Methods to improve the performance of aptamer-based field-effect transistor biosensors

Abstract

The present invention provides a method for improving the performance of an aptamer field effect transistor biosensor, comprising: obtaining a transfer characteristic curve of an aptamer-based field effect transistor biosensor and obtaining its subthreshold interval; obtaining the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment; combining the subthreshold interval and the charge polarity of the aptamer to obtain a first voltage interval opposite to the charge polarity of the aptamer, and the first voltage interval is within the subthreshold interval range; biasing the liquid gate voltage of the field effect transistor biosensor within the first voltage interval to detect the object to be detected in the solution. Through the method of the present invention, a suitable voltage range can be obtained. When the liquid gate bias of the sensor is within the voltage range, the aptamer modified on the field effect transistor biosensor will be perpendicular to the channel surface, so that the volume of the aptamer is increased, thereby improving the binding efficiency of the aptamer and the object to be detected, and finally making the sensor have a lower detection limit and a higher detection sensitivity, thereby improving the detection performance of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensors, in particular to aptamer-based biosensors, and in particular to a method for improving the performance of aptamer-based field effect transistor biosensors. Background Art

[0002] A biosensor is a detection device that is sensitive to biological molecules and can convert their concentration information into electrical signals. As an extension of human senses, it is used in medicine, aerospace science and daily life. It can be used to quantitatively or qualitatively detect some disease-related biomarker molecules that people are concerned about, such as proteins, antibodies, antigens, enzymes, viruses, DNA and RNA, etc. The output is an electrical signal. The characterization and analysis of the electrical signals can help people understand and evaluate their own physical condition.

[0003] Existing biosensors mainly include electrochemical biosensors, optical biosensors, and field effect transistor biosensors. Electrochemical biosensors use electrodes as conversion elements and fixed carriers, fix biological sensitive substances such as antigens, antibodies, enzymes, hormones, viruses, etc., or the organisms themselves as sensitive elements on the electrodes, and convert the signals of the target molecules and their reactions into electrical signals such as capacitance, current, potential, conductivity, etc. through the specific recognition between biological molecules, so as to achieve qualitative or quantitative detection of the target analyte. Combining the specificity of biological reactions with electrochemical analysis methods, a powerful means is provided for the detection of biological samples. However, the response characteristics of electrochemical biosensors are linear, and they do not have the function of current amplification, resulting in a high detection limit of the sensor, a small detection dynamic range and detection response of the sensor, and low sensitivity. It cannot be used to detect extremely low content biomarkers in the human body, which limits the application scenarios of electrochemical biosensors. In addition, in order to obtain greater sensitivity, the electrodes of electrochemical biosensors are usually relatively large, which does not conform to the development trend of miniaturization and integration. Optical biosensors not only fail to meet the needs of future sensor miniaturization and integration, but also have unsatisfactory detection limits and sensitivities, high production costs, complex detection equipment, and require professional personnel to operate and use, which also limits their development.

[0004] Compared with traditional electrochemical biosensors and optical biosensors, field effect transistor biosensors are suitable for detection environments with extremely low concentrations and have higher detection sensitivity because the voltage amplification effect of field effect transistors allows the sensor to exponentially amplify the output current for weak voltage signal changes. Since the sensor has a lower detection limit, the dynamic detection range of the sensor will also be larger. Although field effect transistor biosensors have the advantages of high sensitivity and low detection limit compared to traditional biosensors, their detection performance still needs to be improved when used to detect target molecules with lower content such as DNA, RNA and viruses, especially when the concentration of target molecules reaches the aM level, ordinary field effect transistor biosensors cannot detect it. The main reason is that the recognition molecules modified on the sensor surface are not in an ideal state. For example, they are all perpendicular to the sensor channel surface. It is more likely that the connecting molecules or recognition molecules are fixed on the channel surface at an angle, or even lying on the channel surface. As a result, the effective volume of the sensor recognition molecules is smaller than the theoretical value, which greatly reduces the efficiency of the sensor in capturing the object to be tested. In addition, since some recognition molecules lie on the channel surface, other charged molecules in the solution to be tested can also be closer to the channel surface, causing interference to the sensor channel current. Ultimately, the detection limit and detection sensitivity of the field effect transistor biosensor are not ideal. Summary of the invention

[0005] The present invention aims to provide a method for improving the performance of an aptamer-based field effect transistor biosensor, by biasing the liquid gate voltage (Vgs) of the sensor within a preset voltage range to improve the detection response of the aptamer-based field effect transistor biosensor.

[0006] According to a first aspect of the present invention, a method for improving the performance of an aptamer-based field effect transistor biosensor is provided, comprising:

[0007] Obtaining a transfer characteristic curve of an aptamer-based field effect transistor biosensor and obtaining its subthreshold interval;

[0008] Obtain the charge polarity of the aptamer modified by the field effect transistor biosensor in the solution environment;

[0009] In combination with the subthreshold interval and the charge polarity of the aptamer in the solution environment, a first voltage interval is obtained within the subthreshold interval, and the first voltage interval is a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment; and the liquid gate voltage (Vgs) of the field effect transistor biosensor is biased within the first voltage interval to detect the object to be detected in the solution.

[0010] In one embodiment, the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment is determined according to the isoelectric point of the aptamer modified by the field effect transistor biosensor.

[0011] In one embodiment, the first voltage interval has a narrower voltage range than the subthreshold interval and has a single polarity.

[0012] According to a second aspect of the present invention, a method for detecting an analyte in a target solution using an aptamer-based field effect transistor biosensor is provided. During the detection process, the liquid gate voltage (Vgs) of the aptamer-based field effect transistor biosensor is biased within a preset voltage range to obtain a detection output;

[0013] The preset voltage interval is a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment, wherein the preset voltage interval is a voltage interval narrower than the subthreshold region of the aptamer-based field effect transistor biosensor and has a single polarity.

[0014] In one embodiment, the preset voltage interval is configured to be predetermined, and the predetermined manner is as follows:

[0015] Obtaining a transfer characteristic curve of an aptamer-based field effect transistor biosensor and obtaining its subthreshold interval;

[0016] Determining the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment according to the isoelectric point of the aptamer modified by the field effect transistor biosensor;

[0017] The first voltage interval is obtained by combining the subthreshold interval and the charge polarity of the aptamer in the solution environment, and the first voltage interval is used as the preset voltage interval, wherein the first voltage interval is a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment.

[0018] In one embodiment, the aptamer-based field effect transistor biosensor is a field effect transistor biosensor for detecting one of glucose, protein, antibody, antigen, enzyme, virus, DNA and RNA.

[0019] The method for improving the performance of aptamer-based field effect transistor biosensors proposed by the present invention generates an electric field by applying a liquid gate voltage with a polarity opposite to the charge polarity of the aptamer, thereby adjusting the shape of the aptamer on the surface of the field effect transistor channel, so that the aptamer on the field effect transistor sensor is more perpendicular to the channel surface, increasing the effective volume of the aptamer, and improving the efficiency and ability of the sensor to capture the analyte, so that the sensor can capture more analytes in the same concentration of analytes, and ultimately improve the detection response of the sensor.

[0020] It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below can be considered as part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent. In addition, all combinations of the claimed subject matter are considered as part of the inventive subject matter of the present disclosure.

[0021] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0023] Figure 1 is a schematic diagram of a method for improving the performance of an aptamer-based field effect transistor biosensor according to an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of a subthreshold interval according to an embodiment of the present invention;

[0025] Figure 3a-3b It is a schematic diagram of the shape of the aptamer modified on the surface of the field effect transistor biosensor and its capture of the object to be detected when the liquid gate voltage is biased within the first voltage interval according to an embodiment of the present invention.

[0026] Figure 4a-4b It is a schematic diagram of the shape of the aptamer modified on the surface of the field effect transistor biosensor and its capture of the object to be detected when the liquid gate voltage is biased in the subthreshold interval but not in the first voltage interval according to an embodiment of the present invention.

[0027] Figure 5The figure is a schematic structural diagram of a carbon nanotube-based field effect transistor biosensor prepared according to an embodiment of the present invention, in which a glucose aptamer is modified on the channel surface via a gold-sulfur bond.

[0028] Figure 6 The present invention is a flow chart of a process for preparing a carbon nanotube-based field effect transistor biosensor according to an embodiment of the present invention.

[0029] Figure 7 Schematic diagram of the structure of a glucose aptamer according to an embodiment of the present invention.

[0030] Figure 8 The graph is a response-concentration curve obtained by testing the carbon nanotube-based field effect transistor biosensor prepared according to an embodiment of the present invention under different liquid gate voltages. DETAILED DESCRIPTION

[0031] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0032] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily defined to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed by the present invention are not limited to any implementation. In addition, some aspects disclosed by the present invention can be used alone, or in any appropriate combination with other aspects disclosed by the present invention.

[0033] Combination Figure 1 The method for improving the performance of the aptamer-based field effect transistor biosensor of the illustrated embodiment comprises the following process:

[0034] S101: obtaining a scanning transfer characteristic curve of the aptamer-based field effect transistor biosensor and obtaining its subthreshold interval;

[0035] S102: Obtaining the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment;

[0036] S103: Determine a preset first voltage interval in combination with the subthreshold interval and the charge polarity of the aptamer in the solution environment; the first voltage interval is a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment; and

[0037] S104: biasing the liquid gate voltage (Vgs) of the field effect transistor biosensor within the aforementioned first voltage range to detect the object to be detected in the solution.

[0038] Wherein, the charge polarity of the aptamer modified by the field effect transistor biosensor in the solution environment is determined according to the isoelectric point of the aptamer modified by the field effect transistor biosensor.

[0039] For example Figure 2 The figure shows a transfer characteristic curve of a field effect transistor biosensor based on an aptamer, in which the interval marked in gray is the subthreshold interval, and its voltage range is between [-0.1, 0.1]. It should be understood that within this subthreshold interval, the source-drain current I ds It increases exponentially with the increase of gate voltage Vgs. Therefore, if the liquid gate bias of the sensor is set within this range, the sensor can obtain a lower detection limit and a greater detection sensitivity.

[0040] Combination Figure 2 As shown, according to an embodiment of the present invention, for example, taking the aptamer with a negative charge in the test solution environment as an example, the first voltage interval is determined to be [0,0.1], that is, the voltage interval [-0.1,0] is discarded, and a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment is selected, that is, Figure 2 The interval represented by 1.

[0041] Of course, if the aptamer carries a positive charge in the test solution environment, the first voltage interval is also determined based on the principle that the polarity is opposite to the charge polarity carried by the aptamer in the solution environment.

[0042] Therefore, in the embodiment of the present invention, the first voltage interval has a narrower voltage range than the subthreshold interval and has a single polarity.

[0043] Combination Figure 3a-3b As shown in FIG. 1 , when the liquid gate voltage Vgs is biased in the first voltage interval, the schematic diagram of the shape of the aptamer modified on the surface of the field effect transistor biosensor and the schematic diagram of its capturing the molecule to be detected are respectively shown. Figure 3a As shown, when the liquid gate voltage is biased in the first voltage interval, the shape of the aptamer modified on the surface of the field effect transistor biosensor channel is compared with when the liquid gate voltage is biased in a non-first voltage interval (combined with Figure 4a ), will tend to be more perpendicular to the channel surface, the volume of the aptamer increases significantly, therefore, the binding Figure 3b In the example shown, the aptamer is able to capture more analyte molecules (compared to Figure 4b The capture results shown).

[0044] In the present invention Figure 3a-3b as well as Figure 4a-4b In the experiment, the test solution with the same solubility was used.

[0045] Combination Figure 3a-3bas well as Figure 4a-4b As shown, when the volume of the aptamer on the surface of the aptamer-based field effect transistor biosensor increases, the probability of the aptamer specifically binding to the analyte increases. Therefore, under the same analyte concentration conditions, the aptamer on the sensor surface will be able to capture more analytes, thereby effectively improving the detection sensitivity of the aptamer-based field effect transistor biosensor.

[0046] like Figure 5 FIG. 1 shows the structural design of a carbon nanotube field effect transistor biosensor according to an embodiment of the present invention, which uses a network of carbon nanotubes (CNTs) as a channel layer, and a glucose aptamer is modified on the channel surface by a gold-sulfur bond, as shown in FIG. Figure 7 Shown is a schematic diagram of the structure of the glucose aptamer, whose aptamer sequence is HS-C6-ACG ACC GTGTGT GTT GCT CTG TAA CAG TGT CCA TTG TCG T.

[0047] Figure 6 The process of preparing a carbon nanotube-based field effect transistor biosensor by micro-nano processing is shown in an exemplary manner, wherein silicon / silicon dioxide (Si / SiO 2 ) as the substrate; CNT film is a network-like carbon nanotube film; the source and drain (Contact layer) are both Ti / Pd / Au; the insulating layer (Dielectric) is yttrium oxide, which is used to obtain a floating gate field effect transistor biosensor with better performance. Linker is gold nanoparticles prepared by electron beam coating instrument; the passivation layer (Passivation layer) is S1813 glue, which is used to passivate the device.

[0048] Combination Figure 5 , 6 In the example shown, the size of the prepared carbon nanotube-based field effect transistor biosensor can be determined according to the design requirements. In the example shown in the figure, the network carbon nanotube film uses a single-layer network carbon tube with a thickness of less than 2nm. The thickness of the insulating layer yttrium oxide is about 5-6nm. The source and drain are Ti / Pd / Au with a thickness of 0.3 / 30 / 40nm. The particle size of the gold nanoparticles is approximately equal to 0.6nm. The thickness of the passivation layer is about 1 micron.

[0049] In an embodiment of the present invention, according to Figure 1The method for improving the performance of the aptamer-based field effect transistor biosensor shown in the example first determines the subthreshold interval of the field effect transistor biosensor between [-0.1, 0.1]. Then, combined with the isoelectric point of the aptamer, the charge polarity of the aptamer modified by the field effect transistor biosensor in the solution environment is determined to be negative, and the first voltage interval is determined to be between [0, 0.1].

[0050] During the testing process, Figure 5 The liquid gate voltage Vgs of the aptamer-based field effect transistor biosensor shown is biased in a first voltage interval, between [0, 0.1], to obtain a detection output.

[0051] In combination with the above-mentioned embodiment, the preset voltage interval is a voltage interval with a polarity opposite to the polarity of the charge carried by the aptamer in the solution environment. In addition, the preset voltage interval has a voltage range narrower than the subthreshold region of the aptamer-based field effect transistor biosensor and has a single polarity.

[0052] Combination Figure 8 The test comparison results shown in the figure show that the glucose aptamer used is negatively charged in the test solution environment, and the subthreshold range is -0.1 to 0.1V; therefore, the voltage range of the first voltage interval is determined to be 0 to 0.1V.

[0053] Combination Figure 8 As shown, the sensor liquid gate voltage Vgs is biased in the subthreshold interval but not in interval 1. Taking Vgs = -0.05V as an example, the sensor's detection response to glucose molecules of various concentrations is as follows Figure 8 As shown in the circle.

[0054] Combination Figure 8 As shown in FIG. 1 , the sensor liquid gate voltage Vgs is biased within interval 1. Taking Vgs = 0.05V as an example, the sensor's detection response to glucose molecules of various concentrations is as follows: Figure 8 The pentagon in Figure 2 is shown.

[0055] Combination Figure 8 The sensor biased under different liquid gate voltages shows a response-concentration curve for glucose detection. The detection sensitivity obtained when the sensor liquid gate voltage Vgs is biased within interval 1 is much higher than the sensitivity when it is biased outside interval 1. This is because the sensor is biased under a suitable liquid gate voltage through the method of the present invention, so that the aptamer tends to be more perpendicular to the channel surface. Compared with the inclined or fallen aptamer, the method of the present invention can enable the sensor to obtain a larger aptamer volume, thereby improving the efficiency of the sensor in capturing the object to be detected, and ultimately improving the detection response of the sensor. It can be seen that by applying the method of the present invention to the detection of the sensor, the response characteristics of the sensor can be significantly improved.

[0056] In addition, the carbon nanotube field effect transistor glucose biosensor based on aptamers has a wider dynamic range than the electrochemical glucose sensor, and can detect any glucose concentration in the range of 1nM to 10mM, which is suitable for the detection of glucose concentration in environments such as sweat, saliva, tears and blood. And due to the improvement of sensor performance by the present invention, the sensor's detection limit for glucose can be as low as 1fM.

[0057] In the above examples, the carbon nanotube field effect transistor glucose biosensor is used as an example to illustrate the implementation of the present invention. It should be understood that the method for improving the performance of aptamer-based field effect transistor biosensors in the above embodiments of the present invention is applicable to all aptamer-based field effect transistor biosensors, not limited to carbon nanotube field effect transistor biosensors.

[0058] The aptamer-based field effect transistor biosensor is a field effect transistor-based channel surface modified with an aptamer to detect the object to be detected in the solution. The channel layer can be made of materials such as silicon, graphene and molybdenum disulfide, but is not limited to carbon nanotubes. When the method of the present invention is applied to improve the detection sensitivity of the aptamer-based field effect transistor biosensor, the liquid gate voltage Vgs of the aptamer-based field effect transistor biosensor can be biased within a preset voltage range and then used to detect the object to be detected in the solution, thereby improving the sensor's capture efficiency of the object to be detected, and ultimately improving the sensor's detection response and increasing the sensor's dynamic detection range.

[0059] Through the implementation of the present invention, compared with the detection process of traditional electrochemical sensors and ordinary field effect transistor biosensors, nM-level detection can be achieved, effective detection can be achieved in the range of 1nM to 10mM, and the detection sensitivity of the sensor can be improved at the same time.

[0060] In an optional embodiment, as described above, for any aptamer-based field effect transistor biosensor, the liquid gate voltage applied during detection can be pre-configured and determined, for example, the first voltage interval is determined as the preset voltage interval according to the method described above.

[0061] In an embodiment of the present invention, the aptamer-based field effect transistor biosensor can be configured to detect cells, microorganisms, and other detection objects, such as glucose, proteins, antibodies, antigens, enzymes, viruses, DNA, or RNA.

[0062] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for improving the performance of an aptamer field effect transistor biosensor, characterized in that: include: Obtaining a transfer characteristic curve of an aptamer field effect transistor-based biosensor and obtaining its subthreshold interval; Obtain the charge polarity of the aptamer modified by the field effect transistor biosensor in the solution environment; Combining the subthreshold interval and the polarity of the charge carried by the aptamer in the solution environment, a first voltage interval is obtained, and the first voltage interval is within the subthreshold interval range, and the first voltage interval is a voltage interval with a polarity opposite to the polarity of the charge carried by the aptamer in the solution environment; as well as The liquid gate voltage of the field effect transistor biosensor is biased within the first voltage range to detect the object to be detected in the solution.

2. The method for improving the performance of aptamer field effect transistor biosensor according to claim 1, characterized in that: The method of obtaining the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment comprises: According to the isoelectric point of the aptamer modified by the field effect transistor biosensor, the charge polarity of the aptamer modified by the field effect transistor biosensor in the solution environment is determined.

3. The method for improving the performance of aptamer field effect transistor biosensor according to claim 1, characterized in that: The aptamer-based field effect transistor biosensor is a carbon nanotube-based field effect transistor biosensor, and its channel layer is a carbon nanotube channel layer.

4. The method for improving the performance of aptamer field effect transistor biosensor according to any one of claims 1 to 3, characterized in that: When the liquid gate voltage of the aptamer-based field effect transistor biosensor is biased in the first voltage interval, the shape of the aptamer modified on the surface of the channel layer of the field effect transistor biosensor is perpendicular to the channel surface.

5. A method for detecting an object to be detected in a test solution using an aptamer-based field effect transistor biosensor, characterized in that: During the detection process, the liquid gate voltage of the aptamer-based field effect transistor biosensor is biased within a preset first voltage interval to obtain a detection output; The preset first voltage interval is a voltage interval with a polarity opposite to the polarity of the charge carried by the aptamer in the solution environment, wherein the preset first voltage interval is a single polarity and is within the subthreshold interval.

6. The method for detecting an object to be detected in a test solution using an aptamer-based field effect transistor biosensor according to claim 5, characterized in that: The preset first voltage interval is configured to be predetermined, and the predetermined manner is as follows: Obtaining a scanning transfer characteristic curve of an aptamer-based field effect transistor biosensor and obtaining its subthreshold interval; Determining the charge polarity of the aptamer modified by the field effect transistor biosensor in a solution environment according to the isoelectric point of the aptamer modified by the field effect transistor biosensor; Combining the subthreshold interval and the charge polarity of the aptamer in the solution environment, a first voltage interval is obtained, and the first voltage interval is within the subthreshold interval range. The first voltage interval is used as the preset voltage interval, wherein the first voltage interval is a voltage interval with a polarity opposite to the charge polarity of the aptamer in the solution environment.

7. The method for detecting an object to be detected in a test solution using an aptamer-based field effect transistor biosensor according to claim 5, characterized in that: The aptamer-based field effect transistor biosensor is a carbon nanotube-based field effect transistor biosensor, and its channel layer is a carbon nanotube channel layer.

8. The method for detecting an object to be detected in a test solution using an aptamer-based field effect transistor biosensor according to claim 5, characterized in that: The aptamer-based field effect transistor biosensor is a field effect transistor biosensor for detecting one of glucose, protein, antibody, antigen, biological enzyme, virus, DNA and RNA.

9. The method for detecting an object to be detected in a test solution using an aptamer-based field effect transistor biosensor according to claim 5, characterized in that: During the detection process, when the liquid gate voltage of the aptamer-based field effect transistor biosensor is applied within the first voltage interval, the shape of the aptamer modified on the channel surface of the field effect transistor biosensor will be perpendicular to the channel surface.

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