KR101537958B1 - Method for regulating opening or shutting of inner-pore of organic nanotube - Google Patents

Abstract

The present invention relates to a method for controlling the opening and closing of an inner pore of a natural nanotube. According to various embodiments of the present invention, in the method of controlling the internal pore opening / closing of the natural nanotube of the present invention, the natural nanotube molecule serves as a nano-valve capable of operating in an aqueous solution and a physiological condition, When the pH is increased to the basic region, the interaction between the molecules of the natural nanotubes is weakened. Thus, the valve is kept open and the drug or gas contained in the natural nanotube pores Because molecules can leach out, they can be useful in controlling drug or gas release due to pH differences.

Description

[0001] The present invention relates to a method for regulating opening and closing of an inner pore of a natural nanotube,

The present invention relates to a method for controlling the opening and closing of an inner pore of a natural nanotube.

Halloysite (Al ₂ Si ₂ O ₅ (OH) ₄ .nH ₂ O, n = 0, 2), a 1: 1 layered aluminum hydroxide silicate mineral belonging to kaolin minerals, has an inner diameter of 30-250 nm and a length of 0.2 It is a natural nanomaterial in the form of a tube capable of applying a nano-sized substance to the inside of the tube at -40 탆. For example, if the release rate of the active substance is lowered by supporting a perfume, a cosmetic, a drug, or an agricultural chemical in the haloisotube, the effect can be sustained for a long time. In order to utilize haloisite as a nanomaterial, it is necessary to separate haloisite, screening technology, and application and control technology of functional active material.

The technology that utilizes haloisite as a carrier or container of nanomaterials can be commonly applied to various industrial fields such as cosmetics, drugs, pesticides, and the like. In Korea, it is difficult to develop commercialization technology in the private sector because the basic research on this technology is not done properly. In the United States, the company patented active substance release control technology using halloysite in 1997. In 2006, the company filed a patent for separating and purifying tubular halloysite from natural clay hallow sites. In particular, the patent US5652976 specifically claims a technique for supporting an active substance on a halo lumen lumen and controlling its release, US 5705191 discloses a technique for further delaying the release rate by adjusting the length of the halo site A technology for sealing the entrance of the nanotube by coating the decomposable polymer has been disclosed. However, there is still no technology for controlling the release rate and the release period to suit the condition of the functional active material in the halo site, There is a limit.

The present invention provides a method for controlling the opening and closing of an inner pore of a natural nanotube which can be usefully used for controlling drug or gas release according to pH difference.

According to a representative aspect of the present invention, there is provided a method for controlling opening and closing of an inner-pore of a natural nanotube according to pH control, wherein the natural nanotube has at least one surface selected from the group consisting of unsubstituted or carboxyl groups and amide groups Substituted amines, substituted halothioates, and immigolites to a pH-adjusted solution to perform an aggregation-de-aggregation reaction, and a method for controlling the internal pore opening and closing of natural nanotubes .

According to various embodiments of the present invention, in the method of controlling the internal pore opening / closing of the natural nanotube of the present invention, the natural nanotube molecule serves as a nano-valve capable of operating in an aqueous solution and a physiological condition, When the pH is increased to the basic region, the interaction between the molecules of the natural nanotubes is weakened. Thus, the valve is kept open and the drug or gas contained in the natural nanotube pores Because molecules can leach out, they can be useful in controlling drug or gas release due to pH differences.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a TEM image and a halo site of a haloisot nanotube according to an embodiment of the present invention. FIG.
FIG. 2 is a graph showing the results of measurement of zeta potential according to pH change of a haloisite according to an embodiment of the present invention. FIG.
FIG. 3 is a graph showing the results of analyzing voids of haloisite according to pH change by N ₂ adsorption and desorption according to an embodiment of the present invention. FIG.
FIG. 4 is a graph showing changes in internal-external pore according to pH change of the haloisot nanotube according to the embodiment of the present invention. FIG.
FIG. 5 is a graph showing FT-IR analysis results of a surface modified with a carboxylic acid according to an embodiment of the present invention.
FIG. 6 is a view showing an SEM image and a diagram according to pH change of a surface modified with a carboxylic acid according to an embodiment of the present invention.
FIG. 7 is a graph showing a result of measurement of a correlation function according to a change in pH of a surface-modified halo acid nanotube with a carboxylic acid according to an embodiment of the present invention. FIG.
FIG. 8 is a diagram illustrating a form of flocculation according to changes in pH of a surface-modified carboxylic acid-containing haloisot nanotube according to an embodiment of the present invention.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

According to an aspect of the present invention, there is provided a method for controlling opening and closing of an inner-pore of a natural nanotube according to pH control,

The natural nanotubes may be prepared by adding one or more selected from the group consisting of haloesite and imogolite, whose surface is unsubstituted or substituted with at least one selected from a carboxyl group and an amide group, to a pH- A method for regulating the opening and closing of an inner pore of a natural nanotube is disclosed.

In the method of controlling the pore opening and closing of the haloisite according to the embodiment of the present invention, the halosite molecule serves as a nano-valve capable of operating in an aqueous solution and physiological conditions. When the pH is acidic, the halosite coagulates, If the pH is increased to the basic range, the interaction between the halosite molecules is weakened and the valve is kept open to allow the drug or gas molecules contained in the halloysite pores to leak out. Can be usefully used to control drug or gas release.

According to another aspect of the present invention, there is provided a method for controlling opening and closing of inner pores of a natural nanotube according to pH control,

When the natural nanotubes are at least one selected from surface-uncoated haloisite and imogolite;

(A) in an acid atmosphere, the surface is unsubstituted halloysite, natural aggregate between nanotubes of one selected from a light aunt bone pore volume of 0.15-0.23 cm ³ / g · Å in or form a natural nanotube particles ,

(B) natural nanotubes having a pore volume of 0.25-0.30 cm < ³ > / g • due to weak binding force between one kind of agglomerated natural nanotubes selected from halo- Forming particles,

(C) a natural nanotube having a pore volume of 0.4-0.6 cm ³ / g 占 탈 in which one kind of agglomerated natural nanotube particle selected from haloisotope and imogolite which is unsubstituted in the basic atmosphere is deagglomerated, And controlling the opening and closing of the inner pore by forming the particles.

According to the embodiment of the present invention, in the acidic solution, the natural nanotube ends are positioned adjacent to the ends of the other nanotubes to be agglomerated (pores in the natural nanotubes), or the ends of the natural nanotubes aggregated in the basic solution And the phenomenon of deaggregation, that is, dispersion (separation of pores inside the natural nanotubes) occurs due to separation from the nanotubes.

In one embodiment of the present invention, the natural nanotube particles in the acidic atmosphere (A) have a zeta potential of -3.5 ± 1 mV in the solution having pH 2, and the natural nanotube particles in the neutral atmosphere (B) The natural zeta potential of the solution is -32.4 ± 3 mV, and the natural nanotube particles in the (C) basic atmosphere have a zeta potential of -44.8 ± 5 mV in a solution of pH 11.

According to the embodiment of the present invention, the aggregation or dispersion (deagglomeration) of the natural nanotubes according to the pH change is caused not by the van der Waals bonding between the natural nanotubes but by the hydrogen bonding, Is a much harder particle.

According to another aspect of the present invention, there is provided a method for controlling the inner-pore opening / closing of a natural nanotube according to pH control,

When the surface of the natural nanotubes is one selected from the group consisting of a halo site and an immigolite in which the surface of the natural nanotube is substituted with at least one selected from a carboxyl group and an amide group;

(RF-1) between the oxygen contained in the carboxyl group on the surface of the natural nanotube and the oxygen contained in the carboxyl group on the surface of the other natural nanotube on the surface of the natural nanotube in the acidic atmosphere, (D _t ) at a pH of 1, and (2) the hydrogen bond at the surface of the natural nanotube (HB-4) Of 576.2 ± 10 nm ² / ms and a hydrodynamic radius (R _h ) of 423 ± 10 nm,

(b) In a neutral atmosphere, on the surface of the natural nanotubes, hydrogen bond (HB-1) is formed on the surface of natural nanotubes adjacent to each other, (HB-2) and (3) hydrogen bonds (HB-3) between the carboxyl groups and the surface of the natural nanotubes and (3) the different carboxyl groups, and the strain diffusion coefficient (D _t ) at pH 7 was 155.3 ± 10 nm ² / ms, forming a natural nanotube particle having a hydrodynamic radius (R _h ) of 1572 ± 20 nm,

(c) in the basic atmosphere, (1) electrostatic repulsion (RF-1) between oxygen contained in the carboxyl group on the surface of the natural nanotube and oxygen contained in the carboxyl group on the surface of the other natural nanotube, (2) (R _h ) of 150 ± 5 nm at a pH of 12 and a deformation diffusion coefficient (D _t ) of 1620.9 ± 10 nm ² / ms at a pH of 12, And controlling the opening and closing of the inner pore by forming the tube particle. The method for adjusting the inner pore opening and closing of the natural nanotube is disclosed.

In one embodiment of the present invention, the natural nanotube particles in the acidic atmosphere (A) have a zeta potential of 40.1 ± 4 mV in the solution having pH 1, and the natural nanotube particles in the neutral atmosphere (B) The solution has a zeta potential of -30.5 ± 3 mV, and the natural nanotube particles in the (C) basic atmosphere have a zeta potential of -45 ± 4 mV in a solution of pH 12.

In another embodiment of the present invention, the acidic atmosphere is an acidic solution having a pH of 4 or less, the neutral atmosphere is a neutral solution having a pH of 5-8, and the basic atmosphere is a basic solution having a pH of 8 or more.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. In addition, it is apparent that, based on the teachings of the present invention including the following examples, those skilled in the art can easily carry out the present invention in which experimental results are not specifically shown.

Halo site  The nanotubes (hereinafter, HNT ) ≪ / RTI >

0.4 g of HNT was added to 5 ml of HCl solution (pH 2), 5 ml of ultrapure water deionized water (DI water, resistivity> 18.2? -Cm) or 5 ml of NaOH solution (pH 11). The HNT was obtained by ultrasonic treatment at room temperature for one day and then lyophilized at -40 ° C and 3.6 mPa for 2 days.

Parameter measurement result

The HNT dried structures with an interlayer distance of 7 (n = 2) were analyzed for pore size, pore surface and pore volume using an X-ray diffraction (XRD) analyzer. The 001 interval of 7.3 using the Bragg rule showed a sharp peak at 2 [theta] = 12 [deg.]. Peaks at the position of 2 [theta] = 8.5 [deg. ] Corresponding to the 10 [A] layer structure were not obtained. The dried HNT showed a 002 reflection peak located at 2 &thetas; = 24.51 DEG, which was changed by 10 ANGSTROM. The position peaks at approximately the same 2 [theta] = 12 [deg.] And 2 [theta] = 8.5 [ deg. ] In the base, neutral and acid treated diffraction peaks were excluded. Acid treatment is potentially damaging to the crystalline structure, while in this experiment the acid treatment solution is sufficiently thin (pH 2) to be able to maintain the nanotube structure. A small loss of peak was observed, but the chemical structure of HNT was retained after acid treatment or base treatment and was supported by XRD data. However, the HNT physical properties were changed depending on the ξ (zeta) - potential.

The pH of the solution may affect the total charge of the HNT. The zeta-potential curve of the HNT relative to the pH of the solution is shown in Fig. The zeta potentials at pH 2, pH 7 and pH 11 are -3.5, -32.4 and -44.8 mV, respectively. Similar to the results obtained by Levis and Daisy. The negative zeta potential was measured at pH 2 to pH 11. The zeta potential at pH 2 was remarkably close to the isoelectric point, and the dispersion was unstable. For this reason, HNTs aggregated and formed into large bundles. On the other hand, HNT provided a significantly lower zeta-potential (about -40 mV) in high pH (pH 8 and above) solutions, and the flocculation and precipitation were not caused by van der Waals interaction between the HNTs . At pH 11, the HNT dispersion was the highest in the tested pH. Figures 2 and S2 show the coagulation and dispersion of HNT. This phenomenon affects HNT pore diameter, pore surface area and pore volume. As shown in Figure 4, in the base solution, the HNTs were well dispersed, each HNT end separated from the other HNT (HNT internal pore opening), whereas the HNT bundle in the acidic solution was adjacent to the end of the other HNT (HNT internal pore clogging). This effect has been demonstrated by the Brunauer-EmmettTeller (BET) method and the BarrettJoynerHalenda method.

The surface area and pore volume of HNT treated with acid (pH 2), neutral (pH 7), and basic (pH 11) were analyzed by nitrogen gas physical adsorption using the BET method. As shown in FIG. 3 (a), the isotherm of the HNT can be represented by the IUPAC IV type classification, which is characteristic of conventional porous materials such as micro-and MCM-41. The hysteretic model remained in IV form while the adsorbed gas volume increased at high pressure range (P / P ₀ > 0.95) and low pressure (P / P ₀ <0.95) The opposite result was confirmed. The above-described porous size distribution depending on the solution pH was analyzed by the BJH method, and the results are shown in FIG. 3 (b).

The surface area, pore volume, and pore size of the HNT sample are shown in Table 1. HNT samples were prepared at the same temperature. The micropore volume t-plot showed that the single point absorption total pore volume was smaller than 209 nm at P / P ₀ = 0.99, and the cumulative volume of BJH adsorption of pores between 1.7 nm and 300 nm was increased by high pH treatment . Substitutional pore volume and pore diameter substitutional tendency (4V / A by BET) and BJH absorption average pore diameter (4V / A) of the HNT sample were increased due to lower solution pH. However, the total surface area (BET surface area, S4 ESI †) and mesopore surface area (single point absorption total pore volume P / P ₀ = 0.1999, 1.7 nm and 300 nm diameters, excluding the micropore surface area) And BJH absorption average surface area) were reduced by high pH treatment. The HNT pore diameter measured by the BET isotherm is valid only when the sample has a cylindrical shape. The 4V / A equation was used to calculate the pore diameter of the cylindrical material. In the case of acid and neutral treatments, the "correct" frequency distribution is usually made up of multiple HNTs, but the pore diameter is measured because the base treated HNT is predominantly dispersed.

The pore size distribution plot of the base treated HNT (Figure 3 (b) (ii)) shows a narrow distribution of diameters ranging from 16 nm to 50 nm. The basis for the various pore diameters depends on the HNT treatment, and the variety of pore volumes does not vary. The calculation results of BJH adsorption average pore diameter (4V / A) and diameter width using adsorption average pore (4V / A according to BET) are mostly similar to the actual pore diameters calculated from the SEM or TEM measurement device as average values.

Specifically, the HNT has two N ₂ adsorption and desorption reaction sites. This is consistent with (i) and (ii) of FIG. 3 (b) corresponding to diameters of 2-16 nm and 16-50 nm, respectively. The HNTs were well dispersed in a basic solution, as shown in Fig. 4 (a). Thus, as shown in Figure 3 (b) (i), the volume of space between the HNTs that is related to the peak for a diameter of 2-16 nm is reduced, but the total pore volume and pore size increase in BET and BJH analysis do. This increase is due to the dispersion (opening) of the HNT, and the HNT prevents the mesopores of the other HNT from disappearing by dispersion. For this reason, the reaction pore size and pore volume for N ₂ adsorption and desorption are consequently increased. In acidic solutions, the HNTs aggregate and block the mesopores of other HNT tubes. For this reason, available pore volume and pore size for gas adsorption decrease. On the other hand, the pore area appears to decrease by the increase of pH (S _BET and S _BJH ). The total surface area, summarized in Table 1, is influenced by the interstices and internal spaces of the HNT pores. The interstitial surface area increases significantly when the HNT is dispersed in the basic solution, while the interstitial surface area increases due to the opening of the mesopores of the HNT. The total surface area is more influenced by the interspace surface area. For this reason, the S _BET and S _BJH results decrease due to the pH increase of the solution. Changes in pore volume, pore area and pore size of the BET and BJH analyzes indicate the opening and closing of the HNT based on coagulation and dispersion by base, acid or neutralization.

pH treatment Acid (pH about 2) Neutral (pH approx. 7) Basic (pH about 11) Pore volume
(cm &lt; ³ &gt; / g) V _BET 0.22 0.25 0.29 V _micro 0.0021 0.0034 0.0047 V _BJH 0.22 0.24 0.29 S _sp 57.9 52.7 48.7 Pore area
(m ² / g) S _BET 59.7 53.8 49.3 S _micro 5.67 8.08 10.4 S _ext 53.0 45.7 38.9 Pore size
(nm) S _BJH 61.6 55.9 49.8 d _BET 14.7 18.9 23.4 d _BJH 14.3 18.2 23.3

V _BET (single point adsorption total pore volume of pores less than 209 nm at P / P ₀ = 0.99), V _micro (t-plot micropore volume), V _BJH (BJH adsorption cumulative volume of pores between 1.7 and 300 nm diameter _{), S sp (single point surface} area at P / P 0 = 0.1999), S BET (BET surface area), S micro (t-plot micropore area), S ext (t-plot external surface area), S BJH ( BJH adsorption cumulative surface area of pores between 1.7 and 300 nm diameter), d _BET (adsorption average pore width (4V / A by BET)), d _BJH (BJH adsorption average pore diameter (4V / A)

Production of a haloisite functionalized with carboxylic acid groups and a dispersion solution containing the same

(1) Step 1: Preparation of an amino group-functionalized haloisite

The amino group-modified HNT (HNT-NH ₂ ) was synthesized using pure HNT by the following method. HNT was dispersed by adding 100 ml of toluene for 2 hours using ultrasonic waves and stirred for 2 hours (400 rpm). Next, 3 ml of triethylamine and an APTES solution were added to the HNT solution, and then the mixture was stirred at a temperature of 80 ° C and a nitrogen gas atmosphere for one day. The HNT-NH ₂ was washed several times with deionized water and ethanol, and then collected and dried at a temperature of 50 ° C under a pressure of 1.1 Pa.

(2) Step 2: Preparation of a haloside functionalized with a carboxylic acid group

HNT-COOH was prepared from the HNT-NH ₂ obtained in step 1 above. A portion of 2 ml of 0.1 M succinic anhydride and the dried HNT-NH ₂ obtained in Step 1 were added to DMF and mixed, and then the mixture was stirred for one day. The collected HNT-COOH was dried in a vacuum oven at 50 &lt; 0 &gt; C and 3.6 mPa.

(3) Step 3: Preparation of HNT-COOH dispersion solution

HNT-COOH Acidic, basic and neutral solutions (0.025 mg / ml) were prepared. Sodium hydroxide solution (pH 12) was used as a basic solution, and hydrochloric acid (pH 1) was used as an acidic solution. HNT-COOH (0.5 mg) was dissolved in deionized water (1 ml), and the solution was directly transferred to a whistle-light scattering cell (13 × 100 mm) using a 0.80 μm cellulosic acetate membrane filter. HNT-COOH was dispersed in the solution for 2 h and 5 s, respectively, using a sonicator and an ultrasonic cooker, and each solution was stored at room temperature for one day.

Parameter measurement result

As shown in FIG. 5, IR spectra of pure HNT and HNT-COOH were confirmed and the hydroxyl groups contained in the outer surface of the HNT were confirmed at 3703 cm ^-1 and 3622 cm ^-1 . On the surface of HNT, the hydroxy group was modified with carboxylic acid (HNT-COOH). After the hydroxy groups of the HNT substituted by amino and carboxylic acid group, a wider distribution of alcohol IR peak disappeared at 3200 cm ^-1 to 3500 cm ^-1, carboxylic acid and secondary amine vibration peak is 3400 cm ^-1 to 3600 cm ^{- 1} . The peak is very weak and broad due to the small number of functional groups and hydrogen bonding interactions. Carbonyl vibration was observed at 1580 cm ^-1 and 1700 cm ^-1 of the IR of the HNT-COO, respectively, of the amide and carboxylic acid groups. The peak at 1105 cm ^-1 appears to have appeared after the small distortion of the structure has been deformed. Therefore, the modification of the functional group to carboxylic acid in the work was confirmed by IR spectrum.

Figure 6 shows an SEM image and a schematic diagram of HNT-COOH due to the pH of the solution. The morphology of HNT-COOH from the basic, acidic and neutral solutions was determined using SEM and AFM. The sample was obtained from a deionized water solution (pH 7), and as shown in FIG. 6B, HNT-COOH was highly aggregated due to the mutual bonding of the carboxylic acid and amide groups of the halosite tube. On the other hand, dry samples obtained from acidic and basic solutions were better dispersed than those obtained from neutral solutions on silicon wafers as shown in Figs. 6a and 6c, which can be theoretically explained as a result of repulsive forces . Since the carboxylic acid turns into a carboxylate anion at high pH and pushes out and coagulates to become unstable, the dispersion is much larger in the basic solution than in the neutral solution. Furthermore, the above degree of dispersion is higher in the dried HNT-COOH obtained in the basic solution than in the acid solution, but the explanation of these results can not be obtained directly from the image of the dried sample. Among the many weaknesses of SEM, the first is that the images obtained from SEM and AFM can not naturally represent the in situ form and the aggregation state of the nanotubes in solution. The propensity of the solution agglomeration can be identified using direct imaging techniques. Second, the mutual bonding between the silicon wafer and HNT-COOH affects the sample substrate. In order to overcome this problem, MA-DLS (multiple angle polarized dynamic light scattering) experiments were used in solution. Dynamic light scattering is known as optical property spectroscopy, and this technique can measure particle size in solution.

Figure 7 shows the experimental results of the correlation function with vertical-vertical (incident line velocity is vertically polarized and scattered line velocity is also vertical); The figure shows that the scattering angles of 0.5 mg / ml HNT-COOH in acidic (A), basic (B), and neutral (N) solutions are 30, 45, 60, 75, 90, It is the measured probability distribution function. According to the probability distribution function of HNT-COOH in the basic solution (pH 12) in FIG. 7A, the distribution was well measured at each scattering angle, and HNT-COOH was found to be simply dispersed at pH 12. Figures 7b and 7c show the distribution of HNT-COOH increased in acidic and neutral solutions, but the degree of broadening can be neglected due to the hydrodynamic radius calculated as the average fall time as a result of the MA-DLS experiment . Furthermore, the coagulated HNT-COOH particles are sufficiently simple to disperse because the distribution is suitable for the DLS experiment, and there is no error in calculation of the inferred hydrodynamic radius using the distribution data. 7d, the decay rate is calculated by the equation Γ = 1 / τ, and τ, which is the decay time value, is calculated by the scattering angle. Figure 7 shows the strain diffusion coefficient (D _t ) in two parameters, and the slope (Γ = D _t q ² ) of each point along the line is shown in Figure 4d. The hydrodynamic radius (R _h ) was calculated by the Stokes-Einstein equation. Table 2 below shows the D _t and R _h values of HNT-COOH in the three solutions. The D _t value is 1620.9 nm ² / ms at pH 12, 576.2 nm ² / ms at pH 1, and 155.3 nm ² / ms at pH 7. Furthermore, the degree of agglomeration / dispersion in the solution according to the above pH was confirmed at the R _h value. The R _h values are 150 nm at pH 12, 423 nm at pH 1, and 1572 nm at pH 7. These results are related to SEM images and are generalized under dry conditions.

Fig. 8 is a structural view showing a binding form of HNT-COOH aggregation. Fig. Elastic side branches can be made into a perfect shape using a hydrogen bond (HB) network through a mutual bond between amide and carboxyl groups. As shown in Fig. 8A, three side branches associated with HB mutual binding are identified. If HNT-COOH is adjacent to each other, the side chain is bound to HB-1 (branch-branch and branch-surface bond) and HB-2 (branch-surface bond) via HB-3 will be.

Three types of HB mutual bonds can be maximal in neutral and acidic and basic conditions include the undesirable effect of extra hydrogen in the dehydrogenation reaction, which interferes with effective HB mutual binding. The reason why HNT-COOH shows better agglomeration in acid solution than in basic solution can be explained below. In the acidic condition, the extra hydrogen surrounds the HNT surface oxygen, which is weakened in HB bond with oxygen in the side chain carboxyl group and amide group. The extra hydrogen can adjust the bond between the HNT and COOH via the fourth order HB mutual coupling (HB-4), as shown in FIG. 8B. Hydrogen in solution tends to form an oxonium complex filled with oxygen atoms connected to two Si atoms on the surface of HNT-COOH. The hydrogen-oxygen bond length was found to be 1.01 Å, which agrees well with conventional theory and experimental studies. The two nanotube molecules are connected to each other by hydrogen ions with very stable oxonium ions. This theory is consistent with what Zhang studied. While the bond between hydrogen and oxygen atoms is not very strong, hydrogen bonding with the oxygen of Si-O-Si on the HNT surface can act as a bridge connecting the HNT. This bond is possible because of most of the HNT surface structure including the Si-O-Si form, similar to the structure of the silica particle or silicon oxide material, and all of the above manufacturing methods can be performed without any energy barrier. The dispersibility was thus weakened by the binding of hydrogen through HB-4 in the acidic solution. On the other hand, basic conditions cause dehydrogenation of the carboxyl group. Thus, as shown in Fig. 8 (c), it was lightly filled with the side chain (RF-1) and the HNT surface oxygen (RF-2), which electrostatically repel each other differently. The HB-4 bond can not also be required because of the insufficient hydrogen. Therefore, it is worth mentioning as a mechanism of HNT-COOH aggregation based on HB-bonds that can be controlled by pH conditions.

HNT-COOH was found to be slightly negative (-30.5 mV), basic solution (pH 12) in the positive solution (40.1 mV), neutral solution (pH 7) Has a negative charge (-45 mV). Charge repulsion of HNT according to the solution state also affects the cohesion and dispersion characteristics.

The acidic solution (pH 1) Neutral solution (pH 7) Basic solution (pH 12) D _t 576.16 nm ² / ms 155.30 nm ² / ms 1620.89 nm ² / ms R _h 423.75 nm  1572.11 nm  150.54 nm

Accordingly, in the method of controlling the opening and closing of the inner pore of the natural nanotube of the present invention, the natural nanotube molecule serves as a nano-valve that can operate in an aqueous solution and a physiological condition. When the pH is acidic, When the pH is maintained in the closed state and the pH is increased to the basic region, the interaction between the molecules of the natural nanotubes is weakened, and the valve may be kept open to allow the drug or gas molecules contained in the natural nanotube pores to leak out and can be usefully used to control drug or gas release according to pH difference.

Claims (7)

delete delete delete A method for controlling the inner-pore opening / closing of a natural nanotube according to pH control,
Adding the natural nanotubes, which are at least one selected from the group consisting of halosite and amomolgolite whose outer surface is substituted with a carboxyl group, to a pH-adjusted solution to perform an aggregation-de-aggregation reaction,
(a) In an acidic solution having a pH of 4 or less, it is necessary to form on the surface of the natural nanotubes, (1) electrostatic repulsion between the oxygen contained in the carboxyl group on the surface of the natural nanotube and oxygen contained in the carboxyl group on the surface of the other natural nanotube -1), (2) the carboxy group and the natural nanotube surface hydrogen bond (HB-2) and (3) the natural nanotube surface-natural nanotube surface hydrogen bond (HB-4) Dt) of 576.2 ± 10 nm ² / ms and a hydrodynamic radius (Rh) of 423 ± 10 nm,
(b) In a neutral solution having a pH of 5-9, on the surface of the natural nanotubes, (1) hydrogen bonds between the carboxyl groups of the surfaces of the different natural nanotubes, -1), (2) the hydrogen bond (HB-2) on the surface of the carboxyl group and the natural nanotube surface, and (3) the hydrogen bond (HB-3) between the different carboxyl groups. 155.3 ± 10 nm ² / ms and having a hydrodynamic radius (Rh) of 1572 ± 20 nm,
(c) In the basic solution with a pH of 9 or more, electrostatic repulsion (RF-1) between the oxygen contained in the carboxyl group on the surface of the natural nanotube and the oxygen contained in the carboxyl group on the surface of the other natural nanotube, (Rt) of 150 ± 5 nm at a pH of 12 and a deformation diffusion coefficient (Dt) of 1620.9 ± 10 nm ² / ms at a pH of 12, The nanoparticle particles are formed to control the internal pore opening and closing,
(A) the natural nanotube particles in the acidic atmosphere have a zeta potential of 40.1 ± 4 mV in a solution having a pH of 1, and (b) the natural nanotube particles in the neutral atmosphere have a zeta potential of -30.5 ± 3 mV. In the (c) natural atmosphere, the natural nanotube particles have a zeta potential of -45 + 4 mV in a solution of pH 12,
Characterized in that the nanoparticles are used for drug release or gas release control. delete delete delete

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