Magnetic bead microfluidic channel electrochemical detection device based on magnetic field modulation

Abstract

The application discloses a kind of based on magnetic field modulation's magnetic bead microchannel electrochemical detection device, including support, electromagnet, microchannel electrode sheet, control module;Electromagnet and microchannel electrode sheet are fixed on support;Microchannel electrode sheet is equipped with the U-shaped microchannel of two ends opening, and the inner wall of U-shaped microchannel is equipped with the oxidation working electrode and reduction working electrode opposite in position;The distance between oxidation working electrode and reduction working electrode is 10-1000 μm;Electromagnet is controlled to control module;When working, electromagnet produces periodic change magnetic field by the control of control module, and the U-shaped microchannel of microchannel electrode sheet is located in periodic change magnetic field.This application based on magnetic field modulation's magnetic bead microchannel electrochemical detection device, improve the upper limit of modulation frequency, can avoid numerous noise of low frequency band, and microchannel structure makes that electrochemical reaction is carried out in closed environment, avoids the disturbance of external air flow and other factors and introduces noise, improves the final signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of electrochemical detection technology, and in particular to a magnetic bead microchannel electrochemical detection device based on magnetic field modulation. Background Technology

[0002] Magnetic beads, used in the biomedical field, possess extremely high specific surface area, superparamagnetism, zero coercivity, and no hysteresis. Their surfaces can be combined with various organic and inorganic substances as needed, making them suitable for a wide range of detection scenarios. Because the magnetic force is non-contact and unaffected by chemical variables (such as pH, concentration, or surface charge), magnetic beads offer significant advantages in analytical applications.

[0003] Modified magnetic beads are dispersed into the sample. The modified components on the surface of the beads can capture the analytes in the sample. Applying an external magnetic field can collect the beads again, separating the analytes from the sample. The beads are then dispersed in a washing solution, and after washing for a period of time, they are collected again using an external magnetic field. The magnetic properties of the beads facilitate the separation and purification of analytes from the sample. Then, using an external magnetic field, the beads are enriched onto the electrode surface to undergo an electrochemical reaction for detection. The high specific surface area of ​​the magnetic beads and the enrichment effect caused by the magnetic field force result in more reactants participating in the electrochemical reaction, leading to a larger electrical signal. Therefore, this type of electrochemical sensor has high sensitivity.

[0004] However, traditional magnetic bead electrochemical sensors also have their detection limits. In low-concentration scenarios where the number of magnetic beads or the amount of analyte modified on the magnetic beads is very small, the generated electrical signal is submerged in noise and cannot be estimated, reaching the detection limit of traditional magnetic bead electrochemical sensors. At this time, a method is needed to further improve its detection limit and solve the detection problem in low-concentration scenarios.

[0005] Chinese patent document CN 115420790 A discloses a magnetic field-modulated electrochemical detection method for magnetic beads. This method utilizes a periodically changing magnetic field to control the periodic contact of magnetic beads with the electrode surface, thereby forming a periodically changing electrochemical response signal. The periodic characteristics of this electrochemical response signal are then used to detect frequency characteristic signals through a weak signal detection method, achieving electrochemical detection of trace amounts of magnetic beads or trace analytes on the electrode surface. Figure 1As shown, the magnetic beads in this invention can be composed of a magnetic core 103 made of metal oxides such as iron, cobalt, and nickel, and a shell 104 made of materials such as polymers, silicon, and hydroxyapatite surrounding the magnetic core. The surface of the magnetic beads can be modified, and the modifier 105 serves as a detection target or an electron mediator participating in the electrochemical reaction. The specific modification material needs to be determined according to the actual detection requirements. For example, the surface of the magnetic beads can be modified with antibodies, DNA, etc., thus enabling its application in immunoassay analysis. The magnetic beads are periodically contacted with the electrode surface by a periodically changing magnetic field: when the magnetic field force is upward 106, the magnetic beads are carried away from the electrode surface 101, and the electrochemical reaction stops 107. The magnetic beads remain at the gas-liquid interface 108 of the electrochemical reaction system, and due to the surface tension, the magnetic beads will not be attracted away. When the magnetic field force is downward 109, the magnetic beads contact the electrode surface 101, and the electrochemical reaction begins 110. The periodic contact of the magnetic beads with the electrode surface creates a periodic electrochemical response signal 102. This modulates the electrochemical signal from a traditional DC signal into a periodic AC signal, giving it a second characteristic in addition to its amplitude: frequency. Therefore, even if a weak periodic AC signal is submerged in loud noise, it can still be detected based on its frequency characteristic, enabling the electrochemical detection of trace amounts of magnetic beads or trace analytes on the electrode surface and improving the detection limit of traditional magnetic bead electrochemical sensors.

[0006] However, traditional magnetic field-modulated electrochemical detection devices for magnetic beads have the following drawbacks: 1) They typically use planar electrodes, on which a reaction solution is dropped. The magnetic bead moves up and down within the droplet, generating a modulation signal. Due to the height of the droplet (3-5 mm), the distance the magnetic bead travels is long, limiting the modulation frequency. In the low-frequency range, noise is high, and the low modulation frequency reduces the signal-to-noise ratio; 2) They usually have only one working electrode, on which a constant oxidation or reduction potential is applied. As the experiment progresses, the analyte carried on the magnetic bead is consumed by the oxidation or reduction reaction, causing the modulation signal to gradually weaken and affecting the experimental results; 3) The electrodes and droplets are exposed to the external environment, making them susceptible to disturbances such as airflow, introducing new noise; 4) Traditional devices generate heat during prolonged operation, affecting device operation and even damaging the device. Summary of the Invention

[0007] This invention provides a magnetic bead microchannel electrochemical detection device based on magnetic field modulation, which improves the upper limit of the modulation frequency, avoids many noises in the low frequency band, and the microchannel structure allows the electrochemical reaction to take place in a closed environment, avoiding the introduction of noise by external airflow and other factors, thus improving the final signal-to-noise ratio.

[0008] The technical solution of the present invention is as follows:

[0009] A magnetic bead microchannel electrochemical detection device based on magnetic field modulation includes a support, an electromagnet, microchannel electrode sheets, and a control module;

[0010] The electromagnet and microfluidic electrode sheet are fixed on the support;

[0011] The microfluidic electrode sheet is provided with a U-shaped microfluidic channel with openings at both ends. An oxidation working electrode and a reduction working electrode are provided on the inner wall of the U-shaped microfluidic channel, which are positioned opposite each other. The distance between the oxidation working electrode and the reduction working electrode is 10-1000μm.

[0012] The electromagnet is controlled by the control module; during operation, the electromagnet generates a periodically changing magnetic field under the control of the control module, and the U-shaped microchannel of the microchannel electrode plate is located within the periodically changing magnetic field.

[0013] During operation, the test solution containing modified magnetic beads is placed in a U-shaped microchannel. An oxidation potential is applied to the oxidation working electrode, and a reduction potential is applied to the reduction working electrode. Under the control of the control module, an electromagnet generates a periodically changing magnetic field in the U-shaped microchannel. Under the action of the periodic magnetic field, the modified magnetic beads move back and forth between the oxidation and reduction working electrodes in the U-shaped microchannel. When the modified magnetic beads move to the oxidation working electrode, an oxidation reaction occurs on the oxidation working electrode, and an oxidation current is output. When they move to the reduction working electrode, a reduction reaction occurs on the reduction working electrode, and a reduction current is output.

[0014] During operation, the modified magnetic beads reciprocate between the oxidation and reduction working electrodes within the U-shaped microchannel. The distance between the oxidation and reduction working electrodes is 10-1000 μm, much smaller than the existing droplet height (3-5 mm), which significantly increases the upper limit of the modulation frequency and avoids many low-frequency noises. Moreover, the microchannel structure allows the electrochemical reaction to take place in a closed environment, avoiding noise introduced by external factors such as airflow, thus improving the final signal-to-noise ratio. Within one cycle of the modified magnetic beads, two complementary signals, oxidation and reduction, are generated, further improving the analyzability of the modulation signal. Furthermore, the oxidation and reduction reactions alternate periodically, preventing the analyte from being consumed, allowing the experiment to be conducted for extended periods and yielding more accurate results.

[0015] The U-shaped microchannel is also equipped with a reference electrode and a counter electrode.

[0016] Preferably, the electromagnet includes a first electromagnet and a second electromagnet, which are located on opposite sides of the microfluidic electrode sheet; the first electromagnet is closer to the oxidation working electrode, and the second electromagnet is closer to the reduction working electrode.

[0017] Preferably, the support is a lifting support, and the two electromagnets and the microchannel electrode sheet are detachably fixed on the lifting support.

[0018] The lifting bracket can precisely adjust the relative distance between the electromagnet and the microfluidic electrode plate, making it easy to debug the most suitable distance for the experiment. It also allows for easy installation and removal of the electromagnet, facilitating the maintenance of the device later.

[0019] Electromagnets are prone to overheating during prolonged operation, which can weaken the magnetic field or even damage it. Preferably, the magnetic bead microchannel electrochemical detection device of the present invention is also equipped with a cooling device for cooling the electromagnet.

[0020] Preferably, the cooling device includes a hollow spiral tube covering the electromagnet, a connecting pipe, a coolant storage tank, and a circulation pump; the hollow spiral tube, the connecting pipe, and the coolant storage tank form a closed loop for coolant circulation, and the circulation pump is used to drive the coolant to circulate within the closed loop.

[0021] Preferably, the hollow spiral tube is a copper tube; the gap between the hollow spiral tube and the electromagnet is filled with thermally conductive silicone grease.

[0022] The excellent thermal conductivity of the copper tube and thermally conductive silicone grease ensures sufficient heat exchange between the electromagnet and the coolant. The cooling device solves the problem of overheating during prolonged operation of the electromagnet, enabling it to generate a stable, periodically changing magnetic field over a long period, thus allowing the magnetic bead microchannel electrochemical detection device of this invention to operate stably for extended periods.

[0023] The control module includes a relay, a variable DC power supply, and a microcontroller. The variable DC power supply allows setting the magnetic field strength generated by the electromagnet by adjusting the power supply voltage, facilitating the adjustment to a suitable magnetic field strength for the experiment. The microcontroller controls the relay connected to the variable DC power supply, controlling the electromagnet to periodically switch on and off, generating a periodically changing magnetic field. The required period for the experiment can also be set via the microcontroller.

[0024] During operation, the periodic electrochemical signals generated by the microfluidic electrode are transmitted to the electrochemical workstation for subsequent data processing.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The magnetic bead microchannel electrochemical detection device of the present invention abandons the traditional planar electrode and arranges the electrode in the microchannel, which greatly shortens the path of the modulation magnetic bead movement and increases the upper limit of the modulation frequency. The high modulation frequency can avoid many noises in the low frequency band. Moreover, the microchannel structure allows the electrochemical reaction to be carried out in a closed environment, avoiding the disturbance of external airflow and other factors that introduce noise, and improving the final signal-to-noise ratio.

[0027] (2) An oxidation working electrode and a reduction working electrode are set at both ends of the magnetic bead's movement path, and an oxidation potential and a reduction potential are applied respectively, so that the modifier on the magnetic bead undergoes periodic alternating oxidation and reduction reactions. The modifier will not be consumed as the experiment proceeds, so that the experiment can be carried out stably for a long time. Moreover, the two working electrodes generate two complementary current signals, which improves the analyzability of the modulated signal compared with the single signal of the traditional device.

[0028] (3) The periodic magnetic field is generated by using an electromagnet, which has no mechanical vibration and does not introduce new noise signals. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an existing magnetic field-modulated electrochemical detection method for magnetic beads.

[0030] Figure 2 This is a schematic diagram of a magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to an embodiment of the present invention;

[0031] Figure 3 The diagram shows the structure of the microchannel electrode sheet, where (a) is the overall structure diagram and (b) is the cross-sectional diagram.

[0032] Figure 4 A schematic diagram of the heat dissipation structure for an electromagnet.

[0033] Figure 5 This is a schematic diagram of the lifting support structure. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0035] like Figure 2 As shown, the magnetic field modulated electrochemical detection device for magnetic beads proposed in this invention consists of a microchannel electrode sheet 200, an electromagnet 201, a lifting support 202, a water cooling device 203, an electromagnet control module 204, and an electrochemical workstation 205.

[0036] like Figure 3As shown in (a) and (b), the microfluidic electrode 200 comprises four electrodes: a primary working electrode 2001, a secondary working electrode 2002, a reference electrode 2003, and a counter electrode 2004. In use, a solution containing modified magnetic beads fills the U-shaped microfluidic channel 2005. The height of the microfluidic channel 2005 can be designed to be tens to hundreds of micrometers, significantly reducing the distance the magnetic beads travel. From the outside, the microfluidic channel has only one pair of inlets and outlets 2006, allowing the electrochemical reaction to occur almost entirely within a closed space, isolating it from external disturbances. The four electrodes within the microfluidic channel 2005 are connected by wiring to an interface 2007 at the other end, facilitating the reading and acquisition of electrochemical signals. An oxidation potential can be applied to the primary working electrode 2001, and a reduction potential can be applied to the secondary working electrode 2002. When the modified magnetic bead is driven by the magnetic field to move onto the first working electrode 2001, an oxidation reaction occurs, outputting an oxidation current; when it moves to the second working electrode 2002, a reduction reaction occurs, outputting a reduction current. Two complementary signals are generated within one cycle of the magnetic bead's movement, further improving the analyzability of the modulated signal. Furthermore, the periodic alternation of the oxidation and reduction reactions prevents the analyte from being consumed, allowing the experiment to be conducted for extended periods and yielding more accurate results.

[0037] There are two types of magnetic bead electrochemical detection devices with magnetic field modulation: push-pull permanent magnet type and electromagnet type. Due to the use of microfluidic structure, the mechanical movement of push-pull permanent magnet type is prone to vibration, which is not suitable for electrode plates with microfluidic structure. Electromagnet type has no mechanical movement and is suitable for use in this scenario.

[0038] Because electromagnets tend to heat up during prolonged operation, which can weaken the magnetic field or even damage the device, such as... Figure 4As shown, the electromagnet 201 designed in this invention has a heat dissipation function. Copper wire with an insulating layer is wound into a dense energized coil 2011 in one direction, and the two ends of the energized coil are led out. On the outside of the energized coil 2011, a hollow copper tube 2012 is tightly wound into a spiral shape. The gap between the energized coil 2011 and the copper tube 2012 is filled with thermally conductive silicone grease. The iron core 2013 of the electromagnet is made of silicon steel rod with low coercivity and high permeability. The two ends of the copper tube 2012 are connected to a plastic hose 2014. One end is connected to another electromagnet with the same structure, and the other end is connected to a water cooling device 203. The two electromagnets 201 and the water cooling device 203 form a closed liquid circuit. The container of the water-cooling device 203 contains cooling water and ice packs. A constant voltage DC power supply continuously powers the water pump in the water-cooling device, allowing the cooling water to circulate in a closed liquid circuit, carrying away the heat generated by the electromagnet 201. The copper tube and thermal grease have excellent thermal conductivity, ensuring that the electromagnet energized coil 2011 and the cooling water can have sufficient heat exchange, solving the problem of the electromagnet overheating during long-term operation, and enabling the invented device to generate a stable periodic magnetic field over a long period of time.

[0039] like Figure 5 As shown, the lifting bracket 202 consists of an electromagnet mounting bracket 2021, an electrode plate mounting bracket 2022, a lifting bar, and a base. The small knob on the electromagnet mounting bracket 2021 is used to fix the electromagnet, while the large knob is used to adjust the electromagnet's vertical position. Similarly, the electrode plate mounting bracket 2022 can also be adjusted vertically using knobs. The lifting bracket 202 allows for precise adjustment of the relative distance between the electromagnet and the microfluidic electrode plate, facilitating the determination of the optimal experimental distance. It also allows for easy installation and removal of the electromagnet, simplifying subsequent device maintenance.

[0040] like Figure 2 , Figure 4 As shown, the two ends of the energized coil 2011 of the electromagnet 201 are connected to the electromagnet control module 204. The electromagnet control module 204 consists of a relay, a variable DC power supply, and a microcontroller. The variable DC power supply can be set to adjust the magnetic field strength generated by the electromagnet by setting the power supply voltage, making it easy to adjust the magnetic field strength to a suitable level for the experiment. The microcontroller controls the relay connected to the variable DC power supply to control the electromagnet 201 to periodically switch on and off, generating a periodically changing magnetic field. The period required for the experiment can be set by the microcontroller.

[0041] like Figure 2 As shown, when the magnetic field modulated magnetic bead electrochemical detection device is working, the periodic electrochemical signals generated by the electrode sheet are transmitted to the electrochemical workstation 205 for subsequent data processing.

[0042] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnetic bead microchannel electrochemical detection device based on magnetic field modulation, characterized in that, Includes a support frame, electromagnet, microfluidic electrode sheet, and control module; The electromagnet and microfluidic electrode sheet are fixed on the support; The microfluidic electrode sheet is provided with a U-shaped microfluidic channel with openings at both ends. An oxidation working electrode and a reduction working electrode are provided on the inner wall of the U-shaped microfluidic channel, which are positioned opposite each other. The distance between the oxidation working electrode and the reduction working electrode is 10-1000μm. The electromagnet is controlled by the control module. The electromagnet includes a first electromagnet and a second electromagnet, which are located on both sides of the microchannel electrode sheet. The first electromagnet is closer to the oxidation working electrode, and the second electromagnet is closer to the reduction working electrode. During operation, the electromagnet generates a periodically changing magnetic field under the control of the control module. The U-shaped microchannel of the microchannel electrode sheet is located within the periodically changing magnetic field. During operation, the test solution containing modified magnetic beads is placed in a U-shaped microchannel. An oxidation potential is applied to the oxidation working electrode, and a reduction potential is applied to the reduction working electrode. Under the control of the control module, an electromagnet generates a periodically changing magnetic field in the U-shaped microchannel. Under the action of the periodic magnetic field, the modified magnetic beads move back and forth between the oxidation and reduction working electrodes in the U-shaped microchannel. When the modified magnetic beads move to the oxidation working electrode, an oxidation reaction occurs on the oxidation working electrode, and an oxidation current is output. When they move to the reduction working electrode, a reduction reaction occurs on the reduction working electrode, and a reduction current is output.

2. The magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to claim 1, characterized in that, The support is a lifting support, and the two electromagnets and the microfluidic electrode sheet are detachably fixed on the lifting support.

3. The magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to claim 1, characterized in that, It is also equipped with a cooling device for cooling the electromagnet.

4. The magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to claim 3, characterized in that, The cooling device includes a hollow spiral tube encased in an electromagnet, a connecting pipe, a coolant storage tank, and a circulation pump; the hollow spiral tube, the connecting pipe, and the coolant storage tank form a closed loop for coolant circulation, and the circulation pump is used to drive the coolant to circulate within the closed loop.

5. The magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to claim 4, characterized in that, The hollow spiral tube is made of copper; the gap between the hollow spiral tube and the electromagnet is filled with thermally conductive silicone grease.

6. The magnetic bead microchannel electrochemical detection device based on magnetic field modulation according to claim 1, characterized in that, The control module includes a relay, a variable DC power supply, and a microcontroller.

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