Real Time In Vivo Measurement of Ascorbate in the Brain Using Carbon Nanotube‐Modified Microelectrodes

Ferreira, Noely Evangelista; Santos, R. M.; Laranjinha, João; Barbosa, Rui M.

doi:10.1002/elan.201300053

Cited by 12 publications

(9 citation statements)

References 33 publications

(45 reference statements)

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“…To minimize the interference of undesirable electroactive compounds, the LOx-GOx MBA sites were modified with a poly-[ m -phenylenediamine] exclusion layer 25 . In spite of the specificity of LOx and GOx for the corresponding substrates, the presence of electroactive compounds in the brain extracellular space limits biosensor specificity, namely ascorbate which extracellular concentration range of 200–400 μM 26 – 28 . A typical response of the LOx-GOx MBA to lactate and glucose in the presence of high concentrations of ascorbate (0.5 mM) is depicted in Fig.…”

Section: Resultsmentioning

confidence: 99%

Neurometabolic and electrophysiological changes during cortical spreading depolarization: multimodal approach based on a lactate-glucose dual microbiosensor arrays

Lourenço

Ledo

Gerhardt

et al. 2017

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Spreading depolarization (SD) is a slow propagating wave of strong depolarization of neural cells, implicated in several neuropathological conditions. The breakdown of brain homeostasis promotes significant hemodynamic and metabolic alterations, which impacts on neuronal function. In this work we aimed to develop an innovative multimodal approach, encompassing metabolic, electric and hemodynamic measurements, tailored but not limited to study SD. This was based on a novel dual-biosensor based on microelectrode arrays designed to simultaneously monitor lactate and glucose fluctuations and ongoing neuronal activity with high spatial and temporal resolution. In vitro evaluation of dual lactate-glucose microbiosensor revealed an extended linear range, high sensitivity and selectivity, fast response time and low oxygen-, temperature- and pH- dependencies. In anesthetized rats, we measured with the same array a significant drop in glucose concentration matched to a rise in lactate and concurrently with pronounced changes in the spectral profile of LFP-related currents during episodes of mechanically-evoked SD. This occurred along with the stereotypical hemodynamic response of the SD wave. Overall, this multimodal approach successfully demonstrates the capability to monitor metabolic alterations and ongoing electrical activity, thus contributing to a better understanding of the metabolic changes occurring in the brain following SD.

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Section: Resultsmentioning

confidence: 99%

Neurometabolic and electrophysiological changes during cortical spreading depolarization: multimodal approach based on a lactate-glucose dual microbiosensor arrays

Lourenço

Ledo

Gerhardt

et al. 2017

Sci Rep

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“…The detection limit was as low as 10 μM, with a sensitivity of 0.85 mA mol –1 cm –2 . The current e-CNF-based microsensor demonstrated a low working potential, wide linear range, and high sensitivity. ,,, …”

Section: Results and Disucussionmentioning

confidence: 96%

Engineering Carbon Nanotube Fiber for Real-Time Quantification of Ascorbic Acid Levels in a Live Rat Model of Alzheimer’s Disease

et al. 2017

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Ascorbic acid (AA) levels are closely correlated with physiological and pathological events in brain diseases, but the mechanism remains unclear, mainly due to the difficulty of accurately analyzing AA levels in live brain. In this study, by engineering tunable defects and oxygen-containing species in carbon nanotubes, a novel aligned carbon nanotube fiber was developed as an accurate microsensor for the ratiometric detection of AA levels in live rat brains with Alzheimer's disease (AD). AA oxidation is greatly facilitated on the fiber surface at a low potential, leading to high sensitivity as well as high selectivity against potential sources of interference in the brain. Additionally, an unexpected, separate peak from the fiber surface remains constant as the AA concentration increases, enabling real-time and ratiometric detection with high accuracy. The results demonstrated that the AA levels were estimated to be 259 ± 6 μM in cortex, 264 ± 20 μM in striatum, and 261 ± 21 μM in hippocampus, respectively, in normal condition. However, the overall AA level was decreased to 210 ± 30 μM in cortex, 182 ± 5 μM in striatum, and 136 ± 20 μM in hippocampus in the rat brain model of AD. To the best of our knowledge, this work is the first to accurately detect AA concentrations in the brains of live animal model of AD.

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“…On the other hand, it has been reported that Vit C (ascorbate) is present in high concentrations in rat brain tissues; for example, the concentrations of Vit C in neurons, glia, and hippocampus are 10, 0.9, and 0.29 mM, respectively. , If the CAs coexist with Vit C in tissues, the rate of regeneration of α-Toc • is represented by eq . The α-TocH-regeneration reaction of CAs may compete with that of Vit C …”

Section: Discussionmentioning

confidence: 99%

Kinetic Study of Aroxyl-Radical-Scavenging and α-Tocopherol-Regeneration Rates of Five Catecholamines in Solution: Synergistic Effect of α-Tocopherol and Catecholamines

et al. 2016

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Detailed kinetic studies have been performed for reactions of aroxyl (ArO(•)) and α-tocopheroxyl (α-Toc(•)) radicals with five catecholamines (CAs) (dopamine (DA), norepinephrine (NE), epinephrine (EN), and 5- and 6-hydroxydopamine (5- and 6-OHDA)) and two catechins (epicatechin (EC) and epigallocatechin gallate (EGCG)) to clarify the free-radical-scavenging activity of CAs. Second-order rate constants (ks and kr) for reactions of ArO(•) and α-Toc(•) radicals with the above antioxidants were measured in 2-propanol/water (5:1, v/v) solution at 25.0 °C, using single- and double-mixing stopped-flow spectrophotometries, respectively. Both the rate constants (ks and kr) increased in the order NE < EN < DA < EC < 5-OHDA < EGCG < 6-OHDA. The ks and kr values of 6-OHDA are large and comparable to the corresponding values of ubiquinol-10 and sodium ascorbate, which show high free-radical-scavenging activity. The ultraviolet-visible absorption of α-Toc(•) (λmax = 428 nm), which was produced by the reaction of α-tocopherol (α-TocH) with ArO(•), disappeared under the coexistence of CAs due to the α-TocH-regeneration reaction. The results suggest that the CAs may contribute to the protection from oxidative damage in nervous systems, by scavenging free radicals (such as lipid peroxyl radical) and regenerating α-TocH from the α-Toc(•) radical.

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Real Time In Vivo Measurement of Ascorbate in the Brain Using Carbon Nanotube‐Modified Microelectrodes

Cited by 12 publications

References 33 publications

Neurometabolic and electrophysiological changes during cortical spreading depolarization: multimodal approach based on a lactate-glucose dual microbiosensor arrays

Neurometabolic and electrophysiological changes during cortical spreading depolarization: multimodal approach based on a lactate-glucose dual microbiosensor arrays

Engineering Carbon Nanotube Fiber for Real-Time Quantification of Ascorbic Acid Levels in a Live Rat Model of Alzheimer’s Disease

Kinetic Study of Aroxyl-Radical-Scavenging and α-Tocopherol-Regeneration Rates of Five Catecholamines in Solution: Synergistic Effect of α-Tocopherol and Catecholamines

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