METHOD OF MAKING A TEST STRIP FOR IMPROVED MEASUREMENT OF SPECIFIC GRAVITY

Abstract

The present disclosure relates to a method of manufacturing a test strip for measuring the specific gravity of a urine sample, the method comprising successively: - providing a polyelectrolyte in a first solution, the polyelectrolyte being a poly(methyl vinyl ether-alt-maleic anhydride), - adding to the first solution a base to neutralize the polyelectrolyte and bring the first solution to a pH between 10 and 11, - adding to the first solution a buffering agent to bring and maintain the first solution at a pH between 7.0 and 7.5, - dipping a paper strip into the first solution, - dipping the paper strip into a second solution comprising a pH-sensitive colored indicator. Figure 9

Description

Title of the invention: METHOD OF MANUFACTURING A TEST STRIP ALLOWING AN IMPROVED MEASUREMENT OF SPECIFIC GRAVITY Technical field

[0001] The present disclosure relates to a method of manufacturing a test strip for measuring the specific gravity of a urine sample. The present disclosure also relates to a test strip for determining the specific gravity of a urine sample manufactured according to such a method.

[0002] The strip is adapted to be disposed in a cartridge configured to be inserted into a urine analysis station. The station may be installed on the surface of the toilet bowl. The cartridge mounted on the station will be referred to as an analysis device. The station includes a light source and an optical sensor for performing an optical analysis on the strip. Prior art

[0003] Urine can be a source of useful information about the user's health. Monitoring a user's urine can provide information, for example, about what the user ingests, about body waste, and about excess mineral salts.

[0004] In particular, measuring the specific gravity of a user's urine may be useful for assessing hydration status, kidney function, monitoring certain diseases such as diabetes and kidney disease, monitoring response to medical treatment, assessing urinary tract disorders such as urinary tract infections (UTIs), kidney stones or other conditions affecting urine concentration, monitoring hyponatremia or hypernatremia, detecting heart failure, etc.

[0005] A urine specific gravity test compares the density of urine to that of water and indicates the total concentration of all chemical particles present in the urine.

[0006] There are several methods for determining the specific gravity of urine.

[0007] The most common, and perhaps least accurate, method uses a urinometer. The urinometer is a weighted, pear-shaped instrument with a cylindrical stem containing a scale calibrated to specific gravity. The urinometer method is bulky and has the disadvantages of requiring large volumes of urine samples, making reading the urinometer scale difficult and inaccurate, and making analyses unreliable because the urinometer is not regularly recalibrated.

[0008] Refractometry is an indirect method of measuring the specific gravity of urine. The refractometer method is the gold standard for determining urine specific gravity. However, the refractometer has the major disadvantage of requiring daily calibration and is not suitable for home testing.

[0009] A third method of urine analysis for specific gravity, the falling drop method, like the furinometer, is a direct measurement of the specific gravity of urine. In this method, a drop of urine is introduced into each of a series of columns filled with solvent mixtures of increasing and known specific gravity. Before the development of the refractometer, this technique had the advantage of requiring only a few drops of sample to perform a specific gravity determination. The falling drop method, however, has never been widely used in routine urine analysis due to the time required to set up such a system and the impossibility for an individual to perform the analysis at home.

[0010] Each of the instrument-based specific gravity analysis methods described above has disadvantages, none of which is particularly well-suited to performing specific gravity analyses outside of the physician's office or laboratory.

[0011] Therefore, reagent-impregnated strips have been developed to enable the determination of specific gravity at home. These test strips indirectly measure specific gravity, with the strip changing color depending on the ionic strength of the urine sample.

[0012] These strips measure in particular the sodium concentration, which is the main factor in specific gravity. Sodium ions are captured using polyelectrolytes and hydrogen ions are released. These hydrogen ions are then detected using a pH indicator which shows a color change.

[0013] However, currently commercially available test strips are known for their performance issues due to their sensitivity to changes in urine pH. This makes the tests inherently difficult to interpret because the values ​​are scattered. For example, the article "Dip stick measurements of urine specific gravity are unreliable" by de Buys Roessingh et al compared different methods and concluded that only refractometry gives reliable results on urine specific gravity, while dipstick measurements (i.e., test strips) do not.

[0014] Several solutions have been proposed to improve the detection of specific gravity.

[0015] US 4,318,709 discloses the use of weakly acidic or basic polyelectrolytes that have been neutralized at least 50% with a base or acid. Depending on the ionic strength of the test solution, an intra- lecular can occur in the polymer, the degree of which is a barometer of ionic strength. A pH indicator, such as a pH-sensitive compound, reflects the change in pH (or lack thereof) caused by the ionic strength of the sample.

[0016] US5,403,744 discloses a composition for determining specific gravity comprising a strong polyelectrolyte, an indicator and buffered to a pH of 3 or less.

[0017] Document US 4,376,827 discloses a composition for determining specific gravity comprising a strongly acidic or strongly basic polyelectrolyte and a buffer substance capable of providing a pH of about 5.5, as well as an indicator.

[0018] Document EP0023631 discloses a reagent for determining specific gravity. In addition to a strongly acidic or strongly basic polyelectrolyte polymer, it contains a buffer substance which ensures a pH of at least 5.5 and a pH indicator. DISCLOSURE

[0019] Unlike the prior art and currently commercially available test strips, the present document aims to reduce the variability and increase the sensitivity of urine specific gravity measurement.

[0020] The objective of the disclosure is also to provide rapid, accurate and reliable determination of urine specific gravity using a test strip that can be used at home.

[0021] To this end, the disclosure relates to a method of manufacturing a strip for measuring the specific gravity of a urine sample, the method successively comprising: - providing a polyelectrolyte in a first solution, the polyelectrolyte being poly(methyl vinyl ether-alt-maleic anhydride), - add a base to the first solution, to neutralize the polyelectrolyte and bring the first solution to a pH between 10 and 11, - add a buffering agent to the first solution to bring and maintain the first solution at a pH between 7.0 and 7.5, - soak a strip of paper in the first solution, - dip the paper strip into a second solution containing a pH-sensitive colored indicator.

[0022] The disclosure also relates to a method of manufacturing a strip for measuring the specific gravity of a urine sample, the method successively comprising: - providing a polyelectrolyte in a first solution, the polyelectrolyte being in particular a polyacid, - add a base to the first solution, to neutralize the polyelectrolyte and bring the first solution to a pH between 10 and 11, - add a buffering agent to the first solution to bring and maintain the first solution at a pH between 7.0 and 7.5, - soak a strip of paper in the first solution, - soak the strip of paper in a second solution comprising a pH-sensitive colored indicator.

[0023] In one embodiment, the method further comprises drying the paper web after each dipping.

[0024] In one case, the base is sodium hydroxide (NaOH).

[0025] In one case, the base is a mixture of sodium hydroxide (NaOH) and hydroxide of potassium, preferably in a mass ratio of between 2.6 and 3.5.

[0026] In one embodiment, the neutralization is carried out by titrating the polyelectrolyte until the first solution reaches a pH between 10 and 11.

[0027] In one case, the neutralization is achieved by a one-pot synthesis.

[0028] In one case, the polyelectrolyte is neutralized to at least 80%, preferably to more of 85%.

[0029] In one case, the buffering agent is Tris(hydroxymethyl)aminomethane hydrochloride, in particular a 1 M (mol / L) solution of Tris HCl.

[0030] In one case, the pH-sensitive colored indicator is bromothymol blue.

[0031] The disclosure also relates to a test strip for determining the specific gravity of a urine sample made by the method described above, the test strip determining the specific gravity of the urine sample based on the intensity of the color change of the pH-sensitive colored indicator.

[0032] In one embodiment, the test strip further comprises a pH test block.

[0033] The disclosure also relates to a cartridge for an optical urine analysis device, the cartridge comprising a plurality of chambers arranged next to each other in the shape of a right circular cylinder of at least 80% of a circle with a diameter between 3 and 10 cm, wherein at least one chamber comprises a test strip as described above.

[0034] The cartridge further comprises a pH measuring strip disposed in at least one chamber.

[0035] The disclosure also relates to an optical urine analysis device comprising: - a cartridge as described above, - a station, configured to be positioned on a wall of a toilet bowl, the station comprising: + a housing comprising a compartment in which the cartridge is at least partially received, + an injector, configured to inject fluid onto the strip, + an analyzer to analyze a color change of the strip due to fluid from the fluid sample.

[0036] In one embodiment, the analyzer includes a light source and a light sensor, configured to emit and receive light. Brief description of the drawings

[0037] These characteristics and advantages of the disclosure will appear more clearly on reading the following description, provided solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0038] [Fig.l] shows the general configuration of a urine analysis device according to one embodiment, as installed on the surface of a toilet bowl,

[0039] [Fig.2] shows an exploded view of a model of an analysis apparatus, in which the station and cartridge are visible,

[0040] [Fig.3] shows a detailed view of a cartridge according to one embodiment,

[0041] [Fig.4] shows a sectional view of a cartridge model and station, the location of an optical analyzer of the station,

[0042] [Fig.5] shows a top view of a test strip according to a method of rea lization,

[0043] [Fig.6] shows a side view of the strip of [Fig.5],

[0044] [Fig.7] shows a chemical representation of the polyelectrolyte used in the method according to the present disclosure,

[0045] [Fig.8] shows a method of manufacturing a test strip for measuring the specific gravity of a urine sample according to the present disclosure,

[0046] [Fig.9] shows a graph representing the normalized intensities as a function of specific gravity:

[0047] - with a test strip manufactured according to a reference method,

[0048] - with a test strip manufactured according to a method in accordance with this di vulgation with NaOH as base, and

[0049] - with a test strip manufactured according to a method in accordance with this di vulgation with a mixture of NaOH and KOH as a base.

[0050] [Fig. 10] shows a graph representing the normalized intensities as a function of specific gravity with a test strip made with a method according to the present disclosure without the buffering step and with different urine pHs.

[0051] [Fig. 11] shows two graphs representing the normalized intensities in function of specific gravity:

[0052] - with a test strip manufactured according to a reference method with and without the buffering step (a) and

[0053] - with a test strip manufactured according to a method in accordance with this di- vulgation, with and without the stamping step (b).

[0054] [Fig. 12] shows a graph representing normalized intensities versus specific gravity with a test strip manufactured with a method according to the present disclosure using NaOH as a base, using urine containing different ion compositions.

[0055] [Fig. 13] shows a graph representing the normalized intensities as a function of specific gravity with a strip manufactured according to a method in accordance with the present disclosure using a NaOH / KOH mixture as a base, in the presence of different concentrations of potassium. DETAILED DESCRIPTION

[0056] The present description presents different examples of a cartridge usable with a station as disclosed in documents WO2021 / 175909 and WO2021 / 175944, hereinafter referred to as WO'909 and WO'944. Variants of the stations are presented in documents WO2023036805, WO2023036806, WO2023036808, WO2023036809, hereinafter referred to as WO'80X.

[0057] The following paragraphs explain the general principle of a urine analysis device, but all details of WO'909 and WO'933 (as well as all the aforementioned PCT documents) are applicable.

[0058] GENERAL DESCRIPTION OF THE STATION AND THE CARTRIDGE

[0059] [Fig.l] schematically illustrates an analysis device 100 (referred to as "device 100") for analyzing urine, installed in a toilet 102. The toilet 102 generally comprises a water tank 104, a bowl 106, a seat 108 and a seat cover 110. The analysis device 100 is removably disposed in the toilet 102. For example, the analysis apparatus 100 can be easily removed from the toilet to replace a cartridge, and then replaced in the toilet 102. The analysis device 100 is placed on an inner wall 112 of the toilet bowl 106. The analysis device 100 is positioned such that it is generally under a user's urine stream, such that when a user urinates (generally in a seated position), the urine contacts the analysis device 100. The analysis device 100 may communicate remotely with a remote entity, such as a smartphone 114 or a server 116.

[0060] As illustrated in more detail in [Fig. 2], the analysis device 100 comprises a station 200 and a cartridge 202, removably mounted on the station 200. The station 200 may comprise a housing 204 which may comprise two shells 206, 208. The housing 204 contains a urine analysis assembly. The station 200 comprises an annular housing 212, located inside the case 204, arranged around an axis of rotation A. The annular housing 212 is configured to receive at least by entially the cartridge 202 rotatably mounted about the axis of rotation A (once in position in the annular housing 212). The cartridge 202 comprises a plurality of test carriers which each comprise at least one urinary reagent, for example a dry reagent, the plurality of test carriers being arranged along a circle or an arc of a circle about the axis of rotation A. In one embodiment, the test carriers are test strips. The test carriers may be enclosed, for example individually, in a chamber.

[0061] The annular housing 212 typically extends around 360° and forms a groove configured to at least partially receive the cartridge 202.

[0062] The station 200 includes a collection opening 218, located for example on the shell 208. The collection opening 218 collects urine that flows onto the surface of the housing 204. A drainage opening (not shown) is also included to drain the liquid out of the device 100.

[0063] The housing 204 may have a diameter, in a direction perpendicular to the axis of rotation A, of between 50 mm and 150 mm.

[0064] The test assembly may include a pump, an injector, and an analyzer. The pump draws urine through the collection opening 218, then the injector injects the urine onto one or more test media of the cartridge, and the analyzer obtains certain property values ​​(e.g., physical / chemical properties, such as color) of the test media after they contact the urine. In one instance, the analyzer is an optical analyzer configured to analyze the optical properties of the test media. The injector and the cartridge may move relative to each other such that the injector may open (e.g., puncture) the chamber, such as using a needle or needle-like device.

[0065] [Fig.3] shows an exploded view of the cartridge 202. The cartridge 202 comprises at least one test holder 301, including several test holders 301 configured to receive urine from the injector. Each test holder 301 contains a urine reagent that reacts in a specific manner upon contact with urine. The cartridge 202 comprises a rotatable holder 300, configured to be rotated by the station 200. In normal use of the cartridge 202 and the device 100, the test holders 301 remain attached to the rotatable holder and do not move relative thereto.

[0066] In one embodiment, the rotatable holder 300 has a right circular cylinder shape of at least 80% of a hollow cylinder shape extending annularly about an axis which is, when the cartridge 202 is mounted in the station 200, the rotation axis A. Each test holder 301 may be a test strip. The rotatable holder 300 may comprise an annular portion 302 and a cylindrical portion 304, which extends from an outer radial end of the annular portion 302. The portion cylindrical portion 304, when used, is housed inside the annular housing 212. The test supports 301 are positioned along the cylindrical portion 304, so as to be able to scroll selectively and / or successively in front of the injector and the analyzer. For example, the test supports 301 are part of a support 308, which comprises several chambers 310, separated from each other along a perimeter around the axis A. At least one test strip is received in a chamber 310. Advantageously, a single strip is received in a chamber 310. In particular, each chamber 310 comprises a single strip.

[0067] The plurality of chambers 310 are arranged next to each other in the shape of a right circular cylinder of at least 80% of a circle. To allow light to pass through, the support 308 includes at least one opening 312 per chamber 310 (shown in the upper left zoom where the rotating support is shown as transparent). The chambers 310 are all equidistant from the rotation axis A, so that the injector can selectively inject urine once the desired chamber is positioned at the desired location facing the injector. The injector can move towards the chamber 310 and pierce a seal closing the chamber 310 (visible in [Fig. 4]). A drainage opening 314 is provided in the rotating support 300 to allow urine to be discharged from the injector to the outside of the device 100.

[0068] Each chamber 310 may have a maximum dimension, for example a height H, which is less than 10% more than the maximum extent of the test support, as will be explained below. In particular, each chamber 310 may have a height along the axis of rotation A of less than 2 cm, in particular less than 1.5 cm.

[0069] Each chamber 310 may have a transverse width W, orthogonal to the axis of rotation A, between 1 mm and 6 mm.

[0070] The annular portion 302 of the rotary support 300 remains outside the annular housing 212 to reinforce the cylindrical portion and / or to drive the cartridge 202 in rotation. For this purpose, the annular portion 302 may comprise a mechanical coupling 306, which cooperates with a shaft of the station 200.

[0071] The dimensions relating to the cartridge 202 are described in documents WO'909, WO'933 and WO'80X. The maximum dimension of the device 100 transversely to the axis of rotation A is less than 15 cm, or even less than 10 cm. The maximum dimension of the device along the axis of rotation A is less than 5 cm.

[0072] [Fig. 4] illustrates in more detail the interaction between the cartridge 202 and the station 200 when or after the activation of the injector. The analyzer 400 comprises at least one light source 402, 404 (for example, two) and at least one optical sensor 406. The light goes from the light source 402, 404 to the optical sensor 406 passing through the cartridge 202 and in particular the cylindrical part 304, the opening 312 of the support 308, the test support 301 and therefore the reagent 408.

[0073] In one embodiment, the analyzer 400 is configured to measure the absorbance of a portion of the test media 301 (including the test line and / or the control line of a test strip, as will be explained below). The absorbance is detected by the light source (e.g., a light-emitting diode) that can pass light through the strip, and by the optical sensor that receives the spectrum of about ten wavelengths.

[0074] In one variant, the light sensor is a camera capable of detecting a change in color, in particular a change in color intensity, of a portion of the test media 301 (in particular the test line and / or the control line of a test strip, as will be explained below). The camera can detect a color in RGB values ​​for example.

[0075] The injector comprises an injection end 412 (e.g. a needle), which can be moved between several positions, represented by dashed lines in [Fig. 4]. In the standby position SP, the injection end 412 is outside the cartridge 202 (in an innermost position), so that the cartridge 202 can rotate freely in the annular housing 212; in the injection position IP, the injection end 412 has pierced the seal 410 to access the interior of the chamber 310 and can inject some urine onto the test support 301; in the emptying position DP, the injection end 412 is able to discharge the urine through the emptying opening 314 of the rotating support 300.

[0076] In position SP, the injector is located radially inside the annular chamber. This makes it possible to maximize the radius of the annular chamber while minimizing the size of the station 200. GENERAL DESCRIPTION OF THE TEST STRIP

[0077] The test support 301 may be a test strip 500. As seen in FIGS. 5 and 6, the strip 500 extends mainly along a longitudinal direction X. In one embodiment, the strip 500 has a generally parallelepiped shape. The strip 500 may have a width of less than 5 mm, in particular between 0.5 mm and 3 mm in a transverse direction Y, orthogonal to the longitudinal axis X. The strip 500 may have a length of less than 20 mm, in particular between 10 mm and 15 mm, along the longitudinal axis X. The strip 500 has a thickness along an elevation axis Z which varies along the strip depending on its components. The 500 strip includes various components and materials that absorb and / or react to urine, including urine sodium or urine pH.

[0078] To this end, the test strip 500 comprises a test block 520 (also called a test pad) configured to measure the specific gravity of urine (and called the specific gravity test block 520) and a support block 530. The test strip 500 may also include a reagent block 540 configured to measure the pH of urine (referred to as reagent block 540).

[0079] The support block 530 may be made of Whatman CF3 paper.

[0080] The specific gravity test block 520 is attached to the support block 530, for example with at least one adhesive strip 550. The adhesive tape 550 is in particular a double-sided adhesive. The adhesive tape 550 is for example an acrylic-based adhesive.

[0081] The pH test block 540 is attached to the support block 530, for example, with at least one adhesive strip 560. The adhesive strip 560 is in particular a double-sided adhesive. The adhesive strip 560 is, for example, an acrylic-based adhesive.

[0082] An end 570 of the strip 500 along the longitudinal axis X, in particular the end of the support block 530, is configured to receive a urine sample. In particular, the end 570 is configured to face the end 412 of the injector when the strip 500 is disposed in a chamber 310 of the cartridge 202 and placed inside the analysis device 100. The end 570 is configured to receive the urine injected by the injector onto the strip 500.

[0083] The specific gravity test block 520 may extend a length along the longitudinal axis X of less than 4 mm.

[0084] The specific gravity test block 520 comprises a support matrix impregnated with a reagent composition comprising a polyelectrolyte, a pH-sensitive color indicator, and a buffering agent. The polyelectrolyte is particularly partially neutralized poly(methyl vinyl ether-alt-maleic anhydride), as shown in [Fig.7] (b). The pH-sensitive color indicator may be bromothymol blue. A method of manufacturing the specific gravity test block 520 will be described below.

[0085] The polyelectrolyte used in the present disclosure is a polyacid. The polyacid is neutralized with a base or a mixture of bases. During neutralization, several hydrogen ions of the carboxylic groups are replaced by sodium or sodium and potassium, depending on the base used. When a solution of known specific gravity is added to the reagent block containing the polyelectrolyte, the degree of ionization of the polyelectrolyte changes, resulting in a release of H+ ions and a change in the pKa of the polyelectrolyte. This release of H+ ions results in a change in the pH on the specific gravity test block 520, which is measured using the pH indicator. In the presence of a buffer in the recipe, the pH of the surface of the specific gravity test block 520 is controlled by the buffer and any change in pH on the specific gravity test block 520 due to specific gravity is measured as a pH deviation from the pH of the buffer.

[0086] The pH 540 test block is arranged next to the gravity sampling pad specific 520, particularly between the end 570 and the specific gravity block 520 along the longitudinal axis X. The pH test block 540 may extend over a length along the longitudinal axis X of less than 4 mm.

[0087] A conventional 540 pH test block may be used here.

[0088] Referring again to [Fig.4], each test pad 520, 540 is configured to face the light sources 402, 404 on one side and the optical sensor 406 on the other side when the test strip 500 is disposed in a chamber 310 of the cartridge 202 and placed inside the analysis apparatus 100.

[0089] The test strip 500 may also comprise at least one optical mask 580, in particular three optical masks 580. Each mask 580 is fixed to the support block 530 using at least one adhesive strip 590. Each optical mask 580 makes it possible to avoid light leaks and to improve the sensitivity of the optical sensor and the accuracy of the measurements.

[0090] The test strip 500 presented herein may be used with the previously presented cartridge 202 and the urine analysis device as will be described below. In particular, at least one test strip 500 is received in a chamber 310 of the cartridge 202. They constitute a cost-effective, manufacturing-efficient, easily adaptable and mass-production-friendly solution for improving the quality of optical analysis and, in particular, specific gravity measurements.

[0091] When the test strip 500 does not include a pH test block 540, the cartridge 202 may also include a pH measuring strip disposed in at least one chamber 310, different from the chamber in which the test strip 500 is received. METHOD OF MANUFACTURING THE TEST STRIP

[0092] A method 800 of manufacturing a specific gravity test pad 540 will now be described with reference to [Fig.8].

[0093] In step 802, a polyelectrolyte is provided in a first solution. The polyelectrolyte is in particular a polyacid. The polyelectrolyte is in particular poly(methyl vinyl ether-alt-maleic anhydride), shown in [Fig.7] (a). For example, the poly(methyl vinyl ether-alt-maleic anhydride) may be provided in powder form and is then dissolved in an aqueous solvent to form the first solution. Upon contact with water, the poly(methyl vinyl ether-alt-maleic anhydride) becomes poly(methyl vinyl ether-alt-maleic acid), as shown in [Fig.7] (b).

[0094] In step 804, called neutralization step 804, a base is added to the first solution to neutralize the polyelectrolyte and bring the first solution to a pH between 10 and 11.

[0095] By neutralization of the polyelectrolyte is meant that at least a portion of the ionizable groups is neutralized. In particular, one or more of the carboxyl groups are neutralized.

[0096] The polyelectrolyte is neutralized to at least about 80%, preferably more than 85%. This means that at least 80% of the carboxyl groups are neutralized, preferably at least 85%.

[0097] In one case, the base is sodium hydroxide (NaOH).

[0098] In a variation of potassium hydroxide, the base is a mixture of sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0099] In one embodiment, the mass ratio between NaOH and is between 2.6 and 3.5, for a poly(methyl vinyl ether-alt-maleic anhydride) supplied by Sigma-Aldrich (ref 416339). When the polyelectrolyte is supplied by another manufacturer, the mass ratio must be adapted accordingly.

[0100] The polyelectrolyte, which is a carboxylic acid, reacts with the strong bases NaOH and KOH to produce carboxylate salts:

[0101] In one embodiment, the neutralization is carried out by titration of the polyelectrolyte. In particular, the titration is carried out up to a pH between 10 and 11.

[0102] In one variant, the neutralization is carried out by one-pot synthesis. This method involves mixing the chemical compounds in a single container and allowing them to react, rather than carrying out the reaction in several separate steps. In particular, one-pot synthesis is used when the amount of base to be used for the first solution to reach a pH between 10 and 11 is known.

[0103] In step 806, called buffering step 806, a buffering agent is added to the first solution, after neutralization of the polyelectrolyte, to bring the first solution to a pH between 7.0 and 7.5. The buffering agent then makes it possible to maintain the first solution at a pH between 7.0 and 7.5. At this stage, the first solution comprises the polyelectrolyte and the buffer.

[0104] In particular, the buffering agent is Tris(hydroxymethyl)aminomethane hydrochloride (Tris HCl). Preferably, the buffering agent is a 1 M (mol / L) solution of Tris HCl.

[0105] It should be noted that in the absence of sodium in this buffer solution, the neutralization of the polyelectrolyte carried out previously is not disturbed.

[0106] After the buffering step, the polyelectrolyte concentration in the first solution may be between 0.020 g / mL and 0.025 g / mL, in particular around 0.023 g / mL, for a poly(methyl vinyl ether-alt-maleic anhydride) supplied by Sigma-Aldrich (ref 416339).

[0107] If supplied by another manufacturer, the polyelectrolyte concentration must be adapted according to the characteristics of the polyelectrolyte (IR spectrum), its viscosity, etc.

[0108] In step 808, a strip of paper is dipped into the first solution. At this step, the first solution includes the polyelectrolyte, the base and the buffer.

[0109] In one case, the paper web consists of a Whatman CF3 backing with CF3 paper reagent pads.

[0110] In particular, the paper strip is immersed in the first solution for at least 3 to 5 minutes.

[0111] In step 810, the paper web is then dried. For example, the paper web is dried in an oven for at least 60 minutes.

[0112] In step 812, a second solution is provided. The second solution comprises a pH-sensitive colored indicator. The pH-sensitive colored indicator is, for example, bromothymol blue. The second solution may comprise an organic solvent.

[0113] In one case, bromothymol blue is present at a concentration of 0.001 g / mL in the second solution.

[0114] In step 814, the paper strip is immersed in the second solution comprising a pH-sensitive colored indicator. In particular, the paper strip is immersed in the second solution for at least 3 to 5 minutes.

[0115] In step 816, the paper web is then dried. For example, the paper web is dried in an oven for at least 60 minutes.

[0116] The paper web after step 816 of manufacturing method 800 is the specific gravity test block 520, as previously discussed in connection with [Fig.6]. EXPERIENCES

[0117] The disclosure is illustrated by the following experiments.

[0118] Experiment No. 1:

[0119] With reference to [Fig.9], experiment no. 1 compares the specific gravity measurements with a test strip manufactured: - with a reference method (rounds), - with a test strip manufactured according to a method in accordance with the present disclosure with NaOH as the base (triangle), and - with a strip manufactured according to a method in accordance with the present disclosure with a mixture of NaOH and KOH as base (square).

[0120] The reference method involves dipping a paper strip into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride) neutralized to pH 8, and then dipping the paper strip into a second solution comprising bromothymol blue, which is a pH-sensitive color indicator. The term "reference method" is used herein only to designate a method used for comparison purposes with the method according to the present disclosure.

[0121] The method according to the present disclosure comprises dipping a strip of paper into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride) neutralized to a pH between 10 and 11 and then buffered to a pH between 7.0 and 7.5, then dipping the paper strip into a second solution comprising bromothymol blue, which is a pH-sensitive color indicator.

[0122] Urinary pH is not controlled and varies between 6 and 7.

[0123] The specific gravity of urine varies between a low specific gravity of 1.00 and a high specific gravity of 1.03.

[0124] The potassium concentration is less than 40 mM.

[0125] The graphs in [Fig.9] represent the normalized intensities as a function of the specific gravity of the urine.

[0126] [Fig.9] shows better linearity for both methods according to the disclosure than for the reference method, despite a lower slope.

[0127] Experiment No. 2:

[0128] With reference to [Fig. 10], experiment no. 2 compares the specific gravity measurements with a strip manufactured using a method without a buffering step and with synthetic urine at respective pHs of 6, 6.5, 7 and 8.

[0129] The method involves dipping a strip of paper into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride), and then dipping the strip of paper into a second solution comprising bromothymol blue, which is a pH-sensitive color indicator.

[0130] [Fig. 10] shows that the best linearity is obtained with a pH of 7. Therefore, the method according to the present disclosure comprises the addition of a buffer of pH 7.0 to 7.5 in the step of preparing the polyelectrolyte. Experiment #3:

[0131] With reference to [Fig. 11], experiment no. 3 compares the specific gravity measurements: - (a) with a test strip manufactured according to a reference method with and without buffering step at a pH of 7, and - (b) with a test strip manufactured according to a method 800 comprising steps 802, 804, 806, 808 and 814 and according to a method comprising steps 802, 804, 808 and 814, but not comprising the buffering step 806 of method 800.

[0132] Reference method (a) consists of dipping a paper strip into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride)neutralized to a pH of 8, with or without the buffering step, and then dipping the paper strip into a second solution comprising bromothymol blue, which is a pH-sensitive colored indicator.

[0133] Method (b) here consists of dipping a strip of paper into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride) neutralized to a pH between 10 and 11, with or without the buffering step 806, then dipping the paper strip into a second solution comprising bromothymol blue, which is a pH-sensitive colored indicator.

[0134] A synthetic urine with pH 6.5 is used.

[0135] [Fig. 11] (b) shows lower errors and a plateau above the specific gravity of 1.025 in the presence of buffer compared to the reference test of [Fig. 11] (a) which shows saturation at the specific gravity of 1.020 with or without buffer.

[0136] In [Fig.l 1] (b), the impact of the presence or absence of buffer is evident compared to [Fig.l 1] (a). The amplitude of the response curve in [Fig.l 1] (b) without buffer is larger than with buffer, but the errors are overall better, especially at lower specific gravities, with buffer than without buffer.

[0137] In addition, the presence of the buffer should reduce the impact of urine pH on the test. Experiment #4:

[0138] With reference to [Fig. 12], experiment No. 4 compares specific gravity measurements with a test strip manufactured according to a method in accordance with the present disclosure in the presence of different ion compositions in urine: - sodium and a high concentration of potassium (approximately 70 mM K+); - calcium instead of sodium and a high level of potassium; and - calcium and low potassium levels (<2mM K+).

[0139] The method according to the present disclosure comprises dipping a strip of paper into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride) neutralized to a pH between 10 and 11 and then buffered to a pH between 7.0 and 7.5, and then dipping the strip of paper into a second solution comprising bromothymol blue, which is a pH-sensitive colored indicator.

[0140] The polyelectrolyte is here neutralized with NaOH.

[0141] [Fig. 12] shows that specific gravity measurements made with strips manufactured according to a method in accordance with the present disclosure have a low sensitivity to ionic composition (in particular the presence of potassium and calcium) for the same specific gravity, which is acceptable. In particular, if the urine contains calcium and potassium but not sodium, the strip always reacts to specific gravity. Experiment #5:

[0142] With reference to [Fig. 13], Experiment No. 5 compares a specific gravity measurement with a strip manufactured according to a method in accordance with the present disclosure in the presence of low, intermediate and high concentrations of potassium (<2mM K+, about 40 mM K+ and about 70 mM K+ respectively).

[0143] The method according to the present disclosure consists herein of dipping a strip of paper into a first solution comprising poly(methyl vinyl ether-alt-maleic anhydride) neutralized to a pH between 10 and 11 then buffered to a pH between 7.0 and 7.5, then dipping the strip of paper into a second solution comprising bromothymol blue.

[0144] It is known that the presence of a high concentration of potassium reduces the response compared to the response in low potassium urine (less amplitude between low and high specific gravities).

[0145] To compensate for this effect, the polyelectrolyte is neutralized with a KOH / NaOH base ratio. Indeed, [Fig. 13] shows that the mixture of sodium hydroxide and potassium hydroxide makes it possible to reduce the sensitivity to potassium for specific gravity measurements compared to the use of sodium hydroxide alone. OPERATION OF THE STATION AND THE STRIP

[0146] The operation of the station 200 and the test strip 500 will now be described.

[0147] The station 200 is installed in the toilet 102, as illustrated in [Fig.l]. A cartridge 202 is removably mounted in the station 200. The cartridge 202 comprises at least one test strip 500 as described above, disposed in a chamber 310. Advantageously, the cartridge 202 further comprises a pH measuring strip disposed in at least one chamber 310.

[0148] An individual can urinate on the station 200. A portion of the urine stream is collected through the collection opening 218. With reference to [Fig. 4], the injector is initially in the standby position SP and the injection end 412 is outside the cartridge 202 (in an innermost position), so that the cartridge 202 can rotate freely in the annular housing 212. In particular, the test strip 500 is placed in front of the injector.

[0149] Then, the injector moves to the IP injection position and the injection end 412 pierces the seal 410 to access the interior of the chamber 310 and injects urine onto the end 570.

[0150] Urine and sodium ions present in the urine flow through the strip 500, particularly towards the specific gravity test block 520 and finally towards the pH test block 540 thanks to the support block 530.

[0151] Specific gravity test block 520 shows a color change due to the pH sensitive color indicator, namely bromothymol blue, in response to the specific gravity of the urine.

[0152] The pH 540 test block changes color depending on the pH of the urine.

[0153] Station 200 then performs an optical analysis. For this purpose, the light source 402, 404 illuminates the test block(s) 520, 540 and possibly the reference block 540. The light goes from the light sources 402, 404 to the optical sensor 406 while passing through the cartridge 202 and in particular the cylindrical part 304, the opening 312 of the holder 308, the test strip 500 and in particular the test pad(s) 520, 540.

[0154] The optical sensor 406 acquires optical data through the light emitted by the test strip 500. In particular, the optical sensor 406 analyzes the color variation and determines a specific gravity of the urine sample and optionally the pH of the urine sample.

[0155] The optical sensor 406 may use the measured pH to verify that the pH of the urine is within a range medically considered normal, for example between 5.5 and 7.

[0156] The station 200 may remotely communicate the determined specific gravity, and possibly the pH, to a remote entity, such as the smartphone 114 or a server 116. In a variant, the station 200 may communicate a "low", "normal" or "high" indicator representative of the measured specific gravity relative to an expected specific gravity. The individual can thus easily and regularly monitor the specific gravity of his urine.

Claims

Claims

1. A method (800) of manufacturing a test strip (500) for measuring the specific gravity of a urine sample, the method comprising successively: - providing (802) a polyelectrolyte in a first solution, the polyelectrolyte being poly(methyl vinyl ether-alt-maleic anhydride), - adding (804) to the first solution a base to neutralize the polyelectrolyte and bring the first solution to a pH between 10 and H, - adding (806) to the first solution a buffering agent to bring and maintain the first solution at a pH between 7.0 and 7.5, - dipping (808) a paper strip (520) in the first solution, - dipping (814) the paper strip in a second solution comprising a pH-sensitive colored indicator.

2. The method of claim 1, further comprising at least one of the following: drying (810) the paper web after dipping (806) in the first solution and drying (816) the paper web after dipping (814) in the second solution.

3. A method according to claim 1 or 2, wherein the base is sodium hydroxide (NaOH).

4. A method according to claim 1 or 2, wherein the base is a mixture of sodium hydroxide (NaOH) and potassium hydroxide (KOH), preferably in a mass ratio of between 2.6 and 3.

5.

5. A method according to any one of claims 1 to 4, wherein the neutralization is carried out by titrating the polyelectrolyte until the first solution reaches a pH of between 10 and 11.

6. Method according to one of claims 1 to 4, in which the neutralization is carried out by a one-pot synthesis.

7. Method according to one of claims 1 to 6, in which the polyelectrolyte is neutralized to at least about 80%, preferably to more than 85%.

8. A method according to any one of claims 1 to 7, wherein the buffering agent is Tris(hydroxymethyl)aminomethane hydrochloride (Tris HCl), in particular a 1 M (mol / L) solution of Tris HCl.

9. A method according to any one of claims 1 to 8, wherein the pH-sensitive color indicator is bromothymol blue.

10. Test strip (500) for determining the specific gravity of a A urine sample made by the method of claims 1 to 9, the test strip determining the specific gravity of the urine sample based on the intensity of the color change of the pH-sensitive color indicator.

11. The test strip (500) of claim 10, further comprising a pH test block (540).

12. A cartridge (202) for an optical urine analysis device (100), the cartridge (202) comprising a plurality of chambers (310) arranged next to each other in the shape of a right circular cylinder of at least 80% of a circle with a diameter between 3 and 10 cm, wherein at least one chamber (310) comprises a test strip (500) according to claim 10 or 11.

13. The cartridge of claim 12, further comprising a pH measuring strip disposed in at least one chamber.

14. An optical urine analysis device (100) comprising: - a cartridge (202) according to claims 12 or 13, - a station (200), configured to be positioned on a wall of a toilet bowl (102), the station (200) comprising: + a housing (204) comprising a housing (212) in which the cartridge (202) is at least partially received, + an injector, configured to inject fluid onto the test strip (500), + an analyzer (400) for analyzing a color change of the strip (500) due to the liquid of the liquid sample.

15. The optical urine analysis device (100) of claim 14, wherein the analyzer (400) comprises a light source (402, 404) and a light sensor, configured to emit and receive light.

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