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A solid-contact ion-selective electrode (SC-ISE) based on a covalent organic framework@reduced graphene oxide (rGO) composite is proposed. The composite can be synthesized through the polycondensation of 1,3,5-triformylphloroglucinol (TFP) and 2,6-diaminoanthraquinone (DAAQ) on the rGO nanosheets, which shows high capacitance and good redox-active properties. By applying Cd 2+ -ISE as a model, the electrode exhibits a Nernstian slope of 29.7 ± 0.4 mV/decade in the activity range of 1.0 × 10 -7 - 7.9 × 10 -4  M and the limit of detection is 6.8 × 10 -8  M. Particularly, the electrode based on DAAQ-TFP@rGO exhibits a low potential drift of 1.2 ± 0.2 μV/h over 70 h due to the large capacitance of 2.0 mF. Moreover, the DAAQ-TFP@rGO-based Cd 2+ -ISE shows good reproducibility and the standard deviations of the standard potentials for single batch and batch-to-batch are 0.28 (n = 4) and 0.30 mV (n = 4), respectively. The developed SC-Cd 2+ -ISE is not disturbed by light or gas and no aqueous layer occurs between the sensing membrane and DAAQ-TFP@rGO layer. The DAAQ-TFP@rGO composite is highly promising for construction of calibration-free SC-ISEs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Circulating tumor cells (CTCs), as a type of tumor, have attracted wide attention because of their characteristics of shedding from the primary tumor and spreading to other tissues and organs through peripheral blood. The circulating tumor DNA (ctDNA), the DNA released by CTCs and other tumor cells into the peripheral blood, was considered as a promising detection substance for clinical application. By utilizing the biocompatibility of red blood cells to realize the attachment of tetrahedral DNA (TDN), as well as the specific target recognition ability of TDN to enable efficient recognition of targets, a biocompatible electrochemical biosensor for effective and rapid detection of ctDNA was developed using methylene blue (MB) as the signal probe. The current signal and the logarithm of ctDNA concentration were linearly correlated in the range from 1 fM to 100 pM with the detection limit of 0.66 fM. With high specificity, the TDN-based biosensor can detect ctDNA efficiently in the real biological environment such as serum, which provided a potential opportunity for the early clinical diagnosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In situ growth of quasi-superhydrophobic porous NiCo 2 S 4 nanosheet arrays with a one-step electrodeposition method was provided. A calcium ion-selective electrodes (Ca 2+ -ISE) was subsequently constructed by using the prepared NiCo 2 S 4 as a solid contact layer. The proposed Ca 2+ -ISE exhibits a good Nernstian slope of 30.7 ± 0.3 mV/dec and a detection limit of 1.6 × 10 -7  M. Due to the large redox capacitance of 1.8 mF, the Ca 2+ -ISE based on NiCo 2 S 4 nanosheet arrays shows a high potential stability of 1.9 ± 0.5 μV/h over 90 h. Excellent reproducibilities for the NiCo 2 S 4 -based Ca 2+ -ISEs can be obtained with the single batch and batch-to-batch E° standard deviations of 0.3 (n = 6) and 0.7 mV (n = 5), respectively. The NiCo 2 S 4 nanosheet arrays have a large contact angle of 148 ± 1.4 ° , which effectively suppresses the formation of a water layer at the sensing membrane/NiCo 2 S 4 interface., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

O-Linked β-N-acetylglucosamine (O-GlcNAc), a versatile posttranslational modification (PTM), is found on many chromatin-associated proteins (CAPs), such as transcription factors and their cofactors (TFCs). O-GlcNAc turnover influences the dynamic interactions of CAPs with chromatin and thereby regulates gene expression. Therefore, both global profiling of O-GlcNAc chromatin-associated proteins (OCAPs) and genome-wide mapping of their DNA binding sites are invaluable for understanding the functions of OCAPs and the regulatory machinery of O-GlcNAcylation on gene transcription. However, it is difficult to conduct genome- and proteome-wide OCAP studies using the widely adopted chromatin immunoprecipitation (ChIP) method due to the lack of highly O-GlcNAc-specific panantibodies. Therefore, we developed a chemical enrichment method (AFT-OCAP) for simultaneously profiling OCAPs and mapping their binding DNA via mass spectrometry (MS) analysis and DNA sequencing. In our method, we developed an alkynyl-functionalized trimethylpiperidine (AFT) reagent to perform highly efficient chemical derivatizations of azide-labeled OCAP-DNA complexes. The reversible affinity between the immobilized anti-trimethylpiperidine antibody resin and AFT reagent leads to specific enrichment and efficient elution of the OCAP-DNA complexes for both MS identification and sequencing. Deep coverage of OCAPs was achieved from HeLa cells, including 1951 O-GlcNAc peptides from 1136 O-GlcNAc chromatin-associated transcription factors and cofactors (TFCs) using HCD fragmentation and 669 O-GlcNAc sites using EThcD fragmentation. In addition, the distributions of O-GlcNAcylation across the genome and the dynamic interactions of OCAPs upon O-GlcNAc regulation were obtained., (Copyright © 2021. Published by Elsevier B.V.)

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in various fields including clinical diagnosis, environmental monitoring and industrial analysis. Although most samples of analytical interest measured by the ISEs are aqueous solutions, the applications of these electrodes in nonaqueous media are often inevitable. Unfortunately, so far, little has been known about the extent to which the properties of the ISEs could be affected by the organic solvents. Herein, the feasibility for the applications of the polymeric membrane ISEs in nonaqueous media has been investigated. A polymeric membrane Ca 2+ -ISE is chosen as a model of potentiometric sensors. Four typical water miscible organic solvents (three protic solvents: ethanol, acetic acid, and methanol, and one aprotic dipolar solvent: acetonitrile) are used as the representative examples. Experiments show that the aprotic solvent acetonitrile has the strongest destructive ability towards the sensing performance of the ISE in terms of Nernstian slope and selectivity coefficient. Moreover, the effect on the sensing performance depends on the kind of the protic solvent, the immersion time and the polarity of the membrane plasticizer. We believe that the obtained results could promote further applications of the polymeric membrane ISEs in the organic solvent-containing samples, which could significantly extend the application scope of the ISEs., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The transformation from the traditional potentiometric response of an ion-selective electrode (ISE) to other signal readout is promising to realize the potential signal amplification. In this work, the redox probes, including ferrocyanide/ferricyanide (Fe(CN) 6 3-/4- ), hexaammineruthenium (Ru(NH 3 ) 6 3+ ) and ferrocene derivatives, were introduced to read out the potentiometric response for the solid-contact Ca 2+ -ISE. The mechanism is that the oxidation current of the redox probe on a glassy carbon electrode is modulated by the potential of the ISE through changing the concentrations/activities of Ca 2+ under the control of the constant applied potential. Results show that the linear range and the slope sensitivity for detection Ca 2+ by using the amperometric signal based on Fe(CN) 6 4-/3- redox probe are adjustable through changing the applied potentials. Moreover, the redox probe-based amperometric signal for the solid-contact Ca 2+ -ISE is found to be related to both of the types of the redox probes and the electrode areas. This work provides a convenient and general method for translating the potential response at mV grade to the amperometric signal at the μA level, and is promising for detection of ions with high sensitivity by using the ISEs., (Copyright © 2021 Elsevier B.V. All rights reserved.)

As one of the most common and important post-translational modifications, protein N-glycosylation plays essential roles in many biological processes and have long been considered closely correlated with the occurrence and progression of multiple diseases. Systematic characterization of these disease-related protein N-glycosylation is one of the most convenient ways for new diagnostic biomarker and therapeutic drug target discovering. However, the biological samples are extremely complex and the abundance of N-glycoproteins are especially low, which make highly efficient N-glycoprotein/glycopeptide enrichment before mass spectrometry analysis a prerequisite. In this work, a new type of hydrophilic material (GO-pDMAPS) was prepared by in situ growth of linear zwitterionic polymer chains on the surface of GO and it was successfully applied for N-glycopeptide enrichment from human urine. Due to the excellent hydrophilicity and the facilitate interactions between this GO-pDMAPS and the targets, a total of 1426 N-glycosylated sites corresponding to 766 N-glycoproteins as well as 790 N-glycosylation sites corresponding to 470 N-glycoproteins were enriched and identified from urine of healthy subjects and patients with lung adenocarcinoma, respectively. Among which, 27 N-glycoproteins were expressed exclusively and 4 N-glycoproteins were upregulated at least 3 times comparing with the healthy group, demonstrating the tremendous potential of this new hydrophilic material for large scale and in depth N-glycoproteome research., (Copyright © 2021. Published by Elsevier B.V.)

The developments of alternative signal readout strategies for the ion-selective electrodes (ISEs) are necessary in order to break through the limitation of the Nernst equation. In this work, a simple, convenient and easily operated strategy based on the non-enzymatic amperometric measurement of H 2 O 2 is proposed to read out the potentiometric responses for the ISEs. The proposed amperometric signal readout based on H 2 O 2 is carried out in a two compartment electrochemical cell configuration containing a detection cell and a sample cell, physically connected by a salt bridge. A glassy carbon (GC) electrode is placed in the detection cell to monitor the oxidation current of H 2 O 2 , and an ISE is placed in the sample cell to act as both the reference electrode and the potentiometric sensor for obtaining the ion activities. The oxidation of H 2 O 2 is induced by a constant potential applied between the GC electrode and the ISE, and subsequently modulated by the potential change of the ISE in the presence of the primary ion. The proposed amperometric signal readout based on H 2 O 2 shows the satisfied slope sensitivity and detection limit, which are better than or compared to those for the potentiometric responses for the ISEs. This work provides a general strategy for transforming the potential response of the ISEs into the amperometric readout, and is promising for detection of cations (eg., Ca 2+ ) and anions (eg., NO 3 - ) with high sensitivity and excellent selectivity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Small extracellular vesicles (SEVs), are cell-derived, membrane-enclosed nanometer-sized vesicles that play vital roles in many biological processes. Recent years, more and more evidences proved that small EVs have close relationship with many diseases such as cancers and Alzheimer's disease. The use of phosphoproteins in SEVs as potential biomarkers is a promising new choice for early diagnosis and prognosis of cancer. However, current techniques for SEVs isolation still facing many challenges, such as highly instrument dependent, time consuming and insufficient purity. Furthermore, complex enrichment procedures and low microgram amounts of proteins available from clinical sources largely limit the throughput and the coveage depth of SEVs phosphoproteome mapping. Here, we synthesized Ti 4+ -modified magnetic graphene-oxide composites (GFST) and developed a "one-material" strategy for facile and efficient phosphoproteome enrichment and identification in SEVs from human serum. By taking advantage of chelation and electrostatic interactions between metal ions and phosphate groups, GFST shows excellent performance in both SEVs isolation and phosphopeptide enrichment. Close to 85% recovery is achieved within a few minutes by simple incubation with GFST and magnetic separation. Proteome profiling of the isolated serum SEVs without phosphopeptide enrichment results in 515 proteins, which is approximately one-fold more than those otained by ultracentrifugation or coprecipitation kits. Further application of GFST in one-material-based enrichment led to identification of 859 phosphosites in 530 phosphoproteins. Kinase-substrate correlation analysis reveals enriched substrates of CAMK in serum SEVs phosphoproteome. Therefore, we expect that the low instrument dependency and the limited sample requirement of this new strategy may facilitate clinical investigations in SEV-based transportation of abnormal kinases and substrates for drug target discovery and cancer monitoring., (Copyright © 2020 Elsevier B.V. All rights reserved.)

For construction of solid-contact ion-selective electrodes (SC-ISEs), ion-to-electron transducers based on the redox capacitance transduction mechanism are currently restricted to organic materials. Exploring inorganic nanomaterials with high redox buffer capacities as intermediate layers for SC-ISEs would offer another alternative. Herein, a solid-contact calcium ion-selective electrode (SC-Ca 2+ -ISE) with a new inorganic redox buffer-Ag@AgCl/1-tetradecyl-3-methylimidazolium chloride (TMMCl) as the ion-to-electron transducer is presented. In this system, the predominant component core-shell Ag@AgCl nanoparticles with diameters ranging from 30 to 100 nm can be prepared through a two-step process. An ionic liquid TMMCl is used to offer a source of free Cl - . The developed SC-Ca 2+ -ISE exhibits a near Nernstian slope of 28.3 mV/decade for Ca 2+ in the range of 10 -6 - 10 -2  M. By using of the inorganic redox buffer, the SC-Ca 2+ -ISE has a smaller impedance and higher capacitance than the coated-wire electrode, which guarantees a stable potential response. Additionally, the proposed SC-Ca 2+ -ISE shows excellent resistances to interferences of light, O 2 and CO 2 , with a reduced water layer formed between the ion-selective membrane and the underlying solid contact. The developed inorganic redox buffer of Ag@AgCl/TMMCl can be effectively used as a new ion-to-electron transducer for construction of solid contact ISEs., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Parkinson's disease (PD) severely affects life quality of patients and has brought huge economic burden to health system worldwide. Previous studies have shown that the abnormal expression of hydrogen peroxide (H 2 O 2 ) in the brain is closely related to the development of neurodegenerative diseases such as PD. Herein, we designed a novel deep-red H 2 O 2 fluorogenic probe PB1 to detect the level of H 2 O 2 in vivo. PB1 showed a highly selectivity response to H 2 O 2 over other reactants such as reactive oxygen/nitrogen species, biothiols and various ions in aqueous solution at physiological pH. We have demonstrated that PB1 possesses an excellent response to H 2 O 2 in the cells and in the brain tissue of drosophila from confocal fluorescence imaging. These results suggested that PB1 holds great potential in the study of the relationship between H 2 O 2 overexpression and PD., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A ratiometric visualized fluorescent probe of H 2 S of intramolecular charge transfer (ICT) and excited intramolecular proton transfer (ESIPT) mechanisms due to solvation effects has been designed and synthesized. This chemosensor shows the distinct signal changes with dual-emission in blue and green fluorescence spectral channel (from 495 nm to 525 nm) upon the addition of H 2 S in a single wavelength excitation. This chemosensor exhibits the low detection limit (91 nM) and high sensitivity and selectivity. Based on this, this chemosensor was successfully used not only to monitor H 2 S exogenously but also used to detect and image the endogenously generated H 2 S in HeLa cells with excellent performance., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A new simple and facile fluorescent ratiometric probe (probe 1) has been designed for the detection of cysteine (Cys). Probe 1 as the fluorophore contains a typical excited-state intramolecular proton transfer (ESIPT) dye. In probe 1 to restore the ESIPT process, the group of acrylate which acts as the recognition unit can block the ESIPT process and can be selectively achieved by Cys, which makes the probe as the ratiometric fluorescent detection for Cys in aqueous solution. This probe shows highly selectivity towards Cys over other biothiols including glutathione (GSH) and homocysteine (Hcy) because of specific cyclization between Cys and acrylate group, and having a detection limit of 42.3 nM. In addition, the experiment of cell imaging shows that probe 1 possesses low cytotoxicity and excellent cell permeability towards the living cells, and has been successfully applied to the ratiometric imaging not only for the endogenous but also for the exogenous cysteine in the living cells effectively., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new highly selective fluorescent chemosensor for formaldehyde (FA) has been synthesized based on boron dipyrromethene as fluorophore and o-phenylenediamine (OPDA) as reaction group. When FA is added, the fluorescence emission band of the chemosensor red shift (from 525 nm to 548 nm) accompanied by an increase in intensity with strong green fluorescence was observed. This chemosensor also exhibited the lowest detection limit (0.104 μM) distinguished with other articles that have been reported. The application to cellular fluorescence imaging or test papers detection both indicated that the probe was highly responsive to the FA in endogenous cells and in the gaseous environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

As one of the most common post-translational modifications, protein N-glycosylation precipitates in many important biological processes and has closely correlations with the occurrence and progression of multiple diseases. Plasma exosomes secreted by cells contain various bioactive N-glycoproteins which may serve as potential biomarkers for early disease diagnosis and treatment. However, the protein N-glycosylation profile in human plasma exosome is largely unknown, due to the technical challenges in glycoprotein identification. Signals of the rare N-glycoproteins/N-glycopeptides are severely suppressed by the abundant coexisting non-glycosylated counterparts in mass spectrometry analysis. Therefore, specific enrichment of N-glycoprotein/glycopeptide is a prerequisite for large scale N-glycosylation profiling. In this work, we developed a hydrazide functionalized thermosensitive polymer for efficient enrichment and in-depth identification of protein N-glycosylation in human plasma exosome by mass spectrometry. The polymer chains completely dissolve in the enrichment system to form a homogeneous solution. Therefore, efficient covalent coupling between the N-glycoprotein/glycopeptide and the polymer chain is achieved, due to the reduced interfacial mass transfer resistance and the densely packed accessible functional groups on the polymer chains. Furthermore, the thermosensitive polymer can be easily precipitated and recovered by simply rising the system temperature to above 34 °C. As a result, 329 N-glycosylation sites corresponding to 180 N-glycoproteins were enriched and identified from plasma exosomes of glioma patients and healthy subjects using the thermosensitive polymer. By quantitative comparison, we found 26 N-glycoproteins significantly changed between the glioma patients and the healthy subjects, demonstrating the potential of this new strategy for N-glycoproteome research of plasma exosome and biomarker discovery., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Liquid biopsies using body fluids have gained much attention in recent years due to their multiple advantages in clinical diagnosis, such as less/non-invasive collection, suitability for longitudinal disease monitoring, and better representation of tumor heterogeneity. As an attractive choice for liquid biopsy, urine proteins and their post-translational modifications (PTMs) have the potential to offer significant insights into physiological variations and pathological changes in the human body. However, due to the intrinsically large variability of urine proteins and their PTMs among different individuals, there is a high demand for strategies for high-throughput analysis of a large number of samples to obtain a comprehensive view and a reliable reference interval of the urine proteome. In this work, we proposed a new urine phosphoproteome sample processing strategy that combines fast protein extraction, efficient multiple immobilized-proteases digestion, and tandemly connected centrifugal tips device-based facile phosphopeptide enrichment & fractionation. This strategy is capable of paralleled sample processing with an approximate five-fold reduction in processing time and is therefore particularly suitable for handling a large number of urine samples. Totally, we identified 4196 phosphosites in human urine proteins by mass spectrometry in replicated tests, a number which is dozens of times larger than those previously reported. Therefore, this strategy may have great potential in urine-based phosphoprotein biomarker screening and drug response studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Protein N-glycosylation is one of the most important post-translational modifications, participating in many key biological and pathological processes. Large-scale and precise identification of N-glycosylated proteins and peptides is especially beneficial for understanding their biological functions and for discovery of new clinical biomarkers and therapeutic drug targets. However, protein N-glycosylation is microheterogeneous and low abundant in living organisms, therefore specific enrichment of N-glycosylated proteins/peptides before mass spectrometry analysis is a prerequisite. In this work, we developed a new type of polymer hybrid graphene oxide (GO) by in situ growth of hydrazide-functionalized hydrophilic polymer chains on the GO surface (GO-PAAH) for selective N-glycopeptide enrichment and identification by mass spectrometry. The densely attached and low steric hindrance hydrazide groups as well as the highly hydrophilic nature of GO-PAAH facilitate N-glycopeptide enrichment by the combination of hydrazide capturing and HILIC interaction. Taking advantage of the unique features of GO-PAAH, all of the three N-glycopeptides of bovine fetuin were successfully enriched and identified with significantly enhanced signal intensities from a digest mixture of bovine fetuin and bovine serum albumin at a mass ratio of 1:100, demonstrating the excellent enrichment selectivity of GO-PAAH. Furthermore, a total of 507 N-glycosylation sites and 480 N-glycopeptides in 232 N-glycoproteins were enriched and identified from 10μL of human serum by three replicates using this novel enrichment material, which is nearly two times higher than the commercial hydrazide resin based method (280 N-glycosylation sites, 261 N-glycopeptides and 144 N-glycoproteins in three experiments). Among the identified, 95 N-glycosylation sites were not reported in the Uniprot database, and 106 N-glycoproteins were disease related in the Nextprot database, indicating the potential of this new enrichment material in global mapping of protein N-glycosylation., (Copyright © 2017 Elsevier B.V. All rights reserved.)

O-GlcNAcylation is a kind of dynamic O-linked glycosylation of nucleocytoplasmic and mitochondrial proteins. It serves as a major nutrient sensor to regulate numerous biological processes including transcriptional regulation, cell metabolism, cellular signaling, and protein degradation. Dysregulation of cellular O-GlcNAcylated levels contributes to the etiologies of many diseases such as diabetes, neurodegenerative disease and cancer. However, deeper insight into the biological mechanism of O-GlcNAcylation is hampered by its extremely low stoichiometry and the lack of efficient enrichment approaches for large-scale identification by mass spectrometry. Herein, we developed a novel strategy for the global identification of O-GlcNAc proteins and peptides using selective enzymatic deglycosylation, HILIC enrichment and mass spectrometry analysis. Standard O-GlcNAc peptides can be efficiently enriched even in the presence of 500-fold more abundant non-O-GlcNAc peptides and identified by mass spectrometry with a low nanogram detection sensitivity. This strategy successfully achieved the first large-scale enrichment and characterization of O-GlcNAc proteins and peptides in human urine. A total of 474 O-GlcNAc peptides corresponding to 457 O-GlcNAc proteins were identified by mass spectrometry analysis, which is at least three times more than that obtained by commonly used enrichment methods. A large number of unreported O-GlcNAc proteins related to cell cycle, biological regulation, metabolic and developmental process were found in our data. The above results demonstrated that this novel strategy is highly efficient in the global enrichment and identification of O-GlcNAc peptides. These data provide new insights into the biological function of O-GlcNAcylation in human urine, which is correlated with the physiological states and pathological changes of human body and therefore indicate the potential of this strategy for biomarker discovery from human urine., (Copyright © 2017. Published by Elsevier B.V.)

Detection of multiplex tumor markers was of great importance for cancer diagnosis. Immunochromatographic test strip (ICTS) was the most frequently-used point-of-care detection means. Herein, a convenient and fast method for simultaneous quantitative detection of neuron specific enolase (NSE) and carcinoembryonic antigen (CEA) was developed based on ICTS using quantum dot beads (QBs) as marking material. Good monodispersity, high colloidal stability and carboxyl-modified (COOH-) QBs were used. For this method, two test lines were applied to the NC membrane for simultaneous analysis of CEA and NSE respectively. The ideal limit of CEA and NSE detection was 0.0378ng/mL and 0.0426ng/mL with scarcely any cross-reactivity. Moreover, the fluorescent signal intensity of the nitrocellulose membrane could be easily read out in the cooperation of the "Handing" system without professional operators. The possible clinical utilization of this platform was demonstrated by detecting 100 clinic human serums. The result showed that the platform had sensitivity of 99% and 97% for CEA and NSE, while the specificity was 97% and 100% respectively. Our results indicated that the QBs based ICTS not only owning the ability of sensitive and specific simultaneous detection of CEA and NSE, but also showing the potential in developing this ICTS into a routine part of early lung cancer diagnosis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Hydroxylated polychlorinated biphenyls (OH-PCBs) can be detected by liquid chromatography-mass spectrometry coupled to solid-phase extraction (SPE) using a dummy molecularly imprinted polymer (DMIP) as a sorbent. The DMIP is prepared by using an analogue of OH-PCBs (i.e., 4, 4-dihydroxybiphenyl) as a dummy template, to avoid the leakage of the target molecules. The DMIP-SPE sorbent shows good recoveries for OH-PCBs at pH 11 due to the charge-assisted hydrogen bondings between OH-PCBs and the DMIP. It has been found that the DMIP is much more effective and selective than the traditional C18-SPE method. The sample pH, polymer dosage, elution solvent and volume have been optimized for higher recoveries. Under the optimum experimental conditions, OH-PCBs can be detected in the linear concentration range of 0.05-1.0 pM, with the detection limits ranging from 11 fM to 82 fM for 4'-OH-CB 9, 4'-OH-CB 30, 4'-OH-CB 61, 4'-OH-CB 106 and 4'-OH-CB 112. The proposed system has been successfully applied to the determination of trace OH-PCBs in spiked water samples with recoveries in the range of 89-110%., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Polyamidoamine (PAMAM) dendrimer generation 2.5 was synthesized and evaluated as sweeping agent for in-column enrichment and as stationary phase for capillary electrochromatographic separation of heavy metal ions, viz., Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), in a running buffer containing 4-(2-pyridylazo)resorcinol (PAR) as a chromogenic reagent. During experiment, a plug of aqueous PAMAM generation 2.5 solution was first introduced to the capillary, followed by electrokinetic injection of the heavy metal ions under a positive voltage. In this step, PAMAM acted as a sweeping agent, stacking the metal ions on the analyte/PAMAM boundary by forming metal ion-PAMAM complexes. The second preconcentration process occurred when PAR, a stronger ligand, moving toward the injection end under the electric field, reached and re-swept the metal ion-PAMAM zone, forming metal ion-PAR complexes. During separation, the neutral PAMAM moved toward the detector with the electroosmotic flow, dynamically coating the capillary wall, forming stationary phases that affected the separation of the metal ions. Due to the function of PAMAM, the detection sensitivity and resolution of the heavy metal ions improved significantly. Under the optimum conditions, the detection limits were 0.299, 0.184, 0.774, 0.182 and 0.047 μg/L for Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), respectively. The method was successfully applied to the determination of heavy metals in snow, tap and rain water samples., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Protein glycosylation is involved in the control of many important biological processes and structural alterations of the N-linked glycans are correlated with various kinds of disease. High-throughput N-glycan profiling is a key technique for elucidating the functions of glycans in biological process and disease development as well as discovering new diagnostic biomarkers. However, the low abundance of glycans existing in living organism, the competition/suppression effect of other highly abundant biological molecules and the inherent lack of alkalinity and hydrophobicity of glycans leads to particularly poor detection sensitivity in MS analysis. Here, we demonstrated the first "one-step" approach for highly efficient glycan enrichment and derivatization using reduced graphene oxide as nanoreactors and 1-pyrenebutyric hydrazide for glycan capture and derivatization, which resulted in a 33-fold increase in the glycan detection sensitivity in MALDI-TOF-MS and the identification of 48N-glycoforms from human plasma., (Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.)

Protein glycosylation regulates numerous important biological processes and plays key roles in many diseases including cancer, diabetes and inflammation. The ability to efficiently profile variation of protein glycosylation in biological samples is very useful for identifying new diagnostic biomarkers or developing new therapeutic approaches. Due to the low availability of glycoprotein/glycopeptide from natural sources, enrichment before mass spectrometry (MS) analysis is usually a prerequisite. Affinity enrichment using lectins is currently one of the most widely adopted approaches. Conventionally, lectins are immobilized on solid supporting materials for sample recovery. However, the limited specific surface area, high steric hindrance and rigid nature of such supporting materials restricts lectin loading amount and results in low flexibility as well as accessibility of the immobilized lectins. Therefore, we proposed using core-shell microparticles composed of silica core and brush-like polymer chains shell for improved lectin immobilization. The surface bound brush-like polymer are synthesized by in situ growth of polymer chains from microparticle surface using surface initiated atom transfer radical polymerization (SI-ATRP). The flexible non-crosslinked polymer chains not only provide numerous binding sites, but also work as three-dimensional support for lectin immobilization, which leads to high loading amount and good accessibility of the immobilized lectin. Successful enrichment which facilitated glycoprotein/glycopeptide identification is demonstrated., (Copyright © 2013 Elsevier B.V. All rights reserved.)

We report herein a sensitive, selective, convenient CE determination of heme proteins in complex matrices by a sodium-dodecyl-sulfate-assisted, zirconia nanoparticle-enhanced copper (II)-catalyzed luminol-hydrogen peroxide chemiluminescence (CCLHPCL). Introducing a segment of sodium dodecyl sulfate to the capillary after sample injection not only rendered selective detection by quenching the luminescence signals from the non-heme proteins but also owning to the suppressed protein adsorption, led to significant improvement in separation efficiency and detection sensitivity. The signals were further improved by addition of ZrO(2) nanoparticles to the chemiluminescence solution. Compared with the conventional CCLHPCL, the detection limits (S/N=3) were improved by 10.2-22.0 folds, with 7.8×10(-9), 3.3×10(-9) and 1.5×10(-9) M for three model proteins, viz, myoglobin, hemoglobin and cytochrome C, respectively. Because the method did not require sophisticated pretreatment, it was convenient to analyze heme proteins in complex matrices, as demonstrated, hemoglobin in human blood and spiked human urine samples., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag(+)-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2'-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag(+). The plasticized poly(vinyl chloride) membrane electrode using 22-membered N(2)S(5)-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag(+) over most of the interfering cations have been determined as <-8.0. Under optimal conditions, a lower detection limit of 2.2x10(-10)M can be obtained for the membrane Ag(+)-ISE.

A novel potentiometric method for the determination of ascorbate is described in this communication. It is based on ascorbate oxidation with permanganate which is continuously released from the inner reference solution of a ligand-free tridodecylmethylammonium chloride (TDMAC)-based polymeric membrane ion selective electrode (ISE). The ISE potential determined by the activity of permanganate ions released at the sample-membrane phase boundary is increased with the consumption of permanganate. The proposed membrane electrode is useful for continuous and reversible detection of ascorbate at concentrations in 0.1M NaCl ranging from 1.0 x 10(-6) to 1.0 x 10(-3)M with a detection limit of 2.2 x 10(-7)M.

A highly sensitive and selective method has been developed for spectrophotometric determination of boron in plants, the method based on the color reaction of new reagent 1-(2,3,4-trihydroxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid (THBA) with boron (III). In an ammonium acetate solution of pH 8.0, boron(III) reacts with THBA to form a 1:2 yellow complex which has a maximum absorption peak at 430nm. The reaction can complete within 90min and the absorbance of the complex remains maximum and almost constant at least for 24h under a temperature range from 0 to 35 degrees C. The apparent molar absorptivity and Sandell's sensitivity are 2.95x10(4)lmol(-1)cm(-1) and 0.00036ngcm(-2), respectively. The limit of quantification, limit of detection and relative standard deviations were found to be 5.1, 1.5ngml(-1) and 1.12%, respectively. Under the optimum conditions, the absorbency of the complex (lambda(max)=430nm) increases linearly with concentration up to 0.8mugml(-1) of boron(III). The influences of foreign ions on the determination of boron were investigated in detail. Most of foreign ions can be tolerated in considerable amounts. Experiments have indicated that THBA as chromogenic reagent for spectrophotometric determination of boron has excellent analytical characteristics. Its sensitivity is more than 4.2-fold that of azomethine-H, and stability is advantage over other derivatives of azomehine-H remarkably. Moreover, the synthesis of THBA and its physicochemical properties of THBA were also investigated in detail. Proposed method has been applied to the determination of boron in plants with satisfactory results.

A new bis-Schiff base ligand, bis-(trimethylolaminomethane)-4-tert-butyl-disalicylicimine (HL), was synthesized. The fluorescence intensity of HL-Zn(2+) complex was increased by about 8-fold upon addition of beta-cyclodextrin (beta-CD). The spectrofluorimetric determination of trace amounts of Zn(2+) based on the phenomenon was carried out. The excitation and emission wavelengths are 405 and 465nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Zn(2+) in the range 0-317 mugl(-1) with a detection limit of 1.0mugl(-1). The interferences of some inorganic ions were described. The method is a selective, sensitive, rapid, and simple analytical procedure for the determination of Zn(2+) in crops. The mechanism for the fluorescence enhancement was also discussed.