metabolomics, and translation of metabolomics from clinical findings to pharmacological treatment. Ph.D. is a Senior Principal Scientist at Merck Research Laboratories where he applies his background in nutritional biochemistry to problems in drug discovery. He oversees the development and utilization of stable isotope tracer kinetic methods in studies that are aimed at determining the influence of drug candidates on rates of biochemical flux. Ph.D. FAHA. In his role as Director in the Cardiometabolic Diseases Department, Douglas leads a research group to identify new targets for the treatment of cardiovascular disease. One area of focus includes the study of lipoprotein metabolism to support clinical atherosclerosis programs at Merck Research Laboratories, where he serves as the basic science lead. These clinical programs include cholesteryl ester transfer protein inhibitors (i.e., Anacetrapib), the Ezetimibe/Zetia franchise, and other programs in various stages of preclinical and clinical development. Ph.D. is the Director of Health Sciences Marketing at Waters Corporation. His expertise is in the field of molecular biomarkers and mass spectrometry across the entire continuum from early discovery to translational research and the clinic. Currently, at Waters, he is spearheading the marketing strategy for proteomics, metabolomics, clinical toxicology, digital molecular imaging by mass spectrometry, and clinical diagnostics. Oxylipins are oxidation products of polyunsaturated fatty acids (PUFAs) that affect a broad range of physiological processes, including cell proliferation, inflammation, inflammation resolution, and vascular function. Moreover, oxylipins are readily detectable in plasma, and certain subsets of oxylipins have been detected in human atherosclerotic lesions. Taken together, we set out to produce a detailed quantitative assessment of plasma and plaque oxylipins in a widely used model of atherosclerosis, to identify potential biomarkers of disease progression. We administered regular chow or regular chow supplemented with 0.5 % cholesterol (HC) to male New Zealand white rabbits for 12 weeks to induce hypercholesterolemia and atherosclerosis. Our targeted lipidomic analyses of oxylipins on plaques isolated from rabbits fed the HC diet detected 34 oxylipins, 28 of which were in compliance with our previously established quality control acceptance criteria. The arachidonic acid (AA) metabolite derived from the COX pathway, 6-keto-PGF1α was the most abundant plaque oxylipin, followed by the linoleic acid (LA) metabolites 9-HODE, 13-HODE and 9,12,13-TriHOME and the arachidonic acid (AA)-derivatives 11-HETE and 12-HETE. We additionally found that the most abundant oxylipins in plasma were three of the five most abundant oxylipins in plaque, namely 11-HETE, 13-HODE, and 9-HODE. The studies reported here make the first step towards a comprehensive characterization of oxylipins as potentially translatable biomarkers of atherosclerosis.
Keywords: Eicosanoids; Atherosclerosis; Lipids; Cholesterol; Plaque; Mass spectrometry

is a PhD student at the National Institute of Biology in Ljubljana, Slovenia. His research is focused on evaluation of novel nucleic acid based techniques to standardize and improve diagnosis of human pathogens, enhance characterization of reference materials and facilitate cancer diagnosis. He is especially interested is exploring the capabilities of digital PCR and high-throughput real-time PCR. is Head of the Genetically Modified Organisms Group at the National Institute of Biology, Slovenia. She has been working for several years on cutting-edge approaches and methods for testing of genetically modified organisms and also the establishment of an internationally harmonized and metrologically sound system for molecular analysis. is Deputy Head of GMO Detection at the National Institute of Biology in Ljubljana, Slovenia, where she is responsible for the introduction of new methods, in-house validations and staff training for the National Reference Laboratory for GMO Detection. Her research is focused on challenges associated with established and novel technologies for nucleic acid measurements as well as standardization and quality control of these technologies. Digital PCR (dPCR) is beginning to supersede real-time PCR (qPCR) for quantification of nucleic acids in many different applications. Several analytical properties of the two most commonly used dPCR platforms, namely the QX100 system (Bio-Rad) and the 12.765 array of the Biomark system (Fluidigm), have already been evaluated and compared with those of qPCR. However, to the best of our knowledge, direct comparison between the three of these platforms using the same DNA material has not been done, and the 37 K array on the Biomark system has also not been evaluated in terms of linearity, analytical sensitivity and limit of quantification. Here, a first assessment of qPCR, the QX100 system and both arrays of the Biomark system was performed with plasmid and genomic DNA from human cytomegalovirus. With use of PCR components that alter the efficiency of qPCR, each dPCR platform demonstrated consistent copy-number estimations, which indicates the high resilience of dPCR. Two approaches, one considering the total reaction volume and the other considering the effective reaction size, were used to assess linearity, analytical sensitivity and variability. When the total reaction volume was considered, the best performance was observed with qPCR, followed by the QX100 system and the Biomark system. In contrast, when the effective reaction size was considered, all three platforms showed almost equal limits of detection and variability. Although dPCR might not always be more appropriate than qPCR for quantification of low copy numbers, dPCR is a suitable method for robust and reproducible quantification of viral DNA, and a promising technology for the higher-order reference measurement method.
Keywords: Digital PCR; Real-time PCR; Molecular diagnostics; Human cytomegalovirus; DNA quantification

Forensic examination of electrical tapes using high resolution magic angle spinning 1H NMR spectroscopy by Torsten Schoenberger; Ulrich Simmross; Christian Poppe (123-129).
is head of the NMR unit of the Forensic Science Institute, Federal Criminal Police Office (Bundeskriminalamt, BKA), Germany. His latest research fields cover quantitative NMR spectroscopy. In addition to quantification of all kinds of organic substances, one of his current main tasks is the structure elucidation of new psychoactive substances. This current work also covers the detection of counterfeit pharmaceuticals as well as the analysis of explosives and polymer-based technical products. is an organic chemist. In 1991 he received his Ph.D. in Polymer Chemistry from the Max Planck Institute for Polymer Research. He works for the Forensic Science Institute of the BKA as a forensic practitioner for material analysis. He chairs the Working Group “Paint and Glass” (EPG) of the European Network of Forensic Science Institutes (ENFSI). is a business chemistry student at the Fresenius University of Applied Science. He worked on the described project during his internship at the BKA. The application of high resolution magic angle spinning (HR-MAS) 1H NMR spectroscopy is ideally suited for the differentiation of plastics. In addition to the actual material composition, the different types of polymer architectures and tacticity provide characteristic signals in the fingerprint of the 1H NMR spectra. The method facilitates forensic comparison, as even small amounts of insoluble but swellable plastic particles are utilized. The performance of HR-MAS NMR can be verified against other methods that were recently addressed in various articles about forensic tape comparison. In this study samples of the 90 electrical tapes already referenced by the FBI laboratory were used. The discrimination power of HR-MAS is demonstrated by the fact that more tape groups can be distinguished by NMR spectroscopy than by using the combined evaluation of several commonly used analytical techniques. An additional advantage of this robust and quick method is the very simple sample preparation.
Keywords: Polymers; Spectroscopy; Instrumentation; NMR

Ultrafast affinity extraction and a two-dimensional high performance affinity chromatographic system were used to measure the free fractions for various drugs in serum and at typical therapeutic concentrations. Pooled samples of normal serum or serum from diabetic patients were utilized in this work. Several drug models (i.e., quinidine, diazepam, gliclazide, tolbutamide, and acetohexamide) were examined that represented a relatively wide range of therapeutic concentrations and affinities for human serum albumin (HSA). The two-dimensional system consisted of an HSA microcolumn for the extraction of a free drug fraction, followed by a larger HSA analytical column for the further separation and measurement of this fraction. Factors that were optimized in this method included the flow rates, column sizes, and column switching times that were employed. The final extraction times used for isolating the free drug fractions were 333–665 ms or less. The dissociation rate constants for several of the drugs with soluble HSA were measured during system optimization, giving results that agreed with reference values. In the final system, free drug fractions in the range of 0.7–9.5 % were measured and gave good agreement with values that were determined by ultrafiltration. Association equilibrium constants or global affinities were also estimated by this approach for the drugs with soluble HSA. The results for the two-dimensional system were obtained in 5–10 min or less and required only 1–5 μL of serum per injection. The same approach could be adapted for work with other drugs and proteins in clinical samples or for biomedical research. Graphical Abstract General scheme for the analysis of free drug fractions in serum by ultrafast affinity chromatography and two-dimensional affinity chromatography. The circles represent the drug and the half-circles on the left are serum proteins that can undergo reversible binding with this drug. The rectangles represent (from left-to-right) a guard column, an affinity microcolumn, and an analytical affinity column that are used to isolate and measure the drug's free fraction in serum
Keywords: Ultrafast affinity extraction; Drug–protein binding; Free drug fraction; Human serum albumin; Affinity microcolumn; Two-dimensional affinity chromatography

d-Amino acids are increasingly being recognized as important signaling molecules, and abnormal levels of d-amino acids have been implicated in the pathogenesis of Alzheimer’s disease. To evaluate the potential relationship between Alzheimer’s disease and d-amino acids, a simple, sensitive, and reliable UPLC-MS/MS method with pre-column derivatization was developed and validated for simultaneous determination of 18 d-amino acids in rat plasma. The analytes were extracted from plasma samples by a protein precipitation procedure, and then derivatized with (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester [(S)-NIFE]. Chromatographic separation was achieved using an ACQUITY UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with a mobile phase composed of acetonitrile containing 8 mM ammonium hydrogen carbonate at a flow rate of 0.6 mL min−1. The analytes were detected by electrospray ionization in positive ion multiple reaction monitoring modes. Under the optimum experimental conditions, all the linear regressions were acquired with r > 0.9932. The limits of quantitation of all derivatized d-amino acids were within 0.05–40.0 ng mL−1 in rat plasma. The intra- and inter-day precisions, expressed as percentage relative standard deviations (%RSD), were within the range of 12.3 and 10.1 %, respectively. The recoveries for all the analytes were observed over the range of 82.8–100.5 % with RSD values less than 12.5 %. Finally, the proposed method was successfully applied to simultaneous determination of the 18 d-amino acids in plasma from Alzheimer’s disease rats and age-matched normal controls. Results showed that the concentrations of d-serine, d-aspartate, d-alanine, d-leucine, and d-proline in Alzheimer’s disease rat plasma were significantly decreased compared with those in normal controls, while d-phenylalanine levels increased. It was revealed that some of these d-amino acids would be potential diagnostic biomarkers for Alzheimer’s disease. Graphical abstract Simultaneous determination of 18 d-amino acids in rat plasma
Keywords: d-Amino acids; Pre-column derivatization; UPLC-MS/MS; Alzheimer’s disease; Biomarkers

Analytical strategy to investigate 3,4-methylenedioxypyrovalerone (MDPV) metabolites in consumers’ urine by high-resolution mass spectrometry by María Ibáñez; Óscar J. Pozo; Juan V. Sancho; Teresa Orengo; Gonzalo Haro; Félix Hernández (151-164).
The potential of high-resolution mass spectrometry (HRMS) for the investigation of human in vivo metabolism of 3,4-methylenedioxypyrovalerone (MDPV) using urine collected from a consumer (this is, in non-controlled experiments) has been investigated. As a control sample was not available, the common approach based on the comparison of a control/blank sample and samples collected after drug intake could not be used. Alternatively, an investigation based on common fragmentation pathways was applied, assuming that most metabolites share some fragments with the parent drug. An extension of this approach was also applied based on the fragmentation pathway of those metabolites identified in urine samples in the first step. The use of MSE experiments (sequential acquisition of mass spectra at low and high collision energy) has been crucial to this aim as it allowed promoting fragmentation in the collision cell without any previous precursor ion selection. MDPV belongs to the group of new psychoactive substances (NPS), being known as the “cannibal drug”. This substance is being abused more and more and is associated with dangerous side effects. The human metabolites (both phase I and phase II) were detected and tentatively identified by accurate mass full-spectrum measurements using ultra-high performance liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS). Following this strategy, up to 10 phase I metabolites, together with some glucuronides and sulphates, were detected and tentative structures were proposed. Several compounds identified in this work have not been previously reported in the literature. Graphical abstract Detection of metabolites of MDPV by common fragmentation pathway
Keywords: New psychoactive substances; 3,4-Methylenedioxypyrovalerone; Metabolism; Urine; Liquid chromatography; Time-of-flight mass spectrometry

Atomic force microscopy based investigations of anti-inflammatory effects in lipopolysaccharide-stimulated macrophages by Jiang Pi; Huaihong Cai; Fen Yang; Hua Jin; Jianxin Liu; Peihui Yang; Jiye Cai (165-176).
A new method based on atomic force microscopy (AFM) was developed to investigate the anti-inflammatory effects of drugs on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. The LPS-stimulated RAW264.7 macrophage cell line is a widely used in vitro cell model for the screening of anti-inflammatory drugs or the study of anti-inflammatory mechanisms. In this work, the inhibitory effects of dexamethasone and quercetin on LPS–CD14 receptor binding in RAW264.7 macrophages was probed by LPS-functionalized tips for the first time. Both dexamethasone and quercetin were found to inhibit LPS-induced NO production, iNOS expression, IκBα phosphorylation, and IKKα/β phosphorylation in RAW264.7 macrophages. The morphology and ultrastructure of RAW264.7 macrophages were determined by AFM, which indicated that dexamethasone and quercetin could inhibit LPS-induced cell surface particle size and roughness increase in RAW264.7 macrophages. The binding of LPS and its receptor in RAW264.7 macrophages was determined by LPS-functionalized AFM tips, which demonstrated that the binding force and binding probability between LPS and CD14 receptor on the surface of RAW264.7 macrophages were also inhibited by dexamethasone or quercetin treatment. The obtained results imply that AFM, which is very useful for the investigation of potential targets for anti-inflammatory drugs on native macrophages and the enhancement of our understanding of the anti-inflammatory effects of drugs, is expected to be developed into a promising tool for the study of anti-inflammatory drugs.
Keywords: Atomic force microscopy; Anti-inflammatory; Lipopolysaccharide; Macrophages; CD14 receptor

A new UHPLC-UV method has been developed for the simultaneous analysis of seven alkaloids [ajmaline (1), yohimbine (2), corynanthine (3), ajmalicine (4), serpentine (5), serpentinine (6), and reserpine (7)] from the root samples of Rauwolfia serpentina (L.) Benth. ex Kurz. The chromatographic separation was achieved using a reversed phase C18 column with a mobile phase of water and acetonitrile, both containing 0.05 % formic acid. The seven compounds were completely separated within 8 min at a flow rate of 0.2 mL/min with a 2-μL injection volume. The method is validated for linearity, accuracy, repeatability, limits of detection (LOD), and limits of quantification (LOQ). Seven plant samples and 21 dietary supplements claiming to contain Rauwolfia roots were analyzed and content of total alkaloids (17) varied, namely, 1.57–12.1 mg/g dry plant material and 0.0–4.5 mg/day, respectively. The results indicated that commercial products are of variable quality. The developed analytical method is simple, economic, fast, and suitable for quality control analysis of Rauwolfia samples and commercial products. The UHPLC-QToF-mass spectrometry with electrospray ionization (ESI) interface method is described for the confirmation and characterization of alkaloids from plant samples. This method involved the detection of [M + H]+ or M+ ions in the positive mode.
Keywords: Rauwolfia serpentina ; Alkaloids; Ultra-high performance liquid chromatography-photo diode array; Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry; Dietary supplements

This study presents the development, optimization, and validation of a novel method for the determination of polychlorinated naphthalenes (PCNs) by liquid chromatography-atmospheric pressure photoionization (APPI), using toluene as dopant. The mass spectra of PCN 52, 54, 66, 67, 73, and 75 were recorded in negative ionization. The base ions corresponded to [M–Cl+O], where M is the analyte molecule. A strategy, which includes designs of experiments, for the development, the evaluation, and the optimization of the LC-APPI-MS/MS methods is also described. Finally, a highly sensitive method with low instrumental limits of detection (LoDs), ranging from 0.8 pg for PCN 75 to 16 pg for PCN 54 on column, was validated. A Thermo Hypersil Green PAH (100 mm × 2.1 mm, 3 μm) column was used with acetonitrile/water/methanol as mobile phase. The method was applied for the determination of the selected PCNs in surface and tap water samples. A simple liquid–liquid extraction method for the extraction of PCNs from water samples was used. Method LoQs ranged from 29 ng L−1, for PCN 73, to 63 ng L−1, for PCN 54, and the recoveries ranged from 97 to 99 %, for all congeners. This is the first LC-APPI-MS/MS method for the determination of PCNs in water samples.
Keywords: Polychlorinated naphthalenes (PCNs); Atmospheric pressure photoionization (APPI); Dopant; LC-APPI-MS/MS; Pseudo-SRM; Experimental design

A systematic study on the influence of pigments and sample aging on casein identification was performed on 30 reconstructed paints. The protein in all the paints was extracted into solution for analysis. The amount of protein that can be retrieved for solution-based analysis in each of the reconstructed paints was studied with a well-developed NanoOrange method before and after artificial aging. The results showed that in the paints with calcium phosphate (in bone black) and copper carbonate, hydroxide, or acetate (in verdigris and azurite), the amount of protein that can be retrieved for liquid-phase analysis is much smaller than the other paints, indicating that the protein degradation was accelerated significantly in those paints. Carbon (in vine black), calcium carbonate (in natural chalk), and calcium sulfate (terra alba gypsum and ground alabaster) did not affect much the amount of protein that can be retrieved in the paints compared to non-pigmented binder, meaning that the protein degradation rate was not affected much by those pigments. Artificial aging was observed to decrease the amount of retrievable protein in all the reconstructed paints that were studied. The enzyme-linked immunosorbent assay (ELISA) method was applied to the 28 reconstructed paints (except two verdigris paints) to assess the protein identification. The ELISA responses from the different paints were compared at fixed protein concentrations. Natural chalk, bone black, raw sienna, stack lead white, and cochineal red-violet lake had the lowest ELISA signal in this study, which indicated that the binding sites (epitopes) on the target protein in these paints are likely to deteriorate more than those in the other paints. Artificial aging did not influence the ELISA response as much as the pigments when the protein concentration was kept the same for the paints that were studied.
Keywords: Casein paint; Cultural heritage; Protein degradation; Pigment and protein interaction; ELISA; NanoOrange

Recombinant proteins are frequently hampered by aggregation during the refolding and purification process. A simple and rapid method for in vitro refolding and purification of recombinant human parathyroid hormone (rhPTH 1–34) expressed in Escherichia coli with protein folding size exclusion chromatography (PF-SEC) was developed in the present work. Discrete effects of potential solution additives such as urea, polypolyethylene glycol, proline, and maltose on the refolding with simultaneous purification of rhPTH were investigated. The results of individual additives indicated that both maltose and proline had remarkable influences on the efficiency of refolding with a recovery yield of 65 and 66 % respectively. Further, the synergistic effect of these additives on refolding was also explored. These results demonstrate that the additive combinations are more effective for inhibiting protein aggregation during purification of rhPTH in terms of recovery yield, purity, and specific activity. The maltose and proline combination system achieved the highest renatured rhPTH having a recovery yield of 78 %, a purity of ≥99 %, and a specific activity of 3.31 × 103 cAMP pM/cell respectively, when compared to the classical dilution method yield (41 %) and purity (97 %). In addition, the role of maltose and proline in a combined system on protein aggregation and refolding has been explained. The molecular docking (in silico) scores of maltose (−10.91) and proline (−9.0) support the in vitro results.
Keywords: PFLC; Size exclusion chromatography; Purity; Recovery yield; Specific activity; rhPTH

Soil can contain large numbers of endocrine disrupting chemicals (EDCs). The varied physicochemical properties of EDCs constitute a great challenge to their determination in this type of environmental matrix. In this work, an analytical method was developed for the simultaneous determination of various classes of EDCs, including parabens, alkylphenols, phenylphenols, bisphenol A, and triclosan, in soils, sediments, and sewage sludge. The method uses microwave-assisted extraction (MAE) in combination with continuous solid-phase extraction for determination by gas chromatography–mass spectrometry. A systematic comparison of the MAE results with those of ultrasound-assisted and Soxhlet extraction showed MAE to provide the highest extraction efficiency (close to 100 %) in the shortest extraction time (3 min). The proposed method provides a linear response over the range 2.0 − 5000 ng kg−1 and features limits of detection from 0.5 to 4.5 ng kg−1 depending on the properties of the EDC. The method was successfully applied to the determination of target compounds in agricultural soils, pond and river sediments, and sewage sludge. The sewage sludge samples were found to contain all target compounds except benzylparaben at concentration levels from 36 to 164 ng kg−1. By contrast, the other types of samples contained fewer EDCs and at lower concentrations (5.6 − 84 ng kg−1).
Keywords: Endocrine disrupting chemicals; Environmental solid samples; Continuous solid-phase extraction; Microwave-assisted extraction; Gas chromatography–mass spectrometry

A new procedure based on direct insert microvial thermal desorption injection allows the direct analysis of ionic liquid extracts by gas chromatography and mass spectrometry (GC-MS). For this purpose, an in situ ionic liquid dispersive liquid–liquid microextraction (in situ IL DLLME) has been developed for the quantification of bisphenol A (BPA), bisphenol Z (BPZ) and bisphenol F (BPF). Different parameters affecting the extraction efficiency of the microextraction technique and the thermal desorption step were studied. The optimized procedure, determining the analytes as acetyl derivatives, provided detection limits of 26, 18 and 19 ng L−1 for BPA, BPZ and BPF, respectively. The release of the three analytes from plastic containers was monitored using this newly developed analytical method. Analysis of the migration test solutions for 15 different plastic containers in daily use identified the presence of the analytes at concentrations ranging between 0.07 and 37 μg L−1 in six of the samples studied, BPA being the most commonly found and at higher concentrations than the other analytes.
Keywords: Ionic liquid dispersive liquid–liquid microextraction; Direct insert microvial thermal desorption; Gas chromatography–mass spectrometry; Bisphenols; Migration studies

A comprehensive and sensitive method for hair analysis in drug-facilitated crimes and incorporation of zolazepam and tiletamine into hair after a single exposure by Jihyun Kim; Hyesun Yum; Moonhee Jang; Ilchung Shin; Wonkyung Yang; Seungkyung Baeck; Joon Hyuk Suh; Sooyeun Lee; Sang Beom Han (251-263).
Hair is a highly relevant specimen that is used to verify drug exposure in victims of drug-facilitated crime (DFC) cases. In the present study, a new analytical method involving ultrahigh-performance liquid chromatography-tandem mass spectrometry was developed for determining the presence of model drugs, including zolazepam and tiletamine and their metabolites in hair specimens from DFCs. The incorporation of zolazepam and tiletamine into hair after a single exposure was investigated in Long-Evans rats with the ratio of the hair concentration to the area under the curve. For rapid and simple sample preparation, methanol extraction and protein precipitation were performed for hair and plasma, respectively. No interference was observed in drug-free hair or plasma, except for hair-derived diphenhydramine in blank hair. The coefficients of variance of the matrix effects were below 12 %, and the recoveries of the analytes exceeded 70 % in all of the matrices. The precision and accuracy results were satisfactory. The limits of quantification ranged from 20 to 50 pg in 10 mg of hair. The drug incorporation rates were 0.03 ± 0.01 % for zolazepam and 2.09 ± 0.51 % for tiletamine in pigmented hair. We applied the present method to real hair samples in order to determine the drug that was used in seven cases. These results suggest that this comprehensive and sensitive hair analysis method can successfully verify a drug after a single exposure in crimes and can be applied in forensic and clinical toxicology laboratories.
Keywords: Hair analysis; Drug-facilitated crimes; Single drug exposure; Drug incorporation rates; Zolazepam; Tiletamine

Recent studies suggesting the involvement of singlet oxygen in the pathogenesis of multiple diseases have attracted renewed attention to lipid oxidation mediated by singlet oxygen. Although the rate constants for singlet oxygen quenching by antioxidants have been measured extensively, the inhibition of lipid oxidation mediated by singlet oxygen has received relatively less attention, partly because a convenient method for measuring the rate of lipid oxidation is not available. The objective of this study was to develop a convenient method to measure plasma lipid oxidation mediated by singlet oxygen which may be applied to a rapid assessment of the antioxidant capacity to inhibit this oxidation using a conventional microplate reader. Singlet oxygen was produced from naphthalene endoperoxide, and lipid hydroperoxide production was followed by using diphenyl-1-pyrenylphosphine (DPPP). Non-fluorescent DPPP reacts stoichiometrically with lipid hydroperoxides to give highly fluorescent DPPP oxide. It was found that plasma oxidation by singlet oxygen increased the fluorescence intensity of DPPP oxide, which was suppressed by antioxidants. Fucoxanthin suppressed the oxidation more efficiently than β-carotene and α-tocopherol, while ascorbic acid and Trolox were not effective. The present method may be useful for monitoring lipid oxidation and also for rapid screening of the capacity of dietary antioxidants and natural products to inhibit lipid oxidation in a biologically relevant system.
Keywords: Antioxidant; Carotenoid; Diphenyl-1-pyrenylphosphine; Plasma lipid oxidation; Singlet oxygen

Physicochemical and toxicological evaluation of silica nanoparticles suitable for food and consumer products collected by following the EC recommendation by Catia Contado; Jorge Mejia; Omar Lozano García; Jean-Pascal Piret; Elise Dumortier; Olivier Toussaint; Stéphane Lucas (271-286).
Specific information about the particle size distribution, agglomeration state, morphology, and chemical composition of four silica samples, used as additives in food and in personal care products, were achieved with a combination of analytical techniques. The combined use of differential centrifugal sedimentation (DCS), sedimentation field flow fractionation (SdFFF), and scanning and transmission electron microscopy (SEM and TEM) allows to classify the water dispersed samples as “nanomaterials” according to the EC definition. The mechanical stirring and the ultrasound treatment were compared as dispersion methods. The particle surface chemical composition, determined by particle-induced X-ray emission (PIXE) and X-ray photoelectron spectroscopy (XPS), assessed the different levels of purity between the pyrogenic and the precipitated silica and highlighted particle surface chemical composition modifications in the outer shell when dispersed by mechanical stirring. The potential toxic effects of silica on intestinal Caco-2 cells were investigated using MTS assay and by measuring lactate dehydrogenase (LDH) release and caspases 3/7 activity after 24 h of incubation. No or limited decrease of cell viability was observed for all particles regardless of dispersion procedure, suggesting a relative innocuity of these silica samples.
Keywords: Silica nanoparticles; Food additives; Surface analysis; In vitro tests; Differential centrifugal sedimentation (DCS); Sedimentation field flow fractionation (SdFFF)

Sensitive detection of cyanide using bovine serum albumin-stabilized cerium/gold nanoclusters by Chia-Wei Wang; Ya-Na Chen; Bo-Yi Wu; Cheng-Kai Lee; Ying-Chieh Chen; Yu-Huei Huang; Huan-Tsung Chang (287-294).
A simple, sensitive, and selective fluorescence assay for the detection of CN has been demonstrated using bovine serum albumin-stabilized cerium/gold nanoclusters (BSA–Ce/Au NCs). When excited at 325 nm, BSA–Ce/Au NCs have two fluorescence bands centered at 410 and 658 nm, which are assigned to BSA–Ce/Au complexes and Au NCs, respectively. Each BSA–Ce/Au NC contains 22 Au atoms and 8 Ce ions. Through etching of the Au core in BSA–Ce/Au NCs by CN, the fluorescence at 658 nm is quenched, while that at 410 nm enhances during the formation of complexes among BSA, Ce4+, and [Au(CN)2]. The circular dichroism spectra reveal that relative to BSA–Au NCs, BSA–Ce/Au NCs have looser structures of the BSA templates. As a result, it is easier for CN to access the Au cores in BSA–Ce/Au NCs, allowing faster (within 15 min) etching of the Au cores by CN. At pH 12.0, this assay allows the detection of CN down to 50 nM, with linearity over 0.1–15 μM. This assay has been applied to the determination of the concentrations of CN in spiked drinking water and pond water samples.
Keywords: Fluorescence; Nanoclusters; Cerium; Gold; Cyanide

A direct solid sampling analysis method for the detection of silver nanoparticles in biological matrices by Nadine S. Feichtmeier; Nadine Ruchter; Sonja Zimmermann; Bernd Sures; Kerstin Leopold (295-305).
Engineered silver nanoparticles (AgNPs) are implemented in food contact materials due to their powerful antimicrobial properties and so may enter the human food chain. Hence, it is desirable to develop easy, sensitive and fast analytical screening methods for the determination of AgNPs in complex biological matrices. This study describes such a method using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (GFAAS). A recently reported novel evaluation strategy uses the atomization delay of the respective GFAAS signal as significant indicator for AgNPs and thereby allows discrimination of AgNPs from ionic silver (Ag+) in the samples without elaborate sample pre-treatment. This approach was further developed and applied to a variety of biological samples. Its suitability was approved by investigation of eight different food samples (parsley, apple, pepper, cheese, onion, pasta, maize meal and wheat flour) spiked with ionic silver or AgNPs. Furthermore, the migration of AgNPs from silver-impregnated polypropylene food storage boxes to fresh pepper was observed and a mussel sample obtained from a laboratory exposure study with silver was investigated. The differences in the atomization delays (Δt ad) between silver ions and 20-nm AgNPs vary in a range from −2.01 ± 1.38 s for maize meal to +2.06 ± 1.08 s for mussel tissue. However, the differences were significant in all investigated matrices and so indicative of the presence/absence of AgNPs. Moreover, investigation of model matrices (cellulose, gelatine and water) gives the first indication of matrix-dependent trends. Reproducibility and homogeneity tests confirm the applicability of the method. Graphical Abstract Direct detection of silver nanoparticles in biological samples
Keywords: Silver nanoparticle detection; Direct solid sampling; Graphite furnace atomic absorption spectrometry; Silver nanoparticle entry in food; Biological samples; Robust screening method

A multi-mycotoxin stable isotope dilution LC-MS/MS method was developed for 14 Fusarium toxins including modified mycotoxins in cereals (deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, HT2-toxin, T2-toxin, enniatin B, enniatin B1, enniatin A1, enniatin A, beauvericin, fusarenone X, nivalenol, deoxynivalenol-3-glucoside, and zearalenone). The chromatographic separation of the toxins with particular focus on deoxynivalenol and deoxynivalenol-3-glucoside was achieved using a C18-hydrosphere column. An expedient sample preparation method was developed that uses solid-phase extraction for the purification of trichothecenes combined with zearalenone, enniatins, and beauvericin and provides excellent validation data. Linearity, intra-day precision, inter-day precision, and recoveries were ≥0.9982, 1–6 %, 5–12 %, and 79–117 %, respectively. Method accuracy was verified by analyzing certified reference materials for deoxynivalenol, HT2-toxin, and T2-toxin with deviations below 7 %. The results of this method found barley malt samples from 2012, 2013, and 2014 frequently contaminated with high concentrations of enniatin B, deoxynivalenol, and its modified mycotoxin deoxynivalenol-3-glucoside. Samples from 2012 were especially contaminated. Fusarenone X was not detected in any of the analyzed samples.
Keywords: Trichothecenes; Enniatins; Stable isotope dilution assay; LC-MS/MS; Solid-phase extraction; Barley

FTIR spectroscopy characterization of fatty-acyl-chain conjugates by Vladimir Bobroff; Cyril Rubio; Valérie Vigier; Cyril Petibois (319-326).
FTIR spectroscopy is used to identify poly-l-lysin fatty-acyl-chain (PLL-FAC) conjugates based on structural differences found between FAC species. Twenty-one PLL-FAC models were used, from C8 to C24, and with up to 5 unsaturation levels (C20:5). Curve fitting of the 3050–2800 cm−1 spectral interval permitted extraction of IR bands belonging to the stretching vibration modes of methyl, methylene, and alkene groups. Based on molecular structure models in 3D, the number and position of methyl bands could be set according to chain length and unsaturation level. Band positions for ν-(C = C < H), νas(CH3), and νas(CH2) groups did not follow the maximum intensity shift of spectrum curve; it is the underlying band’s intensity that is modifying maximum intensity of spectrum curve with respect to chain length and unsaturation level. We thus propose to use FTIR spectroscopy for the production monitoring and the quality control of PLL-FAC conjugates used as nutritional complements, and this should be extended to analysis of fatty acid compounds in general. Graphical abstract Legend: Fatty-acyl-chain FTIR spectra bands assignation according to curve-fitting methods and cross-validated by molecular structure modeling. Series of fatty-acyl-chain conjugates of different length and with increased unsaturation levels allow determining the position of ν(-C = C < H), νas(CH3), and νas(CH2) groups. It is also demonstrated that νas(CH3) groups from polypeptidic chain or fatty acids do not raise and absorption band at the same location. Finally, νas(CH2) groups raise different absorption bands according to their position in the fatty acyl chain, at primer position (close to ester or amide bond), inner or terminal positions. The unsaturations of fatty acyl chains give rise to at least two ν(-C = C < H) absorption bands with second unsaturation group.
Keywords: FTIR spectroscopy; Structural biology; Saturated, mono-unsaturated, and poly-unsaturated fatty acids; Fatty acid amide; Nutrition; Quality control

The increasing demand for easily available and low-cost diagnostics has fuelled the development of aptasensors as platforms for rapid, sensitive, and point-of-care testing of target analytes. Recently, gold nanoparticle (AuNP)-based aptasensors have attracted wide recognition owing to their color transition properties which allow real-time rapid sensing of targets. In this study, we utilized the color transition property of aptamer-functionalized AuNPs to detect and quantify estrogen receptor alpha (ERα), a key biomarker protein in breast cancer. We found that the coating of AuNPs with unmodified ERα-RNA aptamer (GGGGUCAAGGUGACCCC) makes them resistant to salt-induced aggregation. However, addition of ERα to the aptamer-protected AuNPs results in their spontaneous aggregation as evident from a color transition from wine red to deep blue. On the basis of this, we developed an ERα aptasensor, with limits of detection and quantification of 0.64 and 2.16 ng/mL, respectively; the aptasensor can efficiently detect and quantify ERα in a working range of 10 ng/mL–5μg/mL protein. Validation of the aptasensor on cellular extracts of ERα-positive MCF-7 and ERα-deficient MDA-MB-231 breast cancer cells showed a target-selective response in ERα-positive samples but not in cellular extracts of ERα-deficient breast cancer cells. Further, the small size and simple fabrication chemistry of aptamers provide an additional benefit to make the ERα aptasensor a potentially useful and cost-effective tool in point-of-care analyses of ERα. Graphical Abstract Schematic representation of developed AuNP-based ER-aptasensor
Keywords: Gold nanoparticles; RNA aptamer; Colorimetric aptasensor; Estrogen receptor alpha; Breast cancer

The present study reports a highly simple and rapid method for the detection of a widely used and extremely toxic organophosphorus pesticide, phorate. The detection employs a pesticide-specific aptamer as the recognition element and gold nanoparticles as the optical sensors. The aptamer, owing to its random coil structure, provides stability to the gold nanoparticles upon linking, thereby keeping the nanoparticles well dispersed. However, on the addition of the target pesticide, the aptamer acquires a rigid conformation resulting in the aggregation of the gold nanoparticles. Consequently, the color of the solution changes from red to blue and is easily observable with the naked eye. The proposed method was linear in the concentration range of 0.01 nM to 1.3 μm with the limit of detection as low as 0.01 nM. Moreover, the proposed assay selectively recognized phorate in the presence of other interfering substances and, thus, can be applied to real samples for the rapid and efficient screening of phorate.
Keywords: Bioanalytical methods; Biosensors; Nanoparticles/nanotechnology