WO2000068670A1 - Method and system for remotely collecting and evaluating chemical/biochemical information - Google Patents

Abstract

The present invention provides a method and system for detecting analytes in a fluid sample in a system of interest. The method and system includes a sensor, which includes at least one reactant, having an integral detector. The detector detects spectroscopic changes of reactants as the fluid sample passes over the reactants. The spectroscopic changes are caused by an analyte present in the fluid sample interacting with reactants.

Description

METHOD AND SYSTEM FOR REMOTELY COLLECTING AND EVALUATING CHEMICAL/BIOCHEMICAL INFORMATION

Priority Claim This application claims the benefit of U.S. Provisional Application No.

60/133,230, entitled Method and System for Remotely Collecting and Evaluating

Chemical/Biochemical Information, filed on May 7, 1999.

Background of the Invention

1. Field of the Invention

The present invention relates to a method and device for the detection of

analytes. Preferably, the analytes are localized at the end of a probe suitable for

insertion into a body of interest. The body of interest may include a wide variety

of materials, including, but not limited to, biological systems, both living and

dead. Thus, the body of interest may be the interior of an animal (which term is

understood to include humans) or a plant. A body of interest could also be a

food product, the wash of a food product, as well as agricultural and/or

environmental materials.

The present invention allows one to acquire chemical/biochemical assays

in localized regions, such as proximate to internal organs or the interior of blood

vessels of a human or animal body. If the present invention includes a video

monitoring system, the present invention allows one to simultaneously acquire both optical information related to the condition of the body of interest, such as,

for example, the condition of internal organs or blood vessels, while also

providing chemical/biochemical assays of these localized regions. More

particularly, the present invention relates to the development of instrumentation

that may be used for both surgical and microsurgical applications, wherein

minimally invasive procedures may be completed with a high degree of

accuracy.

2. Brief Description of the Related Art

The development of smart sensors capable of discriminating different

analytes, toxins, and bacteria has become increasingly important for a wide

range of applications, including environmental, health and safety, remote

sensing, food/beverage and chemical processing applications. Sensors have

been developed that may detect a single analyte or multiple analytes. Sensors

for multiple analyte detection generally include an array of sensors. The

advantages of these array sensor systems are their ability to analyze multiple

analytes, and their ability to be "trained" to respond to new stimuli through the

use of specific receptor molecules and the ongoing development of new types of

receptor molecules. The on-site adaptive analysis capabilities afforded by array

based sensors displaying the capacity to sense and identify complex vapors

have been fashioned using a number of distinct transduction schemes. If the sensors sample air, as opposed to fluid, the sensors are generally

referred to as "electronic noses." Electronic noses generally include a housing

for sampling the air sample, which includes the array of sensors, and a system

for detecting changes to the sensors of the array. The choice of the type of

sensors is dependent on which analyte or how much of an analyte needs to be

identified.

Typically, in the housing for sampling the air sample, the air sample is

pulled by a vacuum pump through a tube into a small chamber which houses the

array of sensors. The tube may be comprised of plastic or stainless steel. In this

manner, the air sample contacts the sensor array, causing the sensors to react in

particular ways to the air sample. The system for detecting changes to the

sensor arrays is then utilized to detect in what ways each sensor reacts to that

particular air sample.

In some instances, a washing gas such as an alcohol vapor is applied to

the array to remove the air sample from the active surface of the sensors. In re-

useable sensor arrays, a reference gas may be utilized to place each sensor to a

known state in order to introduce another air sample to the sensors.

Typical electronic noses fall into five categories: conductivity sensors,

piezoelectric sensors, metal oxide silicon field effect transistor (MOSFET)

sensing devices, optical sensors and spectrometry-based sensing methods. There are two types of conductivity sensors: metal oxide semiconductors

and conducting polymer sensors. Metal oxide semiconductors have been

utilized more extensively and are widely available commercially, but conducting

polymer sensors are also commonly used and are easier to make than metal

oxide semiconductors because they do not need a heating element.

For a metal oxide semiconductor, the metal may be tin, zinc, titanium,

tungsten or iridium, one of which is doped with a noble metal catalyst such as

platinum or palladium. The doped semiconducting material is deposited between

two electrodes over a resistive heating element. The electrodes may be

platinum, aluminum or gold, while the substrate in which the resistive heater is

placed may be silicon, glass or plastic. The resistive heater is normally a

platinum metal trace or wire. The use of tin oxide sensors is described in U.S.

Patent No. 5,654,497, issued to Hoffheins et al. These sensors display the

capacity to identify and discriminate between a variety of organic vapors by

virtue of small site-to-site differences in response characteristics.

For a conducting polymer sensor, the polymer is generally from polymer

families of polypyrroles, thiophenes, indoles or furans. The conducting polymer

is electropolymerized between two electrodes by cycling the voltage between the

electrodes. Because conducting polymer sensors operate at ambient

temperature, they do not need a resistive heating element. For both types of conductivity sensors, a volatile organic compound

(VOC) is introduced to the active material (either the metal oxide or the polymer

material) and alters the conductivity of the active material. The change in

resistance across the electrodes is then measured using conventional electronic

circuitry. For metal oxide semiconductors, as a VOC passes over the active

material, the resistance between the electrodes changes in proportion to the

concentration of the VOC. For conducting polymer sensors, the conductivity of

the active polymer material changes in relation to its exposure to the VOC.

Another structure involves a series of conductive polymer layers

deposited onto metal contacting layers. When these sensors are exposed to

volatile reagents, some of the volatile reagents adsorb onto the surface of the

polymer layers, leading to small changes in the electrical resistance of these

layers. One can identify and quantify the volatile reagents in the air sample by

detecting the small changes in the electrical resistance. This detection process

takes only a few seconds, and sensitivities of parts-per-billion may be achieved.

This electronic nose system is described in U.S. Patent No. 5,698,089, issued to Lewis et al.

Disadvantages with metal oxide semiconductors include that the baseline

response of a semiconductor may drift over a period of time, and that the

sensors are susceptible to poisoning by sulfur compounds present in the air sample. Disadvantages with conducting polymer sensors is the difficulty and

time that must be spent to electropolymerize the active material, which may

result in variations between batches of sensors. Also, these sensors also tend to

drift over a period of time, and they are sensitive to humidity, which may mask

the responses to certain odorous VOCs.

The second type of electronic noses are piezoelectric sensors.

Piezoelectric sensors may be quartz crystal microbalance devices or surface

acoustic wave (SAW) devices. The quartz crystal microbalance devices are

comprised of a small resonating disk with metal electrodes on each side of the

disk, which are connected to a lead wire. The device resonates at a particular

frequency when excited with an oscillating signal. During manufacture, a

polymer coating material is applied to the disk to serve as an active sensing

material. When an air sample is introduced to the disk, the air sample is

absorbed by the polymer coating material, which increases the mass of the

device and thereby reduces the resonance frequency. The reduction in the

resonance frequency is inversely proportional to the mass of the air sample

absorbed by the polymer coating material. The type of air sample to be tested

will determine the type of polymer coating material utilized, and there are a large

number of polymer coating materials available. Surface acoustic wave devices are comprised of a piezoelectric

substance that has a planar surface. Two metal transducers are placed onto the

planer surface, on either side of a polymer coating material. A surface wave

travels over the planar surface of the device by applying an AC signal across one

of the metal transducers. When the surface wave reaches the second metal

transducer, the AC voltage is recreated, although the voltage is shifted in phase

as a result of the distance traveled. The phase shift depends, in part, on the

mass and absorption properties of the polymer coating material, which are

influenced in turn by the gas molecules absorbed.

Surface acoustic wave devices operate at much higher frequencies than

quartz crystal microbalance devices, and thus may generate larger changes in

frequency. However, surface acoustic wave devices may be less sensitive than

quartz crystal microbalance devices because the increased surface to volume

ratios means than signal to noise ratios are generally poorer. Disadvantages

with both types of piezoelectric sensors are their need for more complex

electronics as compared to conductivity sensors.

The third type of electronic noses are MOSFET devices. MOSFET

sensing devices generally include a p-type substrate with two n-doped regions

with metal contacts labeled source and drain. MOSFETs work on the principle

that a volatile organic compound may produce a reaction in a metal when the compound contacts the metal. The product of the reaction may diffuse through

the gate of the MOSFET to change the electrical properties of the device. The

sensitivity and selectivity of the MOSFET sensing devices depends on the type

and thickness of the metal utilized and operating the particular devices at

different temperatures. MOSFET sensing devices have not been commonly

utilized in commercial electronic nose systems. However, an advantage to

MOSFET sensing devices is that they can be made with IC fabrication

processes, thereby reducing batch to batch variations. A disadvantage to

MOSFET sensing devices is the need for the reaction products to penetrate the

metal layer. Thus, the sensing device must have a window to permit gas to

interact with the gate structure on the IC chip. Moreover, it is important to

maintain a seal for the chip's electrical connections in harsh environments.

The fourth type of electronic noses are optical fiber sensors. Optical fiber

sensors are generally comprised of glass fibers with a thin chemically active

material coating on the sides or ends of the fibers. The active material responds

with a change in color to the presence of volatile organic compounds. A light

source comprising one or more portions of the electromagnetic spectrum is

utilized to illuminate the active material. The active material contains chemically

active fluorescent dyes immobilized in an organic polymer matrix. As volatile

organic compounds interact with the active material, the polarity of the dyes is altered, and the dyes shift their fluorescent emission spectrum. When a pulse of

light from the light source interrogates the active material, the fluorescent dye

responds by emitting light at a different frequency. A light sensor detects the

emitted light and the presence of an analyte may be determined.

Advantages to optical sensors are that they are cheap and easy to

fabricate. In addition, it is possible to combine a fluorescent dye to antibody-

antigen binding, such that a specific molecule, and only that molecule, may be

detected. Disadvantages to optical sensors are the complexity of the

instrumentation control system, which makes these sensors cost more to

produce, as well as their limited life due to photobleaching.

The fifth type of electronic noses is based on spectrometry-based sensing

methods. For one type of spectrometer, a concentrated vapor is injected into the

spectrometer, and the spectrometer generates a spectral response which is

characteristic of that vapor. In another type, acousto-optic tunable filters are

utilized. These filters alter their light-filtering characteristics in response to a

change in voltage across their light transmission path. If the voltage is varied,

the transmission path of the light through the filter changes, as does the peak

wavelength of the light. The result is a time-varying signal that is a function of

the light spectrum of the incoming source. A sensor at the output detects a

characteristic profile for each odorant being examined. There are a wide variety of additional electronic nose sensor types whose

general operation is known to those practiced in the art. In all cases, however, it

should be recognized that a relatively small number of carefully chosen sensors

can effect tremendous discrimination between different compounds. Moreover,

each of the technologies discussed above lends themselves to miniaturization

and, in principle, can be combined with the electronic tongue components

discussed in the present application.

In many applications, it is necessary to identify and quantify analytes

present in either liquid or solid phase samples. In these applications, the sensor

is sometimes referred to as an "electronic tongue." Types of electronic tongues

sensors include those which have been referred to as "DNA on a chip," as well

as thin films, dyes or beads that act as receptor units, conducting polymers, and

pulse spectroscopy cells. A full description of each of these types of electronic

tongue sensors is beyond the scope of this invention, although systems based

on "DNA on a chip" technology and systems using thin films, dyes or beads that

act as receptor units are discussed herein. It is assumed that one of skill in the

art is familiar with these types of sensors.

Array sensors based on "DNA on a chip" technology have shown great

analytical promise. These devices possess a high density of DNA hybridization

sites that are affixed in a two-dimensional pattern on a planar substrate. To generate nucleotide sequence information, a pattern is created from unknown

DNA fragments binding to various hybridization sites. Both radiochemical and

optical methods have provided excellent detection limits for analysis of limited

quantities of DNA. Proceedings of the National Academy of Science, USA,

Stimpson, D.I.; Hoijer, J.V.; Hsieh, W.; Jou, C; Gardon, J.; Theriault, T.; Gamble,

R.; Baldeschwieler, J.D., 92, 6397 (1995). Although quite promising for the

detection of DNA fragments, these arrays have the disadvantage of having very

little sensitivity to smaller organic molecules. In addition, many of the analytes of

interest do not contain DNA components, and would thus not be detectable by

this type of sensor. Thus, there is a need for a flexible, non-DNA based sensor.

Optic sensors for evaluating one or more analytes in a fluid sample are

known in the art. For example, a system of analyzing fluid samples using an

array formed of heterogeneous, semi-selective thin films which function as

sensing receptor units is described in U.S. Patent No. 5,512,490, issued to Walt

et al. In particular, this patent discloses a support member with an optic array of

sensing receptor units positioned on the support member, wherein the sensing

receptor units react spectrally different with individual analytes in order to detect

analytes of interest.

Similarly, another way to analyze fluid samples is based on using optical

fibers to carry a plurality of dyes or beads where the dyes or beads function as sensing receptor units, such as described in, for example, U.S. Patents Nos.

5,244,636, issued to Walt et al. (dyes) and U.S. Patent No. 6,023,540, issued to

Walt et al. (beads) (hereafter "the Walt et al. patents"). Typically, the device

includes a single or a plurality of optical fibers. The end of each optical fiber may

be etched to form indentations. The beads are placed into these indentations, or

the dyes are deposited on the end of the optical fiber. The optical fiber provides

illumination to transmit light to the beads or dyes. A detector, such as a charge

coupled device (CCD) detector, detects the light emerging from the beads or

dyes to determine whether an analyte of interest is present in the fluid sample.

The Walt et al. patents disclose analyzing fluid samples in in vivo or in

vitro applications. These patents also disclose utilizing optical fiber strands to

provide imaging, as well as performing a chemical analysis of the fluid sample.

In particular, because the sensor is made of optical fibers, the sensor permits the

direct imaging and viewing of the area in which the sensor is placed. The

capability of the sensor to provide imaging and chemical analysis would allow

one to use a single sensor in an in vivo application, such as angioplasty, to be

able to see where the fiber is traveling to deliver the therapeutic treatment, to

use the fiber to deliver the therapeutic treatment, and to concurrently measure

the efficacy of the treatment. One disadvantage of the Walt et al. patents is that they require a

sufficiently large optical energy source to adequately transmit the optical signal

through the optical fiber. In particular, the Walt et al. patents disclose the use of

fluorescent markers to detect, which require high incident excitation energy to

cause the fluorescence. The use of fluorescent markers is the primary reason

for the requirement of a large energy source. Because of this large energy

requirement, the required signal-to-noise ratio to distinguish an appropriate

signal increases, thereby making this approach systemically less effective. In

addition, the Walt et al. patents disclose small beads or dyes, and thus there is

only a small amount of material to react such that the reactant signal is small.

Moreover, if optical filters are not utilized to differentiate the return signal from

the excitation signal, the signal-to-noise ratio further increases.

Another disadvantage is, because of the use of optical fibers, the sensing

device cannot be contained long term within a host body of interest. Instead,

because of the use of optical fibers, the fibers and any other needed wires and

tubes must come out of the host body to needed equipment that is located

outside the host body. For example, the light source and the external image

processing device, i.e., the detector or camera, are located at the far or remote

end of the optical fibers, outside of the host body. In this manner, the Walt et al.

patents require the optical fibers, wires, and tubes to stick out of the host body, and does not allow for a contained assembly to be inserted into a host body.

Furthermore, an additional disadvantage of the optical fibers is that there

currently is no mechanism by which one can prevent the beads from becoming

dislodged from the optical fiber end.

A method of rapid sample analysis for use in the diagnostic microbiology

field is also desirable. The techniques now used for rapid microbiology

diagnostics detect an array of various analytes ranging from antibodies,

antigens, nucleic acids, enzymes, or metabolites. The most popular of these

methods employs antigen-antibody binding. Direct assays involve rapid antigen

testing which is based upon the use of antibodies to recognize and bind to either

whole organisms, particulate, or byproducts thereof. Inherent to this approach is

the need to obtain and characterize the binding of the antibody to unique

structures (e.g., epitopes) on the organism, antigen or analyte being tested. This

process involves the introduction, identification and isolation of the appropriate

antigen-antibody binding pairs and is time consuming. Current diagnostic assays

employing these techniques are therefore limited to conducting only a handful of

diagnostic assays per testing module in order to avoid interference effects and

cross reactions. Moreover, due to the multiple reagent mixing, dispensing, and

signaling steps involved in these traditional schemes, there is limited opportunity

to conduct simultaneous analysis of multiple antigen-antibody binding events. The response time of antibody-antigen reactions in traditional diagnostic

tests of this type ranges from 10 to 120 minutes, and often involves additional

reaction preparation time, depending on the method of detection. The simplest

methods are generally agglutination reactions (e.g., blood typing), but these

methods are less sensitive and provide limited information due to difficulties in

visual interpretation of the reactions. Approaches with slower reaction times

include antigen recognition by antibody conjugated to either an enzyme or

chromosphere. These test types tend to be more sensitive, especially when

spectrophotometric methods are used to determine if an antigen-antibody

reaction has occurred.

Second, with respect to diagnostic testing with nucleic acids, one

approach uses hybridization to unique regions of the target organism. These

techniques require fewer organisms than antigen-antibody binding schemes, but

have longer response times, of up to five hours to complete. The most recent

improvement in the detection of microorganisms has been the use of nucleic acid

amplification. Nucleic acid amplification tests have been developed that

generate both qualitative and quantitative data. However, the current limitations

of these testing methods are related to delays caused by specimen preparation,

amplification, and detection. Currently, the standard assays require about five

hours to complete. The ability to complete much faster detection for a variety of microorganisms would be of tremendous value in a wide range of commercial,

medical, and safety applications.

It is therefore desirable that new sensors capable of discriminating

different analytes, toxins, metabolic by-products, and/or bacteria in cellular or

biological material or in biological exhaust products be developed for medical

diagnostic, environmental, health and safety, remote sensing, military,

food/beverage, and chemical processing applications. It is further desired that

the sensors be adaptable to the simultaneous detection of a variety of analytes

to improve throughput during various chemical and biological analytical

procedures. In the case of medical diagnostic applications, it is further desirable

that the sensors provide real-time or near real-time feedback to facilitate

appropriate diagnostic decisions.

The field of medical diagnostics is evolving rapidly, supported primarily by

the advancing technological revolution. Aided in part by innovations in the

personal electronics and computer markets, devices are constantly being

reconfigured and miniaturized and, at the same time, are capable of increasingly

intricate functions. This trend is echoed in the field of medicine as patients are

demanding similar technological amenities and subsequently raising the

accepted standard of care. Several recent innovations, such as the open

Magnetic Resonance Imaging (MRI) and "keyhole" Coronary Artery Bypass Graft (CABG), are evidence of this growing sentiment.

Testing procedures have also been altered in order to accommodate the

minimally invasive testing protocols that patients desire. Patients are no longer

tolerant of long, laborious diagnostic procedures and shy away from

unnecessary sampling or highly invasive procedures. Several emerging

technologies, such as electronic chemical/biochemical sensors (including

electronic tongues and electronic noses), are especially suited to help meet the

needs of this rapidly changing environment. Indeed, these technologies are the

epitome of avante garde in the field of medical diagnostics because this

equipment may be constructed to be compact, multi-task oriented, minimally

invasive, cost efficient, and disposable.

SUMMARY OF THE INVENTION

The present invention is directed to a method of detecting an analyte in a

fluid sample. The method includes the step of analyzing the fluid sample integral

to a region of interest with a proximally located sensor with an integral detector.

The detector may be integral with the sensor by forming the sensor and the

detector in a common structure, by attaching the detector to the sensor or

through an optical path from the sensor to the detector. The optical path is

preferably an optical fiber. The analyzing step includes the step of providing, for the sensor, a

substrate with a plurality of spatially distinct locations. A reactant is associated

with at least one of the plurality of spatially distinct locations. The fluid sample is

interacted with the reactant. A light source comprising one or more portions of

the electromagnetic spectrum is transmitted to the reactant. The detector is then

used to monitor the reactant to detect the analyte.

The present invention may include a plurality of reactants. Each reactant

may be placed at at least one of the plurality of spatially distinct locations, or

more than one reactant may be placed at at least one of the plurality of spatially

distinct locations. In the alternative, the substrate defines a plurality of cavities,

wherein at least one cavity is placed at at least one of the plurality of spatially

distinct locations. Then, each reactant is placed in at least one of the plurality of

cavities, or more than one reactant is placed in at least one of the plurality of

cavities.

The reactant is selected from the group consisting of a sensing particle, a

receptor molecule attached to a sensing particle, a gel or a reactive material.

The sensing particle is selected from the group consisting of functionalized

polymeric beads, metal oxide particles, thin polymer films, metal quantum

particles, semiconductor quantum particles, agarose, ceramic, glass, or any

combination of the foregoing. The receptor molecule is selected from the group consisting of signaling proteins, chemically sensitive dyes, nucleic acid strands,

nucleotide sequences, biological binding agents, antibodies, antigens, organic

metabolites, inorganic metabolites, functional group receptors, or any

combination of the foregoing. The substrate is comprised of glass, plastic,

silicon, resin, polymer, fiber composite, metal, metal alloy, ceramic, or any

combination of the foregoing.

In one embodiment, the reactant is a fluorescent based reactant, and the

light source is selected such that the frequency and wavelength of the light

compliments the excitation band of the selected fluorescent based reactant. In

an alternative embodiment, the reactant is a coiorimetric based reactant, and the

light source is a portion of the electromagnetic spectrum. Thus, the light source

is a white light.

The detector monitors the reactant as the fluid sample engages the

reactant. Spectroscopic changes are caused by the analyte present in the fluid

sample interacting with the reactant.

In another embodiment, the present invention is directed to a method of

analyzing a fluid sample containing one or more analytes in a biological system.

The method includes providing a physical assembly. The physical assembly

includes a sensor, a detector and an illumination source. The sensor includes a

substrate with a plurality of spatially distinct locations. A reactant is associated with at least one of the plurality of spatially distinct locations. The physical

assembly is introduced proximal to a region of interest where a fluid sample is

present. The reactant is interacted with a fluid sample. A light source

comprising a portion of the electromagnetic spectrum is transmitted to the

reactant. The detector is used to monitor the reactant to detect an analyte while

the detector is proximally located to the region where the fluid sample is present.

In a preferred embodiment, the method includes means for retrieving

optical information from within the biological system. Preferably, the means for

retrieving optical information includes a video monitor.

In a preferred embodiment, the method includes drive and interface

electronics connected to the physical assembly, which may be directly or

indirectly connected to the physical assembly. The physical assembly may be a

probe, or may be spheroidal in shape. The detector is used to monitor the

reactant as the fluid sample engages the reactant. The spectroscopic changes

are caused by the analyte present in the fluid sample interacting with the

reactant.

In another embodiment, the present invention is directed to a method of

detecting an analyte in a fluid sample within a biological system including

analyzing the fluid sample while inside the biological system with a sensor and a

detector which is integral with the sensor. The sensor and the integral detector are inserted into the biological system to be proximally located to the fluid

sample in a region of interest. The detector detects the analyte present in the

fluid sample while the detector is proximally located to the fluid sample in the

region of interest.

The biological system may be a mammalian body, such as a human, either

living or dead. In one embodiment, the sensor and the detector are integrated

with a catheter to introduce the sensor and the detector to the region of interest.

The present invention is also directed to a device for detecting an analyte

in a fluid sample integral to a region of interest. The device includes a physical

assembly. The physical assembly includes a sensor, a detector which is integral

to the sensor, and an illumination source. The sensor is comprised of a substrate

having a plurality of spatially distinct locations, at least one of the spatially distinct

locations having a reactant. The physical assembly introduces the detector

proximate to a fluid sample integral to a region of interest to allow the detector to

monitor the reactant while proximally located to the fluid sample.

The detector may be integral with the sensor by forming the sensor and

the detector in a common structure, by attaching the detector to the sensor, or

through an optical path from the sensor to the detector. Preferably, the optical

path is an optical fiber.

The device preferably includes a plurality of reactants, wherein each reactant is placed at at least one of the plurality of spatially distinct locations or

more than one reactant is placed at at least one of the plurality of spatially distinct

locations. In one embodiment, the substrate defines a plurality of cavities,

wherein at least one cavity is placed at at least one of the plurality of spatially

distinct locations. Thus, each reactant is placed in at least one of the plurality of

cavities, or more than one reactant is placed in at least one of the plurality of

cavities.

The reactant is selected from the group consisting of a sensing particle, a

receptor molecule attached to a sensing particle, a gel or a reactive material. The

sensing particle is selected from the group consisting of functionalized polymeric

beads, metal oxide particles, thin polymer films, metal quantum particles,

semiconductor quantum particles, agarose, ceramic, glass, or any combination of

the foregoing. The receptor molecule is selected from the group consisting of

signaling proteins, chemically sensitive dyes, nucleic acid strands, nucleotide

sequences, biological binding agents, antibodies, antigens, organic metabolites,

inorganic metabolites, functional group receptors, or any combination of the

foregoing. The substrate is comprised of glass, plastic, silicon, resin, polymer,

fiber composite, metal, metal alloy, ceramic, or any combination of the foregoing.

In one embodiment, the reactant is a fluorescent based reactant, and the

light source is selected such that the frequency and wavelength of the light compliments the excitation band of the selected fluorescent based reactant. In an

alternative embodiment, the reactant is a coiorimetric based reactant, and the

light source is a portion of the electromagnetic spectrum. Thus, the light source is

a white light.

In a preferred embodiment, the device includes means for retrieving optical

information from within the region of interest, which is preferably a video monitor.

The physical assembly may be a probe, or may be spheroidal in shape. In

one embodiment, the sensor and the detector are integrated with a catheter to

introduce the sensor and the detector to region of interest.

Additional objects and advantages of the invention will be set forth in part

in the description which follows, and in part will be obvious from the description,

or may be learned by practice of the invention. The objects and advantages of

the invention will be realized and attained by means of the elements and

combinations particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description and the

following detailed description are exemplary and explanatory only and are not

restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute a

part of this specification, illustrate several embodiments of the invention and

together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of one embodiment of the present invention

that analyzes a gaseous fluid sample utilizing a video pick-up assembly, and

utilizing drive and interface electronics that are indirectly connected to the

physical assembly;

Figure 2 is a perspective view of one embodiment of the present invention

that analyzes a gaseous fluid sample ufilizing a video pick-up assembly, and

utilizing drive and interface electronics that are directly connected to the physical

assembly;

Figure 3 is a perspective view of one embodiment of the present invention

that analyzes a liquid fluid sample utilizing a video pick-up assembly, and utilizing

drive and interface electronics that are indirectly connected to the physical

assembly;

Figure 4 is a perspective view of one embodiment of the present invention

that analyzes a liquid fluid sample utilizing a video pick-up assembly, and utilizing

drive and interface electronics that are directly connected to the physical

assembly;

Figure 5 is perspective view of one embodiment of the sensor of the

present invention; and

Figure 6 is a side view of the sensor shown in Figure 5, with a detector and illumination source.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred

embodiments of the invention, examples of which are illustrated in the

accompanying drawings.

The present invention is directed to method and system for analysis of a

fluid that contains one or more analytes in a system of interest. A system of

interest may include a wide variety of materials. These materials include all types

of biological systems including, but not limited to, medical, animal, environmental

and agricultural applications. Thus, the body of interest may be an animal (e.g.,

mammals, such as humans, dogs and cows, and other animals such as fish) or a

plant (e.g., plants, trees, shrubs and the like). In addition, the body of interest

could be a living or deceased animal or plant, and thus includes, but not limited

to, living or deceased animals, mammals, humans, plants, trees and the like. The

body of interest could also be a food product, or the wash of a food product.

The present invention may be used for either gaseous fluids or liquid fluids.

Thus, the present invention may utilize either "electronic nose" or "electronic

tongue" technology, as well as combining features of both technologies. With

respect to sampling gas samples, the present invention may utilize any type of electronic nose sensor, including, but not limited to, conductivity sensors,

piezoelectric sensors, metal oxide silicon field effect transistor (MOSFET) sensing

devices, optical sensors and spectrometry-based sensing methods. In addition,

with respect to sampling liquid samples, the present invention may utilize any type

of electronic tongue sensor, including, but not limited to, those based on "DNA on

a chip" technology; those based on thin films, dyes or beads that act as receptor

units; probe arrays; conducting polymer gas sensors; acoustic wave gas sensors;

field-effect gas sensors; electrochemical gas sensors; pellistors; fiber optic gas

sensors; discotic liquid crystals; and pulse spectroscopy cells. Again, the present

invention is configured to allow one to combine a type of electronic tongue sensor

with a type of an electronic nose sensor to allow one to sample both liquids and

gases simultaneously.

Depending on the type of sensor utilized, the detector includes, but is not

limited to, optical detectors, such as, for example, complementary metal oxide

semiconductor (CMOS) detectors, photovoltaic cells, amorphous silicon photo¬

sensor on glass (e.g., photodiode or TFT based), Organic Light Emitting Diode

(OLED) detectors, infrared detectors, fluorescent detectors, ultraviolet detectors

or charge coupled device (CCD) detectors.

The device of the present invention is suitably configured such that the

detector is integral with the sensor in a common structure. In this manner, the actual detection of analytes takes place while the sensor and detector are

proximally located to the fluid sample, when the fluid sample is integral with its

system or body of interest. There are a variety of manners in which the sensor

and detector may be integral with each other. For example, the sensor and

detector may be formed in a common structure, such as, for example, in the same

mold or die. In addition, the detector may be attached to the sensor through any

number of attachment mechanisms, including, but not limited to, the use of

adhesives or fastening devices. Also, the detector may be situated near the

sensor, but not be part of the same mold of the sensor nor be attached to the

sensor. In this situation, an optical light path from the sensor could be transmitted

to the detector from the sensor through a variety of mechanisms, including, but

not limited to, an optical fiber. In one embodiment, the detector is situated below

the sensor such that light from the sensor is transmitted to the detector.

The method and system of the present invention includes a sensor which

is preferably comprised of a substrate having a plurality of spatially distinct

locations, at least one of the spatially distinct locations having a reactant. The

substrate is any material capable of having a reactant incorporated therewith.

There are a variety of manners in which the reactant may be incorporated with

the substrate. In one embodiment, the reactant is attached to the substrate. In

another embodiment, the reactant is intercalated within the substrate. Preferably, there is a plurality of reactants, each reactant being placed at one of the spafially

distinct locafions. In the alternative, more than one reactant may be placed at

one of the plurality of spatially distinct locations. In a preferred embodiment, the

substrate defines a plurality of cavities, with at least one cavity being positioned at

at least one of the spatially distinct locations. Thus, in this embodiment, one

reactant may be placed in at least one of the cavities or, in the alternative, more

than one reactant may be placed in one of the cavities. The spatially distinct

locations are comprised of locations spaced apart from one another on the

substrate. These locations may be in an ordered array or may be unordered.

The reactant is any material capable of interacting with an analyte that

experiences changes that are detectable and that are indicative of the analyte

present. The reactant may be a sensing particle, a receptor molecule attached to

a sensing particle, a gel, or a reactive coating.

The method of analyzing a fluid sample for an analyte of interest includes

having a sensor preferably comprised of a substrate having a plurality of spatially

distinct locations, wherein a reactant is associated with at least one of the plurality

of spatially distinct locations. To detect the analyte, the fluid sample is interacted

with the reactant, and a light source comprising a portion of the electromagnetic

spectrum is transmitted to the reactant. Because of the interaction between the

analyte and the reactant, the reactant will absorb electromagnetic radiation at one or more frequencies. The detector is used to monitor the reactant to sense

changes in absorbed electromagnetic radiation, and thus spectroscopically detect

the analyte.

Uses of the Present Invention

The present invention may be utilized in a wide variety of applications to

perform localized assays in specific regions of interest. In particular, the present

invention is configured to be able to be placed in the specific region of interest,

and is able to perform detection of analytes in a sample at the region of interest

while proximally spaced in the region of interest.

For human and animal applications, the present invention may be utilized

to determine a variety of local biochemical or chemical conditions that can be

used to indicate or diagnose specific local or systemic disorders or states. For

example, the present invention may be used to isolate the presence of specific

biochemical "markers," such as cardiac or tumor markers, contained with

biological serum or at a tissue junction. As such, it may prove useful in

researching causal or predictive links between specific markers and known health

states, such as unstable angina. As another example, the present invention may

also prove useful for discriminating between different internal deposits, such as,

for example, lipid laden plaque versus other plaques inside cardiac arterial walls, thereby providing clinicians with diagnostic data that can help determine patient

health states.

The present invention will be capable of performing a multitude of varying

forms of analyses and is particularly well suited for minimally invasive diagnostics

protocols requiring real-time site-directed feedback data. Unlike existing

diagnostic equipment, the present invention requires minimal sample volume and

processing, and thus is able to operate in what previously were inaccessible or

inoperable mediums. Miniaturized platform size and a high degree of integration

allow placement of the system into several existing medical applications. A

variety of minimally invasive diagnostic protocols involving catheter placement

exist currently that allow real-time monitoring of parameters, such as, for

example, intra-arterial pressures and pH. However, no technology currently

exists that allows an extensive panel of real-time analysis to be conducted

concurrent with minimally invasive procedures.

There are three main areas where the present invention would provide

great improvement in current medical diagnostic capabilities. The first involves

continuous monitoring of critical care (ICU) patients. These patients, generally

suffering in some aspect from a deregulation of homeostasis, often need to have

simple blood chemistries, such as, for example, electrolytes and blood gases,

drawn on a rigorous hourly basis. For example, the treatment for a patient admitted in Diabetic Keto-Acidosis consists almost entirely of correcting fluid

electrolytes while stabilizing blood glucose levels. This is often an arduous task

that, in some circumstances, amounts to "chasing your tail" as corrections in

treatment are dependent upon the results of the hourly blood draws. The present

invention would provide one the ability to monitor, in real-time, electrolytes, blood

glucose, ketones and blood gas parameters, and thus would enable the physician

to more efficiently tailor the patient's regimen. Optionally, this could be

accomplished through the integration of the chemical/biochemical sensor into a

typical catheter that is used to provide central venous access for hydration.

Several other examples exist in which real-time monitoring would provide a

distinct advantage in the acute care setting. Poly-trauma patients, often afflicted

with similar hemostatic challenges, could also benefit greatly from such diagnostic

integration. Moreover, patients admitted for suspected bacterial sepsis could be

monitored for the development of complications such as Disseminated

Intravascular Coagulopathy (DIC), a commonly fatal state. In this situation, the

present invention could monitor parameters associated with developing a

Coagulopathy, such as fibrinogen and fibrin split products, could simultaneously

help characterize the offending bacterial agent, and thus help determine the

appropriate anti-microbial therapy.

The second area in which the present invention would provide great improvement in current medical diagnostic capabilities is with its integration with

new generation endoscopic and laparoscopic technologies. There are many new

technologies, both therapeutic and diagnostic, that involve minimally invasive

procedures. On a daily basis, endoscopes are utilized in the field of medicine to

survey a variety of things such as, for example, gastric ulcers, tumors, colon

polyps, and tissue abnormalities. However, little information other than visual

cues is provided to the physician to make their clinical assessment. Quite often,

the physician is put in the position of taking a conservative approach and either

removing or taking a biopsy of a potential malignant or atypical appearing entity.

Many of these procedures, as is learned from subsequent pathology reports, are

unnecessary and could have been avoided had the proper information been

provided. For example, if a physician performing an endoscopic procedure to

survey a patient's gastric ulcer was able to detect the presence of the bacteria

Helicobacter pylori, he or she may be able to avoid an unnecessary biopsy for

possible malignancy by detecting this ulcer causing bacteria.

Similar guidance of therapeutic decisions could be provided in a concurrent

fashion in the use of bronchoscopy. Frequently, bronchoscopy is utilized to

sample inaccessible fluids or organisms present in the lungs. By using the

present invention, a physician would be able to both visualize an area of interest

and simultaneously sample the local environment looking for specific bacterial metabolites or fluid characterization.

Comparable uses for this technology may also be seen in the use of

colonoscopy. Colonoscopy is characteristically used to survey anatomical

aberrations such as, for example, neoplasms and polyps and local area of

inflammation in the intestinal tract. Through the incorporation of tumor marker

agents such as carcino-embryonic antigen (CEA) for colon cancer and local

cytokines for indicators of specific inflammatory diseases such as, for example,

Crohns or Ulcerative Colitis, the clinician may be able to enhance his or her

diagnostic ability and survey more intensely for specific etiologic agents of

disease.

The third area in which the present invention would provide great

improvement in current medical diagnostics is in surgical intervention and

bioengineering. The field of surgery, predicated upon its distinct ability to be

invasive yet beneficial, has perhaps made the greatest leap to the realm of

minimally invasive diagnostic and therapeutic techniques. With the advent of the

laparoscope and the accompanying surgical tools, surgeons are now able to

perform a majority of their procedures through minute incisions. Although this is

obviously a desirable shift for the patient, it has provided a technical challenge

and has limited, in some aspects, the surgeon's ability to completely visualize the

procedure. Intricate fiberoptic laparoscope with illumination sources linked to viewing

monitors are commonplace in every operating room. However, there are still

inaccessible regions that were previously accessible in the more open invasive

approaches. The present invention could provide information regarding the

viability of tissues by sensing necrosis, thrombosis, decreased perfusion, and

local inflammation and local tissue metabolites. With this information, a surgeon

would be able to custom tailor his or her procedure around specific biochemical

thresholds indicative of disease or anatomical aberration.

For example, a patient undergoing an aortic arch vascular repair often has

blood flow diverted from organs such as his or her kidney and colon. Continuous

monitoring of local metabolites indicative of stress such as, for example, lactic

acid or cellular breakdown components, would provide the surgeon with specific

information regarding the viability of bypassed organs. In the case of open heart

surgery, a real-time intra-cardiac monitoring of enzymes associated with

myocardial infarction, such as, for example, CK-MB, would help eliminate "silent

heart attacks" that occur during such procedures. This type of technology would

not only give the added advantage of providing real-time data feedback but would

also allow specific localized surveys of anatomical regions to be conducted, and

thus serve as an extension of the surgeon's diagnostic acumen.

In addition to medicine, the present invention may be utilized in food safety applications. In particular, the present invention could be utilized to detect

pesticides, hormones, toxins, antibiotics, bacterial contamination, and levels of

lipid, sugar and oil. Recently, studies have shown an alarming incident of

pesticides and hormones in produce purchased in supermarkets. Following up

on a 1993 National Academy of Sciences study critiquing federal pesticides

standards relating to protection of infants, the Environmental Working Group

(EWG) commissioned laboratory tests of baby food made by industry leaders. It

found 16 pesticides, including three carcinogens, five 'possible' carcinogens, eight

neurotoxins, five endocrine disruptors, and five 'toxicity one' chemicals.

Because of the widespread industry of use of recombinant bovine growth

hormone (rBGH) to boost milk production, most dairy cows suffer from clinical

mastitis, a common infection of the udder. The antibiotics used to treat these

cows often finds its way into our milk. The present invention may be used to

sample a wash from fruits, grains or other produce, or to directly sample a

solution made from these. Alternatively, the present invention may be used to

test liquid food products, such as milk, for example, to monitor for pesticides,

bacterial presence, hormones, antibiotics, rodent feces, or specific fungal toxins,

such as afaltoxin. Still further, the present invention may be used in ruminant

protein screening, for example, to screen for bovine albumin and ovine albumin,

which could help document compliance to prevent Bovine Spongiform Encephalopathy (BSE), also known as "mad cow" disease, as well as to detect

other residues.

There is also growing concern regarding the accelerating use of genetically

modified crops and their purity. There is evidence that in certain cases

genetically modified crops actually concentrate toxins, or in some cases, express

proteins whose metabolic breakdown products are toxic to the person or animal

that consumes the crop. The present invention could be used to monitor for

specific toxins, proteins, and even for specifically coded DNA sequences to

ensure crop safety.

Food safety is an ever present concern in meat processing operations as

well. Bacterial contamination is a significant health risk that is often caught after

meat processing and distribution has already occurred. Because of its unique

capability to detect specific bacteria, the present invention could innovate the

meat processing industry by providing immediate feedback regarding the

presence of specific bacterial contamination, either directly at the surface of the

meat or in meat wash products. As well, the present invention could be used to

monitor for a wide range of residues, including, but not limited to, toxins,

pesticides, hormones, antibiotics, specific fungal toxins (such as aflatoxin), and

the like.

Food grading is another area where the present invention would be of use. This system can be used in meats to detect lipid levels and other factors that

correlate directly with "eatability." In crops, the same techniques can be used to

detect factors such as, for example, specific oil and sugar levels.

Embodiments of the Present Invention

The present invention is able to detect both an individual analyte and

mixtures of analytes. Preferably, the present invention includes a plurality of

reactants that may simultaneously detect many kinds of analytes rapidly. In

addition, the present invention may be either reusable, assuming the reactants

can be returned to their original state after use, or replaceable, if the relevant

chemistry is not reversible or if dictated by reasons of hygiene or other issues of

convenience and/or expense.

Figures 1 and 2 illustrate embodiments of a system of the present

invention for detecting analytes in an air fluid sample. Such a system can be

used to detect gas-born analytes, including, but not limited to, metabolic

byproducts in bodily structures such as the esophagus, the gastrointestinal tract

or the abdominal cavity.

As shown in Figures 1 and 2, the system 100 includes a sensor structure

101 , a physical assembly 102 for proximally placing the sensor in a region of

interest, and drive and interface electronics 103. The drive and interface WO 00/68670 PCT/USOO/l 2409

electronics may be connected either indirectly (Figure 1) or directly (Figure 2) to

the physical assembly 102. In a preferred embodiment, the system 100 includes

video pick-up assembly 104. Figures 3 and 4 illustrate embodiments of a

system 110 of the present invention for detecting analytes in a liquid fluid sample.

Such a system may be ufilized to detect liquid-born analytes, including, but not

limited to, detecting cardiac or tumor markers within biological serum; detecting

different types of plaque within cardiac arterial walls; detecting electrolytes,

ketones, blood glucose, and blood gas parameters in blood samples; detecting

bacteria in a sample, such as a fluid sample in a gastric ulcer or lungs; detecting

bacteria, pesticides, hormones, antibiotic and the like in wash from fruits, grains,

or other products, or from liquid food products, such as, for example, milk, juices,

canned soups and breakfast drinks; for environmental monitoring, including

testing runoff water, ponds, lakes, rivers, wells, mining operations and testing

toxins on a farm, in both soil and water; and for monitoring plants.

As shown in Figures 3 and 4, the system 110 includes a sensor structure

111 , a detector 112, an illuminafion source 113, a physical assembly 114 for

proximally placing the sensor in a region of interest, and drive and interface

electronics 115. The sensor 111 , the detector 112 and the illumination source

113 are all connected to the physical assembly 114 in some fashion. For

example, either the sensor 111 , the detector 112 and/or the illumination source 113 may be formed in a common structure with the physical assembly 114, such

as, for example, in the same mold or die. In addition, either the sensor 111 , the

detector 112 and/or the illumination source 113 may be attached to the physical

assembly 114 through any number of attachment mechanisms, including, but not

limited to, the use of adhesives or fastening devices.

The drive and interface electronics 115 are connected either indirectly

(Figure 3) or directly (Figure 4) to the physical assembly 114. In this embodiment,

the detector 112 is positioned below the sensor structure 111 to allow for data

acquisition. In a preferred embodiment, the system 110 includes video pick-up

assembly 117. In another preferred embodiment, for fluorescent measurements,

the system 110 includes a filter assembly 116 that removes the excitation

wavelength.

Although any number of types of sensors may be utilized for the sampling

of the fluid of interest, a preferred sensor structure is based on utilizing a sensor

including at least one reactant. In particular, after the reactant interacts with the

analyte of interest in the fluid sample, the reactant experiences spectroscopic

changes that may be detected using a suitable detector. This preferred sensor

structure is discussed in detail in the following U.S. Applications for Patent: Ser.

Nos. 60/093,111 , 09/354,882, 60/144,436, 60/144,435, 60/144,126 and

PCT/US99/16162, all filed on 16 July 1999; Ser. No. 09/287,248 filed 7 April 1999; Ser. Nos. 60/179,369, 60/179,424, 60/179,294, 60/179,380, 60/179,380,

60/179,292 and 60/179,293, all filed on 31 January 2000; the foregoing all owned

by the University of Texas and subject to license by Applicants; and Ser. No.

60/133,230, filed 7 May 1999, jointly owned by Applicants and the University of

Texas, each of which is herein incorporated by reference in its entirely.

In one embodiment, the reactant is a plurality of chemically sensitive

structures that produce a detectable signal in the presence of an analyte.

Preferably, the reactants produce coiorimetric or fluorescence signals upon

exposure to an analyte. In a preferred embodiment, the sensor structure includes

an array of such reactants.

Examples of the reactants include, but are not limited to, functionalized

polymeric beads (e.g., polystyrene-polyethylene-giycol (PS-PEG) resin beads),

gels, metal oxides particles (e.g., silicon dioxide [SiO₂] or aluminum oxides

[AI₂O₃]), thin polymer films, metal quantum particles (e.g., silver, gold, platinum,

etc.), semiconductor quantum particles (e.g., Si, Ge, GaAs, etc.), agarose,

ceramics, glass, or any combination of the foregoing. The particular reactant

selected is dependent on its specific wettability characteristics, porosity, and

reflectivity. In this manner, the reactant selected will be ideally suited to detect

the particular analyte desired to be detected.

In one embodiment, the reactant is a sensing particle, such as, for example, PS-PEG resin beads. The choice of a PS-PEG matrix is based on its

wettability by aqueous solutions and the availability of well developed literature

methods for its derivatization as described in the experimental section.

In one embodiment, the reactant is a receptor molecule synthesized,

adsorbed onto, attached to, or intercalated into a sensing particle. The particular

receptor molecule chosen depends on which analyte one wants to detect.

Examples of chemically active receptor molecules that may be formed on the

surface of the sensing particle include a wide variety of molecules, including, but

not limited to, signaling proteins (e.g., antigens, antibodies, and enzymes),

chemically sensitive dyes, nucleic acid strands, nucleotide sequences, biological

binding agents (e.g., avidin/biotin, lectins, and chelators), organic/inorganic

metabolites, and functional group receptors.

In one embodiment, the sensing particles have diameters in the range of 1

- 500 microns and may actually change size (e.g., swell or shrink) when exposed

to analytes in the fluid sample. For example, a fluid sample that includes a large

amount of lipid material may cause non-polar particles to change in volume when

the particles are exposed to such a fluid.

As discussed above, the sensor includes a substrate having a plurality of

spatially distinct locations, with at least one of the plurality of spatially distinct

locations having a reactant. In one embodiment, as shown in Figures 5 and 6, the substrate is a support member 120 configured to include the reactants. The

support member 120 is preferably used to localize the reactants, as well as to

serve as a microenvironment in which chemical assays may be performed. The

support member 120 is preferably made of any material capable of supporting the

reactants, while allowing the passage of the appropriate wavelength of light.

Preferably, the support member 120 is also made of a material substantially

impervious to the fluid sample of interest. The support member 120 may be

made of a variety of materials, including, but not limited to, silicon, plastics, glass,

metals, resins, polymers, fiber composites, metals, metal alloys, ceramics or any

combination of the foregoing.

As shown in Figures 5 and 6, the support member 120 preferably includes

a plurality of cavities 130. In one embodiment, the cavities 130 are formed such

that at least one particle 124 is substantially contained within a cavity 130. In an

alternative embodiment, a plurality of particles are contained within a single cavity

(not shown). A detailed description of the formation of cavities in a support

member is discussed, for example, in U.S. Application Serial Nos. 90/287,248,

filed April 7, 1999; 60/144,436, filed July 16, 1999; and 60/179,369, field January

31 , 2000; each of which is subject to joint license by Applicants, and are herein

incorporated by reference thereto.

As stated above, in addition to the sensor structure 111 , the system 110 includes a detector 112 and an illumination source 113. As shown in Figure 5,

light comprising a portion of the electromagnetic spectrum, which originates from

the illumination source 113, preferably passes through the sensor structure or

array 111 and is modulated by the reactants of the sensor structure, before

impinging on the proximally spaced detector 112. For fluorescent based systems,

the light source 113 is a wavelength tailored and preferably filtered source, such

as a light emitting diode (LED), whose frequency and wavelength output is

chosen to compliment the excitation band of the chosen sensing fluorophore

particle. For example, in one embodiment, a high intensity blue LED is

appropriate complement to fluorescein. For coiorimetric (e.g., absorbance) based

systems, the light source 113 is preferably a "white" light. In one embodiment,

the light is delivered proximate to the sensor through a fiber optic assembly (not

shown).

Monitoring the spectroscopic changes to the reactants is preferably

accomplished by use of the detector 112 itself and may be assisted by a

microprocessor (such as microprocessor 140 shown in Figure 6) (or other optical

or electronic processing system components) coupled, directly or indirectly, to the

detector 112.

The detector 112 measures changes in the optical characteristics which

occur upon the interaction of the reactants with the analytes. A wide range of optical detectors, including, but not limited to, charged coupled detectors (CCD),

ultraviolet detectors or fluorescent detectors, may be used. For fluorescence

measurements, as shown in Figure 6, a band limiting or band pass optical filter

116 may be placed between the support member and detector 112 to remove the

excitation wavelength.

The system 110 of the present invention includes a sensor structure 111

with an integral detector 112 to allow the detection of any analyte to occur within

the region of interest. The physical assembly 114 is used to place the sensor

structure 111 and the detector 112 within the region of interest. In human or

animal applications, to place the sensor structure 111 and the detector 112 in the

region of interest, the physical assembly 114 is configured to be inserted through

an opening in the biological system, such as, for example, an existing orifice or

incision, to locate the physical assembly 114 (with sensor and detector) proximate

to the region of interest. In one embodiment, the sensor structure 111 and the

detector 112 are integrated into a typical catheter that is used to provide central

venous access for hydration.

Because the present invention may be used in in vivo or in vitro

applications, there are engineering constraints that must be observed in order to

make the present invention compatible with the body. In particular, the physical

assembly 114 must be of a shape and size that permits it to be delivered proximate to the region of interest with minimal invasive effects, typically requiring

the overall diameter to be 15 mm or less. In addition, the physical assembly 114

should be smooth, must be constructed of bio-compatible materials, and must

operate at safe energy levels and temperatures. In one embodiment, the physical

assembly 114 has the shape of a probe. In another embodiment, the physical

assembly 114 is spheroidal in shape.

In addition to the sensor structure 111 , detector 112, illumination source

113, and the physical assembly 114, the system 110 includes drive and interface

electronics 115. In one embodiment, as shown in Figure 3, the drive and

interface electronics 115 are indirectly connected to the physical assembly 114.

The indirect connection of the drive and interface electronics 115 with the

physical assembly may include, but is not limited to, utilizing wires. One of skill in

the art can also readily recognize that alternative indirection connections include,

but are not limited to, utilizing induction methods, such as using radio waves,

microwaves, or infrared sensing. In an alternative embodiment, as shown in

Figure 4, the drive and interface electronics 115 are directly connected to the

physical assembly 114. In one embodiment, the drive and interface electronics

115 are attached to one end of the physical assembly 114.

The drive and interface electronics 115 include, but are not limited to, well

known electrical components such as, for example, a microprocessor to acquire data and to manipulate the data, memory chips to store the data, timing circuitry,

calibration circuitry, communication interface circuitry, provisions to handle

applicable device triggering and the like. These types of electrical components

are well known in the electrical arts, and a detailed discussion of each is beyond

the scope of this invention.

In a preferred embodiment, the present invention includes means for

retrieving optical information from within the body of interest. In particular, the

present invention preferably includes optical video technology that acquires and

permits the display of imagery from within the body of interest that can be used to

visualize and inspect the areas of interest, as well as performing localized

chemical/biochemical assays. In particular, as shown in Figures 1 through 4,

video pick-up assembly 104 or 117 allows one to view the area where the

physical assembly 102 or 114 is being positioned. The video pick-up assembly

104 or 117 is preferably a video monitoring system to allow one to view the region

of interest as the physical assembly 102 or 114 is being inserted to the region of

interest.

Optical Systems

Presently, optical sensors may be based upon coiorimetric or fluorescent

based systems. For either system, the sensor is generally made up of reactants which experience spectroscopic changes after interacting with an analyte of

interest. In addition, for either system, a detector is utilized to detect the

spectroscopic changes experienced by the reactants.

Coiorimetric Based Systems

Evaluation of the changes in optical properties of the various reactants in a

coiorimetric based system may be accomplished in the following fashion. Light is

delivered to the sensor structure and the detector records the coiorimetric

changes in the light that passes through the reactants. A commercial-grade 24-

bit (8 bit x 3 color planes) video camera (not shown) is preferably used to detect

the reactant changes, providing the ability to acquire images at a rate of

approximately 30 times per second. This speed is valuable in the initial kinetic

characterization of reactants, such as, for example, micro-sphere sensors.

Although not discussed at length here, evaluation of the transient data could

provide an additional means to identify the chemical composition of these

samples. It should be emphasized that the rapid acquisition of time dependent

coiorimetric data provides a particularly powerful analytical capacity when these

capabilities are combined with modem pattern recognition algorithms.

For coiorimetric based systems, the spectral information is acquired from

the detector in a format where the white light has been simplified, for instance, by assigning relative intensity values to three key wavelength regions, namely red-

green-blue (RGB). This interpretation has been adopted from standard color

wheel analysis protocols and represents one Commission Internationale de

L'Eclairage (CIE) standard color space that can be used for coiorimetric

processing. The linear intensity levels recorded with the detector are normalized

against an averaged background light level transmitted through particles which

are underivatized. The level of the averaged background light level through

underivatized particles is taken as 100% transmittance. In a reactant particle-

based system, it should be noted, however, that transmission intensities recorded

through a particle are typically 20% less than those obtained in the absence of

the particle, as expected since unavoidable light scattering occurs. For this

reason, underivatized particles in the cavities are used as reference cells instead

of empty cavities.

Absorptance (A_{R G,B}) values reported for each of the three RGB hues are

determined from the following equation:

where T_{R G B} is defined at the transmitted intensity through a particle in a particular

environment for each of the selected hues, and T₀ is the average background

intensity through the underivatized particles. The coherent appearance of color through the center of the particle indicates that the analyte is incorporated

uniformly throughout the particle. Collectively, these results demonstrate that

aqueous analytes can penetrate into the polymer particles, that the particles are

suitable media for optical measurements, and that the detector can be used to

quantify the coiorimetric changes. Other systems may be used wherein the light

source and the sensor operating frequency and wavelength include the receptor

activation range. The term "receptor activation range" is thus understood herein

to refer to that portion of the electromagnetic spectrum in which the receptor

absorbs or interacts with electromagnetic radiation.

Fluorescent Based Systems

Fluorescent based diagnostic assays operate under the same general

principles, although they differ in the optical excitation and signal output

methodology. In a particle-based reactant system, the actual receptor molecule

design and attachment to the sensing particle is identical to coiorimetric

techniques. In the fluorescent mode, the reactant emits a fluorescent rather than

a coiorimetric signal. This is accomplished through the conjugation of chemically

sensitive fluorophores to both the particle substrate and the custom designed

receptor compounds. These fluorophores, responding to local binding events in

and around the particle, emit a unique fluorescent signature. However, this requires excitation via a specific wavelength of light, either through the use of

optical filters or specifically tuned excitation sources such as light emitting diodes

(LED). In particular instances, fluorescent signaling schemes are employed to

amplify signal output from otherwise indetectable analytes. Signal detection is

still accomplished using an optical detector such as, for example, a CCD detector.

This information is then processed and both qualitative and quantitative values

are achieved using correlations with the intensity of the specific wavelength of

light emitted from the reactants. In this scenario, signal analysis is simplified due

in part to the narrow spectral signal input.

Example of Optical Detection Based on o-cresolphthalein

Complexone Derivatized Micro-spheres Utilizing Coiorimetric Based

System

The following is an illustrative example showing how a particle reactant can

acquire information related to the local chemistry of fluids based on a coiorimetric

based system. The information is obtained from optical photomicrographs that

were taken of o-cresolphthalein complexone derivatized particles or micro-

spheres. Upon the exposure of the particles to aqueous solutions containing no

Ca⁺² and 0.1 M Ca⁺², these micro-spheres change color in a dramatic manner.

Indeed, the micro-spheres are virtually transparent across the entire visible region

when no Ca⁺² is present in the solution. In contrast, the same micro-sphere

exposed to 0.1 M Ca⁺² displays a markedly different physical appearance as indicated by purple hue. The UV-vis absorbance spectrum reveals the absorption

band is centered at = 550 nm which approximately matches the solution

absorbance spectrum of o-cresolphthalein complexone responding to Ca⁺².

The sensor structure of the electronic tongue sensor as described herein

has the capacity to simultaneously analyze the chemical composition of complex

mixtures of analytes. In particular, the composite changes to different analytes

were analyzed for four different environments including no analyte, 0.1 M Ca⁺²,

0.1 M Ce⁺³, a mixture of 0.1 M Ca⁺² and 0.1 M Ce⁺³ for four different micro-

spheres. The four different micro-spheres were tagged with: (1) underivatized, (2)

o-cresolphthalein complexone, (3) alizarin complexone, and (4) fluorescein. For

each of the environments on each of the sensors, five representative pH's

(3,5,7,9, and 11), all buffered by a mixture of 0.04 M phosphate, 0.04 M acetate,

and 0.04 M borate, were evaluated.

Quantification of coiorimetric changes using the RGB analysis were

compiled for each of four chemically functionalized micro-spheres. This protocol

conforms to the capabilities afforded by commercially available CCD-based

detectors. With the use of the CCD detector, three channels of data are available

for each micro-sphere as a function of time. In fact, since the micro-sphere is

significantly larger than the associated CCD pixels, redundant information is

available allowing for a signal averaging to be made for each micro-sphere. For the underivatized micro-sphere, little light attenuation is observed for

all of the studied cases. A small deviation in the signals recorded for this micro-

sphere suggests minor alterations in the light scattering changes in the

absorbance properties or differences in the alignment occurred. In any event, the

differences are relatively small when compared to the other micro-sphere

structures. In fact, each type of micro-sphere displays spectral features and

chemical selectivity vastly different from the other ones. For example, the o-

cresolphthalien micro-spheres display significant color attenuation only in the two

cases at pH = 11 with Ca⁺² alone and Ca⁺²/Ce⁺³ mixtures. In particular, in these

situations, most significant attenuation occurs in green wavelengths, along with

modest color attenuation in red wavelengths. In all other chemical environments,

the color attenuation is less significant.

Other embodiments of the invention will be apparent to those skilled in the

art from consideration of the specification and practice of the invention disclosed

herein. It is intended that the specification and examples be considered as

exemplary only, with a true scope and spirit of the invention being indicated by

the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of detecting an analyte in a fluid sample comprising the

step of analyzing the fluid sample integral to a region of interest with a proximally

located sensor with an integral detector.

2. The method of claim 1 wherein the detector is integral with the

sensor by forming the sensor and the detector in a common structure.

3. The method of claim 1 wherein the detector is integral with the

sensor by attaching the detector to the sensor.

4. The method of claim 1 wherein the detector is integral with the

sensor through an optical path from the sensor to the detector.

5. The method of claim 4 wherein the optical path comprises an optical

fiber.

6. The method of claim 1 wherein the analyzing step comprises the

steps of: providing, for the sensor, a substrate with a plurality of

spatially distinct locations, at least one of the plurality of spatially distinct locations

having a reactant;

interacting the fluid sample with the reactant,

transmitting a light source comprising one or more portions of the

electromagnetic spectrum to the reactant, and

monitoring the reactant to detect the analyte.

7. The method of claim 6 further comprising the step of providing a

plurality of reactants, wherein each reactant is placed at at least one of the

plurality of spatially distinct locations.

8. The method of claim 6 further comprising the step of providing a

plurality of reactants, wherein more than one reactant is placed at at least one of

the plurality of spatially distinct locafions.

9. The method of claim 6 wherein the substrate defines a plurality of

cavities, wherein at least one cavity is placed at at least one of the plurality of

spatially distinct locations.

10. The method of claim 9 further comprising a plurality of reactants,

wherein each reactant is placed in at least one of the plurality of cavities.

11. The method of claim 9 further comprising providing a plurality of

reactants, wherein more than one reactant is placed in at least one of the plurality

of cavities.

12. The method of claim 6 wherein the reactant is selected from the

group consisting of a sensing particle, a receptor molecule attached to a sensing

particle, a gel or a reactive material.

13. The method of claim 12 wherein the sensing particle is selected

from the group consisting of functionalized polymeric beads, metal oxide particles,

thin polymer films, metal quantum particles, semiconductor quantum particles, agarose, ceramic, glass, or any combination of the foregoing.

14. The method of claim 12 wherein the receptor molecule is selected

from the group consisting of signaling proteins, chemically sensitive dyes, nucleic

acid strands, nucleotide sequences, biological binding agents, antibodies,

antigens, organic metabolites, inorganic metabolites, functional group receptors,

or any combination of the foregoing.

15. The method of claim 6 wherein the substrate is comprised of glass,

plastic, silicon, resin, polymer, fiber composite, metal, metal alloy, ceramic, or any

combination of the foregoing.

16. The method of claim 6 wherein the reactant is a fluorescent based

reactant, and the light source is selected such that the frequency and wavelength

of the light compliments the excitation band of the selected fluorescent based

reactant.

17. The method of claim 6 wherein the reactant is a coiorimetric based

reactant, and the light source is a portion of the electromagnetic spectrum.

18. The method of claim 17 wherein the light source is a white light.

19. The method of claim 6 wherein the step of monitoring the reactant

comprises monitoring the spectroscopic changes of the reactant by the detector

as the fluid sample engages the reactant, wherein the spectroscopic changes are

caused by the analyte present in the fluid sample interacting with the reactant.

20. A method of analyzing a fluid sample containing one or more

analytes in a biological system comprising the steps of:

providing a physical assembly, the physical assembly including a

sensor, a detector and an illumination source, the sensor including a substrate

with a plurality of spatially distinct locations, at least one of the plurality of spatially

distinct locations having a reactant;

introducing the physical assembly proximal to a region of interest

where a fluid sample is present;

interacting a fluid sample with the reactant;

transmitting a light source comprising a portion of the

electromagnetic spectrum to the reactant; and

monitoring, utilizing the detector, the reactant to detect an analyte

while the detector is proximally located to the region where the fluid sample is

present.

21. The method of claim 20 further comprising the step of providing

means for retrieving optical information from within the biological system.

22. The method of claim 21 wherein the means for retrieving optical

information comprises a video monitor.

23. The method of claim 20 further comprising the step of providing

drive and interface electronics connected to the physical assembly.

24. The method of claim 23 wherein the drive and interface electronics

are directly connected to the physical assembly.

25. The method of claim 23 wherein the drive and interface electronics

are indirectly connected to the physical assembly.

26. The method of claim 20 wherein said physical assembly is a probe.

27. The method of claim 20 wherein said physical assembly is

spheroidal in shape.

28. The method of claim 20 wherein the step of monitoring the reactant

comprises monitoring the spectroscopic changes of the reactant by the detector

as the fluid sample engages the reactant, wherein the spectroscopic changes are

caused by the analyte present in the fluid sample interacting with the reactant.

29. A method of detecting an analyte in a fluid sample within a

biological system comprising the step of analyzing the fluid sample while inside

the biological system with a sensor and a detector which is integral with the

sensor, wherein the sensor and the integral detector are inserted into the

biological system to be proximally located to the fluid sample in a region of

interest, and the detector detects the analyte present in the fluid sample while the

detector is proximally located to the fluid sample in the region of interest.

30. The method of claim 29 wherein the biological system is a mammalian body, such as a human, either living or dead.

31. The method of claim 30 wherein the sensor and the detector are

integrated with a catheter to introduce the sensor and the detector to the region of

interest.

32. The method of claim 31 wherein the biological system is a

mammalian body, such as a human, either living or dead.

33. A device for detecting an analyte in a fluid sample integral to a

region of interest comprising:

a physical assembly, the physical assembly including a sensor, a

detector which is integral to the sensor, and an illumination source; and

the sensor comprised of a substrate having a plurality of spatially

distinct locations, at least one of the spatially distinct locations having a reactant;

wherein the physical assembly introduces the detector proximate to

a fluid sample integral to a region of interest to allow the detector to monitor the

reactant while proximally located to the fluid sample.

34. The device of claim 33 wherein the detector is integral with the

sensor by forming the sensor and the detector in a common structure.

35. The device of claim 33 wherein the detector is integral with the

sensor by attaching the detector to the sensor.

36. The device of claim 33 wherein the detector is integral with the sensor through an optical path from the sensor to the detector.

37. The device of claim 36 wherein the optical path comprises an optical

fiber.

38. The device of claim 33 further comprising a plurality of reactants,

wherein each reactant is placed at at least one of the plurality of spatially distinct

locations.

39. The device of claim 33 further comprising a plurality of reactants,

wherein more than one reactant is placed at at least one of the plurality of

spatially distinct locations.

40. The device of claim 33 wherein the substrate defines a plurality of

cavities, wherein at least one cavity is placed at at least one of the plurality of

spatially distinct locations.

41. The device of claim 40 further comprising a plurality of reactants,

wherein each reactant is placed in at least one of the plurality of cavities.

42. The device of claim 40 further comprising a plurality of reactants,

wherein more than one reactant is placed in at least one of the plurality of

cavities.

43. The device of claim 33 wherein the reactant is selected from the

group consisting of a sensing particle, a receptor molecule attached to a sensing

particle, a gel or a reactive material.

44. The device of claim 43 wherein the sensing particle is selected from

the group consisting of functionalized polymeric beads, metal oxide particles, thin

polymer films, metal quantum particles, semiconductor quantum particles,

agarose, ceramic, glass, or any combination of the foregoing.

45. The device of claim 43 wherein the receptor molecule is selected

from the group consisting of signaling proteins, chemically sensitive dyes, nucleic

acid strands, nucleotide sequences, biological binding agents, antibodies,

antigens, organic metabolites, inorganic metabolites, functional group receptors,

or any combination of the foregoing.

46. The device of claim 33 wherein the substrate is comprised of glass,

plastic, silicon, resin, polymer, fiber composite, metal, metal alloy, ceramic, or any

combination of the foregoing.

47. The device of claim 33 wherein the reactant is a fluorescent based

reactant, and the light source is selected such that the frequency and wavelength

of the light compliments the excitation band of the selected fluorescent based

reactant.

48. The device of claim 33 wherein the reactant is a coiorimetric based

reactant, and the light source is a portion of the electromagnetic spectrum.

49. The device of claim 48 wherein the light source is a white light.

50. The device of claim 33 further comprising means for retrieving optical information from within the region of interest.

51. The device of claim 50 wherein the means for retrieving optical

information comprises a video monitor.

52. The device of claim 33 wherein said physical assembly is a probe.

53. The device of claim 33 wherein said physical assembly is spheroidal

in shape.

54. The device of claim 33 wherein the sensor and the detector are

integrated with a catheter to introduce the sensor and the detector to the region of

interest.