Analytical and Bioanalytical Chemistry (v.410, #24)

Analytical developments in advancing safety in nanotechnology by Lisa Holland; Wenwan Zhong (6037-6039).
is Professor of Chemistry at West Virginia University, specializing in microscale separations of biomolecules relevant to human health.   She received her B.S. degree in Chemistry from the University of Maryland at College Park. She received her Ph.D. in Chemistry from the University of North Carolina at Chapel Hill under the direction of Professor James Jorgenson.  Through a National Research Service Award she held a postdoctoral fellowship under the direction of Professor Susan Lunte in the Department of Pharmaceutical Chemistry at the University of Kansas.  Dr. Holland is the recipient of a National Science Foundation Faculty Early Career Development award and has served as the Chair of the American Chemical Society Subdivision of Chromatography and Separation Chemistry. She enjoys teaching instrumental analysis to undergraduate and graduate students and mentoring the many outstanding researchers who have engaged in science at WVU. is Professor of Chemistry at the University of California, Riverside. She obtained her Ph.D. in Analytical Chemistry from Iowa State University under the guidance of Professor Edward S. Yeung, and did her postdoctoral research in Los Alamos National Lab before joining Department of Chemistry, University of California, Riverside, as an assistant professor in 2006. Her research focuses on the development and applications of microscale separation technologies and bioanalytical sensors to improve disease diagnosis and treatment. Her current work covers three distinct areas: the use of microfluidics and flow field flow fractionation for analysis of circulating biomarkers; the use of capillary electrophoresis, mass spectrometry, and optical spectroscopy for assessment of the interaction between engineered nanomaterials and biomolecules; and the use of synthetic receptors for exploration of post-translational modifications in proteins.

Enhancing research for undergraduates through a nanotechnology training program that utilizes analytical and bioanalytical tools by Lisa A. Holland; Jeffrey S. Carver; Lindsay M. Veltri; Rachel J. Henderson; Kimberly D. Quedado (6041-6050).
is a Professor of Chemistry at West Virginia University, specializing in microscale separations of biomolecules relevant to human health. She received her B.S. degree in Chemistry from the University of Maryland at College Park. She received her Ph.D. in Chemistry from the University of North Carolina at Chapel Hill under the direction of Professor James Jorgenson. Through a National Research Service Award, she held a postdoctoral fellowship under the direction of Professor Susan Lunte in the Department of Pharmaceutical Chemistry at the University of Kansas. Dr. Holland is the recipient of a National Science Foundation Faculty Early Career Development award and has served as the Chair of the American Chemical Society Subdivision of Chromatography and Separation Chemistry. She enjoys teaching instrumental analysis to undergraduate and graduate students and mentoring the many outstanding researchers who have engaged in science at WVU. is the Director of K-12 STEM Education Initiative and Associate Professor of Science Education at West Virginia University. He attended Illinois State University to study chemistry. After a completed Masters and Doctorate, he pursued a career in Science Teacher Education at West Virginia University. His research interests focus on the improvement of teaching and learning in the STEM disciplines at all levels (p-20), particularly in ways that help students connect science to daily living. Current projects include integration of technology into science classrooms using three-dimensional art design and simple robotic components, a Nanotechnology research program for teachers, a Solar Panel installation and study at a local high school, and looking for novel ways to improve large lecture chemistry and physics courses. is a Ph.D. candidate at West Virginia University. She earned her B.S. in Chemistry from West Virginia University in 2018. She is the recipient of the 2017 ACS Division of Analytical Chemistry Undergraduate Award and the College Chemistry Award from the Society for Analytical Chemists of Pittsburgh. Her academic interests include the design and application of microfluidic devices for medical diagnostics, drug discovery, and the development of nanomaterials for biological detection. is a postdoctoral researcher in the Department of Physics and Astronomy at Michigan State University (MSU). Working in the Physics Education Research Lab (PERL) at MSU, her research focus is on developing formal structures to support transformed physics laboratories while developing assessment tools and practices for understanding student learning in these laboratory courses. Rachel recently finished her doctoral work in the Department of Physics & Astronomy at West Virginia University where she focused her research on exploring how classroom diversity and inclusion impacted student performance on the most commonly used conceptual physics assessments in the introductory physics classroom. In addition to research, Rachel currently serves as a member-at-large on the American Physical Society Forum on Outreach and Engaging the Public (APS-FOEP). Most of her service to the forum has been dedicated to publishing newsletter articles highlighting outreach experiences from the perspective of graduate students and other early career individuals. is the Assistant Director of the Office of Undergraduate Research at West Virginia University. She earned her B.S. in Chemistry from the primarily undergraduate institution, Wheeling Jesuit University in Wheeling, WV. She continued her education at West Virginia University at which she received her M.S., Ph.D., and M.A. degrees. Dr. Quedado has diverse experience in higher education as both an assistant professor teaching chemistry and biochemistry related courses and as a manager of graduate and undergraduate traineeship programs. Nanotechnology is a broad field combining traditional scientific disciplines; however, analytical chemistry plays an important role in material design, synthesis, characterization, and application. This article emphasizes the uniqueness of nanotechnology and the importance of providing high-quality undergraduate research experiences to both attract and retain talented individuals to the field of nanotechnology. In response to this need to develop a strong and sustainable nanotechnology work force, strategies to create authentic research experiences are considered within the framework of an interdisciplinary nanotechnology environment at West Virginia University. The program, named NanoSAFE Research Experiences for Undergraduates (REU), embeds students in different departments at West Virginia University and in research laboratories within the National Institute of Occupational Safety and Health. A large number of participants have little or no prior research experience and a strong effort is made to recruit applicants from under-represented populations. Components designed to foster research proficiency include frequent reporting, a strong peer-network, and training for secondary mentors. Evidence, which includes student publications and assessment findings demonstrating self-efficacy, is discussed to substantiate the viability of the strategies used in the 2016–2018 program. Graphical abstractᅟ
Keywords: Nanotechnology; Undergraduate research; REU; Training program

Intelligent testing strategy and analytical techniques for the safety assessment of nanomaterials by Rui Chen; Jiyan Qiao; Ru Bai; Yuliang Zhao; Chunying Chen (6051-6066).
Nanomaterials (NMs) are widely used in various areas because of their unique and useful physicochemical properties. However, they may pose toxicity risks to human health after exposure. Applicable and reliable approaches are needed for risk assessment of NMs. Herein, an intelligent analytical strategy for safety assessment of NMs is proposed that focuses on toxicity assessment using an in vitro cell model. The toxicity assessment by testing on the adverse outcome pathway in a cell culture system was defined by application of a tiered testing approach. To provide an overview of the applicable approach for risk assessment of NMs, we discuss the most commonly used techniques and analytical methods, including computational toxicology methods in dosimetry assessment, high-throughput screening for toxicity testing with high efficiency, and omics-based toxicology assessment methods. The final section focuses on the route map for an integrated approach to a testing and assessment strategy on how to extrapolate the in vitro NM toxicity testing data to in vivo risk assessment of NMs. The intelligent analytical strategy, having evolved step-by-step, could contribute to better applications for safety evaluation and risk assessment of NMs in reality.
Keywords: Nanotoxicology; Adverse outcome pathway; Nanoparticles; Risk assessment; Computational nanotoxicology; Dosimetry

Mass spectrometry-based proteomics for system-level characterization of biological responses to engineered nanomaterials by Tong Zhang; Matthew J. Gaffrey; Brian D. Thrall; Wei-Jun Qian (6067-6077).
The widespread use of engineered nanomaterials or nanotechnology makes the characterization of biological responses to nanomaterials an important area of research. The application of omics approaches, such as mass spectrometry-based proteomics, has revealed new insights into the cellular responses of exposure to nanomaterials, including how nanomaterials interact and alter cellular pathways. In addition, exposure to engineered nanomaterials often leads to the generation of reactive oxygen species and cellular oxidative stress, which implicates a redox-dependent regulation of cellular responses under such conditions. In this review, we discuss quantitative proteomics-based approaches, with an emphasis on redox proteomics, as a tool for system-level characterization of the biological responses induced by engineered nanomaterials. Graphical abstractᅟ
Keywords: Engineered nanomaterials; Proteomics; Post-translational modifications; Redox proteomics; Thiol; Oxidative stress

Emerging technologies for optical spectral detection of reactive oxygen species by Johanna Herman; Yinan Zhang; Vincent Castranova; Sharon L. Neal (6079-6095).
This review surveys recent advances in optical spectral detection of reactive oxygen species (ROS), particularly singlet oxygen, superoxide, hydroxyl radical, and hydrogen peroxide. Advances using nanoparticles and self-organizing nanostructures as well as optical detection schemes are included. Measurements using plasmonic, luminescent, photocatalytic, or self-organizing nanoparticles are highlighted. The large number of spectrophotometric and luminescent probe methods are categorized by ROS sensing mechanism, signaling mode, (de)activation mechanism, if any, and spectral chromaticity. Reports describing multicomponent ROS detection or novel nanoscale probes are discussed. Measurements using ratiometric, multichannel, or time-resolved detection and nonlinear spectral transitions are reviewed. The focus on developing probe molecules for spectral detection documented over the last 20 years has continued, with sustained emphasis on luminescence detection, but with less focus on spectrophotometric measurements. Use of nanoparticles as probes, probe carriers, and compartmentalization agents in ROS detection is increasing. On the other hand, incorporation of advanced spectral methods, such as nonlinear transition and multichannel detection, is increasing slowly in ROS analysis. This indicates there is a substantial opportunity to develop ROS measurements with use of a synergistic combination of (multi)functional nanoscale systems and advanced optical detection methods to optimize the detection limit, selectivity, and response time. Graphical abstractᅟ
Keywords: Reactive oxygen species; Optical detection; Spectral detection; Nanoparticles; Nanostructured media

With the rapid development and numerous applications of engineered nanomaterials (ENMs) in science and technology, their impact on environmental health and safety should be considered carefully. This requires an effective platform to investigate the potential adverse effects and hazardous biological outcomes of numerous nanomaterials and their formulations. We consider predictive toxicology a rational approach for this effort, which utilizes mechanism-based in vitro high-throughput screening (HTS) to make predictions on ENMs’ adverse outcomes in vivo. Moreover, this approach is able to link the physicochemical properties of ENMs to toxicity that allows the development of structure-activity relationships (SARs). To build this predictive platform, extensive analytical and bioanalytical techniques and tools are required. In this review, we described the predictive toxicology approach and the accompanying analytical and bioanalytical techniques. In addition, we elaborated several successful examples as a result of using the predictive approach.
Keywords: Engineered nanomaterials; Predictive toxicological paradigm; Analytical technique and bioanalytical assays; High-throughput screening; Nanostructure-activity relationships

How to accurately predict solution-phase gold nanostar stability by Wenjing Xi; Hoa T. Phan; Amanda J. Haes (6113-6123).
earned both B.S. and M.S. degrees in Pharmaceutical Engineering from East China University of Science and Technology and is currently a Ph.D. candidate in the Chemistry Department at the University of Iowa under the direction of Prof. Amanda J. Haes. Her research focuses on improving the detectability of low concentrations of small molecules in complex samples using novel materials design and understanding how solution composition and molecular adsorption influences the magnitude and reproducibility of the SERS signal. earned a B.S. degree in Chemistry from Hanoi University of Science, Vietnam National University, and is currently a Ph.D. candidate in the Chemistry Department at the University of Iowa under the direction of Prof. Amanda J. Haes. His research focuses on investigating the influence of pH and molecular protonation on chemical enhancements using plasmonic materials stabilized in microporous silica membranes and improving the reproducibility in SERS detection of uranyl on flexible substrates. is Associate Professor in the Chemistry Department and Associate Director of the Nanoscience and Nanotechnology Institute at the University of Iowa. She focuses her research efforts on a number of key issues related to nanoscience and nanotechnology including understanding nanomaterial design, measuring and modeling how intermolecular forces influence interfacial phenomena in plasmonics and SERS, as well as applying these materials in biological, chemical, dental, environmental, and radiological applications. Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles are dispersed in various solvents and matrices. While extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory has been successfully applied to predict nanoparticle stability in solution, this model fails to accurately predict the physical stability of anisotropic nanostructures; thus limiting its applicability in practice. Herein, DLVO theory was used to accurately predict gold nanostar stability in solution by investigating how the choice of the nanostar dimension considered in calculations influences the calculated attractive and repulsive interactions between nanostructures. The use of the average radius of curvature of the nanostar tips instead of the average radius as the nanostar dimension of interest increases the accuracy with which experimentally observed nanoparticle behavior can be modeled theoretically. This prediction was validated by measuring time-dependent localized surface plasmon resonance (LSPR) spectra of gold nanostars suspended in solutions with different ionic strengths. Minimum energy barriers calculated from collision theory as a function of nanoparticle concentration were utilized to make kinetic predictions. All in all, these studies suggest that choosing the appropriate gold nanostar dimension is crucial to fully understanding and accurately predicting the stability of anisotropic nanostructures such as gold nanostars; i.e., whether the nanostructures remain stable and can be used reproducibly, or whether they aggregate and exhibit inconsistent results. Thus, the present work provides a deeper understanding of internanoparticle interactions in solution and is expected to lead to more consistent and efficient analytical and bioanalytical applications of these important materials in the future. Graphical abstractᅟ
Keywords: Gold nanostars; Size; Stability; DLVO theory

has just completed his Ph.D. in Chemical and Environmental Engineering from the University of California, Riverside. His research area focuses on nanoparticle interactions in microbially driven environments such as that found in biological water treatment systems. He is additionally interested in developing student-centered strategies for engineering education that ease the learning process. is a project scientist in the Bourns College of Engineering at the University of California, Riverside. His research focuses on changes to dynamic biological systems post-external perturbations, and developing student-centric curriculum in engineering. is the John Babbage Chair in Environmental Engineering and Professor of Chemical and Environmental Engineering at the University of California, Riverside, and Fellow of the Association for Environmental Engineering and Science Professors. Her work applies fundamental colloid science, chemical, and environmental engineering concepts to challenges in water treatment as it applies to water treatment, reuse, and food safety. Engineered nanomaterials (ENMs) are commonly incorporated into food and consumer applications to enhance a specific product aspect (i.e., optical properties). Life cycle analyses revealed ENMs can be released from products during usage and reach wastewater treatment plants (WWTPs), with titanium dioxide (TiO2) accounting for a large fraction. As such, food grade (FG) TiO2, a more common form of TiO2 in wastewater, was used in this study. Nanomaterials in WWTPs have been well characterized, although the problematic septic system has been neglected. Elution and bioaccumulation of TiO2 ENMs from WTTPs in downriver sediments and microorganisms has been observed; however, little is known about mechanisms governing the elution of FG TiO2 from the septic drainage system. This study characterized the transport behavior and mechanisms of FG TiO2 particles in porous media conditions after septic waste treatment. FG and industrial grade (IG) TiO2 (more commonly studied) were introduced to septic tank effluent and low-ionic strength electrolyte solutions prior to column transport experiments. Results indicate that FG TiO2 aggregate size (200–400 nm) remained consistent across solutions. Additionally, elution of FG and IG TiO2 was greatest in septic effluent at the higher nanoparticle concentration (100 ppm). FG TiO2 was well retained at the low (2 ppm) concentration in septic effluent, suggesting that particles that escape the septic system may still be retained in drainage field before reaching the groundwater system, although eluted particles are highly stabilized. Findings provide valuable insight into the significance of the solution environment at mediating differences observed between uniquely engineered nanomaterials. Graphical abstract
Keywords: Food grade; Titanium dioxide; Wastewater; Groundwater; Filtration

Comparison of filtration mechanisms of food and industrial grade TiO2 nanoparticles by Chen Chen; Ian M. Marcus; Travis Waller; Sharon L. Walker (6133-6140).
The removal of food and industrial grade titanium dioxide (TiO2) particles through drinking water filtration was assessed via direct visualization of an in situ 2-D micromodel. The goal of this research was to determine whether variances in surface composition, aggregate size, and ionic strength result in different transport and deposition processes in porous media. Food and industrial grade TiO2 particles were characterized by measuring their hydrodynamic diameter, zeta potential, and zero point of charge before introduction into the 2-D micromodel. The removal efficiency as a function of position on the collector surface was calculated from direct visualization measurements. Notably, food grade TiO2 had a lower removal efficiency when compared with industrial grade. The difference in removal efficiency between the two particle types could be attributed to the higher stability (as indicated by the larger zeta potential values) of the food grade particles, which lead to a reduced aggregate size when compared to the industrial grade particles. This removal efficiency trend was most pronounced in the rear stagnation point, due to the high contribution of hydrodynamic forces at that point. It could be inferred from the results presented herein that particle removal strategies should be based on particle aggregate size and surface charge. Graphical abstractᅟ
Keywords: Titanium dioxide; Filtration mechanisms; 2-D micromodel; Stagnation point; Hydrodynamic forces; Removal efficiency

Mussel-inspired 3D fiber scaffolds for heart-on-a-chip toxicity studies of engineered nanomaterials by Seungkuk Ahn; Herdeline Ann M. Ardoña; Johan U. Lind; Feyisayo Eweje; Sean L. Kim; Grant M. Gonzalez; Qihan Liu; John F. Zimmerman; Georgios Pyrgiotakis; Zhenyuan Zhang; Juan Beltran-Huarac; Paul Carpinone; Brij M. Moudgil; Philip Demokritou; Kevin Kit Parker (6141-6154).
Due to the unique physicochemical properties exhibited by materials with nanoscale dimensions, there is currently a continuous increase in the number of engineered nanomaterials (ENMs) used in consumer goods. However, several reports associate ENM exposure to negative health outcomes such as cardiovascular diseases. Therefore, understanding the pathological consequences of ENM exposure represents an important challenge, requiring model systems that can provide mechanistic insights across different levels of ENM-based toxicity. To achieve this, we developed a mussel-inspired 3D microphysiological system (MPS) to measure cardiac contractility in the presence of ENMs. While multiple cardiac MPS have been reported as alternatives to in vivo testing, most systems only partially recapitulate the native extracellular matrix (ECM) structure. Here, we show how adhesive and aligned polydopamine (PDA)/polycaprolactone (PCL) nanofiber can be used to emulate the 3D native ECM environment of the myocardium. Such nanofiber scaffolds can support the formation of anisotropic and contractile muscular tissues. By integrating these fibers in a cardiac MPS, we assessed the effects of TiO2 and Ag nanoparticles on the contractile function of cardiac tissues. We found that these ENMs decrease the contractile function of cardiac tissues through structural damage to tissue architecture. Furthermore, the MPS with embedded sensors herein presents a way to non-invasively monitor the effects of ENM on cardiac tissue contractility at different time points. These results demonstrate the utility of our MPS as an analytical platform for understanding the functional impacts of ENMs while providing a biomimetic microenvironment to in vitro cardiac tissue samples. Graphical AbstractHeart-on-a-chip integrated with mussel-inspired fiber scaffolds for a high-throughput toxicological assessment of engineered nanomaterials
Keywords: Polydopamine; Nanofiber; Microphysiological systems; Cardiotoxicity; Nanotoxicology

Analysis of lipid adsorption on nanoparticles by nanoflow liquid chromatography-tandem mass spectrometry by Ju Yong Lee; Hua Wang; Georgios Pyrgiotakis; Glen M. DeLoid; Zhenyuan Zhang; Juan Beltran-Huarac; Philip Demokritou; Wenwan Zhong (6155-6164).
Nanoparticles (NPs) tend to adsorb matrix molecules like proteins and lipids incubated with biological fluids, forming a biological corona. While the formation and functions of protein corona have been studied extensively, little attention has been paid to lipid adsorption on NPs. However, lipids are also abundantly present in biological fluids and play important roles in processes like cell signaling and angiogenesis. Therefore, in this study, we established the analytical procedure for study of lipid adsorption on three different types of NPs in two matrices: human serum and heavy cream, using nanoflow liquid chromatography-mass spectrometry (nanoflowLC-MS). Serum was chosen to represent the common environment the NPs would be present once entering human body, and heavy cream was the representative food matrix NPs may be added to improve the color or taste. Steps of liquid-liquid extraction were established and optimized to achieve maximum recovery of the adsorbed, standard lipids from the NPs. Then, the LC-MS/MS method was developed to attain base-line separation of the standard lipids that represent the major lipid classes. At last, the lipid adsorption profiles of the three NPs were compared. We found that the lipid adsorption profile on the same type of NP was significantly different between the two matrices. The established method will help us investigate lipid adsorption on additional NPs and reveal how it could be affected by the physiochemical properties of NPs and the presence of proteins and other components in the biological matrix.
Keywords: TiO2 nanoparticle; Polystyrene nanoparticle; Cellulose nanofibrils; Lipid adsorption; Serum; Heavy cream; LC-MS/MS

A complementary forensic ‘proteo-genomic’ approach for the direct identification of biological fluid traces under fingernails by Sathisha Kamanna; Julianne Henry; Nico Voelcker; Adrian Linacre; K. Paul Kirkbride (6165-6175).
Violent contact between individuals during a crime can result in body fluids becoming trapped under the fingernails of the individuals involved. The traces under fingernails represent valuable forensic evidence because DNA profiling can indicate from whom the trace originated and proteomic methods can be used to determine the type of fluid in the trace, thus providing evidence as to the circumstances surrounding the crime. Here, we present an initial study of an analytical strategy that involves two complementary techniques, direct PCR DNA profiling and direct mass spectrometry-based protein biomarker detection, for the comprehensive examination of traces of biological fluids gathered from underneath fingernails. With regard to protein biomarker detection, direct MALDI-ToF MS/MS is very sensitive, allowing results to be obtained from biological material present on only a few fibres plucked from a microswab used to collect the traces. Human cornulin, a protein biomarker for vaginal fluid, could be detected up to 5 h after it had been deposited under fingernails whereas haemoglobin, a biomarker for blood, is somewhat more persistent under fingernails and could be detected up to 18 h post-deposition. Bottom-up tandem mass spectrometry techniques were used to provide a high level of confidence in assigning the identity of protein biomarkers. nLC-ESI-qToF MS/MS offered higher levels of confidence and the ability to detect traces that had been present under fingernails for longer periods of time, but this performance came with the cost of longer analysis time and a more laborious sampling approach. Graphical abstractᅟ
Keywords: Forensic science; Haemoglobin; Vaginal fluid; MALDI-TOF MS

Graphene oxide-based biosensing platform for rapid and sensitive detection of HIV-1 protease by Youwen Zhang; Xiaohan Chen; Golbarg M. Roozbahani; Xiyun Guan (6177-6185).
HIV-1 protease is essential for the life cycle of the human immunodeficiency virus (HIV), and is one of the most important clinical targets for antiretroviral therapies. In this work, we developed a graphene oxide (GO)-based fluorescence biosensing platform for the rapid, sensitive, and accurate detection of HIV-1 protease, in which fluorescent-labeled HIV-1 protease substrate peptide molecules were covalently linked to GO. In the absence of HIV-1 protease, fluorescein was effectively quenched by GO. In contrast, in the presence of HIV-1 protease, it would cleave the substrate peptide into short fragments, thus producing fluorescence. Based on this sensing strategy, HIV-1 protease could be detected at as low as 1.18 ng/mL. More importantly, the sensor could successfully detect HIV-1 protease in human serum. Such GO-based fluorescent sensors may find useful applications in many fields, including diagnosis of protease-related diseases, as well as sensitive and high-throughput screening of drug candidates. Graphical abstractᅟ
Keywords: HIV-1 protease; Graphene oxide; Biosensing; Human serum

Matrix-free laser desorption ionization mass spectrometry as a functional tool for the analysis and differentiation of complex phenolic mixtures in propolis: a new approach to quality control by Andreas Schinkovitz; Séverine Boisard; Ingrid Freuze; Junichi Osuga; Norbert Mehlmer; Thomas Brück; Pascal Richomme (6187-6195).
Matrix-free laser desorption ionization (LDI) is a rapid and versatile technique for the ionization of small, UV-light-absorbing molecules. Indeed, many natural products such as polyphenols exhibit inherent LDI properties, potentially facilitating their detection from highly complex samples such as crude extracts. With this in mind, the present work thoroughly evaluated the potential of LDI as an analytical tool for the chemical profiling and differentiation of propolis samples obtained from different global regions. Propolis is a complex bee product containing, among others, significant amounts of phenolic constituents that may show LDI effects. The present work will demonstrate that LDI not only provides reproducible and highly specific fingerprint spectra for each of the tested samples, it further allows their clear differentiation by principal compound analysis (PCA). Contrary to classical analytical approaches such as LC- or GC-MS, LDI does not require time-consuming sample preparation and method optimization procedures. Thus, the technique represents a most interesting analytical tool and potent supplement to classic LC-MS for quality control of herbal pharmaceuticals and dietary supplements. Present results clearly support this approach and further suggest the use of LDI as a versatile tool for the automated analysis of large sample batches on an industrial scale. Graphical abstractᅟ
Keywords: Matrix-free laser desorption ionization; Repeatability; Chemical profiling; Propolis; Principal compound analysis; Dereplication

Magnetic-assisted biotinylated single-chain variable fragment antibody-based immunoassay for amantadine detection in chicken by Sanlei Xie; Kai Wen; Jie Xie; Yongjun Zheng; Tao Peng; Jianyi Wang; Kai Yao; Shuangyang Ding; Haiyang Jiang (6197-6205).
A sensitive competitive immunoassay with simple operation was developed for the detection of the anti-virus drug amantadine (AMD). The single-chain variable fragment (scFv) antibody against AMD was site-specific biotinylated and overexpressed as a secreted body in Escherichia coli AVB101. Horseradish peroxidase-labeled streptavidin-biotinylated scFv antibody (HRP-SA-BIO-scFv) could specifically bind to AMD-functionalized magnetic beads (MBs) and then the immune complexes were separated from the matrix solution by magnet. The concentration of the AMD could be known by the measurement of the signal produced by the horseradish peroxidase. The newly established assay provides a significant improvement in comparison to the conventional ELISA without SA-BIO signal amplification and MBs separation. The limit of detection and assay time was 0.64 vs. 8.4 ng/mL and 50 vs. 150 min, respectively. The recoveries ranged from 77.8 to 112% with the coefficient of variation less than 13%. The immunoassay exhibited an obvious cross-reactivity to rimantadine (84%), 1-(1-adamantyl)ethylamine (72%), and somantadine (63%). These results demonstrated that the developed immunoassay provided a sensitive, rapid, and accurate approach for the detection of AMD in chicken by employing MBs as solid phase and SA-BIO as signal amplification. When applied in natural chicken samples, the newly established method provided results consistent with those from UPLC-MS/MS, suggesting that the proposed method could be used for rapid screening of the target of interest; the new immunoassay could also be extended to other small molecular contaminants and thus represents a universal strategy for food safety analysis. Graphical abstractᅟ
Keywords: Immunoassay; Biotinylated scFv; Magnetic beads; Amantadine; Chicken

Four pyrethroids (PYRs), metofluthrin, profluthrin, tefluthrin, and transfluthrin, which were newly developed and have relatively high vapor activity at ambient temperature, are now playing a key role in safely controlling insects in our daily lives. We developed a sensitive and high-throughput determination method for urinary metabolites derived from the newly developed PYR, e.g., 2,3,5,6-tetrafluoro-1,4-benzenedimethanol (HOCH2-FB-Al), 2,3,5,6-tetrafluorobenzyl alcohol (FB-Al), and other PYR metabolites such as trans-chrysanthemumdicarboxylic acid (trans-CDCA) and 3-phenoxybenzoic acid (3PBA). After high temperature acid hydrolysis of 2 mL urine sample in 24-deep well plate, the PYR metabolites were extracted by semi-automated liquid-liquid extraction with tert-butyl methyl ether. N,O-Bis (trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane or 1,1,1,3,3,3-hexafluoroisopropanol were used for the derivatization of PYR metabolites, and the derivatized metabolites were analyzed separately by GC-MS/MS equipped with dual injector system (DB-5MS and mid- to high-polarity phase Rtx-65 columns). The derivatization and evaporation conditions were mainly optimized for improving sensitivity and reproducibility. The mean within-run day precisions were less than 18.4% (relative standard deviation, %RSD) with low detection limits ranging from 0.01 μg/L for HOCH2-FB-Al to 0.06 μg/L for trans-CDCA. This method was successfully applied to urine samples obtained from 50 3-year-old children with high detection frequencies (e.g., 82% for HOCH2-FB-Al and 84% for FB-Al). This method may be a pivotal tool for developing risk assessment from PYR exposure in the general population.
Keywords: Pyrethroid; Metabolite; GC-MS/MS; Urine

Nitrogen (N) serves as a macronutrient that is essential to plant growth and development, and significantly influences storage protein and starch biosyntheses and, ultimately, grain yield and quality. In this study, we performed the first comparative proteomic analysis of developing wheat grains under high-N conditions using 2D-DIGE and tandem mass spectrometry. High-N fertilizer application caused significant increases in ear number, ear grain number, and grain yield. 2D-DIGE identified 142 differentially accumulated proteins (DAPs) during grain development in the elite Chinese bread wheat cultivar Zhongmai 175, of which 132 (93%) were identified by MALDI-TOF/TOF-MS, representing 92 unique proteins. These proteins are involved mainly in energy, N and protein metabolism, carbon metabolism, and starch biosynthesis. Subcellular localization prediction and fluorescence confocal microscopic analysis showed that the DAPs identified were localized mainly in the cytosol and chloroplast. Principal component analysis (PCA) revealed a greater proteomic difference among grain developmental periods than between the high-N and control groups. Protein–protein interaction analysis highlighted a complex network centered around enzymes involved in energy, N and protein metabolism, and starch biosynthesis. Six key DAP genes showed expression patterns consistent with their protein accumulation trends during grain development. A putative metabolic pathway was proposed, with synergistic regulatory networks of grain storage protein and starch biosyntheses in response to high-N application.
Keywords: Bread wheat; Grain development; High nitrogen; 2D-DIGE; Storage proteins; Starch

Isolation of transferrin by imprinted nanoparticles with magnetic deep eutectic solvents as monomer by Yida Zhang; Huawei Cao; Qiangwei Huang; Xiaoyan Liu; Haixia Zhang (6237-6245).
Transferrin (TrF) is a very important human body glycoprotein and a clinical biomarker which controls the body’s iron ion channels and iron ion balance. Any change in TrF concentration and isoform also reflects the emergence of some diseases. In this work, we prepared magnetic molecularly imprinted nanoparticles (deep eutectic solvent-molecular imprinting polymers [DES-MIPs]) with a deep eutectic solvent (DES) as a functional monomer to separate TrF in human serum. The DES dosage for MIP, pH value, and time for adsorption have been optimized, and these materials show special adsorption properties for TrF. The maximum adsorption capacity (Q max) and dissociation constant K L of the MIP by the Langmuir adsorption curve (R 2 = 0.9949) were 37.5 mg/g and 0.015 g/L, respectively. The imprinting factor of the MIP is 3.50 with relative standard deviation (5.63%). In summary, the use of DES as a functional monomer in molecular imprinting technology provides a novel, efficient, and biocompatible method for the isolation and purification of proteins. Graphical abstractᅟ
Keywords: Deep eutectic solvents; Transferrin; Molecular imprinting; Magnetic nanoparticles

Issues with analyzing noble gases using gas chromatography with thermal conductivity detection by George C. Rhoderick; Michael E. Kelley; Lyn Gameson; Kimberly J. Harris; Joseph T. Hodges (6247-6255).
The noble gases, namely neon, argon, krypton and xenon, have many uses including in incandescent and gas discharge lighting, in plasma televisions, shielding gas in welding, in lasers for surgery and semiconductors, and in magnetic resonance imaging (MRI) of the lungs. When incorporating these noble gases in industries, especially the medical field, it is important to know accurately the composition of the noble gas mixture. Therefore, there is a need for accurate gas standards that can be used to determine the noble gas amount-of-substance fraction in the appropriate mixture application. A recent comparison of mixtures containing four noble gases in a helium balance showed mixed results among National Metrology Institutes. Significant differences, 0.7 to 3.8% relative, were seen in the analytical amount-of-substance assignments versus the gravimetric value of the noble gases in the comparison mixture when using “binary standards”, i.e. neon in helium, argon in helium and krypton in helium, as applied by the National Institute of Standards and Technology. Post-comparison studies showed that when all four noble gases were included in the standards, the agreement between analytical and gravimetric values was within 0.05% relative. Further research revealed that different carrier gases (hydrogen, helium and nitrogen) resulted in varying differences between the analytical and gravimetric values assignments. This paper will discuss the findings of these analytical comparisons. Graphical abstractᅟ
Keywords: Noble gases; Primary standard mixtures; Gas chromatography; Thermal conductivity detection

Measurement of human serum unconjugated estriol without derivatization using liquid chromatography-tandem mass spectrometry candidate reference method and compared with two immunoassays by Xianzhang Huang; Qiaoxuan Zhang; Songbai Zheng; Jianbing Wang; Liqiao Han; Haibiao Lin; Peifeng Ke; Junhua Zhuang; Zhimin (Tim) Cao (6257-6267).
A candidate reference measurement procedure (RMP) for measurement of unconjugated estriol in human serum has been developed and validated. The proposed method is highly reliable and uses isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and requires no derivatization. An appropriate amount of serum was accurately weighed and spiked with an isotopically labeled internal standard. Unconjugated estriol and its internal standard were extracted from serum matrix using liquid-liquid extraction prior to reversed-phase LC-MS/MS. Calibrator bracketing was used to give higher specificity and accuracy for assigning serum level. The accuracy of the candidate RMP was validated by split-sample comparison to established RMPs. The lowest limit of detection (LLoD) and lowest limit of quantification (LLoQ) for developed RMP was estimated to be 0.14 nmol/L and 0.35 nmol/L, respectively. Both intra- and inter-assay imprecisions were ≤2.19% at 1.39, 17.34 and 69.35 nmol/L, respectively. Recoveries were 98.54% to 100.34% and linear response ranged from 0.35 to 173.38 nmol/L. No interference was observed. Biases were 5.6% and 2.8% against the targets of RELA2015A (3.87 nmol/L) and RELA2015B (40.62 nmol/L), respectively. Moreover, the candidate RMP was successfully applied to measure level of unconjugated estriol in serum samples of pregnant women (n = 3) and compared with two immunoassays in clinical laboratory. Our developed method is simple, accurate, and can be used as a candidate RMP to determine total unconjugated estriol level in human serum. Further improvement of certain immunoassays in accuracy and precision is needed. Graphical abstractSelected ion chromatograms by LC-MS/MS using a C18 column for uE3 from a serum sample
Keywords: Estriol; Reference method; Tandem mass spectrometry; Immunoassay

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins and draws great concern in health and food safety. A DNA aptamer against AFB1 having a stem-loop structure shows high binding affinity to AFB1 and promise in assay development for AFB1 detection. Based on the structure-switching property of the aptamer, we report an aptamer fluorescence assay for AFB1 detection. Aptamer with fluorescein (FAM) label at 5′ end was used as affinity ligand, while its short complementary DNA (cDNA) with BHQ1 (black hole quencher 1) label at 3′ end was used as a quencher. In the absence of AFB1, FAM-labeled aptamer hybridized with BHQ1-labeled cDNA, forming a duplex of cDNA and aptamer, resulting in fluorescence quenching of FAM. When AFB1 bound with aptamer, the BHQ1-labeled cDNA was displaced from aptamer, causing fluorescence restoration of FAM. We tested a series of FAM-labeled aptamers and BHQ1-labeled cDNAs with different lengths. The lengths of the aptamer stem and the cDNA, Mg2+ in binding buffer, and temperature had significant influence on the performance of the assay. Under optimized conditions, we achieved sensitive detection of AFB1 by using a 29-mer FAM-labeled aptamer and a 14-mer BHQ1-labeled cDNA, and the detection limit of AFB1 reached 0.2 nM. The maximum fluorescence recovery rate of FAM-labeled aptamer caused by AFB1 was about 69-fold. This method enabled the detection of AFB1 in complex sample matrix, e.g., diluted wine samples and maize flour samples. This aptamer-based fluorescent assay for AFB1 determination shows potential for broad applications. Graphical abstract
Keywords: Aptamer; Aflatoxin; Fluorescence; Sensor; Affinity binding

Chiral and molecular recognition between amino acid and sugar molecules and their implications for chemical evolution were investigated using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. Ultraviolet photodissociation of mass-selected and temperature-controlled gas-phase noncovalent complexes of protonated tryptophan (Trp) and monosaccharide enantiomers, such as aldohexose, aldopentose, and deoxyhexose, was examined as a model for chemical evolution in interstellar molecular clouds. Upon photoexcitation of noncovalent heterochiral H+(l-Trp)(d-aldohexose) complexes, NH2CHCOOH loss from protonated Trp via Cα–Cβ bond cleavage occurred. Conversely, in homochiral H+(l-Trp)(l-aldohexose), the energy absorbed by Trp was released through the detachment of aldohexose, and dissociation of the amino acid was suppressed. In the photodissociation mass spectra of protonated Trp with aldopentose and deoxyhexose, which lacks the OH group of aldohexose, no dissociation of the molecules in the complexes or differences between enantiomers were observed. These results indicate that the OH groups in monosaccharides contribute to enantiomer-selective photodissociation in molecular clouds. The differences observed between enantiomers in the photodissociation mass spectra were applied to distinguishing and quantifying aldohexose enantiomers in solution using l-Trp as a chiral probe. The enantiomeric excesses of aldohexoses in solution could be determined from a single photodissociation mass spectrum by reference to the relative ion intensities for the NH2CHCOOH-elimination product and H+(l-Trp) formed via detachment of aldohexose. This analysis method could also distinguish and quantify two d-aldohexose mixtures, where l-Trp was employed as an isomer probe. Graphical abstractᅟ
Keywords: Enantiomer; Isomer; Molecular evolution; Tandem mass spectrometry; Electrospray ionization

Aromatic formulas in ambient PM2.5 samples from Hong Kong determined using FT-ICR ultrahigh-resolution mass spectrometry by Bin-Yu Kuang; Hoi Sze Yeung; Chi Chung Lee; Stephen M Griffith; Jian Zhen Yu (6289-6304).
Many aromatic compounds (e.g., polycyclic aromatic hydrocarbons (PAHs)) found in atmospheric aerosols are toxic and exist in both unsubstituted and substituted forms. Previous studies have mainly concentrated on investigating unsubstituted PAHs, leaving the substituted compounds largely uncharacterized. This study focuses on detection of both unsubstituted and substituted aromatics in ambient aerosol samples using ultrahigh-resolution mass spectrometry. Aerosol samples collected from roadside, urban, and suburban sites in Hong Kong were characterized by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) coupled with atmospheric pressure photoionization (APPI) or electrospray ionization (ESI). In the APPI+ mode, 166 aromatic CH formulas (i.e., formulas containing C and H only and with a double bond equivalent (DBE) of 4 or higher) were determined through molecular formula calculations based on an accurate m/z determination. Among the determined aromatic CH formulas, 141 are possible alkylated monocyclic aromatic hydrocarbon (MAH) or PAH formulas, and account for ≥ 45% of the total intensity by aromatic CH+ formulas. Both APPI+ and ESI+ are effective in detecting nitroaromatics (i.e., CHO2N1 formulas and DBE ≥ 5). The two ionization modes provide complementary formula coverage, with formulas determined by APPI+ extending to higher DBE and those by ESI+ covering higher carbon numbers. Alkylated nitrobenzene compounds are the most abundant among nitroaromatics, and they, together with alkylated nitro-PAHs, account for > 80% of the total intensity of aromatic CHO2N+ formulas, indicating the importance of these compounds in real aerosol samples. Aromatic CHN+ and CHO+ formulas are also determined, confirming the atmospheric presence of some previously reported O- and N-containing aromatic compounds and revealing new possible formulas. The determination of aromatic organic formulas in this study provides useful guidance for future quantitative analysis of hazardous aromatic compounds. Future work is needed to determine the abundance and to study the toxicity of alkylated MAHs and PAHs outside the 16 US EPA priority PAH compounds. Graphical abstract
Keywords: Aerosols; Particulates; Mass spectrometry; Organic compounds; Trace organic compounds

Recent progress in metabolomics has been aided by the development of analysis techniques such as gas and liquid chromatography coupled with mass spectrometry (GC-MS and LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. The vast quantities of data produced by these techniques has resulted in an increase in the use of machine algorithms that can aid in the interpretation of this data, such as principal components analysis (PCA) and partial least squares (PLS). Techniques such as these can be applied to biomarker discovery, interlaboratory comparison, and clinical diagnoses. However, there is a lingering question whether the results of these studies can be applied to broader sets of clinical data, usually taken from different data sources. In this work, we address this question by creating a metabolomics workflow that combines a previously published consensus analysis procedure ( with PCA and PLS models using uncertainty analysis based on bootstrapping. This workflow is applied to NMR data that come from an interlaboratory comparison study using synthetic and biologically obtained metabolite mixtures. The consensus analysis identifies trusted laboratories, whose data are used to create classification models that are more reliable than without. With uncertainty analysis, the reliability of the classification can be rigorously quantified, both for data from the original set and from new data that the model is analyzing. Graphical abstractᅟ
Keywords: Metabolomics; Reliability; Bootstrap; Uncertainty estimation; Chemometrics; Biomarker discovery

Methodical studies of the simultaneous determination of anions and cations by IC×CE–MS using arsenic species as model analytes by Andrea Beutner; Sebastian Karl Piendl; Stefan Wert; Frank-Michael Matysik (6321-6330).
The separation of the constituents of complex sample mixtures is a challenging task in analytical chemistry. Multidimensional separation systems are widely used to enhance the peak capacity. The comprehensive hyphenation of ion chromatography (IC) and capillary electrophoresis (CE) is promising because the two most important instrumental techniques in ion analysis are combined. In this report a new configuration for capillary anion chromatography is presented enabling the simultaneous IC×CE analysis of anions and cations using a switching valve. Electrospray ionization mass spectrometry (MS) was used for detection. A mixture of organic and inorganic arsenic species served as a model system. The coupling of anion chromatography to CE–MS was done via a modulator enabling periodical injections of the IC effluent into the CE. The injection parameters of the modulator were studied taking into account the complex transport situation. Graphical abstractᅟ
Keywords: Two-dimensional separation; Capillary electrophoresis; Ion chromatography; Electrospray ionization; Mass spectrometry; Arsenic speciation

Carbon quantum dots are becoming powerful fluorophore materials for metal ion analysis. Here, highly passivated green phosphorous and nitrogen co-doped carbon quantum dots (C-dots) were prepared using low-temperature carbonization route. Strong green fluorescence emission around 490 nm and excitation wavelength independent C-dots were obtained. Morphological, surface, and optical properties of the C-dots were characterized. Fluorescence emission of C-dots was quenched selectively by copper ions and restored by adding copper chelators, such as EDTA and sulfide ions. Thus, C-dots were successfully used for direct determination of copper ions. Detection limit as low as 1.5 nM (s/n = 3) was achieved for copper ions. Such a low detection limit is very significant for metal analysis using our proposed facile method and low-cost substrates. Experimental results showed that the prepared C-dots demonstrated high sensitivity and selectivity for Cu2+ ion detection and the method is robust and rugged. Graphical abstractᅟ
Keywords: Carbon quantum dots; Copper; Fluorimetric assay; Phosphorous and nitrogen-doped carbon quantum dots