Optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid

Abstract

The invention relates to an optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid, comprising: (a) a removable substrate having two opposite faces called lower face and upper face, the breath fluid being exhaled on all or part of said substrate, (b) an emitter of optical radiation directed towards the upper face of said substrate, (c) a detector of all or part of the optical radiation emitted by the emitter, and in which all or part of the substrate is functionalized by a molecule having a specific chemical affinity for the target compound(s) such that the intensity of the detected optical radiation is substantially different in the presence or absence of said target compound(s).

Description

Title of the invention: Optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid Technical field.

[0001] The invention relates to an optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid. It also relates to a method for carrying out a test for detecting at least one target compound in a breath fluid by means of such a system. State of the art.

[0002] The use of reliable tests to detect very quickly whether a person has consumed drugs or is suffering from a viral infection presents major challenges in terms of road safety and / or public health. This has recently been confirmed for the COVID-19 epidemic where the need for rapid tests to massively diagnose a population is proving to be a key factor in slowing its progression.

[0003] However, most of the tests on the market aimed at detecting and quantifying such compounds are essentially carried out by blood, nasopharyngeal or saliva samples. The first two types of samples have the disadvantage of being rather slow (several hours or even several days for a diagnosis to be established) and require the presence of medical personnel to be carried out. This is the case for serological tests which measure the antibodies produced by the body during the immune response. This is also the case for PCR tests (abbreviation of the English term Polymerase Chain Reaction) which allow the direct detection of a virus by amplification of its genetic material, as well as antigenic tests based on the recognition of viral antigens on the surface of the virus's proteins.Saliva tests certainly have the advantage of being based on non-invasive samples, of having significantly lower response times (a few tens of minutes) and costs much lower than other tests, but they lack reliability and specificity for detecting a target compound.

[0004] The idea of ​​indirect detection of metabolites in exhaled air has been considered by several research groups in order to be able to carry out real-time tests. The two main technical solutions proposed by the research groups are based on mass spectrometry or on nanometric electrochemical sensors (https: / / pubs.acs.org / doi / pdf / 10.1021 / acsnano.0c05657). In both cases, the idea is to simultaneously detect a plurality of volatile organic compounds whose nature and concentrations are specific to a given viral infection. In addition to the fact that These techniques must be coupled with sophisticated algorithms to discriminate between pathologies and increase the specificity of these tests. Mass spectrometry remains an expensive technique that is difficult to miniaturize.

[0005] This is why the idea of ​​direct detection of target compounds in exhaled air is particularly advantageous. Indeed, many compounds are found in aerosols generated during exhalation, i.e. solid or liquid compounds suspended in exhaled air. This is the case, for example, of solid compounds such as cannabinoids found in the breath of cannabis users, or viruses trapped in micro-droplets. Researchers from the University of Nebraska recently published a study showing that the SarS-Cov-2 coronavirus was found in micro-droplets of less than 5pm exhaled into the ambient air by patients with COVID-9 (https: / / doi.org / 10.1038 / s41598-020-69286-3).

[0006] Finally, several research teams have shown that there are synthetic antibodies with a very high affinity for certain viruses such as SarS-Cov-2 and capable of blocking the infection of lung cells by the virus (https: / / doi.org / 10.1101 / 2020.08.24.264077).

[0007] The present invention aims to resolve all the drawbacks known in the state of the art by proposing an optical system capable of being integrated into a test device which can be at the same time rapid, specific to the target compounds, reliable, compact, simple to use, based on non-invasive sampling, and inexpensive. Presentation of the invention.

[0008] The solution proposed by the invention is an optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid, comprising:

[0009] (a) a removable substrate comprising two opposite faces called the lower face and upper face, the breath fluid being exhaled onto all or part of said substrate,

[0010] (b) an emitter of optical radiation directed towards the upper face of said substrate,

[0011] (c) a detector of all or part of the optical radiation emitted by the transmitter,

[0012] Said system is remarkable in that all or part of the substrate is functionalized by a molecule having a specific chemical affinity to the target compound(s) so that the intensity of the detected optical radiation is significantly different in the presence or absence of said target compound(s).

[0013] The system which is the subject of the present invention makes it possible to carry out a test for detecting the target compound in a breath fluid via a succession of steps consisting of:

[0014] (a) measuring the intensity of the optical signal having interacted with the functionalized substrate by a molecule: this is the reference measurement,

[0015] (b) bringing all or part of the functionalized substrate into contact with the gas exhaled by the breath fluid so as to adsorb the target compound if it is present in the exhaled gas,

[0016] (c) measuring the intensity of the optical signal on all or part of the functionalized substrate having interacted with the breath fluid: this is the final measurement,

[0017] (d) compare the two intensities measured during the reference measurement and the measurement final in order to assess whether the target compound is present or not.

[0018] The objective is therefore to trap the target compound by adsorbing it on the molecule used to functionalize the substrate, then to record on the detector the variation in the intensity of the optical signal over a range of wavelengths characteristic of the presence of the target compound on the substrate. This range of wavelengths can be the direct optical signature of the target compound, the variation in intensity of the signal being due to the absorption of said compound at these wavelengths. Alternatively, it can be the modification of the optical signature of the molecule in the presence of the target compound. This is the case, for example, if the molecule has a fluorophore that is active in the presence of the target compound and inactive otherwise. The change in structure or chemical nature of said molecule induced by the adsorbed target compound then results in a modification of the fluorescence intensity.

[0019] The targeted wavelength range is preferably narrow, i.e. less than 1 pm wide, so that the response is specific to the target compound. The narrower the band, the more specific the response. This may involve radiation in the ultraviolet, visible, or near or mid-infrared ranges.

[0020] The substrate is the physical support of the molecule having an affinity for the target compound. The molecule is preferentially immobilized on one of the external faces or inside the substrate if it has cavities. This immobilization step, also called functionalization of the substrate, consists of depositing said molecules either in liquid phase, or in vapor or gas phase, and on one or more surfaces of the substrate. At the end of the functionalization process, the molecule is found on the surface of the substrate. The interactions between the substrate and said molecule can be strong in the case of the formation of covalent or ionic bonds, or weak in the case of hydrogen or Van der Waals bonds. It may be advantageous to prepare the surface to be functionalized by a chemical or physical treatment aimed at facilitating the immobilization of the target molecule on the substrate.

[0021] A more complex alternative to implement is to encapsulate inside the substrate, for example between two glass slides, a liquid matrix containing said molecules. This can be advantageous if the molecules are only stable in solution, and if the aforementioned methods degrade the structure of the molecule.

[0022] This substrate is removable, which means that it can be easily removed from the system during the detection test, for example between the reference measurement step and the final measurement step, or at the end of the test, for example to recycle said substrate.

[0023] Finally, the substrate can be either transparent or reflective at the wavelengths of interest. It can be rigid or flexible and have multiple geometric shapes. The respective positions of the emitter, the substrate and the detector depend on both the optical and geometric characteristics of said substrate.

[0024] Other advantageous characteristics of the invention will appear in the description. Each of these characteristics can be considered alone or in combination with the remarkable characteristics defined above. Each of these characteristics contributes, where appropriate, to the resolution of specific technical problems defined further in the description and in which the remarkable characteristics defined above do not necessarily participate. The latter may be the subject, where appropriate, of one or more divisional patent applications. Brief description of the figures.

[0025] Other advantages and characteristics of the invention will appear more clearly on reading the description of a preferred embodiment which follows, with reference to the appended drawings, produced as indicative and non-limiting examples and in which:

[0026] [Fig.lA] shows a schematic view of a substrate according to the invention.

[0027] [Fig.lB] illustrates the conformation of a substrate in the form of a tube.

[0028] [Fig.lC] schematizes a detection system according to a first embodiment of the invention.

[0029] [Fig.2A] schematizes a detection system according to a second embodiment of the invention.

[0030] [Fig.2B] shows a schematic of an alternative embodiment of the detection system according to the second embodiment.

[0031] [Fig.2C] shows schematically another variant embodiment of the detection system according to the second embodiment.

[0032] [Fig.3A] shows a diagram of a detection system according to a third embodiment of the invention.

[0033] [Fig.3B] shows a schematic of an alternative embodiment of the detection system according to the third embodiment.

[0034] [Fig.3C] shows schematically another variant embodiment of the detection system according to the third embodiment. Description of the embodiments.

[0035] The target compound is advantageously a virus, i.e. one or more nucleic acid(s) enclosed in a protein capsid, with a size between 10 nm and 300 nm. All of the proteins constituting the virus are formed from a large number of amino acids linked together by a covalent chemical bond called a peptide bond. The vibration of the amide groups of the peptide bond produces absorption of infrared radiation in 3 spectral bands, including 2 intense absorption bands between 5.9 pm and 6.7 pm and a broad band between 7.1 pm and 8.3 pm. This absorption is a signature of the proteins, which is why it is advantageous to detect the variation in intensity of the radiation (in the presence or absence of virus) over one of these two wavelength ranges.

[0036] The emitter can emit in the infrared over a broad spectrum by Joule effect, typically between 2 pm and 15 pm. The emitter can for example consist of a MEMS type black body. In this case, the optical system can integrate, on the optical path located between the emitter and the detector, a narrow optical bandpass filter (not shown) centered between 6.0 pm and 8.2 pm, and preferably centered at 6.1 pm or 6.5 pm. The detector itself can be a pyroelectric detector, a micro-bolometer or a thermopile or even a photodetector.

[0037] Alternatively, the transmitter can be designed so that it emits over a narrow band of wavelengths. These may include photonic emitters such as quantum cascade lasers, LEDs or even nanostructured MEMS micro-sources which emit preferentially at the optical resonance wavelength of the nanostructures. The interest is then to avoid energy losses linked to the emission of the part of the spectrum not useful for detection, while avoiding the integration of an optical filter in the system.

[0038] Furthermore, the substrate is functionalized with a molecule having a chemical affinity specific to the virus that is to be detected. This molecule may be a synthetic protein with one or more recognition sites specific to said virus, so that said virus can adsorb onto the functionalized substrate. The chemical recognition mechanism involved is then similar to that used in the body for antibody-antigen recognition. The desorption of the target compound, necessary to recycle the substrates after a virological test has taken place, can be done by heating the substrate to temperatures above 50°C, or by using acidic or basic solutions. In both cases, the mechanism consists of breaking the bonds between the target compound and the molecule used to functionalize the substrate.

[0039] According to an alternative embodiment, the system can also incorporate a substrate heating device to be able to desorb the target compound without damaging the chemical structure of the molecules. This allows the functionalized substrate to be recycled or to avoid an accumulation of moisture that could interfere with the optical measurement.

[0040] Alternatively, the substrate may contain within it a heating resistor placed so that the functionalized part of the substrate can be heated. This may be, for example, a resistive metal filament which heats up by the Joule effect. This variant obviously increases the cost of the substrate and is therefore only of economic interest if it is desired to recycle the functionalized substrate.

[0041] The optical system that is the subject of the invention can be integrated into a device for detecting target compound(s) in an aerosol exhaled by a breath fluid. The user must then exhale air onto all or part of the functionalized substrate, typically for 3 seconds to 30 seconds and at a distance of 1 cm to 15 cm from said substrate. This operation can be done via a conduit (not shown) making it possible to guide the aerosol exhaled by the user from his mouth to the functionalized surface of the substrate. The system can integrate a measurement of the exhalation flow rate, via a pressure sensor for example, to calculate the volume of exhaled air and indicate to the operator that the test is finished. If the volume is insufficient to guarantee the reliability of the test, then he can be asked to carry out an exhalation operation again.

[0042] It may be a medical testing device for detecting viral pathology in breath fluid.

[0043] Another possible application concerns the detection of drugs in breath fluid, for example with target compounds from the cannabinoid family. In this specific case, the affinity molecules can then be synthetic mimics of the CB1 and CB2 receptors to which the cannabinoids bind in the body.

[0044] [Fig.lA] - The substrate 1 comprises two faces 1a, 1b which are opposite and called lower face 1a and upper face 1b. In the first two embodiments according to the invention, the upper face 1b of said substrate is reflective. All or part of the emitted optical radiation is then reflected on the upper face 1b of the substrate to be directed towards the detector. Typically, the substrate can be covered with one or more thin layers 2 of metal, preferably chosen from the following group: copper, silver, gold, cobalt, nickel, palladium, aluminum, chromium, zinc. These layers 2 have a thickness of between 100 nm and a few tens of pm, and can be deposited by bonding, by electrochemical deposition, by electrolytic deposition, by printing, by screen printing, heating, or by any other thin layer deposition process. The substrate can be rigid or flexible, transparent or not, for example made of glass or plastic.

[0045] [Fig.lB] - In a first embodiment, the substrate 1 whose upper face 1b is reflective is a thin film with a total thickness of less than 250 μm so that it is flexible. The substrate is advantageously made of a material chosen in the following group: polyimide, polyepoxide, polyester, glass fiber reinforced epoxy resin, aluminum. This substrate 1 can be shaped so as to form a tube 3. This tube 3 can be cylindrical (the 2 ends of the tube 3a, 3b being circular openings of the same dimensions) or truncated conical (the 2 ends of the tube being circular openings of different dimensions), without these shapes being limiting. The metal layer 2 forming the upper face 1b is then found inside the tube 3. It is this upper face 1b which is functionalized by a molecule having a specific chemical affinity to the target compound. The functionalization of the reflective surface can consist for example of a metal-ligand bond or a covalent bond.

[0046] [Fig.lC] - The emitter 5 and the detector 4 are located at each of the two ends 3a, 3b of said tube, which has the purpose of guiding the emitted radiation towards the detector 4 by multiple reflections on the metal layer 2. The advantage of such a configuration is to make the emitted radiation interact several times with the functionalized substrate, and thus to increase the sensitivity of the system. The emitter 5 advantageously comprises an optical reflector 6 designed to concentrate and direct the majority of the optical radiation emitted onto the tube 3 (in order to limit emissivity losses and optimize the number of optical reflections) while avoiding as much as possible that the detector receives the direct radiation of the non-reflected emitter. The substrate 1 forming the tube 3 can be pierced with one or more orifices (not shown) located near the ends 3a, 3b, said orifices being in fluid communication with the conduit.This configuration allows the breath fluid to be exhaled directly onto the upper face 1b located inside the tube 3 which is prepositioned in the optical system. This has the advantage of not modifying the respective positions of the substrate 1, the emitter 5 and the detector 4 between the reference measurement and the final measurement.

[0047] [Fig.2A] - In a second embodiment, the substrate 1 whose upper face 1b is reflective is advantageously planar, the emitter 5 and the detector 4 being located on the same side of the plane in which said substrate 1 is inscribed, namely on the side of said upper face 1b. The substrate 1 can be flexible or rigid. It is advantageous in this configuration to use an optical reflector 6 on the emitter 5 in order to control the interaction zone of the optical radiation emitted with the substrate, as well as a collector 7 on the detector in order to direct the maximum of optical radiation reflected on the face 1b of the substrate towards the detector 4. The reflector 6 and the collector 7 have perfectly reflective walls in order to maximize the specular reflections of the optical radiation on these two waveguides. It is also possible for the reflector 6 and the collector 7 to form a single piece (not shown).A person skilled in the art who knows the laws of geometric optics would be able to conceive. the shapes of the reflector 6 and the collector 7, as well as the distances and angles between the emitter 5, the detector 4 and the substrate 1 to maximize the intensity of the optical signal collected at the detector 4, and thus increase the sensitivity of the optical system.

[0048] [Fig.2B] - According to a first embodiment variant, the upper face 1b can also be subdivided into at least two zones 1b' and 1b”. The two zones 1b' and 1b” are functionalized by a molecule having a specific chemical affinity to the target compound. The surface density of said molecule on the two zones 1b' and 1b” are substantially identical so that the reference optical signal level of these two zones is the same. Only zone 1b' receives the exhaled air fluid, the reference zone 1b' being protected for example during the test by a film which is removed at the end of the test. After the expiration phase, the substrate 1 is positioned so that the radiation emitted by the emitter 5 only interacts with zone 1b” before being collected by the detector 4 (not shown). This first measurement step makes it possible to carry out the reference measurement.By translating the substrate 1 along the X axis, it is possible in a second measurement step to make the emitted radiation interact only with the zone 1b' so as to carry out the final measurement. In this configuration, the positions of the emitter 5 and the detector 4 are fixed and only the substrate 1 moves in the optical system.

[0049] [Fig.2C] - According to a second embodiment variant, the material constituting the substrate 1 is transparent, and the emitter 5 as well as the detector 4 are located on the side of the lower face 1a of the substrate, that is to say opposite the face 1b containing the reflective layer 2. In this variant, it is the lower face 1a which is functionalized. The advantage of such a configuration is that a ray emitted by the emitter 5 passes twice through the diopter formed by the functionalized surface 1a, before and after reflection on the layer 2. Thus, the variation in intensity of the optical signal in the presence of the target compound is increased, which makes it possible to increase the detection sensitivity of the optical system.

[0050] Figures 3 - In a third embodiment, the substrate 10 must be transparent ([Fig.3A]). The emitter 5 and the detector 4 are located on either side of the plane in which the substrate 1 is inscribed, namely on the side of the lower face 1a for the emitter 5 and on the side of the upper face 1b for the detector 4. All or part of the emitted optical radiation is then transmitted through the substrate 10 to be directed towards the detector 4. The material of the substrate 10 is chosen so that the transmission of said material at the wavelengths of interest is maximum. It may for example be a glass or a transparent plastic. Only one of the two faces 1a or 1b, or both faces 1a and 1b may be functionalized. The advantage of functionalizing several surfaces rather than one lies in the fact that the variation in intensity of the optical signal in the presence of the target compound is increased. This can be generalized to a stacking of several substrates 10', 10”, 10'” on top of each other, the radiation emitted by the emitter 5 then passing through a plurality of functionalized surfaces before being collected at the detector 4 ([Fig.3B]), which makes it possible to increase the detection sensitivity of the system. Another alternative is to use a substrate 10 structured by microgrooves 8 parallel to each other ([Fig.3C]). It is also advantageous, in the different configurations of Figures 3A, 3B and 3C, to use an optical reflector 6 on the emitter 5 in order to control the interaction zone of the optical radiation emitted with the substrate, as well as a collector 7 on the detector in order to direct the maximum amount of optical radiation towards the detector 4.

[0051] Said collectors 6 and 7 can be replaced respectively by diverging and converging lenses that a person skilled in the art would know how to place to obtain a comparable effect.

[0052] The arrangement of the various elements and / or means and / or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. Other variants may be provided. Furthermore, one or more features disclosed only in one embodiment may be combined with one or more other features disclosed only in another embodiment. Similarly, one or more features disclosed only in one embodiment may be generalized to the other embodiments, even if this or these features are described only in combination with other features.

[0053] :

Claims

Claims

1. Optical system for detecting at least one target compound present in an aerosol exhaled by a breath fluid, comprising: (a) a removable substrate (1) comprising two opposite faces called lower face (1a) and upper face (1b), the breath fluid being exhaled on all or part of said substrate, (b) an emitter (5) of optical radiation directed towards the upper face (1b) of said substrate on which the breath fluid has been exhaled, (c) a detector (4) of all or part of the optical radiation emitted by the emitter (5), and in which: - all or part of the substrate (1) is functionalized by a molecule having a specific chemical affinity to the target compound(s) so that the intensity of the detected optical radiation is substantially different in the presence or absence of said target compound(s),- the upper face (1b) of the substrate (1) is reflective and functionalized by the molecule having a specific chemical affinity to the target compound(s), all or part of the emitted optical radiation being reflected on said upper face to be directed towards the detector (4), - the system comprises a conduit for guiding the aerosol exhaled by the user from his mouth towards the functionalized surface of the substrate (1).,

2. System according to claim 1, wherein the target compound is a virus, the molecule functionalizing the substrate (1) being a synthetic protein provided with one or more recognition sites specific to said virus, so that said virus can adsorb onto said functionalized substrate.

3. System according to claim 1, in which the target compounds are from the cannabinoid family, the molecules functionalizing the substrate (1) being synthetic mimics of the CB1 and CB2 receptors to which the cannabinoids bind in the body.

4. System according to one of the preceding claims, comprising one of the following characteristics: - the substrate (1) is in the form of a tube having two ends (3a, 3b), the emitter (5) and the detector (4) being located at each of the two said ends, or - the substrate (1) is flat, the emitter (5) and the detector (4) being located on the side of the functionalized upper face (1b) of said substrate.

5. Method for carrying out a test for detecting at least one target compound in a breath fluid by means of a system according to claim 1, comprising the steps of: (a) measuring the intensity of the optical signal having interacted with the substrate (1) functionalized by a molecule: this is the reference measurement, (b) bringing all or part of the functionalized substrate into contact with the gas exhaled by the breath fluid so as to adsorb the target compound if it is present in the exhaled gas, (c) measuring the intensity of the optical signal on all or part of the functionalized substrate (1) having interacted with the breath fluid: this is the final measurement, (d) comparing the two intensities measured during the reference measurement and the final measurement in order to evaluate whether the target compound is present or not.

6. Method according to claim 5, comprising the steps of: - subdividing the upper face (1b) of the substrate (1) into at least a first zone (1b') and a second zone (1b”), - functionalizing the two zones (1b', 1b”) with a molecule having a specific chemical affinity to the target compound, the surface density of said molecule on the two said zones being substantially identical so that the reference optical signal level of these two zones is the same, - in a first test phase, only the first zone (1b') receives the exhaled air fluid, the second zone (1b”) being protected by a film which is removed at the end of the test, - after the test phase, positioning the substrate (1) so that the radiation emitted by the emitter (5) interacts only with the second zone (1b”) before being collected by the detector (4), this first measurement step making it possible to carry out the reference measurement,

7. - in a second final measurement step, translate the substrate (1) along an axis (X), so that the emitted radiation only interacts with the first zone (lb'). Method according to one of claims 5 or 6, comprising at least one of the following steps: - carry out the detection test on a target compound which is a virus made up of proteins, which proteins are formed of amino acids linked together by a peptide bond, the vibration of the amide groups of said peptide bond producing an absorption of infrared radiation in three spectral bands, including two intense absorption bands between 5.9 pm and 6.7 pm and a broad band between 7.1 pm and 8.3 pm, - use an emitter (5) which emits in the infrared on a spectrum by Joule effect between 2 pm and 15 pm, - integrate, on the optical path located between the emitter (5) and the detector (4), a narrow optical bandpass filter centered between 6.0 pm and 8.2 pm, and preferably centered at 6.1 pm or 6.5 pm.

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