JP2009235372A - Dendrimer particle, mri contrast medium, and production method for dendrimer particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an F-MRI contrast medium of high contrast sensitivity with a size controlled severely, a dendrimer particle, and a production method therefor. <P>SOLUTION: This dendrimer particle has a unit containing a fluorine atom in a plurality of branch terminals of an aliphatic branched polymer (dendrimer) of high regularity. The dendrimer particle is produced using an atom transfer radical polymerization method or the like. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluorine-containing dendrimer particle that has high contrast capability and can be used for MRI (hereinafter referred to as F-MRI) using fluorine as a detection nucleus, a contrast agent using the same, and a method for producing a dendrimer particle.

  The development of biological imaging methods using nuclear magnetic resonance (hereinafter referred to as MRI) is remarkable, and it is one of the diagnostic imaging methods along with X-ray diagnosis and ultrasonic diagnosis (US) in both basic research and clinical applications. Widely used.

Currently, MRI generally used for medical use is H-MRI using proton ( ¹ H) as a detection nucleus, and captures and images the magnetic environment of water molecules in a living body. Water molecules exist in almost all areas of the living body, and H-MRI is suitable for whole-body imaging because it can sensitively detect the difference in the magnetic properties of protons due to the difference in the environment surrounding the water molecules. In particular, when there is a difference in magnetic environment between a diseased tissue and a normal tissue, this appears as an image change and becomes disease information, and is used as a diagnostic method with a larger amount of information.

Here, as nuclides that can be detected by MRI, there are ¹⁹ F, ²³ Na, ³¹ P, ¹⁵ N, ¹³ C, etc. in addition to the element whose spin quantum number of the nucleus: I = 1/2, that is, ¹ H, Information different from H-MRI can be obtained. Among them, ¹⁹ F is a stable nuclide that can be detected by NMR spectroscopy, is a low-cost element with a detection sensitivity as high as 83% of ¹ H, and a natural abundance ratio of 100%, and is imaged with a conventional H-MRI apparatus. It has the feature of being possible. Therefore, F-MRI is expected as a next-generation diagnostic method following H-MRI. The most characteristic usage of F-MRI is application to image diagnosis for obtaining tracer information using the feature that fluorine atoms do not exist in the living body. For example, positional information of a lesion can be obtained by recognizing an intrinsic change caused by a disease and using a fluorine compound that accumulates therein as a contrast agent. Such a method is useful for diagnosing lesions that do not cause morphological changes that could not be detected by conventional diagnostic imaging methods.

  At present, in order to obtain such lesion-specific image information, a nuclear medicine technique using a radioisotope such as Positron Emission Tomography: PET or Single Photon Emission Computed Tomography: SPECT must be used. However, many radioisotopes used in nuclear medicine techniques have a short lifetime, and there is a problem that an apparatus for synthesizing the radioisotope itself is large.

  Since the elements constituting the material used in F-MRI are inexpensive stable isotopes, there is no problem in nuclear medicine as described above. Further, by using F-MRI, it is expected that various information such as chemical shift, diffusion and relaxation time can be extracted in addition to positional information, and more diagnostic information can be obtained.

Here, chemical shift is a phenomenon in which the external magnetic field felt by the nucleus changes due to the electron distribution around the nucleus and the resonance frequency slightly shifts. If the state of chemical bonding is different in the same ¹⁹ F nucleus (for example, if the atom or atomic group to which the ¹⁹ F nucleus is bonded is different), the resonance frequency shifts, so the chemical shift is a clue to know the structure of the molecule containing ¹⁹ F. The physical properties that become.

  In addition, the nuclear spins of nuclei excited by irradiation with RF pulses in MRI measurement are initially in phase, but the phases rapidly fall apart due to relaxation, and the vector size rapidly decreases. This is called T2 relaxation. At the same time, some of the spins that were pointing down returned to the upward direction, and the magnitude of the vertical vector slowly recovered. This is T1 relaxation. T1 relaxation is a process in which the longitudinal magnetization vector recovers exponentially with time until the T1 value (T1 relaxation time) returns to 1-1 / e (63.2%) of the original value. Time (time constant). T2 relaxation is a process in which the transverse magnetization vector decreases exponentially with time. On the other hand, the T2 value (T2 relaxation time) is defined as the time (time constant) from the maximum value (initial value) of the signal to decay to 1 / e (36.8%).

  In addition, the diffusion of the molecule to be measured affects the MRI signal intensity. For example, if the diffusion is severe, the phase becomes uneven and the MRI signal intensity is reduced. Therefore, it is possible to obtain information on the Brownian motion of molecules in the tissue from the decrease in MRI signal intensity.

  In addition, F-MRI and H-MRI are simultaneously imaged in a single diagnosis, and by superimposing the respective images, anatomical information (information serving as a coordinate axis in the living body) and functional information (information regarding a lesioned part) ) May provide more useful diagnostic information.

  As research on contrast agents for F-MRI, research using anticancer agents, antibiotics, or fluorinated sugars containing fluorine atoms is disclosed in Non-Patent Documents 1 to 3, Patent Document 1, and the like. These are highly clinically meaningful in that they reflect information on drug efficacy and metabolism in vivo, but the contrast sensitivity is not sufficient, and in order to actually visualize these compounds, large doses and long-time imaging are necessary. Therefore, it has not been applied to actual clinical sites.

  Thus, at present, F-MRI has not reached clinical application. One reason for this is that there is no contrast agent having sufficient sensitivity and performance as described above. Therefore, the development of new contrast agents, particularly improved sensitivity, is required for clinical application.

  In this regard, Patent Documents 2 and 3 present a molecular structure having a fluorine atom and a paramagnetic metal in the same molecule in order to obtain a high contrast capability. Patent Document 4 discloses benzene derivatives having a plurality of trifluoro groups, and Patent Document 5 describes the combined use of these with a paramagnetic metal compound at the time of imaging. Since these compounds have no specificity in in vivo behavior, their clinical usefulness is not clear.

  Other examples of research on contrast agents for F-MRI include those using emulsions of perfluorocarbons (PFC) as shown in Non-Patent Documents 4-6. PFC emulsions have been administered in vivo as artificial blood, and there are few safety concerns. Moreover, since the PFC emulsion has a large number of fluorine atoms, it is most advantageous in contrast sensitivity among existing fluorine compounds. Imaging experiments including vascular and intraretinal systems performed using commercially available PFCs have been reported.

  In addition, the neovascularization is actively performed in the tumor cell part, and this new blood vessel is less dense than the blood vessel of normal tissue, and even a fine particle of a certain size permeates outside the blood vessel. (Enhanced Permeability and Retention: EPR effect) is known. There is also a research example in which imaging of cancer is performed after passively taking PFC emulsion particles into the tumor using this EPR effect (Non-patent Documents 7 and 8).

In F-MRI using a PFC emulsion, the quality of imaging changes basically depending on the pharmacokinetics of fine particles riding on the bloodstream. It is known that there are various barriers in the body in capillaries and retinas, and the kinetics of the body naturally change because the barrier permeability varies depending on the size. Similarly, even if the EPR effect is used, if the particle size of the fine particles is too large, it cannot penetrate the neovascularization of the tumor part, and conversely, if it is too small, normal blood vessels other than the neovascularization of the tumor part It will also pass through the wall, making it impossible to selectively image only the tumor part. In particular, an emulsion is a self-assembly of molecules, the number of molecules accumulated between particles cannot be made exactly the same, and it is difficult to strictly control the particle size.
Japanese Patent Laid-Open No. 11-012295 JP-A-6-181890 JP-A-7-097340 U.S. Pat.No. 5,318,770 US Pat. No. 5,357,724 Mag.Res.Med. 17,189 (1991) Radiology 174,141 (1990) Journal of Japanese Society of Medical Radiology 53 (1), 104-106 (1993) E. McFarland et al., J. Comp. Ass. Tomo. 9, 8 (1985) PMJoseph et al., J. Comp. Ass. Tomo. 9,1012 (1985) HELongmaid et al., Invest. Radiol. 20,141 (1985)) AVRatner et al., Invest.Radiol. 23,361 (1988) RPMason et al., Mag. Res. Imag. 7,475 (1989)

  In view of the background art as described above, an object of the present invention is to provide fluorine atom-containing dendrimer particles whose size is precisely controlled.

  Another object of the present invention is to provide a contrast agent for F-MRI with enhanced contrast sensitivity and size uniformity.

  Furthermore, an object of the present invention is to provide a method for producing fluorine atom-containing dendrimer particles whose size is precisely controlled.

  A first aspect of the present invention is a dendrimer particle having a unit containing a fluorine atom at a plurality of branch ends of an aliphatic highly regular branched polymer (dendrimer).

  The second of the present invention is an MRI contrast agent characterized by containing the dendrimer fine particles.

  A third aspect of the present invention is a method for producing dendrimer particles, comprising a step of providing units containing fluorine atoms at a plurality of branch ends of an aliphatic highly regular branched polymer.

  By using dendrimer particles having a unit containing a fluorine atom at the terminal of the dendrimer, it is possible to provide a contrast agent for F-MRI with high contrast sensitivity and a strictly controlled size.

  In view of the problem of the F-MRI contrast agent, the present inventors have conducted extensive studies on the use of dendrimers, and as a result, have reached the invention of a contrast agent capable of controlling the contrast sensitivity and size.

  First, in order to increase the contrast sensitivity in F-MRI, it is necessary to use a compound having an increased fluorine atom content. In order to increase the content of fluorine atoms, it is possible to use micelles, vesicles or emulsions in which relatively low molecular weight compounds are self-assembled, but in this case, the size can be strictly controlled. Have difficulty. In order to overcome such problems, the present inventors have focused on dendrimers that are polymers (highly regular branched polymers) having a structure in which molecular chains are branched with high regularity.

  Here, the dendrimer is, for example, Hawker, et.al. J. Chem. Soc., Chem. Commun. 1990, (15), 1010-1013., DA Tomalia, et.al. Angew. Chem. Int. Ed. Engl., 29, 138-175 (1990). JMJ Frechet, Science, 263, 1710. (1994), Masaaki Enomoto; Chemistry, 50, 608 (1995), etc. It is a general term for branched polymers having dendritic branches, and such a molecule has a polymer structure that is regularly branched from the center of the molecule, so that, for example, DA Tomalia, et.al.Angew.Chem.Int. As described in Ed. Engl., 29, 138-175 (1990)., It takes a spherical molecular form due to the extreme steric crowding of the branched ends that occur as the molecular weight increases.

  In addition to the advantage that the size can be precisely controlled by its generation, the dendrimer has a feature that the number of structures arranged on the outermost side can be changed regularly. Here, the present inventors have found that by using a large number of partial structures arranged on the outermost side of the dendrimer, the fluorine content can be effectively increased and the size can be strictly controlled. .

  As a dendrimer containing a fluorine atom, JP 2002-220468 A has a substituent containing a fluorine atom in a benzene ring, and JP 2003-226611 A contains a fluorine atom in a siloxane dendrimer. A combination of compounds is disclosed.

  The dendrimer used in the present invention needs to be an aliphatic compound, not an aromatic or siloxane compound, from the viewpoint of biocompatibility and solubility. Therefore, the dendrimer particle of the present invention has a structure in which a unit containing a fluorine atom is bonded to a plurality of branch ends of an aliphatic dendrimer (highly regular branched polymer).

  More specifically, as the aliphatic dendrimer that can be used in the present invention, those having a PAMAM (Polyamidoamine dendrimer) or MPA skeleton can be preferably used. As an example, the following formula (1) shows the molecular structure of a PAMAM dendrimer (generation = 2), and the following formula (2) shows the molecular structure of an MPA dendrimer (generation = 2).

  In particular, in the case of PAMAM, each generation is already on the market, and it is possible to appropriately select the number of surface functional groups (amino groups) and particle size as shown in Table 1 below.

  In Langmuir, 23, 8299-8303, 2007, a study in which the end of the dendrimer was chemically bonded to the substrate and then a fluorine-containing compound was chemically bonded to the end of the dendrimer using carbon dioxide supercritical conditions. A case has been disclosed. The state shown in this research example is a state of being fixed on the substrate by a chemical bond, and cannot be used as a contrast agent that needs to be administered into a living body. In addition, once the dendrimer on the substrate prepared according to the above-mentioned research example is broken into fine particles by cutting the chemical bond between the substrate and the dendrimer, the end of the dendrimer that has been bonded to the substrate has fluorine atoms after cutting. It is expected that the unit containing ss is not coupled, and the contrast sensitivity is lowered accordingly, and the shape deviates from the spherical shape. Furthermore, since the form of chemical bond between the substrate and the dendrimer and the form of chemical bond between the fluorine atom-containing unit and the dendrimer are both amide bonds, the fluorine atom-containing unit is broken when the chemical bond between the substrate and the dendrimer is broken. There is a problem that the chemical bond between dendrimers is also broken in the same manner.

On the other hand, in Japanese Patent Publication Nos. 7-5736 and 7-57735, there is a description about modification of surface functionality such as PAMAM dendrimers, but the use as F-MRI contrast agent and molecules therefor are described. There is no suggestion about the design.
[Dendrimer particles of the present invention]
The dendrimer particle of the present invention is characterized by having a unit containing a fluorine atom at a plurality of branch ends of an aliphatic highly regular branched polymer.

  Here, as the unit containing a fluorine atom, a polymer having a repeating unit containing a fluorine atom can be used.

  Examples of the repeating unit include those represented by the following general formula (1) and those represented by the following general formula (2).

Here, Rf ₁ and Rf ₂ are a linear or branched alkyl group containing a fluorine atom, a linear or branched oxyalkyl group containing a fluorine atom, or a linear chain containing a fluorine atom. Or a monomer or oligomer of an oxyalkylene group which is branched or branched (the hydrogen in these alkyl group, oxyalkyl group and oxyalkylene group may be substituted with an atom or atomic group other than hydrogen, and these alkyl group or —CH ₂ — in the oxyalkyl group may be any one of —O—, —CO—, —NH—, and —COO—. The degree of polymerization of the linear or branched oligomer of a oxyalkylene group containing a fluorine atom is preferably 10 or less.

L ₁ and L ₂ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₁ R ₂ — (R ₁ is hydrogen or an alkyl group, R ₂ is a single bond, A divalent linking group selected from a bond or an alkylene group, a divalent linking group selected from an alkylene group having a hydroxyl group and an oxyalkylene group).

  Examples of the repeating unit not containing a fluorine atom include those represented by the following general formula (1a) and those represented by the following general formula (2a).

Here, Rf ₄ and Rf ₅ are linear or branched alkyl groups that do not contain fluorine atoms, linear or branched oxyalkyl groups that do not contain fluorine atoms, and linear chains that do not contain fluorine atoms. Monomers or oligomers of linear or branched oxyalkylene groups that do not contain a fluorine atom (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups is other than hydrogen) It may be substituted with an atom or an atomic group, and —CH ₂ — in these alkyl groups or oxyalkyl groups is substituted with any of —O—, —CO—, —NH—, and —COO—. Is also good). The degree of polymerization of the linear or branched oxyalkylene group oligomer not containing a fluorine atom is preferably 10 or less.

L ₃ and L ₄ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₃ R ₄ — (R ₃ is a hydrogen or alkyl group, R ₄ is a single bond, A divalent linking group selected from a bond or an alkylene group, a divalent linking group selected from an alkylene group having a hydroxyl group and an oxyalkylene group).

  On the other hand, when a unit other than a polymer is used as the unit containing a fluorine atom, examples thereof include those represented by the following general formula (3).

Here, Rf ₃ represents a linear or branched alkyl group containing a fluorine atom, or a linear or branched oxyalkyl group containing a fluorine atom (these alkyl groups or oxyalkyl groups). The hydrogen in the atom may be substituted with an atom or atomic group other than hydrogen, and —CH ₂ — in these alkyl groups or oxyalkyl groups is —O—, —CO—, —NH—, —COO—. Any of which may be substituted).

L is a single bond, or an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, a phenylene group, an oxyphenylene group, and —NR ₃ R ₄ — (R ₃ is hydrogen or an alkyl group, R ₄ is a single bond. Or a divalent group selected from an alkylene group, a divalent linking group selected from an alkylene group having a hydroxyl group and an oxyalkylene group).

By using a perfluoroalkyl group or oxyperfluoroalkylene group containing a large amount of fluorine as represented by Rf ₃ in the above formula (3), the content of fluorine atoms in the dendrimer particles can be increased. On the other hand, when a perfluoroalkyl group or a perfluoroalkylene group containing a large amount of fluorine is used, the molecular mobility of the fluorine-containing portion is lowered, and the detection sensitivity in F-MRI may be lowered. Therefore, when considering use as an F-MRI contrast agent, it is preferable to appropriately control the fluorine atom content in the group represented by Rf ₃ . More specifically, the fluorine atom content per unit of the perfluoroalkyl group or peroxyfluoroalkylene group is preferably 1 to 50, and more preferably 3 to 30.

  In consideration of the use of the compound according to the present invention as an F-MRI contrast agent, it is preferable to devise to enhance water solubility (more strictly, solubility in body fluids such as blood).

As such a device, introduction of a hydrophilic group into dendrimer particles (preferably near the surface thereof) can be considered. For example, it is conceivable to introduce hydrophilic groups such as —OH, —COOH, —NH ₂ , —O—, and —NH— into the fluorine-containing unit. Such a hydrophilic group can be introduced into the main chain or a side chain when the fluorine-containing unit is a polymer. Further, regarding the examples represented by the general formulas (1) to (3), the hydrophilic group can be introduced into any of L ₁ , Rf ₁ , L ₂ , Rf ₂ , L, and Rf _3. It is. Such a hydrophilic group is more preferably provided at the end of the fluorine-containing unit. It is also conceivable to provide a unit that does not contain fluorine outside the fluorine-containing unit and introduce a hydrophilic group into the unit that does not contain fluorine.

  In consideration of the use as an F-MRI contrast agent, it is desirable to design a molecule in consideration of the degree of solvation of the fluorine atom itself.

  When the compound according to the present invention is used as a tumor-specific F-MRI contrast agent or an inflammatory site-specific F-MRI contrast agent, it is desirable to control the particle size within an appropriate range.

  Specifically, since a large pore having a size of about 10 nm to several hundred nm is opened in a blood vessel of a tumor or an inflamed site, the particle size of the compound according to the present invention may be 10 nm to 200 nm. This is preferable in that it can enter a tumor or an inflamed tissue.

  By setting the particle size to 10 nm or more and 200 nm or less, it is possible to make it difficult for the normal capillary to enter the normal tissue while facilitating the entrance of the tumor or the inflamed site from the blood vessel.

  From the viewpoint of increasing the residence time in the tumor tissue, the particle size is preferably 20 nm or more and 200 nm or less, more preferably 50 nm or more and 100 nm or less.

  On the other hand, from the viewpoint of easy synthesis of the dendrimer, the particle size is preferably 2 nm or more and 100 nm or less.

As a method for controlling the particle size, it is conceivable to appropriately select the generation of the core dendrimer. Moreover, when synthesizing dendrimer particles using a living radical polymerization method described later, the particle size can be easily controlled by controlling the polymerization reaction time.
[Method of producing dendrimer particles]
As a method of providing a unit containing a fluorine atom at the end of the dendrimer, two methods can be exemplified.

  One is a method in which a fluorine atom-containing molecule having a relatively low molecular weight is bonded to the end of the dendrimer by a covalent bond, and the other is a method in which a fluorine atom-containing molecule as a monomer is polymerized from the end of the dendrimer.

In order to distinguish the materials used in these two methods, in the following description, “fluorine atom-containing low molecule” means a fluorine atom-containing molecule as a material to be bonded to the end of the dendrimer without using a polymerization method. The “fluorine atom-containing monomer” means a fluorine atom-containing molecule as a material to be bonded to the end of the dendrimer using a polymerization method.
[Method for bonding fluorine atom-containing small molecule by covalent bond]
In this method, an aliphatic dendrimer is reacted with a molecule containing a fluorine atom represented by the following general formula (6) (fluorine atom-containing low molecule).

Here, Rf ₃ represents a linear or branched alkyl group containing a fluorine atom, or a linear or branched oxyalkyl group containing a fluorine atom. Hydrogen in these alkyl groups or oxyalkyl groups may be substituted with an atom or atomic group other than hydrogen, and —CH ₂ — in these alkyl groups or oxyalkyl groups is —O—, —CO—. , —NH—, or —COO— may be substituted.

As described above, Rf ₃ preferably has a group for enhancing hydrophilicity. For example, an OH group or a COOH group can be provided at the end opposite to L. When a low molecule containing a fluorine atom is bonded to the end of the dendrimer, it is preferable to protect a group such as an OH group or a COOH group with a protective group.

X ₁ is a functional group for forming a covalent bond with the functional group at the end of the dendrimer, and is an amino group, hydroxyl group, carboxyl group, carboxylic acid chloride, carboxylic acid fluoride, halogen atom, epoxy group, isocyanate group, —CH═CH. ₂ , —C≡CH and a thiol group can be mentioned, among which amino group, carboxyl group, hydroxyl group, halogen, carboxylic acid chloride, and carboxylic acid fluoride can be preferably used.

L is a linker for bonding the functional group X ₁ and the fluorine-containing group Rf _3, and is a single bond (substantially no linker is present), an alkylene group, an alkylene group having a hydroxyl group , A phenylene group and an oxyphenylene group. Among them, a single bond, an alkylene group, or a hydroxy group-substituted alkylene group can be suitably used. Particularly, a single bond, or a divalent group selected from —O—, an alkylene group, an alkylene group having a hydroxyl group, and an oxyalkylene group. The linking group is more preferable.

  Specific examples of the fluorine atom-containing low molecule represented by the general formula (6) are shown below, but the present invention is not limited to these exemplified compounds.

  When bonding a fluorine atom-containing low molecule, it is preferable to relatively reduce the number of fluorine atoms in the fluorine atom-containing low molecule for the reasons described above. Therefore, in order to improve contrast sensitivity, that is, to increase the fluorine content per particle, it is effective to increase the number of bonds of fluorine atom-containing low molecules by using a high dendrimer generation as a core.

In order to bond a fluorine atom-containing small molecule to the end of the dendrimer, the end of the dendrimer needs to have a reactive functional group. Examples of such functional groups include amino groups, hydroxyl groups, carboxyl groups, halogen atoms, epoxy groups, isocyanate groups, —CH═CH ₂ , —C≡CH, and thiol groups. Among these, an amino group, a carboxyl group, and a hydroxyl group are preferable from the viewpoint of biocompatibility and ease of synthesis as a dendrimer.

  Further, in order to effectively bind the dendrimer and the fluorine atom-containing low molecule, a low molecular weight spacer having a constant molecular weight may be used. For example, by introducing the following functional group at the end of a dendrimer whose terminal is an amino group, it is possible to have a functional group other than an amino group at the end of the dendrimer.

[Method for polymerizing fluorine atom-containing monomer from dendrimer terminal]
By polymerizing from the end of the dendrimer using a fluorine atom-containing monomer, a polymer having a repeating unit containing a fluorine atom can be provided at the end of the dendrimer.

  By using such a method, the fluorine content in the particles can be easily increased.

  In order to polymerize a reactive monomer containing a fluorine atom, it is possible to bond a functional group suitable as a starting point for the polymerization reaction to the end of the dendrimer.

  As the polymerization method, the living radical polymerization method described below, particularly the atom transfer radical polymerization method, has a wide range of raw material options and facilitates molecular weight control, and precisely controls the particle size of the dendrimer particles. Is preferable in that it can be performed.

  By using this method, it is possible to increase the fluorine atom content in the finally obtained dendrimer particles.

  As the reactive monomer used here, a monomer having a double bond or a triple bond, a substituent such as a carboxyl group capable of condensation polymerization, an amino group or a hydroxyl group, an epoxy group capable of ring-opening polymerization, or an isocyanate group capable of addition polymerization. And thioisocyanate groups. Depending on the polymerization method, the size distribution of the dendrimer particles may be uneven due to the broadening of the molecular weight distribution. From the viewpoint of preventing the occurrence of such a problem, a monomer having a double bond, particularly a monomer having an acrylic group or a methacryl group is preferable.

  For example, an acrylic monomer represented by the following general formula (4) or (5) can be suitably used.

Here, Rf ₁ and Rf ₂ are a linear or branched alkyl group containing a fluorine atom, a linear or branched oxyalkyl group containing a fluorine atom, a straight chain containing a fluorine atom. A chain- or branched oxyalkylene group monomer or oligomer (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups may be substituted with atoms or atomic groups other than hydrogen, and these alkyl groups Alternatively, —CH ₂ — in the oxyalkyl group may be any one of —O—, —CO—, —NH—, and —COO—. The degree of polymerization of the linear or branched oligomer of a oxyalkylene group containing a fluorine atom is preferably 10 or less.
L ₁ and L ₂ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₁ R ₂ — (R ₁ is hydrogen or an alkyl group, R ₂ is a single bond or alkylene; A divalent linking group selected from the group, a divalent linking group selected from an alkylene group having a hydroxyl group and an oxyalkylene group. Specific fluorine atom-containing monomers are exemplified below, but the present invention is not limited to these exemplified compounds. For example, a part of H present in the side chain in the following exemplified compounds may be further substituted with F.

It is possible to introduce a hydrophilic group into the side chain of these monomers. Some of these examples are exemplified above, but for other monomers, the side chain terminal CF ₃ or CHF ₂ is changed to CF ₂ OH or the like, or the side chain is changed to COO (C _m F _2m O ) _N R ₅ (m and n are each an integer of 1 or more, preferably 10 or less, and R ₅ is H or an alkyl group).

  For the polymerization of these monomers, a single type of monomer may be used, or a plurality of types of monomers may be introduced. The introduction of a plurality of monomers may be in the form of random copolymerization in which a plurality of monomers are randomly polymerized or in the form of block copolymerization in which each monomer forms a domain. Furthermore, regarding the method using a plurality of monomers, it is possible to combine a monomer containing a fluorine atom and a monomer not containing a fluorine atom. Depending on the monomer not containing a fluorine atom, the solubility and stability may be different. Functions can be added.

  From the viewpoint of imparting solubility, it is preferable that the monomer that does not contain a fluorine atom that can impart a solubility function is present outside the fluorine atom-containing monomer. For this purpose, it is preferable to polymerize a monomer containing no fluorine atom (preferably having a hydrophilic group) after polymerizing a monomer containing a fluorine atom. By doing in this way, a hydrophilic group can be arranged near the surface of particles.

  As the monomer not containing a fluorine atom, for example, an acrylic monomer represented by the following general formula (4a) or (5a) can be preferably used.

Here, Rf ₄ and Rf ₅ are linear or branched alkyl groups that do not contain fluorine atoms, linear or branched oxyalkyl groups that do not contain fluorine atoms, and linear chains that do not contain fluorine atoms. Monomers or oligomers of linear or branched oxyalkylene groups that do not contain a fluorine atom (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups is other than hydrogen) It may be substituted with an atom or an atomic group, and —CH ₂ — in these alkyl groups or oxyalkyl groups is substituted with any of —O—, —CO—, —NH—, and —COO—. Is also good). The degree of polymerization of the linear or branched oxyalkylene group oligomer not containing a fluorine atom is preferably 10 or less.

L ₃ and L ₄ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₃ R ₄ — (R ₃ is a hydrogen or alkyl group, R ₄ is a single bond, A divalent linking group selected from a bond or an alkylene group, a divalent linking group selected from an alkylene group having a hydroxyl group and an oxyalkylene group).

  As a method for polymerizing these monomers from the end of the dendrimer, a conventionally known polymerization method can be used. In general, in order to obtain a polymer having a narrow molecular weight distribution, it is preferable to use anionic polymerization, cationic polymerization, or a living radical polymerization method as a polymerization method.

  The reason for selecting the former anionic polymerization is that the reaction rate at the time of growth is lower than that at the start of the reaction, and the generated molecular chain tends to have a uniform length.

  In recent years, the latter living radical polymerization has been actively studied. Compared to anionic polymerization, living radical polymerization is a more preferable polymerization method in that the selectivity of the monomer is wide and the reaction conditions can be easily set. This living radical polymerization is based on establishing a quick equilibrium between a small amount of growing radical (free radical) species and a large amount of dormant species in the growth reaction. Various types of living radical polymerization have been proposed with dormant chains.

  For example, an ATRP method (atom transfer radical polymerization method) using an alkyl halide as a dormant, a RAFT method (reversible addition fragment transfer) using a dithioester, an NMP method (nitroxide mediated polymerization) using an alkoxyamine, a dithiocarbamate compound, The optical iniferter method to be used has been proposed.

  The ATRP method is a method of polymerizing a vinyl monomer using a polymerization initiator having a highly reactive carbon-halogen bond and a transition metal complex serving as a polymerization catalyst.

  The RAFT method is a method in which a vinyl monomer is polymerized by adding a chain transfer agent (so-called RAFT agent) having a high chain transfer constant consisting of dithioesters to a normal radical polymerization system.

  The NMP method is a method in which a carbon-oxygen bond of alkoxyamine is thermally cleaved to generate a stable nitroxyl radical and a polymer radical, and a vinyl monomer is polymerized to the polymer radical. Under cleavage, nitroxyl radicals react only with carbon-centered free radicals without initiating polymerization. The polymer radical reacts with the monomer to elongate the molecular chain, and is recombined by a coupling reaction with the nitroxyl radical to stably exist as a dormant species. However, when a methacrylic acid ester derivative is used as a monomer, there is a drawback that a side reaction in which the nitroxyl radical extracts hydrogen at the β-position of the radical carbon generated at the terminal of the polymer is likely to occur.

  The photo-iniferter method uses a photo-iniferter group such as an N, N-diethyldithiocarbamate group as an initiator, and initiates a polymerization reaction by irradiation with ultraviolet rays.

  Any of the above methods may be used for the living radical polymerization in the present invention, and there is no particular limitation, but the ATRP method is preferably used from the viewpoint of a wide selection range of raw materials.

  Next, an outline of the ATRP method will be described.

  The polymerization initiator in the ATRP method is not particularly limited as long as it is a compound having at least one chlorine atom, bromine atom or iodine atom serving as a polymerization initiation point, but usually a chlorine atom, bromine atom or iodine serving as a polymerization initiation point. Compounds with one or two atoms are used.

  Specifically, for example, α-haloesters, α-haloalkylamides, benzyl halides, halogenated alkanes, α-haloketones, α-halonitriles, sulfonyl halides and the like are used, and among these, it is easy to obtain raw materials. From a certain point, α-haloester is preferable.

  Examples of α-haloesters include ethyl 2-bromoisobutyrate or ethyl 2-bromopropionate.

  Examples of α-haloalkylamides include 2-chloropropionamide or 2-bromopropionamide.

  Examples of benzyl halide include 1-phenylethyl chloride and 1-bromoethylbenzene.

  Examples of the halogenated alkane include chloroform and carbon tetrachloride.

  Examples of the α-haloketone include α-bromoacetone and α-bromoacetophenone.

  Examples of α-halonitrile include 2-bromopropionitrile.

  Examples of the sulfonyl chloride include p-toluenesulfonyl bromide.

  In order to achieve the form of the present invention, the monomer polymer needs to be bonded to each end of the dendrimer. As the method, there are two methods: a method in which each terminal of the dendrimer is used as a starting point for the polymerization reaction and monomer polymerization is performed therefrom, and a method in which the monomer is polymerized to a desired length and then bonded to each terminal of the dendrimer. However, in view of reaction controllability, it is preferable to use the former method. Therefore, in the case of performing polymerization using the ATRP method, it is preferable to perform a polymerization reaction with a target monomer after previously binding a polymerization initiator serving as a polymerization initiation point to a dendrimer terminal.

  Although it does not restrict | limit especially as a transition metal complex used as a polymerization catalyst, The metal complex which uses the transition metal (M) chosen from the periodic table group 11-11 group as a center metal can be mentioned. Specific examples thereof include, for example, divalent nickel such as cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide as the copper compound having monovalent copper metal. Examples of nickel compounds include nickel dichloride, nickel dibromide, and nickel diiodide. Examples of iron compounds having divalent iron include divalent ruthenium such as iron dichloride, iron dibromide, and iron diiodide. Examples of the ruthenium compound having a ruthenium dichloride, ruthenium dibromide, and ruthenium diiodide.

  Further, the ligand of the transition metal complex is not particularly limited, but 2,2′-bipyridine and its derivatives (for example, 4,4′-dinonyl-2,2′-bipyridine, 4,4′-di ( 5-nonyl) -2,2′-bipyridine), 1,10-phenanthroline and derivatives thereof (4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10) -Phenanthroline, etc.), tetramethylethylenediamine, pentamethyldiethylenetriamine, hexamethyl (2-aminoethyl) amine and the like.

  Any of the dendrimer particles having the configuration described above can be used as a material for a contrast agent for MRI.

  Although the synthesis | combination and evaluation example of a dendrimer containing a fluorine atom are given to the following, this invention is not limited to these.

Example 1
Poly (2,2,2-trifluoroethyl methacrylate) polyamidoamine dendrimer (PAMAM)
-g-PTFEMA)
[Reaction 1]
Synthesis of 2-bromo-2-methylpropionylbromidated polyamidoamine dendrimer Aminoamine-terminated polyamidoamine dendrimer (manufactured by Aldrich, G = 2) Weighed 5 mL of a 20 wt% methanol solution, and then performed an evaporator treatment at 40 ° C under reduced pressure. The methanol was distilled off. To this was added 5 mL of N, N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was subjected to an evaporator treatment at 90 ° C. under reduced pressure. The solvent was completely distilled off to obtain 791 mg (0.24) of a pale yellow viscous polyamideamine dendrimer. mmol).
H-NMR result of this pale yellow viscous material: H-NMR (d ppm, in D ₂ O) 2.3 (-CH ₂ CH ₂ CONH-), 2.5 (-CH ₂ CH ₂ N <), 2.6 (- CH ₂ CH ₂ NH ₂ ), 2.7 (—NCH ₂ CH ₂ CO—), 3.1-3.2 (—CONHCH ₂ CH ₂ —) (see FIG. 1a).

The obtained polyamidoamine dendrimer was dissolved in 10.7 mL of N, N-dimethylformamide. To this, 550 μL (4.0 mmol) of triethylamine (manufactured by Wako Pure Chemical Industries) and 324 μL (4.0 mmol) of pyridine (manufactured by Aldrich) were added, and the mixture was stirred at 0 ° C. in a nitrogen atmosphere. To this solution, 2.47 mL (0.020 mol) of 2-bromo-2-methylpropionyl bromide (BMPB) (manufactured by Aldrich) was added dropwise, and 27 mL of N, N-dimethylformamide was further added and stirred for 45 minutes. The reaction temperature was returned to room temperature, and after stirring for 2 hours, the reaction was continued in a hot bath at 60 ° C. for 48 hours. After completion of the reaction, an evaporator treatment was performed at 90 ° C., followed by vacuum drying to obtain a brown viscous material. This product was dissolved in methanol, and reprecipitation was performed 3 times using acetone as a solvent. Further, washing with hexane was performed to obtain a white powder. H-NMR result of this white powder: H-NMR (d ppm, in D ₂ O) 1.8 (-COC (CH ₃ ) 2Br), 2.7 (-CH ₂ CH ₂ CONH-), 2.8 (-NCH ₂ CH ₂ CO-), 3.0 (-CH ₂ CH ₂ N <), 3.2-3.3 (-CH ₂ CH ₂ NH ₂ ), 3.5 (-CONHCH ₂ CH _2- ) (see Fig. 1b).

A new signal derived from the methyl proton of BMPB was observed in the H-NMR spectrum, and it was found that a polymerization initiating group was introduced into 14 terminals out of 16 NH ₂ terminals of the polyamidoamine dendrimer.

[Reaction 2]
Synthesis of poly (2, 2, 2-trifluoroethyl methacrylate) polyamidoamine dendrimer 2.67 mg (5.0 × 10 ^-4 mmol) of the product obtained in Reaction 1 was used as a polymerization initiator, and 4,4'-di (5-nonyl) -2,2'-bipyridine (manufactured by Aldrich) 49.9 mg (0.12 mmol), copper (I) chloride as catalyst (made by Wako Pure Chemical Industries) 6.53 mg (0.070 mmol), N, N-dimethyl as solvent Living radical polymerization of 3.53 g (21 mmol) of 2,2,2-trifluoroethyl methacrylate (manufactured by Aldrich) was performed using 508 μL of formamide. The polymerization solution was prepared by mixing these reagents with freeze-pump-thaw using a rotary pump and a diffusion pump for 3 cycles, degassing, and mixing. This solution was distributed in a degassed polymerization tube, and after the sealed tube, a polymerization reaction was carried out in an oil bath at 90 ° C. for 25 minutes. After completion of the polymerization, the obtained product was reprecipitated using methanol as a solvent to obtain a white solid product. H-NMR result of this white solid product: H-NMR (Δppm, in CDCl ₃ ) 4.3 − 4.4 (—COOCH ₂ CF ₃ ), 1.9 − 2.1 (—CH ₂ C (CH ₃ ) −), 0.9 − 1.1 (—CH ₂ C (CH ₃ ) —) (see FIG. 2).

  Further, when the molecular weight of the polymer was confirmed by GPC (gel permeation chromatography), Mn (number average molecular weight) = 120700 g / mol and Mw (weight average molecular weight) = 153500 g / mol.

(Example 2)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 1 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was set to 1 hour. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 168600 g / mol and Mw = 250400 g / mol.

(Example 3)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 1 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was changed to 4 hours. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 421800 g / mol and Mw = 673300 g / mol.

Example 4
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 1 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was changed to 7 hours. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 511500 g / mol and Mw = 673300 g / mol.

(Example 5)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 1 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was changed to 25.5 hours. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 542600 g / mol and Mw = 994900 g / mol. This is hereinafter referred to as PAMAM-g-PTFEMA with Mn = 54 × 10 ⁴ g mol ⁻¹ .

When GPC measurement was performed on the PAMAM-g-PTFEMA obtained in Examples 1 to 5 above, an increase in molecular weight proportional to the polymerization time could be confirmed in the region where the polymerization time was short, and the molecular weight was approximately 5 hours after the polymerization time. (Mn = 550,000 g mol ⁻¹ ) was observed (FIG. 3). In FIG. 3, ● represents Mw, and ○ represents Mw / Mn.

(Example 6: Evaluation of F-NMR)
With respect to the obtained white solid product (PAMAM-g-PTFEMA, polymerization for 25.5 hours: Example 5), an F-NMR spectrum was measured using a 600 MHz NMR apparatus (manufactured by JEOL, JNM-ECA600). The solvent used was CDCl ₃ , and the reference substance was C ₆ H ₅ CF ₃ . The result is shown in FIG. As shown in FIG. 4, a single peak was observed at around -74.5 ppm.

(Example 7: Evaluation of particle morphology)
Product (PAMAM-g-PTFEMA) obtained by polymerization for 25.5 hours using a transmission electron microscope (manufactured by JEOL, JEM-2100F) (Example 5) and product obtained by polymerization for 4 hours (PAMAM- g-PTFEMA) (Example 3) was observed. The result is shown in FIG. PAMAM-g-PTFEMA obtained by polymerization for 25.5 hours and 4 hours was found to have a substantially spherical particle size of about 20 nm, respectively.

(Example 8) Reinitiating reaction of poly (2,2,2-trifluoroethyl methacrylate) polyamidoamine dendrimer PAMAM-g-PTFEMA ( _Mn = 511,500) obtained in Example 4 was used as a polymerization initiator to form a ligand. Bipyridine (manufactured by Aldrich) 1.24 mg (7.9 × 10 ^-3 mmol), copper (I) chloride as catalyst (manufactured by Wako Pure Chemical Industries) 0.39 mg (3.9 × 10 ^-3 mmol), N, N-dimethylformamide as solvent Living radical polymerization of 0.60 mL (4.2 mmol) of 2,2,2-trifluoroethyl methacrylate (manufactured by Aldrich) was performed using mL. The polymerization solution was prepared by mixing these reagents with freeze-pump-thaw using a rotary pump and a diffusion pump for 3 cycles, degassing, and mixing. This solution was distributed into a degassed polymerization tube, and after sealing, 4 hours in an oil bath at 90 ° C. (11 hours in combination with the reaction time of 2,2,2-trifluoroethyl methacrylate in Example 4). Polymerization was performed. After completion of the polymerization, the obtained product was reprecipitated using methanol as a solvent to obtain a white solid product.

  Further, when the molecular weight of this polymer was confirmed by GPC (gel permeation chromatography), it was found that Mn (number average molecular weight) = 602000 g / mol and Mw (weight average molecular weight) = 1050000 g / mol.

Example 9
Similar to Example 8 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was 5 hours (12 hours when combined with the reaction time of 2,2,2-trifluoroethyl methacrylate of Example 4). Thus, a fluorine atom-containing dendrimer was synthesized. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 781000 g / mol and Mw = 1230000 g / mol.

(Example 10)
Similar to Example 8 except that the polymerization reaction time of 2,2,2-trifluoroethyl methacrylate was 7 hours (14 hours when combined with the reaction time of 2,2,2-trifluoroethyl methacrylate of Example 4). Thus, a fluorine atom-containing dendrimer was synthesized. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 797000 g / mol and Mw = 12.70000 g / mol.

When GPC measurement was performed on the products obtained in the TFEMA restarting reaction using PAMAM-g-PTFEMA as a polymerization initiator in Examples 8 to 10 above, it was confirmed that the reaction was further progressing. (FIG. 5).
5 is a plot showing the Mn of the polymer obtained in Examples 1 to 5, and the triangle is the Mn of the polymer obtained by the restarting reaction of Examples 8, 9, and 10. In FIG. In FIG. 5, the horizontal axis represents the reaction time with 2,2,2-trifluoroethyl methacrylate. Regarding the plot of ▲, the reaction time in Example 4 and each of 2,2 in Examples 8, 9, and 10 are shown. It is shown as the sum of the reaction time with 2-trifluoroethyl methacrylate.

Example 11
Synthesis of poly (2,2,3,3-tetrafluoropropyl methacrylate) polyamidoamine dendrimer (PAMAM-g-PTFPMA)
[reaction]
Using 4.01 mg (5.6 × 10 ⁻⁴ mmol) of the product obtained in Reaction 1 of Example 1 as a polymerization initiator, 4,4′-di (5-nonyl) -2,2′-bipyridine (Aldrich) as a ligand. 63.6 mg (0.16 mmol), copper (I) chloride (made by Wako Pure Chemical Industries) as the catalyst, 7.74 mg (0.078 mmol) as the catalyst, and 756 μL of N, N-dimethylformamide as the solvent, 2,2,2-tetra Living radical polymerization of 4.73 g (24 mmol) of fluoropropyl methacrylate (manufactured by Aldrich) was performed. The polymerization solution was prepared by mixing these reagents with freeze-pump-thaw using a rotary pump and a diffusion pump for 3 cycles, degassing, and mixing. This solution was distributed into a degassed polymerization tube, sealed, and then subjected to a polymerization reaction in an oil bath at 90 ° C. for 10 minutes. After completion of the polymerization, the obtained product was reprecipitated using methanol as a solvent to obtain a white solid product.

When the molecular weight of this polymer was confirmed by GPC, it was Mn = 14.6 × 10 ⁴ g mol ⁻¹ and Mw = 18.5 × 10 ⁴ g mol ⁻¹ .

Example 12
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 11 except that the polymerization reaction time of 2,2,3,3-tetrafluoropropyl methacrylate was changed to 20 minutes. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 23.3 × 10 ⁴ g mol ⁻¹ and Mw = 33.8 × 10 ⁴ g mol ⁻¹ .

(Example 13)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 11 except that the polymerization reaction time of 2,2,3,3-tetrafluoropropyl methacrylate was changed to 30 minutes. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 35.4 × 10 ⁴ g mol ⁻¹ and Mw = 50.6 × 10 ⁴ g mol ⁻¹ .

(Example 14)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 11 except that the polymerization reaction time of 2,2,3,3-tetrafluoropropyl methacrylate was 1 hour. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 90.9 × 10 ⁴ g mol ⁻¹ and Mw = 136 × 10 ⁴ g mol ⁻¹ .

(Example 15)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 11 except that the polymerization reaction time of 2,2,3,3-tetrafluoropropyl methacrylate was changed to 2 hours. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 126 × 10 ⁴ g mol ⁻¹ and Mw = 185 × 10 ⁴ g mol ⁻¹ .

(Example 16)
A fluorine atom-containing dendrimer was synthesized in the same manner as in Example 11 except that the polymerization reaction time of 2,2,3,3-tetrafluoropropyl methacrylate was changed to 6 hours. When the molecular weight of this polymer was confirmed by GPC, it was Mn = 143 × 10 ⁴ g mol ⁻¹ and Mw = 187 × 10 ⁴ g mol ⁻¹ .

When GPC measurement was performed on the PAMAM-g-PTFPMA obtained in Examples 11 to 16 above, an increase in molecular weight proportional to the polymerization time could be confirmed in the region where the polymerization time was short, and the molecular weight was approximately 2 hours after the polymerization time. (Mn = 125 × 10 ⁴ g mol ⁻¹ ) was observed (FIG. 7). In FIG. 7, as in FIG. 3, ● represents Mw, and ◯ represents Mw / Mn.

(Example 17)
An F-MRI image of PAMAM-g-PTFEMA with Mn = 54 × 10 ⁴ g mol ⁻¹ obtained in Example 5 was obtained. The results are shown in FIG.

In FIG. 8, a1) to a6) are F-MRI images of trifluorotoluene (TFT: reference material, F atom concentration: 50 mM) as a reference, and b1) to b6) are 54 × 10 ⁴ g mol ⁻¹ PAMAM. It is a F-MRI image of -g-PTFEMA (F atomic concentration: 50 mM). All the solvents are chloroform.

  In the measurement of each sample, as shown in the following table, TR (repetition time) and the number of integrations were fixed as shown in the following table, and TE (echo time) was changed.

  Also, the brightness of the image shown in FIG. 8 is normalized by a1) for a1) to a6) and b1) for b1) to b6), and the brightness of a1) and the brightness of b1) are aligned. .

(Example 18)
With respect to PAMAM-g-PTFEMA having Mn = 54 × 10 ⁴ g mol ⁻¹ obtained in Example 5, the concentration dependency of F-MRI images was examined. The results are shown in FIG.

In FIG. 9, a) is a ¹ H-MRI image, and the schematic diagram shown on the right side of a) is a diagram showing the arrangement of samples. B1) is a ¹⁹ F-MRI image of PAMAM-g-PTFEMA, and b2) is a ¹⁹ F-MRI image of TFT. In the schematic diagram on the right of a) and b1) and b2), the ¹⁹ F-MRI image of PAMAM-g-PTFEMA is a dashed circle, and the ¹⁹ F-MRI image of the reference substance TFT is a solid circle. And enclosed in each. The numbers in the circles indicate the concentration (unit: mM).

  More specifically, the arrangement of the sample in each figure of FIG. 9 is a TFT having an F atom concentration of 0.01 mM in the center, and the other is a TFT having an F atom concentration of 0.1 mM, F, PAMAM-g-PTFEMA having an atomic concentration of 0.01 mM, TFT having an F atomic concentration of 1 mM, PAMAM-g-PTFEMA having an F atomic concentration of 1 mM, and PAMAM-g-PTFEMA having an F atomic concentration of 0.1 mM. All the solvents are chloroform.

Here, b1 ¹⁹ F-MRI image and the ¹⁹ F-MRI image shown in b2) shown in) is one obtained by two signals simultaneous measurement utilizing the difference in resonance frequency between the PAMAM-g-PTFEMA and TFT. The measurement conditions are TR = 1000 ms, TE = 3.8 ms, and 600 integrations.

As is clear from FIG. 9, ¹⁹ F-MRI images were not obtained for TFTs other than 1 mM F atom concentration, whereas PAMAM-g-PTFEMA showed ¹⁹ F-MRI images even at 0.1 mM F atom concentration. It is clearly obtained. From this result, it can be said that PAMAM-g-PTFEMA has excellent sensitivity as a ¹⁹ F-MRI contrast agent.

Example 19
For PAMAM-g-PTFEMA with Mn = 54 × 10 ⁴ g mol ⁻¹ obtained in Example 5, T1 and T2 relaxation times were measured.

Measurement was performed by preparing a chloroform solution in which PnAM-g-PTFEMA of Mn = 54 × 10 ⁴ g mol ⁻¹ and TFT as a reference material were each adjusted to 50 mM with F atom concentration and filled into a 2 mL screw tube. Samples were used. T1 measurement was performed by the inversion recovery method (inversion recovery method), and T2 measurement was performed by the spin echo method (spin echo method). FIG. 10 shows the F-NMR spectrum obtained when measuring the T1 relaxation time by the inversion recovery method. a) is the TFT, b) is the spectrum of PAMAM-g-PTFEMA with Mn = 54 × 10 ⁴ g mol ^-1 , the inversion time is 0.1, 0.25, 0.5, 0.8, 1.4, 2.0, 3.0, 4.0, 8.0 and 15.0 seconds. The results of relaxation time measurement are shown in Table 3 below.

  In MRI, the shorter the T1 relaxation time, the more advantageous it is because the number of integrations can be increased in the same time measurement, and the longer the T2 relaxation time, the sharper the signal peak becomes, and the more advantageous it becomes. . In this PAMAM-g-PTFEMA, both T1 relaxation time and T2 relaxation time were shorter than the standard TFT. Although the signal slightly broadened due to the polymerization and the relaxation time was shortened, as apparent from the F-MRI image of FIG.

It is a H-NMR spectrum of a polyamidoamine dendrimer. a) PAMAM-NH _{2 as} a raw material (before reaction), b) BMPB binding, acetone reprecipitation and hexane washing. It is the H-NMR spectrum of PAMAM-g-PTFEMA. It is a graph which shows the relationship of the polymerization time in the superposition | polymerization of PAMAM-g-PTFEMA, molecular weight (Mn), and molecular weight dispersion | distribution (Mw / Mn). It is an F-NMR spectrum of PAMAM-g-PTFEMA. It is a figure which shows the reaction time and molecular weight (Mn) in the polymerization reinitiation reaction of PAMAM-g-PTFEMA. It is a TEM image of PAMAM-g-PTFEMA, the left is a 25.5 hour polymerization sample, and the right is a 4 hour polymerization sample (both have a scale bar of 10 nm). It is a graph which shows the relationship of the polymerization time in the superposition | polymerization of PAMAM-g-PTFPMA, molecular weight (Mn), and molecular weight dispersion | distribution (Mw / Mn). FIG. 5 is an F-MRI image (evaluation of TE (echo time) dependency) of PAMAM-g-PTFEMA of Mn = 54 × 10 ⁴ g mol ⁻¹ obtained in Example 5 and a reference material TFT. FIG. 6 is an F-MRI image (evaluation of concentration dependency) of PAMAM-g-PTFEMA of Mn = 54 × 10 ⁴ g mol ⁻¹ and a reference material TFT obtained in Example 5. FIG. It is a F-NMR spectrum obtained at the time of T1 relaxation time measurement by the inversion recovery method. (a) A chloroform solution of TFT. (b) A chloroform solution of PAMAM-g-PTFEMA.

Claims (19)

  A dendrimer particle comprising a unit containing a fluorine atom at a plurality of branch ends of an aliphatic highly regular branched polymer.   The dendrimer particle according to claim 1, wherein the unit is a polymer having a repeating unit containing a fluorine atom.   The dendrimer particle according to claim 2, wherein the unit is a polymer composed of a repeating unit containing a fluorine atom and a repeating unit not containing a fluorine atom.   The dendrimer particle according to claim 3, wherein the repeating unit not containing a fluorine atom is present outside the repeating unit containing the fluorine atom. The dendrimer particle according to any one of claims 2 to 4, wherein the repeating unit containing the fluorine atom has a structure represented by the following general formula (1) or (2).
[Wherein Rf ₁ and Rf ₂ are a linear or branched alkyl group containing a fluorine atom, a linear or branched oxyalkyl group containing a fluorine atom, a straight chain containing a fluorine atom, A chain- or branched oxyalkylene group monomer or oligomer (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups may be substituted with atoms or atomic groups other than hydrogen, and these alkyl groups Or —CH ₂ — in the oxyalkyl group may be substituted with any of —O—, —CO—, —NH—, and —COO—.
L ₁ and L ₂ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₁ R ₂ — (R ₁ is hydrogen or an alkyl group, R ₂ is a single bond or Represents a divalent linking group selected from an alkylene group, an alkylene group having a hydroxyl group, and a divalent linking group selected from an oxyalkylene group]. The dendrimer particle according to claim 3 or 4, wherein the repeating unit not containing a fluorine atom has a structure represented by the following general formula (1a) or (2a).
[Wherein Rf ₄ and Rf ₅ are linear or branched alkyl groups containing no fluorine atom, linear or branched oxyalkyl groups containing no fluorine atom, Monomers or oligomers of linear or branched oxyalkylene groups that do not contain fluorine atoms, such as chain or branched oxyalkyl groups (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups is other than hydrogen) Or —CH ₂ — in the alkyl group or oxyalkyl group may be substituted with any of —O—, —CO—, —NH—, and —COO—. Any)
L ₃ and L ₄ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₃ R ₄ — (R ₃ is hydrogen or an alkyl group, R ₄ is a single bond or Represents a divalent linking group selected from an alkylene group, an alkylene group having a hydroxyl group, and a divalent linking group selected from an oxyalkylene group]. The dendrimer particle according to claim 1, wherein the unit containing the fluorine atom is represented by the following general formula (3).
[Wherein Rf ₃ represents a linear or branched alkyl group containing a fluorine atom, or a linear or branched oxyalkyl group containing a fluorine atom (these alkyl groups to oxyalkyl Hydrogen in the group may be substituted with an atom or atomic group other than hydrogen, and —CH ₂ — in these alkyl groups or oxyalkyl groups is —O—, —CO—, —NH—, —COO—. And may be substituted with any of
L is a single bond, or an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, a phenylene group, an oxyphenylene group, and —NR ₃ R ₄ — (R ₃ is hydrogen or an alkyl group, R ₄ is a single bond or alkylene. A divalent group selected from a group, an alkylene group having a hydroxyl group, and a divalent linking group selected from an oxyalkylene group].   The dendrimer particle according to any one of claims 1 to 7, which has a hydrophilic group. The dendrimer particle according to claim 8, wherein the hydrophilic group has at least one of —OH, —COOH, —NH ₂ , —O—, and —NH—.   The dendrimer particle according to any one of claims 1 to 9, wherein a particle diameter is 10 nm or more and 200 nm or less.   A contrast agent for MRI, comprising the dendrimer particle according to claim 1.   A method for producing dendrimer particles, comprising a step of providing units containing fluorine atoms at a plurality of branch ends of an aliphatic highly regular branched polymer.   13. The step of providing a unit containing a fluorine atom is a step of providing a polymer comprising a monomer containing a fluorine atom at a plurality of branch ends of an aliphatic highly regular branched polymer. A method for producing the dendrimer particles according to 1.   The method for producing dendrimer particles according to claim 13, wherein the step of providing the polymer is a step using a living radical polymerization method.   The method for producing dendrimer particles according to claim 14, wherein an atom transfer radical polymerization method is used as the living radical polymerization method. The polymer comprising a monomer not containing a fluorine atom is provided at the end of the polymer comprising a monomer containing a fluorine atom after the step of providing the polymer comprising a monomer containing a fluorine atom. The manufacturing method of the dendrimer particle in any one of 13-15. The method for producing dendrimer particles according to any one of claims 13 to 16, wherein the monomer containing a fluorine atom has a structure represented by the following general formula (4) or (5).
[Wherein Rf ₁ and Rf ₂ contain a linear or branched alkyl group containing a fluorine atom, a linear or branched oxyalkyl group containing a fluorine atom, or a fluorine atom. Monomers or oligomers of linear or branched oxyalkylene groups (the hydrogens in these alkyl groups, oxyalkyl groups, and oxyalkylene groups may be substituted with atoms or atomic groups other than hydrogen, and these alkyls is -O - - -CH ₂ in group or an oxyalkyl group, - CO -, - NH - , - may be substituted with either COO-) indicates one of,
L ₁ and L ₂ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₁ R ₂ — (R ₁ is hydrogen or an alkyl group, R ₂ is a single bond or Represents a divalent linking group selected from an alkylene group, an alkylene group having a hydroxyl group, and a divalent linking group selected from an oxyalkylene group]. The method for producing dendrimer particles according to claim 16, wherein the monomer containing no fluorine atom has a structure represented by the following general formula (4a) or (5a).
[Wherein Rf ₄ and Rf ₅ are linear or branched alkyl groups containing no fluorine atom, linear or branched oxyalkyl groups containing no fluorine atom, Monomers or oligomers of linear or branched oxyalkylene groups that do not contain fluorine atoms, such as chain or branched oxyalkyl groups (the hydrogen in these alkyl groups, oxyalkyl groups, and oxyalkylene groups is other than hydrogen) Or —CH ₂ — in the alkyl group or oxyalkyl group may be substituted with any of —O—, —CO—, —NH—, and —COO—. Any)
L ₃ and L ₄ are a single bond, or —O—, an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, and —NR ₃ R ₄ — (R ₃ is hydrogen or an alkyl group, R ₄ is a single bond or Represents a divalent linking group selected from an alkylene group, an alkylene group having a hydroxyl group, and a divalent linking group selected from an oxyalkylene group]. 13. The step of providing a unit containing a fluorine atom is a step of reacting an aliphatic highly regular branched polymer with a molecule represented by the following general formula (6). Of producing dendrimer particles.
[Wherein Rf ₃ represents a linear or branched alkyl group containing a fluorine atom, or a linear or branched oxyalkyl group containing a fluorine atom (these alkyl groups to oxy Hydrogen in the alkyl group may be substituted with an atom or atomic group other than hydrogen, and —CH ₂ — in these alkyl groups or oxyalkyl groups is —O—, —CO—, —NH—, —COO. -May be substituted with any of-
L is a single bond, or an alkylene group, an alkylene group having a hydroxyl group, an oxyalkylene group, a phenylene group, an oxyphenylene group, and —NR ₃ R ₄ — (R ₃ is hydrogen or an alkyl group, R ₄ is a single bond or alkylene. A divalent group selected from a group, an alkylene group having a hydroxyl group and a divalent linking group selected from an oxyalkylene group),
X ₁ is a group selected from an amino group, a hydroxyl group, a carboxyl group, a carboxylic acid chloride, a carboxylic acid fluoride, a halogen atom, an epoxy group, an isocyanate group, —CH═CH ₂ , —C≡CH, and a thiol group.