METHOD FOR DETECTING A QUANTITY OF NO PRODUCED BY THE SUBJECT UNDER TEST, AND APPARATUS FOR CARRYING OUT SAID METHOD

Abstract

A method of tracking a physiological state in a subject by studying the NO emission curve thereof measured by a sensing element on the epidermis thereof over a predefined activity sequence.

Description

The invention relates to a method and a device for detecting, in a dead or living human or animal or plant subject, for example a physiological state and/or a physiopathological state of the subject. The invention also relates to a self-contained device for measuring NO for the purpose of determining a physiological or physiopathological state of the subject such as for example diagnosing and/or preventing the appearance of pathologies linked to this molecule and/or monitoring therapeutic efficacy.

It is known that nitric oxide is a gas which constitutes an intercellular messenger. NO plays an important role in the protection against the appearance and progression of certain cardiovascular diseases, certain neurodegenerative diseases, pulmonary arterial hypertension, or else oncogenesis. Associated cardiovascular pathologies include hypercholesterolemia, hypertension and diabetes. The underlying disease for most cardiovascular diseases (cerebral vessels, coronary arteries, lower limb ischemia) is a dysfunctional endothelial system, which is associated with arteriosclerosis which may lead to thrombotic and ischemic pathologies.

The cardioprotective role of NO includes in particular regulation of tension and vascular tone, inhibition of platelet accumulation, leukocyte adhesion and the proliferation of smooth muscle fiber cells. NO is also involved in bronchial inflammation; in particular it has been measured that the concentration of NO is higher in the air exhaled from asthmatic subjects than from non-asthmatic subjects. It has also been observed that NO is involved, depending on its concentration, in the appearance or regression of tumors. It has also been observed that NO is involved in the pathology of Alzheimer's disease. All of the diseases affected by NO fall within long-term disorders, the annual cost of which becomes greater each year and requires tools for preventing and predicting the appearance of these diseases.

In physiology, nitric oxide is a very good indicator of muscle growth and/or distress and therefore of the monitoring of the physical training of athletes and also of any person who undertakes a physical activity. Thus, by measuring the production of nitric oxide, it is possible to avoid injuries due to overtraining and/or to promote the uptake of NO in order to promote muscle growth and increase sporting performance. This applies both to humans and animals.

In the case of a cardiovascular disease, devices currently in existence and the tools for prevention and prediction are either limited to an indirect measurement of the NO of the patient at rest, or limited to a direct measurement delayed by several hours relative to an observation of a pathological problem. In all cases, the measurements can only be carried out in a clinical environment.

According to the present invention, a device is proposed that enables a direct, continuous and immediate measurement of the NO in a biological liquid, such as sweat, on an epidermis, such as the skin, in a subject such as a patient or a mammal, in its everyday life or at the time of a medical prescription in a clinical setting, optionally over several days and under all environmental conditions, in particular as regards pressure, humidity and temperature. Such a device makes it possible to detect and deduce the development of a physiological or physiopathological state such as a risk of appearance of pathologies or therapeutic monitoring.

One subject of the present invention is a method for detecting, in a subject, in particular a human or animal or plant subject, the subject being dead or living, an amount of NO produced by said subject in the course of a sequence of a predefined activity state, characterized in that an investigation zone of an epidermis of said subject is chosen, the production of NO dissolved in a biological liquid originating from the epidermis is tracked therein, directly and continuously, by means of a device formed of a first part, borne by said investigation zone and held thereon in a leaktight manner, this first part being attached to a sensing element, which carries out the detection of the NO by means of an electrochemical sensor, and that, owing to an energy generator associated with said sensing element, a signal is sent by said electrochemical sensor, the reading of which signal enables the desired detection.

The expression “NO in a biological liquid” is understood to mean that the NO is dissolved in a biological liquid.

The term “epidermis” is understood to mean the surface plant tissue forming a protective layer of the aerial parts of a plant or the surface layer of the skin in humans and animals.

The expression “biological liquid originating from the epidermis” is understood to mean any liquid produced by the subject and excreted via or by the epidermis of the subject. This biological liquid is for example the exudate in plants or the sweat in humans and animals.

The expression “in a leaktight manner” is understood to mean that gases, liquids and microorganisms such as bacteria or viruses located outside of the investigation zone cannot enter into the investigation zone. The leaktightness of the contact between the first part and the investigation zone ensures that the NO detected originates from the biological liquid produced by the investigation zone, and not from a flow coming from the outside.

The term “sequence” is understood to mean a time sequence i.e. a time interval. The expression “predefined activity state” is understood to mean the state in which the subject is in, for example carrying out a muscle exercise, sleeping, sitting down, running, immobile, or even dead, etc.

According to one embodiment, the method makes it possible to detect at least one parameter associated with a physiological state or a pathology.

According to one embodiment, the first part comprises a fibrous body in order to convey the biological liquid from the investigation zone to the sensing element by means of capillary forces.

According to one embodiment, the first part further comprises a filter configured to filter the biological liquid at an inlet of the sensing element in order to avoid distorting the detection of NO by interfering elements contained in the biological liquid.

According to one embodiment, the filter is a eugenol-type membrane.

According to some embodiments, the fibrous body may be a woven material, and a nonwoven material such as cotton.

In an alternative form of the method, use is made of at least one electrochemical sensor, which provides a signal as a result of an electrochemical measurement taken using the biological liquid, in particular sweat or exudate, produced by the subject in the investigation zone, as electrolyte between two work electrodes borne by an insulating planar support.

According to one embodiment, the insulating planar support comprises a material chosen from elastomers such as polydimethylsiloxane (PDMS), polyimides, epoxy resins and parylene.

Provision may be made, in the method according to one alternative form of the invention, for a reference electrode to be connected to the two work electrodes.

According to one embodiment, the reference electrode is a silver chloride (AgCl) electrode.

Provision may also be made for the sensing element to comprise a plurality of similar electrochemical sensors, the signals of which are combined to improve the output signal.

Provision may be made for the pattern of the electrodes relative to their support to follow a Hilbert curve, in order to improve the power of the output signal per unit area of the support.

According to one embodiment, the pattern of the electrodes relative to their support may follow another type of curve chosen from a Peano curve, a Sierpiński curve, a Moore curve and a Lebesgue curve, also for the purpose of improving the strength of the output signal per unit area of the support.

Provision may be made for the measurements to be carried out in line with orifices provided in the planar support, which is in line with the conductive patterns of the electrodes.

In an advantageous embodiment, the electrodes consist of metal deposits, in particular deposits of silver (Ag), gold (Au), platinum (Pt), and platinum black, or graphene deposits doped by nanoparticles of silver (Ag) or of gold (Au), the nanoparticles being functionalized by binders of NO, in particular guanylyl-cyclase or porphyrins.

According to one embodiment, metal deposits of gold are produced as clusters or produced by following a precise pattern, for example a hexagonal pattern.

For one implementation of the method according to invention, provision may be made for the device to further comprise a second part positioned above the first part, the second part containing electronics for receiving the raw measurements from the electrochemical sensor, converting them into an NO concentration and ensuring the transmission of the signal possibly with other parameters linked to the environment.

Provision may be made, in the method according to the invention, for the device to carry out and transmit measurements at a frequency that is a function of the activity state of the subject, this state being tracked by means of a gyroscopic and/or accelerometric module of the second part of the device.

According to one embodiment, the device comprises a geolocation module.

The invention also relates to a detection device for detecting, in a subject, an amount of NO produced by said subject in the course of a sequence of a predefined activity state, said device comprising a first part intended to be borne by an investigation zone of an epidermis of said subject and held thereon in a leaktight manner in order to track, directly and continuously, the production of NO in a biological liquid originating from the epidermis, the first part being attached to a sensing element, which carries out the detection of NO by means of an electrochemical sensor, and a second part configured to send, owing to an energy generator associated with said sensing element, a signal, the reading of which enables the desired detection.

Provision may be made for the sensing element to provide the signal as a result of an electrochemical measurement taken using the biological liquid, produced by the subject in the investigation zone, as electrolyte between two work electrodes borne by an insulating planar support.

In an abovementioned alternative form, provision may be made for a reference electrode to be connected to the two work electrodes.

According to one embodiment, the insulating planar support comprises at least one microchannel so as to guide the biological liquid to the electrochemical sensor.

Provision may be made for the sensing element to comprise a plurality of similar electrochemical sensors, the signals of which are combined to improve the output signal.

According to one embodiment, the sensing element comprises a plurality of electrochemical sensors distributed in a plurality of sensing units and in that each sensing unit is configured to detect at least one chemical species. The sensing element may then detect several different chemical species.

According to one embodiment, the insulating planar support comprises a plurality of microchannels, and each channel comprises a sensing unit.

Provision may be made, in the device according to the invention, for the pattern of the electrodes relative to their support to follow a Hilbert curve in order to improve the strength of the output signal per unit area of the support.

In such a device, the measurements are carried out in line with orifices provided in the planar support, which is in line with the conductive patterns of the electrodes.

Provision may be made, in the device according to the invention, for the work electrodes to consist of metal deposits, in particular deposits of silver (Ag), gold (Au), platinum (Pt), and platinum black, or graphene deposits doped by nanoparticles of silver (Ag) or of gold (Au), the nanoparticles being functionalized by binders of NO, in particular guanylyl-cyclase or porphyrins.

According to one embodiment, the first part comprises a fibrous body in order to convey the biological liquid from the investigation zone to the sensing element by means of capillary forces.

According to one embodiment, the first part further comprises a filter configured to filter the biological liquid at an inlet of the sensing element in order to avoid distorting the detection of NO by interfering elements contained in the biological liquid.

Provision may be made, in the device according to the invention, for the second part to be positioned above the first part, the second part containing electronics for receiving the raw measurements from the electrochemical sensor, for converting them into an NO concentration and ensuring the transmission of the signal possibly with other parameters linked to the environment.

Provision may be made, in the device according to the invention, for the device to carry out and transmit measurements at a frequency that is a function of the activity state of the subject, this state being tracked by means of a gyroscopic and/or accelerometric module of the second part of the device.

According to one embodiment, the device comprises a geolocation module.

In order to make the subject of the invention easier to understand, a description will be given hereinbelow, by way of purely illustrative and nonlimiting example, of one embodiment thereof, depicted in the appended drawing. In this drawing:

FIG. 1 depicts, in perspective, an external general view of a detection device according to the invention;

FIG. 2 depicts an overall view of a subject on whom a device according to the invention has been put in place;

FIG. 3 depicts an exploded view of the device from FIG. 1;

FIG. 4 depicts a block diagram corresponding to the operation of the device from FIG. 3;

FIG. 5 depicts a top view of a planar support bearing two electrodes put in place according to Hilbert curves;

FIG. 6 depicts a graph obtained from a healthy subject equipped with a device according to the invention, as indicated in FIG. 2;

FIG. 7 schematically depicts a first arrangement of the fibrous body and of the sensing element of the device;

FIG. 8 schematically depicts a second arrangement of the fibrous body and of the sensing element of the device;

FIG. 9 schematically depicts an electrochemical sensor of the sensing element comprising three electrodes according to a first embodiment;

FIG. 10 schematically depicts an electrochemical sensor of the sensing element comprising three electrodes according to a second embodiment;

FIG. 11 is a functional schematic depiction of a microhydraulic circuit arranged in the sensing element;

FIG. 12 is a cross-sectional view of the sensing element according to one embodiment.

With reference to the drawing, it is seen that the detection device according to the invention is denoted by 1 throughout; it is intended to take a quantitative measurement of NO in a healthy human subject. In the example described, the subject carries out a physical activity by the use of a bicycle corresponding to a power of 160 W. As FIG. 6 shows, the detection of NO is carried out from the start of the test (point 11) until the end of the test (point 12), i.e. for a time sequence of around 500 seconds. With reference to FIG. 1, the device 1 is overall in the form of a self-adhesive part that takes, in the example, the form of a self-adhesive pad, that can be positioned directly on the skin of the subject. In one embodiment that is not illustrated, the self-adhesive part is a self-adhesive dressing.

The device according to the invention comprises a fastening base 3 made of a biocompatible and adhesive flexible material; this base ensures that the complete device is held on the skin; the central part 4a of the base 3 is a circular recess where the first part of the device is positioned, which makes it possible to track the production of NO in the investigation zone of the skin of the subject. The circular recess 4a therefore enables the positioning of the first part of the measurement device directly on the skin 2 of the subject. The recess 4a may take another shape, for example chosen from ellipse, triangle, rectangle, square or polygon.

This first part comprises a fibrous body 4 which is attached to a sensing element 5 which it surmounts, as illustrated in FIG. 7, or which it envelopes, as illustrated in FIG. 8, to constitute the base of a stack. The fibrous body fulfills the function of conveying the sweat produced in the investigation zone to the sensing element 5 so that the nitric oxide dissolved therein is detected, then of discharging the sweat once the measurement has been carried out.

A filter 29 may optionally be arranged between the fibrous body 4 and the inlet(s) of the sensing element 5. The function of the filter 29 is to filter the sweat to prevent certain elements naturally contained therein from disrupting the measurement of the NO dissolved in the sweat. These interfering elements are for example peroxynitrite (ONOO⁻) or hydrogen peroxide (H₂O₂).

The sensing element 5 detects the NO by means of one or more electrochemical sensors 14, which will be defined below. The sensor sends its information to a converter 6a, which itself supplies a processor 6b, powered by an energy generator 6d associated with said sensing element 5. The processor 6b supplies a radiocommunication system 6c, which sends the information to instrumentation which is capable of converting this information into a graph such as the one depicted in FIG. 6.

In this FIG. 6, the portion constituting the measurement of the NO produced during the effort by the subject is the portion which is between points 11 and 12 of the graph. The whole of the graph of FIG. 6 between points 11 and 12 corresponds to one parameter. Depending on the value of this parameter, it is possible to link a pathology such as arteriosclerosis. It is also possible to accompany the management of a physiological function such as the monitoring of the bioavailability of alanine. Specifically, the natural precursor of NO in an organism is an amino acid called alanine. The human body can produce NO in response to an effort only within the limits of its store of alanine. Consequently, the device also makes it possible to predict the moment when the subject will no longer be able to manage his/her vasodilation, and therefore the risk of becoming injured.

All the components carrying out the various functions depicted in FIG. 4 are assembled together in an embedded electronics system, denoted by 6 in its entirety. The constituents 4, 5 and 6 form a stack, which is held on the skin of the subject by means of a flexible and watertight envelope of silicone type, denoted by 7 in its entirety.

The embedded electronics system of the component 6 carries out the functions of control of the members of the sensing element 5; it also comprises a gyroscopic and accelerometric unit in order to know the orientation and the movements of the subject and also the start and the end of the activity sequence of the subject, and a temperature sensor to measure the temperature of the skin. It is useful to know the temperature of the skin in order to be able to correlate the temperature and the dilation of the vessels.

The sensing element of the example described is electrochemical; the one depicted in FIG. 5 comprises an electrochemical sensor 14 and an insulating planar support 10 made of polyimide. The electrochemical sensor comprises two electrodes 8 and 9 positioned on one side of the insulating planar support 10 and between which is the sweat produced by the subject in the investigation zone, i.e. in line with the stack 4, 5, 6. In the sensing element depicted in FIG. 5, it is seen that there are four identical units each making it possible to obtain an NO measurement. Installing several sensing units advantageously makes it possible to obtain a cutaneous map of NO production within the zone covered.

With reference to FIG. 7, the fibrous body 4 and the sensing element 5 are arranged differently from FIG. 3. The insulating planar support 10 is positioned directly on the skin 2. The side of the support 10 provided with the electrochemical sensor is on the opposite side from the side against the skin 2. The fibrous body 4 has a portion in contact with the skin and a portion that covers the side of the support comprising the electrochemical sensor. In other words, the filter 4 straddles the skin and the electrochemical sensor. In this embodiment, the fibrous body comprises cotton or a nonwoven material.

With reference to FIG. 8, a second arrangement of the fibrous body 4 and of the sensing element 5 is illustrated. The fibrous body 4 sandwiches the sensing element. As a result, a portion of the fibrous body 4 is positioned against the skin.

Next the sensing element 5 is positioned on the fibrous body portion against the skin. The portion of the fibrous body 4 which is not positioned on the skin is folded back over the sensing element 5 thus covering the sensor.

According to a first embodiment, the electrochemical sensor 14 comprises three electrodes as illustrated schematically in FIG. 9: a reference electrode 20, a work electrode 21 and an auxiliary electrode 22. The reference electrode 20 is a silver chloride (AgCl) electrode, the auxiliary electrode 22 is a platinum (Pt) electrode and the work electrode 21 is an electrode based on platinum black. The work electrode 21 has the shape of the disk. This disk is partially surrounded by the reference and auxiliary electrodes, the reference electrode being opposite the auxiliary electrode. The dimensions of the electrochemical sensor are of the order of a millimeter.

According to a second embodiment illustrated in FIG. 10, the electronic sensor comprises a reference electrode 20, a work electrode 21 and an auxiliary electrode 22. The reference electrode 20 is a silver chloride (AgCl) electrode, the auxiliary electrode 22 is a platinum (Pt) electrode and the work electrode 21 is an electrode based on platinum black. The work electrode 21 has the shape of a disk. This disk is partially surrounded by the reference and auxiliary electrodes. The electrodes are arranged concentrically: the work electrode 21 is partially surrounded by the reference electrode 20, and the reference electrode 20 is itself surrounded by the auxiliary electrode 22. The dimensions of the electrochemical sensor are of the order of a millimeter.

The electrochemical sensor of FIG. 9 or 10 may be used in a microhydraulic circuit illustrated schematically in FIG. 11.

In FIG. 11, the fibrous body 4 absorbs the biological liquid, here sweat, and transports it to three microchannels 15 marked out in a planar support 10. These microchannels 15 will each convey the sweat to sensing units 16, 17, 18. In the example represented, there is one sensing unit per microchannel 15. The sensing unit 16 will detect nitric oxide, the sensing unit 17 will detect nitrite contained in the sweat, and the sensing unit 18 will detect hydrogen peroxide contained in the sweat. Nitrite is mainly produced in the cells by the reaction between superoxide oxygen (O2⁻*) and nitric oxide. The detection of NO2⁻ therefore makes it possible to have a better measurement of the NO concentration.

Thus, each sensing unit is devoted to the detection of a chemical species. Each sensing unit is electrically powered thus each sensing unit is at a potential imposed in order to carry out a stationary measurement. The sensing unit 18 is at the redox potential of hydrogen peroxide (oxidizing species) in order to detect hydrogen peroxide. The processing of the data from the sensing unit 18 will give the amount of H₂O₂. The sensing unit 16 is at the redox potential of NO (oxidizing species) in order to detect NO. Owing to the fact that the redox potential of H₂O₂ is lower than the redox potential of NO, the sensing unit 16 detects H₂O₂ as well as NO. The processing of the data from the sensing unit 18 will give the amount of H₂O₂ and NO taken together. The sensing unit 17 is at the redox potential of nitrite (oxidizing species) in order to detect NO. As the redox potential of NO₂⁻ is above the redox potential of H₂O₂ and NO, the unit 17 detects H₂O₂ and NO as well as NO2⁻. The processing of the data from the sensing unit 18 will give the amount of H₂O₂, NO and NO2⁻ taken together. Another subsequent processing of the data produced by the sensing units 16, 17, 18 makes it possible to determine, by the difference, the amounts of each of the chemical species, i.e. of NO, H₂O₂ and NO₂⁻.

Alternatively, use may be made of a pulse method, each sensing unit will then be capable of detecting each species. After processing of the data, the amount of each species present will be able to be determined.

With reference to FIG. 12, the sensing element 5 comprises three microchannels 30, 31, 32 marked out in the thickness of the insulating planar support 10. The sensing units 16, 17 and 18 are placed on each bottom wall of the microchannels 30, 31, 32. The sensing unit 16 is configured to detect nitric oxide, the sensing unit 17 is configured to detect nitrite contained in the sweat, and the sensing unit 18 is configured to detect hydrogen peroxide contained in the sweat. Each sensing unit 16, 17, 18 comprises three sensors 14. A filter 29 is placed on top of the insulating planar support. The filter covers the microchannels. Finally a fibrous body 4 is placed on the filter 29.

The fibrous body 4 absorbs the biological liquid, here sweat, and transports it to the three microchannels 30, 31, 32 by means of capillary forces. When the sweat drained by the fibrous body 4 arrives level with the microchannels, the sweat is filtered by the filter 29 to remove certain interfering elements, then it is transported by the microchannels 30, 31, 32 at least up to the sensing units 16, 17, 18. The sensors of the sensing unit 16 then detect the NO, the sensors of the sensing unit 17 detect the nitrite and the sensors of the sensing unit 18 detect the hydrogen peroxide.

In one embodiment that is not shown, when the sensing element comprises several sensing units, at least one of which is devoted to the detection of a chemical species other than NO, for example hydrogen peroxide, then the filter 29 can be eliminated.

The current intensities that are obtained with the device according to invention are between the picoampere and the milliampere range.

Although the invention has been described in connection with several particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described and also the combinations thereof provided that they fall within the scope of the invention.

The use of the verb “have”, “comprise” or “include” and the conjugated forms thereof do not exclude the presence of elements or steps other than those mentioned in a claim.

In the claims, any reference sign between parentheses should not be interpreted as a limitation of the claim.

Claims

1. A process for detecting, in a subject, an amount of NO produced by said subject in the course of a sequence of a predefined activity state, characterized in that an investigation zone of an epidermis (2) of said subject is chosen, the production of NO dissolved in a biological liquid originating from the epidermis is tracked therein, directly and continuously, by means of a device formed of a first part (4), borne by said investigation zone and held thereon in a leaktight manner, this first part (4) being attached to a sensing element (5), which carries out the detection of the NO by means of an electrochemical sensor (14), and that, owing to an energy generator associated with said sensing element (5), a signal is sent by said electrochemical sensor, the reading of which signal enables the desired detection.

2. The process as claimed in claim 1, characterized in that use is made of at least one electrochemical sensor, which provides the signal as a result of an electrochemical measurement taken using the biological liquid, produced by the subject in the investigation zone, as electrolyte between two work electrodes (8,9) borne by an insulating planar support (10).

3. The process as claimed in claim 2, characterized in that a reference electrode is connected to the two work electrodes (8,9).

4. The process as claimed in claim 2, characterized in that the electrochemical sensor comprises a plurality of electrochemical sensors, the signals of which are combined to improve the output signal.

5. The process as claimed in claim 2, characterized in that the pattern of the electrodes (8,9) relative to their support follows a Hilbert curve in order to improve the power of the output signal per unit area of the support (10).

6. The process as claimed in claim 2, characterized in that the measurements are carried out in line with orifices (13) provided in the planar support, which is in line with the conductive patterns of the electrodes (8,9).

7. The process as claimed in claim 2, characterized in that the electrodes consist of metal deposits, in particular deposits of silver (Ag), gold (Au), platinum (Pt), and platinum black, or graphene deposits doped by nanoparticles of silver (Ag) or of gold (Au), the nanoparticles being functionalized by binders of NO, in particular guanylyl-cyclase or porphyrins.

8. The process as claimed in claim 1, characterized in that the device further comprises a second part (6) positioned above the first part (4), the second part (6) containing electronics for receiving the raw measurements from the electrochemical sensor, converting them into an NO concentration and ensuring the transmission of the signal possibly with other parameters linked to the environment.

9. The process as claimed in claim 1, characterized in that the device carries out and transmits measurements at a frequency that is a function of the activity state of the subject, this state being tracked by means of a gyroscopic and/or accelerometric module of the second part (5) of the device.

10. A detection device (1) for detecting, in a subject, an amount of NO produced by said subject in the course of a sequence of a predefined activity state, said device comprising a first part (4) intended to be borne by an investigation zone of an epidermis (2) of said subject and held thereon in a leaktight manner in order to track, directly and continuously, the production of NO in a biological liquid originating from the epidermis, the first part being attached to a sensing element (5), which carries out the detection of NO by means of an electrochemical sensor (14), and a second part (6) configured to send, owing to an energy generator (5d) associated with said sensing element (5), a signal, the reading of which enables the desired detection.

11. The device as claimed in claim 10, characterized in that the sensing element provides the signal as a result of an electrochemical measurement taken using the biological liquid, produced by the subject in the investigation zone, as electrolyte between two work electrodes (8,9) borne by an insulating planar support (10).

12. The device as claimed in claim 11, characterized in that a reference electrode is connected to the two work electrodes.

13. The device as claimed in claim 11, characterized in that the insulating planar support (10) comprises at least one microchannel (15, 30, 31, 33) so as to guide the biological liquid to the electrochemical sensor (14).

14. The device as claimed in claim 10, characterized in that the sensing element comprises a plurality of similar electrochemical sensors, the signals of which are combined to improve the output signal.

15. The device as claimed in claim 11, characterized in that the pattern of the work electrodes (8,9) relative to their support (10) follows a Hilbert curve in order to improve the strength of the output signal per unit area of the support.

16. The device as claimed in claim 11, characterized in that the measurements are carried out in line with orifices (13) provided in the planar support (10), which is in line with the conductive patterns of the electrodes (8,9).

17. The device as claimed in claim 11, characterized in that the work electrodes (8,9) consist of metal deposits, in particular deposits of silver (Ag), gold (Au), platinum (Pt), and platinum black, or graphene deposits doped by nanoparticles of silver (Ag) or of gold (Au), the nanoparticles being functionalized by binders of NO, in particular guanylyl-cyclase or porphyrins.

18. The device as claimed in claim 10, characterized in that the sensing element comprises a plurality of electrochemical sensors (14) distributed in a plurality of sensing units (16, 17, 18), and in that each sensing unit is configured to detect at least one chemical species.

19. The device as claimed in claim 13 taken in combination, characterized in that the insulating planar support comprises a plurality of microchannels (30, 31, 32), and characterized in that each channel comprises a sensing unit.

20. The device as claimed in claim 10, characterized in that the first part comprises a fibrous body in order to convey the biological liquid from the investigation zone to the sensing element by means of capillary forces.

21. The device as claimed in claim 20, characterized in that the first part further comprises a filter (29) configured to filter the biological liquid at an inlet of the sensing element in order to avoid distorting the detection of NO by interfering elements contained in the biological liquid.

22. The device as claimed in claim 10, characterized in that the second part is positioned above the first part (4), the second part containing electronics for receiving the raw measurements from the electrochemical sensor, for converting them into an NO concentration and ensuring the transmission of the signal possibly with other parameters linked to the environment.

23. The device as claimed in claim 10, characterized in that the device comprises a gyroscopic and/or accelerometric module to detect the activity state of the subject and that the device is configured to carry out and transmit measurements at a frequency that is a function of the activity state of the subject.