KR100702873B1 - Carbon nanotube-chitosan composites and method of manufacturing the same - Google Patents

Abstract

   The present invention relates to a carbon nanotube-chitosan composite and a method for producing the same, to prepare a carbon nanotube-chitosan composite having excellent dispersibility in an organic solvent through the following steps.

-Below-

(Iii) mixing nitric acid and carbon nanotubes, and then refluxing them to introduce carboxyl groups into the carbon nanotubes;

(Ii) The carbon nanotubes to which the carboxyl group is introduced are washed and dried with filtration and distilled water until the pH becomes 7, and SOCl ₂ is mixed therein and then refluxed to introduce the carboxyl groups introduced into the carbon nanotubes. Replacing with a COCl group,

(Iii) The carbon nanotubes into which the -COCl group was introduced were filtered, washed with anhydrous CH ₂ Cl ₂ , and dried, and then mixed with acetic acid in which chitosan was dissolved. Manufacturing process and

(Iii) washing the prepared carbon nanotube-chitosan complex with acetic acid to remove unreacted chitosan, and then washing with distilled water until the pH reaches 7 after filtration.

Complex, chitosan, carbon nanotube, organic solvent dispersibility, gene, drug, carrier

Description

Carbon nanotube-chitosan composites and method of manufacturing the same

1 is a photograph showing a state where the carbon nanotube-chitosan complex is dispersed in a dimethylformamide solvent

2 is a photograph showing a state in which carbon nanotubes are dispersed in a dimethylformamide solvent

3 shows Raman spectra

       (a: carbon nanotube, b: carbon nanotube-chitosan complex, c: chitosan)

4 is FT-IR spectra

      (b: carbon nanotube-chitosan complex, d: carbon nanotube in KBr petri)

5 is the thermogravimetric curve

       (a: carbon nanotube, b: carbon nanotube-chitosan complex, c: chitosan)

6 is a transmission electron microscope photograph of carbon nanotubes

7 is a transmission electron micrograph of the carbon nanotube-chitosan composite

8 is a transmission electron microscope photograph of an enlarged edge of a hollow portion of a carbon nanotube-chitosan composite;

9 is an enlarged transmission electron micrograph of a stem portion of a carbon nanotube-chitosan composite;

The present invention relates to a carbon nanotube-chitosan composite and a method for preparing the same, and more particularly, to a carbon nanotube-chitosan composite having excellent dispersibility in an organic solvent by covalently bonding chitosan to a carbon nanotube and a method for producing the same. will be.

Carbon nanotubes are highly regarded as a very useful material for miniaturization of implantable bioelectronic or optical devices including probes and sensors because of their excellent aspect ratio, mechanical strength, electrical conductivity and thermal conductivity.

In order for carbon nanotubes to be used in gene carriers, drug carriers, implantable bioelectronic devices, and optical devices, they have to have biocompatibility and excellent dispersibility in organic solvents.

As a conventional technique for imparting biocompatibility and solvent dispersibility to carbon nanotubes, a method of modifying surface properties by introducing reactive groups such as -OH group, -COOH group, amine group, and amide group to carbon nanotubes has been known. .

As a specific conventional technique, a method of modifying a surface by emulsion polymerization of n-butylacrylate and methylmethacrylate on a surface of a carbon nanotube [Chem. Mater. 2003, 15, 3879, and a method for producing macromolecules branched by self-condensation polymerization on the surface of carbon nanotubes [Macromolecules 2005. 38, 2606].

However, the conventional methods have a problem that biocompatibility and dispersibility to a solvent are not greatly improved because the surface of the carbon nanotubes is modified with synthetic polymers, not biodegradable natural polymers.

The present invention aims to provide a carbon nanotube-chitosan complex which is useful as a gene carrier by greatly improving biocompatibility and solvent dispersibility by solving such problems of the prior art.

To this end, the present invention provides a method for producing the carbon nanotube-chitosan by giving an acid to the carbon nanotubes using an amide bond of the amine compound, and then covalently bonded to chitosan.

In order to achieve these problems, the present invention manufactures a carbon nanotube-chitosan composite in which chitosan is covalently bonded to carbon nanotubes through the following processes.

-Below-

(Iii) mixing nitric acid and carbon nanotubes, and then refluxing them to introduce carboxyl groups into the carbon nanotubes;

(Ii) The carbon nanotubes to which the carboxyl group is introduced are washed and dried with filtration and distilled water until the pH becomes 7, and SOCl ₂ is mixed therein and then refluxed to introduce the carboxyl groups introduced into the carbon nanotubes. Replacing with a COCl group,

(Iii) The carbon nanotubes into which the -COCl group was introduced were filtered, washed with anhydrous CH ₂ Cl ₂ , and dried, and then mixed with acetic acid in which chitosan was dissolved. Manufacturing process and

(Iii) washing the prepared carbon nanotube-chitosan complex with acetic acid to remove unreacted chitosan, and then washing with distilled water until the pH reaches 7 after filtration.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, in the present invention, nitric acid and carbon nanotubes are mixed and then refluxed to introduce carboxyl groups into the carbon nanotubes.

At this time, it is more preferable to disperse them for 10 to 40 minutes with ultrasonic waves before mixing them with reflux after mixing nitric acid and carbon nanotubes.

As nitric acid, nitric acid having a concentration of 50 to 70% is used, and 1 g of carbon nanotubes are preferably mixed with 50 to 70 ml of nitric acid.

Reflex is also preferably carried out at 100-120 ° C. for 16-20 hours.

Next, the carbon nanotubes to which the carboxyl group is introduced are filtered and washed with distilled water until the pH reaches 7, and then, SOCl ₂ is mixed thereto, and these are refluxed to introduce the carboxyl groups introduced into the carbon nanotubes. Substituted by -COCl group.

At this time, it is preferable to filter the carbon nanotubes into which the carboxyl group is introduced under vacuum with a polycarbonate membrane having micropores having an average diameter of 0.1 to 0.3 µm.

In addition, after washing the carbon nanotubes to which the carboxyl group is introduced, it is preferable to dry them under vacuum at 40 to 60 ° C. for 20 to 60 minutes.

In addition, reflux after SOCl ₂ mixing is preferably carried out at 60 to 80 ° C. for 15 to 20 hours.

Next, the carbon nanotubes into which the -COCl group was introduced were filtered, washed with anhydrous CH ₂ Cl ₂ , and dried, and then mixed with acetic acid in which chitosan was dissolved therein, followed by refluxing them to form a carbon nanotube-chitosan composite. To prepare.

At this time, it is preferable to reflux the carbon nanotubes in which -COCl group is introduced and acetic acid in which chitosan is dissolved at 90 to 110 ° C for 18 to 28 hours.

In addition, the concentration of nitric acid used to dissolve chitosan is preferably 1 to 5%, and the chitosan content in acetic acid in which chitosan is dissolved is preferably 0.5 to 3% by weight.

Next, the prepared carbon nanotube-chitosan composite is washed with acetic acid to remove unreacted chitosan, and then washed with distilled water until pH reaches 7 to prepare a carbon nanotube-chitosan composite as a final product.

At this time, the concentration of nitric acid used for washing is preferably 1 to 5%.

Chitosan is a polysaccharide with a structure similar to cellulose. The two are made from monosaccharides linked in a linear β (1> 4) structure. However, another important difference between cellulose and chitosan is that it consists of 2-amino-deoxy-beta-D-glucose [2-amino-2-deoxy-β-D-glucose] in which chitosan is linked by glycosidic bonds. . This primary amine group confers special properties that make chitosan very useful in the pharmaceutical field. Compared to many other natural polymers, chitosan has a positive charge and mucoadhesive

Therefore, the carbon nanotube-chitosan complex of the present invention in which carbon nanotubes are modified with chitosan has excellent biocompatibility and solvent dispersibility and can effectively deliver a desired gene or drug to a target cell.

After the carbon nanotube-chitosan composite of the present invention was added to a dimethylformamide solvent, dispersed for 5 minutes by ultrasonic wave, and left for one day, the photograph of the dispersed state is shown in FIG. 1. 1 shows that the carbon nanotube-chitosan complex is evenly dispersed in the solvent without aggregation.

Meanwhile, the conventional carbon nanotubes not modified with chitosan are added to dimethylformamide solvent and dispersed by ultrasonic wave for 5 minutes, and then left for one day.

2 shows that the carbon nanotubes are uniformly dispersed in the aggregated state.

The carbon nanotube-chitosan composite of the present invention exhibits excellent dispersibility not only in dimethylformamide but also in various solvents such as formic acid, alcohol solvents and acetic acid.

In order to determine the presence of carbon nanotubes in the carbon nanotube-chitosan complex, Raman spectroscopy was used. 3 is a Raman spectra of carbon nanotubes (a) carbon nanotube-chitosan composites (b) and chitosan (c). A characteristic 1600 cm ⁻¹ tangential G band corresponding to the E _{2 g} mode of graphite was observed. This band is associated with the oscillation of sp ² hybrid carbon in a two-dimensional hexagonal lattice. Carbon nanotubes show the same vibration in the concentric center of the hexagonal carbon lattice. The central disorder mode band at 1282 cm ^-1 is associated with the vibration of carbon atoms with bands suspended from the planar ends of disordered graphite or glassy carbon. From the above observations, it can be seen that the carbon atoms in the carbon nanotubes are arranged in a hexagonal framework like graphite. In addition to this characteristic mode, Raman intensity increases because the Raman vibration mode of pure chitosan is within this range compared to carbon nanotubes showing the presence of chitosan in the composite. However, this result does not mean that chitosan forms covalent grafts on carbon nanotubes.

FT-IR spectra of Figure 4 was measured to determine the characteristic binding of the carbon nanotube-chitosan complex. The band at 1700 cm ^-1 corresponds to the stretching vibration of the C = O group with the amide functional group, and the wide band at 1582 cm ^-1 represents the combination of the stretching vibration of the CN of the amide group and the bending strength of the NH band. Indicates. The wide band of 3430 cm ⁻¹ is the characteristic OH stretching of polysaccharides. The results of FT-IR demonstrate the presence of graft-bound chitosan on carbon nanotubes.

The content of chitosan in the carbon nanotubes was measured by thermogravimetric analysis.

5 is a thermogravimetric curve of carbon nanotube (a), carbon nanotube-chitosan composite (b) and chitosan (c).

Pure chitosan, carbon nanotubes-chitosan, and carbon nanotubes were heated to 20 ° C./min in a nitrogen atmosphere. Carbon nanotubes were decomposed at about 500 ° C. in the air and at 800 ° C. in a nitrogen atmosphere. Chitosan is the most degraded at 270 ~ 400 ℃. However, carbon nanotube-chitosan has a weight loss of 10 parts by weight at 50 to 240 ° C due to the dehydration of moisture attached to the sample. The weight loss occurs 12 parts by weight at 240 to 600 ° C., and the weight loss occurs at 46 parts by weight at 600 to 1000 ° C. Finally, it can be seen that 32% of pure carbon content remains. The major decomposition of chitosan, which occurs at 240 to 400 ° C, shifts to 600 ° C when combined with carbon nanotube surfaces. This result clearly shows the stability of chitosan on the walls of the carbon nanotubes. On the other hand, the decomposition temperature of the carbon nanotubes in the nitrogen atmosphere is lowered to 600 ℃. The transfer of carbon nanotubes to lower temperatures is similar to previous studies that carbon nanotubes encapsulated by poly (methyl methacrylate) are decomposed at 600 ° C. When the amount of chitosan combined with carbon nanotubes in the range of 240 ~ 600 ℃ it can be easily seen that the ratio of chitosan in the carbon nanotubes is 12%.

6 is a transmission electron microscope photograph of carbon nanotubes, FIG. 7 is a transmission electron microscope photograph of a carbon nanotube-chitosan composite, and FIG. 8 is a transmission electron microscope photograph of a hollow edge of the carbon nanotube-chitosan composite. 9 is a transmission electron microscope photograph of an enlarged image of a stem of a carbon nanotube-chitosan composite.

Nanotubes are straight structures, like bamboo, several nanometers in length. The transmission electron micrographs of FIGS. 6 to 7 show diamond patterns of carbon nanotubes. On the other hand, when comparing the diameter of the carbon nanotube-chitosan composite of FIG. 7 and the unmodified carbon nanotube of FIG. 6, the carbon nanotube-chitosan composite of FIG. 7 is thicker and denser than the carbon nanotube of FIG. 6. Able to know. This increase in thickness is more evident that chitosan is grafted onto the carbon nanotubes. In addition, in the carbon nanotube-chitosan composite of FIG. 8, the open end can be seen, the inner diameter of the tube is 4 nm, the outer wall of the tube is 6 nm, and the total diameter of the tube end is 16 nm.

In addition, the end of the tube was narrower in width compared to the stem of FIG. 9 and was about 25 nm. This probably means that the tube shrinks due to more absorption of chitosan into this region, resulting in higher contrast in the transmission electron microscope. Interestingly, cyclone morphology is observed in this area, which means that the carbon is arranged in a hexagonal system in the tube. The present invention relates to the properties and functionality of chitosan-bonded carbon nanotubes, which not only facilitate the functionalization of carbon nanotubes, but also carbon nanoparticles for organic solvents due to the many functional groups (-OH and amide) of chitosan. Good dispersibility of the tube can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  One

60 ml of nitric acid and 1 g of carbon nanotubes (manufactured by CNT) were added to the round flask and refluxed at 110 ° C. for 18 hours to introduce carboxyl groups into the carbon nanotubes. At this time, the dispersion was sonicated for 20 minutes prior to reflux for uniform mixing. Next, the carbon nanotubes to which the carboxyl group was introduced were filtered by vacuum in a filtration device equipped with a polycarbonate membrane having a micropore having an average diameter of 0.22 μm, and the filtrate was continuously washed with distilled water until a pH of 7 was obtained. Then dried at 50 ° C. for 30 h under vacuum.

Next, SOCl ₂ was mixed with the dried carbon nanotubes (which have a carboxyl group introduced), and the mixture was refluxed at 70 ° C. for 16 hours to replace the carboxyl groups introduced into the carbon nanotubes with -COCl having more activity. .

After the reaction was completed, the carbon nanotubes introduced with -COCl group were separated through filtration, washed with anhydrous CH ₂ Cl _2, and dried under vacuum at 50 ° C. for 30 minutes. Next, 500 mg of carbon nanotubes into which the -COCl group was introduced were mixed with 30 ml of 1% acetic acid in which chitosan [viscosity average molecular weight (Mv): 2.1 × 10 ⁵ , diacetalization degree: 0.78] was dissolved at 1% concentration. After they were sonicated for 1 hour, they were then transferred to a three-necked round flask and refluxed at 100 ° C. for about 24 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was washed with 1% acetic acid to remove unreacted chitosan, filtered and then washed with distilled water until the pH of the filtrate was 7 to obtain the final product carbon nanotube-chitosan complex. Prepared.

The prepared carbon nanotube-chitosan composite was added to dimethylformamide, dispersed for 5 minutes using ultrasonic waves, and left for one day.

1 shows that the carbon nanotube-chitosan composite is uniformly dispersed in dimethylformamide without aggregation.

In addition, the prepared carbon nanotube-chitosan composite was prepared in pellet form with KBr, and the results of FT-IR spectra analysis were as shown in FIG. 4.

4 demonstrates the presence of graft-bonded chitosan on carbon nanotubes.

In addition, the Raman spectra of the prepared carbon nanotube-chitosan composites were analyzed as shown in b graph of FIG. 3.

The analysis was carried out with a Burkey optic GMBH FT-Raman RFS 100s equipped with an Nd: YAG laser under an atmosphere of liquid nitrogen cooling.

In addition, the thermogravimetric curves of the prepared carbon nanotube-chitosan composites were analyzed by thermogravimetric analysis (TGA 2050, which is a TA device under nitrogen atmosphere).

In addition, the transmission electron microscope photograph of the prepared carbon nanotube-chitosan composite was as shown in FIG. 7, and the transmission electron microscope photograph of the enlarged hollow edge of the prepared carbon nanotube-chitosan composite was as shown in FIG. The transmission electron microscope photograph of the stem portion of the carbon nanotube-chitosan composite was enlarged as shown in FIG. 9.

In the present invention, since the carbon nanotubes are modified with chitosan, a biodegradable natural polymer, biocompatibility and dispersibility in a solvent are excellent.

Therefore, the present invention is very useful as a gene carrier for delivering a specific gene to a target cell.

Claims (10)

delete Method for producing a carbon nanotube-chitosan composite comprising the following steps -Below- (Iii) mixing nitric acid and carbon nanotubes, and then refluxing them to introduce carboxyl groups into the carbon nanotubes; (Ii) The carbon nanotubes to which the carboxyl group is introduced are washed and dried with filtration and distilled water until the pH becomes 7, and SOCl ₂ is mixed therein and then refluxed to introduce the carboxyl groups introduced into the carbon nanotubes. Replacing with a COCl group, (Iii) The carbon nanotubes into which the -COCl group was introduced were filtered, washed with anhydrous CH ₂ Cl ₂ , and dried, and then mixed with acetic acid in which chitosan was dissolved. Manufacturing process and (Iii) washing the prepared carbon nanotube-chitosan complex with acetic acid to remove unreacted chitosan, and then washing with distilled water until the pH reaches 7 after filtration. The method of manufacturing a carbon nanotube-chitosan composite according to claim 2, wherein the mixture of nitric acid and carbon nanotubes is dispersed by ultrasonic waves before refluxing. The method of producing a carbon nanotube-chitosan composite according to claim 2, wherein the nitric acid and carbon nanotube mixture is refluxed at 100 to 120 ° C. for 16 to 20 hours. The method for producing a carbon nanotube-chitosan composite according to claim 2, wherein the carboxyl group-introduced carbon nanotubes are filtered under vacuum with a polycarbonate membrane having micropores. The method for preparing a carbon nanotube-chitosan composite according to claim 2, wherein the carbon nanotubes to which the carboxyl group is introduced are washed and dried under vacuum at 40 to 60 ° C for 20 to 60 minutes. The method of claim 2, wherein the mixture of the carbon nanotubes and SOSl ₂ into which the carboxyl group is introduced is refluxed at 60 to 80 ° C. for 15 to 20 hours. The method for producing a carbon nanotube-chitosan composite according to claim 2, wherein the concentration of acetic acid is 1 to 5%. The method of producing a carbon nanotube-chitosan composite according to claim 2, wherein the chitosan content in acetic acid in which chitosan is dissolved is 0.5 to 3% by weight. The method for producing a carbon nanotube-chitosan composite according to claim 2, wherein the carbon nanotube to which -COCl group is introduced and acetic acid in which chitosan is dissolved are refluxed at 90 to 110 ° C for 18 to 28 hours.

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