Chemistry: analytical and immunological testing – Measurement of electrical or magnetic property or thermal... – By means of a solid body in contact with a fluid
Reexamination Certificate
2000-05-10
2002-09-24
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Measurement of electrical or magnetic property or thermal...
By means of a solid body in contact with a fluid
C422S068100, C422S082020
Reexamination Certificate
active
06455319
ABSTRACT:
BACKGROUND
The invention relates to sensors and sensor systems for detecting analytes in fluids.
There is considerable interest in developing sensors that act as analogs of the mammalian olfactory system (Lundstrom et al. (1991) Nature 352:47-50; Shurmer and Gardner (1992) Sens. Act. B 8:1-11; Shurmer and Gardner (1993) Sens. Act. B 15:32). In practice, most chemical sensors suffer from some interference by responding to chemical species that are structurally or chemically similar to the desired analyte. This interference is an inevitable consequence of the “lock” being able to fit a number of imperfect “keys”. Such interferences limit the utility of such sensors to very specific situations.
Arrays of broadly cross-reactive sensors have been exploited to produce response patterns that can be used to fingerprint, classify, and in some cases quantify analytes in fluids. Such arrays have been produced incorporating sensors including heated metal oxide thin film resistors (Gardner et al. (1991) Sens. Act. B4:117-121; Gardner et al. (1992) Sens. Act. B 6:71-75), polymer sorption layers on the surfaces of acoustic wave resonators (Grate and Abraham (1991) Sens. Act. B 3:85-111; Grate et al. (1993) Anal. Chem. 65:1868-1881), arrays of electrochemical sensors (Stetter et al. (1986) Anal. Chem. 58:860-866; Stetter et al. (1990) Sens. Act. B 1:43-47;Stetter et al. (1993) Anal. Chem. Acta 284:1-11), conductive polymers or composites that consist of regions of conductors and regions of insulating organic materials (Pearce et al. (1993) Analyst 118:371-377; Shurmer et al. (1991) Sens. Act. B 4:29-33; Doleman et al. (1998) Anal. Chem. 70:2560-2654; Lonergan et al. Chem. Mater.
1996, 8:2298).
Arrays of metal oxide thin film resistors, typically based on tin oxide (SnO
2
) films that have been coated with various catalysts, yield distinct, diagnostic responses for several vapors (Corcoran et al. (1993) Sens. Act. B 15:32-37). Surface acoustic wave resonators are extremely sensitive to both mass and acoustic impedance changes of the coatings in array elements. Attempts have also been made to construct arrays of sensors with conducting organic polymer elements that have been grown electrochemically through use of nominally identical polymer films and coatings. Moreover, Pearce et al., (1993) Analyst 118:371-377, and Gardner et al., (1994) Sensors and Actuators B 18-19:240-243 describe polypyrrole based sensor arrays for monitoring beer flavor. Shurmer (1990) U.S. Pat. No. 4,907,441, describes general sensor arrays with particular electrical circuitry. U.S. Pat. No. 4,674,320 describes a single chemoresistive sensor having a semi-conductive material selected from the group consisting of phthalocyanine, halogenated phthalocyanine and sulfonated phthalocyanine, which was used to detect a gas contaminant. Other gas sensors have been described by Dogan et al., Synth. Met. 60, 27-30 (1993) and Kukla, et al. Films. Sens. Act. B., Chemical 37, 135-140 (1996).
Sensor arrays formed from a plurality of composites that consist of regions of a conductor and regions of an insulating organic material, usually an organic polymer as described in U.S. Pat. No. 5,571,401, have sensitivities that are primarily dictated by the swelling-induced sorption of a vapor into the composite material, and analytes that sorb to similar extents produce similar swellings and therefore produce similar detected signals (Doleman, et al., (1998) Proc. Natl. Acad. Sci. U.S.A, 95, 5442-5447).
In these systems, the different responses from an analyte exposure to the array of sensors is used to identify the analyte. Other properties of the devices are designed to insure that otherwise all sensors are nominally equivalent so that the fluid containing the analyte is delivered to all sensors equally effectively—for example, at the same temperature—so that only the differences in sensors' response properties are being measured.
Although these sensor systems have some usefulness, there remains a need in the art for highly-selective sensor arrays for detecting analytes and resolving the components of complex mixtures.
SUMMARY OF THE INVENTION
The present artificial olfactory systems (or electronic noses) use arrays of many receptors to recognize an odorant. In such a configuration, the burden of recognition is not on highly specific receptors, as in the traditional “lock-and-key” molecular recognition approach to chemical sensing, but lies instead on the distributed pattern processing of the olfactory bulb and the brain. The system takes advantage of the spatio-temporal response differences between nominally identical sensors that are located at different positions in a fluid flow pattern.
In general, in one aspect, the invention provides a method of detecting an analyte in a fluid. The method includes providing a sensor array including at least a first sensor and a second sensor in an arrangement having a defined fluid flow path; exposing the sensor array to a fluid including an analyte by introducing the fluid along the fluid flow path; measuring a response for the first sensor and the second sensor; and detecting the presence of the analyte in the fluid based on a spatio-temporal difference between the responses for the first and second sensors.
Particular implementations of the invention can include one or more of the following features. Detecting the presence of the analyte can include generating a spatio-temporal response profile indicative of the presence of the analyte based on the spatio-temporal difference between the responses for the first and second sensors. The spatio-temporal response profile can be derived from time information indicating the dependence of sensor response on time. The first sensor can be exposed to the fluid before the second sensor, such that the response of the second sensor is delayed with respect to the response of the first sensor. The first sensor can be exposed to the fluid before the second sensor, such that the response of the second sensor is changed in amplitude with respect to the response of the first sensor. The first sensor can include a sensing material; and the response of the first sensor can be greater than the response of the second sensor for an analyte having a high affinity for the sensing material. The first and second sensors can be selected and arranged to provide a first delay between the response of the first sensor and the response of the second sensor upon exposure of the sensor array to a fluid including a first analyte and a second delay between the response of the first sensor and the response of the second sensor upon exposure of the sensor array to a fluid including a second analyte. Measuring the response can include measuring the delay between the response of the first sensor and the response of the second sensor, and the spatio-temporal difference between the responses for the first and second sensors can be derived from the delay. The method can include characterizing the analyte based on the spatio-temporal difference between the responses. Exposing the sensor array to the fluid can include introducing the fluid at a varying flow rate. Generating the spatio-temporal response profile can include generating flow information indicating the dependence of sensor response on flow rate. The sensor array can include a plurality of cross-reactive sensors. The sensor array can include a plurality of sensors selected from the group including surface acoustic wave sensors, quartz crystal resonators, metal oxide sensors, dye-coated fiber optic sensors, dye-impregnated bead arrays, micromachined cantilever arrays, composites having regions of conducting material and regions of insulating organic material, composites having regions of conducting material and regions of conducting or semiconducting organic material, chemically-sensitive resistor or capacitor films, metal-oxide-semiconductor field effect transistors, and bulk organic conducting polymeric sensors. The first and second sensors can include composites having regions of a conducting material and regions of an insulat
Briglin Shawn M.
Freund Michael S.
Lewis Nathan S.
California Institute of Technology
Fish & Richardson P.C.
Sines Brian
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