WO2016037662A1

WO2016037662A1 - A helicobacter pylori sensor with ph sensor

Info

Publication number: WO2016037662A1
Application number: PCT/EP2014/069519
Authority: WO
Inventors: Patrick Fröse; Erhard Magori; Roland Pohle; Evamaria STÜTZ; Angelika Tawil; Oliver von Sicard
Original assignee: Siemens Aktiengesellschaft
Priority date: 2014-09-12
Filing date: 2014-09-12
Publication date: 2016-03-17

Abstract

A Helicobacter pylori sensor for analyzing a test sample for presence of Helicobacter pylori is presented. The test sample is analyzed by determining an extent of ammonia present in the test sample. The HBP sensor includes an ammonia sensor module and a pH sensor module. The ammonia sensor module determines an extent of ammonia present in the test sample. The ammonia sensor module includes a component having silver. The ammonia sensor module is adapted to determine ammonia by detecting an electrochemical reaction between ammonia and the component of the ammonia sensor module. The pH sensor module determines a pH of the test sample. Knowledge of pH is helpful for accurate interpretation of results for determining the extent of ammonia present in the test sample because the equilibrium between ammonia and ammonium ions is dependent on pH of the medium containing ammonia and ammonium ions.

Description

A HELICOBACTER PYLORI SENSOR WITH PH SENSOR This invention relates generally to a sensor for analyzing a test sample for presence of Helicobacter pylori and more par^¬ ticularly to a sensor for Helicobacter pylori with pH measurement . Helicobacter pylori (hereinafter referred to as, HBP) are rod-shaped bacteria, which can colonize the human stomach and are responsible for a number of gastrointestinal disorders. Besides other pathological conditions caused by HBP, the gas^¬ trointestinal disorders include peptic ulcers such as stomach ulcers and duodenal ulcers. In chronic conditions, HBP can also cause stomach cancer. The prevalence of HBP is about 50% worldwide. Therefore, an investigation of infection with HBP represents an integral part of the diagnosis of gastrointes^¬ tinal diseases.

In modern medicine, a HBP infection may, for example, be treated with eradication therapy, that involves simultaneous^¬ ly using a combination of different antibiotics. However, be^¬ fore such eradication therapy can be started, an exact diag- nosis is necessary.

For HBP detection, various direct and indirect detection methods are known, for example, non invasive testing can be performed with a blood antibody test, stool antigen test, urine ELISA test or with the carbon urea breath test (in which the patient drinks 14C—labeled urea or 13C-labeled urea, which the HBP metabolizes, producing labeled carbon di^¬ oxide that can be detected in the breath of the patient) . Another method for detecting H. pylori infection is the so called endoscopy or gastroscopy method. In this method, the investigator i.e. the gastroenterologist performs a biopsy on a tissue sample collected from the gastrointestinal tract of the test subject. The biopsy involves a rapid urease test, histological examinations, and microbial culture from the tissue sample. In rapid urease test, the biopsy sample is placed in a test medium. The test medium contains a nutrient solution for HBP, urea and an indicator such a phenol red. If HBP is present in the biopsy sample, the HBP produces urease that hydrolyzes urea to ammonia and carbon dioxide. In pres^¬ ence of ammonia the pH of the medium is raised and thus the color of the specimen changes from yellow (urease from HBP not present) to red (urease from HBP present) . However, all of these detection methods as well as other known methods have their drawbacks such as delay in getting test results, being unpleasant to the test subject i.e. the patient, and being expensive.

Another simple technique for detecting HBP is disclosed in WO2010094649 Al which attempts to provide an alternate to the above disclosed test methods. In WO2010094649 Al the inven^¬ tion relates to a diagnostic device comprising a first elec- trode which is produced of an acid-fast noble metal, and a second electrode which is produced of silver, the first elec^¬ trode and the second electrode being at least partially im^¬ mersed in a container which is filled with a nutrient solu^¬ tion and into which a tissue sample can be introduced. An electrical voltage can be applied between the first electrode and the second electrode and a change in an electric variable can be measured between the first electrode and the second electrode when ammonia is present. The diagnostic device ac^¬ cording to the invention allows the fast screening of a fresh tissue sample for Helicobacter pylori. The technique accord^¬ ing to the disclosure in WO2010094649 Al is a simple design and makes it possible to reliably detect Helicobacter pylori in a very short time. However, the Helicobacter pylori device of WO2010094649 Al has its drawbacks. Such a device when used to detect ammonia is based on the electrochemical reaction between functional- ized silver and ammonia in the medium. The rate of reaction is dependent on the amount of ammonia available in the medium which in turn is dependent on the pH of the medium, but the device of WO2010094649 Al does not account for this. There^¬ fore, the results obtained from the device of WO2010094649 Al are not accurately interpretable .

It is therefore an object of the present invention to provide a helicobacter pylori sensor with simple construction in which a result which can be accurately interpreted is ob- tained.

This object is achieved by a Helicobacter pylori sensor de^¬ scribed in claim 1 of the present technique. The dependent claims describe advantageous embodiments of the Helicobacter pylori sensor.

In accordance with an aspect of the present technique, a Hel^¬ icobacter pylori sensor (hereinafter, HBP sensor) for analyzing a test sample of a test subject for presence of Helico- bacter pylori is presented. The test sample is analyzed by determining an extent of ammonia present in the test sample. The HBP sensor includes an ammonia sensor module and a pH sensor module. The ammonia sensor module determines an extent of ammonia present in the test sample. The ammonia sensor module includes a component having silver. The ammonia sensor module is adapted to determine ammonia by detecting an elec^¬ trochemical reaction between ammonia and the component of the ammonia sensor module. The pH sensor module determines a pH of the test sample. Knowledge of pH is helpful for accurate interpretation of results for determining the extent of ammonia present in the test sample because the equilibrium be^¬ tween ammonia and ammonium ions is dependent on pH of the me^¬ dium containing ammonia and ammonium ions. In an embodiment of the HBP sensor the component comprises silver chloride (AgCl) . The electrochemical analysis of ammo^¬ nia in the test sample is based on a reaction between ammonia and AgCl . In cases where the component of the ammonia sensor module is without AgCl, the component needs to be functional- ized before analysis of the test sample. The advantage of this embodiment is that the need to functionalize the compo^¬ nent is at least partially obviated.

In another embodiment of the HBP sensor, the component is a layer for contacting the test sample to be analyzed. In this embodiment the ammonia sensor module further includes a first electrode and a second electrode. The first electrode is electrically connected to a first point on the layer and the second electrode is electrically connected to a second point on the layer. The first point and the second point are dis^¬ tinct from each other such that an electrical resistance or an electrical conductance of the layer between the first point and the second point is measurable. On contacting the layer with the test sample, the extent of ammonia present in the test sample is determinable by measuring a change in the electrical resistance or the electrical conductance of the layer between the first point and the second point of the layer. This provides a simple construction of the HBP sensor.

In another embodiment of the HBP sensor, the layer is limited between the first point and the second point. In this embodi^¬ ment, the layer of does not extend beyond the first point and the second point. This ensures that only the extent of layer necessary for measuring the electrical resistance or the electrical conductance between the first point and the second point is used in the HBP sensor. This makes the HBP sensor economical and also miniaturized.

In another embodiment of the HBP sensor, the first electrode and the second electrode are interdigitated electrodes. This ensures increased contact between the layer and the first and the second electrodes and hence makes the HBP sensor more sensitive.

In another embodiment of the HBP sensor, the first electrode and the second electrode are inert electrodes with respect to ammonia and/or hydrochloric acid. Thus, the first and the se^¬ cond electrodes do not chemically react with hydrochloric ac^¬ id and/or ammonia and thus the measurements made by the HBP sensor are more accurate as they represent measurements re- suiting from a reaction between ammonia and the layer only.

In another embodiment of the HBP sensor, the component is a working electrode for contacting the test sample to be ana^¬ lyzed. In this embodiment the ammonia sensor module includes a reference electrode formed of a material chemically inert to acid. The working electrode and the reference electrode are arranged such that an electrical potential or an electri^¬ cal current at the working electrode is measurable. On con^¬ tacting the working electrode with the test sample, the ex- tent of ammonia present in the test sample is determinable by measuring a change in the electrical potential or the elec^¬ trical current at the working electrode. This provides anoth^¬ er simple construction of the HBP sensor. In another embodiment of the HBP sensor the material chemi^¬ cally inert to acid is a noble metal. The noble metals are readily available and thus the HBP sensor is easy to fabri^¬ cate . In another embodiment of the HBP sensor, the pH sensor module comprises a pH sensing element adapted to perform potentiom- etric measurement of pH. The potentiometric measurement of pH provides an accurate measurement and specific result of pH of the test sample as compared to color based pH sensors.

In another embodiment of the HBP sensor, the pH sensing element is an ion-selective electrode. The ion-selective elec^¬ trodes are readily available and economical. Moreover, in this embodiment the HBP sensor is fabricated as a three elec- trode system which is compact and easy to use.

In another embodiment of the HBP sensor, the pH sensing element is an ISFET (ion-sensitive field-effect transistor) . The ISFET are readily available, economical and easy to use.

Moreover, owing to their small sizes in this embodiment the HBP sensor is fabricated as miniaturized and compact arrange^¬ ment .

In another embodiment of the present technique, the HBP sen^¬ sor includes a housing for protecting the ammonia sensor module. The ammonia sensor module is positioned inside the hous^¬ ing such that the ammonia sensor module except the component of the ammonia sensor module is hermetically sealed from the test sample. Thus, no other part of the ammonia sensor module except the component reacts with the test sample, and this ensures accuracy of the measurements. Moreover, because of the housing the longevity of the ammonia sensor module and consequently of the HBP sensor is increased.

In another embodiment of the HBP sensor, the pH sensor module is positioned inside the housing such that the pH sensor mod^¬ ule except the pH sensing element of the pH sensor module is hermetically sealed from the test sample. Thus, no other part of the pH sensor module except the pH sensing element inter^¬ acts with the test sample, and this ensures accuracy of the measurements. Moreover, because of the housing the longevity of the pH sensor module and consequently of the HBP sensor is increased.

In another embodiment of the HBP sensor, the housing is made of a material inert to the test sample to be analyzed with respect to ammonia and hydrochloric acid. Thus, the housing does not react with any ingredients of the test sample and this ensures accuracy of the measurements of extent of ammo^¬ nia as well as of pH. Moreover, the longevity of the HBP sen^¬ sor is increased. It may be noted that by using the present technique a pres^¬ ence or absence of the ammonia in the test sample, and ac^¬ cordingly the presence or absence of HBP in the test sample, may be detected. Furthermore, in test samples where the ammo- nia is found or detected to be present, an extent of ammonia present i.e. an amount of ammonia present in the test sample may be determined which leads to determination of an amount of the HBP present in the test sample.

The present technique is further described hereinafter with reference to illustrated embodiments shown in the accompany^¬ ing drawings, in which: is a schematic representation of an exemplary embodiment of a Helicobacter pylori sensor in accordance with aspects of the present technique; is a schematic representation of another exemplary embodiment of the Helicobacter pylori sensor; is a schematic representation of yet another exemplary embodiment of the Helicobacter pylori sensor; is a schematic representation of another exemplary embodiment of the Helicobacter pylori sensor depicting interdigitated electrodes; and is a schematic representation of yet another exemplary embodiment of the Helicobacter pylori sensor depicting a multi electrode system, in accordance with aspects of the present technique.

Hereinafter, above-mentioned and other features of the pre- sent technique are described in details. Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of ex^¬ planation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodi^¬ ments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details.

The basic principle of the detection of Helicobacter pylori (hereinafter HBP) is based on detecting the presence or absence of ammonia (N¾) in the test sample. HBP characteristi^¬ cally produces bacterial urease, an enzyme that catalyzes the hydrolysis of urea [( H₂)₂CO] into carbon dioxide (C0₂) and ammonia as shown in the following chemical equation:

(NH₂)₂CO + H₂0 → C0₂ + 2NH₃

Ammonia is not present under normal circumstances in a hollow organ of the gastrointestinal tract (hereinafter, GI tract) such as the stomach. Even if present, ammonia is present only in insignificantly small amounts. However, in test samples or in test subjects i.e. patients suffering from HBP infection the amount of ammonia present in the GI tract or in the test culture to which the test sample is added is significantly increased due to the bacterial urease produced by HBP. Thus, determining an extent of ammonia present in the test sample is a definitive conclusion of the presence of HBP.

Detection of ammonia is performed using silver chloride

(AgCl) . Ammonia in aqueous state reacts with AgCl in solid state to form a readily water soluble silver diamine complex as per the following chemical equation:

AgCl(s) + 2NH₃(aq) → [Ag (NH₃) ₂] ⁺ (aq) + Cl^"(aq)

This results in a loss of silver chloride by dissolution into the test sample. This loss of silver chloride is detected to conclude the presence of ammonia which in turn is definitive^¬ ly used to conclude a presence of bacterial urease and final conclusion is presence of HBP.

The above described principle of determining presence of HBP is used in the present technique. FIG 1 schematically represents an exemplary embodiment of a Helicobacter pylori sensor 100 in accordance with aspects of the present technique.

The Helicobacter pylori sensor 100 (hereinafter HBP sensor 100) is used for analyzing a test sample of a test subject for presence of HBP in the test sample. As mentioned above, the presence of HBP is analyzed by determining an extent of ammonia present in the test sample.

For the purposes of the present technique, the term "analyz^¬ ing" or like terms, as used herein, means probing, checking, evaluating, testing, scrutinizing or examining the test sam- pie. The phrase "analyzing the test sample for presence of Helicobacter pylori" means analyzing the test sample to determine or detect a presence of HBP and may optionally in^¬ clude quantifying HBP in the test sample. The "test sample", as used herein, means and includes an in vivo sample or in vitro sample. For probing the test sample in vivo, the HBP sensor 100 is required to be introduced in^¬ side the body of the test subject i.e. the patient. This can be achieved by integrating the HBP sensor 100 with a suitable invasive device such as a gastroscope, an endoscope, an en^¬ doscopy capsule, a biopsy catheter, so on and so forth. An example of the test sample, in vivo, may be, but not limited to, gastric juice within the stomach of the test subject or contents or mediums within other parts of the GI tract. For probing the test sample in vitro, the test sample may be a biological specimen collected from the test subject for exam^¬ ple a specimen of the gastric juice of the test subject. The test sample, in vitro, may also include test sample prepared with additives such as a suitable test buffer or water for dilution.

The phrase "extent of ammonia", as used herein means, the ab^¬ sence or presence of ammonia i.e. zero amount of ammonia or non-zero amount of ammonia. Furthermore, the phrase "extent of ammonia", when in non-zero amount i.e. when ammonia is present, includes the quantitative assessment of the ammonia present .

Now referring to FIG 1, the HBP sensor 100 includes an ammo^¬ nia sensor module 110 and a pH sensor module 120. The ammonia sensor module 110 determines an extent of ammonia present in the test sample. The ammonia sensor module 110 includes a component 5 having silver. The ammonia sensor module 110 is adapted to determine ammonia by detecting an electrochemical reaction between ammonia and the component 5 of the ammonia sensor module 110. In embodiments where the component 5 having silver is formed solely of silver, then there is a need to functionalize the component 5 by changing some of the silver to silver chloride or by coating the component 5 with a layer of silver chloride. The component 5 having silver is functionalized by use of hydrochloric acid to convert at least some of the silver in the component 5 to silver chloride. The functionalization may be achieved before contacting the component 5 with the test sample, for example by dipping or spraying the component 5 having silver with hydrochloric acid, or may be achieved after contacting the component 5 with the test sample by the chloride ions present in the test sample. If the test sample is gastric juice, in vivo or in vitro, it contains hydrochlo^¬ ric acid which helps to functionalize the component 5. In certain other embodiments of the HBP sensor 100 the component 5 comprises silver chloride (AgCl) . Thus, the need to func- tionalize the component 5 is at least partially obviated. The pH sensor module 120 determines a pH of the test sample.

As shown in FIG 2, in another embodiment of the HBP sensor 100, the component 5 is a layer 10. The layer 10 is for con^¬ tacting the test sample to be analyzed. The HBP sensor 100 also includes a first electrode 20 and a second electrode 30. When the HBP sensor 100 is contacted with the test sample, an outer face 12 of the layer 10 of silver chloride comes in contact with the test sample. As is depicted in FIG 2, the first electrode 20 and the second electrode 30 are positioned in the HBP sensor 100 in such a way that the first electrode 20 and the second electrode 30 do not contact the test sam^¬ ple, even when the layer 10 of the HBP sensor 100 is in contact with the test sample. One example of such a construction of the HBP sensor 100 is depicted in FIG 1 where the first electrode 20 and the second electrode 30 are positioned on an inner face 14 of the layer 10.

In another embodiment of the HBP sensor 100, the first and the second electrode 20, 30 are constituted of a material that is inert to ammonia and/or hydrochloric acid and/or oth^¬ er contents of the test sample. In this embodiment, even if the test sample comes in contact with the first and the se^¬ cond electrode 20, 30, there is no reaction between the first and the second electrode 20, 30 with ammonia and/or hydro^¬ chloric acid and/or other contents of the test sample. In an exemplary embodiment of the HBP sensor 100, the first elec^¬ trode 20 is made of inert elements or inert metallic com^¬ pounds such as Gold (Au) , Platinum (Pt) , and so on and so forth, and similarly the second electrode 20 is made of inert elements or inert metallic compounds such as Gold (Au) , Plat^¬ inum (Pt) , and so on and so forth.

The first electrode 20 is electrically connected to a first point 22 on the layer 10. The second electrode 30 is electri^¬ cally connected to a second point 32 on the layer 10. The first point 22 and the second point 32 are regions or areas or volume of the layer 10 where the first electrode 20 and the second electrode 30 are electrically connected. Electri^¬ cal connection of the first and the second electrodes 20, 30 with the first and the second point 22, 32, respectively may be established by physically connecting the first and the se^¬ cond electrodes 20, 30 to the first and the second point 22, 32, for example by riveting, welding, brazing, soldering, and so on and so forth. The first point 22 and the second point 32 are distinct from each other such that an electrical re^¬ sistance or an electrical conductance of the layer 10 of sil^¬ ver chloride between the first point 22 and the second point 32 is measurable. The first and the second electrodes 20, 30 may have various shapes and configurations for example the first and the second electrodes 20, 30 may be simple wire electrodes or stick electrodes. In an exemplary embodiment of the HBP sensor 100, as depicted in FIG 4, the first and the second electrodes 20, 30 are interdigitated electrodes.

Hereinafter, for the purposes of the present disclosure only the term "electrical resistance" has been used, however, as may be appreciated by a person skilled in the art of electri^¬ cal sciences, from knowledge of the electrical resistance of the layer 10, the electrical conductance can be easily calcu^¬ lated. Thus the phrase "electrical resistance", hereinafter is meant to mean "electrical resistance or electrical con^¬ ductance" . In the HBP sensor 100, on contacting the layer 10 with the test sample, the extent of ammonia present in the test sample is determined by measuring a change in the electrical re^¬ sistance of the layer 10 between the first point 22 and the second point 32 of the layer 10. Since, the first electrode 20 and the second electrode 30 do not participate in the re^¬ action with ammonia, either due to being sealed off from the test sample or due to being constituted with inert material or a combination thereof, the change in the electrical re^¬ sistance measured at the first and the second electrodes 20, 30 is solely due to the reaction of ammonia with the layer

10. As may be appreciated by one skilled in the art, the lay^¬ er 10 is either made of silver and/or silver chloride. When the layer 10 is made of silver it needs to be functionalized i.e. at least some silver chloride needs to be present in the layer 10.

In the HBP sensor 100, the electrical resistance of the layer 10 between the first and the second point 22, 32 may be meas- ured by known techniques, such as completing the electrical circuit between the first and the second point 22, 32 via the first and the second electrodes 20, 30 and measuring the electrical resistance for example by using a micro-ohmmeter or ohmmeter in the completed electrical circuit.

When the HBP sensor 100 is used, i.e. when the layer 10 is contacted with the test sample, the electrical resistance is measured at one or more time intervals, and this may be com- pared to a reference value of electrical resistance for the layer 10. The reference value of electrical resistance for the layer 10 is the value of electrical resistance of the layer 10 between the first and the second points 22, 32 when the layer 10 is contacted to a reference sample, i.e. a sam- pie with same or similar constitution as the test sample but without any ammonia. An example of reference sample may be gastric juice from a healthy individual who is known to be not affected by HBP. When the layer 10 is in contact with the test sample that contains ammonia, a reaction, as described hereinabove, will take place resulting into, starting from a partial loss to a complete loss of the layer 10 depending upon the amount or extent of ammonia present in the test sample and/or duration of contact between the layer 10 and the test sample.

Thus, by measuring the change in electrical resistance of the layer 10 between the first point 22 and the second point 32, the loss of the layer 10 is detected and thus a presence of ammonia is concluded. From the different measurement values of the electrical resistance at different time intervals, a rate of change of electrical resistance is determined from which a quantitative assessment of the ammonia present in the test sample is made.

When being used in vivo, the HBP sensor 100 may be used at one location in the GI tract or may be moved to make measure^¬ ments of change of electrical resistance at multiple loca- tions. When moved to a new location in the GI tract, the ref^¬ erence value of electrical resistance at the new location will be electrical resistance of the layer 10 between the first and the second point 22, 32 measured at the new loca- tion at the instance of arrival of the HBP sensor 100 at the new location. Subsequent measurements of the electrical re^¬ sistance at the new location made at subsequent time instanc^¬ es are used to determine whether ammonia is present or not at the new location. With the help of the subsequent measure- ments of the electrical resistance at the new location, a rate of change in the electrical resistance at the new loca^¬ tion is determined which is used to determined the extent of ammonia present at the new location. FIG 3 is a schematic representation of another exemplary embodiment of the HBP sensor 100. As is clearly understood by a comparison of FIG 2 and FIG 3, in an exemplary embodiment of the HBP sensor 100, the layer 10, as shown in FIG 2, may physically extend beyond the first and second point 22, 32. This ensures that the first and the second electrodes 20, 30 are properly shielded by the layer 10 from the test sample, whereas in another exemplary embodiment of the HBP sensor 100, the layer 10, as shown in FIG 3, is physically limited between the first and second point 22, 32 i.e. the layer 10 does not extend beyond the first and the second points 22, 32. This ensures that lesser quantity of silver is required for the fabrication of the layer 10, thereby making the HBP sensor 100 cost effective and compact. As shown in FIG 4, in another embodiment of the HBP sensor

100, the component 5 is a working electrode 50 for contacting the test sample to be analyzed. As may be appreciated by one skilled in the art, the working electrode 50 is either made of silver and/or silver chloride. When the working electrode 50 is made of silver it needs to be functionalized i.e. at least some silver chloride needs to be present in the working electrode 50. In this embodiment the ammonia sensor module 110 includes a reference electrode 60 formed of a material chemically inert to acid. The working electrode 50 and the reference electrode 60 are arranged such that an electrical potential or an electrical current at the working electrode 50 is measurable. On contacting the working electrode 50 with the test sample, the extent of ammonia present in the test sample is determinable by measuring a change in the electri^¬ cal potential or the electrical current at the working elec^¬ trode 50. In the HBP sensor 100 the material chemically inert to acid is a noble metal for example Platinum (Pt) and Gold (Au) .

Referring to FIGs 1 to 5, the pH sensor module 120 has been explained hereinafter. In the HBP sensor 100, the pH sensor module 120 comprises a pH sensing element 122 adapted to per- form potentiometric measurement of pH of the test medium. The potentiometric measurement of pH provides an accurate meas^¬ urement and specific result of pH of the test sample. In one embodiment of the HBP sensor 100, the pH sensing element 122 is an ion-selective electrode. In another embodiment of the HBP sensor 100, the pH sensing element 122 is an ISFET (ion- sensitive field-effect transistor) . The construct of ion- selective electrode and ISFET and their principle of opera^¬ tion are well known in the art of electrochemistry and thus have not been explained in details herein for sake of brevi- ty.

In the present technique, the rate of change of the electri^¬ cal property i.e. electrical resistance and/or electrical conductance and/or electrical potential and/or an electrical current as determined by the ammonia sensor module 110 is used to calculate the extent of ammonia present in the test sample by using reference curves. The reference curves repre^¬ sent, for a given component 5 of known dimensions, different rate of change of the electrical property at different pH values of a standard sample and correlation between these different rate of change at different pH values with the amount or concentration or extent of ammonia present in the standard sample. Similarly, the amount or concentration or extent of ammonia present in the test sample may be used to calculate the quantity of HBP present in the test sample by using reference curves representing the extent of ammonia and its correlation to the quantity of HBP present for standard samples. The technique of using such reference curves is well known and pervasively used in the art of analytical chemistry and physics and thus the same has not been described herein for sake of brevity. As shown in FIGs 1, 2, 3 and 5, the HBP sensor 100 further includes a housing 40 for protecting the ammonia sensor module 110. The ammonia sensor module 110 is positioned inside the housing such that the ammonia sensor module 110 except the component 5 of the ammonia sensor module 110 is hermeti- cally sealed from the test sample. Thus, no other part of the ammonia sensor module 110 except the component 5 reacts with the test sample. In the embodiment where the component 5 is the layer 10, as depicted in FIGs 2 and 3, the the first electrode 20 and the second electrode 30 are positioned in- side the housing 40 and only the layer 10 is adapted to be exposed to the test sample when desired by an operator. Thus, the housing 40 is used to seal off the first and the second electrodes 20, 30 from the test sample when the HBP sensor 100 is used with the test sample, in vitro or in vivo. The housing 40 is made of a material inert to the test sample to be analyzed. In general for suitability of the HBP sensor 100 to be used in vivo, the housing 40 is preferably made of a material inert to gastric juice of the test subject. Examples of the material used to make the housing 40, may be, but not limited to, plastics, inert polymers, and so on and so forth.

In another embodiment of the HBP sensor 100, the pH sensor module 120 is positioned inside the housing 40 such that the pH sensor module 120 except the pH sensing element 122 of the pH sensor module 120 is hermetically sealed from the test sample. Thus, no other part of the pH sensor module 120 ex^¬ cept the pH sensing element 122 interacts with the test sam^¬ ple . While the present technique has been described in detail with reference to certain embodiments, it should be appreciated that the present technique is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves, to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Claims

Patent claims

1. A Helicobacter pylori sensor (100) for analyzing a test sample of a test subject for presence of Helicobacter pylori by determining an extent of ammonia present in the test sam^¬ ple, the Helicobacter pylori sensor (100) comprising:

- an ammonia sensor module (110) for determining an extent of ammonia present in the test sample, wherein the ammonia sensor module (110) comprises a component (5) having silver and is adapted to determine ammonia by detecting an elec^¬ trochemical reaction between ammonia and the component (5) , and

- a pH sensor module (120) for determining a pH of the test sample .

2. The Helicobacter pylori sensor (100) according to claim 1 wherein the component (5) comprises silver chloride.

3. The Helicobacter pylori sensor (100) according to claim 1 or 2 wherein the component (5) is a layer (10) for contacting the test sample to be analyzed and wherein the ammonia sensor module (110) comprises:

- a first electrode (20) electrically connected to a first point (22) on the layer (10), and

- a second electrode (30) electrically connected to a second point (32) on the layer (10), wherein the first point (22) and the second point (32) are distinct from each other such that an electrical resistance or an electrical conductance of the layer (10) between the first point (22) and the se- cond point (32) is measurable,

wherein, on contacting the layer (10) with the test sample, the extent of ammonia present in the test sample is determi^¬ nable by measuring a change in the electrical resistance or the electrical conductance of the layer (10) between the first point (22) and the second point (32) of the layer (10) .

4. The Helicobacter pylori sensor (100) according to claim 3, wherein the layer (10) is limited between the first point (22) and the second point (32) .

5. The Helicobacter pylori sensor (100) according to claim 3 or 4, wherein the first electrode (20) and the second elec^¬ trode (30) are interdigitated electrodes.

6. The Helicobacter pylori sensor (100) according to any of claims 3 to 5, wherein the first electrode (20) and the se^¬ cond electrode (30) are inert electrodes with respect to am^¬ monia and/or hydrochloric acid.

7. The Helicobacter pylori sensor (100) according to claim 1 or 2, wherein the component (5) is a working electrode (50) for contacting the test sample to be analyzed and wherein the ammonia sensor module (110) comprises a reference electrode (60) formed of a material chemically inert to acid, wherein the working electrode (50) and the reference electrode (60) are arranged such that an electrical potential or an electri^¬ cal current at the working electrode is measurable and where^¬ in, on contacting the working electrode (50) with the test sample, the extent of ammonia present in the test sample is determinable by measuring a change in the electrical poten- tial or the electrical current at the working electrode (50) .

8. The Helicobacter pylori sensor (100) according to claim 7, wherein the material chemically inert to acid is a noble met^¬ al .

9. The Helicobacter pylori sensor (100) according to any of claims 1 to 8, wherein the pH sensor module (120) comprises a pH sensing element (122) adapted to perform potentiometric measurement of pH.

10. The Helicobacter pylori sensor (100) according to claim 9, wherein the pH sensing element (122) is an ion-selective electrode .

11. The Helicobacter pylori sensor (100) according to claim 9, wherein the pH sensing element is an ISFET.

12. The Helicobacter pylori sensor (100) according to any of claims 1 to 11, further comprising a housing (40) for protecting the ammonia sensor module (110), wherein the ammonia sensor module (110) is positioned inside the housing (40) such that the ammonia sensor module (110) except the compo- nent (5) of the ammonia sensor module (110) is hermetically sealed from the test sample.

13. The Helicobacter pylori sensor (100) according to claim

12, wherein the pH sensor module (120) is positioned inside the housing (40) such that the pH sensor module (120) except the pH sensing element (122) of the pH sensor module (120) is hermetically sealed from the test sample.

14. The Helicobacter pylori sensor (100) according to claim 12 or 13, wherein the housing (40) is made of a material in^¬ ert to the test sample to be analyzed with respect to ammonia and hydrochloric acid.