Device for quantifying analyte in liquid sample

Abstract

The present disclosure relates to an electrochemical sensing device for quantifying an analyte in a liquid sample, comprising: a substrate; a plurality of electrodes disposed on the substrate, one of the plurality of electrodes being functionalized with a catalyst, the catalyst including an inorganic compound; and a hydrophilic channel disposed on the substrate, the hydrophilic channel configured to receive a liquid sample and direct the liquid sample to the electrode.

Description

Technical Field

[0001] The present technology relates to an apparatus for quantifying an analyte in a liquid sample. Background Art

[0002] Enzyme electrochemical sensors are one of the most commercially successful biosensing technologies for quantifying analytes in liquid samples. In particular, this technology has been widely used in home blood glucose test strips for monitoring the chronic diseases of diabetic patients. This example demonstrates the potential of electrochemical assays in rapidly and accurately quantifying analytes suitable for enzymatic reactions. However, the enzymes used as catalysts in traditional enzyme electrochemical sensors exhibit low stability under environmental conditions, and more importantly, have limited sensitivity in quantifying low-abundance molecules. An example is the quantification of glucose in human saliva - the concentration of glucose in saliva is much lower than that in blood and cannot be accurately quantified using existing enzyme electrochemical biosensor technologies. If saliva can be used to accurately quantify the glucose level of a human subject, a non-invasive method for managing the diabetic condition of human patients will be achieved.

[0003] Therefore, it is desirable to improve the reliability and sensitivity of the apparatus for quantifying analytes in liquid samples. Summary of the Invention

[0004] In view of the above, one aspect of the present technology provides an electrochemical sensing apparatus for quantifying an analyte in a liquid sample, comprising: a substrate; a plurality of electrodes disposed on the substrate, one of the plurality of electrodes being functionalized with a catalyst, the catalyst comprising an inorganic compound; and a hydrophilic channel disposed on the substrate, the hydrophilic channel being configured to receive the liquid sample and direct the liquid sample to the electrodes.

[0005] According to an embodiment of the present technology, there is provided an electrochemical sensing apparatus for quantifying an analyte (such as glucose) in a liquid sample (such as blood or saliva). In use, the liquid sample is deposited on the hydrophilic channel, for example, at a dedicated sample inlet or window exposing the hydrophilic channel. Then, the liquid sample is transported along the hydrophilic channel to the plurality of electrodes where measurements can be made. One of the plurality of electrodes is equipped with and functionalized by an inorganic catalyst that reacts with the analyte in the liquid sample, enabling the determination of the concentration or amount of the analyte. Compared with traditional enzyme catalysts, inorganic catalysts exhibit higher stability under environmental conditions, and more importantly, have higher sensitivity to low concentrations of analytes. By using inorganic catalysts, low-concentration analytes (such as glucose in saliva) can be quantified, and the resulting sensing apparatus has better stability.

[0006] In terms of glucose quantification, compared to glucose oxidase, copper oxide, as an inorganic alternative, exhibits high sensitivity and high specificity at lower concentrations. Thus, in some embodiments, the inorganic compound can include copper oxide. In other embodiments, the inorganic compound can include other metal oxides such as cobalt oxide, nickel oxide, iron oxide, or zinc oxide.

[0007] For certain inorganic catalysts, their high-performance potential depends on the acidity and alkalinity (pH) of the solution with which they react. For example, copper oxide performs well in glucose quantification, but the technique requires the local pH value of the solution to be within a specific range near the functionalized electrode where the catalyst is deposited. While serum pH is typically stable around the physiological range (~7.4), saliva pH varies from person to person and also varies significantly for the same person at different times of the same day, depending on food or beverage intake or oral health. Thus, in some cases, directly replacing the enzyme catalyst with an inorganic catalyst on a simple screen-printed electrode strip (such as those used in existing enzyme electrochemical blood glucose meters) may not be sufficient. Accordingly, in some embodiments, the device can further include a pH control system disposed near the plurality of electrodes, the pH control system configured to control the acidity / alkalinity of at least one region surrounding the functionalized electrode. By doing so, the acidity and / or alkalinity around the functionalized electrode can be locally controlled, enabling the use of catalysts that may be sensitive to pH changes.

[0008] In some embodiments, the plurality of electrodes can include at least a working electrode, a counter electrode, and a reference electrode, wherein the pH control system can be disposed near the working electrode.

[0009] In some embodiments, the pH control system can include a set of pH control electrodes.

[0010] In some embodiments, the set of pH control electrodes can include a pH sensing electrode and an active pH control electrode.

[0011] The pH sensing electrode can take a variety of different suitable forms. In some embodiments, the pH sensing electrode can include an ion-selective sensing device or an ion-sensitive extended gate electrode arranged to be able to measure the pH value for an electronic reading.

[0012] Similarly, the active pH control electrode can take a variety of different suitable forms. In some embodiments, the active pH control electrode can include a quinone-functionalized electrode configured to electrochemically induce electrons or protons at least around the functionalized electrode. In other embodiments, the active pH control electrode can be configured to act as a controlled release valve for an alkaline source stored on the device.

[0013] In some embodiments, the pH control system may be configured to communicate with and be controlled by an electronic reader implementing a predetermined pH calibration algorithm.

[0014] In some embodiments, each of the plurality of electrodes may extend into an electrical connection pad configured to interface with the electronic reader.

[0015] In some embodiments, the plurality of electrodes may include at least a working electrode, a counter electrode, and a reference electrode, wherein the plurality of electrodes may be arranged such that when a potential is applied between the working electrode and the reference electrode, a current is measured through the counter electrode.

[0016] In some embodiments, the functionalized electrode may be the working electrode, on which a catalyst may be deposited.

[0017] The hydrophilic channel may take many different suitable forms as needed. In some embodiments, the hydrophilic channel may be formed of paper. In other embodiments, the hydrophilic channel may be formed by lithography in a dry film photoresist.

[0018] In some embodiments, the hydrophilic channel may be formed with a surface micro-pattern configured to facilitate the diffusion of a liquid sample, for example, after a chemical or plasma-induced hydrophilization treatment.

[0019] In some embodiments, the substrate may include a printed circuit board. In some embodiments, the printed circuit board on which the plurality of electrodes, the hydrophilic channel, and optionally the pH control system are provided may be encapsulated in a housing (such as a plastic housing) to protect the various components of the electrochemical sensing device. An opening or window may be formed in the housing to allow access to a portion of the hydrophilic channel to enable the hydrophilic channel to receive a liquid sample. A second opening or window may be formed in the housing to allow access to the plurality of electrodes (and optionally the pH control system) to enable interfacing with, for example, an electronic reader.

[0020] Embodiments of the present technology each have at least one of the above objects and / or aspects, but not necessarily all of them. It should be understood that certain aspects of the present technology may not meet the object due to attempting to achieve the above object and / or may meet other objects not specifically recited herein.

[0021] Additional and / or alternative features, aspects, and advantages of embodiments of the present technology will become apparent from the following description, drawings, and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments will now be described with reference to the drawings, wherein:

[0023] Figure 1 An exemplary electrochemical sensing device according to an embodiment of the present technology is shown;

[0024] Figure 2 shows another exemplary electrochemical sensing device;

[0025] Figure 3 schematically shows an embodiment of a pH control system; and

[0026] Figure 4A and Figure 4B shows the effect of the pH of a liquid sample on the measured results generated between two analytes. Detailed Description

[0027] The inventors of the present technology recognized that enzymes used as catalysts in traditional enzyme electrochemical sensors exhibit low stability under environmental conditions, and more importantly, have limited sensitivity in the quantification of low-abundance molecules.

[0028] This method replaces the organic enzyme catalyst (such as glucose oxidase) in a traditional enzyme electrochemical sensor with an inorganic catalyst (such as copper oxide). The inorganic catalyst is sensitive to lower concentrations of analytes and has considerable selectivity for the target analyte when properly designed and operated. Therefore, this method can provide a device / system that can quantify analytes suitable for enzyme assays within a much lower sensitivity range than traditional possible sensitivity ranges.

[0029] Embodiments of the present technology provide improved electrochemical sensing devices for quantifying analytes (such as glucose) in liquid samples (such as blood or saliva). Embodiments of the device include a substrate, a plurality of electrodes disposed on the substrate (including electrodes functionalized with an inorganic catalyst), and hydrophilic channels disposed on the substrate for receiving a liquid sample and guiding the liquid sample to the electrodes.

[0030] In use, a liquid sample is deposited on the hydrophilic channels, such as at a sample inlet that exposes the hydrophilic channels. Then, the liquid sample is transported along the hydrophilic channels to the plurality of electrodes where measurements can be made. One of the plurality of electrodes is functionalized with an inorganic catalyst that reacts with the analyte in the liquid sample, enabling quantification of the analyte. Compared to traditional enzyme catalysts, the inorganic catalyst exhibits higher stability under environmental conditions and higher sensitivity to low concentrations of analytes. By using an inorganic catalyst, quantification of low-concentration analytes can be achieved, and the resulting sensing device has better stability.

[0031] Figure 1Shows an exemplary electrochemical sensing device 100 according to an embodiment of the present technology. Device 100 includes a substrate 109, and the components of device 100 are disposed on substrate 109. Substrate 109 can be formed of any suitable material as needed, and in one embodiment, substrate 109 can include a printed circuit board (PCB), and in another embodiment, substrate 109 can be a base (e.g., plastic) for screen printing strips (e.g., for glucose quantification). In the present embodiment, device 100 is implemented by flexible PCB laboratory technology.

[0032] Device 100 includes a hydrophilic channel 101 disposed on substrate 109. Hydrophilic channel 101 has an inlet 102 at one end for receiving a liquid sample and a sensing region at the end opposite to inlet 102. In the present embodiment, inlet 102 is wider than the rest of hydrophilic channel 101 to enable easy deposition of the liquid sample, but this is not necessarily the case; in other embodiments, the width of inlet 102 can be the same as the width of the rest of hydrophilic channel 101. When the liquid sample is deposited on inlet 102, hydrophilic channel 101 passively transports the liquid sample along its length to the sensing region by diffusion, and a plurality of electrochemical sensing electrodes 103a, 104a, 105a are disposed on the sensing region.

[0033] In the present embodiment, the plurality of electrochemical sensing electrodes 103a, 104a, 105a include a working electrode (WE) 103a, a reference electrode (RE) 104a, and a counter electrode (CE) 105a. An inorganic catalyst material (e.g., copper oxide nanoparticles) is deposited on the surface of the WE, for example, by drop casting or printing from a solution and drying to functionalize the WE. Sensing electrodes 103a, 104a, 105a are formed as conductive tracks plated with an inert metal (e.g., gold). The conductive tracks enable good current conduction, e.g., towards an instrument electrically connected to the electrodes, and the inert metal plating reduces adverse chemical reactions between the electrodes and the liquid sample. In some embodiments, in addition to the inert metal plating, if needed, the inorganic catalyst can also be encapsulated with a suitable material to improve stability and / or signal amplification. Each of the conductive tracks forming WE 103a, RE 104a, and CE 105a extends towards the edge of device 100 to corresponding connection pads 103b, 104b, 105b, which are arranged to be electrically connected to, for example, an electronic reader 120 through a suitable connection (e.g., a cable) 110. When device 100 is in use, a potential is applied between WE 103a and RE 104a (e.g., by electronic reader 120 through connection pads 103b and 104b), and the resulting current is read through CE 105a, e.g., by electronic reader 120 through connection pad 105b.

[0034] In this embodiment, the device 100 is further provided with a pH control system which, in this example, includes a set of pH control electrodes 106a, 107a disposed on the substrate 109 and located at the same end as a plurality of electrodes 103a, 104a, 105a adjacent to the WE 103a. This set of pH control electrodes includes a pH sensing electrode (PHSE) 106a and an active pH control electrode (PHCE) 107a, which extend into connection pads 106b and 107b respectively, and the connection pads are arranged to be in electrical interface with the electronic reader 120.

[0035] The PHSE 106a can be any suitable commercially available ion-selective sensing device as required. For example, the PHSE 106a can be an ion-sensitive field effect transistor (ISFET) or an ion-sensitive extended gate field effect transistor, such as ITO, ZnO, parylene, etc. The pHCE 107a can be, for example, a quinone-functionalized electrode for electrochemically inducing local release of electrons or protons at the electrode. The pHCE 107a can alternatively be configured to act as a controlled release valve for an alkaline source (such as NaOH) stored on the chip.

[0036] In this embodiment, the PHSE 106a and the pHCE 107a are controlled by an electronic reader that implements a predetermined sensor pH calibration algorithm thereon. The sensor pH calibration algorithm defines the operating pH value (or range of operating pH values) suitable for the chemical reaction between the analyte in the liquid sample and the inorganic catalyst on the WE 103a, and defines the instructions for controlling the pHCE 107a based on the pH value measured at the PHSE 106a in order to achieve the desired pH value or range of pH values. Therefore, based on the pH value read at the PHSE 106a and the specific properties of the non-enzymatic inorganic catalyst on the WE 103a, the device 100 adjusts the pH value of the sample liquid in the area around the WE 103a by an algorithm to adapt to the sensitivity and selectivity of the WE 103a, thereby achieving electronically tunable sensing of different analytes.

[0037] The hydrophilic channel 101 can be formed through paper in a hybrid implementation manner, or formed in a seamless integration manner via lithography through a dry film photoresist. In the latter case, a hydrophilization process can be performed after formation, including, for example, oxygen plasma treatment inside the micro-pattern.

[0038] Figure 2 An exemplary micro-patterned hydrophilic channel 201 is shown. In this embodiment, the diamond micro-patterns 200-1, 200-2, 200-3 contribute to the passive (i.e., without applying external pressure) flow of the liquid sample from the inlet 202 towards the sensing area at the opposite end of the channel 201. Of course, other shapes of micro-patterns other than this diamond can be used as required, including the same shape or a combination of two or more shapes.

[0039] In various embodiments, the hydrophilic channel (e.g., hydrophilic channel 101) can range in size from 250 μm wide to 1 mm, as defined by manufacturing limitations as needed. The length and thickness of the hydrophilic channel can be determined by the sample volume of the expected liquid sample that the hydrophilic channel needs to accommodate for analysis and quantification, and the sample volume can be defined by the clinical concentration range of the target analyte in the liquid sample and the molecular diffusion time of the analyte into the working electrode region.

[0040] In an exemplary embodiment, copper oxide (e.g., copper oxide in the form of nanoparticles) is used as an inorganic substitute for glucose oxidase in glucose analysis because it has sensitivity and improved specificity at lower analyte (glucose) concentrations. However, due to the technical requirement of precisely controlling the acidity / alkalinity of the liquid sample locally deposited on the WE, the potential of copper oxide as an alternative catalyst has not been adopted in practice. In the case of glucose analysis by a blood sample, the serum pH value is mostly stable around the physiological range (7.4), so active pH control is not required. However, the pH value of human saliva varies from person to person and also varies significantly for the same person over time due to food or beverage intake and oral health. When using copper oxide, the change in pH value can lead to inaccurate or uncertain glucose analysis of saliva samples. In this case, a pH control system, such as the pH control system including pHSE 106a and pHCE 107a, can be implemented in the embodiments of the present technology to measure and actively control the acidity / alkalinity of the liquid sample adjacent to the WE 103a.

[0041] Figure 3 The sensing area of the device 100 as seen from the side is shown, showing the pH control mechanism performed by the PHSE 106a and PHCE 107a, which is controlled by an electronic reader 120 through a pH control algorithm. As described above, the WE 103a located between the PHSE 106a and PHCE 107a is functionalized with an inorganic catalyst that is capable of chemically reacting with the target analyte (e.g., glucose molecules). In this embodiment, the inorganic catalyst can be copper oxide (CuO) nanoparticles 300. In use, the PHSE 106a enables the external electronic reader 120 to electronically read the pH value of the liquid sample. The electronic reader 120 implements a pH control algorithm that defines the instructions for providing an electronic signal stimulus (e.g., voltage or current) to the PHCE 107a. The amplitude of the electronic signal stimulus is determined by (e.g., proportional to) the pH value measured at the PHSE 106a, and the electronic signal stimulus causes the PHCE 107a to locally release protons to the WE 103a, thereby locally adjusting the acidity / alkalinity to a predetermined level (e.g., a predetermined pH value).

[0042] Figure 4A and Figure 4B shows the specificity of copper oxide for glucose and lactic acid at different acidity / alkalinity. As Figure 4A shown, when the pH value of the solution is adjusted to 8, copper oxide can be used as an inorganic catalyst in the above-mentioned electrochemical sensing device to accurately quantify glucose. On the other hand, as Figure 4B shown, when the pH value of the solution is adjusted to 7.5, the above device can accurately quantify lactic acid.

[0043] The example and conditional language described herein are intended to assist the reader in understanding the principles of the present technology, rather than limiting its scope to these specifically described examples and conditions. It should be understood that those skilled in the art can design various arrangements, although not explicitly described or shown herein, which embody the principles of the present technology and are included within the scope defined by the appended claims.

[0044] In addition, for the sake of understanding, the above description may describe relatively simplified embodiments of the present technology. Those skilled in the art will understand that various embodiments of the present technology may have greater complexity.

[0045] In some cases, examples of modifications considered useful for the present technology may also be listed. This is done solely to assist understanding and not to limit the scope of the present technology or to clarify its boundaries. These modifications are not an exhaustive list, and those skilled in the art can make other modifications while still remaining within the scope of the present technology. Additionally, if no modified embodiments are listed, it should not be construed that modifications are not possible and / or that the described content is the only way to implement this element of the present technology.

[0046] In addition, all statements herein reciting the principles, aspects, and embodiments of the present technology, as well as its specific examples, are intended to cover their structural and functional equivalents, whether currently known or developed in the future.

[0047] It is obvious to those skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present technology.

Claims

1. An electrochemical sensing device for quantifying an analyte in a liquid sample, comprising: a substrate; a plurality of electrodes disposed on the substrate, one of the plurality of electrodes being functionalized with a catalyst, the catalyst comprising an inorganic compound; and a hydrophilic channel disposed on the substrate, the hydrophilic channel being configured to receive the liquid sample and direct the liquid sample to the electrodes.

2. The device according to claim 1, wherein the inorganic compound comprises a metal oxide, including one or more of copper oxide, cobalt oxide, nickel oxide, iron oxide, or zinc oxide.

3. The device according to any one of the preceding claims, further comprising a pH control system disposed near the plurality of electrodes, configured to control the acidity / alkalinity of at least one region around the functionalized electrode.

4. The device according to claim 3, wherein the plurality of electrodes at least comprises a working electrode, a counter electrode, and a reference electrode, and the pH control system is disposed near the working electrode.

5. The device according to claim 3 or 4, wherein the pH control system comprises a set of pH control electrodes.

6. The device according to claim 5, wherein the set of pH control electrodes comprises a pH sensing electrode and an active pH control electrode.

7. The device according to claim 6, wherein the pH sensing electrode comprises an ion-selective sensing device or an ion-sensitive extended gate electrode arranged to be able to measure the pH value with an electronic reading.

8. The device according to claim 6 or 7, wherein the active pH control electrode comprises a quinone-functionalized electrode configured to electrochemically induce electrons or protons around at least the functionalized electrode.

9. The device according to claim 6 or 7, wherein the active pH control electrode is configured to act as a controlled release valve for an alkaline source stored on the device.

10. The device according to any one of claims 3 to 9, wherein the pH control system is configured to communicate with and be controlled by an electronic reader implementing a predetermined pH calibration algorithm.

11. The device according to any one of the preceding claims, wherein each of the plurality of electrodes extends into an electrical connection pad configured to interface with an electronic reader.

12. The device according to any one of the preceding claims, wherein the plurality of electrodes at least comprises a working electrode, a counter electrode, and a reference electrode, wherein the plurality of electrodes are arranged such that when a potential is applied between the working electrode and the reference electrode, current is measured through the counter electrode.

13. The device according to claim 12, wherein the functionalized electrode is the working electrode and the catalyst is deposited thereon.

14. The device according to any one of the preceding claims, wherein the hydrophilic channel is formed of paper.

15. The device according to any one of the preceding claims, wherein the hydrophilic channel is formed by lithography in a dry film photoresist.

16. The device according to any one of the preceding claims, wherein the hydrophilic channel is formed with a surface micro-pattern configured to facilitate the diffusion of the liquid sample.

17. The apparatus according to any one of the preceding claims, wherein the substrate comprises a printed circuit board.

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