Apparatus for testing a blood sample for the concentration of certain IONS therein

Abstract

APPARATUS FOR TESTING A BLOOD SAMPLE FOR THE CONCENTRATION OF CERTAIN IONS THEREIN 5 The invention relates to an apparatus for testing a blood sample for the concentration of certain ions therein, comprising: a top layer of membrane (1) capable of filtering out all constituents of the sample except plasma; a middle layer of glass fibre (2) coated with an ion-selective complex which includes an ionophore (10), a cation exchanger (11) and a dye (12), for facilitating an interchange between 10 said certain ions (13) in the plasma and the dye (12); and a bottom layer which includes a milli-fluidic channel (4) along which the dye can travel, wherein the distance (16) travelled by the dye indicates the concentration of said certain ions in the sample. 15

Description

[0001] APPARATUS FOR TESTING A BLOOD SAMPLE FOR THE CONCENTRATION OF CERTAIN IONS THEREIN

[0002] FIELD OF THE INVENTION

[0003] This invention relates to an apparatus for testing a blood sample for the concentration of certain ions therein.

[0004] BACKGROUND OF THE INVENTION

[0005] Human body relies on metal ions for various biological functions and maintains a consistent level to maintain homeostasis. Regular monitoring of metal ion levels is crucial to ensure that the body is functioning normally. Deviations from the ideal level can lead to health problems and imbalances in bodily functions. Daily monitoring of metal ion levels is recommended to identify any changes early, allowing for prompt treatment and prevention of complications. Nowadays, clinical measurement of ion concentration is typically done through ion-selective electrodes using ionophore -based membranes. Although this method is dependable, it requires specialized equipment and is not practical for low -resource settings.

[0006] R. Daniel Johnson et. al. in their paper entitled "Ionophore-Based Ion-Selective Potentiometric and Optical Sensors" describes ion-selective electrodes (ISEs) and optodes with a focus on the fundamental mechanisms, response characteristics, and recognition elements (ionophores) described to date for these sensors.

[0007] Xiaojiang Xie et. al. in their paper entitled "Ion Selective Optodes: from the Bulk to the Nanoscale" describes recent advances in the miniaturization of ion selective optodes into microscale and nanoscale sensors.

[0008] Nonetheless, none of the above papers discloses an easy- and convenient-to-use solution to test a blood sample for certain ions therein, which can be employed under a low-resource setting. SUMMARY OF THE INVENTION

[0009] The above-mentioned drawbacks and difficulty are overcome by the invention elaborated in the paragraphs that follow.

[0010] One aspect of the invention provides an apparatus for determining the concentration of certain ions in a blood sample, comprising: a top layer of membrane capable of filtering out all constituents of the sample except plasma; a middle layer of glass fibre coated with an ion-selective complex which includes an ionophore, a cation exchanger and a dye, for facilitating an interchange between said certain ions in the plasma and the dye; and a bottom layer which includes a milli-fluidic channel along which the dye can travel, wherein the distance travelled by the dye indicates the concentration of said certain ions in the sample.

[0011] Advantageously, the apparatus integrates plasma separation from the sample, detection of certain ions in the plasma, and indication of the ion concentration into a single step, hence eliminating the need for solution transfer, and making the process more convenient and efficient.

[0012] Advantageously, the apparatus simplifies and speeds up the ion detection process, hence is more efficient.

[0013] Advantageously, the apparatus also provides a greater accuracy and convenience in detecting the concentration of ions in a blood sample.

[0014] Advantageously, the apparatus provides a distance-based analysis using the milli- fluidic channel which is independent of pH, and a straightforward ion exchange process using a dye which is insensitive to pH. Different from a conventional pH indicator-based optode, the apparatus operates without the participation of H+ ions in the ion exchange equilibrium. Hence, the test result of the apparatus is unaffected by any change in pH of the sample. Being pH independent, the apparatus is much more reliable and versatile in providing a precise and consistent analysis across diverse applications regardless of the pH condition of the sample.

[0015] Typically the concentration of ions is determined in vitro. Advantageously, the apparatus requires only a single drop of blood sample, hence is highly convenient for point-of-care diagnostics. More especially, the apparatus eliminates the need to use laboratory equipment in carrying out a blood test.

[0016] Typically, the complex is coated on the glass fibre by a polymer binder.

[0017] Typically, said bottom layer comprises a polymer plate on which said channel is configured, said channel being coated with silica gel powder for facilitating retention of dye-carrying plasma within said channel.

[0018] Advantageously, the TLC milli-fluidic channel ensures that liquid is well contained within the channel, which allows the liquid to flow better along the channel, and provides a more accurate and efficient result.

[0019] Advantageously, the membrane is capable of quickly and efficiently separating plasma from blood for on-the-spot analysis, thus eliminating the need for centrifugal separation which is time-consuming.

[0020] Advantageously, the apparatus provides a convenient and cost-effective solution for point-of-care testing, and is a promising apparatus for use in a setting with poor resources.

[0021] In one embodiment, the apparatus also comprises two annular members each being configured between any two of said adjacent layers spacing one layer from the other.

[0022] Typically, said bottom layer includes two marks indicating the lower and upper limits of the distance within which the concentration of said certain ions in the sample is considered normal.

[0023] In another embodiment, the apparatus also comprises a cover configured on top of said layers, wherein said cover includes: a hollow through which the distance is visible; another hollow aligned with said membrane, through which the sample can be dripped onto said membrane; and two marks indicating the lower and upper limits of the distance within which the concentration of the ions in the sample is considered normal.

[0024] Typically, the complex is capable of being customised for facilitating an interchange between certain ions in the plasma and a dye, by varying the combination of said ionophore, dye and cation exchanger. Typically, said dye is fluorescent, and said cation exchanger is lipophilic.

[0025] Typically, the apparatus is portable and useable at a point of care.

[0026] Advantageously, the apparatus is configured in a self-contained manner, hence is both easy to use and practical.

[0027] Another aspect of the invention provides a set of apparatuses each being the apparatus as described in the preceding paragraphs, wherein each complex of the apparatus is customised for facilitating an interchange between distinct ions in the plasma and a dye.

[0028] Advantageously, the set of apparatuses or the apparatus provides a fast and simple way to determine various medical conditions, hence is invaluable for medical professionals and researchers.

[0029] DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which:

[0031] Fig. 1 is an exploded view of the kit, according to the invention, for testing a blood sample for the concentration of certain ions therein;

[0032] Fig. 2 illustrates the mechanism, according to the invention, by which certain ions of the blood sample are captured by an ionophore coated on a glass fibre while a dye is released from the ionophore;

[0033] Fig. 3 shows the reference marks, according to the invention, defining a range within which the ions concentration in the blood sample is considered normal; and

[0034] Fig. 4 shows the kit, according to the invention, capable of detecting in a single step, a single type of ions (on the left) and multiple types of ions (on the right).

[0035] Referring to Figure 1, the kit comprises three main components, i.e. a plasma separator membrane 1, a glass fibre pad 2 coated with an ion-selective complex, and a polymer plate 3 on which a Thin-Layer Chromatography (“TLC”) millifluidic channel 4 is configured. The polymer can be Teflon. A ring 5 is configured between said membrane 1 and glass fibre pad 2, and another ring 6 between said glass fibre pad 2 and polymer plate 3, to provide a space between said membrane 1, glass fibre pad 2 and polymer plate 3. A cover 7 is configured on top of said membrane 1. Said cover 7 includes: a hollow 8 through which the channel 4 is visible; and another hollow 9 aligned with said membrane 1, through which a blood sample can be dripped onto said membrane 1.

[0036] The kit requires a single drop of blood sample for certain ions in the sample to be detected and the concentration thereof indicated. When in use, a drop of the sample is dripped onto said membrane 1. Capillary action and gravity help in transferring the sample from the top of said membrane 1 to said channel 4 by which the concentration of ions in the sample is indicated.

[0037] The plasma separator membrane 1 allows only plasma of the sample to pass through and filters out other constituents of the sample. The membrane 1 is made of a thin polymeric material which has a controlled pore size that allows only plasma to pass through while retaining other blood components such as red blood cells and platelets. The membrane 1 is built in a way such that capillary action and gravity is sufficient to replace the conventional centrifugal force needed to separate plasma from the blood sample.

[0038] Referring to Figure 2, the ion-selective complex coated on the glass fibre pad 2 comprises a combination of an ionophore 10, a lipophilic cation exchanger 11, and a fluorescent dye indicator 12. More specifically, the ionophore can be potassium ionophore, sodium ionophore, calcium ionophore or magnesium ionophore, the cation exchanger can be tetrakis[3,5-bis(trifluoromethyl)phenyl] borate salts, and the dye indicator can be Nile blue A or basic yellow 1. The ionophore 10 provides an excellent selectivity in capturing particular ions 13 from the plasma, while triggering the release of dye molecules 12 from the complex. This specificity results from the ability of the ionophore 10 to discriminate between ions, allowing it to capture only ions of interest 13 and disregard other ions. The coating enables quantitative ion-dye replacement, wherein certain ions in the plasma are replaced with the fluorescent dye in a quantifiable manner. By incorporating in the coating an ionophore which is highly selective of ions, specific ions in the sample can be targeted. By manipulating said combination, the coating on the glass fibre pad 2 provides the flexibility to selectively capture specific ions 13 from the plasma, hence enables identification of targeted ions, e.g. potassium, sodium, magnesium or calcium, in the sample.

[0039] Referring to Figure 4, the kit 14 on the left has been configured to test a blood sample for a single type of ions therein, whereas the set of kits 15 on the right comprises a plurality of kits, each of which has been configured to test a blood sample for a distinct type of ions therein. Such configuration is achieved by changing the combination of ionophore, cation exchanger, and dye indicator in the ion-selective complex.

[0040] The process of coating the ion-selective complex on the glass fibre pad involves the use of a polymer binder, e.g. plasticized polyvinyl chloride, or polyacrylamide, polyurethanes. This binder helps to hold the complex in place on the pad 2, ensuring that it remains stable and functional. The coating process helps to ensure that the ion-selective complex is evenly distributed across the surface of the pad 2, which ensures that ions interact effectively with the electrode surface, making the overall process efficient.

[0041] The coating is capable of achieving a high selectivity in either a mixed or separate solution of monovalent and divalent ions, in addition to being sustainably produced without toxic solvents. This coating has the potential to revolutionize ion detection, as it offers a more environment friendly and efficient approach compared to conventional methods.

[0042] As shown in Figure 1, the TLC milli-fluidic channel 4 is used for measuring the concentration of the ions quantitatively. Fabrication of the TLC milli-fluidic channel 4 comprises the steps of: drilling a milli-fluidic channel on a polymer plate 3; and coating the milli-fluidic channel with silica gel powder to transform the milli- fluidic channel into the TLC milli-fluidic channel 4. Compared to traditional wax printed channels, this particular design significantly increases the water retention and liquid diffusion capabilities of the channel. When the dye is in contact with the milli-fluidic channel, it will be absorbed onto the surface of the silica. As shown in Figure 3, the concentration of certain ions in the sample can be determined by measuring the distance 16 covered by a dye, as the length that the dye has travelled is directly proportional to the concentration of the ions in the sample. A longer distance indicates a higher concentration of the ions. Hence, the TLC milli-fluidic channel converts the ion concentration into a distance-based measure which is not only precise and accurate, but also easily interpreted. The distance 16 indicates the amount of dye released from the complex which accurately quantifies the concentration of the ions in the sample.

[0043] Referring to Figure 3, the kit comes with two reference marks 17, 18 that serve as a guide to determine whether the level of ions in the blood sample is normal. The reference marks 17, 18 are visual indicators that help healthcare providers in interpreting the result of a test accurately. If the distance 16 covered by the dye falls within the marks 17, 18, it indicates that the ion level in the blood sample is within the acceptable range. On the contrary, if the distance covered by the dye falls outside the marks 17, 18, it suggests that a further evaluation may be required to identify any underlying health issues or conditions. Therefore, certain medical conditions can be diagnosed and progress of a disease can be monitored from the test result.

[0044] The kit provides a simple, efficient, and accurate way to indicate the concentration of ions in the blood sample. The kit is capable of identifying and isolating specific ions, which could help in the diagnosis and treatment of relevant diseases.

[0045] The kit can detect the concentration of ions in a blood sample with ease, unlike the complicated process required for ICP-MS / OES. The latter requires expensive test equipment, trained personnel for sample collection and analysis, and complicated sample pre-processing. In contrast, the kit offers a straightforward solution that can accurately detect the ions concentration in the sample.

[0046] Unlike a conventional pH-sensitive optode sensor, the kit provides a distance-based analysis using the TLC milli-fluidic channel which is independent of pH, due to a simple ion exchange process and the use of a pH-insensitive dye as an indicator. When the kit is used to test a blood sample for the concentration of certain ions therein, the ion exchange equilibrium does not involve H+ ions, making it distinct from the conventional hydrogen chromo-ionophore or pH indicator-based optodes. Consequently, the readout signal obtained from the distance-based analysis can be expected to remain unaffected by changes in solution pH. This characteristic provides a reliable and consistent analysis platform, enabling accurate measurements regardless of the pH conditions. The combination of a straightforward ion exchange process and the utilization of a pH-insensitive dye enhances the robustness and versatility of the kit.

[0047] It will be appreciated by persons skilled in the art that the present invention may also include further additional modifications which does not affect the overall functioning thereof.

Claims

CLAIMS1. An apparatus for determining the concentration of certain ions in a blood sample, comprising: a top layer of membrane (1) capable of filtering out all constituents of the sample except plasma; a middle layer of glass fibre (2) coated with an ion-selective complex which includes an ionophore (10), a cation exchanger (11) and a dye (12), for facilitating an interchange between said certain ions (13) in the plasma and the dye (12); and a bottom layer which includes a milli-fluidic channel (4) along which the dye can travel, wherein the distance (16) travelled by the dye indicates the concentration of said certain ions in the sample.

2. The apparatus as claimed in claim 1, wherein the complex is coated on the glass fibre (2) by a polymer binder.

3. The apparatus as claimed in claim 2, wherein said bottom layer comprises a polymer plate (3) on which said channel (4) is configured, said channel (4) being coated with silica gel powder for facilitating retention of dye-carrying plasma within said channel (4).

4. The apparatus as claimed in claim 3, also comprising two annular members (5, 6) each being configured between any two of said adjacent layers spacing one layer from the other.

5. The apparatus as claimed in claim 4, wherein said bottom layer includes two marks (17, 18) indicating the lower and upper limits of the distance (16) within which the concentration of said certain ions in the sample is considered normal.

6. The apparatus as claimed in claim 4, also comprising a cover (7) configured on top of said layers, wherein said cover (7) includes: a hollow (8) through which the distance (16) is visible; another hollow (9) aligned with said membrane (1), through which the sample can be dripped onto said membrane (1); and two marks (17, 18) indicating the lower and upper limits of the distance (16) within which the concentration of the ions in the sample is considered normal.

7. The apparatus as claimed in claim 6, wherein the complex is capable of being customised for facilitating an interchange between certain ions (13) in the plasma and a dye (12), by varying the combination of said ionophore (10), dye (12) and cation exchanger (11).

8. The apparatus as claimed in claim 7, wherein said dye (12) is fluorescent, and said cation exchanger (11) is lipophilic.

9. The apparatus as claimed in claim 8, being portable and useable at a point of care.

10. A set of apparatuses (15) each being the apparatus as claimed in claim 7, wherein each complex of the apparatus is customised for facilitating an interchange between distinct ions in the plasma and a dye.

Images