JP2016008270A - Nanoparticle and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form various nanoparticles by using a temperature-responsive block copolymer.SOLUTION: Nanoparticles of a block copolymer which has another copolymer introduced into the core site thereof are formed by raising temperature of an aqueous solution of a temperature-responsive block copolymer and another temperature-responsive copolymer having a structure identical to one block of the block copolymer. The nanoparticles having various characteristics can be formed by appropriately selecting structures of the block copolymer to be used and the other copolymer, the number of repetition of units constituting them, and combinations of terminal functional groups or the like.

Description

  The present invention relates to nanoparticles, and more particularly, to nanoparticles formed in a self-organized manner by mixing a copolymer and a block copolymer and raising the temperature.

  Various types of “smart” polymer nanoparticles have been applied in a wide range of fields (Non-Patent Documents 1 and 2). Each of these nanoparticles is usually created in the laboratory, so these properties (monomers, size, structure, charge, composition, etc.) are unique and there is concern that this may cause development delays. The Designing nanoparticles with variable properties is a major challenge and will make a significant contribution to the whole world.

  For the production of nanoparticles, multifunctional block copolymers have been reported by the development of controlled living radical polymerization (CLRP) and click chemistry (Non-Patent Documents 3 to 6). However, the number of stimulus responsiveness of block copolymers is still limited and it is usually difficult to change the stimulus responsiveness after polymerization. In order to solve this problem, it has been proposed to construct nanoparticles in a self-organizing manner from a mixture of simple block copolymers (Non-Patent Documents 7 to 9). As a trigger for self-organization, temperatures were used to simplify handling (reversibility, no special equipment required, and no addition of chemicals). A temperature-responsive polymer is one of the most well-studied polymers, and is applied to a wide range of protein complexes, drug delivery systems (DDS), cell engineering and devices (Non-Patent Documents 10 to 10). 15). By increasing the temperature of the solution, these temperature-responsive polymers can reversibly change their physicochemical properties. The temperature at which this change occurs is known as the Lower Critical Solution Temperature (LCST). The inventor of the present application has previously proposed to produce a micelle shell (multifunctional shell) using two or three kinds of temperature-responsive block copolymers. These block copolymers have a common LCST, and above LCST formed a mixed shell of nanoparticles. The properties of the shell were precisely adjusted by the mixing ratio of the block copolymer (Non-patent Document 9).

  However, a general amphiphilic block copolymer requires the addition of an organic solvent and dialysis in order to prepare an aggregate. Also, due to the high dispersion stability of the aggregate, recovery takes time. The inventors of the present application have succeeded in producing a multifunctional shell by using a temperature-responsive polymer in advance and raising the temperature in water without using an organic solvent (Non-patent Document 9). Moreover, since the block copolymer has a two-step temperature response, rapid recovery was possible. However, in the method shown in Non-Patent Document 9, the control of the core portion of the aggregate is insufficient. Accordingly, an object of the present invention is to control the functionality of the core portion of the assembly by using a block copolymer and a mixture of copolymers.

According to one aspect of the present invention, a temperature-responsive copolymer is composed of a plurality of blocks, and one block in the plurality of blocks has the same structure as the copolymer. Nanoparticles comprising a copolymer are provided.
Here, the plurality of units constituting the one block and the plurality of units constituting the copolymer are the same, but the number of repetitions of each of the plurality of units in the one block and the copolymerization are the same. The number of repetitions of each of the plurality of units in the body may be the same or different.
The nanoparticle includes a core portion including a portion hydrophobized by raising the temperature of the block copolymer and the copolymer hydrophobized by being heated, and other shell portions And may consist of:
The weight of the hydrophobized copolymer contained in the core portion may be equal to or less than the weight of the block copolymer constituting the nanoparticles.
The block copolymer is 2- (2-methoxyethoxy) ethyl methacrylate (abbreviated as MEO ₂ MA), oligo (ethylene glycol) methacrylate (abbreviated as OEGMA), 6-acetylthiohexyl acrylate (abbreviated as ATA). ) And 2- (diisopropylamino) ethyl methacrylate (abbreviated as DP) are polymerized, and the first block having the structure P (MEO ₂ MA-co-OEGMA) and P A block copolymer P (MEO ₂ MA-co-OEGMA) -b-P (MEO ₂ MA) having a second block having a structure of (MEO ₂ MA-co-OEGMA-co-ATA-co-DP) -Co-OEGMA-co-ATA-co-DP) and the copolymer is MEO ₂ Four types of monomers, MA, OEGMA, ATA and DP, are polymerized, and have the same structure as P (MEO ₂ MA-co-OEGMA-co-ATA-co-DP) as in the second block. It is a copolymer, and the monomer may correspond to the unit.
The repeating numbers of the monomers MEO ₂ MA and OEGMA in the first block of the block copolymer are 48 and 20, respectively, and the monomer MEO ₂ MA in the _second block of the block copolymer, OEGMA, said block copolymer comprising repeating number of ATA and DP are respectively 25,4,3 and 4 _{P (MEO 2 MA 48 -co-} OEGMA 20) -b-P (MEO 2 MA 25 -co- OEGMA ₄ -co-ATA ₃ -co-DP ₄ ), and the repeating number of monomers MEO ₂ MA, OEGMA, ATA and DP in the copolymer is 17, 2, 3 and 2, respectively, or each a 33,5,4 and 5, wherein the copolymer _{P (MEO 2 MA 17 -co-} OEGMA 2 -co-ATA 3 co-DP ₂₎ or _{P (MEO 2 MA 33 -co-} OEGMA 5 -co-ATA 4 -co-DP 5) and may be those represented.
Moreover, you may have a functional group at the terminal of the said block copolymer.
Further, another substance may be bonded to the functional group.
The other substance may be selected from the group consisting of proteins, nucleic acids, enzymes, small molecules, inorganic particles, and quantum dots.
The other substance may be arranged on the nanoparticle surface.
Moreover, you may decompose | disassemble into the said copolymer and the said block copolymer by making it lower than the minimum critical solution temperature of the said 2nd block in the said copolymer and the said block copolymer in water.
Further, it may be formed again by raising the temperature to the lower critical solution temperature or higher.
Moreover, the said core site | part is gelatinized and you may enclose another substance in the inside.
The other substance may be selected from the group consisting of pharmaceuticals, enzymes, proteins, nucleic acids, and inorganic particles.
According to another aspect of the present invention, the temperature responsive copolymer is composed of a plurality of blocks, and one block in the plurality of blocks has the same structure as the copolymer. The manufacturing method of the nanoparticle which heats up the aqueous solution containing these block copolymers more than the minimum critical solution temperature of the said one block of the said copolymer and the said block copolymer.
Here, the first nanoparticles produced by the method shown above and the method of claim 15 shown above, wherein the first nanoparticles are the copolymer and the block copolymer. The temperature of the aqueous solution containing the second nanoparticles having different weight ratios is lowered below the lower critical solution temperature, and the first and second nanoparticles are decomposed into the copolymer and the block copolymer. Then, after the decomposition, the temperature of the aqueous solution may be raised to the lower critical solution temperature or higher to produce third nanoparticles having a weight ratio different from any of the first and second nanoparticles.
The aqueous solution may further contain a buffer solution.
Moreover, the terminal of the block copolymer may have a functional group.

  The present invention produces nanoparticles by mixing a block copolymer and a copolymer and raising the temperature, whereby the particle size of the nanoparticles, the core portion (the nanoparticle is composed of a core portion and a shell portion). It is possible to control the functionality and the surface properties of the nanoparticles. Moreover, since the temperature-responsive polymer is used, the nanoparticles once formed can be dissolved by lowering the temperature, and the nanoparticles can be constructed again by raising the temperature. Furthermore, since the block copolymer used here has two LCSTs that are temperature responsive (that is, the LCSTs of a plurality of types of blocks constituting the block copolymer are different from each other), Can be recovered quickly. When combined with the multifunctional shell previously proposed in Non-Patent Document 9 by the inventors of the present application, nanoparticles can be prepared in response to various needs. Moreover, since the nanoparticle of the present invention can incorporate a hydrophobic material having a weight substantially equal to the weight of the nanoparticle into the core portion, it can be applied as an efficient carrier for various substances.

The figure which illustrates notionally the preparation of the mixed nanoparticle by the assembly | assembly of the copolymer of this invention, and a block copolymer, and the characteristic of the mixed nanoparticle produced in that way. The figure which shows the structural formula of the block copolymer used in the Example of this invention, and a copolymer. _P for mixing nanoparticles made by the temperature-controlled solution (MEO 2 MA-co-OEGMA -co-ATA-co-DP) (4C) and _{P (MEO 2 MA-co-} OEGMA) -b- shows the structure of _{P (MEO 2 MA-co-} OEGMA-co-ATA-co-DP) (2Cb4C). (A) The figure which shows the relationship between the particle size / PDI of the mixed nanoparticle in the solution which mixed 0.5 wt% of 2Cb4C and 4C (short) in pH7.4 PBS of 40 degreeC, and the weight% of 4C (short). (B) The figure which shows the relationship between the particle size / PDI of the mixed nanoparticle in the solution which mixed 0.5 wt% of 2Cb4C and 4C (length) in pH7.4 PBS of 40 degreeC, and the weight% of 4C (length). The temperature was increased from 15 ° C. to 40 ° C. (5 ° C. increase every 10 minutes). The figure explaining reconstruction of the mixed nanoparticle by controlling the temperature of a solution. Two kinds of nanoparticles having different sizes (size / PDI / 4C (long) amount: 74 ± 30 nm / 0.16 / 50 wt% and 33 ± 8 nm / 0.08 / 0 wt%) were mixed at 40 ° C. The total amount of 4C (long) was 10 wt%. (A) The figure which shows the transmittance | permeability change with respect to temperature about the solution which mixed 0.5 wt% of 2Cb4C and 4C (length) in pH7.4 PBS. (B) Size distribution histogram at 45 ° C. of mixed nanoparticles composed of 2Cb4C and P (MEO ₂ MA ₁₉ -co-OEGMA ₂ ) (total concentration 0.5 wt%, mixing ratio 1: 1). (C) A chart showing whether or not nanoparticles can be formed by mixing 2Cb4C with various compositions, chain lengths, and copolymers of LCST (◯: created, x: not created). Here, mixing of 2Cb4C and the copolymer was performed with PBS of pH 7.4, and the mixing ratio was 1: 1. The AFM image of the nanoparticle which consists of block copolymer 2Cb4C.

  In the present invention, the elements constituting the polymer nanoparticles are divided into two. Specifically, as shown in FIG. 1, it is a copolymer (poly (A)) and a block copolymer (poly (A) -b-poly (B)). That is, the copolymer (poly (A)) is the same as some of the blocks forming the block copolymer (poly (A) -b-poly (B)) (more Exactly, the same thing is used except for the number of repetitions of each unit constituting the block (nanoparticles are formed even if the number of units does not match). For example, block copolymers and copolymers whose structure is shown in FIG. 2 can be designed to initiate assembly at the same temperature (eg, around 35 ° C.) to prepare mixed nanoparticles. This temperature can be easily controlled by the composition. Also, by lowering the temperature of the mixed nanoparticle solution below the temperature at which these polymers start to assemble, the assembly of the copolymer and block copolymer that made up the mixed nanoparticles can be dissolved and dissolved. To do. Thereafter, by adding a new block copolymer, aggregates having different particle diameters, that is, mixed nanoparticles can be reconstructed as shown in FIG.

  If, for example, carboxyl groups are provided at the ends of the block copolymer, these carboxyl groups are arranged on the surface at the time of assembly. If the reaction of a carboxyl group and an amine group is utilized, various materials such as molecules and antibodies can be bound to a block copolymer and arranged on the surface of the mixed nanoparticles. Further, the carboxyl group at the end can be converted into a nonionic one or a click reaction by selecting a RAFT agent at the time of polymerization.

  By mixing the block copolymer and the copolymer, it is possible to precisely design the particle size and functionality of the mixed nanoparticles of the present invention. Various parameters of the mixed nanoparticles can be controlled as follows, for example. Since various parameters can be adjusted relatively easily in this way, the present invention can be used to create a standard kit for preparing a wide range of nanoparticles by combining several block copolymers and copolymers. Can also be provided.

1. Regarding the temperature responsiveness of block copolymers and copolymers Since the temperature-responsive block copolymers and copolymers that are the raw materials for the nanoparticles of the present invention are synthesized by living radical polymerization, their chain lengths The composition can be accurately controlled. This makes it possible to freely design the structure and temperature response of each polymer.

2. Particle size control The particle size can be adjusted in the order of several nanometers by mixing the copolymer, but for larger orders (several tens of nanometers), this is achieved by adjusting the chain length of the block copolymer. Is done. Thereby, the particle size of the mixed nanoparticles of the present invention can be designed in the range of several tens nm to several hundreds nm.

3. Block copolymer and copolymer structure / composition: pH responsiveness and biodegradability were successfully incorporated into the copolymer, but other stimuli responsiveness (eg photoresponsiveness, molecular responsiveness) was incorporated This makes it possible to produce a wide variety of composite nanoparticles. This makes it possible to develop these block copolymers and copolymers as options for the above-described kit for producing nanoparticles, for example.

4). About the terminal of a block copolymer Since the block copolymer used by this invention is compoundable by RAFT (reversible addition-fragmentation chain transfer) polymerization, the terminal originates in a RAFT agent. Currently, multiple RAFT agents are available for purchase, and their ends vary from nonionic, cationic, anionic, and click reactive groups. By using these commercially available RAFT agents or by synthesizing RAFT agents, various types of terminal block copolymers can be synthesized and provided as options for materials contained in the kit described above.

5. About the reactivity of the terminal of a block copolymer As above-mentioned, since various terminal can be arrange | positioned in a block copolymer, the mixed nanoparticle of this invention is combined with various molecules, proteins, nucleic acids, etc. Can do. These bonded materials are also arranged on the surface of the mixed nanoparticles.

6). About the diversity of the core part of a mixed aggregate Since the core part of the mixed nanoparticle of the present invention can be gelled, drugs, enzymes, proteins, nucleic acids, inorganic particles and the like can be encapsulated therein. This gelation is performed, for example, by deprotecting copolymerized ATA and utilizing crosslinking between exposed thiols (—SH). Further, the amount of inclusion can be controlled by adjusting the crosslinking density and the amount of crosslinking for gelation. As long as the response temperatures of the materials to be mixed are approximate, block copolymers and copolymers having different structures can be incorporated into the same particle.

  In the following, the present invention will be described in more detail based on examples.

  In the present application, attention was focused on a mixed core of nanoparticles composed of the copolymer and block copolymer shown in FIG. Here, a core part is the site | part hydrophobized by temperature rising. It has been found that this block copolymer can incorporate into the core a hydrophobic copolymer of the same weight (that is, a copolymer that has also been hydrophobized by heating). Further, the average particle diameter of the mixed nanoparticles could be accurately controlled within the range of 5 nm by the mixing ratio (mixing ratio range: 10 to 50 wt%; where [mixing ratio] = [copolymer weight] / ([[ Copolymer weight] + [block copolymer weight]). The structure of the nanoparticles can be reconstructed by controlling the temperature of the solution, and the microstructure of the mixed copolymer It has also been found to be strongly influenced by molecular weight and LCST, and with this understanding, the nanoparticles can be designed accurately and easily by selecting the copolymer and block copolymer to be mixed. After designing the nanoparticles, the target nanoparticles are constructed by dissolving the copolymer in an aqueous medium at a temperature below the LCST and raising the temperature above the LCST. Number and type of responsiveness, Surface properties, formation control of cross-linked structure, and extends to encapsulation of various materials.

FIG. 3 shows the respective structures of the copolymers (4C and 2Cb4C). 2- (2-methoxyethoxy) ethyl methacrylate (MEO ₂ MA) / oligo (ethylene glycol) methacrylate (OEGMA), 6-acetylthiohexyl as monomer Acrylate (6-acetylthiohexyl acrylate, ATA) and 2- (Diisopropylamino) ethyl methacrylate (DP) were selected to control temperature, biodegradability, and responsiveness to pH, respectively ( Here, the separator between the first two monomers, MEO ₂ MA and OEGMA, is “/” because the temperature response is controlled by MEO ₂ MA and OEGMA. This is because the meaning of the two combinations is different from the others). The LCST of P (MEO ₂ MA-co-OEGMA) and P (MEO ₂ MA-co-OEGMA-co-ATA-co-DP) was adjusted to 60 ° C. and 35 ° C., respectively. The relationship between these LCSTs and the amount of X in the binary copolymer P (MEO ₂ MA-co-X) (specifically, mol% of X. Expressed in another form, the number of X units) )), It was possible to predict LCST even for complex compositions (eg, quaternary copolymers). For the design of the properties of 4C and 2Cb4C, P (MEO2MA-co-X) (where X = OEGMA, ATA and DP) in various solutions (milliQ, PBS pH 7.4 and buffer solution pH 5.5). ) LCST was measured.

Crosslinks (—S—S—) by thiol (SH) groups can be broken in a cell due to a reducing environment (Non-patent Document 16), and thus are used as drug carriers. However, since the thiol group functions as a radical scavenger, it is difficult to directly polymerize a monomer having a thiol group by radical polymerization. Therefore, the ATA monomer was selected because it protects the thiol group and can be easily deprotected after polymerization (Non-patent Document 17). Indeed, the efficiency of ATA deprotection in P (MEO ₂ MA-co-ATA) can be controlled from 36.7% to 67.7% depending on the concentration of the reducing agent and the reaction time. DP (pK _a = 6.3) is applied as _a pH-responsive polymer in biomaterials. The proton sponge effect (Non-Patent Document 18) causes endosome escape from the cationic charge of the DP unit of the polymer. These biocompatibility, biodegradability and endosomal escape are among the capabilities required for drug carriers. According to the present invention, the functionality of the core can be easily designed simply by mixing a block copolymer and a copolymer having a common LCST.

As an example of the copolymer used in the present invention, a quaternary copolymer P (MEO ₂ MA-co-OEGMA-co-ATA-co-DP) (4C) and a block copolymer P (MEO ₂ MA-co) are used. _{-OEGMA) -b-P (MEO 2} MA-co-OEGMA-co-ATA-co-DP) and were prepared (2Cb4C). This block copolymer has the same 4C block as a common temperature-responsive block (LCST: 35 ° C. in PBS at pH 7.4) (FIG. 3). 2Cb4C has a carboxyl group at the end of the polymer chain, and these carboxyl groups are located on the nanoparticles after self-assembly. Its position strongly affects the solution properties (Non-Patent Document 19), and carboxyl groups are used for reaction sites with small molecules, enzymes, proteins, nucleic acids and inorganic materials. Importantly, the carboxyl group is derived from the RAFT agent, and RAFT agents having various functional groups (nonionic, succinimide, azide group, etc.) can be purchased or synthesized. Of course, the terminal group of dithioester can also be used as a reaction point (nonpatent literature 20, 21).

  FIG. 4 shows the particle size and PDI (polydispersity index) of mixed nanoparticles of 2Cb4C and 4C (short) or 4C (long) in PBS at 40 ° C. The particle diameter of the 2Cb4C nanoparticles was 33 ± 8 nm (PDI: 0.079) (from AFM, it was also confirmed that the 2Cb4C nanoparticles were spherical (FIG. 7), while FIG. 4 (A). As shown in Fig. 4, as the mixing amount of the 4C (short) copolymer is increased, the particle diameter of the mixed nanoparticles slightly increases with a narrow distribution of PDI of less than 0.1. It was noteworthy that the block copolymer was able to encapsulate a copolymer of the same mass in the (short) amount of 50 wt%). It is possible to incorporate 4C (short) as much as 340% ([weight of copolymer 4C incorporated in core] / [weight of 4C portion of block copolymer in core] × 100) into the core. It means that you can do it from 20 ℃ When the temperature was directly increased to 40 ° C., the relationship between the particle size and the amount of the copolymer contained was the same as when the temperature was slowly increased, and this surprisingly high encapsulation rate and stability was also exhibited by the carboxyl groups on the surface. This carboxyl group is derived from the RAFT agent and its functional group is also used as a reaction site with materials such as molecules, peptides, antibodies, proteins, nucleic acids and inorganic particles.

  The particle size of the mixed nanoparticles was precisely controlled in the range of 5 nm by a mixing ratio of 4C (short). Aggregation or precipitation was observed when the mixing amount exceeded 70 wt%. Further, by using the FRET (fluorescence resonance energy transfer) phenomenon (Non-Patent Documents 22 and 23), the mixed core of nanoparticles has a copolymer (having a pyrene unit) and a block copolymer. It was shown to consist of a polymer (having coumarin 343 units). After mixed nanoparticles were formed, high intensity FRET was observed. FIG. 4B shows the particle size of the mixed nanoparticles between 2Cb4C and 4C (long). The particle size was slightly larger than the same amount of 4C (short). Interestingly, the PDI was greater than 0.1 and the particle size was greatly increased at a 50 wt% mix. These results suggest that a low molecular weight copolymer is advantageous for mixing the block copolymer into the core.

  Table 1 below summarizes the composition, molecular weight, and molecular weight distribution of the components of the mixed nanoparticles formed above (from the top of Table 1, 2C, 2Cb4C, 4C (long) and 4C (short), respectively).

  Because it is a temperature responsive polymer, the mixed nanoparticles can be easily reconstructed simply by controlling the temperature of the solution. On the other hand, it is necessary to use an organic solution or add chemicals to reconstruct normal self-assembled nanoparticles. FIG. 5 shows a mixture of nanoparticles having different sizes (size / PDI / 4C (long) amount: 74 ± 30 nm / 0.16 / 50 wt% and 33 ± 8 nm / 0.08 shown in FIG. 4B). 4C (long), when the amount of 4C (long) is 0 wt%, the nanoparticles are only 2Cb4C and are the same in FIG. 4 (A) and FIG. Omitted). The total amount of 4C (length) of the entire mixture is 10 wt%. Initially, immediately after mixing both at 40 ° C., two peaks were observed. When the temperature of the solution containing nanoparticles was lowered to 4 ° C., no peak was observed. Subsequently, it was found that by increasing the temperature of the solution to 40 ° C., nanoparticles with narrow PDI (particle size 34 ± 7 nm, PDI 0.07) were reconstructed. This observed size and PDI was consistent with that of mixed nanoparticles containing 10 wt% 4C (long) as shown in FIG. 4 (B).

The nanoparticle mixed core described above consisted of 4C and 2Cb4C of the same composition (ie MEO ₂ MA, OEGMA, ATA and DP). The result leads to the question of whether the copolymer can be mixed with a block copolymer having a different composition and LCST. According to Non-Patent Document 24, polyion complex micelles formed by electrostatic interaction can recognize the chain length of a mixed block copolymer. In the present application, as shown in FIG. 4, not only the chain length but also the LCST is an important factor for the particle structure. Therefore, several types of copolymers with different chain lengths and LCSTs were examined to see if they were suitable for forming the nanoparticles of the present invention. FIG. 6A shows the change in transmittance with respect to temperature of 2Cb4C and 4C (long) mixed at various mixing ratios. The decrease in transmittance due to 4C (long) gradually became stronger as the amount of 2Cb4C was decreased. Another decrease in transmittance around 52 ° C. was due to dehydration of the 2C block. Decreasing the transmittance due to the dehydration of the copolymer 4C by mixing 2Cb4C means that light scattering by the formed aggregate is weak, and nanoparticles are formed. I suggest that. The 2Cb4C repeat unit and LCST were 68/36 (unit) and 60/35 (° C.), respectively. A copolymer having a long chain length (70 units) and a similar LCST (35 ° C.) showed aggregation and precipitation when mixed with 2Cb4C (mixing ratio 1: 1). Interestingly, as shown in FIG. 6C, a copolymer having a short chain length (21 units) and a high LCST of 42 ° C. formed mixed nanoparticles with 2Cb4C (35 ± 7 nm, PDI 0.078). ). There is a 7 ° C. difference in LCST between this copolymer and the 4C block in 2Cb4C. It is known that the dehydration of a temperature-responsive polymer is a continuous behavior and exhibits nanoscale dehydration even at a lower temperature than LCST (Non-patent Document 25). Weak interactions and short chain lengths may lead to highly organized structures. A mixture of 2Cb4C with LCST around 43 ° C. and a copolymer with a long chain length (86 units) showed aggregation / precipitation as the temperature of the solution was increased. These results suggest that the block copolymer may recognize the chain length and LCST of the copolymer mixed therewith (FIG. 5). In fact, mixed nanoparticles may be formed even if there is a difference of 7 degrees between the LCSTs. The formation of mixed nanoparticles is related to the LCST and the chain length of the copolymer. As can be seen from FIG. 6 (C), even if the same LCST was used, mixing was not successful if the chain length (copolymer length) was long. Moreover, hydrophobicity is also expected to play an important role in forming advanced nanoparticles. Copolymers having the same LCST have different hydrophobicity due to their structure (Non-patent Documents 26 and 27).

  In conclusion, nanoparticles with mixed cores composed of separate temperature-responsive copolymers and block copolymers could be made. This block copolymer can take the copolymer hydrophobized by raising the temperature above its LCST to the same extent as its own weight in the core, and the mixed nanoparticles have a particle size of the copolymer to be mixed. The ratio is accurately controlled in the range of 5 nm. The assembled structure could be reconstructed by controlling the temperature of the solution, and the structure was strongly influenced by the chain length and LCST of the copolymer being mixed.

  As described above in detail, according to the present invention, polymer nanoparticles having a wide range of adjustable properties can be easily produced, and there is no intention to limit to this. There are great expectations for biomedical applications such as drug delivery.

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Claims (18)

A temperature-responsive copolymer;
A nanoparticle comprising a plurality of blocks, wherein one block of the plurality of blocks includes a temperature-responsive block copolymer having the same structure as the copolymer.   The plurality of units constituting the one block and the plurality of units constituting the copolymer are the same, but the number of repetitions of each of the plurality of units in the one block and the number of units in the copolymer are the same. The nanoparticle according to claim 1, wherein the number of repetitions of each of the plurality of units is the same or different.   The nanoparticles are composed of a core portion including a portion hydrophobized by raising the temperature of the block copolymer and the copolymer hydrophobized by raising the temperature, and a shell portion other than the core portion. 3. A nanoparticle according to claim 1 or 2 comprising.   The nanoparticle according to claim 3, wherein a weight of the hydrophobized copolymer contained in the core portion is equal to or less than a weight of the block copolymer constituting the nanoparticle. The block copolymer is 2- (2-methoxyethoxy) ethyl methacrylate (abbreviated as MEO ₂ MA), oligo (ethylene glycol) methacrylate (abbreviated as OEGMA), 6-acetylthiohexyl acrylate (abbreviated as ATA). And four monomers of 2- (diisopropylamino) ethyl methacrylate (abbreviated as DP) are polymerized,
A block having a first block having a structure of P (MEO ₂ MA-co-OEGMA) and a second block having a structure of P (MEO ₂ MA-co-OEGMA-co-ATA-co-DP) a polymer _{P (MEO 2 MA-co-} OEGMA) -b-P (MEO 2 MA-co-OEGMA-co-ATA-co-DP),
The copolymer is obtained by polymerizing four types of monomers, MEO ₂ MA, OEGMA, ATA and DP, and the same P (MEO ₂ MA-co-OEGMA-co-ATA-co-) as the second block. DP) is a copolymer having the structure
The nanoparticle according to any one of claims 1 to 4, wherein the monomer corresponds to the unit. The repeating numbers of monomers MEO ₂ MA and OEGMA in the first block of the block copolymer are 48 and 20, respectively.
The repeating numbers of the monomers MEO ₂ MA, OEGMA, ATA and DP in the _second block of the block copolymer are 25, 4, 3 and 4, respectively, and the block copolymer is P (MEO ₂ MA _{48 -co-OEGMA 20)} is expressed as _{-b-P (MEO 2 MA 25} -co-OEGMA 4 -co-ATA 3 -co-DP 4),
The repeating numbers of the monomers MEO ₂ MA, OEGMA, ATA and DP in the copolymer are 17, 2, 3 and 2, respectively 33, 5, 4 and 5 respectively.
The copolymer _{P (MEO 2 MA 17 -co-} OEGMA 2 -co-ATA 3 -co-DP 2) or _{P (MEO 2 MA 33 -co-} OEGMA 5 -co-ATA 4 -co-DP 5) The nanoparticle according to any one of claims 1 to 5, represented by:   The nanoparticle according to any one of claims 1 to 6, which has a functional group at an end of the block copolymer.   The nanoparticle according to claim 7, wherein another substance is bonded to the functional group.   9. Nanoparticles according to claim 8, wherein the other substance is selected from the group consisting of proteins, nucleic acids, enzymes, small molecules, inorganic particles and quantum dots.   The nanoparticle according to claim 8 or 9, wherein the other substance is arranged on the nanoparticle surface.   The copolymer and the block copolymer are decomposed by making the temperature lower than the lower critical solution temperature of the second block in the copolymer and the block copolymer in water. 11. The nanoparticle according to any one of 10.   The nanoparticle according to claim 11, which is formed again by raising the temperature to the lower critical solution temperature or higher.   The nanoparticle according to claim 3 or 4, wherein the core part is gelled, and another substance is encapsulated therein.   14. The nanoparticle according to claim 13, wherein the other substance is selected from the group consisting of pharmaceuticals, enzymes, proteins, nucleic acids, and inorganic particles. A temperature-responsive copolymer;
An aqueous solution comprising a plurality of blocks and one block in the plurality of blocks having a temperature-responsive block copolymer having the same structure as the copolymer includes the copolymer and the block copolymer. A method for producing nanoparticles in which the temperature is raised to the lower critical solution temperature of the one block of coalescence. First nanoparticles produced by the method of claim 15;
The temperature of an aqueous solution produced by the method of claim 15 and containing second nanoparticles having a weight ratio of the copolymer and the block copolymer different from the first nanoparticles is defined as the lower critical solution temperature. The first and second nanoparticles are decomposed into the copolymer and the block copolymer,
After the decomposition, the temperature of the aqueous solution is raised to the lower critical solution temperature or higher to produce third nanoparticles having a weight ratio different from any of the first and second nanoparticles,
A method for producing nanoparticles.   The method for producing nanoparticles according to claim 15 or 16, wherein the aqueous solution further contains a buffer solution.   The method for producing nanoparticles according to claim 15 or 16, wherein a terminal of the block copolymer has a functional group.