JP2004511762A - Nanoscale sensor - Google Patents

Abstract

The present invention includes, but is not limited to, organic, inorganic, or other molecules or entities that may be involved in interaction events, including, but not limited to, carbon nanotubes, silicon nanotubes, nanobars, and biological materials such as microtubules and actin filaments. Create a signaling system that physically connects to nanoscale objects represented by structural elements and reports events on the submicron scale. When a molecule or object is involved in a molecular interaction event or some other interaction event, monitor the movement or change in the physical properties of the nanotube and report the occurrence of the interaction event using an ammeter or scanning Detect molecular interaction events using a tunneling microscope.

Description

[0001]
(priority)
This application is based on prior provisional application Ser. No. 60 / 238,518 filed Oct. 10, 2000 and U.S. Pat.　　　Claim the benefit of the issue. Provisional Application No. 60 / 238,518 and Non-Provisional Application No. 60 / 238,518　　　The disclosure of the present invention is incorporated herein by reference.
[0002]
(Field)
The present invention relates to an apparatus and a method for detecting a nanoscopic event. In particular, the invention relates to monitoring molecular interaction events by monitoring the effects of the interaction event based on a nanoscale object to which one or more molecules or objects involved in the event are bound. How to
[0003]
(background)
It is very useful to detect events that occur on the nanometer scale and report these events in the micro world. Such events include molecular interaction events between biomolecules, antibodies and antigens, enzymes, and other chemical and inorganic molecular events. One prior art method of detecting events on the nanometer scale relies on the use of an averaged phenomenon change. Such methods include the population method. However, the population method requires a large number of molecules and only reports the averaged characteristics of the entire population. Recently, methods have been developed that allow the investigation of a small group of molecules, or even a single molecule. The newly developed methods include scanning probe microscopy and high resolution optics.
[0004]
Scanning probe microscopes use a probe based on a micron dimensional scale to interrogate the tissue distribution or other characteristics of molecules on a solid support. In one variation, a chemical, biomolecular or modified microparticle is attached to the end of a probe and the microparticle is scanned across a surface or a sample on the surface while measuring a very small force. it can. The measurement of this force is effective when the microparticles attached to the end of the probe interact with the surface or objects deposited on the surface.
[0005]
One problem with the above research methods is that the "reporter" system involves objects based on the micron space scale or larger. In contrast, molecules of interest are often based on the sub-nanometer scale, and the activity of the molecule of interest can also occur at the nanometer scale. Detection of nanometer-scale molecular interaction events is difficult, even using advanced AFM probe technology. Compounding this problem is the fact that the probe connecting the molecules is much larger and heavier than the molecule on which it is connected, the molecule of interest. The large deviation in size between the two molecules and the probe results in low or reduced sensitivity to single molecule interaction events. Accordingly, there is a need for improved devices and methods for detecting molecular interaction events based on the micron and nanometer scale.
[0006]
Accordingly, there is a need for an apparatus and method for detecting molecular interaction events that occur on a nanometer scale. Further, there is a need to directly detect these molecular interaction events without resorting to population means. Finally, there is a need for devices and methods that can act as reporters for a single biomolecular interaction event.
[0007]
(Overview)
The present invention describes an apparatus and method for using nanotubes and other nanometric objects as part of a reporter system that allows detection of the activity of molecules or other objects on a sub-micron scale. This new device and method can improve sensitivity and responsiveness to molecular and molecular activities that occur on the nanometer scale.
In the present invention, organic, inorganic, or other objects that can be involved in molecular interaction events include, but are not limited to, carbon nanotubes, silicon nanotubes, metal nanotubes, and biological materials such as microtubules and actin filaments. Create a signaling system that physically connects to nanoscale objects, represented by structural elements, and reports events on the submicron scale.
[0008]
In one embodiment, a first nanoscale object is formed and operably positioned relative to a second nanoscale object having a molecule at one end. A first nanoscale object is connected at each end to an individual micron-sized conductive pad. Then, a current is passed through the first nanoscale object and monitored. When a molecule bound to the second nanoscale object participates in a molecular interaction event, the physical properties of the second nanoscale object change, affecting the electrical conductivity of the first nanoscale object. In the simplest case, the second nanoscale object physically moves due to the small size of the nanoscale object relative to the molecules bound thereon, affecting the current or resistance of the first nanoscale object. Exert. This current or resistance can be detected to report a molecular interaction event. Obviously, other physical properties of the nanoscale object interaction can also be measured.
[0009]
In a second embodiment of the present invention, a first nanoscale object is formed on a surface having a molecule tethered at one end and a conductive pad tethered to the other end. The position and electronic characteristics of the nanoscale object are monitored using a scanning tunneling microscope. When a molecular interaction event occurs, the position or electronic properties of the nanoscale object change. Changes in the position or electrical properties of nanotubes are detected and reported by scanning tunneling microscopy.
[0010]
The invention further comprises a first nanotube formed on the surface, a monitoring device operably attached to the first nanotube, and a second nanotube formed on the surface and in operative relationship with the first nanotube. And at least one molecule tethered to the first end of the second nanotube, wherein when a molecular interaction event occurs with the tethered molecule, the monitoring device detects the molecular interaction event. Including nanoscale sensors.
[0011]
Another embodiment of the invention is a method of detecting a molecular interaction event, wherein the first nanotube is operably coupled to a second nanotube, wherein the first nanotube comprises a first conductive material at a first end. Operably coupling to a pad, coupling to a second conductive pad at a second end, and coupling the second nanotube to a third conductive pad at a first end and to a molecule at a second end; Providing a current flowing through the nanotubes and monitoring the current through the first and second nanotubes with an ammeter, wherein when the biomolecule undergoes a molecular interaction event, the first and second nanotubes Detecting a change in conductivity with an ammeter.
[0012]
Yet another method of detecting a molecular interaction event includes connecting a molecule to a first end of a nanoscale object, scanning the nanoscale object with a scanning tunneling microscope, and when the molecule has undergone a molecular interaction event, Detecting the movement of the nanoscale object.
Also provided herein is an apparatus for detecting a molecular interaction event, comprising: a first nanotube operably attached to a surface; and an operably attached and operatively attached to the first nanotube. A second nanotube operably connected to the second nanotube and a molecule tethered to the first end of the second nanotube, wherein the molecule is involved in a molecular interaction event, and the physical properties of the first and second nanotubes can be measured. An apparatus is characterized, wherein the change occurs.
[0013]
(Detailed description)
As utilized in the present invention, a nanoscale object is monitored in such a way that a change in the physical location or other property of the object can be recognized as an indicator of a nanoscale event. For example, carbon nanotubes conduct electrons in such a way that they can act like wires, switches, and diodes. Thus, electrical resistance is one property that can be monitored to indicate the occurrence of a molecular interaction event. Other nanoscale objects can be used in the present invention. Such nanoscale objects include anatomical elements such as silicon nanotubes, microtubules and actin filaments, as well as nanobars and nanowires. The present invention utilizes carbon nanotubes as a preferred nanoscale object. Clearly, the well-defined metal properties, and the ability to create nanobars with defined physical and chemical attributes, can provide an alternative device for the nanosensor configurations described herein. . In addition, systems of this type can be more easily created in large quantities. Accordingly, replacement of other nanoscale objects, such as those listed above, can be achieved by one of ordinary skill in the art without altering the features and scope of the present invention.
[0014]
C in the form of a needle-like monolayer or multilayer tube with nanometer dimensions₆₀The synthesis of fullerene structures is known in the art. This expanded fullerene tube structure is also known as a carbon nanotube or a thin-walled carbon nanotube. Structurally, carbon nanotubes are a member of the molecular carbon class known as fullerenes. The atomic arrangement of the hexagonal carbon ring with respect to the nanotube axis varies from tube to tube and is usually helical. Nanotubes are composed of a large number of coaxial cylindrical sheets (ranging from 1 to about 50) of hexagonally arranged carbon atoms. Tubes typically have diameters of a few nanometers to tens of nanometers and lengths up to a few micrometers. Such nanotubes are well-known to those skilled in the art.
[0015]
Methods for synthesizing experimental amounts of these nanotubes using standard carbon are known. The production of nanotubes typically involves placing two water-cooled carbon electrodes, either amorphous carbon or graphite rods, in a vacuum chamber about 1 millimeter apart;^-5Pa (about 10^-7Depressurizing the chamber, backfilling the chamber with an inert gas such as helium, nitrogen, argon or hydrogen,³~ 7 × 10⁴It consists of skipping a high current arc between the electrodes while maintaining a pressure in the range of Pa (50-500 Torr) and continuously adjusting them to maintain a 1 millimeter electrode gap. As a result, carbon nanotubes and other small carbon particles grow on the negative electrode. The amount of nanotubes produced in the electrode deposit depends on how long optimal growth conditions can be maintained.
[0016]
Probes constructed in this and other ways can be used for many experiments. Wong, S.M. S. , E .; Joselevic, A .; T. Woolley, C.I. L. Cheung, and C.I. M. Lieber, Covalent functional nanotubes as nanometer-sized probes in chemistry and biology, Nature, 1998, p. 52-5; Wong, S .; S. , A. T. Woolley, E .; Joselevic, C.I. L. Cheung, and C.I. M. Lieber, Covalently Functional Single-Walled Carbon Nanotube Probe Tip for Chemical Force Microscopy, Journal of the American Chemical Society, 1998, p. 8557-8558; Wong, S .; S. , A. T. Woolley, E .; Joselevic, and C.I. M. Lieber, Functionalization of Carbon Nanotube AFM Probe Using Tip Activating Gas, Chemical Physics Letters, 306, p. 219; Dai, H .; E. FIG. W. Wong and C.I. M. Lieber, Exploring Electric Transport in Nanomaterials: Conductivity of Individual Carbon Nanotubes, Science, 1996, 272: p. 523-526; Shoushan Fan, Michael Chapline, Nathan Franklin, Thomas Tommbler, A .; Cassell and Hongjie Dai, Self-Oriented Regular Array Structure of Carbon Nanotubes and Their Functional Devices, Science, 283, 512 (1999); Soh, Alberto Morpurgo, Jing Kong, Charles Marcus, Calvin Quate and Hongjie Dai, Integrated Nanotube Circuit: Controlled Growth and Ohmic Contact for Single-Walled Carbon Nanotubes, Appl. Phys, Lett. , 75, 6951, (1999); Hongjie Dai, Jing Kong, Chongwu Zhou, Nathan Franklin, Thomas Tombler, Alan Cassell, Shoushan Fan and Michael for the Physics and Construction of the Chemical Chapline for the Physical Chapline, and the Nanotube for the Physical Chapline, Michael Chapline . Phys. Chem B. 1999, 103, 11246-11255 (1999); Martin, B .; R. , Nanobars, Advanced Materials, 11, p. 1021 (1999); Cui, Y .; Et al., Nanowire Nanosensors for Highly Sensitive and Selective Detection of Biological and Chemical Species, Science, 293, p. 1289 (2001); Martin, B .; R. , Nanobars, Advanced Materials, 11, p. 1021 (1999).
[0017]
In such an experimental device, about 7 × 10⁴Under a helium pressure of about 500 Torr, a DC voltage of about 18 V is applied between two carbon electrodes in the chamber. Plasma is generated between closely spaced electrodes. As the positive electrode is consumed, carbon accumulates and grows on the negative electrode. If the correct electrode spacing is maintained, the deposit will grow into a cylindrical structure with an outer hard shell and an inner soft fibrous core. The gray outer shell is composed of carbon nanotubes and other carbon nanoparticles, which fuse into a hard mass. The soft black inner core contains fibrous free nanotubes and nanoparticles, which are aligned in the direction of the current between the electrodes. Additional methods of making nanotubes are known, such as those described in US Patent Nos. 5,753,088 and 5,482,601.
[0018]
The devices and methods of the present invention describe devices and methods that utilize carbon nanotubes to report events as macroscopic signals. The device and method of the present invention will be described first, followed by a description of the method and some specific examples utilizing the device as a nanoscale reporter.
One embodiment of the device of the present invention includes a first carbon nanotube 10, a second carbon nanotube 12, and a surface 14. First and second carbon nanotubes 10, 12 are operatively connected to and attached to surface 14. The first carbon nanotube 10 further includes a conductive pad 16 operatively attached to one end. Conductive pad 16 is also operatively attached to surface 10. The second carbon nanotube 12 further includes a conductive pad 18 attached to the first end, and a molecule 20 connected to the second end. The molecule 20 connected to the second nanotube 12 is the molecule to be studied.
[0019]
In the present embodiment, the conductive pads 16 and 18 are formed of a platinum lattice, and are attached to the carbon nanotubes 10 and 12. Other conductive pads, such as micron-sized gold islands, can also be used.
The length and size of the constructed nanotubes can be determined by one skilled in the art and will depend on the nature of the molecular interaction event to be detected. By various methods, a secure electrical connection bridged by individual nanotubes can be constructed. For example, a method of achieving a semiconductor single-walled carbon nanotube and then connecting it to two metal electrodes such as the platinum electrode of the present embodiment is described in Nature, 292, (1998). Furthermore, it has been found that carbon nanotubes grow to accumulate into electronic circuits. J. above. Phys. Chem B. 1999, 103 11246-11255 (1999). Nanotube tips can be grown in desired locations on a substrate using the deposition of nanotubes utilizing a substrate patterned with 1-5 micron wide catalyst islands. The position of the nanotube can be confirmed using an atomic force microscope or a scanning tunneling microscope. Using various methods, for example, chemical vapor deposition, single-wall or multi-wall carbon nanotubes growing on a silicon surface, including a silicon oxide substrate, can be considered.
[0020]
Next, the molecule 20 is connected to the free end of the second nanotube 12 using a known technique. Depending on the molecular interaction event of interest, an inorganic or organic molecule 20 can be attached to the composite end of the second nanotube 12. A modification of the chip of one embodiment is achieved by attaching an amine to a pendant carboxyl group. In another embodiment, the covalently modified nanotube tips described above can also be utilized. See Nature, 395, July 1998, supra. In yet another embodiment, the carboxyl groups can be modified to provide additional conjugates. As is evident, the molecule 20 need not necessarily be connected to the end of the second nanotube 12, but may be connected to a position along the entire length of the second nanotube 12.
[0021]
This embodiment can further include a power supply 22. Power supply 22 is operatively attached to conductive pad 16 attached to first nanotube 10 and to conductive pad 18 attached to second nanotube 12. The power supply 22 takes into account the small voltage applied through the first and second carbon nanotubes 10,12. The power supply 22 may also be controlled to precisely monitor and control the amount of power provided to the nanotubes 10,12. Circuits formed with nanotube bridges can also be characterized by measuring electrical resistance or conductivity.
[0022]
This embodiment can further include an ammeter 24. An ammeter 24 is operatively attached to the first and second carbon nanotubes 10, 12 and monitors the current. Ammeters 24 capable of measuring resistance based on the nanoamp and picoamp scales are known to those skilled in the art.
Due to the electronic properties of the nanotubes 10, 12, the shape of the nanotube structure has various electronic properties that can be controlled by the chemical details of the nanotubes used. Depending on the conductive pads 16, 18 and the power supply 22, the intersection between the first nanotube 10 and the second nanotube 12 may be a conductive pad, a rectifying path, a switching path, or even a transistor. In this embodiment, a conductive pad is created whose intersection is monitored by the user. The electronic signature of the nanotube contact is measured and used as a baseline before activation of the enzyme. When a molecular interaction event occurs with the tethered molecule 20, the dynamic molecular properties are transmitted by the nanotubes 10, 12 and amplified into a macroscopic signal. For example, a change in the physical orientation can be measured by monitoring the resistance of the system, since the change in the amount of current flowing therethrough can be measured.
[0023]
When the present invention is used as a molecular event detector, the molecule 20 attached to the second nanotube 12 is exposed to a target sample. The target sample can include a substance that can react with the molecule 20 attached to the end of the second nanotube 12. Due to the potential for reaction, this embodiment contemplates that, if present, the molecule will react in a detectable manner with the tethered molecule. A reaction can be any molecular interaction event that results in any reportable change in the system. In the present embodiment, a change in the electric resistance can be predicted and detected by an ammeter. As will be apparent to those skilled in the art, the teachings of the method of the present invention are applicable to a wide variety of selection systems.
[0024]
As described above, when the molecule 20 tethered to the end of the second nanotube 12 undergoes a molecular interaction event, the event causes a change in the physical relationship between the first nanotube 10 and the second nanotube 12. Let it. In this embodiment, this change is reported by a change in monitored voltage or resistance measured through platinum pads 16, 18 on the ends of the first and second nanotubes 10, 12. This change in resistance is caused by a change in the physical relationship of the nanotubes 10, 12 as a result of a molecular interaction event, ie, changing the length of the current path, thereby changing the resistance detected by the ammeter 24. In other words, since each nanotube 10,12 is connected to a macroscopic circuit through conductive pads 16,18, the measurement of the change in current through the two nanotubes 10,12 will be a measure of the molecular activity taking place. Involved.
[0025]
In alternative embodiments, nanotube properties such as, but not limited to, motion, heat transfer, resistance, compression, expansion, etc. are altered and detected. Changes in the properties of the nanotubes alter the characteristics of the nanotube-nanotube contacts, thereby reporting the enzymatic activity characteristics to the macroscopic world. As will be apparent to those skilled in the art, in alternative embodiments, various properties of the first and second nanotubes 10, 12 can be monitored to detect the occurrence of a molecular interaction event.
[0026]
In an alternative embodiment of the present invention, only one nanotube can be utilized to report a molecular interaction event. One nanotube is formed on the selected surface and the molecule is attached to it. The scanning tunneling microscope is operatively positioned relative to the nanotube to monitor the position or electronic characteristics of the nanotube. When a molecular interaction event occurs on a molecule tethered to the end of the nanotube, the scanning tunneling microscope reports a change in the position of the nanotube and thus the occurrence of an interaction event.
[0027]
In another alternative embodiment of the present invention, the invention is directed to a first nanotube, a second nanotube, a first conductive pad, a second conductive pad attached to the first nanotube, and connected to the second nanotube. A second conductive pad. The nanotubes are operatively attached to each other and the molecule is tethered to the end of the second nanotube. This embodiment may also include a power supply and an ammeter connected between the pads. In this embodiment, current flows through the first pad attached to the first nanotube, traverses to the second nanotube, and then through the second nanotube to the second pad. As will be apparent, in this embodiment, the molecules tethered to the end of the second nanotube will not be affected by the small currents placed on the system. As in the previous embodiment, molecular interaction events caused by the molecule affect the current flowing through the system and are reported by the ammeter.
[0028]
The following embodiments are presented to teach the present invention and are representative of various alternative applications of the present invention. The following embodiments are not intended to limit the invention in any way, as the invention is applicable to chemical detection, material interactions, and other physical or electronic interactions.
[0029]
Example 1: Detection of airborne particles
Airborne molecules affect the behavior and general physical state of the recipient. It is of great interest to be able to detect airborne particles, as even small amounts can cause both animal or human behavior and physiological effects. Such airborne particles may include various toxins, chemicals, or other substances such as pheromones.
[0030]
In one embodiment, a pheromone receptor is attached to the first nanotube. The first nanotube is secured at the other end and traverses a substantially vertical second nanotube connected at both ends to a gold electrode. In addition, it includes a power supply and an ammeter and is operably attached to the system. The steady state electronic signature of this system is verified using a sensitive circuit placed between two gold electrodes. The pheromone is introduced into the environment near the nanotube-bound receptor. When the receptor binds to the pheromone, it undergoes a structural change that affects the properties of the attached first nanotube. Molecular interaction events are reported by detecting changes in the second nanotube circuit. In an alternative embodiment, the device can be made susceptible to transient events by utilizing standard filtering techniques, such as performing a Kellman filter known to those skilled in the art.
[0031]
In alternative embodiments, the present invention can be used to detect other airborne pathogens. For example, Bacillus anthracis is a deadly pathogen that can be transmitted as airborne particles. Other detectable substances include mold spores and viral pathogens.
In these alternative embodiments, the molecule that attaches to the nanotube can include an aptamer. Aptamers are molecules designed to specifically bind to the surface and structure of biological or non-biomolecules. Aptamers that react for a wide variety of interactions and under a variety of conditions can be made by methods known to those skilled in the art. When the aptamer interacts with an airborne pathogen, the aptamer undergoes a structural change, is transmitted as in the above example, and is detected by the nanotube binding circuitry.
[0032]
In another alternative embodiment, the invention can be used for photon detection. In this example, a photoreceptor is attached to the end of a nanotube-based nanosensor. Photon receptors may be based on any of a wide variety of photonic sensors in biology, including photoreceptors in the eye, which are involved in the first step of photosynthesis, and (Also known as blue-green algae). Alternatively, the photoreceptor can be a non-biological material, such as a natural or artificial, photoreactive mineral (eg, silicon). In this embodiment, a photon interaction at a predetermined energy level causes a structural change to be transmitted through the nanoscale sensor into the photodetector. In another alternative embodiment, the present invention can be utilized as a thermal sensor as well. It is clear from these examples that sensors can be designed for a wide variety of interactions based on the core concepts presented. This includes, but is not limited to, particle sensors, chemical sensors, and mineral sensors.
[0033]
It should be noted that in the above example the binding reaction takes place in the air and the detection is based on the detection of mechanically transmitted structural changes. In an alternative embodiment, the detection event can be based on a change in the electronic state of the nanotube that is directly transmitted by the binding interaction. For example, as described above, the sensor is configured such that the nanotube bridges two gold electrodes. Connected to the center of the nanotube is a detection entity such as the pheromone receptor described above. This tether can be achieved at defective areas known to occur within the nanotube. The electronic state of the sensor is established by measuring the circuit. Upon reaction with the pheromone ligand, this electronic state changes due to the addition of new components to the system, blending its electronic characteristics with the electronic state of existing systems. This state change is monitored by a change in the detection circuit mechanism.
[0034]
So far, all embodiments have been described using systems operating in air or vacuum at some level of humidity. However, similar reactions can be performed in solution as long as the sensor is protected and distinguished from the liquid environment. It is well known that scanning tunneling microscopes can scan in solution by covering most of the probe with an insulating material, leaving only the top end open to the surrounding liquid environment. Using this same method, nanoscale sensor systems with similar properties can be made. For example, a nanoscale sensor can be coated with an insulating material by ion beam sputtering the insulating material entirely except for the sensing portion of the system. In this case, the system can be operated in solution and detect biomolecular events in a liquid system. The following are particularly useful examples.
[0035]
Example 2: Detection of enzyme activity
A first nanotube is formed as described above and attached to a biomolecule. The first carbon nanotube is acid-treated at one end to form a dangling-COOH group at the end. -The COOH group is attached to the enzyme by condensation chemistry. In one embodiment of the method of the present invention, a carbodiimide reagent is used to catalyze the condensation of a free carboxyl group with a primary amine on an enzyme, thereby liberating a water molecule and providing a covalent chain between the enzyme and the nanotube. To form
The enzyme is then activated by the addition of a substrate and the necessary cofactors. As the enzyme performs its catalytic function, the properties of the first and second nanotubes change depending on the catalytic function of the enzyme.
[0036]
In one embodiment, upon a molecular interaction event, movement of the linked enzyme results in a change in resistance of the circuit formed by the nanotubes. In one embodiment, when a molecular interaction event changes the relative position of the first and second nanotubes, the length of the circuit path changes. The change in resistance is measured by electrons drawn through the second nanotube as the second nanotube slides, moves, or reacts in some way with the first nanotube. In another alternative embodiment, other physical characteristics and relationships of the two nanotubes can be detected when a molecular interaction event occurs.
[0037]
In an alternative embodiment, structures such as electronic gates can be incorporated in the construction of crossed nanotubes that give rise to transistor switches.
In this example, the primary information derived is whether the enzyme is active and undergoes a molecular interaction event. This information is very useful, for example, if the enzyme is only active in the presence or absence of certain reagents. One example is in the detection of metal ions that catalyze a chemical reaction. Another example is the detection of a particular type of enzyme substrate, the presence or absence of which is diagnostic of a particular condition. The present invention is useful for both of these characterizations.
[0038]
In another alternative embodiment, when the enzyme is a DNA polymerase, a change in molecular shape or other characteristic detects the presence of a particular nucleic acid. Nucleic acids are detected by enzymes that become active only when the complementary primer DNA molecule binds to the target DNA molecule, thereby forming a suitable substrate on which the polymerase acts.
In yet another embodiment, the binding of one protein to another is detected. When an antibody is made on a nanotube sensor, the binding of the antibody to the antigen causes a change in the antibody structure. This structural change is translated into an electronic signal in a manner similar to that described above.
[0039]
One advantage of this embodiment of the present invention is that the nanotube sensor is the same size as the enzyme. The fact that the nanotube and the enzyme are the same size means that the activity of the enzyme has a profound effect on the properties of the nanotube. This is in contrast, for example, to the fact that conventional AFM probes have thousands of times the mass of a single enzyme molecule attached to its apex. The difference in size results in low sensitivity.
[0040]
Example 3: Detection of DNA sequencing
In this embodiment, a nanotube junction is created in which a DNA polymerase enzyme is connected to one end of a second nanotube. In this embodiment, a DNA substrate and a complementary primer are added to the system. As soon as the substrate and primer bind together and bind to the tethered DNA polymerase, the enzyme is ready to work. The enzymatic activity is initiated by the addition of a nucleotide triphosphate precursor containing the appropriate buffer and catalyst. As the enzyme adds nucleotides to the primer molecule, the enzyme produces a signal that affects the current between the first and second nanotubes within the nanotube junction, which is a result of the energy consumed by the enzyme, and Detected by the meter. The generated signal is a mechanical, thermal, or some other form of energy. In the present embodiment, these signals correspond to the sequence of DNA synthesized by adding nucleotides to the primer.
[0041]
For a polymerase to be active, it requires a DNA substrate that contains both the target DNA and the primer strand. The primer strand provides a 3'-OH group to which the polymerase can start adding nucleotides while simultaneously copying the target strand. When a DNA polymerase acts to incorporate a complementary molecule into the growing strand of DNA, the stereochemistry and energy requirements for each nucleotide type are slightly different. This difference constitutes a separate indicator of nucleotide A, C, G, or T (U for RNA) incorporation. This information is transmitted by the nanosensors described herein and provides an immediate knowledge of the DNA sequence of the molecule synthesized by the polymerase component of the nanosensor. This embodiment is applicable to both DNA and RNA molecules. Therefore, according to the present embodiment, the user can analyze the generated signal and directly infer the generated DNA or RNA sequence. The uses and advantages of the invention are clear.
[0042]
In an alternative embodiment, the method can be performed on a large set of nanoscale sensors formed on the same surface. Since each biosensor has a space dimension of about 2 μ × 2 μ, a solid substrate or 1 cm²There can be millions on a “chip”. Using such a method and apparatus, the sequence of a DNA fragment can be determined simultaneously. Furthermore, the reaction rate of DNA polymerases is as fast as 20 to 40 nucleotides per second, which translates into extremely fast and efficient sequencing rates.
[0043]
The information and examples described herein are for illustrative purposes and are not meant to exclude any derivations or alternatives within the conceptual content of the invention. It is contemplated that various departures from this embodiment may be made without departing from the scope of the invention. Therefore, it is intended that the scope of the invention be determined not by the preceding description of this embodiment, but by the claims.
All publications cited in this application are incorporated by reference in their entirety, regardless of purpose.
[Brief description of the drawings]
FIG.
1 shows a schematic diagram of a nanotube circuit of one embodiment of the present invention.

Claims (21)

A sensor,
A first nanoscale object formed on a surface;
A second nanoscale object formed in operative relationship with the first nanoscale object on the surface;
A monitoring device operably attached to the first nanoscale object and the second nanotube object;
At least one molecule tethered to a first end of the second nanoscale object;
A sensor characterized in that when a molecular interaction event involving the tethered molecule occurs, the monitoring device detects the molecular interaction event. Furthermore,
A first conductive pad attached to a first end of the first nanoscale object;
A second conductive pad attached to a second end of the second nanoscale object;
The device of claim 1, comprising: Further, by including a power supply operably attached to the first and second conductive pads, the power supply conducts current through the first nanoscale object and the second nanoscale object and diverts the current to the The device of claim 1 wherein the monitoring device detects. The monitoring device is an ammeter, wherein the ammeter measures a resistance of a current passing through the first nanoscale object and the second nanoscale object, and detects a change in the resistance. The device of claim 1. The device of claim 1, wherein the surface is silicon. The apparatus of claim 5, wherein said surface further comprises a layer of silicon dioxide. The device of claim 1, wherein the molecule tethered to the end of the second nanoscale object is a biomolecule. The device of claim 7, wherein the biomolecule is an enzyme. 9. The device of claim 8, wherein said enzyme is a DNA polymerase. The device of claim 1, wherein the molecule tethered to the end of the second nanoscale object is an inorganic molecule. A method for detecting a molecular interaction event, comprising the following steps:
Operably coupling a first nanotube to a second nanotube, wherein the first nanotube is operably coupled to a first conductive pad at a first end and operable to a second conductive pad at a second end. Coupled and the second nanotube is operably coupled at a first end;
Providing a current flowing through the first nanotube, and monitoring the current flowing through the first nanotube with an ammeter, wherein when the biomolecule undergoes a molecular interaction event, Affecting the conductivity of the first nanotube and detecting a change in the conductivity with the ammeter;
A method that includes 12. The method of claim 11, wherein said molecule is a biomolecule. 13. The method of claim 12, wherein operably coupling the biomolecule to the second nanotube further comprises performing a condensation reaction between a carboxyl group and a primary amine. A method for detecting a molecular interaction event, comprising the following steps:
Connecting the molecule to the first end of the nanoscale object,
Scanning the nanoscale object with a scanning tunneling microscope, and detecting movement of the nanoscale object as the molecule undergoes a molecular interaction event;
A method that includes 15. The method of claim 14, wherein the movement of the nanoscale object is detected through a change in the position of the nanoscale object with respect to the scanning tunneling microscope probe. 15. The method of claim 14, wherein said molecule is a biomolecule. 15. The method of claim 14, wherein said molecule is an enzyme. An apparatus for detecting a molecular interaction event, comprising:
A first nanotube operably attached to a surface;
A second nanotube operably attached to the surface and operably connected to the first nanotube;
A molecule connected to a first end of the second nanotube;
A device wherein the molecule involved in a molecular interaction event causes a measurable change in the physical properties of the first and second nanotubes. Furthermore,
A monitoring device operably positioned with respect to the first and second nanotubes, wherein the monitoring device detects a change in a physical property of the first and second nanotubes when the molecular interaction event occurs. 20. The apparatus of claim 18, wherein: 19. The apparatus of claim 18, wherein said monitoring device is an ammeter. 20. The apparatus of claim 19, wherein said monitoring device is a scanning tunneling microscope probe.