Matrix solid-phase dispersion coupled with gas chromatography–tandem mass spectrometry for simultaneous determination of 13 organophosphate esters in vegetables Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-28 Qing Luo, Shiyu Wang, Yue Shan, Li-na Sun, Hui Wang
In this study, matrix solid-phase dispersion coupled with gas chromatography–tandem mass spectrometry (GC–MS/MS) was developed for the analysis of 23 organophosphate esters (OPEs) in vegetables. Under the optimal conditions, 0.5 g vegetables was dispersed with use of 2 g Florisil, 2 g anhydrous sodium sulfate, and 0.1 g graphitized carbon black, and it was transferred to an empty solid-phase extraction cartridge. The analytes were eluted with 15 mL n-hexane/acetone (1:1, v/v) and analyzed by GC–MS/MS. The method detection limits and quantitation limits ranged from 0.05 to 0.33 ng/g and from 0.16 to 1.10 ng/g, respectively. The recoveries ranged from 65.1% to 109.1%, and the relative standard deviations were less than 15%. The analysis of eight kinds of vegetables shows that the vegetables had been contaminated by OPEs; the concentrations of the sum of the OPEs ranged from 5.89 to 26.8 ng/g. The proposed method is applicable to analyze OPEs in vegetables.
High-throughput liquid chromatography differential mobility spectrometry mass spectrometry for bioanalysis: determination of reduced and oxidized form of glutathione in human blood Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-28 Sophie Bravo-Veyrat, Gérard Hopfgartner
Currently, the measure of the oxidative stress, from oxidized and reduced glutathione (GSSG and GSH respectively), for large cohorts of samples, is generally limited to spectrometric methods. In this study, a high-throughput assay for GSH after derivatization with N-ethylmaleimide and GSSG in blood sample was developed with an analysis time of 1.5 min. The method combines protein precipitation and a short LC (10-mm length) column where compounds were trapped in front-flush mode and eluted in back-flush mode. This setup is combined with modifier-assisted differential ion mobility spectrometry (DMS, SelexIon) and detection is performed in the selected reaction monitoring mode using positive electrospray ionization. In DMS, various modifiers were investigated including N2, methanol, toluene, ethanol, acetonitrile, and isopropanol to improve assay selectivity. Using EtOH as modifier, the limit of quantification (LOQ) was found to be 0.4 μM for GSSG and 3.2 μM for GS-N-ethylmaleimide (NEM) using a blood volume of 60 μL. The method is linear over a wide dynamic concentration range of 0.4 to 400 μM for GSSG and from 3.2 to 3200 μM for GS-NEM. The inter-assay precision of QC samples were ≤ 6.7%, with accuracy values between 98.3 and 103%. The method was further cross-validated with a LC Hypercarb-DMS-MS/MS method by the analysis of human blood samples. The bias between both assays ranged from − 0.3 to 0.2%.
An assessment of retention behavior for gold nanorods in asymmetrical flow field-flow fractionation Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-09-07 Hind El Hadri, Julien Gigault, Jiaojie Tan, Vincent A. Hackley
Applications of asymmetrical flow field-flow fractionation (AF4) continue to expand rapidly in the fields of nanotechnology and biotechnology. In particular, AF4 has proven valuable for the separation and analysis of particles, biomolecular species (e.g., proteins, bacteria) and polymers (natural and synthetic), ranging in size from a few nanometers to several micrometers. The separation of non-spheroidal structures (e.g., rods, tubes, etc.) with primary dimensions in the nanometer regime, is a particularly challenging application deserving of greater study and consideration. The goal of the present study was to advance current understanding of the mechanism of separation of rod-like nano-objects in the AF4 channel. To achieve this, we have systematically investigated a series of commercially available cetyltrimethylammonium bromide stabilized gold nanorods (AuNRs), with aspect ratios from 1.7 to 10. Results show clearly that the retention time is principally dependent on the translational diffusion coefficient of the AuNRs. Equations used to calculate translational and rotational diffusion coefficients (cylinder and prolate ellipsoid models) yield similarly good fits to experimental data. Well characterized gold nanorods (length and diameter by transmission electron microscopy) can be used as calibrants for AF4 measurements allowing one to determine the aspect ratio of nanorod samples based on their retention times.
A hierarchically porous composite monolith polypyrrole/octadecyl silica/graphene oxide/chitosan cryogel sorbent for the extraction and pre-concentration of carbamate pesticides in fruit juices Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-31 Pattamaporn Klongklaew, Thamolwan Naksena, Proespichaya Kanatharana, Opas Bunkoed
A hierarchically porous structured composite monolith sorbent of polypyrrole-coated graphene oxide and octadecyl silica incorporated in chitosan cryogel (PPY/GOx/C18/chitosan) was synthesized and used as solid-phase extraction sorbent for the determination of carbamate pesticides. Various factors affecting the characteristics of the adsorbents (chemistry of the sorbent, polymerization time, concentrations of graphene oxide and octadecyl silica) and the extraction efficiency using the prepared sorbents, such as sample loading, desorption conditions, sample volume, sample flow rate, sample pH, and ionic strength, were investigated and optimized. Under the optimal conditions of sorbent preparation and extraction, the developed composite monolith sorbent provided wide linear responses from 1.0 to 500 μg L−1 for carbofuran and diethofencarb, from 0.5 to 500 μg L−1 for carbaryl, and from 2.0 to 500 μg L−1 for isoprocarb. The limits of detection using HPLC-UV at 203, 220, and 208 nm were in the range of 0.5–2.0 μg L−1. When the composite monolith sorbent was applied for the pre-concentration and determination of carbamate in fruit juices, good recoveries (84.1–99.5%) were achieved. The developed sorbents were porous and exhibited low back pressure enabling their use at high flow rates during sample loading. Extraction and clean-up were highly efficient, and the good physical and chemical stability of the sorbent enables reuse up to 13 times.
Multi-contrast diffraction enhanced computed laminography at Beijing Synchrotron Radiation Facility Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-31 Jian Fu, Xianhong Shi, Qingxi Yuan, Wanxia Huang, Wei Guo, Peng Peng
Synchrotron radiation X-ray computed tomography (CT) enables nondestructive visualization of 3D morphological and chemical changes inside a sample and has become a powerful analysis tool to monitor reactive parts and their chemical states. However, synchrotron radiation CT imaging of specimens with lateral extensions much larger than the acceptance window of detectors is rather problematic due to strong absorption of X-rays in the lateral directions. On the other hand, X-ray computed laminography (CL) permits 3D imaging of flat samples while X-ray diffraction enhanced imaging (DEI) can provide high-quality results with different imaging contrasts such as absorption, phase and dark-field for samples with weak absorptions. Combining CL and DEI together, we have developed a multi-contrast DEI-CL system at the 4W1A beamline of the Beijing Synchrotron Radiation Facility for this kind of sample. Here we reported its design, implementation, and preliminary experimental results of carbon fiber reinforced polymer laminates with three kinds of imaging contrasts. The results have demonstrated the validity of this DEI-CL system. It will be helpful to push the applications of the state-of-the-art synchrotron radiation methods and instruments towards cutting-edge research.
Imaging of growth factors on a human tooth root canal by surface-enhanced Raman spectroscopy Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-15 Václav Ranc, Radovan Žižka, Zuzana Chaloupková, Juraj Ševčík, Radek Zbořil
Endodontic treatment of immature permanent teeth with necrotic pulp poses several clinical challenges and is one of the most demanding interventions in endodontics. Recently, with new discoveries in the field of tissue engineering, novel treatment protocols have been established. The most promising treatment modality is revascularization, whose integral part is the exposure of collagen matrix and embedded growth factors. However, optimization of the treatment protocol requires a development of analytical procedures able to analyze growth factors directly on the sample surface. In this work, method based on surface-enhanced Raman spectroscopy (SERS) was developed to investigate the influence of the time of the medical treatment using EDTA on exposure and accessibility of the growth factors, namely TGF-ß1, BMP-2, and bFGF on the dentine surface. The nanotags, which consist of magnetic Fe3O4@Ag nanocomposite covalently functionalized by tagged antibodies (anti-TGF-ß1-Cy3, anti-BMP-2-Cy5, and anti-bFGF-Cy7), were employed as a SERS substrate. Each antibody was coupled with a unique label allowing us to perform a parallel analysis of all three growth factors within one analytical run. Developed methodology presents an interesting alternative to a fluorescence microscopy and in contrary allows evaluating a chemical composition and thus minimizing possible false-positive results.
Capillary-based chemiluminescence immunoassay for C-reactive protein with portable imaging device Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-22 Haiying Shen, Rizwanullah Khan, Xiaoqian Wang, Zulan Li, Feng Qu
A capillary-based chemiluminescence immunoassay system using a charge-coupled device (CCD) camera as detector was established in this paper. The fused quartz capillary was easily activated in one step for immobilizing capture antibody, and the chemiluminescence immunoassay was carried out in the capillary in double-antibody sandwich format. Chemiluminescence signals were recorded by the portable imaging device which was installed with the CCD camera and the results were analyzed through gray intensity. The total cost time, which included not only the time for test but also the time for the preparation of experimental materials, was only 2 h. The immunoassay was performed without any complicated or expensive instruments. The consumption of the sample was only 0.8 μL in one test, which was significantly less than other methods. In this work, C-reactive protein (CRP), as a target, was quantitatively detected from 0.3 to 160.0 μg mL−1 with high specificity and low sample volume. The reproducibility and accuracy were tested in clinic human serum samples and shown good results. Thus, this rapid, easy preparation and using, portable immunoassay system indicated its usefulness as a novel technology platform.
Sensitive determination of aldehyde metabolites in exhaled breath condensate using capillary electrophoresis with laser-induced fluorescence detection Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-09-13 Tingting Wang, Dan Luo, Zheyan Chen, Yining Qu, Xiuhua Ma, Jiannong Ye, Qingcui Chu, Dongping Huang
A novel capillary electrophoresis with laser-induced fluorescence detection method has been developed for the analysis of aldehyde metabolism biomarkers for oxidative stress in exhaled breath condensate (EBC), and fluorescein 5-thiosemicarbazide was used as a derivatization reagent. In a simple capillary zone electrophoresis mode, ten low molecular weight aldehydes (LMWAs) could be well separated within 30 min. The reaction efficiency was doubled by increasing sample solution pH and magnetic stirring, and the LODs of this method reached 0.16–3.4 nM (S/N = 3). Acceptable recoveries (82.1–115%) were obtained for EBC samples, and the RSD data were within 7.9%. This developed method has been applied for the analyses of EBC samples and evaluation of the correlation between smoking and the contents of aldehyde metabolites in EBC. Due to no need of buffer additives and sample preconcentration, this proposed method may provide an appealing alternative for the trace analyses of LMWAs in noninvasive biofluids.
A critical analysis of L-asparaginase activity quantification methods—colorimetric methods versus high-performance liquid chromatography Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-29 Agnes Magri, Matheus F. Soler, André M. Lopes, Eduardo M. Cilli, Patrick S. Barber, Adalberto Pessoa, Jorge F. B. Pereira
L-asparaginase or ASNase (L-asparagine aminohydrolase, E.C.188.8.131.52) is an enzyme clinically accepted as an antitumor agent to treat acute lymphoblastic leukemia (ALL) and lymphosarcoma through the depletion of L-asparagine (L-Asn) resulting in cytotoxicity to leukemic cells. ASNase is also important in the food industry, preventing acrylamide formation in processed foods. Several quantification techniques have been developed and used for the measurement of the ASNase activity, but standard pharmaceutical quality control methods were hardly reported, and in general, no official quality control guidelines were defined. To overcome this lack of information and to demonstrate the advantages and limitations, this work properly compares the traditional colorimetric methods (Nessler; L-aspartic acid β-hydroxamate (AHA); and indooxine) and the high-performance liquid chromatography (HPLC) method. A comparison of the methods using pure ASNase shows that the colorimetric methods both overestimate (Nessler) and underestimate (AHA and indooxine) the ASNase activity when compared to the values obtained with HPLC, considered the most precise method as this method monitors both substrate consumption and product formation, allowing for overall mass-balance. Correlation and critical analysis of each method relative to the HPLC method were carried out, resulting in a demonstration that it is crucial to select a proper method for the quantification of ASNase activity, allowing bioequivalence studies and individualized monitoring of different ASNase preparations.
Ultrathin ZIF-67 nanosheets as a colorimetric biosensing platform for peroxidase-like catalysis Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-09-01 Shujuan Wang, Dongpo Xu, Lan Ma, Jingxuan Qiu, Xiang Wang, Qingli Dong, Qi Zhang, Jing Pan, Qing Liu
In this work, we report a zeolitic imidazolate framework (ZIF-67) which could catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) to produce a yellow chromogenic reaction. ZIF-67 showed high peroxidase-like activity compared with copper-based metal−organic framework nanoparticles (Cu-MOF), zinc-based metal−organic framework nanoparticles (ZIF-8), and horseradish peroxidase (HPR). We discovered for the first time that the cobalt-based metal−organic framework nanoparticles possess intrinsic peroxidase-like activity without H2O2, which can be employed to quantitatively monitor the H2O2.
Characterization and mapping of secondary metabolites of Streptomyces sp. from caatinga by desorption electrospray ionization mass spectrometry (DESI–MS) Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-09-08 Júlia Pereira Rodrigues, Shamina Saiyara Prova, Luiz Alberto Beraldo Moraes, Demian Rocha Ifa
The discovery of new secondary metabolites is a challenge to biotechnologists due to the emergence of superbugs and drug resistance. Knowledge about biodiversity and the discovery of new microorganisms have become major objectives; thus, new habitats like extreme ecosystems have become places of interest to research. In this context, caatinga is an unexplored biome. The ecosystem caatinga is a rich habitat for thermophilic microbes. Its high temperature and dry climate cause selective microbes to flourish and become established. Actinobacteria (Caat 1-54 genus Streptomyces sp.) isolated from the soil of caatinga was investigated to characterize and map its secondary metabolites by desorption electrospray ionization mass spectrometry imaging (DESI–MSI). With this technique, the production of bioactive metabolites was detected and associated with the different morphological differentiation stages within a typical Streptomyces sp. life cycle. High-resolution mass spectrometry, tandem mass spectrometry, UV–Vis profiling and NMR analysis were also performed to characterize the metabolite ions detected by DESI–MS. A novel compound, which is presumed to be an analogue of the antifungal agent lienomycin, along with the antimicrobial compound lysolipin I were identified in this study to be produced by the bacterium. The potency of these bioactive compounds was further studied by disc diffusion assays and their minimum inhibitory concentrations (MIC) against Bacillus and Penicillium were determined. These bioactive metabolites could be useful to the pharmaceutical industry as candidate compounds, especially given growing concern about increasing resistance to available drugs with the emergence of superbugs. Consequently, the unexplored habitat caatinga affords new possibilities for novel bioactive compound discovery.
Critical assessment of different methods for quantitative measurement of metallodrug-protein associations Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-29 Luis Galvez, Sarah Theiner, Márkó Grabarics, Christian R. Kowol, Bernhard K. Keppler, Stephan Hann, Gunda Koellensperger
Quantitative screening for potential drug–protein binding is an essential step in developing novel metal-based anticancer drugs. ICP–MS approaches are at the core of this task; however, many applications lack in the capability of large-scale high-throughput screenings and proper validation. In this work, we critically discuss the analytical figures of merit and the potential method-based quantitative differences applying four different ICP–MS strategies to ex vivo drug–serum incubations. Two candidate drugs, more specifically, two Pt(IV) complexes with known differences of binding affinity towards serum proteins were selected. The study integrated centrifugal ultrafiltration followed by flow injection analysis, turbulent flow chromatography (TFC), and size exclusion chromatography (SEC), all combined with inductively coupled plasma-mass spectrometry (ICP–MS). As a novelty, for the first time, UHPLC SEC-ICP–MS was implemented to enable rapid protein separation to be performed within a few minutes at > 90% column recovery for protein adducts and small molecules.
A fluorescent material for the detection of chlortetracycline based on molecularly imprinted silica–graphitic carbon nitride composite Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-17 Shengnan Xu, Jie Ding, Ligang Chen
A new fluorescent probe based on graphitic carbon nitride (g-C3N4) combined with molecularly imprinted silica was successfully fabricated and used to selectively recognize chlortetracycline (CTC). The g-C3N4 used in this study has the characteristics of low toxicity and high chemical stability. This synthetic composite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, UV spectroscopy, X-ray diffraction, and fluorescence spectroscopy. The material was used to detect CTC by the fluorescence quenching technique. The fluorescence quenching was due to g-C3N4 and the benzene ring of CTC through π–π electron donor–acceptor interaction and electrostatic force. Hydrogen bonds formed between CTC and 3-aminopropyltriethoxysilane during the polymerization process. Eventually, a considerable amount of selective recognition holes were formed in the composite material and could specifically recognize the template molecule CTC. In addition, the probe strategy was successfully applied to milk analysis, and the recoveries ranged from 90.1% to 95.7%, with relative standard deviations of 1.8–2.8%; the detection limit for CTC was 8 ng mL-1. The results indicate that this method combined the sensitivity of fluorescence detection with the excellent selectivity of a molecularly imprinted polymer. The new material can be widely used in the detection of dairy products.
A sample-in-digital-answer-out system for rapid detection and quantitation of infectious pathogens in bodily fluids Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-29 Haowen Yang, Zhu Chen, Xiaobao Cao, Zhiyang Li, Stavros Stavrakis, Jaebum Choo, Andrew J. deMello, Philip D. Howes, Nongyue He
A variety of automated sample-in-answer-out systems for in vitro molecular diagnostics have been presented and even commercialized. Although efficient in operation, they are incapable of quantifying targets, since quantitation based on analog analytical methods (via standard curve analysis) is complex, expensive, and challenging. To address this issue, herein, we describe an integrated sample-in-digital-answer-out (SIDAO) diagnostic system incorporating DNA extraction and digital recombinase polymerase amplification, which enables rapid and quantitative nucleic acid analysis from bodily fluids within a disposable cartridge. Inside the cartridge, reagents are pre-stored in sterilized tubes, with an automated pipetting module allowing facile liquid transfer. For digital analysis, we fabricate a simple, single-layer polydimethylsiloxane microfluidic device and develop a novel and simple sample compartmentalization strategy. Sample solution is partitioned into an array of 40,044 fL-volume microwells by sealing the microfluidic device through the application of mechanical pressure. The entire analysis is performed in a portable, fully automated instrument. We evaluate the quantitative capabilities of the system by analyzing Mycobacterium tuberculosis genomic DNA from both spiked saliva and serum samples, and demonstrate excellent analytical accuracy and specificity. This SIDAO system provides a promising diagnostic platform for quantitative nucleic acid testing at the point-of-care.
13 C quantification in heterogeneous multiphase natural samples by CMP-NMR using stepped decoupling Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-13 Paris Ning, Ronald Soong, Wolfgang Bermel, Daniel Lane, Myrna J. Simpson, André J. Simpson
Many natural and environmental samples contain combinations of liquids, gels, and solids, yet quantification in the intact state and across multiple phases is highly challenging. Comprehensive multiphase nuclear magnetic resonance (CMP-NMR) combines all the capabilities of high-resolution magic angle spinning (HR-MAS), with the addition of full solids power handling, permitting all phases (i.e., mixtures of liquids, gels, and solids) to be studied and differentiated in intact samples without pre-treatment or extraction. Here, quantification in CMP-NMR is considered. As 1H NMR is considerably broadened in the solid-state, quantification is easier to achieve through 13C which can be observed easily in all the phases. Accurate 13C quantification requires effective 1H decoupling for all the phases, but each phase requires different decoupling conditions. To satisfy these conditions, a pulse sequence termed stepped decoupling is introduced. This sequence can be used to study all components under ideal decoupling conditions resulting in high-resolution spectra without truncation artifacts and provides accurate integrals of components in all phases. The approach is demonstrated on standards and then applied to natural samples including broccoli, soil, and Arabidopsis. The approach permits accurate quantification of chemical categories (for example total carbohydrates) as well as individual species (for example glucose). Further, as the samples are studied intact, volatile species such as methanol and ethylene which are normally hard to detect in plants can be easily quantified in Arabidopsis.
Rapid monitoring of plant growth regulators in bean sprouts via automated on-line polymeric monolith solid-phase extraction coupled with liquid chromatography tandem mass spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-28 Qixun Nian, Lianfeng Ai, Dongmei Li, Xuelei Chen, Lei Zhang, Manman Wang, Xuesheng Wang
An automated on-line solid-phase extraction (SPE) following liquid chromatography tandem mass spectrometry was established for the fast determination of plant growth regulator residues in soybean sprout and mung bean sprout. The crude extracted specimens were directly purified on a poly (2-(dimethylamino) ethyl methacrylate-co-ethylene dimethacrylate) monolithic column which was well-defined as the on-line SPE adsorbent. Under the optimized conditions, the developed method gave the linear range of 0.3–50 ng/mL for gibberellin and 2,4-dichlorophenoxyacetic acid, 0.2–50 ng/mL for 4-chlorophenoxyacetic acid, and 0.5–50 ng/mL for 1-naphthaleneacetic acid (r ≥ 0.998). The detection limits (S/N = 3) ranged from 1.0 to 2.5 μg/kg and the recoveries for spiked soybean sprout samples were in the range of 75.0–93.3%. Besides, the total time for one analysis was 16 min. The reusability of the monolith was up to 600 extractions. The proposed process facilitated fully automated SPE and accurate determination in one step with rapidity, simplicity, and reliability.
A simple, highly sensitive colorimetric immunosensor for the detection of alternariol monomethyl ether in fruit by non-aggregated gold nanoparticles Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-13 Yan Man, Junan Ren, Bingru Li, Xinxin Jin, Ligang Pan
Alternariol monomethyl ether (AME) is one of the major Alternaria mycotoxins present in a wide range of fruits, vegetables, grains, and their products, and possesses the properties of mutagenicity and carcinogenicity. In this study, a simple, rapid, and highly sensitive colorimetric immunosensor based on magnetic nanoparticles (MNPs) was firstly developed for the detection of AME in fruit by nonaggregated gold nanoparticles (GNPs). AME–BSA–Fe3O4 MNP conjugates and free AME molecules in samples competitively bind with monoclonal antibody (mAb)–GNP conjugates. After magnetic separation, the UV absorbance of the nonaggregated GNP supernatant was measured directly. The absorption intensity was proportional to the concentration of AME in the sample. Carboxyl-group-modified AME, AME–bovine serum albumin (BSA) conjugates, anti-AME mAbs, AME–BSA–Fe3O4 MNP conjugates, and mAb–GNP conjugates were prepared and characterized. The effect of GNP sizes (16, 24, and 40 nm) on the colorimetric determination of AME was studied. Under optimized conditions, the limit of detection and the linear range for AME were 0.16 ng/mL and 0.08–0.48 ng/mL, respectively. Moreover, the colorimetric immunosensor developed has lower cross-reactivity with AME analogues. The recoveries of spiked fruits ranged from 80.6% to 90.7%. The colorimetric immunosensor developed provides a promising method for simple, rapid, highly sensitive, and highly specific detection of other mycotoxins in the field of food safety.
IR-MALDESI mass spectrometry imaging of underivatized neurotransmitters in brain tissue of rats exposed to tetrabromobisphenol A Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-13 M. Caleb Bagley, Måns Ekelöf, Kylie Rock, Heather Patisaul, David C. Muddiman
There is a pressing need to develop tools for assessing possible neurotoxicity, particularly for chemicals where the mode of action is poorly understood. Tetrabromobisphenol A (TBBPA), a highly abundant brominated flame retardant, has lately been targeted for neurotoxicity analysis by concerned public health entities in the EU and USA because it is a suspected thyroid disruptor and neurotoxicant. In this study, infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) coupled to a Q Exactive Plus mass spectrometer was used for the analysis of neurotransmitters in the brains of rats exposed to TBBPA in gestation and lactation through their mothers. Three neurotransmitters of interest were studied in three selected regions of the brain: caudate putamen, substantia nigra (SN), and dorsal raphe. Stable isotope labeled (SIL) standards were used as internal standards and a means to achieve relative quantification. This study serves as a demonstration of a new application of IR-MALDESI, namely that neurotransmitter distributions can be confidently and rapidly imaged without derivatization.
New structural insights into the role of TROVE2 complexes in the on-set and pathogenesis of systemic lupus erythematosus determined by a combination of QCM-D and DPI Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-13 Augusto Juste-Dolz, Noelle M. do Nascimento, Isidro Monzó, Elena Grau-García, Jose A. Román-Ivorra, José Luis Lopez-Paz, Jorge Escorihuela, Rosa Puchades, Sergi Morais, David Gimenez-Romero, Ángel Maquieira
The mechanism of self-recognition of the autoantigen TROVE2, a common biomarker in autoimmune diseases, has been studied with a quartz crystal microbalance with dissipation monitoring (QCM-D) and dual polarization interferometry (DPI). The complementarity and remarkable analytical features of both techniques has allowed new insights into the onset of systemic lupus erythematosus (SLE) to be achieved at the molecular level. The in vitro study for SLE patients and healthy subjects suggests that anti-TROVE2 autoantibodies may undergo an antibody bipolar bridging. An epitope-paratope-specific binding initially occurs to activate a hidden Fc receptor in the TROVE2 tertiary structure. This bipolar mechanism may contribute to the pathogenic accumulation of anti-TROVE2 autoantibody immune complex in autoimmune disease. Furthermore, the specific calcium-dependent protein-protein bridges point out at how the TRIM21/TROVE2 association might occur, suggesting that the TROVE2 protein could stimulate the intracellular immune signaling via the TRIM21 PRY-SPRY domain. These findings may help to better understand the origins of the specificity and affinity of TROVE2 interactions, which might play a key role in the SLE pathogenesis. This manuscript gives one of the first practical applications of two novel functions (−df/dD and Δh/molec) for the analysis of the data provided by QCM-D and DPI. In addition, it is the first time that QCM-D has been used for mapping hidden Fc receptors as well as linear epitopes in a protein tertiary structure.
Profiling of nanoparticle–protein interactions by electrophoresis techniques Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-13 Mohammad Zarei, Jamal Aalaie
The use of nanomaterials in the chemical, biomedical, and biotechnological sciences is growing, increasing the possible release of these materials into the environment and contact with living organisms. Because of their large surface area, biomolecules can be adsorbed on the surface of nanomaterials. Proteins bind to the surface of nanoparticles (NPs), forming a biological layer around the NP, the “protein corona,” which gives new characteristics to the NPs in biological milieu and may affect biomedical applications or induce nanotoxicological effects. Therefore, the development of analytical tools for identification of NP protein corona behavior is essential. Techniques such as spectroscopy, chromatography, calorimetry, and electrophoresis have been used to investigate the interaction of NPs with proteins. This review describes recent developments in the application of electrophoresis techniques for profiling of NP–protein interactions. Further, we provide an overview of directions and challenges in the application of electrophoresis methods for the investigation of NP–protein structures.
Quantitative mapping of specific proteins in biological tissues by laser ablation–ICP-MS using exogenous labels: aspects to be considered Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-12 María Cruz-Alonso, Ana Lores-Padín, Eva Valencia, Héctor González-Iglesias, Beatriz Fernández, Rosario Pereiro
Laser ablation (LA) coupled with inductively coupled plasma mass spectrometry (ICP-MS) is a versatile tool for direct trace elemental and isotopic analysis of solids. The development of new strategies for quantitative elemental mapping of biological tissues is one of the growing research areas in LA-ICP-MS. On the other hand, the latest advances are related to obtaining not only the elemental distribution of heteroatoms but also molecular information. In this vein, mapping of specific proteins in biological tissues can be done with LA-ICP-MS by use of metal-labelled immunoprobes. However, although LA-ICP-MS is, in principle, a quantitative technique, critical requirements should be met for absolute quantification of protein distribution. In this review, progress based on the use of metal-labelled antibodies for LA-ICP-MS mapping of specific proteins is reported. Critical requirements to obtain absolute quantitative mapping of specific proteins by LA-ICP-MS are highlighted. Additionally, illustrative examples of the advances made so far with LA-ICP-MS are provided.
Hexagonal cobalt oxyhydroxide nanoflakes/reduced graphene oxide for hydrogen peroxide detection in biological samples Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-11 Xiaoqing Cui, Hong Zhao, Zengxi Li
Abnormal concentration of hydrogen peroxide (H2O2) in blood plasma and cells may lead to several diseases. Thus, it is important to develop a selective and sensitive method to monitor H2O2. In the present work, a novel nonenzymatic H2O2-sensing platform based on cobalt oxyhydroxide (CoOOH)/reduced graphene oxide (RGO) nanocomposite was fabricated. CoOOH nanoflakes were firstly synthesized via soft chemistry routes and then assembled on the surface of RGO. A series of characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy demonstrated that hexagonal CoOOH nanoflakes were well distributed on the surface of RGO. The nanocomposite exhibited excellent electrochemical performance for H2O2 detection. Two linear ranges of 6–200 μM and 200–1500 μM were obtained, and the detection limit was 0.01 μM (signal-to-noise ratio was 3). The good performance was attributed to more exposed catalytic active sites of CoOOH nanoflakes compared with zero-dimensional nanoparticles and outstanding conductivity of RGO as well as their synergistic effect. Moreover, the nanocomposite was used to detect H2O2 from human serum and HeLa cells with satisfactory results.
Tip-enhanced Raman spectroscopy: principles, practice, and applications to nanospectroscopic imaging of 2D materials Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-10 Feng Shao, Renato Zenobi
Two-dimensional (2D) materials have been one of the most extensively studied classes of modern materials, due to their astonishing chemical, optical, electronic, and mechanical properties, which are different from their bulk counterparts. The edges, grain boundaries, local strain, chemical bonding, molecular orientation, and the presence of nanodefects in these 2D monolayers (MLs) will strongly affect their properties. Currently, it is still challenging to investigate such atomically thin 2D monolayers with nanoscale spatial resolution, especially in a label-free and non-destructive way. Tip-enhanced Raman spectroscopy (TERS), which combines the merits of both scanning probe microscopy (SPM) and Raman spectroscopy, has become a powerful analytical technique for studying 2D monolayers, because it allows very high-resolution and high-sensitivity local spectroscopic investigation and imaging and also provides rich chemical information. This review provides a summary of methods to study 2D monolayers and an overview of TERS, followed by an introduction to the current state-of-the-art and theoretical understanding the spatial resolution in TERS experiments. Surface selection rules are also discussed. We then focus on the capabilities and potential of TERS for nanoscale chemical imaging of 2D materials, such as graphene, transition metal dichalcogenides (TMDCs), and 2D polymers. We predict that TERS will become widely accepted and used as a versatile imaging tool for chemical investigation of 2D materials at the nanoscale.
Liquid chromatography–time-of-flight high-resolution mass spectrometry study and determination of the dansylated products of estrogens and their hydroxylated metabolites in water and wastewater Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-10 Luis Honda, Mercedes Becerra-Herrera, Pablo Richter
A method combining liquid chromatography with a dual-probe ultraspray electrospray ionization (ESI) source and time-of-flight high-resolution mass spectrometry (LC-ESI-TOF/MS) was developed for the simultaneous determination of four steroidal sex hormones, estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2), and estriol (E3), as well as five of their hydroxylated metabolites, 2-hydroxyestrone (2-OHE1), 4-hydroxyestrone (4-OHE1), 16α-hydroxyestrone (16-OHE1), 2-hydroxyestradiol (2-OHE2), and 4-hydroxyestradiol (4-OHE2), in water samples in a short chromatographic run of 10 min. Derivatization of the analytes was optimized using dansyl chloride as the derivatizing agent. Under optimal positive ionization conditions, the following signals, which had not been previously reported, were observed (with theoretical values of m/z 377.1373 for 2- and 4-OHE1 and 378.1452 for 2- and 4-OHE2), corresponding to doubly derivatized catechol estrogens in the form of [M+2H]2+. These mass spectrometric signals were more abundant than those reported previously for the [M+H]+ forms of these hydroxylated metabolites. Solid-phase extraction (SPE) with an octadecyl-endcapped sorbent was used to pretreat tap water and effluent from a wastewater treatment plant (WWTP) in Santiago, Chile. The method achieved the simple, fast, and sensitive measurement of nine estrogens with quantitative recoveries (higher than 85.4%). Detection and quantification limits were between 1 and 17 ng L–1 and between 3 and 58 ng L–1, respectively, for all compounds in water. The estrogens E1 and E2 were found in WWTP effluent at concentrations of 7 ± 1 and 41 ± 1 ng L–1, respectively, and EE2 was detected at a concentration below the limit of quantitation. This study shows that the proposed method is suitable for the accurate, rapid, and selective determination of all these analytes at trace levels.
Identification of lignin oligomers in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMS n ) Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-10 Jens Prothmann, Peter Spégel, Margareta Sandahl, Charlotta Turner
Kraft lignin is the main source of technically produced lignin. For the development of valuable products based on Kraft lignin, its molecular structure is important. However, the chemical composition of Kraft lignin is still not well known. So far, the analysis of Kraft lignin by mass spectrometry (MS) has been mainly focused on monomeric compounds. Previous MS studies on lignin oligomers (LOs) considered only synthesised LO standards and/or lignins produced by processes other than the Kraft process. Furthermore, published MS methods suffer from using high resolution only in the MS1 stage in multiple-stage tandem MS methods. A high resolution in all MSn stages would provide more detailed information about LO fragmentation pathways. Since lignin samples are complex mixtures of a large number of similar phenolic compounds, the selection of tentative LOs in the MS data is challenging. In this study, we present a method for non-targeted analysis of LOs in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn). A pre-selection strategy for LOs has been established based on a data-dependent neutral loss MS3 method in combination with a principal component analysis-quadratic discriminant analysis classification model (PCA-QDA). The method was optimised using a design of experiments (DOE) approach. The developed approach improved the pre-selection of tentative LOs in complex mixtures. From 587 detected peaks, 36 peaks were identified as LOs.
Disposable amperometric immunosensor for Saccharomyces cerevisiae based on carboxylated graphene oxide-modified electrodes Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-08 Boryana Borisova, Alfredo Sánchez, Paul E. D. Soto-Rodríguez, Abderrahmane Boujakhrout, María Arévalo-Villena, José M. Pingarrón, Ana Briones-Pérez, Concepción Parrado, Reynaldo Villalonga
A sensitive and disposable amperometric immunosensor for Saccharomyces cerevisiae was constructed by using carbon screen-printed electrodes modified with propionic acid-functionalized graphene oxide as transduction element. The affinity-based biosensing interface was assembled by covalent immobilization of a specific polyclonal antibody on the carboxylate-enriched electrode surface via a water-soluble carbodiimide/N-hydroxysuccinimide coupling approach. A concanavalin A-peroxidase conjugate was further used as signaling element. The immunosensor allowed the amperometric detection of the yeast in buffer solution and white wine samples in the range of 10–107 CFU/mL. This electroanalytical device also exhibited low detection limit and high selectivity, reproducibility, and storage stability. The immunosensor was successfully validated in spiked white wine samples.
Balancing metabolome coverage and reproducibility for untargeted NMR-based metabolic profiling in tissue samples through mixture design methods Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-08 Hong Zheng, Zhitao Ni, Aimin Cai, Xi Zhang, Jiuxia Chen, Qi Shu, Hongchang Gao
Untargeted metabolomics attempts to acquire a comprehensive and reproducible set of small-molecule metabolites in biological systems. However, metabolite extraction method significantly affects the quality of metabolomics data. In the present study, we calculated the number of peaks (NP) and coefficient of variation (CV) to reflect metabolome coverage and reproducibility in untargeted NMR-based metabolic profiling of tissue samples in rats under different methanol/chloroform/water (MCW) extraction conditions. Different MCW extractions expectedly generated diverse characteristics of metabolome. Moreover, the classic MCW method revealed tissue-specific differences in the NP and CV values. To obtain high-quality metabolomics data, therefore, we used mixture design methods to optimize the MCW extraction strategy by maximizing the NP value and minimizing the CV value in each tissue sample. Results show that the optimal formulations of MCW extraction were 2:2:8 (ml/mg tissue) for brain sample, 2:4:6 (ml/mg tissue) for heart sample, 1.3:2:8.7 (ml/mg tissue) for liver sample, 4:2:6 (ml/mg tissue) for kidney sample, 2:3:7 (ml/mg tissue) for muscle sample, and 2:4:6 (ml/mg tissue) for pancreas sample. Therefore, these findings demonstrate that different tissue samples need a specific optimal extraction condition for balancing metabolome coverage and reproducibility in the untargeted metabolomics study. Mixture design method is an effective tool to optimize metabolite extraction strategy for tissue samples.
Novel mixed hemimicelles based on nonionic surfactant–imidazolium ionic liquid and magnetic halloysite nanotubes as efficient approach for analytical determination Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-08 Wei Liu, Ruya Wang, Fan Hu, Pinping Wu, Tao Huang, Meriem Fizir, Hua He
The co-adsorption of mixed nonionic surfactant and imidazolium-based ionic liquid, Triton X100 (TX100), with 1-cetyl-3-methylimidazolium bromide (C16mimBr) adsorbed onto the surface of magnetic halloysite nanotubes (MHNTs) was used as an efficient adsorbent for simultaneous determination of amlodipine and nimodipine in urine. The designed adsorbent was characterized by TEM, TGA, FTIR, and DLS analysis methods. All the parameters that influence the extraction efficiency are optimized with the aid of response surface methodology (RSM). The effects of nonionic surfactant TX100 with different structures of ionic-liquid-coated MHNTs were investigated. Under optimum conditions, extraction recoveries of amlodipine and nimodipine were in the range of 73.8–81.2 and 94.3–96.1%, with RSDs (n = 3) of 2.6–5.5% in spiked urine samples, respectively. The adsorption mechanism principal of mixed hemimicelles was discussed in this study. The limit of detection obtained for analytes was < 0.002 μg·mL−1. To our knowledge, this was the first attempt using a mixed hemimicelle solid-phase extraction (SPE) based on MHNTs and nonionic surfactant and imidazolium-based ionic liquid for the simultaneous determination of amlodipine and nimodipine in biological samples.
Simultaneous determination of 14 urinary biomarkers of exposure to organophosphate flame retardants and plasticizers by LC-MS/MS Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-05 Michiel Bastiaensen, Fuchao Xu, Frederic Been, Nele Van den Eede, Adrian Covaci
Organophosphate flame retardants and plasticizers (PFRs) are a group of chemicals widely added to consumer products. PFRs are quickly metabolized in the human body into two types of metabolites, (1) dialkyl and diaryl phosphate esters (DAPs), such as diphenyl phosphate (DPHP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP); and (2) hydroxylated PFRs (HO-PFRs), such as 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) and 2-hydroxyethyl bis(2-butoxyethyl) phosphate (BBOEHEP). Existing analytical methods usually focus on DAPs; therefore, human biomonitoring data on HO-PFRs remain scarce. In this study, an analytical procedure was developed for the simultaneous quantification of multiple PFR metabolites in human urine, covering eight DAPs and six HO-PFRs. Sample preparation was optimized to include all target compounds using Bond-Elut C18 solid-phase extraction cartridges, followed by instrumental analysis based on liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS). Method performance was validated according to established guidelines and satisfactory results were obtained for all metabolites in terms of recovery, linearity, limits of quantification, precision, and accuracy. Recoveries ranged from 87 to 112%. Method detection limits from 0.002 ng/mL for 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-HO-EHDPHP) to 0.66 ng/mL for 4-hydroxyphenyl phenyl phosphate (4-HO-DPHP). Seven PFR metabolites were frequently detected in a small biomonitoring study (n = 14), among them bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), di-n-butyl phosphate (DNBP), 5-HO-EHDPHP, and BBOEHEP. Highest mean concentrations were found for DPHP, 2-ethylhexyl phenyl phosphate (EHPHP), and BCIPHIPP, while 4-HO-DPHP, 5-HO-EHDPHP, and EHPHP were detected in urine for the first time. Overall, the obtained results demonstrate that the developed method can be used for the simultaneous determination of 14 urinary biomarkers of exposure to PFRs.
An investigation into the kinematics of magnetically driven droplets on various (super)hydrophobic surfaces and their application to an automated multi-droplet platform Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-05 Prashant Agrawal, Kyle J. Bachus, Gabrielle Carriere, Phoenix Grouse, Richard D. Oleschuk
Magnetic actuation on digital microfluidic (DMF) platforms may provide a low-cost, less cumbersome alternative for droplet manipulation in comparison to other techniques such as electrowetting-on-dielectric. Precise control of droplets in magnetically driven DMF platforms is achieved using a low-friction surface, magnetically susceptible material/droplet(s), and an applied magnetic field. Superhydrophobic (SH) surfaces offer limited friction for aqueous media as defined by their high water contact angles (WCA) (>150°) and low sliding angles (<10°). The low surface friction of such coatings and materials significantly reduces the force required for droplet transport. Here, we present a study that examines several actuation parameters including the effects of particle and particle-free actuation mechanisms, porous and non-porous SH materials, surface chemistry, droplet speed/acceleration, and the presence of surface energy traps (SETs) on droplet kinematics. Automated actuation was performed using an XY linear stepper gantry, which enabled sequential droplet actuation, mixing, and undocking operations to be performed in series. The results of this study are applied to a quantitative fluorescence-based DNA assay in under 2 min.
Phenotyping the genus Hypericum by secondary metabolite profiling: emodin vs. skyrin, two possible key intermediates in hypericin biosynthesis Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-05 Katarína Kimáková, Andrea Kimáková, Jakub Idkowiak, Maciej Stobiecki, Paweł Rodziewicz, Łukasz Marczak, Eva Čellárová
A wide range of compounds that occur in the genus Hypericum are listed as effective drugs of natural origin. The main biological activities of several Hypericum representatives are due to the presence of naphthodianthrones, phloroglucinols, and other diverse groups of secondary metabolites that synergistically contribute to their therapeutic effects. The regulation of biosynthesis of hypericin as the key bioactive naphthodianthrone remains uncertain. Here, we present liquid chromatography mass spectrometry-based phenotyping of 17 Hypericum species, the results of which suggest an important role for skyrin and its derivatives in the polyketide pathway that leads to hypericin formation. Moreover, we report for the first time the presence of new metabolites in the genus Hypericum that are related to classes of anthraquinones, their derivatives, and phloroglucinols. As skyrin and other species of anthraquinones are rarely found in higher plants but frequently occur in fungal microorganisms, the obtained results suggest that further research on the synthesis pathways of hypericin and the role of anthraquinone derivatives in plant metabolism should be carried out. The fact that these compounds are commonly synthesized in endophytic fungi and perhaps there is some similarity in the metabolic pathways between these organisms should also be investigated.
Alumina/nano-graphite composite as a new nanosorbent for the selective adsorption, preconcentration, and determination of chromium in water samples by EDXRF Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-05 Anna Baranik, Rafal Sitko, Anna Gagor, Beata Zawisza
Obtaining new nanocomposites with sorption properties towards chromium is highly important not only from the environmental point of view but also for developing eco-friendly methods of chromium determination. The potential use of aluminum oxide-coated nano-graphite (Al2O3/nano-G) as a new nanosorbent in ultrasound-assisted dispersive micro-solid-phase extraction (DMSPE) for rapid speciation of trace chromium(III) and chromium(VI) ions in natural water was evaluated. In the developed method, the crucial issue is the new nanocomposite synthesized by coating alumina on a nano-graphite surface with sorption properties. Structural researches of the nanocomposite were carried out by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Raman spectroscopy. Maximum adsorption capacity of Al2O3/nano-G towards Cr(III) was 32.8 mg g−1. The influence of the method’s factors like pH, sample volumes, contact time, coexisting ions, and humic acid on the recovery of chromium was examined. The nanocomposites have been found to be stable and effective as a sorbent in water with high concentrations of selected cations and anions present in water as well as in water of various pH. Al2O3/nano-G is selective for Cr(III) in presence of Cr(VI). Cr(III) was determined by the developed method, total Cr after reduction of Cr(VI) to Cr(III), and Cr(VI) was calculated as the difference between total Cr and Cr(III). After sorption, the nanocomposite with chromium was collected on 5-mm diameter filters and analyzed by energy-dispersive X-ray fluorescence spectrometry (EDXRF) to determine the chromium concentration. The method was characterized by correlation coefficient 0.999, limit of detection (LOD) 0.04 ng mL−1, and relative standard deviation (RSD) 3.5%. Al2O3/nano-G combined with proposed DMSPE/EDXRF was verified by analysis of certificate reference material of natural water (NIST 1640a).
Combined host-guest complex with coffee-ring effect for constructing ultrasensitive SERS substrate for phenformin hydrochloride detection in healthcare products Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-04 Lixia Zhang, Peng Li, Xiangfeng Bu, Jiawei Wu, Xiaolei Zhang, Bing Zhao, Yuan Tian
Phenformin hydrochloride (PHE), once used as a traditional anti-diabetic drug, has now been banned due to significant side effects. However, the phenomenon of the illegal addition of PHE to hypoglycemic healthcare products is still rampant. Thus, the detection of illegally added PHE is urgently needed. Surface-enhanced Raman scattering (SERS) is a promising candidate for this purpose, but the weak affinity between PHE and bare metal (Au or Ag) limits direct SERS detection of PHE. In this paper, we prepared Ag nanoparticles coated with β-cyclodextrin (AgNP@β-CD), which display the coffee-ring effect, that can be used for PHE sensing. β-CD-functionalized nanoparticles could capture the analyte and fix the molecular orientation in the hydrophobic cavity. The coffee-ring effect could improve the SERS effect through a higher concentration of the analyte, higher density of nanoparticles, and more hot spots. The SERS performance of the AgNP@β-CD substrate was characterized by using o-phenylenediamine dihydrochloride as a probe molecule. The excitation wavelength and pH value were optimized. A linear response for PHE detection is in the 7.0 × 10−8–1.0 × 10−6 mol L−1 concentration range, and the limit of detection is as low as 8.0 × 10−9 mol L−1. This AgNP@β-CD coffee-ring effect substrate was applied to the detection of PHE in healthcare products, with recoveries between 95.3 and 105.0% and relative standard deviations of less than 5.16%. It is anticipated that the AgNP@β-CD substrate will also have great potential for the monitoring of other aromatic drugs in healthcare products.
Selective extraction of 3,4-dihydroxybenzoic acid in Ilex chinensis Sims by meticulous mini-solid-phase microextraction using ternary deep eutectic solvent-based molecularly imprinted polymers Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Guizhen Li, Kyung Ho Row
A ternary deep eutectic solvent (TDES) was used as both template and functional monomer in the synthesis of TDES-based molecularly imprinted polymers (TDES-MIPs). A meticulous miniaturized solid-phase microextraction (mini-SPME) method followed by high-performance liquid chromatography (HPLC) were used for the optimal speciation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the needle of a syringe system with response surface methodology (RSM). Under the optimal conditions for the determination of 3,4-DHBA (amount of adsorbent (2 mg), sample volume (1 mL), cycles for adsorption and desorption (6)), the actual extraction amount was 8.46 μg g−1. The limits of detection (LODs, S/N = 3) for 3,4-DHBA in Ilex chinensis Sims were 0.26–0.31 μg mL−1, and the intra-day and inter-day precision (relative standard deviations, n = 4) after spiking with 5 μg mL−1, 100 μg mL−1, and 200 μg mL−1 were both less than 4.21%. The meticulous method (TDES-MIP-mini-SPME) combined with RSM offers a significant advance over existing methods, because of the meticulous operation and excellent selectivity of 3,4-DHBA from complex samples.
Preparation and characterization of large-format macroporous cryogel disks for use in affinity chromatography and biotechnological applications Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Wim Noppe, Roxanne Cordier, Pieter Baatsen, Hans Deckmyn
We have prepared and evaluated larger format phage-bound epoxy-cryogel columns in order to increase the yield of bound target. Freezing thermograms showed that larger column formats (2.5–5 cm diameter) are not usable due to irregular polymerization phenomena. Preparing thin disks of 0.5 cm height with similar diameter proved to be an excellent alternative. Disks could be stacked and run in a chromatographic setup. In this way, we could increase the matrix volume, ligand-binding capacity, and finally the yield of bound target. By increasing the column volume about sevenfold, we observed a 12-fold increase of ligand density and a sevenfold increase in the yield of protein recovery in a column where phages were attached without spacer and a 10- to 34-fold increase in a spacer column, depending on the spacer used.
A signal-on electrochemiluminescence sensor for clenbuterol detection based on zinc-based metal-organic framework–reduced graphene oxide–CdTe quantum dot hybrids Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Xiaoxia Hu, Han Zhang, Shihong Chen, Ruo Yuan, Junhao You
Clenbuterol (CLB) is harmful to human health when used long term, and it has been listed by the World Anti-Doping Agency (WADA). In this work, a novel zinc-based metal-organic frameworks–reduced graphene oxide–CdTe quantum dots (ZnMOF-RGO-CdTe QDs) hybrid was used to construct an electrochemiluminescence (ECL) sensor for detecting CLB. CdTe QDs, loaded by RGO, exhibited an enhanced ECL signal. In addition, the ZnMOFs catalyzed OH• generation by coreactant H2O2, which further strengthened the ECL signal of the CdTe QDs. The integration of ZnMOFs and RGO-CdTe QDs endowed the sensor with high sensitivity for CLB detection. The intensity of the ECL signal increased as the concentration of CLB increased. The linear range of CLB detection was 3.0 × 10−13 M to 6.0 × 10−10 M, and the detection limit was estimated to be 1.0 × 10−13 M. Furthermore, the sensor displayed a good repeatability and stability. The ZnMOF-RGO-CdTe QD hybrids described in this study provide a foundation for the development of new methods of detecting CLB.
Photoelectrochemical immunoassay of lipoprotein-associated phospholipase A 2 via plasmon-enhanced energy transfer between gold nanoparticles and CdS QDs/g-C 3 N 4 Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Dong-Ping Zhang, Ling-E Wang, Xiao-Ying Liu, Zhi-Hua Luo, Lei Zheng, Yun He, Bo Zhang
A facile and feasible photoelectrochemical (PEC) immunoassay based on plasmon-enhanced energy transfer between gold nanoparticles (AuNPs) and CdS quantum dots (QDs)/g-C3N4 nanosheets was developed for the ultrasensitive detection of lipoprotein-associated phospholipase A2 (Lp-PLA2). To construct such a sensing platform, the immunosensor was prepared by immobilizing Lp-PLA2 on a CdS QDs/g-C3N4-modified electrode. A competitive-type immunoreaction was utilized for Lp-PLA2 detection, with AuNP-labeled anti-Lp-PLA2 antibody used as the competitor. Introducing AuNPs with the specific antibody for the antigen target Lp-PLA2 led to heavy quenching of the photocurrent of CdS QDs/g-C3N4 due to the plasmon-enhanced energy transfer between AuNPs and CdS QDs. The quenching efficiency decreased with increasing target Lp-PLA2 concentration. Under optimal conditions, the PEC immunosensor presented a good photocurrent response to the target Lp-PLA2 in the dynamic linear range of 0.01–300 ng mL−1, with a low detection limit of 5.3 pg mL−1. Other biomarkers and natural enzymes did not interfere with response of this system. The reproducibility and accuracy of this method for the analysis of human serum specimens were evaluated, and the results given by the method developed here were found to closely correspond to the results obtained with commercial Lp-PLA2 ELISA kits. Importantly, this protocol offers promise for the development of exciton–plasmon interaction-based PEC detection systems.
Drosophila melanogaster odorant receptors as volatile compound detectors in forensic science: a proof-of-concept study Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Olivia Leitch, Chris Lennard, K. Paul Kirkbride, Alisha Anderson
The ability to detect and identify substances based on the volatile compounds (odors) they emit is relied upon heavily for numerous investigative purposes. Animals have an innate olfactory sensitivity and selectivity that out-performs current instrumentation. This has led to immense interest in their employment as chemical sensors for a range of applications, including forensic science, both as whole organisms and as sensing elements in biosensors. Using electrophysiological and calcium imaging assays, this research examined the response of Drosophila melanogaster olfactory receptors (ORs) to odor compounds significant in forensic science and assessed their potential utility as volatile compound sensors. This investigation illustrated the different sensitivities, selectivities, and sensing features of individual ORs and demonstrated that their employment for detection purposes is feasible. While further research expanding on this study will be required to demonstrate the performance characteristics that an OR-based detection system will ultimately possess, this research provides an encouraging first step towards the goal of utilizing isolated biological ORs as volatile compound sensors in forensic science.
Non-invasive monitoring of blood glucose using optical methods for skin spectroscopy—opportunities and recent advances Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-03 Sven Delbeck, Thorsten Vahlsing, Steffen Leonhardt, Gerald Steiner, H. Michael Heise
Diabetes mellitus is a widespread disease with greatly rising patient numbers expected in the future, not only for industrialized countries but also for regions in the developing world. There is a need for efficient therapy, which can be via self-monitoring of blood glucose levels to provide tight glycemic control for reducing the risks of severe health complications. Advancements in diabetes technology can nowadays offer different sensor approaches, even for continuous blood glucose monitoring. Non-invasive blood glucose assays have been promised for many years and various vibrational spectroscopy-based methods of the skin are candidates for achieving this goal. Due to the small spectral signatures of the glucose hidden among a largely variable background, the largest signal-to-noise ratios and multivariate calibration are essential to provide the method applicability for self-monitoring of blood glucose. Besides multiparameter approaches, recently presented devices based on photoplethysmography with wavelengths in the visible and near-infrared range are evaluated for their potential of providing reliable blood glucose concentration predictions.
Development and validation of an LC-MS/MS assay for the quantification of dolutegravir extracted from human hair Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-02 Craig Sykes, Kimberly Blake, Nicole White, Amanda P Schauer, Bryan B. Guzman, Mackenzie L. Cottrell, Bani Tamraz, Angela D. M. Kashuba
Measurement of drug concentrations in hair provides a non-invasive approach to assess drug adherence. Here, we report on the development and validation of a method for the quantification of the antiretroviral dolutegravir (DTG) extracted from human hair. DTG is extracted from hair samples by sonication and incubation in 50:50 methanol:acetonitrile with 2% formic acid overnight at 40 °C. Following extraction, samples are analyzed by reverse-phase chromatography on a Waters Atlantis T3 (50 × 2.1 mm, 3-μm particle size) column with subsequent detection by electrospray ionization in positive ion mode on an AB Sciex API-5000 triple quadrupole mass spectrometer. The stable, isotopically labeled 13C,d5-DTG is used as an internal standard in the assay. The calibration range is 5–10,000 pg DTG/mL of extraction solvent with the ability to extract between 1 and 10 mg of hair/mL of extraction solvent. The assay was linear, accurate (inter-assay %bias within ± 6.5%), and precise (inter-assay %CV ≤ 10.3%). The assay was successfully used to analyze clinical samples from subjects on DTG regimens. Analysis of clinical samples suggested the potential presence of a degradation product, which was subsequently confirmed to occur with exposure to sunlight. The degradation of DTG could complicate absolute interpretation of clinical results, but the presence of this degradation product is easily evaluated with this assay to aid in data interpretation.
Direct bacteria analysis using laserspray ionization miniature mass spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-02 Siyu Liu, Jia Zuo, Yaowen Lu, Lijuan Gao, Yanbing Zhai, Wei Xu
An atmospheric pressure laserspray ionization mass spectrometry (AP-LSI mini MS) has been developed and employed in the fast analysis of bacteria. Without using surfactants or any extracting methods, 21 foodborne bacteria from 12 genera were directly analyzed. Typical fingerprints of small molecules and lipids were detected and recognized in the mass spectra with high reproducibility. Furthermore, a supervised multivariate statistics method, orthogonal partial least squares (OPLS), was applied, and these bacteria could be differentiated at both genus and species levels. With improved performance in the future, AP-LSI mini MS could be a simple, effective, and fast approach for direct bacteria analysis on the field.
Portable glucose meter: trends in techniques and its potential application in analysis Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-02 Linan Zhang, Chunchuan Gu, Huan Ma, Langlang Zhu, Jiajun Wen, Hanxiao Xu, Hongying Liu, Lihua Li
A blood glucose meter is an electronic medical device used for determining the concentration of glucose in blood. These meters have undergone five phases of development: washed blood glucose meters, wiped blood glucose meters, colorimetric blood glucose meters, electrochemical blood glucose meters, and micro, multiple site blood glucose meters. Thanks to their speed, portability, low cost, and easy operation, blood glucose meters have been widely available for use in clinical diagnosis. Recently, coupling of target recognition elements (antibody–antigen recognition, nucleic acid hybridization, enzyme recognition, and click chemistry) with signal transduction and amplification strategies (glucose-generating enzymes, nicotinamide adenine dinucleotide (NADH)-generating enzymes, encapsulated glucose, nanomaterials, and cyclic amplification of DNA) has allowed various targets to be determined via the relationship between the signal of the blood glucose meter and the concentration of targets. In this paper, a brief review of the development and mechanism of blood glucose meters is given first. Then, more details on the application of blood glucose meters in analysis are described, including biomedical analysis, food analysis, and environmental analysis. Finally, the prospect of future development of blood glucose meters is also discussed.
High-affinity graphene oxide-encapsulated magnetic Zr-MOF for pretreatment and rapid determination of the photosensitizers hematoporphyrin and hematoporphyrin monomethyl ether in human urine prior to UPLC-HRMS Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-02 Xin Hua, Guosheng Gao, Shengdong Pan
In this paper, a high-affinity graphene oxide-encapsulated magnetic Zr-MOF (GO-Mag@Zr-MOF) was synthesized and characterized by SEM, TEM, and XPS for its morphology, structure, and components. Subsequently, the as-prepared GO-Mag@Zr-MOF was, for the first time, employed as magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of photodynamic therapy (PDT) with the photosensitizers hematoporphyrin (Hp) and hematoporphyrin monomethyl ether (HMME) in human urine samples coupled with ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). The synthesized GO-Mag@Zr-MOF revealed excellent adsorption efficiency for Hp and HMME in urine samples. Under optimal conditions, the spiked recoveries of the developed method were in the range of 89.5–105.6% with RSDs less than 10%. The limits of detection (LODs) were found to be 0.036 and 0.042 μg/L for Hp and HMME, respectively, while limits of quantitation (LOQs) were 0.12 and 0.14 μg/L. The proposed method was found to be rapid, effective, sensitive, and accurate for clinical analysis. Moreover, this paper, for the first time, carefully expounded the mass spectrum cracking mechanisms of Hp and HMME.
An adapted isotope dilution 1 H– 13 C heteronuclear single-quantum correlation (ID-HSQC) for rapid and accurate quantification of endogenous and exogenous plasma glucose Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-27 Tao Huang, Lingling Yu, Xiaofang Ma, Kaifeng Hu
A wide variety of methods, such as enzymatic methods, LC-MS, and LC-MS/MS, are currently available for the concentration determination of plasma glucose in studies of diabetes, obesity, exercise, etc. However, these methods rarely discriminate endogenous and exogenous glucose in plasma. A novel NMR strategy for discriminative quantification of the endogenous and exogenous glucose in plasma has been developed using an adapted isotope dilution 1H–13C heteronuclear single-quantum correlation (ID-HSQC) with uniformly 13C-labeled glucose as a tracer of exogenous glucose. This method takes advantage of the distinct 1H–13C chemical shifts of the hemiacetal group of the α-D-glucopyranose and makes use of the 13C–13C one-bond J-coupling (1JCC) in uniformly 13C-labeled glucose to differentiate the 1H–13C HSQC signal of labeled glucose from that of its natural counterpart when data are acquired in high-resolution mode. The molar ratio between the endogenous and exogenous plasma glucose can then be calculated from the peak intensities of the natural and labeled glucose. The accuracy and precision of the method were evaluated using a series of standard mixtures of natural and uniformly 13C-labeled glucose with varied but known concentrations. Application of this method is demonstrated for the quantification of endogenous and exogenous glucose in plasma derived from healthy and diabetic cynomolgus monkeys. The results nicely agree with our previous LC-MS/MS results. Considering the natural abundance of 13C isotope at the level of 1.1% in endogenous glucose, comparable peak intensities of quantitatively measurable signals derived from natural and labeled glucose imply that the ID-HSQC can tolerate a significantly high ratio of isotope dilution, with labeled/natural glucose at ~ 1%. We expect that the ID-HSQC method can serve as an alternative approach to the biomedical or clinical studies of glucose metabolism.
Evaluation of accuracy dependence of Raman spectroscopic models on the ratio of calibration and validation points for non-invasive glucose sensing Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-25 Surya P. Singh, Soumavo Mukherjee, Luis H. Galindo, Peter T. C. So, Ramachandra Rao Dasari, Uzma Zubair Khan, Raghuraman Kannan, Anandhi Upendran, Jeon Woong Kang
Optical monitoring of blood glucose levels for non-invasive diagnosis is a growing area of research. Recent efforts in this direction have been inclined towards reducing the requirement of calibration framework. Here, we are presenting a systematic investigation on the influence of variation in the ratio of calibration and validation points on the prospective predictive accuracy of spectral models. A fiber-optic probe coupled Raman system has been employed for transcutaneous measurements. Limit of agreement analysis between serum and partial least square regression predicted spectroscopic glucose values has been performed for accurate comparison. Findings are suggestive of strong predictive accuracy of spectroscopic models without requiring substantive calibration measurements.
Fluorescent “keep-on” type pharmacophore obtained from dynamic combinatorial library of Schiff bases Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-11 Yudai Tabuchi, Masumi Taki
We established a novel principle for fluorescence detection of a target protein. A low-molecular-weight fluorescent pharmacophore, as a targeted probe, was selected from a dynamic combinatorial library of Schiff bases. The pharmacophore retains its fluorescence when bound to the hydrophobic site of the target, whereas it loses it because of hydrolysis when unbound.
Sulfur speciation by HPLC-ICPQQQMS in complex human biological samples: taurine and sulfate in human serum and urine Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-30 Bassam Lajin, Walter Goessler
The advent of the triple quadrupole technology to the inductively coupled plasma mass spectrometry (ICPMS) technique has allowed a strong improvement in the accuracy and detection limits of ICPMS for non-metal elements such as sulfur by removing major polyatomic interferences. Up to now, there has been no report utilizing this development for sulfur speciation in complex human biological matrices. In the present report, we show the success of HPLC-ICPQQQMS for the simultaneous determination of two major sulfur metabolites, taurine and sulfate, in human urine and serum, by direct injection without the need for sample clean-up. The optimized chromatographic method was validated, tested for robustness, and applied for investigating the intra-individual variability in taurine urinary excretion in eight healthy volunteers over a period of 8 weeks. The limit of detection and limit of quantification for taurine determination was found to be 0.2 and 0.7 pmol, respectively. The concentrations found in the analyzed group of urine samples (n = 64) had a range, mean, and SD of 0.6–99, 20.4, and 23.2 μg mL−1 for taurine, and 115–1373, 616, and 259 μg mL−1 for sulfate. Taurine was found to exhibit a much higher intra-individual variability than sulfate. The developed method can be applied in large-scale epidemiological studies and clinical studies in order to establish the potential cardioprotective effects of taurine.
Quantification of desmosine and isodesmosine using MALDI-ion trap tandem mass spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-31 Pratikkumar Rathod, Manjeet Kaur, Hsin-Pin Ho, Marissa E. Louis, Basant Dhital, Philip Durlik, Gregory S. Boutis, Kevin J. Mark, Jong I. Lee, Emmanuel J. Chang
Desmosine (Des) and isodesmosine (Isodes), cross-linking amino acids in the biomolecule elastin, may be used as biomarkers for various pathological conditions associated with elastin degradation. The current study presents a novel approach to quantify Des and Isodes using matrix-assisted laser desorption ionization (MALDI)-tandem mass spectrometry (MS2) in a linear ion trap coupled to a vacuum MALDI source. MALDI-MS2 analyses of Des and Isodes are performed using stable-isotope-labeled desmosine d4 (labeled-Des) as an internal standard in different biological fluids, such as urine and serum. The method demonstrated linearity over two orders of magnitude with a detection limit of 0.02 ng/μL in both urine and serum without enrichment prior to mass spectrometry, and relative standard deviation of < 5%. The method is used to evaluate the time-dependent degradation of Des upon UV irradiation (254 nm) and found to be consistent with quantification by 1H NMR. This is the first characterized MALDI-MS2 method for quantification of Des and Isodes and illustrates the potential of MALDI-ion trap MS2 for effective quantification of biomolecules. The reported method represents improvement over current liquid chromatography-based methods with respect to analysis time and solvent consumption, while maintaining similar analytical characteristics.
Application of polyethyleneimine-modified attapulgite for the solid-phase extraction of chlorophenols at trace levels in environmental water samples Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-04 Mengsa Chai, Yihui Chen, Rongrong Xuan, Junfeng Ma, Zhenfeng Jin, Tingting Wang, Dan Qiu, Lihua Zhang, Yukui Zhang
A polyethyleneimine (PEI)-modified attapulgite was employed as a new adsorbent for solid-phase extraction (SPE) of chlorophenols (CPs) from environmental water samples. Key factors pivotal to extraction efficiency, such as organic additive, pH, salt, sample loading volume, elution volume, and sample loading flow rate, were investigated. The maximum adsorption capacity of CPs reached 38 mg/g, and the adsorption behavior could be described with the Langmuir isotherm model. The developed SPE procedure was then tested on river water samples. Of this cartridge, 0.4 g could be used to treat up to 100 mL of the water sample, with high recoveries achieved. The limit of detection (S/N = 3) and the limit of quantification (S/N = 10) were in range of 0.08–0.56 and 0.27–1.88 ng/mL, respectively. The mean recoveries of CPs spiked in river water samples ranged from 84.4 to 96.8% with relative standard deviations for the intra-day and inter-day less than 6.30%. The developed SPE method exhibited high sensitivity, high selectivity, excellent accuracy, and good repeatability to the analysis of trace CPs in complicated aqueous matrices.
One-step synthesized flower-like materials used for sensitively detecting amyloid precursor protein Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-06 Chengke Wang, Rong Tan, Qingqing Wang
In this paper, we developed a new method to detect Alzheimer’s disease (AD)-related amyloid precursor protein (APP). A composite material containing horseradish peroxidase (HRP), APP antibody, and Cu3(PO4)2 was synthesized as the biosensor by co-precipitation method. In this competitive immunoassay, APP was first conjugated onto the microplate surface with the help of poly-L-lysine as the coating reagent; the composite materials were then attached onto the microplate through the interaction of APP and antibody; the HRP can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and formed colored species. Therefore, the more APP in the detection solution (free form), the less composite material was combined with the immobilized APP on the microplate, resulting in the production of less colored TMB species. A series of detection parameters were studied, such as the composite material synthesis process, the concentration, and reaction time of different compounds. Our method has higher sensitivity compared with the similar immunoassay without using composite materials (the limits of detection are 0.3 and 3 ng/mL, respectively), and can be used for real samples (human serum) detection. The detection results using our method are consistent with the ELISA results, which is useful for the AD detection.
Self-assembled protein-enzyme nanoflower-based fluorescent sensing for protein biomarker Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-10-01 Yucheng Liu, Bao Wang, Xinghu Ji, Zhike He
Multi-protein (or enzyme) conjugates play a vital role in biosensing due to the integrated function of each component, such as biological recognition and signal amplification. In this work, a green self-assembled method for the synthesis of multi-functional protein-enzyme nanoflowers has been developed, in which no chemical modification and coupling reaction is needed to fabricate the fluorescent signal probe. The self-assembled protein-enzyme conjugates streptavidin (SA) -β-galactosidase (β-Gal)-CaHPO4 nanoflowers load sufficient enzymes without damaging their activity, which meets the requirements of signal tags for biosensing. Through integrated multi-function of biorecognition (SA) and signal amplification (β-Gal), the SA-β-Gal-CaHPO4 hybrid nanoflower-based fluorescent sensor exhibited an ultrasensitive detection of protein biomarker alpha-fetoprotein (AFP), with limits of detection at the fM level. The presented self-assembled strategy can be extensively applied to develop on-demand protein-enzyme conjugates according to the specific requirements in a variety of applications including biosensors, bioimaging, and biomedicine.
Analyte-driven self-assembly of graphene oxide sheets onto hydroxycamptothecin-functionalized upconversion nanoparticles for the determination of type I topoisomerases in cell extracts Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-17 Xu Wang, Xiu-Ping Yan
Type I topoisomerases (TOPOI), a potential diagnostic biomarker and a target for chemotherapeutic agents, play essential roles in DNA replication, transcription, chromosome segregation, and recombination. It is essential to develop analytical methods for accurate detection of TOPOI in biological fluids for early diagnosis of diseases. Here we show an assay for TOPOI on the basis of the target-induced self-assembly of graphene oxide (GO) sheets onto hydroxycamptothecin-functionalized upconversion nanoparticles (HCPT-UCNPs). The dipole-dipole coupling of HCPT-UCNPs (donor) and GO (acceptor) regulated by TOPOI enables Förster resonance energy transfer between the donor and the acceptor. Integration of minimal autofluorescence and highly specific affinity into the developed nanosensor allows reliable detection of TOPOI in the nanomolar range with the detection limit of 0.29 nM. The detection of TOPOI in breast cancer cells with recoveries from 96.3 to 103.7% shows the availability of the proposed assay in complicated samples.
Determination of six benzotriazole ultraviolet filters in water and cosmetic samples by graphene sponge-based solid-phase extraction followed by high-performance liquid chromatography Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-28 Xuemei Wang, Juan Wang, Tongtong Du, Haixia Kou, Xinzhen Du, Xiaoquan Lu
An approach for fabrication of graphene sponge (GS)-based solid-phase extraction (SPE) followed by high-performance liquid chromatography (HPLC) with ultraviolet detection (HPLC-UV) is proposed, which was applied to determine the six benzotriazole UV filters in water and cosmetic samples. Several extraction conditions including type of elution solvent, the volume of elution solvent, and salt effect were optimized. Under the optimum conditions, the GS-SPE-HPLC-UV method shows a low limit of detection (LOD, S/N = 3) of 0.02–0.08 μg L−1 for standard solution, limits of quantification (LOQ, S/N = 10) of 0.07–0.26 μg L−1 for standard solution, wide linear ranges from 20.0 to 1000 μg L−1 for all compounds for standard solution, correlation coefficients (r) of more than 0.999, except for 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (UV-P), and acceptable reproducibility (relative standard deviations, RSDs < 6.5% for intra-day, RSDs < 8.1% for inter-day). The satisfactory recoveries were obtained in the range 89–105% with RSDs lower than 9.8% at the three spiked levels of 20, 50, and 100 μg L−1. Every home-made GS-SPE cartridge can be reused for more than 60 cycles. The method is facile, low-cost, rapid, sensitive, and suitable for the determination of UV filters in water and cosmetics samples.
GDME-based methodology for the determination of free formaldehyde in cosmetics and hygiene products containing formaldehyde releasers Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-30 Pedro Francisco Brandão, Rui Miguel Ramos, José António Rodrigues
Formaldehyde is often applied in the industrial production of different products, such as textiles, insulation materials, or cosmetics, due to its preservative and disinfectant properties. However, formaldehyde is classified by the International Agency for Research on Cancer as carcinogenic, and there are numerous studies about the pernicious health effects that frequent exposure to formaldehyde can pose to human health. In the cosmetic industry, compounds called formaldehyde releasers are added during production, with the intent of releasing small amounts of formaldehyde over time. Although there are many methods available for the determination of formaldehyde, they are usually not suitable for the determination of free formaldehyde in cosmetics with formaldehyde releasers in their composition, as they can promote the accelerated release of formaldehyde. In this work, the gas-diffusion microextraction (GDME) technique was used for the extraction of formaldehyde from cosmetic and personal hygiene products. Acetylacetone was used as the derivatization reagent which was later used for the spectrophotometric determination of formaldehyde. The developed methodology exhibits limits of detection (1.98 mg kg−1) and quantification (6.60 mg kg−1) perfectly adequate for the determination of formaldehyde in these samples. Formaldehyde values between 6.9 ± 0.3 and 365 ± 15 mg kg−1 were found in samples containing the formaldehyde releasers DMDM hydantoin, Diazolidinyl urea, and Bronopol. Furthermore, mass spectrometry studies were performed in order to unbiasedly ensure the presence of formaldehyde in every extract. GDME proved to be an economical, simple, and robust alternative for the extraction of free formaldehyde in personal hygiene and cosmetic samples.
Highly sensitive and specific real-time PCR by employing serial invasive reaction as a sequence identifier for quantifying EGFR mutation abundance in cfDNA Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-20 Zheng Xiang, Ruixuan Wan, Bingjie Zou, Xiemin Qi, Qing Huang, Shalen Kumar, Janet L. Pitman, Guohua Zhou, Qinxin Song
Detection of EGFR mutations in circulating cell-free DNA (cfDNA) is beneficial to monitor the therapeutic effect, tumor progression, and drug resistance in real time. However, it requires that the mutation detection method has the ability to quantify the mutation abundance accurately. Although the next-generation sequencing (NGS) and digital PCR showed high sensitivity for quantifying mutations in cfDNA, the use of expensive equipment and the high-cost hampered their applications in the clinic. Herein, we propose a highly sensitive and specific real-time PCR by employing serial invasive reaction as a sequence identifier for quantifying EGFR mutation abundance in cfDNA (termed as qPCR-Invader). The mutation abundance can be quantified by using the difference of Ct values between mutant and wild-type targets without the need of making a standard curve. The method can quantify a mutation level as lower as 0.1% (10 copies/tube). Thirty-six tissue samples from non-small-cell lung cancer (NSCLC) patients were detected by our method and 14/36 tissues gave EGFR L858R mutation-positive results, whereas ARMS-PCR just identified 12 of L858R mutant samples. The two inconsistent samples were confirmed as L858R mutant by pyrophosphorolysis-activated polymerization method, indicating that qPCR-Invader is more sensitive than ARMS-PCR for mutation detection. The L858R mutation abundances of 19 cfDNA samples detected by qPCR-Invader were close to that from NGS, indicating our method can precisely quantify mutation abundance in cfDNA. The qPCR-Invader just needs a common real-time PCR device to accomplish quantification of EGFR mutations, and the fluorescence probes are universal for any target detection. Therefore, it could be used in most laboratories to analyze mutations in cfDNA.
Superhydrophilic molecularly imprinted polymers based on a single cross-linking monomer for the recognition of iridoid glycosides in Di - huang pills Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-25 Wenhua Ji, Rongyu Wang, Yan Mu, Xiao Wang
An efficient analytical method based on molecularly imprinted solid-phase extraction (MISPE) coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) was established for the determination of iridoid glycosides (IGs) in Di-huang pills. As the solid-phase extraction medium, superhydrophilic molecularly imprinted polymers (MIPs) with high affinity and selectivity to IGs in water media were fabricated using divinyl galactose as a single cross-linking monomer. The structure, porosity, and hydrophilicity of MIPs were characterized. The properties involving dynamic adsorption, kinetic adsorption, and selectivity were evaluated. Under optimal conditions the MISPE-HPLC-DAD based method was applied for loganin, morroniside, cornin, and sweroside determination in three kinds of Di-huang pills. The limits of detection of four IGs were 0.002–0.003 mg g−1. Furthermore, the proposed method exhibited some merits including good linearity, excellent precision, and desirable accuracy. The established MISPE-HPLC-DAD method has great potential for the selective determination of IGs in Chinese patent drugs.
Spectrofluorometric determination of berberine using a novel Au nanocluster with large Stokes shift Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-18 Aoli Wen, Xiaoxiao Peng, Pingping Zhang, Yunfei Long, Huiming Gong, Qingru Xie, Ming Yue, Shu Chen
Berberine hydrochloride (BHC), a natural isoquinoline alkaloid, is widely applied as a an agent in traditional Chinese medicine. Almost all the traditional methods for BHC detection require complicated preprocessing steps or expensive instruments. In this article, we report a simple, rapid, sensitive, and selective method for BHC detection using fluorescent gold nanoclusters (F-AuNCs) as the fluorescent probe with a large Stokes shift of 237 nm. The F-AuNCs prepared with citrate-stabilized stannous chloride and hydrogen tetrachloroaurate(III) as raw materials in an aqueous medium display strong and stable fluorescence at 566 nm. When F-AuNCs are mixed with BHC, the fluorescence of F-AuNCs is effectively quenched. Under optimized conditions, this method allows sensitive and selective measurements of BHC in a concentration ranging from 1.0 × 10-6 to 1.0 × 10-4 mol L-1 with a detection limit of 7.5 × 10-8 mol L-1, which is relatively low among reported spectral methods. This method provides excellent selectivity for the detection of BHC against inorganic anions and natural amino acids. In addition, the BHC content in two different types of berberine tablets was successfully determined by this method and the results showed high accuracy.
Synthesis and application of ratio fluorescence probe for chloride Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-20 Chen Ma, Fengyuan Zhang, Yaya Wang, Xinyue Zhu, Xiaoyan Liu, Chunyan Zhao, Haixia Zhang
As chloride ions (Cl−) play a vital role in maintaining normal physiological activity, detection of chloride ions is quite urgent. Hence, we developed chloride fluorescence probes to highly selectively and sensitively monitor chloride ions. The probe M2 with single emission has a high fluorescence quantum yield (Φ = 45%), and it is capable of quantitative detection of Cl− under physiological conditions (pH = 7.4) and pH = 5.0 with a linear range of 0.1–4.0 mM; nevertheless, it is of the switch-off type. We further synthesized a ratiometric fluorescent probe MY with M2 as raw material, which featured excellent selectivity and anti-interference, and large two-photon cross section (555 GM). The probe is conveniently used to detect Cl− in water samples and biological samples including human sweat, serum, and urine samples, indicating it holds great promise for chloride detection and biological application.
Preparation of copper tetra(N-carbonylacrylic) aminephthalocyanine functionalized zwitterionic-polymer monolith for highly specific capture of glycopeptides Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-25 Wenjuan Zhang, Liyan Jiang, Dongze Wang, Qiong Jia
In this work, poly(glycidyl methacrylate-ethyleneglycol dimethacrylate) monolith functionalized with copper tetra(N-carbonylacrylic) aminephthalocyanine and iminodiacetic acid was successfully synthesized. Owing to hydrogen bonding and hydrophilic interactions, the monolith exhibited good performance for glycopeptide enrichment. When the tryptic digests of horseradish peroxidase were enriched by the developed monolith, a total of 20 glycopeptides could be captured and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis with a detection limit as low as 0.5 fmol μL−1. With the mixture of bovine serum albumin and horseradish peroxidase digests (200:1, m/m) as the sample, 14 glycopeptides were identified after enrichment, showing the high selectivity of the monolith. Moreover, the functionalized monolith exhibited good stability and reproducibility. It was successfully applied to enrich glycopeptides from human serum, demonstrating its potential applications in selective and efficient capture of glycopeptides in complex biological samples.
Detection of organic compounds in impact glasses formed by the collision of an extraterrestrial material with the Libyan Desert (Africa) and Tasmania (Australia) Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-23 Leticia Gómez-Nubla, Julene Aramendia, Silvia Fdez-Ortiz de Vallejuelo, Kepa Castro, Juan Manuel Madariaga
Impact glasses are rich silica melted formed at high temperature and pressure by the impact of an extraterrestrial body on Earth. Here, Libyan Desert glasses (LDGs) and Darwin glasses (DGs) were studied. Two non-destructive analytical techniques were used to detect and characterize organic compounds present in their inclusions: Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS). Phytoliths, humboldtine, palmitic acid, myristic acid, oleic acid, 4-methyl phthalic acid, and S-H stretching vibrations of amino acids were identified. The presence of these particular organic compounds in such materials has not been reported so far, providing information about (a) the ancient matter of the area where the impact glasses were formed, (b) organic matter belonging to the extraterrestrial body which impacted on the Earth, or (c) even to current plant or bacterial life, which could indicate an active interaction of the LDG and DG with the surrounding environment. Moreover, the identification of fullerene allowed us to know a pressure (15 GPa) and temperatures (670 K or 1800–1900 K) at which samples could be subjected.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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