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Showing papers in "Analytical Chemistry in 2011"


Journal ArticleDOI
TL;DR: A high-throughput droplet digital PCR system that enables processing of ∼2 million PCR reactions using conventional TaqMan assays with a 96-well plate workflow is described that will allow researchers to explore complex genetic landscapes, discover and validate new disease associations, and define a new era of molecular diagnostics.
Abstract: Digital PCR enables the absolute quantitation of nucleic acids in a sample. The lack of scalable and practical technologies for digital PCR implementation has hampered the widespread adoption of this inherently powerful technique. Here we describe a high-throughput droplet digital PCR (ddPCR) system that enables processing of ∼2 million PCR reactions using conventional TaqMan assays with a 96-well plate workflow. Three applications demonstrate that the massive partitioning afforded by our ddPCR system provides orders of magnitude more precision and sensitivity than real-time PCR. First, we show the accurate measurement of germline copy number variation. Second, for rare alleles, we show sensitive detection of mutant DNA in a 100 000-fold excess of wildtype background. Third, we demonstrate absolute quantitation of circulating fetal and maternal DNA from cell-free plasma. We anticipate this ddPCR system will allow researchers to explore complex genetic landscapes, discover and validate new disease associat...

2,203 citations


Journal ArticleDOI
TL;DR: As the first review of aptamers on Analytical Chemistry, this work attempts to cover major progresses in bioanalytical applications of aptamer research in the past 2 years.
Abstract: With over 2,000 publications, including about 250 reviews, resulting from a SciFinder search in just a two year period (2009–2010), the field of aptamer research has continuously generated lots of interest in the scientific community. Aptamers, first reported by three groups independently in 1990,1–3 are the artificial single-stranded DNA or RNA sequences (more recently, peptides) that fold into secondary and tertiary structures making them bind to certain targets with extremely high specificity. Owing to the high specific affinity of an aptamer to its target molecule (small molecules, proteins and even entire cells), it is thought to resemble chemical antibodies, with the dissociation constants ranging from nanomolar to picomolar level. Aptamers have a number of unique features which make them a more effective choice than antibodies. First, aptamers can be screened via in vitro process against a synthetic library, making it possible to target any molecules (from small inorganic ions to intact cells), overcoming the limit of having to use cell lines or animals, as is necessary for antibodies. Second, aptamers, once selected, can undergo subsequent amplification through polymerase chain reaction to produce a large quantity with high purity. Third, the simple chemical structure of aptamer makes it easily amendable to further modifications with functional groups according to different purposes. Finally, aptamers are much more stable than antibodies, making them suitable in applications requiring harsh conditions (e.g., high temperature or extreme pH). The applications of aptamers remain very dynamic, with increasing explorations in the fields of biosensing, diagnostics and therapeutics (some aptamer-based applications are illustrated in Figure 1). There have been a numbers of excellent reviews in recent years with different emphases.4–8 Herein, as the first review of aptamers on Analytical Chemistry, we attempt to cover major progresses in bioanalytical applications of aptamers in the past 2 years. Figure 1 The widespread use of aptamers for numerous analytical and biological applications. Bioanalytical applications of aptamers are highlighted in red.

691 citations


Journal ArticleDOI
TL;DR: QCM users are offered a set of guidelines for interpretation and quantitative analysis of QCM data based on a synthesis of well-established concepts rooted in rheological research of the last century and of new results obtained in the last several years.
Abstract: Over the last 2 decades, the quartz crystal microbalance (QCM or QCM-D) has emerged as a versatile tool for investigating soft and solvated interfaces between solid surfaces and bulk liquids becaus...

673 citations


Journal ArticleDOI
TL;DR: This paper presents a practical guide on how to count and size nanoparticles using spICPMS, and an alternative protocol is provided for determining particle size that broadens the applicability of the technique to all types of inorganic nanoparticles.
Abstract: Currently there are few ideal methods for the characterization of nanoparticles in complex, environmental samples, leading to significant gaps in toxicity and exposure assessments of nanomaterials. Single particle-inductively coupled plasma-mass spectrometry (spICPMS) is an emerging technique that can both size and count metal-containing nanoparticles. A major benefit of the spICPMS method is its ability to characterize nanoparticles at concentrations relevant to the environment. This paper presents a practical guide on how to count and size nanoparticles using spICPMS. Different methods are investigated for measuring transport efficiency (i.e., nebulization efficiency), an important term in the spICPMS calculations. In addition, an alternative protocol is provided for determining particle size that broadens the applicability of the technique to all types of inorganic nanoparticles. Initial comparison, using well-characterized, monodisperse silver nanoparticles, showed the importance of having an accurate...

582 citations


Journal ArticleDOI
TL;DR: The determination of the fluorescence quantum yields (QY, Φ(f)) of a series of fluorescent dyes that span the absorption/excitation and emission ranges of 520-900 and 600-1000 nm is reported.
Abstract: The determination of the fluorescence quantum yields (QY, Φ(f)) of a series of fluorescent dyes that span the absorption/excitation and emission ranges of 520-900 and 600-1000 nm is reported. The dyes encompass commercially available rhodamine 101 (Rh-101, Φ(f) = 0.913), cresyl violet (0.578), oxazine 170 (0.579), oxazine 1 (0.141), cryptocyanine (0.012), HITCI (0.283), IR-125 (0.132), IR-140 (0.167), and four noncommercial cyanine dyes with specific spectroscopic features, all of them in dilute ethanol solution. The QYs have been measured relative to the National Institute of Standards and Technology's standard reference material (SRM) 936a (quinine sulfate, QS) on a traceably characterized fluorometer, employing a chain of transfer standard dyes that include coumarin 102 (Φ(f) = 0.764), coumarin 153 (0.544), and DCM (0.435) as links between QS and Rh-101. The QY of Rh-101 has also been verified in direct measurements against QS using two approaches that rely only on instrument correction. In addition, the effects of temperature and the presence of oxygen on the fluorescence quantum yield of Rh-101 have been assessed.

556 citations


Journal ArticleDOI
TL;DR: This paper describes the first approach at combining paper microfluidics with electrochemiluminescent (ECL) detection by analyzing the red pixel intensity in digital images of the ECL emission, and a calibration curve was constructed demonstrating that DBAE could be detected to levels of 250 μM using the phone.
Abstract: This paper describes the first approach at combining paper microfluidics with electrochemiluminescent (ECL) detection. Inkjet printing is used to produce paper microfluidic substrates which are combined with screen-printed electrodes (SPEs) to create simple, cheap, disposable sensors which can be read without a traditional photodetector. The sensing mechanism is based on the orange luminescence due to the ECL reaction of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) with certain analytes. Using a conventional photodetector, 2-(dibutylamino)ethanol (DBAE) and nicotinamide adenine dinucleotide (NADH) could be detected to levels of 0.9 μM and 72 μM, respectively. Significantly, a mobile camera phone can also be used to detect the luminescence from the sensors. By analyzing the red pixel intensity in digital images of the ECL emission, a calibration curve was constructed demonstrating that DBAE could be detected to levels of 250 μM using the phone.

529 citations



Journal ArticleDOI
Fang Wen1, Yanhua Dong1, Lu Feng1, Song Wang1, Sichun Zhang1, Xinrong Zhang1 
TL;DR: A new strategy to construct enzyme functionalized fluorescent gold nanoclusters via a biomineralization process for the detection of hydrogen peroxide is reported, indicating that HRP enzyme remains active and enables catalytic reaction of HRP-Au NCs and H(2)O(2).
Abstract: The fluorescence of metal nanoclusters provides an amusing optic feature to be applied in various fields. However, rational design of dual functional fluorescent metal nanoclusters directed by active enzyme with targeted application remains little explored. In this work, we report a new strategy to construct enzyme functionalized fluorescent gold nanoclusters via a biomineralization process for the detection of hydrogen peroxide. Horseradish peroxidase (HRP) was used as a model functional template to direct the synthesis of fluorescent gold nanoclusters (Au NCs) at physiological conditions to form HRP−Au NCs bioconjugates. We found that the fluorescence of HRP−Au NCs can be quenched quantitatively by adding H2O2, indicating that HRP enzyme remains active and enables catalytic reaction of HRP−Au NCs and H2O2. Upon the addition of H2O2 under optimal conditions, the fluorescence intensity quenched linearly over the range of 100 nM to 100 μM with high sensitivity (LOD = 30 nM, S/N = 3). This study would be po...

503 citations



Journal ArticleDOI
TL;DR: The electron-transfer annihilation of hole-injection and electron-injected carbon dots could mainly account for the CL emission, which sheds new light on the optical properties of the carbon dots.
Abstract: In this work, chemiluminescent (CL) property of the carbon dots in the presence of peroxynitrous acid was studied. Peroxynitrous acid is formed by online mixing of nitrite and acidified hydrogen peroxide. The CL intensity was increased linearly with nitrite concentration in the range from 1.0 × 10–7 M to 1.0 × 10–5 M, and the detection limit was 5.3 × 10–8 M (signal-to-noise ratio of S/N = 3). This method has been successfully applied to the determination of nitrites in pond water, river water, and pure milk, with recoveries in the range of 98%–108%. The CL mechanism of the peroxynitrous acid–carbon dots system was investigated using the CL, ultraviolet–visible light (UV–vis), and electron paramagnetic resonance (EPR) spectra. The electron-transfer annihilation of hole-injected and electron-injected carbon dots could mainly account for the CL emission, which sheds new light on the optical properties of the carbon dots.

405 citations


Journal ArticleDOI
TL;DR: This cell-phone-enabled optofluidic imaging flow cytometer could especially be useful for rapid and sensitive imaging of bodily fluids for conducting various cell counts or rare cell analysis as well as for screening of water quality in remote and resource-poor settings.
Abstract: Fluorescent microscopy and flow cytometry are widely used tools in biomedical sciences. Cost-effective translation of these technologies to remote and resource-limited environments could create new opportunities especially for telemedicine applications. Toward this direction, here we demonstrate the integration of imaging cytometry and fluorescent microscopy on a cell phone using a compact, lightweight, and cost-effective optofluidic attachment. In this cell-phone-based optofluidic imaging cytometry platform, fluorescently labeled particles or cells of interest are continuously delivered to our imaging volume through a disposable microfluidic channel that is positioned above the existing camera unit of the cell phone. The same microfluidic device also acts as a multilayered optofluidic waveguide and efficiently guides our excitation light, which is butt-coupled from the side facets of our microfluidic channel using inexpensive light-emitting diodes. Since the excitation of the sample volume occurs through...

Journal ArticleDOI
TL;DR: The synthesis of new water-soluble, stable, fluorescent Ag clusters via a facile, green method using denatured bovine serum albumin (dBSA) as a stabilizing agent is reported on.
Abstract: Proteins have proven to be particularly attractive as effective ligands in the synthesis of nano- and subnanoscaled materials because of their multiple chelating and functional groups imparting unique functionalities. However, protein-directed fluorescent metal cluster synthesis is still a challenge but a promising area of research. Here, we report on the synthesis of new water-soluble, stable, fluorescent Ag clusters via a facile, green method using denatured bovine serum albumin (dBSA) as a stabilizing agent. The dBSA with its 35 free cysteine residues could contribute to polyvalent interactions with the Ag clusters and serve as effective stabilizing agents for these clusters. The as-prepared Ag clusters showed high fluorescence emission at ∼637 nm and were stable even in 1 M NaCl. The fluorescent Ag clusters were then used in the detection of Hg2+ with high sensitivity and selectivity. The detection limit was 10 nM in the linear range from 10 nM to 5 μM.

Journal ArticleDOI
TL;DR: By taking advantage of the super fluorescence quenching efficiency of GO, the proposed biosensor exhibits a high sensitivity toward the target with a detection limit of 300 pM for Pb(2+), which is lower than previously reported for catalytic beacons.
Abstract: On the basis of the remarkable difference in affinity of graphene (GO) with ssDNA containing a different number of bases in length, we for the first time report a GO–DNAzyme based biosensor for amplified fluorescence “turn-on” detection of Pb2+. A FAM-labeled DNAzyme–substrate hybrid acted as both a molecular recognition module and signal reporter and GO as a superquencher. By taking advantage of the super fluorescence quenching efficiency of GO, our proposed biosensor exhibits a high sensitivity toward the target with a detection limit of 300 pM for Pb2+, which is lower than previously reported for catalytic beacons. Moreover, with the choice of a classic Pb2+-dependent GR-5 DNAzyme instead of 8-17 DNAzyme as the catalytic unit, the newly designed sensing system also shows an obviously improved selectivity than previously reported methods. Moreover, the sensing system was used for the determination of Pb2+ in river water samples with satisfying results.

Journal ArticleDOI
TL;DR: This Review concentrates on the technology behind the third- and fourth-generation sequencing methods: their challenges, current limitations, and tantalizing promise.
Abstract: DNA sequencing is in the throes of an enormous technological shift marked by dramatic throughput increases, a precipitously dropping per-base cost of raw sequence, and an accompanying requirement for substantial investment in large capital equipment in order to utilize the technology. Investigations that were, for most, unreachable luxuries just a few years ago (individual genome sequencing, metagenomics studies, and the sequencing of myriad organisms of interest) are being increasingly enabled, at a rapid pace. This Review concentrates on the technology behind the third- and fourth-generation sequencing methods: their challenges, current limitations, and tantalizing promise. First-generation sequencing encompasses the chain termination method pioneered by Sanger and Coulson1 in 1975 or the chemical method of Maxam and Gilbert in 1976–1977.2 In 1977, Sanger sequenced the first genome, bacteriophage ΦX 174, which is 5375 bases in length.3 These methods and their early history4 have been reviewed in detail previously.5 Four-color fluorescent Sanger sequencing, where each color corresponds to one of the four DNA bases, is the method used by the automated capillary electrophoresis (CE) systems marketed by Applied Biosystems Inc., now integrated into Life Technologies, and by Beckman Coulter Inc. (Table 1).6 The first composite human genome sequence, reported in 2001, was obtained largely using CE, at great cost and with intense human effort over more than a decade.7,8 While the genome reported in 2001 was a work in progress, the availability of an ever-improving “reference” genome is the basis of an ongoing transformation of biological science and remains fundamental to investigations of genotype–phenotype relationships. Considering reports that have appeared (and not appeared) in the literature to date, it could well be that medically meaningful (actionable) insights into complex diseases will require additional types of “personal” genomic data, for instance, tissue-specific mRNA expression profiling and mRNA sequencing, individualized analysis of gene regulatory regions, epigenetic profiling, and high-quality, long-range chromosome mapping to catalog significant deletions, insertions, rearrangements, etc. Correlation of such integrated genomic data sets with comprehensive medical histories for hundreds or thousands of individuals may be what it takes to reach an era of personalized medicine.9–11 Large-scale sequencing centers are now completing the conversion to next-generation sequencers; the Joint Genome Institute (JGI) has retired all of their Sanger sequencing instruments.12 At the other extreme, until small-scale next-generation sequencers can outperform CE on a cost per accurate base called as well as read length, CE systems will likely remain in heavy use for benchtop-scale, targeted sequencing for directed investigations such as quantitative gene expression, biomarker identification, and pathway analysis. Table 1 First- and Second-Generation Sequencing Technologies

Journal ArticleDOI
TL;DR: This is the first time that UCPs and CNPs were employed as a donor-acceptor pair to construct FRET-based biosensors, which utilized both the photophysical merits of U CPs and the superquenching ability of CNPs and thus afforded favorable analytical performances.
Abstract: We presented a new aptamer biosensor for thrombin in this work, which was based on fluorescence resonance energy transfer (FRET) from upconverting phosphors (UCPs) to carbon nanoparticles (CNPs). The poly(acrylic acid) (PAA) functionalized UCPs were covalently tagged with a thrombin aptamer (5′-NH2- GGTTGGTGTGGTTGG-3′), which bound to the surface of CNPs through π–π stacking interaction. As a result, the energy donor and acceptor were taken into close proximity, leading to the quenching of fluorescence of UCPs. A maximum fluorescence quenching rate of 89% was acquired under optimized conditions. In the presence of thrombin, which induced the aptamer to form quadruplex structure, the π–π interaction was weakened, and thus, the acceptor was separated from the donor blocking the FRET process. The fluorescence of UCPs was therefore restored in a thrombin concentration-dependent manner, which built the foundation of thrombin quantification. The sensor provided a linear range from 0.5 to 20 nM for thrombin with...

Journal ArticleDOI
TL;DR: Second Harmonic Generation microscopy has emerged as a powerful new optical imaging modality and its chemical and physical principles are described and current applications in disease diagnostics are highlighted.
Abstract: Second Harmonic Generation microscopy has emerged as a powerful new optical imaging modality. This Feature describes its chemical and physical principles and highlights current applications in disease diagnostics.

Journal ArticleDOI
TL;DR: The as-proposed graphene ECL immunosensor exhibited high sensitivity and specificity on the detection of prostate protein antigen (PSA), a biomarker of prostate cancer that was used as a model and showed excellent correlations with standard chemiluminescence immunoassay.
Abstract: In this work, we report a cathodic electrogenerated chemiluminescence (ECL) of luminol at a positive potential (ca. 0.05 V vs Ag/AgCl) with a strong light emission on the graphene-modified glass carbon electrode. The resulted graphene-modified electrode offers an excellent platform for high-performance biosensing applications. On the basis of the cathodic ECL signal of luminol on the graphene-modified electrode, an ECL sandwich immunosensor for sensitive detection of cancer biomarkers at low potential was developed with a multiple signal amplification strategy from functionalized graphene and gold nanorods multilabeled with glucose oxidase (GOx) and secondary antibody (Ab2). The functionalized graphene improved the electron transfer on the electrode interface and was employed to attach the primary antibody (Ab1) due to it large surface area. The gold nanorods were not only used as carriers of secondary antibody (Ab2) and GOx but also catalyzed the ECL reaction of luminol, which further amplified the ECL s...

Journal ArticleDOI
TL;DR: It is demonstrated that a retention time prediction model can improve metabolite identification on a hydrophilic interaction chromatography-high-resolution mass spectrometry metabolomics platform, allowing identified metabolites to be mapped onto an organism-wide metabolic network, providing opportunities for future studies of cellular metabolism from a global systems biology perspective.
Abstract: Metabolomics is an emerging field of postgenomic biology concerned with comprehensive analysis of small molecules in biological systems. However, difficulties associated with the identification of detected metabolites currently limit its application. Here we demonstrate that a retention time prediction model can improve metabolite identification on a hydrophilic interaction chromatography (HILIC)–high-resolution mass spectrometry metabolomics platform. A quantitative structure retention relationship (QSRR) model, incorporating six physicochemical variables in a multiple-linear regression based on 120 authentic standard metabolites, shows good predictive ability for retention times of a range of metabolites (cross-validated R2 = 0.82 and mean squared error = 0.14). The predicted retention times improved metabolite identification by removing 40% of the false identifications that occurred with identification by accurate mass alone. The importance of this procedure was demonstrated by putative identification ...

Journal ArticleDOI
TL;DR: Both the thickness of the tissue section and the amount of sinapinic acid sublimated per unit area have optimal ranges for maximal protein signal intensity.
Abstract: We have employed matrix deposition by sublimation for protein image analysis on tissue sections using a hydration/recrystallization process that produces high-quality MALDI mass spectra and high-spatial-resolution ion images. We systematically investigated different washing protocols, the effect of tissue section thickness, the amount of sublimated matrix per unit area, and different recrystallization conditions. The results show that an organic solvent rinse followed by ethanol/water rinses substantially increased sensitivity for the detection of proteins. Both the thickness of the tissue section and the amount of sinapinic acid sublimated per unit area have optimal ranges for maximal protein signal intensity. Ion images of mouse and rat brain sections at 50, 20, and 10 μm spatial resolution are presented and are correlated with hematoxylin and eosin (H&E)-stained optical images. For targeted analysis, histology-directed imaging can be performed using this protocol where MS analysis and H&E staining are ...

Journal ArticleDOI
Lingling Li1, Hongying Liu1, Yuanyuan Shen1, Jian-Rong Zhang1, Jun-Jie Zhu1 
TL;DR: The Au NCs could be an effective candidate for new types of ECL biosensors in the future due to their fascinating features, such as good water solubility, low toxicity, ease of labeling, and excellent stability.
Abstract: Electrogenerated chemiluminescence (ECL) emission was observed from the water-soluble, bovine serum albumin (BSA)-stabilized Au nanoclusters for the first time. The possible ECL mechanism was discussed according to the presented results and ascribed to the effective electron transfer from the conduction-band of excited indium tin oxide (ITO) to Au nanoclusters (NCs). A simple label-free method for the detection of dopamine has been developed based on the Au NCs ECL in aqueous media. The Au NCs could be an effective candidate for new types of ECL biosensors in the future due to their fascinating features, such as good water solubility, low toxicity, ease of labeling, and excellent stability.

Journal ArticleDOI
TL;DR: A platform of flow injection electrospray-time-of-flight mass spectrometry to profile small molecules in >1400 biological extracts per day at native mass resolution and presents an exemplary screen with Escherichia coli deletion mutants to show the exquisite capacity of the platform to identify lesions in primary metabolism at high throughputs.
Abstract: Direct injection of samples on high-resolving mass spectrometers is an effective way to maximize analytical throughput and yet allow analyte discrimination in complex samples by mass-to-charge ratio. We present a platform of flow injection electrospray–time-of-flight mass spectrometry to profile small molecules in >1400 biological extracts per day at native mass resolution. We comprehensively benchmark the performance with more than 5000 injections of chemically defined standards and Escherichia coli cellular extracts obtained from miniscale cultivations. For at least 90% of tested compounds, we attain a linear response over 3 decades of concentration, interday coefficient of variation of 1500 distinct ions in each mode. The accurate mass and correlation analysis enabled one to assign with good confidence 400–800 ions to electrospray derivatives of metabolites listed in the genome-wide reconstruction of...

Journal ArticleDOI
TL;DR: The first use of redox nanoparticles of cerium oxide as colorimetric probes in bioanalysis based on changes in the physicochemical properties of ceria nanoparticles, used here as chromogenic indicators, is reported, showing that these particles can be fully integrated in a paper-based bioassay.
Abstract: We report the first use of redox nanoparticles of cerium oxide as colorimetric probes in bioanalysis. The method is based on changes in the physicochemical properties of ceria nanoparticles, used here as chromogenic indicators, in response to the analyte. We show that these particles can be fully integrated in a paper-based bioassay. To construct the sensor, ceria nanoparticles and glucose oxidase were coimmobilized onto filter paper using a silanization procedure. In the presence of glucose, the enzymatically generated hydrogen peroxide induces a visual color change of the ceria nanoparticles immobilized onto the bioactive sensing paper, from white-yellowish to dark orange, in a concentration-dependent manner. A detection limit of 0.5 mM glucose with a linear range up to 100 mM and a reproducibility of 4.3% for n = 11 ceria paper strips were obtained. The assay is fully reversible and can be reused for at least 10 consecutive measurement cycles, without significant loss of activity. Another unique featur...

Journal ArticleDOI
TL;DR: A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed, and the obtained fiber was stable enough for more than 150 replicate extraction cycles and exhibited higher enrichment factors (EFs) than the commercial polydimethylsioxane (PDMS) fiber.
Abstract: A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed. Graphite oxide was first used as starting coating material that covalently bonded to the fused-silica substrate using 3-aminopropyltriethoxysilane (APTES) as cross-linking agent and subsequently deoxidized by hydrazine to give the graphene coating in situ. The chemical bonding between graphene and the silica fiber improve its chemical stability, and the obtained fiber was stable enough for more than 150 replicate extraction cycles. The graphene coating was wrinkled and folded, like the morphology of the rough tree bark. Its performance is tested by headspace (HS) SPME of polycyclic aromatic hydrocarbons (PAHs) followed by GC/MS analysis. The results showed that the graphene-coated fiber exhibited higher enrichment factors (EFs) from 2-fold for naphthalene to 17-fold for B(b)FL as compared to the commercial polydimethylsioxane (PDMS) fiber, and the EFs increased with the number of condensed rings of PAHs. The strong adsorption affinity was believed to be mostly due to the dominant role of π-π stacking interaction and hydrophobic effect, according to the results of selectivity study for a variety of organic compounds including PAHs, the aromatic compounds with different substituent groups, and some aliphatic hydrocarbons. For PAHs analysis, the graphene-coated fiber showed good precision (<11%), low detection limits (1.52-2.72 ng/L), and wide linearity (5-500 ng/L) under the optimized conditions. The repeatability of fiber-to-fiber was 4.0-10.8%. The method was applied to simultaneous analysis of eight PAHs with satisfactory recoveries, which were 84-102% for water samples and 72-95% for soil samples, respectively.

Journal ArticleDOI
TL;DR: The quenching of luminescence of the protein-capped Cu QCs in the presence of very low hydrogen peroxide concentration reflects the efficacy of the QCs as a potential sensing material in biological environments.
Abstract: A one-pot synthesis of extremely stable, water-soluble Cu quantum clusters (QCs) capped with a model protein, bovine serum albumin (BSA), is reported. From matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, we assign the clusters to be composed of Cu5 and Cu13 cores. The QCs also show luminescence properties having excitation and emission maxima at 325 and 410 nm, respectively, with a quantum yield of 0.15, which are found to be different from that of protein alone in similar experimental conditions. The quenching of luminescence of the protein-capped Cu QCs in the presence of very low hydrogen peroxide concentration (approximately nanomolar, or less than part-per-billion) reflects the efficacy of the QCs as a potential sensing material in biological environments. Moreover, as-prepared Cu QCs can detect highly toxic Pb2+ ions in water, even at the part-per-million level, without suffering any interference from other metal ions.

Journal ArticleDOI
TL;DR: The slurry-packed MIL-101(Cr) column for high-performance liquid chromatographic separation of substituted aromatics was reported, allowing fast and selective separation of the ortho-isomer from the other isomers within 3 min using dichloromethane as the mobile phase.
Abstract: The diverse structures and pore topologies, accessible cages and tunnels, and high surface areas make metal–organic frameworks attractive as novel media in separation sciences. Here we report the slurry-packed MIL-101(Cr) column for high-performance liquid chromatographic separation of substituted aromatics. The MIL-101(Cr) packed column (5 cm long × 4.6 mm i.d.) offered high-resolution separation of ethylbenzene (EB) and xylene, dichlorobenzene and chlorotoluene isomers, and EB and styrene. The typical impurities of toluene and o-xylene in EB and styrene mixtures were also efficiently separated on the MIL-101(Cr) packed column. The column efficiencies for EB, m-dichlorobenzene, and m-chlorotoluene are 20000, 13000, and 10000 plates m–1, respectively. The relative standard deviation for five replicate separations of the substituted aromatics was 0.2–0.7%, 0.9–2.9%, 0.5–2.1%, and 0.6–2.7% for the retention time, peak area, peak height, and half peak width, respectively. The MIL-101(Cr) offered high affinit...

Journal ArticleDOI
TL;DR: The PeakML format in particular enables the flexible exchange of processed data between software created by different groups or companies, as it is illustrated by providing a PeakML-based integration of the widely used XCMS package with mzMatch data processing tools.
Abstract: The recent proliferation of high-resolution mass spectrometers has generated a wealth of new data analysis methods. However, flexible integration of these methods into configurations best suited to the research question is hampered by heterogeneous file formats and monolithic software development. The mzXML, mzData, and mzML file formats have enabled uniform access to unprocessed raw data. In this paper we present our efforts to produce an equally simple and powerful format, PeakML, to uniformly exchange processed intermediary and result data. To demonstrate the versatility of PeakML, we have developed an open source Java toolkit for processing, filtering, and annotating mass spectra in a customizable pipeline (mzMatch), as well as a user-friendly data visualization environment (PeakML Viewer). The PeakML format in particular enables the flexible exchange of processed data between software created by different groups or companies, as we illustrate by providing a PeakML-based integration of the widely used...

Journal ArticleDOI
TL;DR: The burgeoning role of QDs in many different fields of bioanalyses is described and the advantages afforded by their unique physical and optical properties are highlighted.
Abstract: Colloidal semiconductor quantum dots (QDs) have evolved beyond scientific novelties and are transitioning into bona fide analytical tools. We describe the burgeoning role of QDs in many different fields of bioanalyses and highlight the advantages afforded by their unique physical and optical properties.

Journal ArticleDOI
TL;DR: The amplified immunoassay developed in this work shows acceptable stability and reproducibility, and the assay results for phospho-p53(392) spiked in human plasma also show good recovery, and this simple and low-cost immunosensor shows great promise for detection of other phosphorylated proteins and clinical applications.
Abstract: P53 phosphorylation plays an important role in many biological processes and might be used as a potential biomarker in clinical diagnoses. We report a new electrochemical immunosensor for ultrasensitive detection of phosphorylated p53 at Ser392 (phospho-p53392) based on graphene oxide (GO) as a nanocarrier in a multienzyme amplification strategy. Greatly enhanced sensitivity was achieved by using the bioconjugates featuring horseradish peroxidase (HRP) and p53392 signal antibody (p53392Ab2) linked to functionalized GO (HRP−p53392Ab2−GO) at a high ratio of HRP/p53392Ab2. After a sandwich immunoreaction, the HRP−p53392Ab2−GO captured onto the electrode surface produced an amplified electrocatalytic response by the reduction of enzymatically oxidized thionine in the presence of hydrogen peroxide. The increase of response current was proportional to the phospho-p53392 concentration in the range of 0.02−2 nM with the detection limit of 0.01 nM, which was 10-fold lower than that of the traditional sandwich elec...

Journal ArticleDOI
TL;DR: DPCR exhibited good analytical sensitivity and was reproducible outside the range recommended by the instrument manufacturer; detecting 16 estimated targets with high precision, and it is demonstrated that preamplification can impose a significant measurement bias.
Abstract: The emerging technique of microfluidic digital PCR (dPCR) offers a unique approach to real-time quantitative PCR for measuring nucleic acids that may be particularly suited for low-level detection. In this study, we evaluated the quantitative capabilities of dPCR when measuring small amounts (<200 copies) of DNA and investigated parameters influencing technical performance. We used various DNA templates, matrixes, and assays to evaluate the precision, sensitivity and reproducibility of dPCR, and demonstrate that this technique can be highly reproducible when performed at different times and when different primer sets are targeting the same molecule. dPCR exhibited good analytical sensitivity and was reproducible outside the range recommended by the instrument manufacturer; detecting 16 estimated targets with high precision. The inclusion of carrier had no effect on this estimated quantity, but did improve measurement precision. We report disagreement when using dPCR to measure different template types and when comparing the estimated quantities by dPCR and UV spectrophotometry. Finally, we also demonstrate that preamplification can impose a significant measurement bias. These findings provide an independent assessment of low copy molecular measurement using dPCR and underline important factors for consideration in dPCR experimental design.

Journal ArticleDOI
TL;DR: Cotton wool microtips are established for glycan and glycopeptide purification with subsequent mass spectrometric detection of IgG and transferrin followed by MALDI-TOF-MS detection.
Abstract: Solid-phase extraction microtips are important devices in modern bioanalytics, as they allow miniaturized sample preparation for mass spectrometric analysis. Here we introduce the use of cotton wool for the preparation of filter-free HILIC SPE microtips. To this end, pieces of cotton wool pads (approximately 500 μg) were packed into 10 μL pipet tips. The performance of the tips was evaluated for microscale purification of tryptic IgG Fc N-glycopeptides. Cotton wool HILIC SPE microtips allowed the removal of salts, most nonglycosylated peptides, and detergents such as SDS from glycoconjugate samples. MALDI-TOF-MS glycopeptide profiles were very repeatable with different tips as well as reused tips, and very similar profiles were obtained with different brands of cotton wool pads. In addition, we used cotton HILIC microtips to purify N-glycans after N-glycosidase F treatment of IgG and transferrin followed by MALDI-TOF-MS detection. In conclusion, we establish cotton wool microtips for glycan and glycopeptide purification with subsequent mass spectrometric detection.