Electrochemical sensor for superoxide anion radical using polymeric iron porphyrin complexes containing axial 1-methylimidazole ligand as cytochromec mimics

Electrochemical Biosensors Employing Natural and Artificial Heme Peroxidases on Semiconductors

Heme peroxidases are widely used as biological recognition elements in electrochemical biosensors for hydrogen peroxide and phenolic compounds. Various nature-derived and fully synthetic heme peroxidase mimics have been designed and their potential for replacing the natural enzymes in biosensors has been investigated. The use of semiconducting materials as transducers can thereby offer new opportunities with respect to catalyst immobilization, reaction stimulation, or read-out. This review focuses on approaches for the construction of electrochemical biosensors employing natural heme peroxidases as well as various mimics immobilized on semiconducting electrode surfaces. It will outline important advances made so far as well as the novel applications resulting thereof.

A Reactive Oxygen/Nitrogen Species Sensor Fabricated from an Electrode Modified with a Polymerized Iron Porphyrin and a Polymer Electrolyte Membrane

We have developed an electrochemical reactive oxygen/nitrogen species sensor that can detect superoxide anion radicals (O₂^-•) and nitric oxide (NO). The reactive oxygen/nitrogen species sensor was fabricated by surface modification of an electrode with polymerized iron tetrakis(3-thienyl)porphyrin (FeT3ThP), and it can detect either O₂^-• or NO by switching the applied potential. Furthermore, we fabricated a sensor with improved selectivity by coating a Nafion^® film onto the poly(FeT3ThP)-modified electrode. An interference current caused by NO₂^- was seen for the poly(FeT3ThP)-modified electrode, while the interference current was significantly reduced at the Nafion^®/poly(FeT3ThP)-modified electrode, leading to improved selectivity for NO detection. The current response at the Nafion^®/poly(FeT3ThP)-modified electrode exhibited good linearity in the O₂^-• and NO concentration ranges 1.3 - 4.1, and 0.5 - 10 μM, respectively. The Nafion^®/poly(FeT3ThP)-modified and poly(FeT3ThP)-modified electrodes are highly versatile, because these electrodes can detect either O₂^-• or NO by switching the applied potential. Since the Nafion^®/poly(FeT3ThP)-modified and poly(FeT3ThP)-modified electrodes contain no bio-derived compounds, the reactive oxygen/nitrogen species sensor should be safe even when it is used in vivo.

Real-time monitoring of superoxide anion radical generation in response to wounding: electrochemical study

Background

The growth and development of plants is deleteriously affected by various biotic and abiotic stress factors. Wounding in plants is caused by exposure to environmental stress, mechanical stress, and via herbivory. Typically, oxidative burst in response to wounding is associated with the formation of reactive oxygen species, such as the superoxide anion radical (O₂^•−), hydrogen peroxide (H₂O₂) and singlet oxygen; however, few experimental studies have provided direct evidence of their detection in plants. Detection of O₂^•− formation in plant tissues have been performed using various techniques including electron paramagnetic resonance spin-trap spectroscopy, epinephrine-adrenochrome acceptor methods, staining with dyes such as tetrazolium dye and nitro blue tetrazolium (NBT); however, kinetic measurements have not been performed. In the current study, we provide evidence of O₂^•− generation and its kinetics in the leaves of spinach (Spinacia oleracea) subjected to wounding.

Methods

Real-time monitoring of O₂^•− generation was performed using catalytic amperometry. Changes in oxidation current for O₂^•− was monitored using polymeric iron-porphyrin-based modified carbon electrodes (φ = 1 mm) as working electrode with Ag/AgCl as the reference electrode.

Result

The results obtained show continuous generation of O₂^•− for minutes after wounding, followed by a decline. The exogenous addition of superoxide dismutase, which is known to dismutate O₂^•− to H₂O₂, significantly suppressed the oxidation current.

Conclusion

Catalytic amperometric measurements were performed using polymeric iron-porphyrin based modified carbon electrode. We claim it to be a useful tool and a direct method for real-time monitoring and precise detection of O₂^•− in biological samples, with the potential for wide application in plant research for specific and sensitive detection of O₂^•−.

Hyperoxia suppresses excessive superoxide anion radical generation in blood, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats: laboratory study

This study used an electrochemical O2. sensor to investigate the effects of hyperoxia on generation of the superoxide radical (O2.) in the jugular vein during forebrain I/R in rats. Twenty-eight male Wistar rats were allocated to a sham group (n = 7; sham-treated rats with inspired oxygen fraction [FiO2] of 0.4), a hemorrhagic shock and reperfusion (HS/R) group (n = 7; HS without carotid artery occlusion and reperfusion with FiO2 of 0.4), a normoxia group (n = 7; forebrain ischemia produced by bilateral carotid arteries occlusion with HS and reperfusion with FiO2 of 0.4), and a hyperoxia group (n = 7; forebrain ischemia with FiO2 of 0.4 and reperfusion with FiO2 of 1.0). The jugular venous O2. current was measured for 10 min during forebrain ischemia and for 120 min after reperfusion. The O2. current increased gradually during forebrain ischemia in the three groups other than the sham group. Immediately after reperfusion, the current showed a marked increase in the normoxia group and a pronounced decrease in the hyperoxia group. Levels of brain and plasma malondialdehyde, high-mobility group box 1 protein, and intercellular adhesion molecule 1 were significantly attenuated in the hyperoxia group relative to those in the normoxia group. In conclusion, hyperoxia suppressed jugular venous O2. generation and malondialdehyde, high-mobility group box 1, and intercellular adhesion molecule 1 in the brain and plasma in the acute phase of cerebral I/R. Thus, the administration of 100% oxygen immediately after reperfusion suppresses oxidative stress and early inflammation in cerebral I/R.

Urinary trypsin inhibitor suppresses excessive superoxide anion radical generation in blood, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats

OBJECTIVES

To investigate the effects of ulinastatin, a urinary trypsin inhibitor (UTI), on jugular venous superoxide radical (O₂⁻·) generation, oxidative stress, early inflammation, and endothelial activation in forebrain ischemia/reperfusion (FBI/R) rats.

METHODS

Fourteen Wistar rats were allocated to a control group (n = 7) and a UTI group (n = 7). Throughout the experiments, O₂⁻· in the jugular vein was measured by the produced current using a novel electrochemical O₂⁻· sensor. Forebrain ischemia was induced by occlusion of the bilateral common caroti darteries with hemorrhagic hypotension for 20 min, followed by reperfusion. In the UTI group, UTI (5 U/g) was administered intravenously immediately after reperfusion. At 60 min after reperfusion, plasma and brain were harvested, and malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) were measured.

RESULTS

O₂⁻· current increased gradually during forebrain ischemia in both groups. The current increased markedly in the control group immediately after reperfusion but was significantly attenuated in the UTI group after reperfusion. Brain and plasma malondialdehyde, HMGB1, and ICAM-1 were significantly attenuated in the UTI group compared with those in the control group, except for brain HMGB1, which was associated with the amount of O₂⁻· generated during FBI/R.

DISCUSSION

UTI suppressed jugular venous O₂⁻· generation, oxidative stress, early inflammation, and endothelial activation in FBI/R rats. Therefore, UTI might be a useful agent for the therapy of the cerebral ischemia/reperfusion pathophysiology.

Urinary trypsin inhibitor suppresses excessive generation of superoxide anion radical, systemic inflammation, oxidative stress, and endothelial injury in endotoxemic rats

OBJECTIVE AND DESIGN

The protective effects of ulinastatin, a human urinary trypsin inhibitor (UTI), against superoxide radical (O(2)(-*)) generation, systemic inflammation, lipid peroxidation, and endothelial injury were investigated in endotoxemic rats.

MATERIALS AND TREATMENT

Twenty-one Wistar rats were allocated to a control group, a UTI group, and a sham group. A bolus of lipopolysaccharide (LPS; 3 microg/g) was administered intravenously to the control group, a bolus of LPS and UTI (5 U/g) to the UTI group, and a bolus of saline to the sham group.

METHODS

The O(2)(-*) generated was measured as the current in the right atrium using an electrochemical O(2)(-*) sensor. Plasma nitrite, high mobility group box 1 (HMGB1), tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, malondialdehyde, and soluble intercellular adhesion molecule-1 (sICAM-1) were measured 360 min after LPS administration.

RESULTS

The O(2)(-*) current increased in the control group and was significantly attenuated in the UTI group after 55 min (P < 0.05 at 55-60 min, P < 0.01 at 65-360 min). Plasma nitrite, HMGB1, TNF-alpha, IL-6, malondialdehyde, and sICAM-1 were attenuated in the UTI group.

CONCLUSIONS

UTI suppressed excessive O(2)(-*) generation, systemic inflammation, lipid peroxidation, and endothelial injury in endotoxemic rats.

Cholinergic agonist physostigmine suppresses excessive superoxide anion radical generation in blood, oxidative stress, early inflammation, and endothelial injury in rats with forebrain ischemia/reperfusion

The cholinergic anti-inflammatory pathway is reportedly important in modulating the inflammatory response in local and systemic diseases, including ischemia/reperfusion pathophysiology. In this study, we investigated the effects of the cholinergic agonist, physostigmine, on jugular venous superoxide radical (O(2)(-)) generation, oxidative stress, early inflammation, and endothelial activation during forebrain ischemia/reperfusion (FBI/R) in rats. Fourteen male Wistar rat were allocated to the control group (n=7) or physostigmine group (n=7). The physostigmine group received 80 ng/g physostigmine intraperitoneally 24 h and 1 h before forebrain ischemia was established. The jugular venous O(2)(-) current was measured for 10 min during forebrain ischemia and for 120 min after reperfusion. The O(2)(-) current increased gradually during forebrain ischemia in both groups. The current increased markedly immediately after reperfusion in the control group but was significantly attenuated in the physostigmine group after reperfusion. Brain and plasma malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule 1 (ICAM1) were significantly attenuated in the physostigmine group compared with the control group, except for brain HMGB1. The amount of O(2)(-) generated during FBI/R correlated with malondialdehyde, HMGB1, and ICAM1 in both the brain and plasma. In conclusion, the cholinergic agonist physostigmine suppressed jugular venous O(2)(-) generation, oxidative stress, early inflammation, and endothelial activation in the brain and plasma in the acute phase of cerebral ischemia/reperfusion. Therefore, the suppression of O(2)(-) is a key mechanism of the cholinergic anti-inflammatory pathway in the pathophysiology of cerebral ischemia/reperfusion.

Moderate hypothermia suppresses jugular venous superoxide anion radical, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats

The aim of this study was to assess the effect of moderate hypothermia (MH) on generation of jugular venous superoxide radical (O2-.), oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion (FBI/R) rats. Twenty-one Wistar rats were allocated to a control group (n=7, 37 degrees C), a pre-MH group (n=7, 32 degrees C before ischemia), and a post-MH group (n=7, 32 degrees C after reperfusion). MH was induced before induction of ischemia in the pre-MH group and just after reperfusion in the post-MH group. Forebrain ischemia was induced by occlusion of bilateral common carotid arteries with hemorrhagic hypotension for 10 min, followed by reperfusion. O(2)(-)(.) in the jugular vein was measured from the produced current using a novel O2-. sensor. The O2-. current showed a gradual increase during forebrain ischemia in the control and post-MH groups but was attenuated in the pre-MH group. Following reperfusion, the current showed a marked increase in the control group but was strongly attenuated in the pre- and post-MH groups. Concentrations of malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma 120 min after reperfusion in the pre- and post-MH groups were significantly lower than those in the control group, except for plasma HMGB1 in the post-MH group. In conclusion, MH suppressed O2-. measured in the jugular vein, oxidative stress, early inflammation, and endothelial injury in FBI/R rats.

In vivo real-time measurement of superoxide anion radical with a novel electrochemical sensor

The dynamics of superoxide anion (O(2)(-)) in vivo remain to be clarified because no appropriate method exists to directly and continuously monitor and evaluate O(2)(-) in vivo. Here, we establish an in vivo method using a novel electrochemical O(2)(-) sensor. O(2)(-) generated is measured as a current and evaluated as a quantified partial value of electricity (Q(part)), which is calculated by integration of the difference between the baseline and the actual reacted current. The accuracy and efficacy of this method were confirmed by dose-dependent O(2)(-) generation in xanthine-xanthine oxidase in vitro in phosphate-buffered saline and human blood. It was then applied to endotoxemic rats in vivo. O(2)(-) current began to increase 1 h after lipopolysaccharide, and Q(part) increased significantly for 6 h in endotoxemic rats, in comparison to sham-treated rats. These values were attenuated by superoxide dismutase. The generation and attenuation of O(2)(-) were indirectly confirmed by plasma lipid peroxidation with malondialdehyde, endothelial injury with soluble intercellular adhesion molecule-1, and microcirculatory dysfunction. This is a novel method for measuring O(2)(-) in vivo and could be used to monitor and treat the pathophysiology caused by excessive O(2)(-) generation in animals and humans.

Xanthine oxidase is one of the major sources of superoxide anion radicals in blood after reperfusion in rats with forebrain ischemia/reperfusion

We recently reported that excessive superoxide anion radical (O(2)(-)) was generated in the jugular vein during reperfusion in rats with forebrain ischemia/reperfusion using a novel electrochemical sensor and excessive O(2)(-) generation was associated with oxidative stress, early inflammation, and endothelial injury. However, the source of O(2)(-) was still unclear. Therefore, we used allopurinol, a potent inhibitor of xanthine oxidase (XO), to clarify the source of O(2)(-) generated in rats with forebrain ischemia/reperfusion. The increased O(2)(-) current and the quantified partial value of electricity (Q), which was calculated by the integration of the current, were significantly attenuated after reperfusion by pretreatment with allopurinol. Malondialdehyde (MDA) in the brain and plasma, high-mobility group box 1 (HMGB1) in plasma, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma were significantly attenuated in rats pretreated with allopurinol with dose-dependency in comparison to those in control rats. There were significant correlations between total Q and MDA, HMGB, or ICAM-1 in the brain and plasma. Allopurinol pretreatment suppressed O(2)(-) generation in the brain-perfused blood in the jugular vein, and oxidative stress, early inflammation, and endothelial injury in the acute phase of forebrain ischemia/reperfusion. Thus, XO is one of the major sources of O(2)(-)- in blood after reperfusion in rats with forebrain ischemia/reperfusion.

Fabrication of Sensor for Reactive Oxygen Species Using Gold Electrodes Modified with Electropolymerized Porphyrins and Application for Detection of Stress of Plants

Reactive Oxygen Spiecies (ROS) such as superoxide anion radical (.O(2)(-)) act as signals for the activation of stress-response and defense pathways. However, excess ROS generated by perturbing .O(2)(-) homeostasis stimulated many environmental stress, including intense light, drought, temperature stress, herbicides, induce high radical toxicity. Consequently, quantitative analysis of .O(2)(-) is a subject of intense research, since most of ROS are derived from .O(2)(-). Iron meso-tetrakis(3-thienyl)porphyrin complexes were electropolymerized onto a Au wire electrode. The modified Au electrode were applied to .O(2)(-) sensor to detect catalytic oxidation current of .O(2)(-) which was generated as an intermediate during the oxidation of xanthine by catalystic XOD. It was revealed that the sensor was quantitative to measure .O(2)(-). The modified Au electrode were applied to measure oxidation current of .O(2)(-) in mung beans under environmental stress condition. Plants were grown in atmosphere, 25 degrees C and in black darkness. The other plants were exposed to oxygen excess. The oxidation current of .O(2)(-) were increased plants were grown by high-oxygen environment compared to plants were grown at atmosphere. This experiment was indicated that environmental stress such as hyperoxia induced excess .O(2)(-) and Au wire sensor using iron porphyrin complexes is capable of .O(2)(-) detection in plants under environmental stresses.