Development of a new open-tubular capillary electrochromatography method for in vitro monitoring of toxic aromatic amines distribution in rat blood.

Exposure to aromatic amines from different industrial and agricultural activities entails a substantial risk of deleterious somatic effects, genetic damage and cancer development. Thus, a new and simple method for separation and analysis of aromatic amines has been developed by open-tubular capillary electrochromatography with a novel amphipathic block copolymer (poly(tert-butyl acrylate)(127)-block-poly(glycidyl methacrylate)(86)) coating based on its self-assembled property. Key factors affecting the separation efficiency of the test analytes, such as pH, buffer concentration and selective solvent, were studied in detail.

Determination of sodium benzoate by chiral ligand exchange CE based on its inhibitory activity in D-amino acid oxidase mediated oxidation of D-serine.

A novel quantitative approach for the determination of sodium benzoate (SB) was proposed by the kinetic study about its competitive inhibitory efficiency to D-amino acid oxidase (DAAO) activity with a chiral ligand exchange capillary electrophoresis (CE) method, in which the Zn(II)-L-prolinamide complex was chosen as a novel chiral selector. After the optimization of buffer pH and the chiral selector concentration this chiral ligand exchange CE method was employed to determine labeled D,L-Serine with good linearity (r(2)≥0.995), efficient recovery (95.

A novel amphipathic block copolymer coating forming micelle-like aggregates for separation of steroids in open tubular capillary electrochromatography.

A new amphipathic block copolymer, poly(tert-butyl acrylate)(127)-block-poly(glycidyl methacrylate)(86), was developed for the coating in open tubular capillary electrochromatography. The self-assembly characters of the coating, which could form micelle-like aggregates under proper conditions, were observed by atomic force microscopy. Compared with bare capillary, this coating could act as surfactant and lead to improve the separation of steroids.

Study on the decrease of renal D-amino acid oxidase activity in the rat after renal ischemia by chiral ligand exchange capillary electrophoresis.

D: -Amino acid oxidase (DAAO) in mammal kidney regulates the renal reactive oxygen species (ROS) levels directly and plays a leading role in the development of ROS-mediated renal pathologic damages based on its crucial role in the oxidative deamination of D: -amino acids and the consequent generation of H(2)O(2). Quantitative measurement of DAAO activity in the process of renal ischemia, which could help to understand the molecular mechanisms of this gripping acute renal disease, was conducted through the determination of chiral substrate by capillary electrophoresis (CE) in our study. In this study, a chiral ligand exchange CE method was explored with Zn(II)-L: -alaninamide complex as the chiral selector to investigate DAAO activity by determining the decreased concentration of the chiral substrate of DAAO-mediated enzymatic reaction.

Online electrochemical measurements of Ca2+ and Mg2+ in rat brain based on divalent cation enhancement toward electrocatalytic NADH oxidation.

This study describes a novel electrochemical approach to effective online monitoring of electroinactive Ca(2+) and Mg(2+) in the rat brain based on the current enhancement of divalent cations toward electrocatalytic oxidation of NADH. Cyclic voltammetry for NADH oxidation at the electrodes modified with the polymerized film of toluidine blue O (TBO) reveals that the current of such an electrocatalytic oxidation process is remarkably enhanced by divalent cations such as Ca(2+) and Mg(2+). The current enhancement is thus used to constitute an electrochemical method for the measurements of Ca(2+) and Mg(2+) in a continuous-flow system with the polyTBO-modified electrode as the detector.

Extracellular ascorbic acid fluctuation during the protective process of ischemic preconditioning in rabbit renal ischemia-reperfusion model measured.

Background: Ascorbic acid has important antioxidant properties, and may play a role in the protective effects of ischemic preconditioning on later ischemia-reperfusion. Herein, we examined the role of endogenous extracellular ascorbic acid in ischemic preconditioning in the kidney.

Methods: We developed a solitary rabbit kidney model where animals received ischemia-reperfusion only (ischemia-reperfusion group, n = 15) or ischemic preconditioning followed by ischemia-reperfusion (ischemic preconditioning group, n = 15).

Determination of formal potential of NADH/NAD+ redox couple and catalytic oxidation of NADH using poly(phenosafranin)-modified carbon electrodes.

The electrochemical regeneration of NADH/NAD(+) redox couple has been studied using poly(phenosafranin) (PPS)-modified carbon electrodes to evaluate the formal potential and catalytic rate constant for the oxidation of NADH. The PPS-modified electrodes were prepared by electropolymerization of phenosafranin onto different carbon substrates (glassy carbon (GC) and basal-plane pyrolytic graphite (BPPG)) in different electrolytic solutions. The formal potential was estimated to be -0.

Pt-Ru/CeO2/carbon nanotube nanocomposites: an efficient electrocatalyst for direct methanol fuel cells.

Pt-Ru/CeO(2)/multiwalled carbon nanotube (MWNT) electrocatalysts were prepared using a rapid sonication-facilitated deposition method and were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and voltammetry. Morphological characterization by TEM revealed that CeO(2) nanoparticles (NPs) were in intimate contact with Pt-Ru NPs, and both were highly dispersed on the exteriors of nanotubes with a small size and a very narrow size distribution. Compared with the Pt-Ru/MWNT and Pt/MWNT electrocatalysts, the as-prepared Pt-Ru/CeO(2)/MWNT exhibited a significantly improved electrochemically active surface area (ECSA) and a remarkably enhanced activity toward methanol oxidation.

Enhanced catalytic reduction of oxygen at tantalum deposited platinum electrode.

A tantalum deposited platinum electrode that offers an enhanced catalytic four-electron reduction of oxygen over the bare platinum electrode in acidic solution is explored.

Noncovalent attachment of NAD+ cofactor onto carbon nanotubes for preparation of integrated dehydrogenase-based electrochemical biosensors.

This study describes a facile approach to the preparation of integrated dehydrogenase-based electrochemical biosensors through noncovalent attachment of an oxidized form of beta-nicotinamide adenine dinucleotide (NAD(+)) onto carbon nanotubes with the interaction between the adenine subunit in NAD(+) molecules and multiwalled carbon nanotubes (MWCNTs). X-ray photoelectron spectroscopic and cyclic voltammetric results suggest that NAD(+) is noncovalently attached onto MWCNTs to form an NAD(+)/MWCNT composite that acts as the electronic transducer for the integrated dehydrogenase-based electrochemical biosensors. With glucose dehydrogenase (GDH) as a model dehydrogenase-based recognition unit, electrochemical studies reveal that glucose is readily oxidized at the GDH/NAD(+)/MWCNT-modified electrode without addition of NAD(+) in the phosphate buffer.

Femtoliter and attoliter electrochemical cells on chips.

Chip electrochemistry is one of the top ambitions of today's electrochemistry. Here, a study for manufacturing electrochemical microcells on chips in a cost-effective, facile, and mass-producible way is presented. The ultrasmall, planar electrochemical cells, ranging from 140 femtoliter to 14 attoliter, can work independently as electroanalytical devices with embedded functional microelectrodes.

Sensitive impedimetric DNA biosensor with poly(amidoamine) dendrimer covalently attached onto carbon nanotube electronic transducers as the tether for surface confinement of probe DNA.

This study demonstrates a new impedimetric DNA biosensor with second-generation poly(amidoamine) dendrimer (G2-PAMAM) covalently functionalized onto multi-walled carbon nanotube (MWNT) electronic transducers as the tether for surface confinement of probe DNA. G2-PAMAM dendrimer was covalently functionalized onto purified MWNTs and the as-formed G2-PAMAM-functionalized MWNT composite (i.e.

A non-oxidative electrochemical approach to online measurements of dopamine release through laccase-catalyzed oxidation and intramolecular cyclization of dopamine.

A new electrochemical approach to selective online measurements of dopamine (DA) release in the cerebral microdialysate is demonstrated with a non-oxidative mechanism based on the distinct reaction properties of DA and the excellent biocatalytic activity of laccase. To make the successful transition of the distinct sequential reaction properties of DA from a conceptual determination protocol to a practical online analytical system, laccase enzyme is immobilized onto magnetite nanoparticles and the nanoparticles are confined into a fused-silica capillary through an external magnetic field to fabricate a magnetic microreactor. The microreactor is placed in the upstream of the thin-layer electrochemical flow cell to efficiently catalyze the oxidation of DA into its quinonoid form and thereby initialize the sequential reactions including deprotonation, intramolecular cyclization, disproportionation and/or oxidation to finally give 5,6-dihydroxyindoline quinone.

Effective electrochemical method for investigation of hemoglobin unfolding based on the redox property of heme groups at glassy carbon electrodes.

This study demonstrates a facile and effective electrochemical method for investigation of hemoglobin (Hb) unfolding based on the electrochemical redox property of heme groups in Hb at bare glassy carbon (GC) electrodes. In the native state, the heme groups are deeply buried in the hydrophobic pockets of Hb with a five-coordinate high-spin complex and thus show a poor electrochemical property at bare GC electrodes. Upon the unfolding of Hb induced by the denaturant of guanidine hydrochloride (GdnHCl), the fifth coordinative bond between the heme groups and the residue of the polypeptides (His-F8) is broken, and as a result, the heme groups initially buried deeply in the hydrophobic pockets dissociate from the polypeptide chains and are reduced electrochemically at GC electrodes, which can be used to probe the unfolding of Hb.

Label-free and sequence-specific DNA detection down to a picomolar level with carbon nanotubes as support for probe DNA.

This study describes a simple and label-free electrochemical impedance spectroscopic (EIS) method for sequence-specific detection of DNA by using single-walled carbon nanotubes (SWNTs) as the support for probe DNA. SWNTs are confined onto gold electrodes with mixed self-assembly monolayers of thioethanol and cysteamine. Single-stranded DNA (ssDNA) probe is anchored onto the SWNT support through covalent binding between carboxyl groups at the nanotubes and amino groups at 5' ends of ssDNA.

Determination of monoamine neurotransmitters and their metabolites in a mouse brain microdialysate by coupling high-performance liquid chromatography with gold nanoparticle-initiated chemiluminescence.

Our previous work showed that gold nanoparticles could trigger chemiluminescence (CL) between luminol and AgNO3. In the present work, the effect of some biologically important reductive compounds, including monoamine neurotransmitters and their metabolites, reductive amino acids, ascorbic acid, uric acid, and glutathione, on the novel CL reaction were investigated for analytical purpose. It was found that all of them could inhibit the CL from the luminol-AgNO3-Au colloid system.

Physiologically relevant online electrochemical method for continuous and simultaneous monitoring of striatum glucose and lactate following global cerebral ischemia/reperfusion.

This study demonstrates a new electroanalytical method with a high physiological relevance for simultaneous online monitoring of glucose and lactate in the striatum of the rat brain following global cerebral ischemia/reperfusion. The online analytical method is based on the efficient integration of in vivo microdialysis sampling with an online selective electrochemical detection with the electrochemical biosensors with dehydrogenases, i.e.

Dynamic regional changes of extracellular ascorbic acid during global cerebral ischemia: studied with in vivo microdialysis coupled with on-line electrochemical detection.

The morphologic and functional outcomes of cerebral ischemia generally result from the acute neurochemical changes that occur 1 h after cerebral ischemia. As one of the small chemical species, ascorbic acid (AA) is involved in almost all kinds of neurochemical processes in acute cerebral ischemia. To understand the neurochemical processes in global cerebral ischemia, this study compares the dynamic regional changes of extracellular AA level, with in vivo microdialysis coupled with on-line electrochemical detection, in four different brain regions, 1 h after global cerebral ischemia induced by two-vessel occlusion (2-VO).

Gold nanoparticle/alkanedithiol conductive films self-assembled onto gold electrode: Electrochemistry and electroanalytical application for voltammetric determination of trace amount of catechol.

This paper describes novel electrochemical properties of gold nanoparticles/alkanedithiol conductive films and their electroanalytical applications for voltammetric determination of trace amount of one kind of environmental pollutants, catechol. The conductive films are prepared by closely packing 12-nm diameter gold nanoparticles (Au-NPs) onto Au electrodes modified with the self-assembled monolayers (SAMs) of alkanedithiols (i.e.

An electrochemical sensor for 3,4-dihydroxyphenylacetic acid with carbon nanotubes as electronic transducer and synthetic cyclophane as recognition element.

A new electrochemical sensor was demonstrated for selective sensing of 3,4-dihydroxyphenylacetic acid (DOPAC) through a non-oxidative mechanism by using single-walled carbon nanotubes (SWNTs) as the electronic transducer and a synthetic cyclophane electron acceptor as the recognition element.

Aptamer-based electrochemical sensors that are not based on the target binding-induced conformational change of aptamers.

This study describes a new kind of aptamer-based electrochemical sensor that is not based on the target binding-induced conformational change of the aptamers by using a 15-mer thrombin-binding aptamer (5'-GGTTGGTGTGGTTGG-3') as the model oligonucleotide. The sensors are developed by first self-assembling the aptamer (i.e.

Change of extracellular ascorbic acid in the brain cortex following ice water vestibular stimulation: an on-line electrochemical detection coupled with in vivo microdialysis sampling.

Background: Ascorbic acid (AA) represents one of the most important enzyme co-factors, antioxidants and neuromodulators and plays an important role in the cerebral system. Increasing evidence has suggested that AA could treat certain kinds of vertigo diseases such as Meniere's disease. To elucidate the neurochemical functions associated with AA in vertigo, the change of extracellular AA in the brain cortex following caloric vestibular stimulation (CVS) was evaluated.

In situ cationic ring-opening polymerization and quaternization reactions to confine ferricyanide onto carbon nanotubes: a general approach to development of integrative nanostructured electrochemical biosensors.

This study demonstrates a new and relatively general route to the development of multiwalled carbon nanotube (MWNT)-based integrative electrochemical biosensors by confining ferricyanide redox mediator onto MWNTs. The ferricyanide-confined MWNTs are synthesized first through grafting of epoxy chloropropane onto MWNTs with in situ cationic ring-opening polymerization and then introducing the positively charged methylimidazolium moieties into the grafted polymer with a quaternization reaction. The grafted polymers with positively charged methylimidazolium moieties tethered onto MWNTs can essentially be used to confine redox-active ferricyanide onto MWNTs to form a redox mediator-confined nanocomposite with a good stability and excellent electrochemical property.