WO1989007254A1

WO1989007254A1 - Infrared transmitting probe and assays using same

Info

Publication number: WO1989007254A1
Application number: PCT/US1989/000351
Authority: WO
Inventors: Louis Pierre De Rochement; Robert C. Davenport, Jr.
Original assignee: Spectran Corporation
Priority date: 1988-01-28
Filing date: 1989-01-27
Publication date: 1989-08-10

Abstract

The present invention relates to biological and chemical assays that utilize an infrared (IR) light transmitting glass optical probe. The invention also relates to novel optical fiber structures that are particularly useful in biological and chemical assays.

Description

INFARED TRANSMITTING PROBE AND ASSAYS USING SAME

BACKGROUND OF THE INVENTION

The present invention relates to biological and chemi¬ cal assays that utilize an infrared (IR) light transmitting glass optical probe. The invention also relates to novel optical fiber structures that are particularly useful in biological and chemical assays.

The analysis and detection of minute quantities of substances in biological samples in-vitro and in-vivo. has become a routine practice in clinical and analytical labor_¬ atories around the world. Also, recently biological and chemical assays have almost become common-place for use by the layman, e.g. home-pregnancy test kits or a combat • soldier assaying an air sample to determine what neurotoxin is being utilized during a chemical warfare attack.

In biological and chemicals^' assays the substance to be determined is generally referred to as the "analyte" and the substance that is utilized to detect the analyte is gener¬ ally referred to as the "analyte-specific moiety".

The analyte and analyte-specific moiety can interact in one or both of two ways to permit the detection of the analyte. The analyte and analyte-specific moiety can inter_¬ act by participating in a chemical reaction. The chemical reaction can cause a change in the color of a dye or the emission of light, for example, each of which can be conveyed to a human directly or through an instrument, detec¬ tion system. It should be noted that in this scenario the interaction per se, i.e. chemical reaction, conveys to a human the presence of the analyte. The second way in which an analyte and analyte-specific moiety can interact is py their forming a complex with each other. Complex formation is based on a primary recognition event, brought about by precise molecular alignment and interaction, and energetically favored by the release of non-covalent bonding free energy (e.g., hydrogen bonding, dispersion bonding, ionic bonding, dipolar bonding and the like), whereby the analyte-specific moiety recognizes the

10 analyte to form a complex. In this method of detection, in addition to the primary recognition event, a signalling event is also required. This event relates to the necessity of conveying to a human or instrument detection system the formation of the complex.

T5 Signalling has been centered mainly in two broad areas: radioactive and non-radioactive techniques. Radioactive signalling has relied on radiolabeling of one or more components involved in the system, with such atoms as _______P, I, C, H, and the like. Detection is usually by means

2° of a radioactivity detector. Non-radioactive techniques have been used increasingly in the last few years, since they involve no radioactivity, thus making such techniques safer, cleaner and more stable towards storage. They have been developed to sensitivities as high if not higher than

25 radiolabeling techniques. Among the most common non-radio¬ active signalling techniques used at present are enzyme linked immunobiological assays (see, for example, Schuurs, A.H. et al., Clinlca Chimica Acta, 81: 1-40 (1977), fluores¬ cence, Bauman et al., Chromosoma, 84: 1-18 (1981), indirect

³⁰ im unofluorescence, Rudkin et al., Nature, 265: 472-473 (1977), avidin-biotin interactions. Manning, J. et al. Biochemistry, 16: 1365-1370 (1977), electron microscopy of electron dense nuclei such as ferritin. Broker, R.R. et al.

35 ■Nucleic Acids Research, 5: 363-384 (1978), latex attachment, Sodja, A., ibid 35: 385-401 (1978), combinations of the aforementioned techniques and others.)

The biological and chemical assays involving complex formation generally comprise fixing the analyte to a solid support, eg., a nitrocellulose filter, blocking areas of the solid support that no analyte moieties are fixed with a blocking agent, followed by contacting the analyte with the analyte-specific moiety to form the complex. The analyte- specific moiety generally has the signalling moiety attached thereon. The nonco plexed analyte-specific moieties are separated from ones that are co plexed by washing, for example. This separation step is required to prevent a false positive result. The signal is then generated by means of the signalling moiety. The signal can be, for example, radioactive, enzymatic or fluorescent. The genera¬ tion of a signal indicates the presence of the analyte moiety.

An example of a biological assay involving complex formation is an immunoassay, which involves the non-covalent association between an antibody and its antigen. See, for example, T. Chard, An Introduction to Radlolmmunoassay and Related Techniques, North Holland Publishing Company, Amsterdam, New York, Oxford, 1978. Another example of a biological assay involving complex formation is a hybridiza¬ tion assay. This assay involves the noncovalent association of a nucleotide sequence to a complementary nucleotide sequence under hybridization conditions. (See, for example, Fal ow et al., U.S. Patent 4,358,535, Wahl et al, U.S. Patent 4,302,204 and Hei er, U.S. Patent 3,755,086.) An analyte and analyte-specific moiety can also inter¬ act by both forming a complex with each other and partici¬ pating in a chemical reaction. For example, cyclodextrins, as discussed hereinbelow, can form a complex and particpate in a chemical reaction with its substrate.

Recently, it has been proposed to utilize an optical probe to detect a signal in a biological assay. For example, an optical fiber probe was utilized for detecting . and monitoring antibody-antigen reactions at a solid-liquid interface. The antibody was covalently immobilized onto the surface of the optical fiber probe. The reaction of the immobilized antibody with antigen in solution was detected through use of the evanescent wave component of a light beam, which has a characteristic depth of penetration of a fraction of a wavelength into aqueous phase, thus optically interacting primarily with substances bound, (or located very close)- to the interface and only minimally with a bulk solution. The article also points out that this immunobio- logical assay is homogenous, i.e., no separation step is required to separate the antigens that complex with the antibody from the antigens that do not form a complex with an antibody. See R.M. Sutherland et al., Optical Detection of Antibody-Antigen Reactions at a Glass-Liquid Interface, clinical Chemistry 30/9,1533-1538 (1984).

An optical fiber probe has been utilized to detect a che iluminescent reaction. This is an example of a biologi¬ cal assay wherein the interaction of the analyte-specific moiety results in a chemical reaction rather than the for a- tion of a complex. The assay was carried out by utilizing an optical fiber probe for the detection of hydrogen peroxide based on the luminol reaction. This is accom¬ plished by immobilizing peroxidase in a polyacrylamide gel on the end of an optical fiber probe. When the probe is immersed in a solution of peroxide in the presence of excess luminol, chemiluminescence is generated as peroxide diffuses into the peroxidase phase. The optical fiber is utilized to transmit the chemiluminescence to a detector. See Freeman et al., Chemiluminescent Fiber Optic Probe for Hydrogen Peroxide Based on the Luminol Reaction, Analytical Chemistry, vol. 50, No. 9, August 1978.

An optical fiber probe has also been utilized to meas¬ ure blood PH and blood gasses, PO, and PC0₂ in-vivo. This assay is based upon the variation in fluorescence intensity of certain dyes in response to changes in arterial blood gasses. The optical fiber probe is utilized to collect the light generated from the fluorescent dye. See w.w. Miller et. al, Performance of an .In-ylvo, Continuous Blood-Gas Monitor with Disposal Probe, Clinical Chemistry, 33/9, 1538-1542 (1987). Other medical applications of optical fiber probes have been suggested. See J.S. Schultz, Medical Applications of Fiber Optic Sensors, Medical Instrumenta¬ tion, Volume 19, No. 4, July-August 1985.

All optical probes detect a signal, which indicates the presence of an analyte, based on one of the following four phenomena: l. Absorption of Light - The absorption of light is the physical uptake of a photon of light by a chemical compound. The energy of the photon is transferred to the chemical compound. A compound that can absorb photons, absorbs photons only of specific wavelengths of light. The wavelengths that are absorbed depend on the chemical struc- ture of the compound. For example, an antibody can absorb light at a wavelength of about 280nm. This is based upon the fact that an antibody is a protein comprised of a - sequence of a ino acids, which sequence can include the a ino acids phenylalanine, tyrosine and tryptophan. Each of 7254

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these amino acids has an aromatic group which is capable of absorbing light at about 280 nm. A nucleotide sequence can absσrb light at about 260 nm. This is due to the fact that the base of the nucleotide may be thymidine, guanine or adenine, each of which can absorb light at about 260 nm.

If a chemical compound is in the icroenvironment of an optical probe, such as on the outer surface of the optical probe, then as light of the wavelength that is capable of being absorbed by the chemical compound is passed through the optical probe, at least a portion of the light that is capable of being absorbed will be absorbed. At the end of the optical probe one can, be means of a photodetector, measure the decrease in the quantity of light that is present at such wavelength. This decrease indicates the presence of the chemical compound. Thus, for example, if an antibody/antigen complex can absorb light, then one can measure the presence of such complex in this manner. Also, a shift in the absorption of light can result from the formation of an analyte/analyte-specific moiety complex. This shift in absorption can also be detected.

2. Emission of Light- The emission of a light occurs when a chemical compound gives off a photon. Like absorp¬ tion, an emission is of a specific wavelength. For example, in the chemical reaction of peroxide and luminol in the presence of peroxidase, light is given off, i.e., an emission of photons takes place at 430nm. If the chemical compound is in the microenvironment of an optical probe, then this light can be transmitted through the optical probe and detected by a photodetector.

3. Absorption/Emission of Light- This principle combines the first. two principles. This principle involves applying a specific wavelength of light to a chemical compound, which is absorbed, thereby resulting in the compound giving off light of different specific wavelength, i.e., an emission. If the chemical compound is in the microenvironment of an optical probe, then the emission of light can be transmitted through the optical probe and detected by a photodetector. An example of this principle is a fluorescent reaction.

4. Transmittance of Light - This principle involves applying light to a solution and only specific wavelengths of the light are transmitted through the solution. The wave¬ lengths of the transmitted light can be measured. If the solution is in the microenvironment of the optical probe, then the transmitted wavelengths can be transmitted through the optical probe and detected by a photodetector. A simple example of this system is a dye in solution.

Optical probes transmit light of wavelengths only within a defined optical transmission bandwidth. For example, most optical probes are made of silica glass, which transmits light only in a bandwidth of from about 200 nm. to about 2,000 nm. Thus, if the wavelength of light that one wants to detect is outside this range, a silica optical probe would be of no use in detecting the light.

Accordingly, there is the need for an optical probe that has a very broad optical transmission bandwidth, especially of wavelengths greater than about 2,000 nm.

SUMMARY OF THE INVENTION

This invention relates to a method for detecting an analyte which comprises:

A. contacting said analyte or a mixture of said analyte and said analyte labeled with an entity that is capable of fluorescence or absorption of light with an analyte-specific 7254

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moiety in the microenvi onment of an infrared ' light transmitting glass optical probe under conditions that permit said analyte to be detected by the absorption of light, emission of light, absorption/emission of light or the transmittance of light, and B. detecting said analyte by means of said infrared light transmitting glass optical probe. The invention also relates to a novel optical fiber structure that is particularly useful as an optical probe. The optical fiber structure comprises an outer layer optical core having an index of refraction which can transmit opti¬ cal information of a predetermined wavelength and a layer of optical cladding material inwardly adjacent to said outer layer optical core wherein said outer layer optical core has an index of refraction which is greater than that of said optical cladding material. It is believed that such an optical fiber structure is particularly useful as a probe because the optical cladding material "pushes" more light to the outer surface of the optical core. The more light that is present on the outer surface of the optical core permits a more sensitive biological or chemical assay, especially when an evanescent wave component of a light beam is utilized to detect the analyte.

•DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a method for detecting an analyte by means of an infrared light transmitting glass optical probe. The term "analyte" as used in the specifica¬ tion and claims includes any substance whose presence is to be detected and, if necessary, quantified. It is believed the analyte can be a molecule of small or high molecular weight and the invention is intended to cover any chemical compound that is to be detected. Among the common analytes are proteins, polysaccharides, lipopolysaccharides, substrates, protein complexes, nucleic acids or segments thereof, H⁺ions - which permits the determination of pH, CO 2 and 0₂, which can be utilized to determine blood p0_ and pC0₂. Among the common proteins are the structural pro¬ teins, enzymes, immonuglobulins or fragments thereof. Among the most common nucleic acids are DNA and RNA of various different types, eg. rRNA, mRNA, rRNA and the like.

The analyte can be detected with an analyte-specific moiety. As discussed hereinabove, the analyte-specific moiety can interact with the analyte to permit the detection of the analyte in one or both of two ways. Contacting the analyte with the analyte-specific moiety can result in a chemical reaction and/or the formation of a complex. Examples of analyte-specific moieties^' that operate by means of complex formation include a nucleotide sequence than can recognize the nucleotide sequence of the analyte, an anti¬ body that can recognize its antigen, a lectin that can recognize its sugar, an inhibitor that recognizes its enzyme, a hormone that can recognize its hormone receptor, or vice-versa. Examples of analyte-specific moieties that operate by means of a chemical reaction include dyes that change color upon interacting with the analyte, eg. a dye whose color changes with a change of pH. Another example is the use of luminol to detect hydrogen peroxide. Luminol reacts with hydrogen peroxide in the presence of peroxidase to generate chemiluminesence.

An example of ah analyte-specific moiety that can operate by means of complex formation and a chemical reac¬ tion are the cyclic polysaccharides cyclodextrins. The cyclodextrins form a complex by binding with a substrate in the cavity of the cyclodextrin. The-cyclodextrin can then, depending on the substrate, perform a chemical reaction with the substrate, which results in the substrate and cyclodex¬ trin forming a covalent bond. Generally, it is the hydroxyl groups of the cyclodextrin that react with the substrate. However, various substituents that are capable of performing a chemical reaction with the substrate can be attached to the cyclodextrin. See R. Breslow, Bio imetic Chemistry in Oriented Systems, Israel Journal of Chemistry, vol. 18, 187-191 (1979).

It is preferred to utilize substrates that can also form a covalent bond with a cyclodextrin. This is because the covalent bond -is irreversible and, therefore, during the biological or chemical assay the substrate/cyclodextrin complex will remain bound. Accordingly, over time, a more sensitive assay can be performed than with a substrate that only binds the cyclodextrin. The binding of the substrate to the cyclodextrin is a reversible process.

The preferred cyclodextrins are alpha, beta and gamma cyclodextrin. An example of a suitable substrate for alpha cyclodextrin are phosphate-based neurotoxins, e.g. isopropyl ethylphosphonofluoridate (Sarin) . See C. van Hooidonk et al., Model Studies For Enzyme Inhibition, Part II, RECUEIL Des Travaux Chemiques de Pays-bas, 89, 845-856 (1970). Suitable substrates for beta and gamma cyclodextrin include steroids, e.g. progesterone, and cardiac glycosides. For an excellent review of cyclodextrins see J. Szejtli, Cyclodextrins And Their Complexes (Akademiai, Budapest, 1982)

The method of the invention utilizes an infrared light transmitting glass as an optical probe. Glass that trans¬ mits light in the IR region, i.e. from about 2,000nm. to about 16,000nm., as discussed hereinbelow, can be very useful as an optical probe. It is believed that any glass that transmits light in at least a portion of the IR region can be utilized. Nonlimiting examples of suitable glasses are chalcogenide glasses and fluoride glasses, with fluoride glasses being preferred. Chalcogenide glasses have an opti¬ cal transmission bandwidth of from about l,000nm. to about 10,000nm. Fluoride glasses have a multispectral optical transmission bandwidth, from about 200nm. to about 8,000nm. This broad range of optical transmission is useful because light of a plethora of wavelengths useful to molecular spectroscopy (ultraviolet, visible and the mid-IR) can be transmitted through fluoride glass and, therefore, used in biological and chemical assays.

Light in the IR region can be utilized to generate bond deformations of chemical compounds. The light that causes the bond to deform is absorbed by the compound. The bond deformation of each compound is virtually unique, and, therefore, the absorption pattern is unique. Thus, virtu-- ally any compound can be "fingerprinted". The bond deforma¬ tions can be detected - by measuring absorption of light - and recorded - with a spectophotometer. This is the basis for the field that is commonly known as "infrared spectros¬ copy. " An infrared light transmitting glass optical probe can be utilized to gather a tremendous amount of information that heretofore could not be gathered with an optical probe. For example, analytes that are not easily signalled in the optical transmission bandwidth of from about 200nm. to about 2,000nm. (typical silica glass) now can be detected.

Furthermore, even chemical compounds that can absorb, emit, absorb/emit or transmit light in a wavelength of from about 20^'0nm. to about 2,000nm., can be more precisely character¬ ized by complementary information from the IR region. Also, analytes that form a complex with an analyte-specific- moiety produce a change in the bond deformation of the analyte- specific moiety produced by light in the IR region. This change causes a shift in the absorption pattern, which can be detecte .

Any chalcogenide glass can be utilized in the^' invention for a chalcogenide glass optical glass probe. Suitable chalcogenide glasses are compositions utilizing germanium, selenium and arsenic in the glassy states and glassy mixtures thereof.

Any fluoride glass can be utilized in the invention for a fluoride glass optical probe. Among the best known of the fluoride glass-forming systems are the compositions based on BeF,. A number of other fluoride glass compositions have been recently discovered. U.S. Patent No. 4,141,741 discloses a family of ZrF. based glass-forming compositions in the ZrF₄-BaF₂~ThF₄ composition systems which exhibit infrared transparency out to about 7 microns and which are non-hygroscopic. U.S. Patent No. 4,308,066 discloses a family of fluoride compositions based on Z ₄ and/or AlF,, containing 20-80 mole percent of CaF₂, SrF₂, BaF₂, and/or PbF₂, which will form glasses if rapidly quenched.

M. Matecki et. al. describe, in Mat. Res. Bull. , 17, 1035-1043 (1982), a series of T F₄-ZrF₄ compositions containing fluorides selected from the group LaF₃, YF., CdF-,- LuF-, ScF₃ as glass modifiers. These compositions provide relatively stable glasses, exhibiting glass transi¬ tion temperatures in the »460*-515^βC. range, which can.be formed by casting and are infrared-transparent out to about 7 microns.

Glasses based on fluorides other than ZrF 4. are also known. S. Shibata et al. disclose, in Mat. Res. Bull., 15, 129-137 (1980), a family of PbF₂~based glasses in the PbF₂~ A1F_ system which will form glasses rapidly quenched. . Matecki et al.. Mat Res. Bull. , 17, 1275-1281 (1982) report glasses based on CdF₂, including binary CdF₂-BaF₂ and tern¬ ary CdF₂-BaF₂-ZnF₂ compositions optionally containing A1F_, YbF₃, ThF. and/or alkali metal fluorides. Other suitable compositions are disclosed in U.S. Patents: 4,445,755; 4,380,588; 4,358,543; 4,346,176 and 4,328,318.

The infrared light transmitting glass optical probe can be any shape, e.g. planar - a glass slide or cylindrical - a fiber. However, a fiber is preferred because light can be transmitted down the fiber, rather than just reflecting off a slide, which results in more internal reflections and, therefore, more information for a given amount of input light can be obtained.

It is preferred that the outer surface of the infrared light transmitting glass optical probe have a hermetic coat- ing thereon. The hermetic coating is utilized to protect and enhance the durability of the glass. Infrared light transmitting glass can easily corrode and crack due to the moisture in the atmosphere. It is essential that the hermetic coating be optically transmissive to regions of the optical spectrum for which it is desired that the infrared light transmitting glass optical probe be utilized, especially when an evanescent wave component of a light beam is utilized to detect the analyte . Suitable hermetic coat¬ ings include magnesium oxide; thorium fluoride and magnesium fluoride, with magnesium oxide being preferred. The optical spectrum transmission bandwidth for magnesium oxide is from about 200 nm. to about 8,500nm. The hermetic coating can be applied by chemical vapor deposition. For example, see copending application U.S. Serial No. 846,331, filed March 31, 1986, entitled Hermetic Coatings for Non-Silica Based Optical Fibers, the disclosure of which is incorporated herein by reference. It should be noted that chalcogenide glasses are more durable than fluoride glasses and, therefore, a hermetic coating is not as necessary.

It is also preferred that when the infrared light transmitting glass optical probe is a fiber that its struc¬ ture be comprised of an outer layer optical core having an index of refraction which can transmit optical information of a predetermined wavelength and a layer of optical cladding material inwardly adjacent to said outer layer optical core whrein said outer layer optical core has an index of refraction which is greater than that of said optical cladding material.

This structure is particulary useful when the analyte is detected through the use of an evanescent wave component of a beam of light. In this instance the analyte-specific moiety is located in the microenvironment of the outer surface of the optical core and preferably on the outer surface of the optical core. For an excellent discussion of the use of an evanescent wave component of a beam of light to detect an analyte with an optical probe, see J.D. Andrade et al. , Remote Fiber-Optic Biosenors Based on Evanescent- Excited Fluoro-immunoassay: Concept and Progress, Transac¬ tion on Electron Devices, Vol. Ed-32, No.7, July 1985 and R.M. Sutherland et al.. Optical Detection of Antibody- Antigen Reactions at a Glass-Liquid Interface, Clin. Chem. , 30/9, 1533-1538 (1984). It is believed that such a struc¬ ture for the optical fiber probe "pushes" the light near the outer surface of the optical fiber probe as light is trans¬ mitted down the optical fiber, resulting in enhanced sensi¬ tivity of the optical fiber probe. This optical fiber structure can be utilized to obtain an enhanced outer surface sensitivity with not only an infrared light trans¬ mitting glass optical fiber probe but also with any type of glass optical fiber probe, eg. silica glass.

The optical cladding material can be any glass that has a lower refractive index than the optical core material. It is preferred to utilize optical cladding material that is compatible with the optical core. For example, for use with a fluoride glass optical core, an optical cladding material comprised of a mixture of hafnium fluoride, aluminum fluor¬ ide, zirconium fluoride, lanthium fluoride and barium fluor¬ ide is preferred.

It is preferred that the optical cladding material be from about 25 microns to about 100 microns in diameter. It is preferred that the thickness of the optical core be from about 100 microns to about 2,000 microns, i.e. the diameter of the optical fiber glass probe will be from about 125 microns to about 2,100 microns. It is preferred that the optical fiber probe be from about 0.5 cm. to about 6 cm. in length.

The optical fiber glass probe of the invention can be made by the method described in U.S. Patent 4,519,826, the disclosure of which is incorporated herein by reference.

The method of the invention can encompass virtually any biological and chemical assay that is known that utilizes an optical probe and any biological and chemical assay.to be developed in the future that utilizes an optical probe.

A biological and chemical assay with an optical probe is generally carried out as follows: The analyte-specific moiety is immobilized within the microenvironment of the optical probe. For purposes of the present invention, the term "microenvironment" of the optical probe includes a distance of up to 25 microns from the nearest point of the outer surface of the optical probe. hat is essential is that the analyte-specific moiety be located where it can be utilized to detect the analyte by means of the optical probe. The analyte-specific moiety can be located at the end or on the outer surface of the optical probe. When the assay is carried out in a solution, the analyte-specific moiety will aggregate at the solution-optical probe inter¬ face. It is preferred that the solution have a refractive index that permits the solution to act like a cladding material.

The analyte-specific moiety can also be placed on the outer surface of the optical probe by binding the analyte- specific moiety to the outer surface of the optical probe by means of a polymer. This is carried out by binding one end of the polymer to the analyte-specific moiety and binding the other end of the polyme to the outer surface of the optical probe. Thus, any polymer with these chemical properties can be utilized herein. This results in the formation of a polymeric film on the outer surface of the optical probe. It is preferred that the density of the polymeric film be sufficient to form organic crystals.

One can bind the analyte-specific moiety to the outer surface of the optical probe by means of a polymer by utilizing the Langmuir/Blodgett technique, in this tech- nique the polymer must have a hydrophobic tail and hydrophi- lic head. The technique results in the analyte-specific moiety being bound to the hydrophobic tail and the outer surface of the optical probe being bound to the hydrophilic head. Thus, a polymeric film is formed on the outer surface of the optical probe.

The analyte-specific moiety is then contacted with the analyte. As discussed hereinabove, the contacting step results in one or both of a chemical reaction or complex formation. The analyte is then detected by the optical probe. This can be accomplished by measuring the absorption of light, emission of light, absorption/emission of light or the transmittance of light. It should also be noted that an analyte can be detected by utilizing more than one of these measurements.

As an alternate embodiment, a standard "competition" assay can be utilized. In this embodiment the analyte is labeled with an entity that is capable of fluorescence or the absorption of light. The labeled analyte then competes with the analyte for binding sites on the analyte-specific moiety. The more of the labeled analyte that binds to the analyte-specific moiety, the less analyte that is present. A competition assay with an optical fiber probe is described in J.S. Shultz, et al. Affinity Sensor: A New Technique For Developing Implantable Sensors for Glucose and Other Metabo¬ lites, Diabetes Care, Vol. 5, No. 3, May-June 1982 and J.D. Andrade et al., Remote Flber-Optlc Biosensors Based on Evanescent-Excited Fluro-lmmunoassa : Concept and Progress, IEEE Transactions on Electron Devices, Vol. ED-32, No.7,

July 1985, the disclosures of which are incorporated herein by reference.

The absorption, emission, absorption/emission and transmittance of light can be measured with an optical probe as follows:

1. Absorption of Light - The absorption of light can be measured by passing light of a wavelength that is capable of being absorbed by the complex through the optical probe and then measuring the absorption of light with a photo- detector.

An assay that is particularly useful with a fluoride glass optical fiber probe is one wherein the absorption measured is a shift in the absorption of light resulting from the formation of a complex of the analyte and analyte- specific moiety, i.e. the change in the absorption of light of the analyte-specific moiety caused by complex formation with the analyte. A shift in absorption is particularly useful to measure with a infrared transmitting glass optical fiber probe because such a shift is most likely to be detected with light in the infrared region. 5 2. Emission of Light- The emission of light is meas¬ ured by utilizing the optical probe to transmit the light emitted to a photodetector.

An optical fiber probe has been utilized to detect the emission of light caused by an enzyme-catalyzed process.

10 For example, an optical fiber probe has been utilized to detect the light generated by the chemical reaction of pero¬ xide, the analyte-specific moiety, and luminol in the pres¬ ence of peroxidase. The reaction is carried out at the end of the optical fiber probe. See T.M. Freeman, et al., Chemi-

T5 luminescence Fiber Optic Probe for Hydrogen Peroxide Based on the Luminol Reaction, Anal. Chem., Vol. 50, No. 9, Aug. 1978, the disclosure of which is incorporated herein by . reference.

3. Absorption/Emission of Light - The

20 absorption/emission of light is measured with an optical probe by contacting the analyte/analyte-specific moiety complex with a wavelength of light that the complex absorbs. The light that is emitted is transmitted through the optical probe to a photodetector.

25 A primary example of the use of this principle is a fluorescent reaction. There are numerous examples in the art of that use optical probes for the detection of emissions generated by fluorescence. For example, a competition biological assay for the detection of glucose

30 has been utilized. This competition biological assay uses fluorescein labeled sugar that competes with the glucose for

35 the binding site on the lectin Concanavalin A. (Sugars and lectins upon contact form a complex.) Thus, the less glucose that is present in the sample, the more fluorescein labeled sugar that will bind to Concanavalin A. The fluorescein is then utilized to generate a fluorescent reaction, with the optical fiber probe being utilized to detect the emission of light. .See J.S. Schultz, Affinity Sensor: A New Technique for Developing I plantable Sensors for Glucose and Other Metabolites, Diabetes Care, Vol. 5 No. 3, May-June 1982, the disclosure of which is incorporated herein by reference.

An optical fiber probe has been utilized with a fluorescent reaction to detect heavy metal ions. For example, the dye morin becomes fluorescent in the presence of Al .. See J.S. Schultz, Medical Applications of Fiber¬ optic Sensors, Medical Instrumentation, Vol. 19, No. 4 July - Aug 1985, the disclosure of which incorporated herein by reference. ^' Note that in the latter example the fluorescent entity is created by the presence of the analyte whereas in the .former example a fluorescent entity is utilized as a signalling entity. The latter Schultz article also discloses how optical fibers that generate a fluorescent reaction can be utilized to monitor regional blood flow and the oxidation-reduction state of tissues. A fluorescent reaction has also been utilized in an immunoassay with an optical fiber probe. See J.D. Andade, et.al.. Remote Fibe -Optic Biosensors Based on Evanescent-Excited Fluoro- immunosasy Concept and Progress, Transactions on Electron Devis, Vol.Ed.-32, No. 7. July 1985. 4. Transmittance of Light- In this embodiment analytes are detected by the use of dyes, which change color depend¬ ing on the presence or concentration of the. analyte. The dye is located in the microenvironment of the optical probe and then light is transmitted through the dye and the opti- cal probe and the wavelengths of light that are transmitted are measured by a photodetector. Those wavelengths that are transmitted depend on the color of the dye, which is depend¬ ent upon the presence and/or concentration of the analyte. The transmittance of light has been utilized to determine the pH, pC0₂ and p0₂ of blood, acetylcholine, arginine, creatinine, penicillin, acetaldehyde, tyrosine and insulin.

In this instance an optical fiber probe is particularly useful because it can be part of a catheter, which can be inserted in the blood stream or inside organs. The follow¬ ing articles discuss the use of optical fibers for detection of analytes via transmittance: J.I. Peterson, Fiber Optic Chemicals Sensors^" - A View From the Past to- the Future, IEEE/NSF Symposium on Biosensors - 1984 and W.F. Regnault et al. , Review of Medical Biosensors and Associated Materials Problems, J. Biomed Mater. Res.: Applied Biomaterials, Vol.21, No. A2, 163-180 (1987), the disclosures of which are incorporated herein" by reference.

Claims

What is claimed is:

1. A method for detecting an analyte which comprises:

A. contacting said analyte or a mixture of said 5 analyte and said analyte labeled with an entity that is capable of fluorescence or absorption of light with an analyte-specific moiety in the microenvironment of an infrared light transmitting glass optical probe under 0 conditions that permit said analyte to be detected by the absorption of light, emission of light, absorption/emission of light or the transmittance of light, and

B. detecting said analyte by means of said infra- 5 red light transmitting glass optical probe.

2. The method of claim 1 wherein said infrared light transmitting glass optical probe is a fiber.

0 3. The method of claim 2 wherein said infrared light transmitting glass optical probe is made of a glass selected from the group consisting of fluoride glass and chalcogenide glass.

s 4. The method of claim 3 wherein said glass is a fluoride glass.

5. The method of claim 4 wherein said fiber has an outer surface and said outer surface has a hermetic coating 0 thereon.

6. The method of claim 5 wherein said hermetic coating is magnesium oxide.

5

7. The method of claim 4 wherein said contacting results in the. formation of a complex that is capable of absorbing light and said detection step comprises:

(i) passing light of a wavelength that is capable of being absorbed by said complex through said infrared light transmitting glass optical probe and

(ii) measuring said absorption.

8. The method of claim 7 wherein measuring said absorption comprises measuring a shift in absorption.

9. The method of claim 7 wherein said fiber has an outer surface, and said analyte-specific moiety is on said outer surface.

10. The method of claim 9 wherein said analyte-specific moiety is bound on said outer surface by means of a polymer.

11. The method of claim 7 wherein said complex is selected from the group consisting of an antibody complexed to an antigen and a nucleotide sequence complexed to its complementary nucleotide sequence.

12. The method of claim 4 wherein said contacting results in a chemical reaction that emits light and said detection step comprises measuring said emitted light that is passed through said infrared light transmitting glass optical probe.

13. The method of claim 4 wherein said contacting results in the formation of a complex that is capable of the absorption/emission of light and said detection step co pri- ses:

(i) contacting said complex with light of a wave¬ length that is absorbed by said complex, and (ii) measuring the light that is emitted through said infrared light transmitting glass opti- cal probe.

14. The method of claim 13 wherein said complex is capable of fluorescence.

15. The method of claim 1 wherein said contacting results in a chemical reaction that causes a change in color of a solution in the microenvironment of said infrared light transmitting glass optical probe and said detecting step comprises: (i) passing light through said solution and

(ii) measuring the light that is transmitted through said solution and said infrared light transmitting glass optical probe.

16. An optical fiber comprising:

(i) an outer layer optical core having an index of refraction which can transmit optical information of a predetermined wavelength, and (ii) a layer of optical cladding material inwardly adjacent to said outer layer opti¬ cal core. wherein said outer layer optical core has an index of refrac¬ tion which is greater than that of said optical cladding material.

17. The optical fiber of claim 16 wherein said optical core is selected from the group consisting of silica glass, fluoride glass and chalcogenide glass.

18. The optical fiber of claim 17 wherein said optical core is a fluoride glass.

a) The optical fiber of claim 17 wherein said optical core is a chalcogenide glass.

19. The optical fiber of claim 16 wherein said optical core-has an outer surface and said outer surface has a hermetic coating thereon.

20. The optical fiber of claim 19 wherein said hermetic coating is magnesium oxide.

21. The optical fiber of claim 19 wherein said hermetic coating is magnesium fluoride.

22. The optical fiber of claim 17 wherein said optical core is a chalcogenide glass.

23. The method of claim 5 wherein said hermetic coating is magnesium fluoride.

24. The method of claim 5 wherein said hermetic coating is thorium fluoride.

25. A method for detecting an analyte that is capable of forming a complex with a cyclodextrin which comprises:

A. contacting said analyte or a mixture of said analyte and said analyte labeled with an entity that is capable of fluorescence or absorption of light with a cyclodextrin in the microenvironment of an optical probe to form a complex under conditions that permit said analyte to be detected by the absorption of light, emission of light, absorption/emission of light or the transmittance of light, and

B. detecting said analyte by means of said optical probe.

26. The method of claim 25 wherein said contacting results in the formation of a complex that is capable of absorbing light and said detection step comprises:

(i) passing light of a wavelength that is capable of being absorbed by said complex through said optical probe and (ii) measuring said absorption.

27. The method of claim 26 wherein measuring said absorption comprises measuring a shift in absorption.

28. The method of claim 25 wherein said contacting results in the formation of a complex that is capable of the absorption/emission of light and said detection step comprises:

(i) contacting said complex with light of a wavelength that is absorbed by said complex, and (ii) measuring the light that is emitted by said complex through said optical probe.

29. The method of claim 28 wherein said complex is capable of fluorescence.

30. The method of claim 25 wherein said analyte is iospropyl methylphosphonofluoridate and said cyclodextrin is alpha cyclodextrin.

31. The method of claim 25 wherein said optical probe is a fiber.

32. The method of claim 31 wherein said fiber has an outer surface and said outer surface has a hermetic coating thereon.

33. The method of claim 32 wherein said hermetic coating is magnesium oxide.

34. The method of claim 31 wherein said fiber has an outer surface and said cyclodextrin is on said outer surface.

35. The method of claim 34 wherein said cyclodextrin is bound on said outer surface by means of a polymer.

36. The method of claim 25 wherein said optical probe is made of an infrared light transmitting glass.

37. The method of claim 36 wherein said infrared light transmitting glass is a fluoride glass.

38. The method of claim 25 wherein said analyte is selected from the group consisting of steroids and cardiac glycosides and said cyclodextrin is selected from the group consisting of beta and gamma cyclodextrin.

39. The method of claim 25 wherein said analyte and said cyclodextrin form a covalent bond.

40. The method of claim 40 wherein said analyte is a phosphate-based neurotoxin.

41. An optical probe which has in its microenvironment a cyclodextrin.

42. The optical probe of claim 41 wherein said optical probe is a fiber.

43. The optical probe of claim 41 wherein said optical probe is made of an infrared light transmitting glass.

44. The optical probe of claim 43 wherein infrared light transmitting glass is a fluoride glass.

45. The optical probe of claim 42 wherein said fiber has an outer surface and said outer surface has a hermetic coating thereon.

46. The optical fiber of claim 45 wherein said hermetic coating is magnesium oxide.

47. The optical probe of claim 42 wherein said fiber has an outer surface and said cyclodextrin is on said outer surface.

48. The optical probe of claim 47 wherein said cyclodextrin is bound on said outer surface by means of a polymer.

49. The optical probe of claim 47 wherein said cyclodextrin is complexed to an analyte that is capable of forming a complex with a cyclodextrin.

50. The method of claim 32 wherein said hermetic coating is magnesium fluoride.

51. The method of claim 36 wherein said infrared light transmitting glass is a chalcogenide glass.

52. The optical fiber of claim 45 wherein said hermetic coating is magnesium fluoride.