Nitric oxide sensor
First Claim
1. A nitric oxide-specific electrode sensor, which comprises:
- an electrically conductive substrate whose amperometric response is substantially unaffected by the presence of nitric oxide; and
an adherent and substantially uniform electrochemically active polymeric coating formed on a surface of said electrically conductive substrate which interacts with NO to change the redox potential of NO and the electrode sensor.
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Abstract
An electrode sensor which may be used to specifically and quantitatively measure nitric oxide is provided, as well as a method of preparing and using such an electrode sensor to measure nitric oxide concentration in solution. A nitric oxide (NO) microsensor based on catalytic oxidation of NO comprises a thermally-sharpened carbon fiber with a tip diameter of about 0.5-0.7 μm coated with several layers of p-type semiconducting polymeric porphyrin and cationic exchanger deposited thereon. The microsensor, which can be operated in either the amperometric, voltammetric or coulometric mode utilizing a two or three electrode system, is characterized by a linear response up to about 300 μM, a response time better than 10 msec and a detection limit of about 10 nM. The sensor of the present invention also discriminates against nitrite, the most problematic interferant in NO measurements. The amount of NO released from a single cell can thus be selectively measured in situ by a porphyrinic microsensor of the invention. A larger scale sensor utilizing porphyrin and cationic exchanger deposited on larger fibers or wires, platinum mesh or tin indium oxide layered on glass, can also be employed when measurement of NO concentration in chemical media, tissue or cell culture is desired.
90 Citations
66 Claims
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1. A nitric oxide-specific electrode sensor, which comprises:
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an electrically conductive substrate whose amperometric response is substantially unaffected by the presence of nitric oxide; and an adherent and substantially uniform electrochemically active polymeric coating formed on a surface of said electrically conductive substrate which interacts with NO to change the redox potential of NO and the electrode sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An electrode sensor for detecting the presence of NO in an analytic solution, the electrode sensor detecting an electrical signal developed between the electrode sensor and a counterelectrode, the electrode sensor comprising:
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a) a conductive support having a catalytic surface for catalyzing NO oxidation and thereby generating a NO detection electrical signal; and b) a cationic exchanger disposed on the catalytic surface in contact with the analytic solution, the cationic exchanger allowing diffusion of NO therethrough but preventing the diffusion of anions to the catalytic surface that would mask the NO detection electrical signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A sensor system for measuring the level of NO in an analytic solution comprising:
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a) an electrode sensor comprising a conductive support coated with a conductive layer of catalytic material that will catalyze NO oxidation and generate a detection signal, and a layer of cationic exchanger disposed on the catalytic material and making the detection signal selective to NO; b) a counterelectrode; and c) an instrument for detecting an electrical signal developed between the electrode sensor and the counterelectrode in response to the oxidation of NO. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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- 39. A sensor for measuring the level of NO in an analytic solution comprising a conductive support coated with a plurality of layers of a polymeric metalloporphyrin for detecting oxides of nitrogen, and a coating of a cationic exchanger on the plurality of layers of metalloporphyrin, which cationic exchanger allows passage of NO but not anions of other nitrogen oxides and makes the sensor selective for NO.
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46. An electrode sensor for a sensor for measuring the level of NO in an analytic solution, the sensor measuring an electrical signal developed between the electrode sensor and a counterelectrode, the electrode sensor comprising:
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a) a conductive support having a catalytic coating thereon comprising a polymeric metalloporphyrin layer disposed thereon for catalyzing NO oxidation, the oxidation developing an electrical signal at said electrode; and b) a cationic exchanger layer comprising a chemically stable perfluorosulfonic acid ion exchange resin disposed on the layer of catalytic material and in contact with the analytic solution which cationic exchanger layer prevents the diffusion of interfering anions to the catalytic layer surface, which interfering anions would adversely affect the NO oxidation electrical signal.
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- 47. A method of manufacturing a nitric oxide-specific electrode sensor, which comprises contacting an electrically conductive substrate whose amperometric response is substantially unaffected by the presence of nitric oxide with a compound which forms an electrochemically active polymeric coating which interacts with NO to change the redox potential of NO and the electrode sensor.
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56. A method of directly measuring NO in an analytic solution generally comprising the steps of:
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a) providing an electrode sensor comprising a conductive support having a layer of catalytic material disposed thereon with a layer of a cationic exchanger disposed on the catalytic material; b) providing a counterelectrode; c) providing an instrument for measuring an electrical signal developed between the electrode sensor and the counterelectrode; d) placing the electrode sensor in the analytic solution; e) placing the counterelectrode in the analytic solution; and f) measuring the electrical signal developed between the electrode sensor and the counterelectrode. - View Dependent Claims (57, 58, 59)
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60. A nitric oxide-specific electrode sensor for detecting the quantity of NO in an analytic solution, the electrode sensor detecting an electrical signal developed between the electrode sensor and a counterelectrode, in strength in proportion to the quantity of NO in the analytic solution, the electrode sensor comprising:
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(a) an electrically conductive substrate whose amperometric response is substantially unaffected by the presence of nitric oxide; (b) an adherent and substantially uniform electrochemically active polymeric coating formed on a surface of said electrically conductive substrate, said electrochemically active polymeric coating interacting with NO in said analytical solution to change the redox potential of NO and the nitric oxide-specific electrode sensor, the change being in strength related to the quantity of NO in the analytic solution, and to generate an NO detection electrical signal in strength related to the quantity of NO in the analytic solution; and (c) a cationic exchanger disposed on a surface of said electrochemically active polymeric coating, the cationic exchanger being in contact with the analytic solution, the cationic exchanger allowing diffusion of NO therethrough but preventing the diffusion of anions to the surface of the electrochemically active polymeric coating that would mask the NO detection electrical signal;
wherein the sensor may be used quantitatively to measure the levels of NO present in the analytic solution. - View Dependent Claims (61, 62, 63, 64)
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65. A method of manufacturing a nitric oxidespecific electrode sensor, which comprises depositing a metalloporphyrin selected from among the group consisting of tetrakis (3-methoxy-4-hydroxyphenyl)porphyrin and meso-5'"'"'0-P-phenylene-2'"'"',3'"'"'-0-isopropylidine uridine-tri (n-methyl-4-pyridinium)porphyrin on an electrically conductive glass carbon fiber microelectrode having a tip approximately 1 μ
- m or less in diameter, by electrolytic polymerization, to an average surface coverage (Γ
) being in the approximate range of 0.7-1.2 nmol cm2, to form an electrochemically active polymeric coating on the fiber which interacts with NO to change the redox potential of NO and the electrode sensor, and applying a coating on the metalloporphyrin of a cationic exchanger which comprises a chemically stable perfluorosulfonic acid ion exchange resin that is permeable to nitric oxide and exludes nitrite. - View Dependent Claims (66)
- m or less in diameter, by electrolytic polymerization, to an average surface coverage (Γ
Specification