JP7650502B2 - Transistor Type Sensor - Google Patents

Description

The present invention relates to an organic semiconductor transistor-type sensor that utilizes an antigen-antibody reaction, and a measurement method for quantitatively measuring antigens or antibodies using a transistor-type sensor.

Oxytocin is a hormone secreted in the brain and can be used as a biomarker to objectively evaluate the mother's mental state in maternal-child nursing.
Enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC) are used to analyze oxytocin, but they require advanced expertise, sample pretreatment, and large equipment. Furthermore, the long measurement time is also a factor that hinders rapid testing, so there is a need to realize a small sensor that can achieve high sensitivity detection easily and quickly. In addition, quantitative detection is required to evaluate the change in the amount of oxytocin.

As a small sensor, sensors using transistors such as those described in Non-Patent Document 1 have been considered, but a method for measuring oxytocin using such a small sensor has not yet been realized.

Minami, T. ACS Sense. 2019, 4, 2571-2587.

The inventors have investigated a detection method using a transistor as a method for detecting oxytocin, and have discovered that a transistor using an organic semiconductor with a detection electrode connected to a gate electrode and an oxytocin antibody chemically bound to the surface of the detection electrode via a linker and a binding portion can detect the antigen oxytocin, thus arriving at the present invention.

That is, the present invention includes the following.
[1] A transistor-type sensor comprising a detection electrode for detecting an antigen or an antibody by capturing the antigen or the antibody, and an organic semiconductor transistor having a gate electrode connected to the detection electrode, wherein when the detection electrode detects an antigen, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part, and when the detection electrode detects an antibody, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part.
[2] The transistor-type sensor according to [1], wherein the binding portion is composed of streptavidin and biotin, or composed of avidin and biotin.
[3] The transistor-type sensor according to [2], wherein the antigen or the antibody is chemically bound to the streptavidin or the avidin.
[4] The transistor-type sensor according to any one of [1] to [3], wherein the linker has a molecular length of 0.3 to 2.6 nm.
[5] The transistor-type sensor according to any one of [1] to [4], wherein the antigen is oxytocin and the antibody is an oxytocin antibody.
[6] The transistor-type sensor according to [1], wherein the organic semiconductor transistor is a p-type semiconductor.
[7] The transistor-type sensor according to [1], which detects the detection target in a solution or dispersion.
[8] A method for quantitatively measuring an antigen or an antibody by using a transistor-type sensor, comprising:
A step of contacting an antigen or antibody to be detected with the detection electrode of the transistor-type sensor according to [1];
measuring a current Id flowing between the drain electrode and the source electrode of the transistor for each concentration of the detection target, and obtaining a concentration-current Id relationship curve;
a step of contacting the detection electrode with the detection target having an unknown concentration and obtaining a current Id of the detection target having an unknown concentration;
comparing the current Id of the detection target, the concentration of which is unknown, with the concentration-current Id relationship curve to determine the concentration of the current Id of the detection target, the concentration of which is unknown.
[9] A method for quantitatively measuring an antigen or an antibody by using a transistor-type sensor, comprising:
A step of contacting an antigen or antibody to be detected with the detection electrode of the transistor-type sensor according to [1];
measuring a threshold voltage for each concentration of the detection target and obtaining a concentration-threshold voltage relationship curve;
a step of contacting the detection electrode with the target substance having an unknown concentration, and obtaining a threshold voltage of the target substance having an unknown concentration;
comparing a threshold voltage of the detection target having an unknown concentration with the concentration-threshold voltage relationship curve, and determining the concentration of the threshold voltage of the detection target having an unknown concentration.
[10] The measurement of the threshold voltage
applying a voltage Vd to a drain electrode of the organic semiconductor transistor with respect to a source electrode, and applying a voltage Vg to a counter electrode with respect to the source electrode;
obtaining a Vg-Id curve by sweeping the Vg and measuring a current Id flowing between the drain electrode and the source electrode;
and obtaining a threshold voltage value using the Vg-Id curve.
[11] The measurement method according to [9], wherein the transistor-type sensor further includes a counter electrode, and the detection electrode and the counter electrode are brought into contact with the detection target.
[12] The measurement method according to [9], wherein the detection target is contained in a solution or dispersion, and detection is performed in a state in which the detection electrode and the counter electrode are immersed in the solution or dispersion.
[13] The measurement method according to [9], wherein the applied voltage is a DC voltage.

The transistor-type sensor of the present invention has a simple structure and is capable of quantitatively measuring the antigen or antibody to be detected by utilizing the antigen-antibody reaction.

FIG. 1 is a schematic diagram of a transistor-type sensor according to a first embodiment. FIG. 2 shows a manufacturing procedure for the transistor type sensor of the first embodiment. FIG. 3 is a schematic diagram showing the process of immobilizing an antibody on the electrode surface. FIG. 4 is a schematic diagram showing the immobilization of an antibody. FIG. 5 is a schematic diagram showing the state when an antigen is immobilized. FIG. 6 is a diagram showing a shift in threshold voltage from the start of detection in the first embodiment. FIG. 7 is a diagram showing the measurement results of Example 1. FIG. 8 is a diagram showing the measurement results of Example 1. FIG. 9 is a diagram showing the change in threshold voltage with respect to concentration in Example 1. FIG. 10 is a diagram showing the measurement results of Comparative Example 1. FIG. 11 is a diagram showing the measurement results of Comparative Example 1. FIG. 12 is a diagram showing the change in threshold voltage with respect to the concentration in Comparative Example 1. In FIG. FIG. 1 is a diagram in which the current Id is plotted against the oxytocin concentration for the detection experiment of Example 1. FIG. 13 is a diagram in which the current Id is plotted for each oxytocin concentration in the detection experiment of Comparative Example 1.

[Transistor type sensor]
The transistor-type sensor of the present invention is a transistor-type sensor comprising a detection electrode for detecting an antigen or an antibody by capturing the antigen or the antibody, and an organic semiconductor transistor having a gate electrode connected to the detection electrode, wherein when the detection electrode detects an antigen, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part, and when the detection electrode detects an antibody, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part. The detection electrode is an extended gate electrode of a transistor.

(Transistor)
The sensor of the present invention includes a field effect transistor, which is a thin film transistor made of an organic semiconductor, because it is small and easy to use.
In the present invention, a field effect transistor using an organic semiconductor of a normal configuration can be used, and an example is shown in Fig. 1. The field effect transistor T in Fig. 1 is a typical field effect transistor, and is composed of a substrate 1, a gate electrode 2, a gate insulating film 3, a source electrode 4, a drain electrode 5, a bank 6, an organic semiconductor (OSC) 7, and a sealing film 8.
The material constituting the field effect transistor T is not particularly limited. For example, the substrate 1 may be made of inorganic materials such as glass, ceramics, and metals, as well as organic materials such as resin and paper. The gate electrode 2 may be made of aluminum, silver, gold, copper, titanium, indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, conductive carbon nanotubes, graphene, conductive organic-inorganic composite materials, and the like. The gate insulating film 3 may be made of materials such as silica (silicon oxide), alumina (aluminum oxide), self-assembled monolayers, polystyrene, polyvinylphenol, polyvinyl alcohol, polymethyl methacrylate, polydimethylsiloxane, polysilsesquioxane, ionic liquid, and polytetrafluoroethylene. The substrate 1 and the gate electrode 2 may be integrated together, and a metal substrate or a Si substrate may be used. The Si substrate is preferably doped to improve conductivity. When the organic semiconductor layer is p-type, a substrate doped to n-type may be used, and when the organic semiconductor layer is n-type, a substrate doped to p-type may be used. Furthermore, the gate insulating film 3 may be made of SiO ₂ formed by oxidizing the surface of a Si substrate. Examples of materials for the source electrode 4 and the drain electrode 5 include metals such as gold, silver, copper, platinum, and aluminum, conductive polymers such as PEDOT:PSS, conductive carbon nanotubes, graphene, and conductive organic-inorganic composite materials. Examples of materials for the bank 6 include polytetrafluoroethylene, and examples of materials for the sealing film 8 include polytetrafluoroethylene and polyparaxylylene.
The substrate 1, gate electrode 2, gate insulating film 3, source electrode 4, and drain electrode 5 may be subjected to a surface treatment, for example, a self-assembled monolayer may be formed in order to adjust the liquid repellency of the surface.

The material of the organic semiconductor 7 is not particularly limited as long as it can exhibit its function, but in the case of a P-type, pentacene, dinaphthothienothiophene, benzothienobenzothiophene (Cn-BTBT), TIPS pentacene, TES-ADT, rubrene, P3HT, PBTTT, etc. can be used, and in the case of an N-type, fullerene, etc. can be used. Among them, the following compounds are preferably used, and were also used as the semiconductor materials in the examples described in this specification.

In FIG. 1, the detection electrode EL includes a conductor 9, a detection electrode substrate 10, a detection electrode body 11, a counter electrode 12, an aqueous solution 13 containing the detection target, and an active layer 14. The detection electrode body 11 is electrically connected to the gate electrode 2 of the transistor T by a conductor 9. In experiments, it is preferable to place the detection electrode EL and the counter electrode in a tube containing the aqueous solution to make it easier to detect the liquid.

Examples of materials for the detection electrode substrate 10 include polyethylene naphthalate. The detection electrode main body (extended gate electrode main body) 11 is disposed on the surface of the detection electrode substrate 10. However, if the detection electrode main body 11 is self-supporting, it may also serve as the detection electrode substrate 10. As with the gate electrode 2, the material for the detection electrode main body 11 may be aluminum, silver, gold, copper, titanium, indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, conductive carbon nanotubes, graphene, conductive organic-inorganic composite materials, or the like.
The counter electrode 12 may be made of any material having electrical conductivity, and may be a metal electrode or a carbon electrode. The counter electrode 12 may be a conductive film formed on a substrate made of the same material as the detection electrode substrate 10, or a conductive film may be formed on a detection electrode substrate shared with the detection electrode. An active layer made of the same or different material as the active layer 14 may be formed on the counter electrode 12. The active layer on the counter electrode 12 may be treated in the same manner as the active layer 14, or may be treated up to an intermediate stage of the active layer 14. A reference electrode may also be used, and examples of commonly used materials include Ag/AgCl.
An active layer 14 is formed on the detection electrode body 11. The transistor-type sensor of the present invention detects a detection target by utilizing an antigen-antibody reaction, so when the detection target is an antigen, the active layer 14 contains an antibody capable of undergoing an antigen-antibody reaction with the antigen of the detection target, and when the detection target is an antibody, the active layer 14 contains an antigen capable of undergoing an antigen-antibody reaction with the antibody of the detection target.
In the following, as an example, the detection target is an antigen, and what is immobilized on the detection electrode body is an antibody, but the present invention is not limited to this example.

The antibodies immobilized on the surface of the detection electrode body 11 are not directly deposited on the surface, but are bound via a linker and a binding moiety.
The detection electrode body 11 is preferably formed of a metal thin film such as gold having a thickness of 10 nm to 1000 μm, or a carbon nanotube, graphene, conductive inorganic material thin film, or conductive organic material thin film, and the surface may be formed of a metal oxide film such as SiO ₂ having a thickness of 1 nm to 1000 nm, preferably 1 nm to 50 nm. In this specification, the surface of the detection electrode body 11 is a concept that includes both a case where the material of the detection electrode body 11 itself is the surface, and a surface on which a metal thin film or metal oxide film is formed.

The linker is composed of a linear compound having two or more carbon atoms. In the present invention, the linear compound may or may not have a branched chain. By using a linker, the antibody to be immobilized can be stably immobilized on the detection electrode while maintaining flexibility. In addition, the linker plays a role in keeping the distance between the detection target and the electrode constant, and the charge in the solution and the distance between the electrodes can be adjusted depending on the length of the linker, which affects the electric field acting on the gate electrode during electrochemical measurement. Specifically, the shorter the linker, the closer the charge is to the electrode, and when the charge simply approaches the electrode, the greater the effect on the gate electric field. However, if the linker is too short, the linker itself becomes difficult to align on the electrode, and the binding portion and the antibody are also arranged randomly, so that the direction of intramolecular polarization when the antigen acts is not aligned, and the effect on the gate electric field is small.

The linker has a site that reacts with the metal thin film or metal oxide film and a site that bonds with the binding site. It is preferable that each site is not on the same carbon but on separate carbons. In addition, the linker is preferably linear and has the above sites at both ends.
Examples of the site that reacts with the metal thin film or metal oxide film include a mercapto group, a carboxy group, an amino group, a triethylsilyl group, a trimethylsilyl group, a trichlorosilyl group, a sulfo group, a phosphonic acid group, etc. Examples of the site that bonds with the bonding part (reactive functional group) include a halogen group, a hydroxy group, an alkoxy group, a carbonyl group, a carboxy group, an amino group, etc.
For example, when an electrode having a gold surface is used, a mercapto group is selected as the site that reacts with the metal, and when a carboxy group is selected as the reactive functional group, a linker is selected from 3-mercaptopropionic acid, 6-mercaptohexanoic acid, 11-mercaptoundecanoic acid, etc.

The binding site is the site that binds the linker to the antibody. From the viewpoint of being able to stably bind to the linker without suppressing the immune reaction between the antigen-binding site of the antibody and the antigen, the binding site is preferably composed of a combination of streptavidin and biotin, or a combination of avidin and biotin.

The linker and antibody can be directly bonded, but avidin-biotin bonds are preferred. Antibodies are often large molecules compared to linkers, and because antibodies have multiple reactive sites, it is expected that multiple linkers and antibodies will be bonded when linkers and antibodies are bonded directly. When an antibody is bonded to multiple linkers, it becomes difficult for the antibody to be oriented uniformly on the electrode, and therefore the direction of intramolecular polarization when an antigen acts is not uniform, and the effect on the gate electric field is reduced.

By using streptavidin or avidin, if the streptavidin or avidin is formed in the same direction on the linker, the biotin that binds to it, and even the antibody to which the biotin is bound, can also be formed in the same direction. This allows the intramolecular polarization of the antigen to act on the electrode in a state where the direction is relatively uniform.

In order to bind the reactive functional group of the linker that binds to the binding portion to streptavidin or avidin, the immobilized linker may be reacted with a compound that enhances the reaction activity of the reactive functional group, and then bound to streptavidin or avidin. Examples of such compounds include sodium N-hydroxysulfosuccinimide, N-hydroxysuccinimide, 1-hydroxybenzotriazole, and 1-hydroxy-7-azabenzotriazole. When immobilizing the linker to the electrode, the lower the reaction activity of the reactive functional group that binds to the binding portion, the easier it is for the linker to be aligned and formed on the electrode, and it is preferable to increase the reaction activity of the linker after immobilizing it to the electrode and bind it to streptavidin or avidin.

The linker is not immobilized on the electrode without any gaps, and some of the electrode is exposed, and some substance may act on the electrode during antigen detection, adversely affecting the measurement results. To prevent this, it is preferable to physically adsorb a substance to the electrode surface in advance. Examples of such substances include human serum albumin, bovine serum albumin, casein, and polyethylene glycol.
The linker and streptavidin or avidin do not react 100% at the reactive sites, and the reactive functional groups of the linker remain, which may adversely affect the detection of the antigen. In order to prevent this, it is preferable to carry out an operation to convert the reactive functional groups of the linker into substituents with low reactive activity. A compound corresponding to a compound that increases the reactive activity of the reactive functional group is selected. For example, when sodium N-hydroxysulfosuccinimide is used, a water-soluble primary amine is preferable, and examples of such water-soluble primary amines include 2-aminoethanol, 1-amino-2-propanol, and 3-amino-1-propanol.

The antibody immobilized on the surface of the detection electrode body 11 via a linker or a binding site is capable of undergoing an antigen-antibody reaction with the antigen to be detected. The antibody immobilized on the detection electrode body 11 is not particularly limited as long as it is capable of undergoing an antigen-antibody reaction with the antigen to be detected, and examples of the antibody include chromogranin A, IgA, and IgG.
In particular, the combination of oxytocin and an oxytocin antibody allows accurate measurement of the concentration because the threshold voltage value clearly changes with the oxytocin concentration.
In addition to the threshold voltage, the current value can be used for measurement. The current value can be calculated by simply comparing Id measured at a specific voltage Vg. However, the amount of change in Id is often not linear with respect to the voltage Vg, and the measurement accuracy may vary depending on which voltage Vg Id is used for the calculation. In addition, when comparing current values in transistors having different threshold voltages, it is better to set the maximum current value, the median current value, the current value at a voltage (Vth+Vd), etc., rather than arbitrarily setting an absolute voltage.

[About the manufacturing method of transistor type sensor]
(Preparation of detection electrodes)
The preparation of the detection electrode includes a step of immobilizing an antibody on the surface of the detection electrode. In the example, a method of immobilizing an oxytocin antibody on the surface of the detection electrode will be described.
As already explained, the oxytocin antibody is not directly immobilized on the surface of the detection electrode, but is immobilized via a linker and a binding portion. Hereinafter, the method will be explained with reference to FIG.

(Formation of Linker)
First, linker A is formed on the detection electrode (FIG. 3(I)). Linker A is formed by dip-coating a compound that will become linker A using a method such as dip coating. For example, by immersing the electrode in an ethanol solution containing 3-mercaptopropionic acid, the sulfur atom of the 3-mercaptopropionic acid is bonded to the surface of the detection electrode.

(Formation of joint)
Next, a material that will become a binding portion is bound to the linker A on the detection electrode on which the linker A is formed. The binding portion is preferably a compound that can be chemically bound to the linker A, and in order to achieve this binding, a reactive functional group B is first formed on the end of the linker that is not bound to the detection electrode (FIG. 3 (II)). Specifically, a solution containing 2-(N-morpholino)ethanesulfonic acid, sodium N-hydroxysulfoscurcinimide, and N,N'-diisopropylcarbodiimide is dropped onto the detection electrode on which the linker A is formed, and the end of the linker A becomes a reactive functional group B.
Next, an aqueous solution of streptavidin is dropped onto the detection electrode, and streptavidin C is bound to the reactive functional group B (FIG. 3 (III)).

Next, the streptavidin C is treated with 2-aminoethanol to inactivate unbound reactive functional groups. Note that G in Fig. 4 shows a schematic diagram of unbound reactive functional groups being treated with 2-aminoethanol and inactivated.
Next, a solution containing human serum albumin is dropped onto the detection electrode, and then an oxytocin antibody (antibody E with biotin D attached) is added to the solution containing human serum albumin and dropped onto the detection electrode (IV in FIG. 3). This allows the immobilized antibody E to undergo an antigen-antibody reaction with antigen F.

Figure 4 shows the state in which the immobilized antibody E is undergoing an antigen-antibody reaction with the antigen F. Surface H of the detection electrode is treated to prevent physical adsorption of human serum albumin.

Figure 5 shows the state in which antigen F is immobilized on the detection electrode. In this case, the detection target is antibody E. In this case, the antigen F used is one to which biotin D has been attached.

(Fabrication of organic semiconductor transistors)
An example of a method for manufacturing the organic semiconductor transistor T shown in FIG. 1 will be described with reference to FIG. 3. First, a substrate 1 (made of glass) is prepared (a), and a gate electrode 2 (made of aluminum) with a thickness of 30 nm is formed on the surface of the substrate (b). Then, RIE (reactive ion etching to form an aluminum oxide film) is performed for 15 minutes, and a gate insulating film 3 is formed by processing with HFPA (c). Furthermore, source and drain electrodes 4 and 5 (both made of gold) are patterned (d). Then, a bank 6 (made of polytetrafluoroethylene) is formed (e), and a layer of an organic semiconductor 7 is formed (f). Finally, a sealing film 8 (made of polytetrafluoroethylene) is formed by spin coating or the like (g), and the organic semiconductor transistor T is manufactured.

A transistor-type sensor can be manufactured by connecting the gate electrode 2 to the detection electrode EL.

[Detection target substance]
Since the present invention uses an antigen-antibody reaction, when an antigen is immobilized on the detection electrode, the substance to be detected is an antibody, and when an antibody is immobilized on the detection electrode, the substance to be detected is an antigen. Therefore, in the above example, an oxytocin antibody is immobilized on the detection electrode. Therefore, the detection target of the sensor is oxytocin.

This sensor detects concentrations of the target substance that are preferably 0.1 to 1000 pg/mL, and more preferably 10 to 200 pg/mL. If the concentration exceeds 1000 pg/mL, the threshold voltage does not shift, making qualitative detection possible, but quantification difficult. If the concentration is less than 0.1 pg/mL, the detection limit is exceeded, making qualitative as well as quantitative detection difficult.

In this example, the temperature during detection is not particularly limited, but can be performed at room temperature. The pressure during detection is also not particularly limited, but can be performed in the atmosphere. However, since it is preferable that the detection target substance has the above-mentioned concentration, it is preferable to immerse the detection electrode in the solution containing the detection target and perform detection.

(Detection Method)
The method of measuring the detection target is to apply Vd at -1.0 V, and Vg at 0.1 V steps from +0.5 V to -3.0 V, and measure Id at that time. Then, an approximation line is drawn in the linear region (saturation region) where Id to the power of 1/2 and Vg are linear, and the value of the X-intercept is calculated to obtain the threshold voltage. The obtained threshold voltage changes depending on the concentration of the detection target.
By plotting a curve of concentration versus threshold voltage, the threshold voltage for a detection target of unknown concentration can be obtained, and the concentration can be measured.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Electrode preparation example 1
Electrode Preparation Example 1 will be described with reference to FIG.
Using a metal mask, a 100 nm gold thin film was formed on a PEN substrate by vacuum deposition to obtain an electrode 1. 3-mercaptopropionic acid was dissolved in ethanol to a concentration of 1 mM to prepare a treatment solution 1. Next, the electrode 1 was washed with ethanol and ultrapure water, dried, and then immersed in the treatment solution 1 at room temperature for 1 hour, followed by washing with ethanol and ultrapure water and drying.
Then, 100 mM 2-(N-morpholino)ethanesulfonic acid and 500 mM sodium chloride were added to ultrapure water to make a pH 5.5 solution, to which 5 mM N-hydroxysulfoscurcinimide sodium salt and 40 mM N,N'-diisopropylcarbodiimide were added to prepare treatment solution 2. Treatment solution 2 was dropped onto the electrode, which was then allowed to stand at room temperature for 30 minutes, washed with ethanol, and dried.
Furthermore, streptavidin was added to the ultrapure water to a concentration of 1 mg/mL to prepare a streptavidin solution. Sodium carbonate was added to the ultrapure water to a concentration of 15 mM, and sodium bicarbonate was added to the ultrapure water to a concentration of 35 mM to prepare a carbonate buffer having a pH of 9.6. The streptavidin solution and the carbonate buffer were mixed in a volume ratio of 1:1 to prepare treatment solution 3. Treatment solution 3 was dropped onto the electrode, left to stand at room temperature for 2 hours, washed with ultrapure water, and dried.
Then, 2-aminoethanol was added to Dulbecco's phosphate buffered saline to a concentration of 1 M to prepare treatment solution 4. Treatment solution 4 was dropped onto the electrode, which was then left to stand at room temperature for 15 minutes, washed with ultrapure water, and dried.
Human serum albumin was added to Dulbecco's phosphate buffered saline to a concentration of 0.1 weight percent, and Tween 20 (polyoxyethylene sorbitan monolaurate) was further added to a concentration of 0.05 weight percent to prepare treatment solution 5. Treatment solution 5 was dropped onto the electrode, which was then allowed to stand at room temperature for 15 minutes, washed with Dulbecco's phosphate buffered saline, and dried.
Biotin-labeled anti-oxytocin antibody was added to the treatment solution 5 to a concentration of 30 μg/mL to prepare treatment solution 6. Treatment solution 6 was dropped onto the electrode, which was then allowed to stand at room temperature for 30 minutes, washed with Dulbecco's phosphate buffered saline, and dried to obtain a detection electrode with an oxytocin antibody immobilized thereon.

Example 1
Manufacture of a transistor-type sensor using a treated electrode A transistor-type sensor of the present invention was manufactured by connecting the oxytocin antibody-immobilized detection electrode obtained in Electrode Preparation Example 1 to the gate electrode of a transistor obtained by the manufacturing method shown in Fig. 3. In the transistor-type sensor of this example, the gate terminal (not shown) of a semiconductor parameter analyzer was connected to a counter electrode (Ag/AgCl).

Confirmation of Operation of Organic Semiconductor Transistor The gate electrode, source electrode, and drain electrode of the transistor obtained by the manufacturing method shown in FIG. 3 were connected to the gate terminal, source terminal, and drain terminal of a semiconductor parameter analyzer (terminals not shown), respectively.
Electrical measurements were performed with a source-drain voltage (Vd) of -1.0 V and a gate voltage (Vg) of 0.5 to -3 V, and it was confirmed that the organic semiconductor transistor operates at a Vg of -3 V or less, the source-gate current (Ig) is smaller than the source-drain current (Id) by at least one order of magnitude, and the threshold voltage shift is sufficiently small.

(Oxytocin detection experiment: Confirmation of threshold voltage)
The electrodes were immersed in oxytocin solutions adjusted to concentrations of 1, 5, 7, 10, 20, 30, and 50 pg/mL in microtubes, and left to stand for 1 hour in an incubator set at 37° C. This operation was set so that the antigen-antibody reaction would proceed sufficiently.
When the time response was checked, it was confirmed that the threshold voltage shifted in less than 10 minutes (see FIG. 6).

Measurement experiments were carried out at each concentration.
For the oxytocin solution in the microtube, the oxytocin antibody-immobilized detection electrode was connected to the gate electrode of the transistor obtained by the manufacturing method shown in Figure 3, and a counter electrode (Ag/AgCl) was inserted, and this was connected to the gate terminal (not shown) of a semiconductor parameter analyzer.
The measurement was performed with a source-drain voltage (Vd) of −1.0 V and a gate voltage (Vg) of 0.5 to −3 V. The measurement was performed six times.

The measurement results are shown in Figure 7. This is the current-voltage characteristic obtained by taking the average of the current value of six measurements for each concentration. Figure 7 shows that the current value decreases as the concentration increases.
FIG. 8 is a graph in which the 1/2 power of the current value is plotted on the vertical axis, and it is clear that even if the saturation region of the transistor characteristics is expanded, the curve moves with increasing concentration.
9 is a graph in which the threshold voltage calculated from the 1/2 power of the current value is plotted on the vertical axis and the concentration is plotted on the horizontal axis. It was found that the threshold voltage shifts in the negative direction as the concentration changes.
The graph embedded in Figure 9 is a graph showing the amount of change in threshold voltage, where the threshold voltage Vth(n) for each concentration is normalized by the threshold voltage Vth(0) for a concentration of 0. Vth-Shift(n) can be calculated by subtracting Vth(0) from Vth(n) and dividing the result by Vth(0). This graph also shows that the threshold voltage shifts significantly with changes in concentration.

Comparative Example 1
An experiment similar to that in Example 1 was carried out using a silicon field effect transistor manufactured by ON Semiconductor, product name BSS84, produced using a normal semiconductor manufacturing process, instead of the organic semiconductor transistor.
The measurement results (current-voltage characteristics) are shown in Fig. 10. Fig. 10 does not show any relationship between increasing the concentration and decreasing the current value.
FIG. 11 corresponds to FIG. 9 of Example 1, and in this figure too, no shift in the curve due to differences in concentration was observed even when the saturation region of the transistor characteristics was enlarged.
FIG. 12 shows the calculation results of the threshold voltage corresponding to FIG. 10 of Example 1. However, there was no change in the threshold voltage, and oxytocin could not be detected.
The transistors used in the measurements were confirmed to have sufficiently small changes in threshold voltage due to multiple measurements.
The figure embedded in FIG. 12 is a graph showing the amount of change in threshold voltage, and compared with Example 1, it was found that there was almost no change.

(Oxytocin detection experiment: confirmation of current Id)
The current Id obtained in the detection experiment of Example 1 was plotted for each oxytocin concentration. The results are shown in Figure 13. Specifically, Figure 13 is a graph obtained by taking the average of the current values of six measurements for each concentration, calculating the voltage corresponding to the current value that is half the current value at -3.0 V at a concentration of 0, and determining the current value at that voltage for each concentration. It was found that the current value decreased as the concentration increased.
The graph embedded in Figure 13 is a graph showing the amount of change in the current value Id, normalized by the current value Id(0) at a concentration of 0 for the current value Id(n). Id-Shift(n) can be calculated by subtracting Id(0) from Id(n) and dividing the result by Id(0). This graph also shows that the current value changes significantly with changes in concentration.

For the detection experiment of Comparative Example 1, the obtained current Id was plotted for each oxytocin concentration. The results are shown in Figure 14. It was found that with the transistor of Comparative Example 1, the current value was unlikely to change significantly even when the concentration was increased. From Figure 14, it can be seen that the current value increases from 1 pg/mL, but because the characteristics of the sensor mean that the current is expected to change in a decreasing direction, this is considered to be an error. The figure embedded in Figure 14 is a graph showing the amount of change in the current value Id. It was found that the amount of change in the current value was small even when the concentration was increased.

The organic semiconductor transistor-type sensor of the present invention that uses an antigen-antibody reaction is extremely simple as a device for measuring antigens or antibodies, and has industrial applicability.

T Field effect transistor EL Detection electrode 1 Substrate 2 Gate electrode 3 Gate insulating film 4 Source electrode 5 Drain electrode 6 Bank 7 Organic semiconductor 8 Sealing film 9 Conductive wire 10 Detection electrode substrate 11 Detection electrode (extension gate)
12 Counter electrode 13 Aqueous solution containing a detection target 14 Active layer A Linker B Reactive group C Streptavidin D Biotin E Antibody F Antigen

Claims (12)

A transistor-type sensor comprising a detection electrode for detecting an antigen or an antibody by capturing the antigen or the antibody, and an organic semiconductor transistor having a gate electrode connected to the detection electrode, in which, when the detection electrode detects an antigen, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part, and when the detection electrode detects an antibody, an antibody capable of undergoing an antigen-antibody reaction with the antigen to be detected is bound to the surface of the detection electrode via a linker and a binding part. The transistor-type sensor according to claim 1, wherein the binding portion is composed of streptavidin and biotin, or composed of avidin and biotin. The transistor-type sensor according to claim 2, wherein the antigen or the antibody is chemically bound to the streptavidin or the avidin. The transistor-type sensor according to any one of claims 1 to 3, wherein the molecular length of the linker is 0.3 to 2.6 nm. The transistor-type sensor according to any one of claims 1 to 4, wherein the antigen is oxytocin and the antibody is an oxytocin antibody. The transistor-type sensor according to claim 1, wherein the organic semiconductor transistor is a p-type semiconductor. The transistor-type sensor according to claim 1, which detects the detection target in a solution or dispersion. A method for quantitatively measuring an antigen or an antibody by using a transistor-type sensor, comprising:
A step of contacting an antigen or an antibody to be detected with the detection electrode of the transistor-type sensor according to claim 1;
measuring a current Id flowing between a drain electrode and a source electrode of the transistor -type sensor for each concentration of the detection target, and obtaining a concentration-current Id relationship curve;
a step of contacting the detection electrode with the detection target having an unknown concentration and obtaining a current Id of the detection target having an unknown concentration;
comparing the current Id of the detection target, the concentration of which is unknown, with the concentration-current Id relationship curve to determine the concentration of the current Id of the detection target, the concentration of which is unknown. A method for quantitatively measuring an antigen or an antibody by using a transistor-type sensor, comprising:
A step of contacting an antigen or an antibody to be detected with the detection electrode of the transistor-type sensor according to claim 1;
measuring a threshold voltage for each concentration of the detection target and obtaining a concentration-threshold voltage relationship curve;
a step of contacting the detection electrode with the target substance having an unknown concentration, and obtaining a threshold voltage of the target substance having an unknown concentration;
comparing a threshold voltage of the detection target having an unknown concentration with the concentration-threshold voltage relationship curve, and determining the concentration of the threshold voltage of the detection target having an unknown concentration. The measurement of the threshold voltage includes:
applying a voltage Vd to a drain electrode of the organic semiconductor transistor with respect to a source electrode, and applying a voltage Vg to a counter electrode with respect to the source electrode;
obtaining a Vg-Id curve by sweeping the Vg and measuring a current Id flowing between the drain electrode and the source electrode;
and obtaining a value of a threshold voltage using the Vg-Id curve. The measurement method according to claim 9, wherein the transistor-type sensor further includes a counter electrode, and the detection electrode and the counter electrode are brought into contact with the detection target. The measurement method according to claim 11 , wherein the detection target is contained in a solution or dispersion, and detection is performed in a state in which the detection electrode and the counter electrode are immersed in the solution or dispersion.

Images