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Spreading depolarization (SD) is one of the most common neuropathologic phenomena in the nervous system, relating to numerous diseases. However, real‐time monitoring the rapid chemical changes during SD to probe the molecular mechanism remains a great challenge. We develop a potentiometric dual‐channel microsensor for simultaneous monitoring of H2S and pH featuring excellent selectivity and spatiotemporal resolution. Using this microsensor we first observe real time changes of H2S and pH in the rat brain induced by SD. This changes of H2S are completely suppressed when the rat pre‐treats with aminooxyacetic acid (AOAA), a blocker to inhibit the H2S‐producing enzyme, indicating H2S fluctuation might be related to enzyme‐dependent pathway during SD and less pH‐dependent. This study provides a new perspective for studying the function of H2S and the molecular basis of SD‐associated diseases. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS)‐based therapeutic strategies play an important role in cancer treatment. However, in situ, real‐time and quantitative analysis of intracellular ROS in cancer treatment for drug screening is still a challenge. Herein we report one selective hydrogen peroxide (H2O2) electrochemical nanosensor, which is prepared by electrodeposition of Prussian blue (PB) and polyethylenedioxythiophene (PEDOT) onto carbon fiber nanoelectrode. With the nanosensor, we find that the level of intracellular H2O2 increases with NADH treatment and that increase is dose‐dependent to the concentration of NADH. High‐dose of NADH (above 10 mM) can induce cell death and intratumoral injection of NADH is validated for inhibiting tumor growth in mice. This study highlights the potential of electrochemical nanosensor for tracking and understanding the role of H2O2 in screening new anticancer drug. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S), is proposed as a cytoprotectant and gasotransmitter, involving in many physiological processes and regulating of some diseases. In addition, H2S is a small molecular with a minimum of steric hindrance compared with other reactive sulfur species. In physiological atmosphere, H2S is mainly existent in HS−, which has a strong nucleophilicity and reducing potency. It also can precipitate with some metal ions forming metallic sulfides with high precipitation coefficient. In recent years, the researchers have a desire to develop methods to achieve real‐time detection of H2S in vivo, further understanding the physiology and pathology of H2S. In this minireview, we summarize recent progress for detecting of H2S in brain or cell and briefly expound the principle of methods with the comparison of the different methods between performance and temporal resolution. [ABSTRACT FROM AUTHOR]

This study demonstrates a new electrochemical method for in vivo measurements of ascorbic acid (AA) in rat brain with multiwalled carbon nanotube (MWNT)-modified carbon fiber microelectrodes (CFMEs) based on the electrochemical property of MWNTs for facilitating AA oxidation. Cyclic voltammetry results indicate that the prepared MWNT-modified CFMEs possess a marked electrocatalyric activity toward AA oxidation and can be used for its selective measurement in the presence of other kinds of electroactive species coexisting in rat brain, such as 3,4-dihydroxyphenylacetic acid, uric acid, and 5-hydroxytryptamine. The selectivity of the MWNT-modified CFMEs toward AA measurement is further studied in vivo by exogenously infusing ascorbate oxidase into the brain, and the results confirm that the prepared electrodes are selective and can thus be used for reliable in vivo measurements of AA in rat brain, combined with their good stability during in vivo measurements. The basal level of striatum AA is determined to be 0.20 [+ or -] 0.05 mM (n = 3). The application of the voltammetric method with the MWNT-modified CFMEs is preliminarily demonstrated for in vivo observation of homeostatic regulation of striatum AA with exogenous infusion of AA into the brain.

This study describes a novel analytical system integrating in vivo microdialysis sampling with a radial thin-layer flow cell with a single-walled carbon nanotube (SWNT)-modified glassy carbon electrode as working electrode for continuous and on-line monitoring of ascorbate depletion in the rat striatum induced by global ischemia. The SWNTs, especially those after vacuum heat treatment at 500 [degrees]C, are found to be able to enhance the electron-transfer kinetics of ascorbate oxidation at a low potential (ca. -50 mV) and possess a strong ability against electrode fouling. These properties essentially make it possible to determine ascorbate with a good stability and high selectivity against catecholamines and their metabolites and other electroactive species of physiological levels. While being integrated with in vivo microdialysis to assemble an on-line analytical system, the electrode is proved useful for continuous and sensitive monitoring of the basal dialysate level of ascorbate and its depletion in the rat striatum induced by global ischemia. The basal dialysate level of ascorbate is determined to be 5.0 [+ or -] 0.5 [micro]M (n = 5) and a 50 [+ or -] 10% (n = 3) depletion is recorded for the basal ascorbate after 4 h of global ischemia.

Nanocomposite electrodes made of sol-gel-derived ceramic--carbon nanotube are fabricated by doping mutli-walled carbon nanotubes (MWNTs) into a silicate gel matrix. The electrochemical behavior and potential electrochemical applications of the ceramic--carbon nanotube nanocomposite electrodes (CCNNEs) are also studied. The as-prepared CCNNEs exhibit a tunable dimension ranging from conventional electrode to nanoelectrode ensemble (NEE), depending on the amount of the MWNT dispersed in the silica sol and finally doped within the gel matrix. A high content of the MWNT (i.e., higher than 1.5 mg/mL in the sol) leads to the formation of the CCNNE characteristic of an electrode of conventional dimension, while a low content (typically lower than 0.10 mg/mL) essentially yields the CCNNE like a nanoelectrode ensemble. The NEE is demonstrated to possess good electrocatalytic activity toward the oxidation of ascorbic acid (AA), and the CCNNE of conventional dimension is found to possess remarkable electrocatalytic activity toward the oxidation of glutathione (both reduced and oxidized forms, GSH and GSSG). These properties of the CCNNEs essentially offer a new electrochemical approach for the detection of AA, GSH, and GSSG. The possible essence of the tailor-made dimensions of the CCNNEs is also presented and discussed.

Alpha‐synuclein (α‐Syn) localizes at presynaptic terminal and modulates synaptic functions. Increasing evidence demonstrate that α‐Syn oligomers, forming at the early of aggregation, are cytotoxic and is thus related to brain neurodegenerative diseases. Herein, we find that vitamin D (VD) can reduce neurocytotoxicity. The reduced neurocytotoxicity might be attributed to the less amount of large‐sized α‐Syn oligomers inhibited by VD, measured by electrochemical collision at single particle level, which are not observable with traditionally ensembled method. Single‐cell amperometry (SCA) results show that VD can recover the amount of neurotransmitter release during exocytosis induced by α‐Syn oligomers, further verifying the neuroprotection of VD. Our study reveals the neuroprotective role of VD through inhibiting α‐Syn aggregation, which is envisioned to be of great importance in treatment and prevention of the neurodegenerative diseases. [ABSTRACT FROM AUTHOR]