WO2006086388A2 - Trace gas sensor with reduced degradation - Google Patents
Trace gas sensor with reduced degradation Download PDFInfo
- Publication number
- WO2006086388A2 WO2006086388A2 PCT/US2006/004292 US2006004292W WO2006086388A2 WO 2006086388 A2 WO2006086388 A2 WO 2006086388A2 US 2006004292 W US2006004292 W US 2006004292W WO 2006086388 A2 WO2006086388 A2 WO 2006086388A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sensing element
- environment
- oxygen
- less
- analyte
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/483—Physical analysis of biological material
- G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath
Definitions
- This invention resides in the field of sensors for detecting and measuring the concentration of gaseous analytes.
- Trace gas analysis is of value in many applications, including the diagnosis and management of physiological conditions.
- a change in nitric oxide (NO) concentration in the exhaled breath of a person suffering from asthma can indicate a change in the level of inflammation in the airway of the person, which in turn can indicate an increase in the likelihood of an asthma attack.
- Another example of a trace gas in exhaled breath that is indicative of an abnormal physiological condition is carbon monoxide.
- a rise in the carbon monoxide level in exhaled breath can be an early sign of the onset of hemolytic jaundice.
- a still further example is hydrogen, a rise in which can indicate malabsorption of carbohydrate.
- these gases are present at concentrations in the parts per billion (ppb) range, and changes within this range can indicate abnormalities before they can be detected at the parts per million range.
- ppb parts per billion
- Various sensors have been developed to measure the concentrations of different gaseous analytes. Some of these sensors contain bioactive substances, notably proteins, which undergo measurable changes upon contact with gaseous analytes and can therefore be termed "chemical transducers” since they transform the change into a signal that can be read and quantified.
- bioactive substance is cytochrome c, which undergoes an optically quantifiable change in response to NO.
- Certain sensors that utilize cytochrome c include this protein in encapsulated form in a xerogel (a dry stabilized sol-gel).
- degradation is used herein to denote a loss in the functionality of the protein, including the responsivity of the protein to the analyte in terms of both the magnitude of the change that can be detected and the time required for the change to occur.
- the sensor may have degraded to the point of being useless, i.e., incapable of producing a meaningful or reliable analysis, by the time the user is ready to perform the analysis or even by the time the user obtains a unit containing the sensor.
- cytochrome c for example, a loss of responsivity to NO is evidenced by a loss in the magnitude of the soret peak, which is the spectral peak of the iron porphyrin, the part of the protein that binds NO, and is centered around 400 nm.
- This degradation has been found to limit the utility of cytochrome c as a sensor in certain circumstances. While the rate of degradation appears to vary with temperature, the mechanism and overall cause of the degradation are unknown. Sensors that display a rapid response are particularly susceptible to degradation. This is true for example in certain cytochrome c elements that are disclosed in the citations above, particularly such elements that are able to generate a signal in less than five minutes of exposure to NO.
- cytochrome c as a sensor for NO, and other analyte-binding proteins that display degradation over time, can be reduced by controlling the exposure of the protein to oxygen. This is particularly true in the case of cytochrome c-containing sensors that display a rapid response, as stated above. Accordingly, this invention resides in the storage or packaging of the sensor, or the storage or packaging of devices containing the sensor, in a low-oxygen or substantially oxygen-free environment.
- oxygen as used in this specification and the appended claims denotes molecular oxygen as opposed to an oxygen atom or atoms covalently bonded to other atoms.
- low-oxygen environment refers to oxygen levels that are below the oxygen level in ambient air, i.e., significantly below 21% by volume. Preferred definitions of a low-oxygen environment are 10% or less, 5% or less, and 1% or less, all by volume.
- substantially oxygen-free denotes oxygen levels that are either zero or below the limits of detection of the analytical detection method used or available for use in the manufacturing, storage, or shipping environment. Depending on the detection method, the lower detection limit can be 0.1% by volume, 50 ppm by volume, 1 ppm by volume, or 0.1 ppm by volume.
- the senor is also maintained in an environment in which the relative humidity is 6% or less, preferably 3% to 6%, and currently 3%. In certain other embodiments of the invention, the relative humidity is maintained at 1% or less, more preferably 0.5% or less, and most preferably 0.1% or less. All values in this paragraph and the appended claims are approximate; the value shown for the digit of the lowest order of magnitude represents a rounded-off value.
- FIG. 1 is a graph showing the degradation over time of a cytochrome c sensor for NO.
- the y-axis represents the change in absorbance in the sensor after 90 seconds when the humidity in the environment surrounding the sensor is maintained at 200 ppm water and the sensor is reacted with 500 ppb NO.
- the x-axis represents equivalent days using accelerated aging based on an acceleration model of reaction rate based on measurements of change at 30, 50 and 70 degrees Celsius.
- the circles represent data points and the solid line represents the Arrhenius-derived decay.
- FIG. 2 is a graph comparing the NO response at 7O 0 C for sensors aged in an ambient environment with the NO response of identical sensors aged under the same conditions except that the environment was oxygen-free.
- Relative humidity was maintained constant by the use of 3 A molecular sieve. Three sets of data are shown, one representing results obtained from 7 days of exposure to 500 ppb NO (diamonds), a second representing results from 7 days of exposure to 23 ppm NO (squares), and the third representing results from 50 seconds of exposure to 500 ppb.
- Sensing elements and devices that will benefit from the present invention are those in which the binding species, i.e., the protein that generates the detectable change when contacted with the analyte, is suspended or encapsulated in a solid support matrix to form a sensing element that has a high surface area.
- Preferred sensing elements are those with a surface area that is greater than 300 m 2 /g, and most preferred are those with a surface area greater than 390 m 2 /g.
- Also preferred are those with a pore width (diameter) of 3nm to 6 run, and most preferably 3.5 nm to 5.8 nm.
- the surface area and pore width are both determined by the BET method well known among those skilled in the art.
- the matrix itself is preferably a xerogel formed by polymerization of tetramethyl orthosilicate, followed by aging and drying.
- the first row of data in the table represents the control test, in which a sensor was maintained at an equivalent of room temperature in an environment with an ambient oxygen level at 6% relative humidity, maintained by a saturated solution of LiBr.
- sensitivity was measured by exposing the sensor to air containing 500 ppb NO, both at the start of the test and after 220 equivalent days. By 220 days, the sensitivity had dropped by 78%, i.e., the sensitivity was only 22% of the sensitivity at the start of the test.
- the second row of data in the table represents a test in which an identical sensor was again maintained at room temperature but in an environment that was free of oxygen and in which the relative humidity was maintained at 0.1% by a 3 A molecular sieve. Again, using air containing 500 ppb NO as the test composition, the sensor exhibited only a 10% drop in sensitivity, resulting in a sensitivity at the equivalent of 220 days that was 90% of the sensitivity at the start of the test. This confirms that the presence of molecular oxygen was the primary cause of the degradation in the first test, and suggests that the high relative humidity may have further contributed to the degradation. [0014]
- the degradative effect of oxygen can be controlled in a variety of ways.
- a low-oxygen or oxygen- free environment can be achieved by purging the sensor housing with nitrogen or another inert gas, and once purged, the housing can be sealed in an oxygen-free, i.e., oxygen-purged, packaging environment.
- Such purging can for example be achieved with five cycles of nitrogen, based on the volume of the sensor and the volume of the sensor housing.
- a vacuum can be applied to the housing, either with or without nitrogen purging.
- the senor can be sealed in an oxygen-impermeable housing or closure, and an oxygen absorber can be used to remove the oxygen from the housing or closure.
- an oxygen absorber is CR YO V AC® OS Film (Cryovac Inc., Duncan, South Carolina, USA).
- the oxygen absorber can be placed in the same packaging as a sealed sensor, particularly when the sealing around the sensor is of oxygen-permeable material that allows oxygen to be drawn through the sealing material by the oxygen absorber. Purging of the sensor housing is optional when an oxygen absorber is used.
- An oxygen absorber can also be used to remove oxygen from an unsealed sensor housing, to facilitate the diffusion of oxygen to the absorber.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2006212799A AU2006212799A1 (en) | 2005-02-07 | 2006-02-06 | Trace gas sensor with reduced degradation |
EP06720442A EP1851526A4 (en) | 2005-02-07 | 2006-02-06 | Trace gas sensor with reduced degradation |
CA002596488A CA2596488A1 (en) | 2005-02-07 | 2006-02-06 | Trace gas sensor with reduced degradation |
JP2007554327A JP2008530534A (en) | 2005-02-07 | 2006-02-06 | Trace gas sensor with reduced degradation |
NO20074074A NO20074074L (en) | 2005-02-07 | 2007-08-07 | Tracer sensor with reduced degradation |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/053,046 US20060174691A1 (en) | 2005-02-07 | 2005-02-07 | Method of controlling degradation of trace gas sensors |
US11/053,046 | 2005-02-07 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2006086388A2 true WO2006086388A2 (en) | 2006-08-17 |
WO2006086388A3 WO2006086388A3 (en) | 2007-03-15 |
Family
ID=36778560
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2006/004292 WO2006086388A2 (en) | 2005-02-07 | 2006-02-06 | Trace gas sensor with reduced degradation |
Country Status (7)
Country | Link |
---|---|
US (2) | US20060174691A1 (en) |
EP (1) | EP1851526A4 (en) |
JP (1) | JP2008530534A (en) |
AU (1) | AU2006212799A1 (en) |
CA (1) | CA2596488A1 (en) |
NO (1) | NO20074074L (en) |
WO (1) | WO2006086388A2 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB0717433D0 (en) * | 2007-09-07 | 2007-10-17 | Bedfont Scient Ltd | Apparatus and method |
JP5240954B2 (en) | 2010-08-03 | 2013-07-17 | パナソニックヘルスケア株式会社 | Nitric oxide detection element |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS56152417A (en) * | 1980-04-28 | 1981-11-26 | Furointo Sangyo Kk | Preparation of cytochrome c pharamaceutical for internal use |
JPS5721315A (en) * | 1980-07-15 | 1982-02-04 | Ookura Seiyaku Kk | Stable solid preparation of cytochrome c and its preparation |
US5096813A (en) * | 1988-07-18 | 1992-03-17 | Massachusetts Institute Of Technology | Visual indicator system |
JPH0298669A (en) | 1988-10-04 | 1990-04-11 | Fujikura Ltd | Semiconductor acceleration sensor |
US5421981A (en) * | 1991-06-26 | 1995-06-06 | Ppg Industries, Inc. | Electrochemical sensor storage device |
US5520545A (en) * | 1994-11-21 | 1996-05-28 | The Whitaker Corporation | Variable orientation, surface mounted hermaphroditic connector |
US6010459A (en) * | 1996-04-09 | 2000-01-04 | Silkoff; Philip E. | Method and apparatus for the measurement of components of exhaled breath in humans |
US6787366B1 (en) * | 1996-12-11 | 2004-09-07 | The United States Of America As Represented By The Secretary Of The Army | Microspot test kit and method for chemical testing |
DE19960338A1 (en) * | 1999-12-15 | 2001-07-05 | Bosch Gmbh Robert | Gas sensor for determining the concentration of gas components in gas mixtures and its use |
US7220387B2 (en) * | 2002-07-23 | 2007-05-22 | Apieron Biosystems Corp. | Disposable sensor for use in measuring an analyte in a gaseous sample |
US20040017570A1 (en) * | 2002-07-23 | 2004-01-29 | Bhairavi Parikh | Device and system for the quantification of breath gases |
US20050053549A1 (en) * | 2003-09-10 | 2005-03-10 | Aperon Biosystems Corp. | Method for treating airway disorders |
US7325409B2 (en) * | 2004-03-24 | 2008-02-05 | Espinosa Edward P | Vacuum storage apparatus with sliding drawers |
-
2005
- 2005-02-07 US US11/053,046 patent/US20060174691A1/en not_active Abandoned
-
2006
- 2006-02-06 JP JP2007554327A patent/JP2008530534A/en active Pending
- 2006-02-06 WO PCT/US2006/004292 patent/WO2006086388A2/en active Application Filing
- 2006-02-06 EP EP06720442A patent/EP1851526A4/en not_active Withdrawn
- 2006-02-06 US US11/348,925 patent/US7278291B2/en active Active
- 2006-02-06 CA CA002596488A patent/CA2596488A1/en not_active Abandoned
- 2006-02-06 AU AU2006212799A patent/AU2006212799A1/en not_active Abandoned
-
2007
- 2007-08-07 NO NO20074074A patent/NO20074074L/en not_active Application Discontinuation
Non-Patent Citations (2)
Title |
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None |
See also references of EP1851526A4 |
Also Published As
Publication number | Publication date |
---|---|
JP2008530534A (en) | 2008-08-07 |
EP1851526A2 (en) | 2007-11-07 |
US20060191321A1 (en) | 2006-08-31 |
NO20074074L (en) | 2007-09-05 |
AU2006212799A1 (en) | 2006-08-17 |
WO2006086388A3 (en) | 2007-03-15 |
US20060174691A1 (en) | 2006-08-10 |
CA2596488A1 (en) | 2006-08-17 |
US7278291B2 (en) | 2007-10-09 |
EP1851526A4 (en) | 2009-06-17 |
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