KR20040075620A - Preparation of novel carbon nanotubes-nucleic acids conjugates - Google Patents

Abstract

PURPOSE: Provided is a method for producing a carbon nanotube-nucleic acid conjugate which provides a functionalized and solubilized carbon nanotube in high yield, wherein the carbon nanotube is uniformly cut without forming a bundle, and is useful for developing a biosensor and a material having improved physical property. CONSTITUTION: In the water-soluble carbon nanotube-nucleic acid conjugate, the nucleic acid surrounds a part of surface or whole surface of carbon nanotube by non-covalent bond. The nucleic acid is DNA, RNA, DNA-RNA hybrid, or mixture thereof. To an end of the nucleic acid or a part thereof, an adduct not affecting a spiral, basic structure of the nucleic acid is connected. The conjugate is produced by the method comprising mixing at least one of DNA, RNA, DNA-RNA hybrid or mixture thereof with carbon nanotube to obtain a mixture and then mechanically crushing the obtained mixture.

Description

Preparation of new carbon nanotube-nucleic acid conjugates {PREPARATION OF NOVEL CARBON NANOTUBES-NUCLEIC ACIDS CONJUGATES}

The present invention relates to a method for obtaining highly efficient, functionalized and solubilized carbon nanotubes that do not form a bundle and are uniformly cut.

Carbon nanotubes refer to a structure in which a sheet of hexagonal atomic structure in which one carbon atom is surrounded by three carbon atoms and bonded to each other is rolled up to form a cylinder. In general, carbon nanotubes are divided into single-walled nanotubes having a diameter of several nanometers and multi-walled nanotubes having a diameter of several tens of nanometers formed by overlapping several layers in concentric circles. Carbon nanotubes may be electrically conductive like metals or function as semiconductors, depending on the shape of the curled shape and the diameter of the tube shape.

Since 1991, Sumio Iijima (Helical Microtubules of Graphitic Carbon, Nature 354 , 1991, pp 56-58) reports for the first time that the shape of a multilayer tube can be obtained by evaporating carbon by arc discharge. Carbon nanotubes have attracted attention in a variety of applications because of their inherent properties. Due to the unique properties of nanoscale fine size, good electrical conductivity, high mechanical strength, low density and excellent surface selectivity, carbon nanotubes can be used for high resolution displays, nanoprinting, nanoelectrodes, drug delivery, sensors and field emission sources. It has a high applicability as a new material material constituting a field emission source. In particular, it is expected to be applied as a material for display elements, energy gas storage systems, supercapacitors, thin film batteries, electromagnetic wave shielding agents and the like by exhibiting excellent characteristics in electron transfer reaction, energy generation and storage.

However, despite such various applicability, the practical use of carbon nanotubes is still not achieved. It is not only difficult to purely separate, manipulate and uniformly cut carbon nanotubes from carbon nanotube bundles formed by Van der Waals interaction, but also to make them nonpolar in order to take advantage of the unique properties of carbon nanotubes. This is because functionalization is needed to chemically activate the nanotubes.

In order to solve this problem, various methods have been tried to obtain carbon nanotubes that are free of bundles and functionalized and solubilized. The most common way to get rid of the bundle form is to ultrasonically treat the bundle of carbon nanotubes for a long time. In addition, methods for covalently linking inactivated carbon nanotubes to selected molecules have been developed for the functionalization and solubilization of carbon nanotubes. However, functionalization by commonly used sonication and strong acid treatment is known to cause serious damage to the surface of carbon nanotubes, and in most cases no water soluble product is obtained. Recently, functionalization methods for obtaining water-soluble carbon nanotubes by covalent bonding with glucosamine have been reported (Pompeo F. et al ., Nano letter 2 , 2002, 369-373), but have very low solubility, It turns out to be very dependent.

Meanwhile, a technique for fixing biomolecules such as platinum oligonucleotides and metal thionines on the surface of carbon nanotubes for the development of biosensors has been reported, suggesting new applications of carbon nanotubes. However, they only fixed platinum-plated oligonucleotides to the carbon nanotubes, and the method of non-covalently enclosing the carbon nanotubes with nucleic acid molecules and thereby causing changes in the properties of the carbon nanotubes such as increased water solubility. I do not expect it at all.

Therefore, there is an urgent need for research to obtain functionalized carbon nanotubes having high water solubility while minimizing surface damage of carbon nanotubes.

It is an object of the present invention to provide a carbon nanotube containing material which has high water solubility, is cut uniformly and does not form a bundle.

Another object of the present invention is to provide a carbon nanotube-containing material as a material suitable for biosensor fabrication and having improved material properties.

It is a further object of the present invention to provide a process for the preparation and separation of carbon nanotubes having the excellent material properties mentioned above.

Figure 1 is a schematic of the manufacturing process of the carbon nanotube (CNT) -DNA conjugate,

2 is a scanning electron micrograph (SEM) of a water soluble carbon nanotube-DNA conjugate,

3 is a transmission electron microscopy (TEM) picture of a water soluble carbon nanotube-DNA conjugate (bars represent 50 nm),

4 is a UV-Vis spectrum of DNA and carbon nanotube-DNA conjugates,

5 is a SEM photograph of a water-soluble carbon nanotube-DNA conjugate after 60 days,

FIG. 6 is a SEM photograph (an enlarged photo of FIG. 5) of a water soluble carbon nanotube-DNA conjugate after 60 days. FIG.

According to the above object, the present invention provides a water-soluble carbon nanotube-nucleic acid conjugate.

The present invention also provides a method of preparing the carbon nanotube-nucleic acid conjugate and a method of separating the carbon nanotube by forming the carbon nanotube-nucleic acid conjugate.

Hereinafter, the present invention will be described in detail.

The carbon nanotube-nucleic acid conjugate of the present invention has a form in which nucleic acids surround all or part of the surface of carbon nanotubes by non-covalent bonds, thereby enabling chemical functionalization. Such non-covalent functionalization is essential for maintaining the sp ² hybrid structure of carbon nanotubes to maintain electrical properties suitable for a variety of applications.

In the above, the nucleic acid may be a DNA, RNA, DNA-RNA hybrid or a mixture thereof, it is double stranded or single stranded. Adducts which do not affect the helical basic structure of the nucleic acid may be linked to the ends or portions thereof.

The carbon nanotubes may be single-walled nanotubes or multi-walled nanotubes substantially free of amorphous carbon, with particular preference being given to single-walled nanotubes.

The weight ratio of the nucleic acid to the carbon nanotubes is preferably 1: 0.2 to 1:20, and particularly, the amount of the nucleic acid is more than the amount of the carbon nanotubes in order to completely surround the surface of the carbon nanotubes with the nucleic acid. The thickness of the nucleic acid region surrounding the surface of the carbon nanotubes depends on the concentration of the nucleic acid applied.

In another aspect, the present invention provides a method for producing a carbon nanotube-nucleic acid conjugate, comprising the step of mixing and milling carbon nanotubes and nucleic acids. The mechanically mixed grinding step may be performed according to a known method generally used in the art, for example, by a method of mixing and grinding carbon nanotubes and nucleic acids simultaneously or sequentially by a ball mill device. have.

The production of carbon nanotube-nucleic acid conjugates provided by the present invention is characterized in that it can be made in the solid state. The synthesis process of the carbon nanotube-nucleic acid conjugate is shown in FIG. 1. Through the above process, the carbon nanotubes are mechanically cut uniformly, and at the same time, the nucleic acids can be non-covalently wrapped around the carbon nanotubes by a nonspecific reaction between the carbon nanotubes and the nucleic acids.

In the above, the nucleic acid may be double stranded or single stranded DNA, RNA, DNA-RNA hybrid or a mixture thereof, and an adduct that does not affect the helical basic structure of the nucleic acid may be bound to the terminal or part of the nucleic acid. have. The carbon nanotubes are preferably single-walled carbon nanotubes that are substantially free of amorphous carbon.

The weight ratio of the nucleic acid to the carbon nanotubes is preferably 1: 0.2 to 1:20, and in particular, the amount of the nucleic acid is more than the amount of the carbon nanotubes in order to completely surround the surface of the carbon nanotubes with the nucleic acid. The thickness of the nucleic acid region surrounding the surface of the carbon nanotubes depends on the concentration of the nucleic acid applied.

The carbon nanotube-nucleic acid conjugate produced by the method of the present invention has a very high solubility in water, and the carbon nanotubes do not form a bundle and are chemically functionalized. In addition, it is possible to obtain carbon nanotubes that are relatively uniformly cut by using a mechanical mixed grinding method. The water solubility of the carbon nanotube-nucleic acid conjugate lasts more than 2 months stably.

The present invention also comprises the steps of mechanically mixing and grinding the addition of nucleic acids to a composition comprising carbon nanotubes; Dissolving the mixed and ground product in water; And separating the aqueous layer in which the carbon nanotube-nucleic acid conjugate is dissolved and the solid layer insoluble in water.

In the above, the nucleic acid is a single- or double-stranded DNA, RNA, DNA-RNA hybrid or a mixture thereof, carbon nanotubes may be single-walled nanotubes or multi-walled nanotubes, but single-walled nanoparticles do not form a bundle It is preferably a tube.

Separation of the aqueous layer and the solid layer may be a known method commonly used in the art, for example, other carbon nanotube-nucleic acid conjugates dissolved in water by centrifugation, precipitation, filtration, etc. are not dissolved in water. It can be separated from the components.

If necessary, the nucleic acid may be removed from the separated carbon nanotube-nucleic acid conjugate to obtain the carbon nanotube in a pure state. In this case, the carbon nanotube-nucleic acid conjugate may be treated with a polar or nonpolar solvent to separate only the carbon nanotubes. For example, a chlorinated organic solvent such as methylene chloride may be used for this purpose, but is not limited thereto. Any solvent capable of changing the noncovalent binding force between the nucleic acid and the carbon nanotubes can be used.

The separated carbon nanotube-nucleic acid conjugates or solutions or suspensions comprising the same have high applicability in various fields because they are chemically functionalized and do not form bundles while maintaining the electrical, thermal, and mechanical properties of the carbon nanotubes.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Example 1 Preparation of Carbon Nanotube-DNA Bonds

Carbon nanotubes to be used to prepare carbon nanotube-DNA conjugates were prepared according to the method of Sohn JI et al ., Appl. Phys. Let. , 78, 901-903, 2001. 5 mg of the carbon nanotubes were ground with a ball mill (length: 4 cm, diameter: 1.7 cm), and then 25 mg of DNA (Sigma, Catalog No. D6898) was added and ground for 1 hour (20 Hz, 220 V). To prepare a carbon nanotube-DNA conjugate.

The black powdery carbon nanotube-DNA conjugate obtained above was observed with a scanning electron microscope (SEM). SEM photographs of the carbon nanotube-DNA conjugate show that the DNA completely covers the surface of the carbon nanotubes uniformly cut to about 1-2 μm (FIG. 2). Since the amount of DNA was applied in excess of the amount of carbon nanotubes, the carbon nanotubes can be completely wrapped with nucleic acid. The diameter of the carbon nanotubes completely wrapped with nucleic acid increased to 10-20 μm, indicating that the surface of the carbon nanotubes was completely wrapped by DNA.

On the other hand, transmission electron microscope (TEM) pictures show that the surface of the carbon nanotubes exhibits an irregular shape due to the DNA coating (FIG. 3).

Example 2 Solubility of Carbon Nanotube-DNA Conjugates

The carbon nanotube-DNA conjugate powder obtained in Example 1 was added to deionized water to confirm water solubility. Carbon nanotubes obtained through the same ball mill treatment in the absence of DNA were used as a control. The control group was not dissolved in water, whereas the carbon nanotube-DNA conjugate was completely dissolved in water (5 mg / ml).

<Experiment 1> Formation pattern of carbon nanotube-DNA conjugate according to the change of DNA concentration

In order to confirm the influence of the DNA concentration on the formation of the carbon nanotube-DNA conjugate, the aqueous solution of the carbon nanotube-DNA conjugate obtained in Example 2 was diluted. 4 shows UV spectra of aqueous solutions of carbon nanotube-DNA conjugates at different concentrations, where a) is DNA and b), c) and d) are 0.07 mg / ml, 0.22 mg / ml and 0.25 mg, respectively. UV-Vis spectrum of carbon nanotube-DNA conjugate aqueous solution at / ml concentration is shown. As the solution was diluted, the DNA thickness was reduced, and the thickness of the DNA surrounding the carbon nanotubes was highly dependent on the concentration of the DNA. The UV-Vis spectrum showed absorption at 903 nm close to the infrared region, due to the semiconducting bands of the metal or carbon nanotubes.

Experimental Example 2 Stability of Carbon Nanotube-DNA Conjugates

The carbon nanotube-DNA conjugate aqueous solution was stored in a 4 ° C. refrigerator. As a result, no precipitation was observed even after 60 days had elapsed. This shows that the solubility of carbon nanotube-DNA conjugates lasts more than two months. SEM photographs after 60 days (FIGS. 5 and 6) show that carbon nanotubes, due to the interaction between the DNA molecules surrounding the carbon nanotubes and van der Waals interactions, are unlike the initial bundles formed only with carbon nanotubes. The bundles between tube-DNA conjugates appear to be in unique forms.

The carbon nanotube-nucleic acid conjugates provided by the present invention exhibit high water solubility and are evenly cut and bundle-free. In addition, because it is based on non-covalent bonds, it can be chemically functionalized while minimizing surface damage of carbon nanotubes. Carbon nanotubes separated by a simple mechanical method of mixing and grinding with nucleic acids have ease and economy of separation and manipulation, and can be applied to various fields, including the development of biosensors and the development of materials with improved physical properties.

Claims (12)

A water soluble carbon nanotube-nucleic acid conjugate wherein the nucleic acid surrounds all or part of the carbon nanotube surface by non-covalent bonds. The method of claim 1, Carbon nanotube-nucleic acid conjugate, characterized in that the nucleic acid is DNA, RNA, DNA-RNA hybrid or a mixture thereof. The method of claim 2, A carbon nanotube-nucleic acid conjugate, characterized in that an adduct is attached to a terminal or part of the nucleic acid that does not affect the helical basic structure of the nucleic acid. The method of claim 2, A carbon nanotube-nucleic acid conjugate wherein the nucleic acid is double stranded or single stranded. The method of claim 1, Carbon nanotube-nucleic acid conjugates wherein the carbon nanotubes are single-walled or multi-walled nanotubes that are substantially free of amorphous carbon. The method of claim 1, A carbon nanotube-nucleic acid conjugate, characterized in that the weight ratio of nucleic acid to carbon nanotube is 1: 0.2 to 1:20. A method of making a water soluble carbon nanotube-nucleic acid conjugate, comprising mixing and grinding mechanically mixed one or more nucleic acids selected from DNA, RNA, DNA-RNA hybrids or mixtures thereof with carbon nanotubes. The method of claim 7, wherein A method of making a water soluble carbon nanotube-nucleic acid conjugate, wherein the carbon nanotubes are single-walled or multi-walled carbon nanotubes that are substantially free of amorphous carbon. The method of claim 7, wherein Method for producing a water-soluble carbon nanotube-nucleic acid conjugate, characterized in that the weight ratio of the nucleic acid to the carbon nanotube is 1: 0.2 to 1:20. The method of claim 7, wherein Method for producing a water-soluble carbon nanotube-nucleic acid conjugate, characterized in that the carbon nanotubes do not form a bundle. Mechanically mixing and milling by adding one or more nucleic acids selected from DNA, RNA, DNA-RNA hybrids or mixtures thereof to a composition comprising carbon nanotubes; Dissolving the mixed and ground product in water; And separating the water layer in which the carbon nanotube-nucleic acid conjugate is dissolved and the solid layer insoluble in water. The method of claim 11, A method of separating carbon nanotubes, further comprising the step of removing the nucleic acid from the carbon nanotube-nucleic acid conjugate contained in the aqueous layer.