CN112924745A - Nanopore gene sequencing micro-current detection device - Google Patents
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Abstract
The invention discloses a nanopore gene sequencing micro-current detection device, which comprises a micro-current detection circuit, a voltage constant circuit, a sensor electrode and a common electrode, wherein the sensor electrode and the common electrode are oppositely arranged; the voltage constant circuit comprises an operational amplifier, a feedback resistor, a differential amplifier and a bias output circuit, wherein the negative input end of the operational amplifier is electrically connected with one end of the sensor electrode and one end of the feedback resistor respectively, and the common electrode is grounded; the positive input end of the operational amplifier is electrically connected with the negative input end of the differential amplifier and the output end of the bias output circuit respectively, and the output end of the operational amplifier is electrically connected with the positive input end of the differential amplifier and the other end of the feedback resistor respectively. The nanopore gene sequencing micro-current detection device disclosed by the invention can solve the technical problem of low measurement precision of the existing micro-current detection device.
Description
Technical Field
The invention belongs to the technical field of electronics, and particularly relates to a nanopore gene sequencing micro-current detection device.
Background
At present, the third generation gene sequencing technology based on single molecule level has more remarkable advantages in reading length, cost and speed, and is one of the hot spots of the current research. The principle of nanopore gene sequencing is that voltage acts on an electrolyte chamber through at least two electrodes, so that ions or other small molecule substances in the electrolyte chamber can penetrate through a nanopore to form a stable and detectable ion current, and then the current change amplitude caused when the DNA passes through the nanopore is different according to the chemical property difference of different bases on the DNA molecule, so that the sequence information of the DNA is judged. Therefore, the accurate measurement of the weak characteristic current change generated when the DNA single strand passes through the nanopore is one of the key technologies for realizing high-accuracy gene sequencing.
However, the conventional micro-current detection device for measuring the weak characteristic current change generally has the technical problem of low measurement precision, and is specifically characterized in that in the measurement process, when a certain voltage is applied between two electrodes positioned on two sides of a lipid membrane to drive single-stranded DNA to pass through a nanopore, the pressure difference between the two electrodes is easily fluctuated due to the existence of an illegal drawing process, and meanwhile, the characteristic current change generated when the DNA single-stranded DNA passes through the nanopore is very weak, generally in the picoampere level, so that the fluctuation of the pressure difference greatly influences the detection precision of the micro-current, and further influences the accuracy of gene sequencing.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a nanopore gene sequencing micro-current detection device, aiming at solving the technical problem of low measurement precision of the existing micro-current detection device.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a nanopore gene sequencing micro-current detection device comprises a micro-current detection circuit, wherein the micro-current detection circuit comprises a voltage constant circuit, a sensor electrode and a common electrode which are oppositely arranged; the voltage constant circuit comprises an operational amplifier, a feedback resistor, a differential amplifier and a bias output circuit, wherein the negative electrode input end of the operational amplifier is electrically connected with the sensor electrode and one end of the feedback resistor respectively, and the common electrode is grounded; the positive input end of the operational amplifier is electrically connected with the negative input end of the differential amplifier and the output end of the bias output circuit respectively, and the output end of the operational amplifier is electrically connected with the positive input end of the differential amplifier and the other end of the feedback resistor respectively.
Further, the voltage constant circuit further comprises a feedback capacitor, and the feedback capacitor is connected with the feedback resistor in parallel.
Furthermore, the micro-current detection circuit further comprises an analog-to-digital converter and a data processor, the bias output circuit comprises a digital-to-analog converter, an output end of the differential amplifier is electrically connected with an input end of the analog-to-digital converter, and an output end of the analog-to-digital converter is electrically connected with an input end of the data processor; the input end of the digital-to-analog converter is electrically connected with the output end of the data processor, and the output end of the digital-to-analog converter is electrically connected with the anode input end of the operational amplifier.
Furthermore, the micro-current detection circuit further comprises a denoising circuit, and the denoising circuit is arranged on a path between the output end of the differential amplifier and the input end of the analog-to-digital converter.
Furthermore, the micro-current detection circuit further comprises an input offset compensation circuit, and an output end of the input offset compensation circuit is electrically connected with the sensor electrode, one end of the feedback resistor and a negative input end of the operational amplifier respectively.
The micro-current detection circuit is characterized by further comprising a first adder, a zero-point overcharge compensation circuit, a high-frequency compensation circuit and a bias voltage post-compensation circuit, wherein the input end of the first adder is electrically connected with the output end of the zero-point overcharge compensation circuit and the output end of the bias voltage post-compensation circuit respectively, and the output end of the first adder is electrically connected with the input end of the high-frequency compensation circuit; the output end of the high-frequency compensation circuit is electrically connected with the input end of the de-noising circuit, and the input end of the zero point overcharge compensation circuit is electrically connected with the output end of the differential amplifier.
Furthermore, the nanopore gene sequencing micro-current detection device further comprises a first compensation capacitor, a first time delay circuit and a step voltage output circuit, wherein one end of the first compensation capacitor is electrically connected with the negative electrode input end of the operational amplifier, and the other end of the first compensation capacitor is electrically connected with the output end of the step voltage output circuit through the first time delay circuit.
Furthermore, the nanopore gene sequencing micro-current detection device further comprises a second compensation capacitor, a second time delay circuit and a proportion regulation circuit, wherein one end of the second compensation capacitor is electrically connected with the negative input end of the operational amplifier, and the other end of the second compensation capacitor is electrically connected with the output end of the step voltage output circuit after sequentially passing through the proportion regulation circuit and the second time delay circuit.
Furthermore, the nanopore gene sequencing micro-current detection device further comprises a second adder and a compensation circuit of a correction loop, wherein the input end of the second adder is electrically connected with the output end of the compensation circuit of the correction loop, the output end of the first time delay circuit and the output end of the proportion regulation circuit respectively, and the output end of the adder is electrically connected with the other end of the first compensation capacitor and the other end of the second compensation capacitor respectively; and the input end of the compensation circuit of the correction loop is electrically connected with the output end of the differential amplifier.
Furthermore, the nanopore gene sequencing micro-current detection device further comprises a membrane capacitance detection circuit, wherein the membrane capacitance detection circuit comprises a controller, a timer, a first resistor and a second resistor; one end of the first resistor is electrically connected with one end of the second resistor and the discharge end of the timer respectively, and the other end of the first resistor is connected with a power supply end; the other end of the second resistor is electrically connected with the sensor electrode, the low-level trigger end of the timer and the high-level trigger end of the timer respectively; the output end of the timer is electrically connected with the input end of the controller.
Compared with the prior art, the invention has the beneficial effects that:
according to the nanopore gene sequencing micro-current detection device, a specially designed voltage constant circuit is arranged, so that stable and constant driving voltage for driving DNA molecules to pass through a nanopore can be formed between a sensor electrode and a common electrode, the pressure difference between the sensor electrode and the common electrode is not easy to fluctuate due to the existence of an illegal pulling process in the gene sequencing process, the detection precision of micro-current is prevented from being influenced by the fluctuation of the pressure difference, and the accuracy of gene sequencing is effectively improved; in addition, this voltage constant circuit still can realize converting the current signal who detects into voltage signal's function, so, only need through a circuit alright realize converting current signal into voltage signal's function and for providing stable and invariable drive voltage's function between the two electrodes simultaneously, and need not two circuits of the corresponding function of separate design respectively, thereby reducible electronic components's quantity, be favorable to integrating, improve detection device's integrated level, in order to satisfy the nanopore current detection better and to small, the device requirement that the integrated level is high.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a nanopore gene sequencing micro-current detection device in an embodiment of the invention;
FIG. 2 is a schematic diagram of a membrane capacitance detection circuit according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a nanopore gene sequencing micro-current detection device in another embodiment of the present invention.
Description of reference numerals:
11-sensor electrode, 12-common electrode;
2-a voltage constant circuit, 21-an operational amplifier, 22-a feedback resistor, 23-a differential amplifier, 24-a bias output circuit, 241-a digital-to-analog converter and 25-a feedback capacitor;
3-lipid membrane, 31-nanopore, 4-DNA molecule, 5-analog-to-digital converter, 6-data processor;
7-membrane capacitance detection circuit, 71-controller, 72-timer, 73-first resistor, 74-second resistor, 8-denoising circuit;
91-input offset compensation circuit, 92-offset voltage post-compensation circuit, 93-zero point overcharge compensation circuit, 94-first adder, 95-high frequency compensation circuit, 96-first compensation capacitor, 97-second adder, 98-first time delay circuit, 99-step voltage output circuit, 910-second compensation capacitor, 911-proportion regulation circuit, 912-second time delay circuit and 913-compensation circuit of correction loop.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, an embodiment of the present invention provides a nanopore gene sequencing micro-current detection device for measuring a weak characteristic current change generated when a DNA molecule 4 passes through a nanopore 31 on a lipid membrane 3, the nanopore gene sequencing micro-current detection device including a micro-current detection circuit including a voltage constant circuit 2, and a sensor electrode 11 and a common electrode 12 disposed opposite to each other; the voltage constant circuit 2 comprises an operational amplifier 21, a feedback resistor 22, a differential amplifier 23 and a bias output circuit 24, wherein the negative input end of the operational amplifier 21 is electrically connected with one end of the sensor electrode 11 and one end of the feedback resistor 22 respectively, and the common electrode 12 is grounded; the positive input end of the operational amplifier 21 is electrically connected to the negative input end of the differential amplifier 23 and the output end of the bias output circuit 24, and the output end of the operational amplifier 21 is electrically connected to the positive input end of the differential amplifier 23 and the other end of the feedback resistor 22. Illustratively, the sensor electrode 11 and the common electrode 12 are respectively located on two sides of the lipid membrane 3, wherein the sensor electrode 11 and the common electrode 12 may be inert electrodes such as platinum electrode and gold electrode.
The usage principle of the nanopore gene sequencing micro-current detection device of the embodiment is as follows:
in one electrolyte chamber, the lipid membrane 3 divides the solution in the electrolyte chamber into upper and lower two regions, and a plurality of nanopores 31 for proteins such as hemolysin, MspA, CsgG, and the like are embedded in the lipid membrane 3. Before the experiment, the common electrode 12 used as a ground is placed on one side of the lipid membrane 3, and the sensor electrode 11 is placed on the other side of the lipid membrane 3, wherein the common electrode 12 can be shared by a plurality of nanopores 31, and the sensor electrode 11 can be placed one for each nanopore 31. When gene sequencing is performed, a bias voltage is provided to the positive input terminal of the operational amplifier 21 through the bias output circuit 24, since the feedback resistor 22 connected across the negative input terminal and the output terminal of the operational amplifier 21 can provide negative feedback, thus making the voltage at the negative input of the operational amplifier 21 equal to the voltage at the positive input of the operational amplifier 21, when the bias output circuit 24 provides a bias voltage to the positive input terminal of the operational amplifier 21, the bias voltage is applied to the sensor electrode 11 so that the voltage between the sensor electrode 11 and the common electrode 12 is driven to the same potential as the voltage generated by the bias output circuit 24, and thus, by controlling the output voltage of the bias output circuit 24 to be kept constant, that is, it is ensured that a stable and constant driving voltage for driving the DNA molecules 4 through the nanopore 31 can be formed between the sensor electrode 11 and the common electrode 12; in addition, any current flowing through the sensor electrode 11 must flow through the feedback resistor 22, and since no current flows through the negative input terminal of the operational amplifier 21, when the micro-current formed when the ions or other small molecule substances in the electrolyte chamber pass through the nanopore 31 passes through the feedback resistor 22, a voltage field is generated across the feedback resistor 22, so that the detected current signal is converted into a voltage signal; in the process of driving the DNA molecule 4 through the nanopore 31, the output voltage of the operational amplifier 21 is equal to the product of the feedback resistor 22 and the input current (i.e., the detected micro-current) plus the bias voltage output by the bias output circuit 24, the output voltage is input to the differential amplifier 23, then the differential amplifier 23 subtracts the bias voltage from the output voltage, and amplifies (for example, amplifies by 10 times) the remaining voltage signal (i.e., the voltage signal obtained by converting the detected current signal through the feedback resistor 22) and outputs the amplified voltage signal to the subsequent measurement circuit, since the feedback resistor 22 is known, the detected micro-current only needs to be obtained by simple calculation (dividing the measured voltage by the feedback resistor 22) according to the voltage measured in the subsequent measurement circuit).
According to the nanopore gene sequencing micro-current detection device provided by the embodiment, the specially designed voltage constant circuit 2 is arranged, so that stable and constant driving voltage for driving the DNA molecules 4 to pass through the nanopore 31 can be formed between the sensor electrode 11 and the common electrode 12, the pressure difference between the sensor electrode 11 and the common electrode 12 is not easy to fluctuate due to the existence of an illegal pulling process in the gene sequencing process, the detection precision of micro-current can be prevented from being influenced by the fluctuation of the pressure difference, and the accuracy of gene sequencing is effectively improved; in addition, this voltage constant circuit 2 still can realize converting the current signal who detects into voltage signal's function, so, only need through a circuit alright realize converting current signal into voltage signal's function and for providing stable and invariable drive voltage's function between sensor electrode 11 and the common electrode 12 simultaneously, and need not respectively two circuits of independent design corresponding function, thereby reducible electronic components's quantity, be favorable to integrating, improve detection device's integrated level, with satisfy the device requirement that nanopore 31 current detection is small to, the integrated level is high better.
Further, referring to fig. 1, in an exemplary embodiment, the micro-current detection circuit further includes an analog-to-digital converter 5 and a data processor 6, the bias output circuit 24 includes a digital-to-analog converter 241, an output terminal of the differential amplifier 23 is electrically connected to an input terminal of the analog-to-digital converter 5, and an output terminal of the analog-to-digital converter 5 is electrically connected to an input terminal of the data processor 6; the input end of the digital-to-analog converter 241 is electrically connected with the output end of the data processor 6, and the output end of the digital-to-analog converter 241 is electrically connected with the positive input end of the operational amplifier 21. Specifically, the data processor 6 mainly comprises a single chip microcomputer, an FPGA (Field Programmable Gate Array) processor, a data transmission module, and the like, and can be used for controlling the bias voltage output by the digital-to-analog converter 241, the sampling frequency of the analog-to-digital converter 5, the time for starting detection of a subsequent film capacitor, and the like; the input end of the FPGA processor is electrically connected to the output end of the analog-to-digital converter 5, and the output end of the FPGA processor is electrically connected to the input end of the digital-to-analog converter 241 and an upper computer (not shown in the figure).
In this embodiment, based on the above structural design, when performing gene sequencing, a constant digital signal can be output to the digital-to-analog converter 241 through the FPGA processor, and the digital-to-analog converter 241 converts the received digital signal into a voltage signal and outputs the voltage signal to the positive input end of the operational amplifier 21, so that a constant bias voltage can be applied to the sensor electrode 11, so that the voltage between the sensor electrode 11 and the common electrode 12 is driven to the same potential as the voltage generated by the bias output circuit 24, and a stable and constant driving voltage for driving the DNA molecule 4 to pass through the nanopore 31 can be formed between the sensor electrode 11 and the common electrode 12; meanwhile, the differential amplifier 23 amplifies the converted voltage signal and outputs the amplified voltage signal to the analog-to-digital converter 5, and the analog-to-digital converter 5 converts the received voltage signal into a digital signal and outputs the digital signal to the FPGA processor for data processing, so that the current magnitude of the micro-current can be measured; and the FPGA processor transmits the processed related data to an upper computer, and the upper computer performs large-scale data analysis to realize the identification and assembly of the base sequence of the DNA molecule 4.
Further, referring to fig. 1 to 3, in an exemplary embodiment, the nanopore gene sequencing micro-current detection device further includes a membrane capacitance detection circuit 7, and the membrane capacitance detection circuit 7 includes a controller 71, a timer 72, a first resistor 73, and a second resistor 74; one end of the first resistor 73 is electrically connected to one end of the second resistor 74 and the discharging end of the timer 72, respectively, and the other end is connected to the power supply terminal VDD; the other end of the second resistor 74 is electrically connected to the sensor electrode 11, the low-level trigger end of the timer 72, and the high-level trigger end of the timer 72, respectively; an output of the timer 72 is electrically connected to an input of the controller 71. In specific implementation, the timer 72 may be a 555 timer, and a single chip microcomputer of AT89C51, STM32, or the like may be used as the controller 71, where the single chip microcomputer in the data processor 6 may be used as the controller 71 in order to reduce the number of electronic components used and improve the integration of the apparatus.
In the present embodiment, based on the above structural design, the function of detecting the membrane capacitance (the lipid membrane 3 can be equivalent to one capacitance in the solution, which is referred to as a membrane capacitance) can be realized (that is, the capacitance of the membrane capacitance is detected, wherein the larger the detected capacitance of the membrane capacitance is, the smaller the membrane thickness of the lipid membrane 3 is), so as to judge whether the membrane thickness of the lipid membrane 3 placed in the solution of the electrolyte chamber meets the requirement of the subsequent gene sequencing, thereby improving the practicability of the device. Specifically, considering that the thickness of the lipid membrane 3 affects the precision of the detection of the micro-current, selecting the lipid membrane 3 with an appropriate thickness for the experiment is advantageous to further improve the precision of the detection of the micro-current. The working principle of the membrane capacitance detection circuit 7 of the present embodiment is as follows:
after the power supply end VDD is powered on, the sensor electrode 11 is charged through the first resistor 73 and the second resistor 74, when the voltage between the sensor electrode 11 and the common electrode 12 rises to a certain amplitude, the 555 timer is reset, meanwhile, a discharge triode in the 555 timer is conducted, the sensor electrode 11 is discharged through the two resistors and the discharge triode in the 555 timer, so that the voltage between the sensor electrode 11 and the common electrode 12 is reduced, the 555 timer is set, the process is repeated in this way, a periodic pulse signal can be obtained at the output end of the 555 timer, the controller 71 obtains the pulse signal and calculates the capacitance value of the membrane capacitor according to the frequency of the pulse signal (regarding the measurement of the frequency of the pulse signal, a singlechip can be used as the controller 71, and an input capture mode is adopted through the timer/timer in the singlechip, a digital frequency measurement system is formed, firstly, a timer records the time of two rising edge or falling edge pulse intervals to measure a period time T of a pulse signal, the period time T is converted into a frequency f, and then according to a formula: the capacitance C of the film capacitor can be calculated by 1.44/[ (R1+2R2) × C) ═ 1/T, where R1 is the resistance of the first resistor 73 and R2 is the resistance of the second resistor 74).
Further, referring to fig. 3, in an exemplary embodiment, the voltage stabilizing circuit 2 further includes a feedback capacitor 25, and the feedback capacitor 25 is connected in parallel with the feedback resistor 22. The feedback capacitor 25 is preferably a variable capacitor with adjustable capacitance.
In the present embodiment, based on the above structural design, by adding the feedback capacitor 25 connected in parallel with the feedback resistor 22, the bandwidth of the feedback resistor 22 can be limited to the frequency of 1/(2 pi · Rc) (where R is the resistance of the feedback resistor 22 and c is the capacitance of the feedback capacitor 25), so that the output voltage noise of the feedback resistor 22 can be effectively reduced and aliasing can be prevented from occurring when the analog-to-digital converter 5 samples. In particular, the bandwidth of the feedback resistor 22 is preferably limited to a frequency of 10kHz by adjusting the capacitance of the feedback capacitor 25.
Further, referring to fig. 3, in an exemplary embodiment, the micro-current detection circuit further includes a de-noising circuit 8, the de-noising circuit 8 being disposed in a path between the output of the differential amplifier 23 and the input of the analog-to-digital converter 5. In particular, an existing low-pass filter may be used as the denoising circuit 8.
In the embodiment, based on the above structural design, the noise removal circuit 8 is additionally arranged on the path between the output end of the differential amplifier 23 and the input end of the analog-to-digital converter 5, so that noise and other interference signals generated during DNA single-molecule perforation can be filtered, and the accuracy of micro-current detection can be further improved.
Further, referring to fig. 3, in an exemplary embodiment, the micro-current detection circuit further includes an input offset compensation circuit 91, and an output terminal of the input offset compensation circuit 91 is electrically connected to the sensor electrode 11, one terminal of the feedback resistor 22, and the negative input terminal of the operational amplifier 21.
In the present embodiment, based on the above structural design, the input offset compensation circuit 91 may perform internal or external offset zeroing on the operational amplifier 21 to compensate the input offset for zeroing the output offset voltage of the operational amplifier 21, which is beneficial to further improving the precision of micro-current detection. It should be noted that the specific circuit structure of the input offset compensation circuit 91 is a conventional structure, and is not described herein again.
Further, referring to fig. 3, in an exemplary embodiment, the micro-current detecting circuit further includes a first adder 94, a zero point overcharge compensating circuit 93, a high-frequency compensating circuit 95, and a bias voltage post-compensating circuit 92, wherein an input terminal of the first adder 94 is electrically connected to an output terminal of the zero point overcharge compensating circuit 93 and an output terminal of the bias voltage post-compensating circuit 92, respectively, and an output terminal of the first adder 94 is electrically connected to an input terminal of the high-frequency compensating circuit 95; the output end of the high-frequency compensation circuit 95 is electrically connected to the input end of the noise removal circuit 8, and the input end of the zero point overcharge compensation circuit 93 is electrically connected to the output end of the differential amplifier 23.
In this embodiment, based on the above structural design, the noise generated in the micro-current detection process is subjected to multiple compensation processing, which is beneficial to further improving the precision of micro-current detection. Specifically, by providing the high-frequency compensation circuit 95, the bandwidth of the voltage signal output by the differential amplifier 23 can be increased, so as to solve the problem that the high-frequency component of the voltage signal amplified by the differential amplifier 23 may be weakened; meanwhile, the zero overcharge compensation circuit 93 is arranged between the differential amplifier 23 and the high-frequency compensation circuit 95, so that the zero of the operational amplifier 21 can be overcharged and compensated, and the phenomenon that the zero of the operational amplifier 21 generates overcharge on the input signal of the high-frequency compensation circuit 95 is avoided; in addition, the zero point overcharge compensation circuit 93 performs the zero point overcharge compensation on the voltage signal output by the differential amplifier 23, and the offset voltage post-compensation circuit 92 is added to perform the offset voltage post-compensation on the voltage signal output by the zero point overcharge compensation circuit 93, thereby eliminating the negative effect of the offset voltage. It should be noted here that specific circuit structures of the zero overcharge compensation circuit 93, the high-frequency compensation circuit 95, and the offset voltage post-compensation circuit 92 are all conventional structures, and are not described herein again.
Further, referring to fig. 3, in an exemplary embodiment, the nanopore gene sequencing micro-current detection device further includes a first compensation capacitor 96, a first time delay circuit 98, and a step voltage output circuit 99, wherein one end of the first compensation capacitor 96 is electrically connected to the negative input terminal of the operational amplifier 21, and the other end is electrically connected to the output terminal of the step voltage output circuit 99 through the first time delay circuit 98.
In this embodiment, it is considered that during gene sequencing, the excess charges in the solution in the electrolyte chamber are arranged on both sides of the sensor electrode 11 and the common electrode 12 tightly, and form an electrode capacitance similar to a plate capacitor, which is non-purely capacitive, and the charge and discharge current thereof can seriously submerge the detection signal, so that the electrode capacitance needs to be compensated. Specifically, in the present embodiment, based on the above structural design, a branch circuit using the first compensation capacitor 96 as a charging/discharging current injection element is connected to the positive input end of the operational amplifier 21 to provide current for charging/discharging of the electrode capacitor, and a synchronous step voltage is input to the other end of the first compensation capacitor 96, so that the current passing through the first compensation capacitor 96 is exactly equal to the charging/discharging current of the electrode capacitor to be eliminated, and the direction is opposite to the charging/discharging current; meanwhile, due to the existence of the electrode capacitance time constant, the step voltage signal applied to the first compensation capacitor 96 also needs to be output after passing through the first time delay circuit 98 with adjustable time constant, so that the compensation current is better matched with the electrode capacitance current. Therefore, the precision of micro-current detection is further improved.
Further, referring to fig. 3, in an exemplary embodiment, the nanopore gene sequencing micro-current detection device further includes a second compensation capacitor 910, a second time delay circuit 912, and a proportional adjustment circuit 911, wherein one end of the second compensation capacitor 910 is electrically connected to the negative input terminal of the operational amplifier 21, and the other end of the second compensation capacitor is electrically connected to the output terminal of the step voltage output circuit 99 after passing through the proportional adjustment circuit 911 and the second time delay circuit 912 in sequence.
In this embodiment, it is considered that the lipid membrane 3 can be equivalent to a capacitor (referred to as a membrane capacitor) in the solution, and the time constant of the membrane capacitor is higher than that of the electrode capacitor, which may cause output distortion, so that the membrane capacitor needs to be compensated. Specifically, in the present embodiment, based on the above structural design, a second compensation capacitor 910 connected in parallel with the first compensation capacitor 96 is connected to the positive input end of the operational amplifier 21, the second compensation capacitor 910 is used as a branch of the charging and discharging current injection element to provide current for charging and discharging the film capacitor, and a synchronous step voltage is input to the other end of the second compensation capacitor 910, so that the current passing through the second compensation capacitor 910 is exactly equal to the charging and discharging current of the film capacitor to be eliminated, and the direction of the current is opposite; meanwhile, due to the existence of the membrane capacitance time constant, the step voltage signal applied to the second compensation capacitor 910 needs to pass through the second time delay circuit 912 and the proportional regulating circuit 911 and then be output, so that the compensation current is better matched with the membrane capacitance current. Therefore, the precision of micro-current detection is further improved.
Further, referring to fig. 3, in an exemplary embodiment, the nanopore gene sequencing micro-current detection device further includes a second adder 97 and a compensation circuit 913 of the correction loop, an input terminal of the second adder 97 is electrically connected to an output terminal of the compensation circuit 913 of the correction loop, an output terminal of the first time delay circuit 98, and an output terminal of the proportional regulating circuit 911, respectively, and an output terminal of the adder is electrically connected to the other terminal of the first compensation capacitor 96 and the other terminal of the second compensation capacitor 910, respectively; the input of the compensation circuit 913 of the correction loop is electrically connected to the output of the differential amplifier 23. Illustratively, an input of the compensation circuit 913 of the correction loop is electrically connected to an output of the de-noising circuit 8.
In this embodiment, considering that the nanopore 31 on the lipid membrane 3 can be equivalent to several resistors connected in series in the solution, the current flowing through the several resistors connected in series will cause extra voltage drop, so that the bandwidth of the system is not expected, and the rapid measurement of DNA will be affected, so that the nanopore 31 needs to be compensated. Specifically, in the present embodiment, based on the above structural design, a compensation channel is applied to the output end of the operational amplifier 21, and a certain proportion of the output voltage of the operational amplifier 21, which is proportional to the detection current, is taken out to offset a part of the voltage drop, so as to form a compensation circuit of a correction loop, thereby improving the time resolution of the detection current signal and improving the bandwidth capability of the system, so as to meet the index of DNA rapid measurement.
It should be noted that other contents of the nanopore gene sequencing micro-current detection device disclosed by the present invention can be referred to in the prior art, and are not described herein again.
In addition, it should be noted that the descriptions related to "first", "second", etc. in the present invention are only used for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A nanopore gene sequencing micro-current detection device is characterized by comprising a micro-current detection circuit, wherein the micro-current detection circuit comprises a voltage constant circuit, a sensor electrode and a common electrode which are oppositely arranged; the voltage constant circuit comprises an operational amplifier, a feedback resistor, a differential amplifier and a bias output circuit, wherein the negative electrode input end of the operational amplifier is electrically connected with the sensor electrode and one end of the feedback resistor respectively, and the common electrode is grounded; the positive input end of the operational amplifier is electrically connected with the negative input end of the differential amplifier and the output end of the bias output circuit respectively, and the output end of the operational amplifier is electrically connected with the positive input end of the differential amplifier and the other end of the feedback resistor respectively.
2. The nanopore gene sequencing micro-current detection device of claim 1, wherein the voltage constant circuit further comprises a feedback capacitor connected in parallel with the feedback resistor.
3. The nanopore gene sequencing micro-current detection device of claim 1, wherein the micro-current detection circuit further comprises an analog-to-digital converter and a data processor, the bias output circuit comprises a digital-to-analog converter, an output of the differential amplifier is electrically connected to an input of the analog-to-digital converter, and an output of the analog-to-digital converter is electrically connected to an input of the data processor; the input end of the digital-to-analog converter is electrically connected with the output end of the data processor, and the output end of the digital-to-analog converter is electrically connected with the anode input end of the operational amplifier.
4. The nanopore gene sequencing micro-current detection device of claim 3, wherein the micro-current detection circuit further comprises a de-noising circuit disposed on a path between the output of the differential amplifier and the input of the analog-to-digital converter.
5. The nanopore gene sequencing micro-current detection device of claim 3, wherein the micro-current detection circuit further comprises an input offset compensation circuit, and an output end of the input offset compensation circuit is electrically connected to the sensor electrode, one end of the feedback resistor, and a negative input end of the operational amplifier.
6. The nanopore gene sequencing micro-current detection device according to claim 4, wherein the micro-current detection circuit further comprises a first adder, a zero-point overcharge compensation circuit, a high-frequency compensation circuit and a bias voltage post-compensation circuit, wherein an input end of the first adder is electrically connected with an output end of the zero-point overcharge compensation circuit and an output end of the bias voltage post-compensation circuit respectively, and an output end of the first adder is electrically connected with an input end of the high-frequency compensation circuit; the output end of the high-frequency compensation circuit is electrically connected with the input end of the de-noising circuit, and the input end of the zero point overcharge compensation circuit is electrically connected with the output end of the differential amplifier.
7. The nanopore gene sequencing micro-current detection device of claim 1, further comprising a first compensation capacitor, a first time delay circuit and a step voltage output circuit, wherein one end of the first compensation capacitor is electrically connected to the negative input terminal of the operational amplifier, and the other end of the first compensation capacitor is electrically connected to the output terminal of the step voltage output circuit through the first time delay circuit.
8. The nanopore gene sequencing micro-current detection device of claim 7, further comprising a second compensation capacitor, a second time delay circuit and a proportional control circuit, wherein one end of the second compensation capacitor is electrically connected to the negative input terminal of the operational amplifier, and the other end of the second compensation capacitor is electrically connected to the output terminal of the step voltage output circuit after passing through the proportional control circuit and the second time delay circuit in sequence.
9. The nanopore gene sequencing micro-current detection device according to claim 8, further comprising a second adder and a compensation circuit of a correction loop, wherein an input terminal of the second adder is electrically connected to an output terminal of the compensation circuit of the correction loop, an output terminal of the first time delay circuit and an output terminal of the proportional regulating circuit, and an output terminal of the adder is electrically connected to the other end of the first compensation capacitor and the other end of the second compensation capacitor; and the input end of the compensation circuit of the correction loop is electrically connected with the output end of the differential amplifier.
10. The nanopore gene sequencing micro-current detection device of any of claims 1 to 9, further comprising a membrane capacitance detection circuit comprising a controller, a timer, a first resistance and a second resistance; one end of the first resistor is electrically connected with one end of the second resistor and the discharge end of the timer respectively, and the other end of the first resistor is connected with a power supply end; the other end of the second resistor is electrically connected with the sensor electrode, the low-level trigger end of the timer and the high-level trigger end of the timer respectively; the output end of the timer is electrically connected with the input end of the controller.
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