WO2016045700A1

WO2016045700A1 - A helicobacter pylori sensor using optical sensing

Info

Publication number: WO2016045700A1
Application number: PCT/EP2014/070230
Authority: WO
Inventors: Patrick Fröse; Erhard Magori; Roland Pohle; Angelika Tawil; Oliver von Sicard
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2014-09-23
Filing date: 2014-09-23
Publication date: 2016-03-31
Anticipated expiration: 2017-03-23

Abstract

The present technique describes a Helicobacter pylori sensor and a method for analyzing a test sample for presence of Helicobacter pylori by determining an extent of ammonia present in the test sample. The Helicobacter pylori sensor includes an optical source, a stack of alternating first and second layers arranged to receive the light emitted by the optical source and a detector for detecting the light after being reflected from the stack of alternating layers. The first layer includes silver chloride and the second layer includes a material which is soluble in the test sample. On contacting the stack of alternating layers with the test sample, the extent of ammonia present in the test sample is determinable by measuring an intensity of the light detected.

Description

A Helicobacter pylori sensor using optical sensing This invention relates generally to a sensor for analyzing a test sample for presence of Helicobacter pylori and more particularly to a sensor for Helicobacter pylori using optical sensing. 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 gastrointestinal 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 gastrointestinal diseases.

In modern medicine, a HBP infection may, for example, be treated with eradication therapy, that involves

simultaneously using a combination of different antibiotics. However, before such eradication therapy can be started, an exact diagnosis 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 dioxide 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 presence 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 technique for examination of the stomach to detect a settlement of HBP is disclosed in WO2010108759 Al which attempts to provide an alternate to the above disclosed test methods. WO2010108759 Al presents a Helicobacter pylori sensor. The Helicobacter pylori sensor comprises a slide with a measuring area, a first electrode made of a precious metal which cannot be attacked by hydrochloric acid, and a second electrode which is made of silver and has a silver chloride layer, wherein the first electrode and the second electrode extend at least partially into the measuring area, and a change in an electrical variable can be measured when the measuring area and the two electrodes are at least partially wetted with a measurement solution and when ammonia is present in the measurement solution between the first

electrode and the second electrode. The Helicobacter pylori sensor according to the disclosure in WO2010108759 Al is compact and of simple design and makes it possible to

reliably detect Helicobacter pylori in a very short time. However, the Helicobacter pylori sensor of WO2010108759 Al has its drawbacks. Such a sensor when used in vivo and or in vitro will result in loss of one of the electrode i.e. the AgCl/Ag electrode and will be ruined for future usage. Fabricating the lost electrode sensor with all its proper electrical connections in a ruined sensor will be cumbersome. This will necessitate replacement of the entire sensor. Thus, the above mentioned techniques for detection of HBP are based on complex chemical tests and/or electrical parameters that need sophisticated electrical sensors and complex and very careful handling of the electrical sensors to make measurements. Moreover, there is exists a possibility of electrical interference in the test results from other undesired electrochemical activities at the electrodes. Thus, there exists a need for a simple technique of detection which is not based on chemical or electrical sensing mechanisms. It is therefore an object of the present invention to provide a technique of determining Helicobacter pylori using optical sensing .

This object is achieved by a Helicobacter pylori sensor described in claim 1 and by the method described in claim 13. The dependent claims describe advantageous embodiments of the Helicobacter pylori sensor and the method.

According to an aspect of the present technique a

Helicobacter pylori sensor (hereinafter, HBP sensor) for analyzing a test sample for presence of Helicobacter pylori is presented. The presence of Helicobacter pylori in the test sample is performed by determining an extent of ammonia present in the test sample. The Helicobacter pylori sensor includes an optical source, a stack of alternating first and second layers and a detector. The optical source is adapted to emit light towards the stack of alternating layers. In the stack of alternating first and second layers, the first layer includes silver chloride (AgCl) and the second layer includes a material which is soluble in the test sample. The stack of alternating layers in the HBP sensor is arranged to receive the light emitted by the optical source. The light emitted by the optical source is reflected by the stack of alternating layers. The detector is arranged for detecting the light after being reflected from the stack of alternating layers.

On contacting the stack of alternating layers with the test sample, the extent of ammonia present in the test sample is determinable by measuring an intensity of the light detected by the detector. The intensity of light detected by the detector depends on the number of first and the second layers forming the stack. When ammonia is present in the test sample, the AgCl of the first layer forms soluble silver diamine complex and thus gets dissolved in the test sample exposing an underlying second layer which is subsequently dissolved in the test sample exposing a new first layer which in turn gets dissolved. Thus, if ammonia is present in the test sample, the number of the first and the second layers forming the stack gets reduced and this has an effect on properties of the light reflected from the stack of

alternating layers for example the intensity of the reflected light is changed. This change in properties of the light reflected from the stack of alternating layers is detected by the detector.

From the change observed in the properties of the light reflected from the stack of alternating layers, the number of the layers in the stack after contacting the test sample is determined as compared to the number of the layers in the stack before contacting the test sample. The change in the number of layers indicates presence of ammonia in the test sample which in turn indicates presence of Helicobacter pylori in the test sample. Furthermore, a rate of change in the number of layers in the stack after contacting the test sample indicates the extent of ammonia present in the test sample which in turn indicates concentration of Helicobacter pylori in the test sample.

In an embodiment of the HBP sensor, the optical source is a Light-emitting diode (LED) . Use of LED enables selection of specific wavelengths of the light provided by the optical source and thus measurement at the detector for one or more specific wavelengths is easily performed without interference or noise from the other undesired wavelengths of light.

Moreover, LED is a readily available, economical and compact optical source and thus the HBP sensor when fabricated using the LED is easy to manufacture, inexpensive and compact.

In another embodiment of the HBP sensor, the optical source is a Laser diode. Use of LED enables selection of specific wavelengths of the light provided by the optical source and thus measurement at the detector for one or more specific wavelengths is easily performed without interference or noise from the other undesired wavelengths. Moreover, the Laser diode is readily available, economical and compact optical source and thus the HBP sensor fabricated using the Laser diode is easy to manufacture, inexpensive and compact.

In another embodiment of the HBP sensor, the optical source is a broadband source. Thus a broad range of wavelengths are present in the light provided by the optical source and measurement at the detector for one or more specific

wavelengths is easily performed.

In another embodiment of the HBP sensor, the detector is a photodiode. The photodiode is a readily available, economical and compact detector and thus the HBP sensor fabricated using the photodiode is easy to manufacture, inexpensive and compact . In another embodiment of the HBP sensor, the detector is a spectrophotometer. The spectrophotometer provides detection of intensities of reflected light over a wide spectrum and thus the HBP sensor can be used with different wavelengths of light emitted from the optical source. Moreover, the

spectrophotometer is readily available and its working is well known thus the HBP sensor fabricated using the

spectrophotometer is easy to manufacture, and simple to use for detection of the light reflected from the stack of alternating layers.

In another embodiment of the HBP sensor, the material of the second layer is cellulose. Cellulose is an organic compound and is biocompatible, and this makes the in-vivo use of the HBP sensor safe and simple. Moreover, since cellulose is readily available the HBP sensor fabricated using the

cellulose is easy to manufacture and inexpensive.

In another embodiment of the HBP sensor, the material of the second layer is gelatin. Gelatin is an organic compound and is biocompatible, and this makes the in-vivo use of the HBP sensor safe and simple. Moreover, since gelatin is readily available the HBP sensor fabricated using the gelatin is easy to manufacture and inexpensive.

In another embodiment of the HBP sensor, the material of the second layer is glass dissolvable in hydrochloric acid. This provides an alternative embodiment of the HBP sensor for in- vitro use of the HBP sensor. Fabricating of glass sheets and layers is simple and thus achieving any desired dimensions of second layers is simple and easy. In another embodiment the HBP sensor includes a housing. The stack of alternating layers is positioned inside the housing such that the stack of alternating layers is adapted to contact the test sample only at one end of the stack. The material of the housing is inert to the test sample to be analyzed with respect to hydrochloric acid and/or ammonia. The housing ensures controlled exposure of the stack of alternating layers to the test sample. Thus the layers of the stack are exposed sequentially and in a controlled manner which ensures accuracy of the HBP sensor.

In another embodiment the HBP sensor, the optical source is positioned inside the housing. Thus the optical source is protected against the test sample. In another embodiment the HBP sensor, the detector is

positioned inside the housing. Thus the detector is protected against the test sample.

According to another aspect of the present technique, a method for analyzing a test sample for presence of

Helicobacter pylori is presented. The method uses a HBP sensor according to the previous aspect of the present technique. The presence of Helicobacter pylori in the test sample is performed by determining an extent of ammonia present in the test sample. In the method, the stack of alternating layers of the HBP sensor is contacted with the test sample to be analyzed and light from the optical source is directed towards the stack of alternating layers of the

HBP sensor after or during the contact of the stack of layers with the test sample. Subsequently, the light from the optical source after being reflected from the stack of layers is detected. Finally, from intensity of the light detected, the extent of ammonia present in the test sample is

calculated .

As aforementioned, the intensity of light detected depends on the number of layers forming the stack. When ammonia is present in the test sample, the first layer of the HBP sensor gets dissolved in the test sample exposing an underlying second layer which is subsequently dissolved in the test sample exposing a new first layer which in turn gets

dissolved, and so on and so forth. Thus, if ammonia is present in the test sample, the number of the layers forming the stack gets continuously reduced and this changes

properties of the light reflected from the stack of

alternating layers for example the intensity of the reflected light is changed. This change in properties of the reflected light detected indicates the number of the layers present or remaining in the stack after contacting the test sample as compared to the number of the layers in the stack before contacting the test sample. The change in the number of layers indicates presence of ammonia in the test sample which in turn indicates presence of Helicobacter pylori in the test sample. Furthermore, a rate of change in the number of layers in the stack after contacting the test sample indicates the extent of ammonia present in the test sample which in turn indicates concentration of Helicobacter pylori in the test sample .

In an embodiment of the method of the present technique, the light directed from the optical source towards the stack of alternating layers is a broadband light. Thus a broad range of wavelengths are present in the light and determination of changes in properties of the reflected light for one or more specific wavelengths is easily performed.

In another embodiment of the method of the present technique, the light directed from the optical source towards the stack of alternating layers is a light of predetermined wave length. Thus determination of changes in properties of the reflected light for the predetermined wavelength is easily performed without interference or noise from the other undesired wavelengths of light.

It may be noted that by using the present technique a

presence or absence of the ammonia in the test sample, and accordingly the presence or absence of HBP in the test sample, may be detected. Furthermore, in test samples where the ammonia 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

accompanying drawings, in which: FIG 1 is a schematic representation of an exemplary embodiment of a Helicobacter pylori sensor in accordance with aspects of the present technique; FIG 2 is a schematic representation of another exemplary embodiment of the Helicobacter pylori sensor;

FIG 3 is an exemplary graph used for determining an

extent of ammonia in the test sample by the

Helicobacter pylori sensor; and

FIG 4 is a flow chart illustrating a method for analyzing a test sample of a test subject for presence of Helicobacter pylori, in accordance with aspects of the present technique.

Hereinafter, above-mentioned and other features of the present 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 explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. 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 (NH₃) in the test sample. HBP

characteristically 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 optically detected to conclude the presence of ammonia which in turn is definitively 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 "analyzing" or like terms, as used herein, means probing, checking, evaluating, testing, scrutinizing or examining the test sample. 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 include 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 inside 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 endoscopy 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 example 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 absence 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 in the test sample, includes the quantitative

assessment of the ammonia present.

Now referring to FIG 1, the HBP sensor 100 includes an optical source 10, a stack 20 of alternating first 22,24,26 and second layers 23,25,27 and a detector 30. The optical source 20 is adapted to emit light towards the stack 20 of alternating layers. In the stack 20 of alternating first 22,24,26 and second layers 23,25,27, the first layer 22,24,26 includes silver chloride (AgCl) and the second layer 23,25,27 includes a material which is soluble in the test sample. The stack 20 of alternating layers in the HBP sensor 100 is arranged to receive light 12 emitted by the optical source 10. A light 12 emitted by the optical source 10 is reflected by the stack 20 of alternating layers. The detector 30 is arranged for detecting the light after being reflected i.e. a reflected light 14 from the stack 20 of alternating layers. The optical source 10 of the HBP sensor 100 may be a

broadband source or may be an optical source which is a source of a particular wavelength of light or a source of a narrow range of wavelengths of light. Examples of the optical source 10 may include, but not limited to, a Light-emitting diode (LED) , an array of multiple LEDs each producing the light 12 of same or different wavelengths, a Laser diode, an array of multiple Laser diodes each producing the light 12 of same or different wavelengths, a spectrometer, and so on and so forth. The optical source 10 is selected based on one or more of wavelengths of the light 12 at which the difference in properties of the reflected light 14 are specifically and sensitively detectable. The optical source 10 may produce the light 12 in visible spectrum or Infra-red spectrum or near infra-red spectrum.

The number of first layers 22,24,26 and/or the number of second layers 23,25,27 in the stack 20 may be an even or an odd number i.e. in one exemplary embodiment, the stack 20 of the HBP sensor 100 may include one or three first layers 22,24,26 and one or three second layers 23,25,27 whereas in a second exemplary embodiment, the stack 20 may include two first layer 22,24 and two second layers 23,25. It may be noted that FIG 1 that depicts three first 22,24,26 and three second layers 23,25,27 is not limiting and is for exemplary purposes only. There may be more than three first 22,24,26 and three second layers 23,25,27 in the stack 20.

Furthermore, it may also be noted that in the stack 20, number of first layers 22,24,26 may be same as or may be different than number of second layers 23,25,27 i.e. in one exemplary embodiment, the stack 20 of the HBP sensor 100 may include three first layers 22,24,26 and three second layers 23,25,27 whereas in a second exemplary embodiment, the stack 20 may include three first layer 22,24,26 and two second layers 23,25. It may be noted that FIG 1 that depicts three first 22,24,26 and three second layers 23,25,27 is not limiting and is for exemplary purposes only. It may also be noted that use of terms ^xfirst' and 'second' are only for representative purposes and for differentiating between the two types of layers and does not indicate any order of arrangement of the layers in the stack 20. As shown in FIG 1, one side of the stack 20 is a sample side 21 and other side of the stack 20 is a detection side 29, and the first 22,24,26 and the second layers 23,25,27 may be present in any order arranged from the sample side 21 to the

detection side 29. To explain further, in one exemplary embodiment, the sample side 21 may have the first layer 22 as the outermost layer as depicted in FIG 1 whereas in an alternate embodiment the sample side 21 may have the second layer 22 as the outermost layer contrary to as depicted in FIG 1. Furthermore, in one exemplary embodiment, the

detection side 29 may have the second layer 27 as the

outermost layer as depicted in FIG 1 whereas in an alternate embodiment the detection side 29 may have the first layer 26 as the outermost layer contrary to as depicted in FIG 1.

Thus, the number and order of arrangement of the first layers 22,24,26 and the second layers 23,25,27 in the stack 20 may be varied as desired by the application and use of the HBP sensor 100.

The refractive index of the first layers 22,24,26 is

different from the refractive index of the second layers 23,25,27. In one embodiment of the HBP sensor 100, the refractive index of the first layers 22,24,26 is higher than the refractive index of the second layers 23,25,27. In an alternate embodiment of the HBP sensor 100, the refractive index of the first layers 22,24,26 is lower than the

refractive index of the second layers 23,25,27. As aforementioned, the first layers 22,24,26 includes silver chloride whereas the second layers 23,25,27 includes a material which is soluble in the test sample. When using the HBP sensor 100 in-vivo, the test sample is the content of the GI tract of the test subject and thus contains hydrochloric acid. Whereas when using the HBP sensor 100 in vitro, the test sample or part of the test sample is collected from the GI tract of the test subject and thus includes hydrochloric acid. Therefore in an exemplary embodiment of the HBP sensor 100, the second layers 23,25,27 include a material which is soluble in hydrochloric acid present in the test sample.

Examples of the material of the second layer 23,25,27 are, but not limited to, cellulose, gelatin, variants of glass that are dissolvable in hydrochloric acid, and so on and so forth. Furthermore, when using the HBP sensor 100 in vitro, an ingredient may be added to the test sample which may specifically dissolve the material of the second layers 23, 25, 27.

The detector 30 detects the reflected light 14. More

specifically, in one embodiment of the HBP sensor 100, the detector 30 determines or detects the intensity of the reflected light 14. The detector 30 may include, but not limited to, a photodiode, a spectrophotometer, and so on and so forth.

Referring now to FIG 2, an embodiment the HBP sensor 100 includes a housing 40. The stack 20 of alternating layers is positioned inside the housing 40 such that the stack 20 of alternating layers is able to contact the test sample only at one end of the stack 20 i.e. at the sample side 21 of the stack 20. The other end of the stack 20 i.e. the detection side 29 of the stack 20 is sealed off from the test sample. The material of the housing 40 is inert to the test sample to be analyzed, especially with respect to hydrochloric acid and/or ammonia. The housing 30 ensures controlled exposure of the stack 20 of alternating layers to the test sample. Thus the layers 22,23,24,25,26,27 of the stack 20 are exposed sequentially and in a controlled manner when contacted with the test sample. To explain further, as depicted in FIG 2 in combination with FIG 1, if ammonia is present in the test sample then the first layer 22 is dissolved first as due to the housing 40 only the first layer 22 is allowed to come in contact with the test sample. Only when a part of the first layer 22 is dissolved the second layer 23 is exposed to the test sample and gets dissolved in the test sample. This in turn exposes the underlying first layer 24 which gets

dissolved in presence of ammonia, if any in the test sample, resulting into exposure of the underlying second layer 25, and so on and so forth. In the HBP sensor 100, optionally, the optical source 10 and/or the detector 30 are positioned inside the housing 40 to protect against the test sample or its constituents.

FIG 3 is used to explain the working of the HBP sensor 100. In FIG 3, ^λΧ' axis represented by reference numeral 54 represents wavelength of the light 12 and ^λΥ' axis

represented by reference numeral 54 represents intensity of the light 12 detected at the detector 30. As an example and for purposes of explanation, the graph 50 shows three curves namely curve 68, curve 64 and curve 62. In the graph 50, ^λΝ' represents total number of layers 22,23,24,25,26,27 of the stack 20 present in the HBP sensor. The graph 50 represents a standard graph for the HBP sensor 10 i.e. specifically curve 68 shows the standard curve for the stack 20 in which total number of the first and the second layers 22,23,24,25,26,27 is eight, specifically curve 64 shows the standard curve for the stack 20 in which total number of the first and the second layers 22,23,24,25,26,27 is four and specifically curve 62 shows the standard curve for the stack 20 in which total number of the first and the second layers

22,23,24,25,26,27 is two. The standard curves show the intensities of the reflected light 14 for different

wavelengths of the light 12 shined upon the stack 20 for stacks 20 having different number of layers

22,23,24,25,26,27. Such standard curves 68,64,62 are used to determine the extent of ammonia present in the test sample.

For example, let us assume a test case with an unknown sample i.e. it is not known whether ammonia is present in the test sample or not. The test sample is analyzed using the HBP sensor 10 with stack 20 in which say total number of first layers 22,24,26 and second layers 23,25,27 is eight i.e. N = 8. The HBP sensor 10 is introduced into the test sample such that the sample side 21 of the stack 20 comes in contact with the test sample. The optical source 10 is activated to emit the light 12 towards the detection side 29 of the stack 20. The reflected light 14 is detected at the detector 30. Say the optical source 10 produces the light 12 of 660 nm

(nanometer) wavelength. After continued exposure, for a predetermined period of time, of the stack 20 to the test sample if no change in the intensity of the reflected light

14 is detected then it is concluded that the test sample does not have any ammonia present which in turn leads to the conclusion that no HBP infection is present in the test sample. On the other hand if after continued exposure, for a predetermined period of time, of the stack 20 to the test sample if a change in the intensity of the reflected light 14 is detected then it is concluded that ammonia is present in the test sample which in turn leads to the conclusion that HBP infection is present in the test sample. The change in the intensity is represented in the graph 50 for the double headed arrow represented by reference numeral 55 which depicts the intensities at 660 nm for N=2, N=4, and N=8.

Additionally since the time of exposure of the stack 20 to the test sample is known, the rate of loss of the layers 22,23,24,25,26,27 of the stack 20 is determined. From the rate of loss of the layers 22,23,24,25,26,27 of the stack 20 the amount of ammonia present in the test sample is determined because the rate of loss of the layers 22,23,24,25,26,27 of the stack 20 is directly proportional to the amount of ammonia present in the test sample. FIG 4 is a flow chart illustrating a method 1000 for

analyzing a test sample of a test subject for presence of Helicobacter pylori, in accordance with aspects of the present technique. FIG 4 has been explained hereinafter in combination with FIGs 1 to 3 and their descriptions provided hereinabove. The method 1000 uses the HBP sensor 100 as described in reference to FIG 1 and 2. The presence of HBP in the test sample is performed by determining an extent of ammonia present in the test sample. In the method 1000, the stack 20 of alternating layers 22,23,24,25,26,27 of the HBP sensor 100 is contacted with the test sample to be analyzed in a step 500 and the light 14 from the optical source 10 is directed, in a step 520 of the method 1000, towards the stack 20 of alternating layers 22,23,24,25,26,27 of the HBP sensor 100 after or during the contact of the stack 20 with the test sample in step 500. In one embodiment of the method 1000, the step 520 may be performed after the step 500, whereas in another embodiment of the method 1000, the step 500 and the step 520 may be performed simultaneously. The light 12 may be a broadband light i.e. having a broad range of wavelengths or may be light of a particular wavelength or light of a narrow range of wavelengths.

Subsequent to step 520, the light 12 from the optical source 10 after being reflected from the stack 20 of layers i.e. the reflected light 14 is detected in a step 540. The detection of the reflected light 14 is performed using the detector 30 as described in FIG 1 and 2. Finally, from intensity of the reflected light 14 detected in the step 540, the extent of ammonia present in the test sample is calculated in step 560. The calculation of extent of ammonia and thus the

determination of presence or absence of HBP in the test sample is performed in accordance with the description provided hereinabove for FIG 3. As may be appreciated by a person skilled in the art of optics, the term "intensity" as used herein includes any other related measurement pertaining to the reflected light 14 obtained after reflection from the stack 20 which in turn provides an indication or measurement of the intensity of the reflected light 14.

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 for analyzing a test sample for presence of Helicobacter pylori by determining an extent of ammonia present in the test sample, the Helicobacter pylori sensor comprising:

- an optical source adapted to emit light,

- a stack of alternating first and second layers, wherein the first layer comprises silver chloride and the second layer comprises a material which is soluble in the test sample, the stack of alternating layers being arranged to receive the light emitted by the optical source, and

- a detector arranged for detecting the light from the optical source after being reflected from the stack of alternating layers,

wherein, on contacting the stack of alternating layers with the test sample, the extent of ammonia present in the test sample is determinable by measuring an intensity of the light detected by the detector.

2. The Helicobacter pylori sensor according to claim 1, wherein the optical source is a Light-emitting diode.

3. The Helicobacter pylori sensor according to claim 1, wherein the optical source is a Laser diode.

4. The Helicobacter pylori sensor according to claim 1, wherein the optical source is a broadband source.

5. The Helicobacter pylori sensor according to any of claims

1 to 4, wherein the detector is a photodiode.

6. The Helicobacter pylori sensor according to any of claims 1 to 4, wherein the detector is a spectrophotometer.

7. The Helicobacter pylori sensor according to any of claims 1 to 6, wherein the material of the second layer is

cellulose .

8. The Helicobacter pylori sensor according to any of claims 1 to 6, wherein the material of the second layer is gelatin.

9. The Helicobacter pylori sensor according to any of claims 1 to 6, wherein the material of the second layer is glass dissolvable in hydrochloric acid.

10. The Helicobacter pylori sensor according to any of claims 1 to 9, further comprising a housing, wherein the stack of alternating layers is positioned inside the housing such that the stack of alternating layers is adapted to contact the test sample only at one end of the stack.

11. The Helicobacter pylori sensor wherein the optical source is positioned inside the housing.

12. The Helicobacter pylori sensor wherein the detector is positioned inside the housing.

13. A method for analyzing a test sample for presence of Helicobacter pylori by determining an extent of ammonia present in the test sample by using a Helicobacter pylori sensor according to any of claims 1 to 9, the method

comprising:

- contacting the stack of alternating layers of the

Helicobacter pylori sensor with the test sample to be

analyzed,

- directing light from the optical source towards the stack of alternating layers of the Helicobacter pylori sensor,

- detecting the light from the optical source after being reflected from the stack of layers, and

- calculating, from intensity of the light detected, the extent of ammonia present in the test sample.

14. The method according to claim 10 wherein the light directed from the optical source towards the stack of

alternating layers is a broadband light.

15. The method according to claim 10 wherein the light directed from the optical source towards the stack of alternating layers is a light of predetermined wave length.