[0001]The present invention relates to novel nanoparticles, a contrast agent for magnetic resonance imaging containing the nanoparticles, and a zwitterion ligand compound used for producing the nanoparticles.
Background technology
[0002]Magnetic resonance imaging (MRI) plays an important role in clinical diagnostic imaging and is also an important tool in the field of biomedical research.
[0003]
　The diagnostic imaging method and the contrast medium used therein are techniques used for examination of organs and tissues of a living body. Of these, MRI is a technique for creating elaborate cross-sectional images and three-dimensional images of tissues and organs in a living body using a strong magnetic field and high-frequency radio signals based on the magnetic properties of atoms.
[0004]
　MRI is an effective technique for obtaining two-dimensional or three-dimensional images of all tissues and organs containing water.
[0005]
　When an electromagnetic pulse is incident on magnetically oriented hydrogen nuclei in a tissue of interest, those hydrogen nuclei undergo nuclear magnetic resonance and then return a signal as a result of proton relaxation. Small differences in signals from various tissues allow MRI to identify organs and potentially contrast benign and malignant tissues. MRI is useful for detecting tumors, inflammation, bleeding, edema and the like.
[0006]
　Here, the contrast medium for MRI is changed by mainly shortening the relaxation time (T 1 , T 2 ) of water in the living tissue, and by enhancing the contrast between different tissues, the lesion site is detected or the lesion site is detected. It refers to a drug that enables investigation of blood flow in blood vessels or the function of each organ.
[0007]
　It is desired that the contrast medium for MRI has a property that a contrast effect can be obtained promptly after administration, it does not adversely affect the living body, and the entire amount is excreted. MRI contrast agents can be distributed in blood and extracellular fluid, for example by intravenous administration. Then, the contrast medium half-life in blood is preferably excreted in urine transrenally within 3 hours, more preferably within 2 hours. Contrast media distributed in extracellular fluid are not themselves directly imaged by MRI. Contrast media promotes the relaxation of protons in the surrounding tissue where it is distributed. This is mainly T 1 is referred to as a shortening effect. This effect, contrast agent T 1 exhibits a contrast effect in enhanced image (signal is enhanced). Contrast agents change the relaxation time of the tissue they occupy.
[0008]
　When the contrast agent concentration is higher than a predetermined concentration, T 2 , T 2 * signal by shortening effect is attenuated reversed. Therefore, the optimum density for increasing the signal strength differs depending on the purpose of contrast enhancement.
[0009]
The magnitude of the shortening effect 　of T 1 and T 2 relaxation of the magnetic material , that is, the efficiency of shortening the relaxation time of protons, is expressed as a relaxation rate (R). Here, the relaxation rates R 1 and R 2 are represented by the reciprocals of the vertical relaxation time T 1 and the horizontal relaxation time T 2 of the MRI (R 1 = 1 / T 1 , R 2 = 1 / T 2 ), respectively. The relaxation rate per unit concentration is expressed as relaxation ability (r), the vertical relaxation ability is expressed as r 1 , and the lateral relaxation ability is expressed as r 2 . The R 1 / R 2 ratio and the r 1 / r 2 ratio are used as one of the parameters for evaluating the palliative ability of the contrast medium for MRI.
[0010]
　In particular, those used for the purpose of enhancing the signal on the T 1 weighted image by utilizing the T 1 relaxation are called a T 1 shortened contrast agent or a positive contrast agent. A positive contrast agent causes a signal elevation in the tissue occupied by the contrast medium. A contrast agent used for the purpose of attenuating a signal on a T 2 emphasized image by utilizing T 2 relaxation is called a T 2 shortened contrast agent or a negative contrast agent. Negative contrast media results in signal loss in the tissue occupied by the contrast medium. T 1 weighted MRI and T 2 weighted MRI is an image method used in standard in the diagnosis of medical. T 1 positive contrast agents in weighted MRI, as compared to negative contrast agents, does not occur loss of tissue due to the signal reduction, useful in the diagnosis it is possible to improve the contrast of lesions without missing information in normal tissues It is highly sexual and the use of positive contrast media is essential in diagnostic imaging.

[0011]
　In particular, the r 1 / r 2 ratio of the contrast medium is an important value for the evaluation of the positive contrast medium, and a high r 1 / r 2 as the positive contrast medium results in a T 1 enhanced MR image with good contrast .
[0012]
　Gadolinium (Gd) -based chelate compounds can be used as clinically positive contrast agents, have high r 1 and low r 2 (ie high r 1 / r 2 ) and exhibit excellent T 1 contrast. However, Gd-based compounds are known to be severely toxic to patients with reduced renal excretion, such as the elderly and patients with renal insufficiency.
[0013]
　On the other hand, iron oxides are much less toxic than Gd. Therefore, research and development of iron oxide-based nanoparticles are underway as a material to replace Gd, which is currently the mainstream in the market (Non-Patent Document 1).
[0014]
　So far, nanoparticles for use in medical applications such as diagnostic or therapeutic have been researched and developed. Nanoparticles in which the surface of core particles made of a metal material is coated with various molecules such as polymers are known as one of the configurations of nanoparticles for application to a living body. For example, a method for producing iron oxide particles (ESIONs) having a diameter of 4 nm or less and a positive contrast agent for MRI using nanoparticles coated with polyethylene glycol phosphate (PO-PEG) have been reported (Non-Patent Document 2). .. Further, there have been reports of nanoparticles having a structure in which iron oxide nanoparticles are used as core particles and zwitterionic dopamine sulfonate (ZDS) is bonded to the surface of iron oxide nanoparticles (Non-Patent Document 3 and Patent). Document 1). In addition, the performance when the nanoparticles (ZDS-SPIONs) are used as a positive contrast agent has also been reported (Patent Document 2 and Non-Patent Document 4).
Prior art literature
Patent documents
[0015]
Patent Document 1: International Publication No. WO2013 / 090601 (Published on June 20, 2013)
Patent Document 2: International Publication No. WO2016 / 044068 (Published on March 24, 2016)
Non-patent literature
[0016]
Non-Patent Document 1: Corot et al., Advanced Drug Delivery Reviews, 58, 1471-1504, 2006
Non-Patent Document 2: Byung Hyo Kim et al., J Am. Chem. Sci., 133, 12624-12631, 2011
Non -Patent Document 1: Patent Document 3: He Wei et al., Integr. Biol., 5, 108-114, 2013
Non-Patent Document 4: He Wei et al., Proc. Natr. Acad. Sci., 114 (9), 2325-2330 , 2017
Outline of the invention
Problems to be solved by the invention
[0017]
Conditions 　that it still has excellent positive contrast ability (that is, high r 1 / r 2 ), exhibits stable behavior in vivo, has low toxicity to living organisms, and has good storage stability. New nanoparticles and ligand compounds for coating the nanoparticles are desired. Furthermore, it is necessary to develop a contrast medium for magnetic resonance imaging using the nanoparticles.
Means to solve problems
[0018]
　In order to solve the above problems, the present invention includes any one of the following aspects.
　Unless otherwise specified, when a symbol in a chemical formula in the present specification is also used in another chemical formula, the same symbol has the same meaning.
<1>
　Nanoparticles containing iron oxide-containing metal particles to which one or more zwitterionic ligands represented by the formula (I) are coordinated.
[Chemical

formula 1] (In the formula, one of
R 1 and R 2 is a group represented by the formula (a) or the formula (b), and the other is H, a lower alkyl, an —O- lower alkyl or a halogen. ,
[Chemical formula 2]

X 1 may be a bond or methylene, and X 1 may be ethylene when R 1 is a group represented by the formula (a), and X 2 may be substituted with OH. Good C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene - and R 1
There X when the group represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene--O-C 1-2 alkyl, or Ra and R b combine with the quaternary nitrogen atom to which they are attached to form a 5- or 6-membered nitrogen-containing saturated heterocycle, where
Y − is SO 3 −. , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, -O-C 1-3 alkyl or halogen,
n is an integer of 0 to 2
, and
i) when R 1 is a group represented by the formula (a) and X 1 is methylene, R 2 and Ra or R b are integrated. To form ethylene,
ii) When R 1 is a group represented by the formula (a) and X 1 is ethylene, R 2 and Ra or R b are integrated. Methylene may be formed, and when
iii) R 2 is a group represented by the formula (a) and X 1 is methylene, R 3 and Ra or R b are integrated into ethylene.
May be formed, provided that R 2Is the group represented by the formula (a), Ra and R b are methyl, X 1 is a bond, X 2 is C 1-4 alkylene, and R 1 , R 3 and R 4 when it is both H, Y - is HPO 3 - , or, CO 2 - it is. )
<2>
　A compound represented by the following formula (I) or a salt thereof.
[Chemical

formula 3] (In the formula, one of
R 1 and R 2 is a group represented by the following formula (a) or formula (b), and the other is H, lower alkyl, -O-lower alkyl or halogen. Yes,
[Chemical 4]

X 1 is a bond or methylene, and R When 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 may be substituted with OH C 1-5 alkylene or -C 1-2 alkylene-O. -C 1-3 alkylene -, and further R 1 X when groups are represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1- 3 Alkyl, -C 1-3 alkylene-OC 1-2 Alkyl, or Ra and R b are 5- or 6-membered nitrogen-containing saturated with the quaternary nitrogen atom to which they are attached. form a heterocyclic
ring, Y - is, SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, -O-C 1-3 alkyl or halogen,
n is 0-2 In
addition, when
i) R 1 is a group represented by the formula (a) and X 1 is methylene, R 2 and Ra or R b are integrated to form ethylene. When
ii) R 1 is a group represented by the formula (a) and X 1 is ethylene, R 2 and Ra or R b are integrated to form methylene. Well, and
iii) When R 2 is a group represented by the formula (a) and X 1 is methylene, R 3 and Ra or R b may be integrated to form ethylene,
except that. R 2 is the group represented by the formula (a), R a and R b are methyl, X 1 is a bond, X 2 is C 1-4 alkylene, and R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
The invention's effect
[0019]
　The present invention is expected to have the effect of providing novel nanoparticles having good positive contrast ability and not exhibiting cytotoxicity, and a contrast agent for magnetic resonance imaging containing the nanoparticles.
A brief description of the drawing
[0020]
FIG. 1 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which the contrast medium containing the 3K purified particles of Example 6 was administered. , 1 hour (1hour) and over time T of 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (B) shows the kidneys of mice to which the contrast medium containing the 3K purified particles of Example 6 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (C) shows pre-administration (pre), immediately after administration (post), 0.5 hours (0.5 hours), and 1 hour (0.5 hours) after administration in the bladder of mice to which the contrast medium containing the 3K purified particles of Example 6 was administered. over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements.
FIG. 2 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which the contrast medium containing the 10K purified particles of Example 6 was administered. , 1 hour (1hour) and over time T of 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (B) shows the kidneys of mice to which the contrast medium containing the 10K purified particles of Example 6 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). 1 hour) and 1.5 hours (1.5 hours) of T 1 over time An image of the emphasized MRI measurement result is shown. (C) shows the bladder of the mouse to which the contrast medium containing the 10K purified particles of Example 6 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (c). Images of MRI measurement results over time for 1 hour) and 1.5 hours (1.5 hours) are shown.
FIG. 3 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which the contrast medium containing the 3K purified particles of Example 7 was administered. , 1 hour (1hour) and over time T of 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (B) shows the kidneys of mice to which the contrast medium containing the 3K purified particles of Example 7 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (C) shows the bladder of the mouse to which the contrast medium containing the 3K purified particles of Example 7 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (c). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements.
FIG. 4 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which a contrast medium containing 10K purified particles of Example 7 was administered. T 1 over time for 1, 1 hour (1 hour) and 1.5 hours (1.5 hours) An image of the emphasized MRI measurement result is shown. (B) shows the kidneys of mice to which the contrast medium containing the 10K purified particles of Example 7 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (C) shows the bladder of the mouse to which the contrast medium containing the 10K purified particles of Example 7 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (c). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements.
FIG. 5 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which the contrast medium containing the 3K purified particles of Example 25 was administered. , 1 hour (1hour) and over time T of 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (B) shows the kidneys of mice to which the contrast medium containing the 3K purified particles of Example 25 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (C) shows pre-administration (pre), immediately after administration (post), 0.5 hours (0.5 hours), and 1 hour (0.5 hours) after administration in the bladder of mice to which the contrast medium containing the 3K purified particles of Example 25 was administered. over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements.
FIG. 6 (a) shows pre-administration (pre), immediately after administration (post), and 0.5 hours (0.5 hour) after administration in the liver of mice to which a contrast medium containing 10K purified particles of Example 25 was administered. , 1 hour (1hour) and over time T of 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (B) shows the kidneys of mice to which the contrast medium containing the 10K purified particles of Example 25 was administered before administration (pre), immediately after administration (post), 0.5 hours (0.5 hours) after administration, and 1 hour (b). over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements. (C) shows pre-administration (pre), immediately after administration (post), 0.5 hours (0.5 hours), and 1 hour (0.5 hours) after administration in the bladder of mice to which the contrast medium containing the 10K purified particles of Example 25 was administered. over time T of 1hour) and 1.5 hours (1.5Hour) 1 illustrates an image enhancement MRI measurements.
FIG. 7 shows the magnetic field dependence of the magnetization of the 3K purified particles of Examples 6, 7 and 9 at 300K. It is a graph in which the applied magnetic field is plotted on the horizontal axis and the magnetization per weight is plotted on the vertical axis.
Mode for carrying out the invention
[0021]
　Hereinafter, embodiments of the present invention will be described in detail.
[0022]
　[Definition of terms]
　"Lower alkyl" means linear or branched alkyl having 1 to 6 carbon atoms (hereinafter abbreviated as C 1-6 ), for example, methyl, ethyl, n-propyl, isopropyl, n. -Butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, etc. Another embodiment is C 1-4 alkyl, yet another embodiment is C 1-3 alkyl, yet another embodiment is methyl, ethyl, n-propyl, and yet another embodiment. The embodiment is methyl. Further, one embodiment of "C 1-3 alkyl" is methyl, ethyl or n-propyl, and one embodiment is methyl.
[0023]
　"C 1-5 alkylene" means linear or branched C 1-5 alkylene, such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, propylene, butylene, methylmethylene, ethylethylene, 1,1- Dimethylethylene, 2,2-dimethylethylene, 1,2-dimethylethylene, 1-methylbutylene and the like. One embodiment is C 1-3 alkylene, another embodiment is C 1-2 alkylene, and yet another embodiment is methylene, ethylene, trimethylene, propylene or butylene. The "C 1-5 alkylene" and "C 1-4 alkylene" are C 1-3 or C 1-2 alkylene , respectively , and in some embodiments, methylene or ethylene.
[0024]
　The "5- or 6-membered nitrogen-containing saturated heterocycle" formed by R a and R b integrally with the quaternary nitrogen atom to which they are bonded means that the quaternary nitrogen atom is contained as a ring-constituting atom and has 5 ring members. Or 6 non-aromatic heterocycles, i.e. pyrrolidine or piperidine rings. One embodiment is a pyrrolidine ring containing a quaternary nitrogen atom as a ring-constituting atom.
[0025]
　"Halogen" means F, Cl, Br, and I. Another aspect is F and Cl, yet another aspect is F, and yet another aspect is Cl.
[0026]
　As used herein, the term "nanoparticle" refers to a particle having a particle size of nanometer scale or smaller. A particle having a particle size of less than 100 nm in one embodiment, less than 10 nm in another embodiment, less than 5 nm in yet another embodiment, and less than 3 nm in yet another embodiment. Yet another embodiment refers to particles having a particle size of less than 1 nm. Here, the details of the particle size will be described in the following item of particle size.
[0027]
　As used herein, the term "cluster" refers to an aggregate in which a plurality of identical or different particles are gathered to form a single mass. In one embodiment, it refers to an aggregate of fine metal particles to which a zwitterion ligand is coordinated and a zwitterion ligand.
[0028]
　A "bicyclic ion ligand" or a "bicyclic ion ligand compound" is a compound having a group having both a positive charge and a negative charge in the molecule, and is a group capable of coordinating with a metal atom on the surface of a metal particle. It means a compound used as a particle surface modifier for stably dispersing metal particles in water. In the present specification, the term "twin ion ligand" or "bi-ion ligand compound" is used when the compound is a compound before or after being coordinate-bonded to the surface of metal particles. It means either or both of the cases having a molecular structure.
[0029]
　"Subject" refers to any organism to which the contrast agent for MRI, nanoparticles or compositions comprising nanoparticles of the present invention can be administered, for example, for experimental, diagnostic and / or therapeutic purposes. One example is humans.
[0030]
　Hereinafter, nanoparticles, a contrast agent for MRI, and a zwitterion ligand compound according to the present invention will be described.
[0031]
　[1. Nanoparticles]
　The nanoparticles according to the present invention are nanoparticles containing iron oxide-containing metal particles to which one or more zwitterionic ligands represented by the above formula (I) are coordinated. The embodiment of the zwitterion ligand having a coordination bond will be described in the following sections.
　In one aspect, the nanoparticles according to the present invention are particles formed by coordination-bonding one or more twin ion ligand compounds on the outer surface of metal particles containing iron oxide, and the twin ion ligands. A particle in which the metal particle is coated with a compound.
　In one aspect, the nanoparticles according to the present invention have metal particles in the central portion (core) thereof, and one or more twin ion ligand compounds are coordinate-bonded to the outer surface of the metal particles. , The twin ion ligand compound is a particle having a core-shell structure coated with the metal particle.
　In one aspect, the nanoparticles according to the present invention consist of one or more "metal particles containing iron oxide coordinate-bonded to one or more zwitterionic ligands" and one or more zwitterionic ligand compounds. It is a particle, which is a complex of
　In one aspect, the nanoparticles according to the present invention are composed of two or more twin ion ligand compounds and two or more "metal particles containing iron oxide in which one or more twin ion ligand compounds are coordinated and bonded". It is a particle, which is a cluster.
　In one aspect, the nanoparticles according to the present invention are defined as two or more twin ion ligand compounds and two or more "metal particles containing iron oxide in which one or more twin ion ligand compounds are coordinated and bonded". Are particles, which are irregularly connected clusters.
[0032]
　If the nanoparticles are coordinate-bonded with the zwitterion ligand compound of the present invention, the nanoparticles are prevented from aggregating with each other, and the particle properties are stable even in a solution containing the nanoparticles at a high concentration, for example. With such nanoparticles, to ensure low saturation magnetization, T of clear contrast 1 it is possible to obtain an enhanced image, because renal excretion is facilitated can be expected to exhibit good renal clearance.
[0033]
　(Metal particles)
　Metal particles contain iron oxide. In one embodiment, the metal particles are iron oxide particles containing only iron oxide, and as another example, the metal particles are metal particles containing iron in addition to iron oxide. The "metal particles" in the specification of the present application refer to "iron oxide nanoparticles" in "iron oxide nanoparticles in which a hydrophobic ligand is coordinated and bonded to the surface" as a raw material, and the biionic ligand of the present invention as metal particles. It includes "iron oxide-containing metal particles" in which some changes have occurred from the raw material iron oxide nanoparticles as a result of carrying out a production method for coordinating and bonding, for example, the MEAA method described later. Here, some changes include, but are not limited to, structural changes from core-shell structures to complexes and clusters, changes in particle size, changes in composition, and the like. That is, the "metal particles" in the present specification are at least the MEAA method, which is a production method for coordinating the biionic ligand represented by the formula (I) described in the present specification to the metal particles, and the TMA (OH) described later. ) And all metal particles containing iron oxide obtained by the phase transfer catalyst method.
[0034]
　In one embodiment, the iron oxide-containing metal particles may further contain at least one metal derivative other than iron oxide. Further, the metal particles may further contain at least one kind of metal element other than iron (Fe). As another metallic element, at least one selected from the group consisting of gadolinium (Gd), manganese (Mn), cobalt (Co), nickel (Ni) and zinc (Zn) is optionally selected. Further can be included.
[0035]
　In yet another embodiment, the metal particles may consist solely of iron oxide or may contain ferrite derived from iron oxide. Ferrite is an oxide of formula MFe 2 O 4 , where M is a transition metal preferably selected from Zn, Co, Mn and Ni.
[0036]
　A material known as Super Paramagnetic Iron Oxide (SPIO) is also preferably used. These materials are represented by the general formula [Fe 2 O 3 ] x [Fe 2 O 3 (M 2 + O)] 1-x (x = 0 or 1 in the formula). M may be, for example, Fe, Mn, Ni, Co, Zn, magnesium (Mg), copper (Cu), or a combination thereof. When the metal ion (M 2+ ) is ferrous ion (Fe 2+ ) and x = 0, the material is magnetite (Fe 3 O 4 ), and when x = 1, the material is mug hemite (Fe 3 O 4 ). γ-Fe 2 O 3 ).
[0037]
　In one embodiment, the iron oxide is magnetic iron oxide and can be magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), or a mixture thereof. Such metal particles made of magnetic iron oxide become superparamagnetic nanoparticles.
[0038]
　In yet another embodiment, if the iron oxide particles contain at least one derivative of a metal element other than iron, each derivative of the metal element may be a different type of derivative. That is, the iron oxide particles may contain oxides, nitrides and the like. In another embodiment, the core particles may contain iron derivatives other than iron oxide (eg, FePt and FeB) that have iron elements other than iron oxide.
[0039]
　The metal particles according to one embodiment may be manufactured by a known method such as the methods described in the above-mentioned Patent Document 1, Non-Patent Document 2, Non-Patent Document 3, etc., and may be commercially available. There may be. For example, it may be iron oxide particles produced by a coprecipitation method or a reduction method.
[0040]
　(Particle size of metal particles) In
　this specification, the term particle size means the average particle size unless otherwise specified.
[0041]
　The "particle size" of a metal particle is intended, for example, to be the diameter of the maximum inscribed circle with respect to the two-dimensional shape of the particle when the particle is observed with a transmission electron microscope (TEM). For example, if the two-dimensional shape of a particle is substantially circular, the diameter of that circle is intended. Further, when the shape is substantially elliptical, the minor axis of the ellipse is intended. Further, when it is substantially square, the length of the side of the square is intended, and when it is substantially rectangular, the length of the short side of the rectangle is intended.
[0042]
　As a method of confirming that the average particle size has a value in a predetermined range, for example, 100 particles are observed with a transmission electron microscope (TEM), the particle size of each particle is measured, and 100 particles are used. This can be done by finding the average value of the particle diameters of the particles of.
[0043]
　The particle size of the metal particles (including the case where it is the average diameter of clusters or complexes containing metal particles) according to one embodiment is preferably 5 nm or less and 4 nm or less when measured by TEM. Is more preferably 3 nm or less, further preferably 2 nm or less, and most preferably 1 nm or less. If the particle size is 2 nm or less, it is more useful as a positive contrast agent for high magnetic field MRI of 3 tesla (T) or more.
[0044]
　Further, if the particle size is 2 nm or less, preferably 1 nm or less, a higher signal-to-noise ratio can be obtained when used in a high magnetic field MRI of 7 T or more, so that higher spatial resolution and measurement in a short time can be realized. There is sex.
[0045]
　In one embodiment, the population of nanoparticles contained in the MRI contrast agent is preferably as uniform as possible in the properties of the nanoparticles. Therefore, it is preferable that the metal particles, which are the core of the nanoparticles, have a uniform size and shape. As an example, metal particles have uniformity within the range of their average particle size ± 1 nm. As another example, it has a uniformity within the range of an average particle size of ± 0.5 nm.
[0046]
　In another embodiment, as the nanoparticles contained in the contrast medium for MRI, it is preferable that a large number of small particles are contained as the contained metal particles. As an example, the number of metal particles having a diameter of 3 nm or more is 30% or less of the total, preferably 10% or less of the total, and more preferably 5% or less of the total. As another example, the number of particles having a diameter of 2 nm or more is 30% or less of the total, preferably 10% or less of the total, and more preferably 5% or less of the total. As yet another example, the number of particles having a diameter of 1 nm or more is 30% or less of the total, preferably 10% or less of the total, and more preferably 5% or less of the total.
[0047]
　In yet another embodiment, the population of nanoparticles contained in the MRI contrast agent may have non-uniform characteristics of each particle, so that the metal particles to which the zwitterionic ligand is coordinated are non-uniform. It may have a uniform size and shape. As an example, the metal particles may include particles having a size different from the average particle size of 1 nm or more.
[0048]
　(Particle size of
　nanoparticles ) It is estimated that the particle size of nanoparticles is increased by the thickness of the zwitterion ligand that is coordinate-bonded to the surface of the metal particles. Usually, the hydrodynamic diameter (HD) when nanoparticles are used as a solution is used as an index of the size. As an example, the average HD of nanoparticles is 10 nm or less, preferably 8 nm or less. As yet another example, the average HD of nanoparticles is 5 nm or less, preferably 4 nm or less, preferably 3 nm or less, preferably 2 nm or less, still more preferably 1 nm or less.
[0049]
　HD of nanoparticles can be performed, for example, by observing the particles by the small-angle X-ray scattering method (SAXS) and obtaining the average value of the particle diameters.
　Commercially available equipment may be used for the measurement of SAXS, and it is preferable to use a synchrotron radiation facility such as SPring-8 (BL19B2) or Aichi Synchrotron Optical Center. For example, when SPring-8 (BL19B2) is used, the camera length is set to 3 m, the sample is irradiated with X-rays of 18 KeV, and the wave number q is observed in the range of about 0.06 to 3 nm -1 .
[0050]
　In the case of a dispersion liquid sample, put it in a capillary with a diameter of 2 mm, set the exposure time appropriately so that the scattered radiation does not saturate, and obtain scattered data. The scattered data can be fitted by Guinier analysis or using appropriate SAXS analysis software to obtain an average particle size.
[0051]
　Further, as a method for measuring the relative size of nanoparticles, for example, Size Exclusion Chromatography (SEC) can be used.
[0052]
　SEC is an analytical method in which a sample is poured on a column packed with a carrier having pores, and the size of the sample is estimated by the time until it flows out. Large agglomerates flow out quickly because they do not enter the pores of the carrier, and small nanoparticles pass through the pores of the carrier, so the route to flow out becomes long and flows out slowly. The relative size of the particles can be measured.
[0053]
　[2. Zwitterion ligand compound]
　The zwitterion ligand compound according to the present invention is a compound represented by the following formula (I) or a salt thereof.
[Chemical

formula 5] (In the formula, one of
R 1 and R 2 is a group represented by the formula (a) or the formula (b), and the other is H, a lower alkyl, an —O- lower alkyl or a halogen. ,
[Chemical formula 6]

X 1 may be a bond or methylene, and X 1 may be ethylene when R 1 is a group represented by the formula (a), and X 2 may be substituted with OH. When a good C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene - and R 1 is a group represented by the formula (b), X 2 may be a bond. , R A and R

b is the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are quaternary nitrogen atoms to which they are attached. and to form a 5- or 6-membered nitrogen-containing saturated heterocyclic ring
together, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other , H, C 1-3 alkyl, -OC 1-3 alkyl or halogen,
n is an integer of 0 to 2
, and
i) R 1 is the group represented by the formula (a). And X 1When is methylene, R 2 and Ra or R b may be integrated to form ethylene,
ii) R 1 is a group represented by the formula (a), and X 1 is ethylene. When, R 2 and Ra or R b may be integrated to form methylene, and
iii) R 2 is a group represented by the formula (a), and X 1 is methylene. At some point, R 3 and Ra or R b may be integrated to form ethylene,
where R 2 is the group represented by formula (a) and R a and R b are methyl. , X 1 is a bond and X 2There, C 1-4 alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
[0054]
　In one embodiment, one of R 1 and R 2 is the group represented by the formula (a) and the other is a zwitterionic ligand which is H, lower alkyl, —O-lower alkyl or halogen.
[0055]
　In one embodiment, the zwitterionic ligand compound according to the present invention is a compound represented by the following formula (o).
[0056]
[Chemical

　formula 7] (The symbols in the formula are the same as those in the above formula (I).) In
　one embodiment of the compound represented by the formula (o), R 2 is H, a lower alkyl, and an —O— lower alkyl. Alternatively, it is a zwitterionic ligand, which is halogen, and in another embodiment, when R 2 is H or halogen and X 1 is bound, methylene or ethylene, or X 1 is methylene, then R 2 And R a or R b may be integrated to form ethylene, X 2 is C 2-4 alkylene, Ra and R b are both methyl, and R 3 and R 4 are formed. Are zwitterionic ligands that are the same or different from each other and are H, C 1-3 alkyl or halogen, and in yet another embodiment, R 2 is H or halogen and X. When 1 is bonded or methylene, or when X 1 is methylene, R 2 and Ra or R b may be integrated to form ethylene, where X 2 is C 2-4 alkylene. Yet another embodiment in which R a and R b are both methyl and R 3 and R 4 are the same or different from each other and are H, C 1-3 alkyl or halogen, a diionic ligand. R 2 is H or F, X 1 is bound, methylene or ethylene, X 2 is ethylene or propylene, Ra and R b are both methyl, and R 3 and R 4Are zwitterionic ligands, both of which are H, and in yet another embodiment, R 2 is H, X 1 is ethylene, X 2 is ethylene or propylene, and Ra and R b. Is a zwitterionic ligand in which both are methyl and R 3 and R 4 are both H, and in yet another embodiment, R 2 is H or F and X 1 is bound or Ethylene, X 2 is an ethylene group or a propylene group, Ra and R b are both methyl, R 3 and R 4 are both H, and Y − is SO 3 − or. CO 2 - is a zwitterionic ligands, as yet another embodiment, R 2 is H or F, X 1 is methylene, X 2 is a propylene or butylene group, Ra and R b are both methyl, and R 3 and R 4 are both H. and, Y - is SO 3 - , HPO 3 - , or, CO 2 - is a zwitterionic ligands, in a further embodiment, R 2 is is H or F, X 1 is methylene Yes, X 2 is a propylene group or a butylene group, Ra and R b are both methyl, R 3 and R 4 are both H, and Y −There SO 3 - is a zwitterionic ligands.
　One embodiment is a zwitterionic ligand represented by the following formula (1).
[0057]
[Chemical

formula 8] (The symbol Y - in the formula is the same as that in the formula (I).)
[0058]
　Another embodiment is a zwitterionic ligand represented by the following formula (2).
[Chemical

formula 9] (The symbol Y - in the formula is the same as that in the formula (I).)
[0059]
　Another embodiment is a zwitterionic ligand represented by the following formula (3).
[Chemical

formula 10] (The symbol Y - in the formula is the same as that in the formula (I).)
[0060]
　Another embodiment is a zwitterionic ligand represented by the following formula (4).
[Chemical

formula 11] (The symbol Y - in the formula is the same as that in the formula (I).)
[0061]
　Another embodiment is a zwitterionic ligand represented by the following formula (5).
[Chemical

formula 12] (The symbol Y - in the formula is the same as that in the formula (I).)
[0062]
　In another embodiment, the zwitterionic ligand compound according to the present invention is a compound represented by the following formula (6).
[0063]
[Chemical

　formula 13] (The symbols in the formula are the same as those in the above formula (I).)
　One embodiment is a zwitterionic ligand represented by the following formula (7).
[0064]
[Chemical

formula 14] (The symbol Y - in the formula is the same as that in the formula (I).)
[0065]
In one embodiment of the zwitterionic ligand compound, one of R 1 and R 2 in the above formula (I) is a group represented by the following formula (b-1), and the other is H, a lower alkyl,-. A zwitterionic ligand that is an O-lower alkyl or halogen.
[Chemical

　formula 15] (The symbols in the formula are the same as those in formula (I).)
[0066]
　In one embodiment, the zwitterionic ligand compound according to the present invention is a compound represented by the following formula (8).
[0067]
[Chemical

　formula 16] (The symbols in the formula are the same as those in the above formula (I).) In
　one embodiment of the compound represented by the formula (8), R 2 is H, a lower alkyl, and an —O— lower alkyl. Alternatively, it is a diionic ligand that is a halogen, and in another embodiment, R 2 is H or halogen, X 1 is bound or methylene, X 2 is bound or C 1-3 alkylene, and R. A diionic ligand in which a is methyl and R 3 and R 4 are the same or different from each other and are H, C 1-3 alkyl or halogen, and in yet another embodiment, R 2 is H or F, X 1 is methylene, X 2 is bound or methylene, Ra is methyl, and R 3 and R 4 are both H and Y. - is SO 3 - , HPO 3 - , or, CO 2 - is a zwitterionic ligands, in a further embodiment, R 2 is is H or F, X 1 is methylene, X 2 a There bond or methylene, R a is methyl, and, R 3 and R 4 both are H, and, Y - is CO 2 - is a zwitterionic ligands, or even another In embodiments, R 2 is H or halogen, X 1 is bond or methylene, X 2 is C 1-5 alkylene or bond, Ra is methyl, and R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, or halogen, and, Y - is SO 3 - , or, CO 2 - is a zwitterionic ligands.
[0068]
　Another embodiment is a zwitterionic ligand represented by the following formula (9).
[Chemical

　formula 17] (The symbol Y - in the formula is the same as that of the above formula (I).)
[0069]
　Another embodiment is a zwitterionic ligand represented by the following formula (10).
[Chemical

　formula 18] (The symbol Y - in the formula is the same as that of the above formula (I).)
[0070]
　The nanoparticles according to the present invention are nanoparticles containing metal particles containing iron oxide, to which one or more zwitterionic ligands represented by the above formula (I) are coordinated and bonded, and the above-mentioned [2. The nanoparticles containing the iron oxide-containing metal particles to which the zwitterion ligand compounds of the respective embodiments described in [Zwitterion Ligand Compound] are coordinated and bonded are the nanoparticles of the nanoparticles of the present invention, respectively. be. When the twin ion ligand is coordinate-bonded to a metal particle containing iron or iron oxide, the oxygen of the two hydroxyl groups of the twin ion ligand compound is coordinate-bonded with the metal atom on the surface of the metal particle, and the present invention To form nanoparticles.
[0071]
　Further, the present invention also includes the use of the zwitterion ligand compound for producing the nanoparticles of the present invention, and the zwitterion ligand compound itself. The above [2. The zwitterionic ligand compound] is also an embodiment of the zwitterionic ligand compound in these inventions.
[0072]
　In the zwitterionic ligand of the present invention, the trisubstituted amino group is substituted with catechol directly or via an alkylene group to form an ammonium cation. The zwitterionic ligand of the present invention has a shorter molecular chain and can have a thinner ligand layer than a conventionally known ligand. Moreover, it is characterized by having a positive charge on the metal particle side and a negative charge on the outer surface side, whereby the nanoparticles of the present invention are expected to exhibit high stability because the particles are less likely to aggregate in the body fluid. Will be done. Further, since the ligand layer is thin, the distance from the metal atom becomes short, and it is expected that excellent imaging ability due to an increase in the number of water molecules affected by the metal particles and the like is exhibited.
[0073]
　The number of molecules of the zwitterion ligand coordinated on the surface of the metal particles (the number of zwitterion ligands) varies depending on the size and surface area of ​​the metal particles. One embodiment has 2 to 200 metal particles, another embodiment has 5 to 50 particles, and yet another embodiment has 5 to 20 particles.
[0074]
　(Compound that binds to metal particles other than the twin ion ligand)
　The nanoparticles of the present invention may contain other than the twin ion ligand of the present invention, and in one embodiment, the metal particles themselves have fluorescent characteristics. Or may further contain molecules such as fluorescent molecules or dye molecules bound to the surface of the metal particles. The nanoparticles themselves can have fluorescent properties, or by introducing fluorescent or dye molecules into the nanoparticles, the nanoparticles can be used not only as a contrast agent for MRI, but also as an optical image contrast agent at the same time. can. In another embodiment, the fluorescent molecule or dye molecule may be a ligand covalently bound to the zwitterion ligand of the present invention, and the molecule is linked to the iron oxide particles via the zwitterion ligand. .. Even after the nanoparticles have been injected into the body, the fluorescent molecules are present on the surface of the iron oxide particles and can be used for microscopic imaging as well as for investigating the localization of the nanoparticles. Fluorescent and dye molecules include rhodamine, fluorescein, nitrobenzoxadiazole (NBD), cyanine, green fluorescent protein (GFP), coumarin and derivatives thereof.
[0075]
　Further, in another embodiment, it may have at least one substance bonded to the surface of the metal particle, and may be a peptide, a nucleic acid, a small molecule, or the like, without limitation. For example, it is possible to impart a therapeutic effect on a tumor by binding a peptide having a property of specifically producing a therapeutic effect on the tumor to the nanoparticles of the present invention.
[0076]
　Further, a ligand other than the zwitterionic ligand of the present invention may be bound to the surface of the metal particles. For example, it is also possible to impart tumor-selective binding property by binding a ligand having a property of specifically accumulating in a tumor to the metal particles of the present invention.
[0077]
　It is preferable to impart such tissue specificity to the contrast medium in order to strengthen the signal at the site to be measured by MRI and to obtain information on a specific pathological condition or the like. The distribution of contrast media in vivo depends on particle size, charge, surface chemistry, route of administration and route of excretion.
[0078]
　Further, since the nanoparticles of the present invention contain iron oxide as metal particles, they are expected to have low toxicity to the living body. Therefore, it is expected that the safety is excellent and there are few restrictions on various uses.
[0079]
　[3. Method for producing zwitterionic ligand]
　The method for producing the zwitterionic ligand of the formula (I) of the present invention is not particularly limited, and it can be easily produced from a known raw material compound using a reaction well known to those skilled in the art. For example, the methods described in Wei H. et al., Nano Lett. 12, 22-25, 2012 can be referred to.
[0080]
　In one example, the synthetic method described in Production Example is preferably used.
[0081]
　[4. Nanoparticle manufacturing method]
　Next, a nanoparticle manufacturing method will be described.
　(Production of Metal Particles Coordinated to a
　Hydrophobic Ligand or Hydrophilic Ligand as a Raw Material ) Production of Nanoparticles For metal particles to which a hydrophobic ligand or a hydrophilic ligand is coordinated to be a raw material, a known method is used. Can be manufactured. For example, the methods described in Byung Hyo Kim et al., J Am. Chem. Soc. 2011, 133, 12624-12631, and Byung Hyo Kim et al., J Am. Chem. Soc. 2013, 135, 2407-2410. Can be done with reference to.
[0082]
　For example, (a) a metal salt is reacted with an alkali metal salt of a fatty acid to form a metal fatty acid complex, and (b) the complex is rapidly heated to a high temperature of 200 ° C. or higher together with a surfactant, if desired. By reacting at a high temperature for a certain period of time, metal particles whose surface is coated with a hydrophobic ligand can be synthesized. Further, (c) the metal particles coated with the hydrophobic ligand are coated with [2- (2-methoxyethoxy) ethoxy] acetic acid (MEAA). It is possible to obtain metal particles coated with MEAA that can be dispersed in a highly polar solvent.
　Hereinafter, each step will be described in detail.
[0083]
　(Step (a)) A
　metal salt and an alkali metal salt of a fatty acid are dispersed in a solvent. Examples of the above metal salts, iron (III) chloride hexahydrate (FeCl 3 · 6H 2 O). Examples of the alkali metal salts of fatty acids, sodium oleate, as the solvent ethanol, water, hexane, And mixtures thereof. Subsequently, under heating, the mixture is stirred at preferably 70 ° C. for 1 to 10 hours, preferably 3 to 4 hours to recover the organic layer, and the organic layer is washed with water one to multiple times, more preferably 3. Repeat up to 4 times to obtain a metal fatty acid complex. The resulting organic layer is dried if desired.
[0084]
　(Step (b)) The
　complex obtained in step (a) is selected from the group consisting of fatty acids, aliphatic alcohols and aliphatic amines under an inert gas atmosphere selected from, for example, argon (Ar) and nitrogen. At least one surfactant and a solvent selected from diphenyl ether and phenyl octyl ether are added. As an example, the surfactant is oleic acid, oleyl alcohol, oleyl amine or a mixture thereof, and the solvent is diphenyl ether. Next, the mixture is rapidly heated from room temperature to 180 to 300 ° C., and if desired, stirred as it is for 10 minutes to several hours. As an example, the temperature is raised from 30 ° C. to 250 ° C. at 10 ° C./min, and the mixture is stirred at 250 ° C. for 30 minutes. As another example, the temperature is raised from 30 ° C. to 200 ° C. at 10 ° C./min, and the mixture is stirred at 200 ° C. for 30 minutes.
[0085]
　After lowering the temperature of the reaction solution to room temperature, acetone is added and the supernatant is removed by centrifugation. This operation is repeated 2-3 times, preferably 4-5 times. If desired, the resulting solution may be dried. As an example, the operation of adding acetone and centrifuging the supernatant is repeated three times to obtain metal particles whose surface is coated with a hydrophobic ligand such as oleic acid.
[0086]
　(Step (c)) In
　an inert gas atmosphere selected from Ar and nitrogen, nanoparticles coated with a hydrophobic ligand are dispersed in a solvent, and then MEAA is added and reacted. Methanol is suitable as the solvent.
[0087]
　The reaction is carried out by stirring at room temperature or warming, preferably at 25 to 80 ° C. for about 1 to 15 hours, preferably for 5 to 10 hours, for example, by stirring at 50 ° C. for 7 hours. As another example, it is carried out by stirring at 70 ° C. for 10 hours, and as another example, it is carried out by stirring at 70 ° C. for 5 hours.
[0088]
　After lowering the temperature of the reaction solution to room temperature, a solvent selected from acetone and hexane is added and centrifuged to remove the supernatant. This operation may be repeated 2-3 times, preferably 4-5 times. The resulting solution may be dried. As an example, the above operation is repeated three times to obtain metal particles whose surface is coated with MEAA.
[0089]
(Method for Producing
　Nanoparticles of the Present Invention) The "nanoparticles containing metal particles containing iron oxide in which one or more biionic ligands are coordinated and bonded" is a metal whose surface is coated with a known MEAA. It can be produced by using a method via particles (MEAA method), a method using TMA (OH) (TMA (OH) method), or a novel synthesis method using an interphase transfer catalyst.
A) MEAA method
　This production method is a method for obtaining the nanoparticles of the present invention by reacting the metal particles whose surface is coated with MEAA with the zwitterionic ligand compound of the present invention. The reaction involves the metal particles whose surface is coated with MEAA and the zwitterionic ligand compound of the present invention in an inert gas atmosphere selected from Ar and nitrogen for 1 to several tens of hours at room temperature or heating. This is done by stirring. As an example, it is performed in an Ar atmosphere. The reaction temperature is 25 to 80 ° C. as an example and 50 to 70 ° C. as another example. The stirring time is 5 to 7 hours as an example and 24 hours as another example. As an example, stir overnight at room temperature. Subsequently, the temperature of the reaction solution is lowered to room temperature, a solvent is added and the mixture is centrifuged, and the supernatant is removed to obtain nanoparticles in which one or more zwitterionic ligand compounds of the present invention are coordinated. The solvent is not particularly limited, but is selected from acetone, hexane and the like. Acetone is used as an example. Further, the operation of adding the solvent, centrifuging and removing the supernatant may be repeated a plurality of times, for example, 4 to 5 times. As an example, this operation is repeated three times. Subsequently, the solution containing the nanoparticles coated with the zwitterionic ligand compound of the present invention may be concentrated using a concentration column such as a centrifugal ultrafiltration filter. This concentration operation may be repeated a plurality of times, or a solution such as PBS may be added in the middle and the concentration operation may be repeated.
[0090]
B) TMA (OH) method
　Oleic acid-coated iron oxide particles (SNP-OA) are suspended in a hexane solution and mixed with a 1.7% tetramethylammonium hydroxide (TMA (OH)) aqueous solution. Shake vigorously. The aqueous layer is separated from the obtained solution by centrifugation, acetone is added, and the mixture is centrifuged at 8000 to 12000 rpm for 5 to 10 minutes to remove the supernatant. To the obtained precipitate, add 2 mL of 0.1% TMA (OH) solution to disperse, and add 10 mL of acetone again to precipitate. This operation may be repeated a plurality of times, preferably 3 to 4 times. The obtained solution is dispersed in a 0.1% TMA (OH) solution and stored.
　A solution of the ligand compound prepared to have a pH of about 8 to 12 using a 0.1% to 2% TMA (OH) solution is added to the 0.1% TMA (OH) solution prepared in the above procedure. The obtained solution is stirred at room temperature for 6 to 24 hours, acetone is added to precipitate, and the mixture is centrifuged at 8000 to 12000 rpm for 3 to 10 minutes to remove the supernatant. The amount of solution is reduced by dispersing this precipitate in phosphate buffer and centrifuging at 7000 to 12000 rpm using a concentrated column. Phosphate buffer is added thereto, and the mixture is centrifuged again at 7000 to 12000 rpm for 10 to 20 minutes to concentrate. This operation may be repeated a plurality of times, preferably 3 to 4 times, more preferably 5 to 10 times to obtain nanoparticles in which one or more zwitterionic ligands of the present invention are coordinated. The resulting solution of nanoparticles may be diluted with PBS and stored.
[0091]
C) Phase transfer catalyst method In
　the presence of a phase transfer catalyst, metal particles in which a hydrophobic ligand such as oleic acid is coordinated and bonded to the surface are placed in a two-layer solvent of an organic layer and an aqueous layer, and the dual ions of the present invention are present. This is a method for producing nanoparticles in which one or more biionic ligands of the present invention are coordinated and bonded by contacting with a ligand compound.
　The "two-layer solvent of an organic layer and an aqueous layer" is a mixed solvent of an organic solvent and water, which is separated into two layers. The organic solvent is an aprotic solvent, and in one embodiment, 2-methyltetrahydrofuran (2-Me-THF), cyclopentyl methyl ether (CPME), methyl tert-butyl ether (MTBE), chloroform, toluene, xylene, etc. It is selected from the group consisting of heptane and combinations thereof. In another embodiment, it is selected from 2-methyltetrahydrofuran, chloroform and combinations thereof.
[0092]
　The "phase transfer catalyst" is a phase transfer catalyst selected from salts having quaternary ammonium and quaternary phosphonium which are soluble in both organic solvents and water, and in one embodiment, quaternary ammonium is used. A salt, for example, a quaternary ammonium salt is selected from the group consisting of tetrabutylammonium salt, trioctylmethylammonium salt and benzyldimethyloctadecylammonium salt. Examples of the anion forming the salt here include a halide ion, a hydroxide ion, a hydrogen sulfate ion, and the like. In yet another embodiment, it is a halogenated tetrabutylammonium salt, for example, the halogenated tetrabutylammonium salt is selected from tetrabutylammonium bromide (TBAB) and tetrabutylammonium fluoride (TBAF). In yet another embodiment, it is a hydrate of tetrabutylammonium fluoride, such as tetrabutylammonium fluoride trihydrate.
[0093]
　Further, if desired, a pH adjuster may be added, and for example, sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate or dipotassium hydrogen phosphate can be used.
[0094]
　In the reaction, metal particles having a hydrophobic ligand coordinated to the surface and a biionic ligand compound are selected from nitrogen and argon in a two-layer solvent of an organic layer and an aqueous layer in the presence of a phase transfer catalyst. In an inert gas atmosphere, at room temperature or under warming, in one embodiment at room temperature to 80 ° C., in another embodiment at 30 ° C. to 60 ° C. for 1 hour or longer, in another embodiment 1 to 20 hours, separately. In one embodiment, the stirring is carried out for 1 to 15 hours, and in another embodiment, the stirring is carried out for 1 to 6 hours. The reaction temperature and reaction time can be appropriately adjusted according to the metal particles used in the reaction and the type of zwitterion ligand.
　In this reaction, the zwitterionic ligand can be used at a ratio of 1 to 30 wt (weight ratio) to the metal particles, 5 to 20 wt in one embodiment, and 6 to 15 wt in another embodiment. The phase transfer catalyst is 0.1 to 10 wt with respect to the metal particles, 0.1 wt to 6 wt in one embodiment, 0.1 wt to 5 wt in another embodiment, 0.5 to 6 wt in another embodiment, and another. It can be carried out by adding at a ratio of 0.5 to 3 wt as an embodiment and 0.5 wt to 2 wt as yet another embodiment. Further, when a pH adjuster is used, the phase transfer catalyst can be added at a ratio of 0.1 wt to 5 wt, and in some embodiments 0.5 wt to 2 wt, with respect to the metal particles.
[0095]
　Isolation of nanoparticles from the reaction solution can be performed using known methods such as centrifugation, ultrafiltration, or liquid separation manipulation. As an example, Amicon (registered trademark) Ultracentrifuge filter (Merck Millipore), Agilent Captiva Premium Syringe Filters (Regenerated Cellulose, 15 mm), YMC Duo-Filter can be separated by repeating centrifugation, etc. The resulting solution of nanoparticles may be diluted with PBS and stored.
[0096]
　Regardless of which method is used, when the twin ion ligand of the present invention is used, nanoparticles obtained by simply exchanging a ligand from a surface hydrophobic ligand to a twin ion ligand are produced, and nanoparticles are produced. Nanoparticles in which the metal particles in the particles are smaller than the metal particles used as the raw material (for example, 3K purified particles shown in Examples described later) may be produced. Many are available in both types. It is presumed that this is because the zwitterionic ligand of the present invention has a property of changing the metal particles when coordinate-bonded, and differs depending on the zwitterionic ligand. It may change depending on the reaction conditions and purification conditions.
[0097]
　By adjusting the type of zwitterionic ligand to be used, reaction conditions and isolation conditions, nanoparticles having a core-shell structure and / or nanoparticles having fine metal particles (clusters, complexes, etc.) can be obtained. be able to.
　In one embodiment, one or more zwitterionic ligand compounds are coordinate-bonded to the outer surface of the metal particles containing iron oxide to produce particles coated with the zwitterion ligand compounds. NS.
　In one embodiment, as a complex composed of one or more "metal particles containing iron oxide in which one or more zwitterion ligand compounds are coordinated and bonded" and one or more zwitterion ligand compounds, the micron is minute. Particles are produced.
　In one embodiment, a cluster consisting of two or more zwitterionic ligand compounds and two or more "metal particles containing iron oxide in which one or more zwitterionic ligand compounds are coordinated and bonded" is produced.
　In any form, the nanoparticles of the present invention can be used as a contrast agent for magnetic resonance imaging.
　One embodiment is the method described in the examples below.
[0098]
　[5. Contrast Agent for Magnetic Resonance Imaging (Contrast Agent for MRI)] The
　present invention also provides a contrast agent for magnetic resonance imaging containing the above-mentioned nanoparticles.
[0099]
　Hereinafter, the contrast medium for MRI will be described in detail.
[0100]
　(Various Components Included in MRI Contrast Agent)
　i) Nanoparticles In
　one embodiment, the MRI contrast agent of the present invention is characterized by containing at least one of the above-mentioned nanoparticles. In another embodiment, the MRI contrast agent of the present invention may contain a combination of two or more of the nanoparticles described above.
[0101]
　In addition to the nanoparticles, the contrast agent for MRI can contain a solvent and a pharmacologically acceptable additive, if necessary. As one embodiment of the contrast agent for MRI of the present invention, at least one selected from a suitable solvent and / or an additive such as a carrier, a vehicle, and a complex may be further contained.
[0102]
　ii) Solvent
　Examples of the solvent contained in the contrast agent for MRI include water and a buffer solution, and further examples of the buffer solution include physiological saline, phosphate buffer solution, Tris buffer solution, borate buffer solution and Ringer solution. And so on. When the dosage form is an injection, the preferred solvent is, for example, water, Ringer solution, physiological saline or the like.
[0103]
　That is, the contrast agent for MRI according to the present invention may be a solution in which the nanoparticles according to the present invention are suspended in a solution having a desired composition. Specifically, the nanoparticles may be suspended in a buffer solution such as a phosphate buffer solution, a Tris buffer solution, or a boric acid buffer solution.
[0104]
　iii) Additives Examples of additives such
　as carriers, complexes, and vehicles contained in contrast media for MRI include carriers, vehicles, and the like that are generally used in the fields of pharmaceuticals and biotechnology. Examples of the carrier include polymers such as polyethylene glycol and fine metal particles, and examples of the complex include diethylenetriamine-5acetic acid (DTPA), 1,4,7,10-tetraazacyclododecane-1,4,7. , 10-Tetraacetic acid (DOTA), etc. Examples of vehicles include lime, soda ash, sodium silicate, starch, glue, gelatin, tannins and kebracho.
[0105]
　Further, the contrast agent for MRI according to the present invention may further contain an excipient, a lubricant, a wetting agent, an emulsifier, a suspending agent, a preservative, a pH adjusting agent, an osmotic pressure adjusting agent and the like.
[0106]
　(Dosage Form)
　The dosage form of the contrast medium for MRI of the present invention is not particularly limited and may be liquid, solid, semi-solid or semi-liquid. These dosage forms can be easily produced based on methods known to those skilled in the art. When the dosage form is liquid, for example, the nanoparticles according to the present invention may be dispersed, suspended or dissolved in an aqueous solvent. Further, as the form of the freeze-drying agent, it may be dispersed, suspended or dissolved at the time of use.
[0107]
　(Concentration of nanoparticles) The concentration
　of nanoparticles in the contrast medium for MRI is appropriately determined according to the purpose, the tissue to be imaged, and the like. For example, a concentration within a range having an appropriate contrast ability and an acceptable effect on the living body is selected.
[0108]
　The nanoparticles of the present invention are less likely to aggregate even at high concentrations and can maintain stability. Therefore, it is expected that higher MRI contrast ability can be stably maintained for a long period of time as compared with known nanoparticles.
[0109]
　For example, when the contrast medium for MRI is an aqueous solution, the concentration of nanoparticles in the solution is, for example, 0.1 to 1000 mM Fe, preferably 1.0 to 500 mM Fe when used as a general injection. Further, the concentration can be 5.0 to 100 mM Fe, 10 to 500 mM Fe in one embodiment, 5.0 to 50 mM Fe in another embodiment, and the like.
[0110]
　(Administration Target)
　The administration target of the contrast medium according to the present invention includes any non-human organism or human. Non-human organisms include mammals (eg, rodents such as mice, rats and rabbits, primates such as monkeys, dogs, cats, sheep, cows, horses, and pigs), birds, reptiles, amphibians, and fish. , Insects and plants, but not limited to these. In some embodiments, the animal can be a transgenic animal, a genetically engineered animal or a cloned organism. In addition, the administration target other than the living body may be a tissue sample or a biological material containing cells.
[0111]
　(Application to which MRI contrast medium is applied) As
　described above, there are two types of MRI contrast medium, a positive contrast medium and a negative contrast medium.
[0112]
　In one embodiment, the MRI contrast agent of the present invention is a positive contrast agent. Another embodiment is a negative contrast agent.
[0113]
　The present invention also includes an MRI contrast method using the above-mentioned MRI contrast agent. Further, the present invention also relates to a method of contrasting various target organs with an MRI apparatus using the contrast agent for MRI. For example, a method of contrasting kidney, liver, and cerebrovascular can be mentioned. The present invention also relates to a method for diagnosing lesions and the presence or absence of tumors in various target organs using the contrast medium for MRI. For example, it can be suitably used for a method for diagnosing renal function, a method for diagnosing liver tumor, and the like. Furthermore, the present invention also relates to a method for visualizing various target organs by an MRI apparatus using the above-mentioned contrast agent for MRI. For example, it can be suitably used for visualization of kidneys, liver, cerebral blood vessels and the like. Here, the MRI apparatus may be any apparatus, and known ones can be used. Further, as the applied magnetic field, for example, 1T, 1.5T, 3T and 7T are used. The diagnostic method or visualization method using the contrast medium of the present invention is a step of administering a positive contrast medium to a living human or other subject, and subsequently, MRI of a desired organ of the subject using an MRI apparatus. It includes the process of obtaining an image.
[0114]
　When an external magnetic field is applied, paramagnetism is oriented in the same direction as the magnetic field to which the dipole moment is applied, which was in an arbitrary direction, and is magnetized in the same direction as the external magnetic field. Such materials T by dipole-dipole interactions 1 results in a shortening effect. While a net magnetic moment in the same mechanism also superparamagnetic occurs, magnetic susceptibility greater than the magnetic susceptibility of a paramagnetic substance, T 2 shortening effect is large. This contrast agent is considered to exhibit paramagnetism or superparamagnetism within the boundary or paramagnetism, and it is presumed that both relaxation mechanisms are affected by the magnetic field strength, resulting in T 1 , T 2 and T 2 * relaxation. In particular T in practical magnetic field region 1 by shortening effect, it is expected to result in higher positive contrast effect.
　The indication of paramagnetism within the boundary between paramagnetism and superparamagnetism can be confirmed by measuring the magnetic field dependence of magnetization using a superconducting quantum interferometer (SQUID). FIG. 7 shows a measurement example at 300K. Magnetic susceptibility is substantially proportional to the magnetic field, the nature of the superparamagnetic are considered low, yet nanoparticle has a property of paramagnetic, excellent T in a practical magnetic field region 1 shortening effect can be expected ..
　In one embodiment, imaging capability of the contrast agent according to the present invention, in a magnetic field of 37 ° C. and 1.5T, r 2 relaxivity 2.8 ~ 6.2 mM -1It is s -1 , and the r 1 relaxation ability is in the range of 2.5 to 4.4 mM -1 s -1 . In another embodiment, imaging capability of the contrast agent according to the present invention, in a magnetic field of 37 ° C. and 1.5T, r 2 relaxivity 3.0 ~ 4.2 mM -1 s -1 is, r 1 relaxivity 2.7 The range is ~ 3.9 mM -1 s -1 .
[0115]
　Relaxation ability is a variety of factors such as particle size, composition, charge or properties of particle surface, particle stability, and cohesiveness and tissue binding in living organisms in contrast medium nanoparticles for MRI. Depends on. The relaxation capacity ratio, r 1 / r 2, is commonly used to quantify the type of contrast produced by MRI and can be an indicator of the performance of the contrast agent.
[0116]
　For MRI positive contrast agents of the present invention, r in order to improve the diagnostic performance by obtaining a higher positive contrast effect 1 / r 2 preferably as the value of is large, when the magnetic field is 1.5T r 1 / r The value of 2 is, for example, preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. When the r 1 / r 2 value is 0.7 or more, the T 1 (positive) effect is excellent, and even in MRI measurement with a higher magnetic field, it has a high resolution and a high contrast effect. From the viewpoint of significantly enhancing the contrast effect and administering a smaller amount of the positive contrast agent for MRI, the value is preferably 0.8 or more.
[0117]
　In the nanoparticles of the present invention, the molecular chain length of the zwitterionic ligand is shorter than that of a known ligand, the distance between the metal particle and an external water molecule is shortened, and the relaxation ability can be efficiently extracted.
[0118]
　In the contrast agent for MRI of the present invention, contrast for MRI using nanoparticles having a particle size of metal particles (including the case where the average diameter of clusters or complexes containing metal particles is 2 nm or less) is 2 nm or less, for example, 1 nm or less. agents include, the MRI contrast agent T in the MRI apparatus of the above 7T 1 is can be used as a positive contrast agent in the enhanced image. As an example, a positive contrast agent for MRI for use in an MRI apparatus of 7T or less is included. One example includes a positive contrast agent for MRI for use in an MRI apparatus of 3T or less.
[0119]
　(Toxicity and Stability)
　The contrast medium for MRI of the present invention has high nanoparticle stability, and the degree of aggregation can be confirmed by the method described in Test Example 3 below, and the degree of aggregation can be confirmed in a solution at room temperature or 4 ° C. It is expected that it can be stored for a long time without agglomeration. In addition, it is less toxic to living organisms and is expected to be applicable to living organisms for a long period of time.
[0120]
　[6. Illustrative Specific Aspects of the Present Invention] In
　order to solve the above problems, the present invention includes any one of the following aspects.
　Unless otherwise specified, when a symbol in a chemical formula in the present specification is also used in another chemical formula, the same symbol has the same meaning.
<1>
　Nanoparticles containing iron oxide-containing metal particles to which one or more zwitterionic ligands represented by the formula (I) are coordinated.
[Chemical

formula 19] (In the formula, one of
R 1 and R 2 is a group represented by the formula (a) or the formula (b), and the other is H, a lower alkyl, an —O- lower alkyl or a halogen. ,
[Chemical formula 20]

X 1 may be a bond or methylene, and X 1 may be ethylene when R 1 is a group represented by the formula (a), and X 2 may be substituted with OH. Good C 1-5 alkylene or -C 1-2 alkylene-OC 1-3
Alkylene -, and further R 1 X when groups are represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b combine with the quaternary nitrogen atom to which they bind to form a 5- or 6-membered nitrogen-containing saturated heterocycle. ,
Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, -O-C 1-3When it is alkyl or halogen,
n is an integer of 0 to 2
, and
i) R 1 is the group represented by the formula (a) and X 1 is methylene, then R 2 and Ra or R b may be integrated to form ethylene, and when
ii) R 1 is a group represented by the formula (a) and X 1 is ethylene, R 2 and Ra or R b preparative may form a methylene together, and
iii) R 2 is a group is of formula (a), and, X 1 when is methylene, R 3 and R a or R b and May form ethylene together,
provided that R 2 is the group represented by the formula (a), Ra and R b are methyl, X 1 is a bond, X 2 is C 1-4 alkylene, and R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
<2>
　zwitterionic
ligands, R 1 and R 2 one is a group of formula (a) or formula (b), the other, H, lower alkyl or
halogen, X 1 is X 1 when it is a bond or methylene, and R 1 is a group represented by the formula (a). May be ethylene,
X 2 is C 1-5 alkylene, which may be substituted with OH , or -C 1-2 alkylene-OC 1-3 alkylene-, and R 1 is further. X when the group represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene--O-C 1 -2 alkyl, or, R a and R b are, they, together with the quaternary nitrogen atom attached to form a pyrrolidine
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - a
and, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, or halogen,
n is 1,
further,
i) R 1 is represented by the formula (a) Nanoparticles of <1>, which are zwitterionic ligands, which are groups and when X 1 is methylene, R 2 and Ra or R b may be integrated to form ethylene
.
<3> In the
　zwitterionic ligand,
R 1 is a group represented by the formula (a) or the formula (b), R 2 is H or a halogen,
X 1 is a bond or methylene, and further. When R 1 is a group represented by the formula (a), X 1May be
ethylene, X 2 is, C 1-5 alkylene, further R 1 X when groups are represented by the formula (b) 2 may be a
bond, R a and R b are both
methyl, Y - is, SO 3 - or, CO 2 - and is,
zwitterionic ligand nanoparticles <2>.
<4> The
　zwitterion ligand is a zwitterion ligand in which one of R 1 and R 2 is a group represented by the formula (a) and the other is H, a lower alkyl, an —O- lower alkyl or a halogen. The nanoparticles of <1>.
<5> The
　zwitterion ligand is
1) R 1 is the group represented by the formula (a), and R 2 is a zwitterionic ligand that is H, lower alkyl, -O-lower alkyl or halogen, or
2) R 1 is H and R 2 is the group represented by formula (a), R Nanoparticles of <4>, where 3 is C 1-3 alkyl or halogen and R 4 is H, which is a
zwitterionic ligand.
<6> The
　zwitterionic ligand is a zwitterionic ligand in which R 1 is the group represented by the formula (a) and R 2 is H, a lower alkyl, an —O- lower alkyl or a halogen. <5> nanoparticles.
<7> The
　zwitterionic ligands are
R 2 being H or halogen,
X 1 being bound, methylene or ethylene, and
X 2 being C 2-4 alkylene.
When R a and R b are both methyl,
R 3 and R 4 are the same or different, H, C 1-3 alkyl or halogen, and
X 1 is methylene, then R 2 and R Nanoparticles of <6>, which are zwitterionic ligands, which may form ethylene together with a or R b
.
<8> The
　zwitterionic ligand is a zwitterionic ligand in which
R 2 is H or F,
X 2 is ethylene or propylene, and
R 3 and R 4 are both H
, <7>. Nanoparticles.
<9>
The nanoparticles of <8> where the zwitterionic ligand is
R 2 is H,
X 1 is bound or ethylene, and is a
zwitterionic ligand.
<10>
　zwitterionic ligands,
Y - is SO 3 - or CO 2 - a,
a zwitterionic ligands, nanoparticles according to any one of <4> to <9>.
<11> In the
　zwitterionic ligand,
R 1 is the group represented by the following formula (b-1),
[Chemical 21]

R 2 is H or halogen, and
X 1 is bound or methylene. ,
X 2 is C 1-5Alkylene or a
bond, R a is
methyl, Y - is SO 3 - , or, CO 2 - a,
a zwitterionic ligands, nanoparticles <3>.
<12>
　The nanoparticles according to any one of <1> to <11>, wherein the metal particles containing iron oxide are metal particles containing only iron oxide.
<13>
　Nanoparticles are particles formed by coordination-bonding one or more twin ion ligands to the outer surface of metal particles containing iron oxide, and the metal particles are coated with the twin ion ligands. The nanoparticles according to any one of <1> to <12>, which are nanoparticles.
<14> The
　nanoparticles are a complex composed of
metal particles containing iron oxide to which one or more zwitterionic ligands are coordinated and
one or more zwitterionic ligands, and one or more zwitterionic ligands.
The nanoparticles according to any one of <12>.
<15>
　Nanoparticles are
two or more zwitterionic ligand compounds, and

The nanoparticle according to any one of <1> to <12>, which is a cluster composed of two or more "metal particles containing iron oxide in which one or more zwitterionic ligand compounds are coordinated and bonded" .
<16>
　A contrast agent for magnetic resonance imaging containing the nanoparticles according to any one of <1> to <15>.
<17> A
　contrast medium for magnetic resonance imaging of <16>, which is a positive contrast medium.
<18>
　Use of the zwitterionic ligand compound represented by the following formula (I) for producing the nanoparticles of <1>.
[Chemical

formula 22] (In the formula, one of
R 1 and R 2 is a group represented by the following formula (a) or formula (b), and the other is H, lower alkyl, -O-lower alkyl or halogen. Yes,
[Chemical 23]

X 1 is a bond or methylene, and when R 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 is substituted with OH. Good C 1-5Alkylene, or, -C 1-2 alkylene -O-C 1-3 alkylene - and further R 1 X when groups are represented by the formula (b) 2 may be a
bond, R a and R b is the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are quaternary nitrogen atoms to which they are attached. and to form a 5- or 6-membered nitrogen-containing saturated heterocyclic ring
together, Y - is, SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4Are the same or different from each other, H, C 1-3 alkyl, -OC 1-3 alkyl or halogen,
n is an integer of 0 to 2
, and
i) R 1 is the formula (a). When it is a group represented by and X 1 is methylene, R 2 and Ra or R b may be integrated to form ethylene, and
ii) R 1 is represented by the formula (a). When X 1 is ethylene, R 2 and Ra or R b may be integrated to form methylene, and
iii) R 2 is represented by the formula (a). When it is a group and X 1 is methylene, R 3 and RaAlternatively, R b may be integrated to form ethylene,
where R 2 is the group represented by the formula (a), R a and R b are methyl, and X 1 is a bond. X 2 is, C 1-4 alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
<19>
　zwitterionic ligand compound, R 1 and R 2 one is a group of formula (a), the other, H, lower alkyl, zwitterionic is -O- lower alkyl or halogen Use of <18>, which is an ionic ligand compound.
<20>
　A compound represented by the following formula (I) or a salt thereof.
[Chemical

formula 24] (In the formula, one of
R 1 and R 2 is a group represented by the following formula (a) or formula (b), and the other is H, lower alkyl, -O-lower alkyl or halogen. Yes,
[Chemical 25]

X 1 is a bond or methylene, and when R 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 is substituted with OH. It may be C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene-, and when R 1 is a group represented by the formula (b), X 2 may be a bond.
well, R a and R b are the same or different from each other, C 1-3Alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are 5- or 6-membered nitrogen-containing saturated heteros integrated with the quaternary nitrogen atom to which they are attached. forms a
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, -O-C When 1-3 alkyl or halogen,
n is an integer of 0 to 2
,
i) R 1 is the group represented by the formula (a), and X 1 is methylene, then R 2 and R A or R b may be integrated to form ethylene, and
ii) when R 1 is a group represented by the formula (a) and X 1 is ethylene, R 2 and Ra or R b may be integrated to form methylene, and when
iii) R 2 is a group represented by the formula (a) and X 1 is methylene, R 3 and Ra or R Ethylene may be formed integrally with b ,
except that R 2 is a group represented by the formula (a), Ra and R b are methyl, X 1 is a bond, and X 2 But C 1-4Alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. ) 　<21>
R 1 and R 2 one is a group of formula (a) or formula (b), the other, H, lower alkyl or halogen, X 1 is a bond or methylene Further, when R 1 is a group represented by the formula (a), X 1 may be ethylene, and X 2 may be substituted with OH. C 1-5 alkylene or -C 1-2. It is alkylene-OC 1-3 alkylene-, and further R 1

There X when the group represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene--O-C 1-2 alkyl, or, R a and R b are, they, together with the quaternary nitrogen atom attached to form a pyrrolidine
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, or halogen,
n is 1,
further, i) R 1Is a group represented by the formula (a), and when X 1 is methylene, R 2 and Ra or R b may be integrated to form ethylene,
the compound of <20> or That salt.
<22>
　R 1 is a group represented by the formula (a) or the formula (b), R 2 is H or a halogen,
X 1 is a bond or methylene, and R 1 is a formula (a). ) X when the group represented by 1 may be
ethylene, X 2 is, C 1-5 alkylene, further R 1 X when groups are represented by the formula (b) 2 is a bond at
best, R a and R b are both methyl,
Y - is, SO 3 - or, CO 2 - is a compound or a salt thereof <21>.
<23> A compound of <20> or a salt thereof, wherein one of
　R 1 and R 2 is a group represented by the formula (a) and the other is H, a lower alkyl, an —O— lower alkyl or a halogen.
<24>
　4-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate,
3-{[(6-fluoro-2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl }
Propyl- 1-sulfonate, hydrogen = (3-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} propyl) phosphonate,
5-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) Azaniumyl} pentanoate
{1-[(2,3-dihydroxyphenyl) methyl] -1-methylpiperidin-1-ium-4-yl} acetate,
1-[(2,3-dihydroxyphenyl) methyl] -1 -Methylpiperidin-1-ium-4-carboxylate,
4-{[2- (2,3-dihydroxyphenyl) ethyl] (dimethyl) azaniumyl} butanoate,
2-{[2- (2,3-dihydroxyphenyl) ethyl] (dimethyl) azaniumyl} ethane-1-sulfonate, And
3-[(2,3-dihydroxyphenyl) (dimethyl) azaniumyl] propan-1-sulfonate
, the compound of <20> selected from the group, or a salt thereof.
<25>
　{1-[(2,3-dihydroxyphenyl) methyl] -1-methylpiperidin-1-ium-4-yl} acetate, and
2-{[2- (2,3-dihydroxyphenyl) ethyl]
A compound of <24> or a salt thereof selected from the group consisting of (dimethyl) azaniumyl} ethane-1-sulfonate .
<26>
　4-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate, and
3-{[(6-fluoro-2,3-dihydroxyphenyl) methyl] (dimethyl)
A compound of <24> selected from the group consisting of azaniumyl} propan-1-sulfonate or a salt thereof.
　The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.
Example
[0121]
　Production examples and examples will be shown below, and the present invention will be described in more detail.
　In addition, the following abbreviations may be used in Examples, Production Examples and Tables below.
[0122]
　PEx: Production example number, Ex: Example number, PSyn: Production example number produced by the same method, ESyn: Example number produced by the same method, Str: Chemical structural formula, Me: Methyl group, Et: Ethyl Group, Data1: Means physicochemical data of production example, NMR-D: δ (ppm) of characteristic peak in 1H-NMR in DMSO-d6, ESI +: m / z value (ionization) in mass spectrometric value The method ESI indicates (M + H) + unless otherwise specified, and (M +) + indicates (M +) + when it is ESI (M +) + in the table below.) APCI / ESI (M +) +: Indicates the m / z value (ionization method APCI and ESI) in the mass spectrometric value. Production Example 27 shows Mass data of the oleic acid moiety excluding iron ions, and its ESI is (M-)-. Data2: Means the physicochemical data of the examples, SEC (min) means the outflow time of nanoparticles under the conditions described in Test Example 2, and 3K means the particles purified by the filter described below. A certain 3K purified particles, 10K means 10K purified particles which are particles purified by the filter described below. THF: tetrahydrofuran, DMF: N, N-dimethylformamide, OA: oleic acid, MEAA: [2- (2-methoxyethoxy) ethoxy] acetic acid, TBAF trihydrate: tetrabutylammonium fluoride trihydrate, PBS : Phosphate buffered saline, OA or MEAA coordinate-bonded iron oxide nanoparticles are referred to as SNP-OA and SNP-MEAA, respectively. In the structural formula, Br − indicates a bromide ion and I − indicates an iodide ion. For reverse phase column chromatography, a column packed with silica gel whose surface was modified with ODS (octadecylsilyl group) was used.
[0123]
　The Amicon Ultracentrifuge 3K filter (Merck Millipore) used for the purification of iron oxide nanoparticles is referred to as the Amicon 3K filter. Further, when the same instrument having different fractional molecular weights of 10K, 30K, 50K, and 100K is used, they are similarly described as Amicon 10K filter, Amicon 30K filter, Amicon 50K filter, and Amicon 100K filter. The particles purified by ultrafiltration of the fractional molecular weights of 30K, 10K, and 3K are referred to as 30K purified particles, 10K purified particles, and 3K purified particles, respectively.
Filtration of particles using Agilent Captiva Premium Syringe Filters (Regenerated Cellulose, 15 mm, pore size: 0.2 μm) or YMC Duo-Filter (XQUO15 pore size 0.2 μm) is referred to as membrane (0.2 μm) filtration.
　Further, the broken line in the example table described later represents a coordination bond with a metal atom on the surface of the metal particle.
[0124]
　The compounds of Production Examples and nanoparticles of Examples shown in the table below were produced according to or in the same manner as the following Production Examples or Examples.
　In addition, in the production example of the zwitterion ligand compound, the iron oleic acid complex, and the iron oxide nanoparticles (SNP-OA) coated with oleic acid, directly from SNP-OA or via SNP-MEAA. An example of producing nanoparticles in which a zwitterion ligand compound is coordinate-bonded is described in Examples.
[0125]
Production Example 1 A
　9.5 mol / L dimethylamine aqueous solution (7.1 mL) was added to 6-fluoro-2,3-dimethoxybenzaldehyde (2.50 g), and the mixture was stirred at room temperature for 15 hours. Sodium borohydride (514 mg) was added thereto under a water bath, and the mixture was stirred at room temperature for 2 hours. Concentrated hydrochloric acid was added under an ice bath (pH 1-2). The aqueous layer was washed twice with dichloromethane. A 1 mol / L sodium hydroxide aqueous solution was added to this aqueous layer (pH> 11). This was extracted three times with dichloromethane and dried over anhydrous sodium sulfate. After filtration, the mixture was concentrated to obtain 1- (6-fluoro-2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (2.46 g).
[0126]
Production Example 2
　Sodium triacetoxyborohydride (13.6 mL) in a mixture of 4-fluoro-2,3-dimethoxybenzaldehyde (2.50 g), dichloromethane (75 mL) and 2 mol / L dimethylamine THF solution (13.6 mL). 3.74 g) was added, and the mixture was stirred at room temperature for 1 hour. Basic silica gel was added, and the mixture was concentrated under reduced pressure. Purification by basic silica gel column chromatography (developing solvent: hexane-chloroform) gave 1- (4-fluoro-2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (2.81 g).
[0127]
Production Example 3
　1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (3.82 g), 1,2λ 6 -oxathiolane-2,2-dione (1.89 mL), ethyl acetate (38. The mixture (2 mL) was stirred at room temperature for 7 days. Further, 1,2λ 6 -oxathiolane-2,2-dione (515 μL) was added, and the mixture was stirred at 50 ° C. for 4 hours. After allowing to cool to room temperature, the solid was collected by filtration, washed with ethyl acetate, dried under reduced pressure, and 3-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} propan-1-sulfonate (5. 41 g) was obtained.
[0128]
Production Example 4
　1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (3.00 g), sodium carbonate (1.63 g), sodium 2-bromoethane-1-sulfonate (3.24 g), A mixture of water (6 mL) and ethanol (30 mL) was stirred at 75 ° C. for 3 days. Further, sodium 2-bromoethane-1-sulfonate (3.24 g) was added, and the mixture was stirred at 80 ° C. for 2 days. Further, sodium 2-bromoethane-1-sulfonate (3.24 g) was added, and the mixture was stirred at 80 ° C. for 2 days. After allowing to cool to room temperature, the mixture was concentrated under reduced pressure. Water was added and purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and 2-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} ethane-1-sulfonate (3.50 g) Got
[0129]
Production Example 5
　1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (2.00 g), 1,2λ 6 -oxatian-2,2-dione (1.36 mL), ethyl acetate (20 mL) The mixture was stirred at 50 ° C. for 3 hours and then at 70 ° C. for 24 hours. Further, 1,2λ 6 -oxatian-2,2-dione (1.04 mL) was added, and the mixture was stirred at 70 ° C. for 24 hours. After allowing to cool to room temperature, the solid was collected by filtration, washed with ethyl acetate, dried under reduced pressure, and 4-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate (2. 28 g) was obtained.
[0130]
Production Example 6 A mixture of
　2-fluoro-4,5-dimethoxyaniline (2.50 g), 1,2λ 6 -oxathiolane-2,2-dione (1.54 mL) and acetonitrile (63 mL) is stirred at 115 ° C. for 8 hours. bottom. Further, 1,2λ 6- oxathiolane -2,2-dione (0.64 mL) was added, and the mixture was stirred at 115 ° C. for 8 hours. After allowing to cool to room temperature, the solid was collected by filtration, washed with acetonitrile, dried under reduced pressure at 50 ° C., and 3- (2-fluoro-4,5-dimethoxyanilino) propan-1-sulfonic acid (4.00 g). ) Was obtained.
[0131]
Production Example 7
　3- (2-chloroethoxy) propan-1-sulfonic acid (1.46 g), dioxane (22 mL), water (11 mL) in a mixture of 3,4-dimethoxyaniline (1.66 g), iodide Potassium (1.79 g) and potassium carbonate (2.49 g) were added, and the mixture was stirred at 100 ° C. overnight. The reaction mixture is allowed to cool to room temperature, concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and lyophilized by 3- [2- (3,4-dimethoxyanilino) ethoxy. ] Propane-1-sulfonic acid (532 mg) was obtained.
[0132]
Production Example 8
　Mixture of 2-methoxy-N- (2-methoxyethyl) ethane-1-amine (3.0 mL), 1,2λ 6 - oxathiolane -2,2-dione (2.0 mL), acetonitrile (27 mL) Was stirred at 80 ° C. for 4 hours. After allowing to cool to room temperature, concentrate, add diethyl ether, stir at room temperature for 2 hours, filter the solid, and dry under reduced pressure at room temperature to 3- [bis (2-methoxyethyl) amino] propane-1. -Sulfonic acid (5.00 g) was obtained.
[0133]
Production Example 9
　1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (1.70 g), 3-chloro-2-hydroxypropane-1-sodium sulfonate (3.42 g), potassium iodide A mixture of (1.73 g), ethanol (26 mL) and water (7.7 mL) was stirred at 80 ° C. overnight. After allowing to cool to room temperature, concentrate, purify by reverse phase column chromatography (developing solvent: acetonitrile-water), and freeze-dry to 3-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl. } -2-Hydroxypropane-1-sulfonate (2.17 g) was obtained.
[0134]
Production Example 10
　7,8-dimethoxy-1,2,3,4-tetrahydroisoquinoline (1.80 g), 1,2λ 6 - oxathiolane -2,2-dione (0.98 mL ), potassium carbonate (1.29 g) , The mixture of acetonitrile (45 mL) was stirred at 100 ° C. for 8 hours. After allowing to cool to room temperature, water is added, concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and lyophilized by 3- (7,8-dimethoxy-3,4-dihydro). Isoquinolin-2 (1H) -yl) propan-1-sulfonic acid (1.79 g) was obtained.
[0135]
Production Example 11
　A mixture of 1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (1.30 g), diethyl (3-bromopropyl) phosphonate (1.66 mL), ethanol (6.50 mL). Was stirred at 80 ° C. for 6 hours. After allowing to cool to room temperature, it is concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and 3- (diethoxyphosphoryl) -N-[(2,3-dimethoxyphenyl) methyl] -N, N-Dimethylpropan-1-aminium = bromide (2.70 g) was obtained.
[0136]
Production Example 12
　3- [bis (2-methoxyethyl) amino] propan-1-sulfonic acid (3.00 g), 1- (chloromethyl) -2,3-dimethoxybenzene (4.39 g), potassium carbonate (1) A mixture of .95 g) and ethanol (45 mL) was stirred at 80 ° C. overnight. After allowing to cool to room temperature, it is concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and lyophilized by 3-{[(2,3-dimethoxyphenyl) methyl] bis (2- Methyl) azaniumyl} propan-1-sulfonate (3.09 g) was obtained.
[0137]

　A mixture of Production Example 13 (3-bromopropyl) phosphonate diethyl (2.53 g) and 3,4-dimethoxyaniline (3.00 g) was stirred at 95 ° C. for 6 hours under an argon atmosphere. The mixture was allowed to cool to room temperature, saturated aqueous sodium hydrogen carbonate solution was added, and the mixture was extracted once with ethyl acetate. The organic layer was washed once with saturated brine and dried over anhydrous magnesium sulfate. After filtration, it is concentrated and purified by silica gel column chromatography (developing solvent; hexane-ethyl acetate, then ethyl acetate-methanol) to [3- (3,4-dimethoxyanilino) propyl] diethyl phosphonate (1. 74 g) was obtained.
[0138]
Production Example 14
　A mixture of 1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (2.00 g) and ethyl 4-bromobutaneate (2.60 g) was stirred at 80 ° C. for 3 hours. By purifying this with reverse phase column chromatography (developing solvent; water-acetriform), N-[(2,3-dimethoxyphenyl) methyl] -4-ethoxy-N, N-dimethyl-4-oxobutane-1- Aminium-bromid (3.93 g) was obtained.
[0139]
Production Example 15
　1- (6-fluoro-2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (1.20 g), 1,2λ 6 -oxathiolane-2,2-dione (990 μL), ethyl acetate ( The mixture (12 mL) was stirred at 50 ° C. for 18 hours. After allowing to cool to room temperature, the solid was collected by filtration, washed with ethyl acetate, dried under reduced pressure, and 3-{[(6-fluoro-2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} propane-1- Sulfonate (1.79 g) was obtained.
[0140]
Production Example 16
A mixture of 1- (2,3-dimethoxyphenyl) -N, N-dimethylmethaneamine (2.00 g) and ethyl 5-bromopentanoate (2.79 g) was stirred at 80 ° C. for 3 hours. By purifying this with reverse phase column chromatography (developing solvent; water-acetonitrile), N-[(2,3-dimethoxyphenyl) methyl] -5-ethoxy-N, N-dimethyl-5-oxopentane- 1-Aminium = bromide (3.91 g) was obtained.
[0141]
Production Example 17
　3- (2-fluoro-4,5-dimethoxyanilino) propan-1-sulfonic acid (4.00 g), potassium carbonate (4.52 g), methyl iodide (7.7 mL), methanol (60 mL) ) Was stirred at 50 ° C. overnight. After allowing to cool to room temperature, it is concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and freeze-dried to 3-[(2-fluoro-4,5-dimethoxyphenyl) (dimethyl). Azaniumyl] Propane-1-sulfonate (4.34 g) was obtained.
[0142]
Production Example 18
　3- (3,4-dimethoxyanilino) propan-1-sulfonic acid (2.00 g), 1,4-diiodobutane (1.04 mL), potassium carbonate (2.21 g), dioxane (30 mL), The mixture of water (15 mL) was stirred at 100 ° C. overnight. After allowing to cool to room temperature, concentrate, purify by reverse phase column chromatography (developing solvent: acetonitrile-water), and freeze-dry to 3- [1- (3,4-dimethoxyphenyl) pyrrolidine-1-ium. -1-Il] Propane-1-sulfonate (2.37 g) was obtained.
[0143]
Production Example 19
　A mixture of 3- (3,4-dimethoxyanilino) propan-1-sulfonic acid (2.00 g), ethyl iodide (2.94 mL), potassium carbonate (2.41 g), and methanol (30 mL). The mixture was stirred at 50 ° C. overnight. Methyl iodide (4.1 mL) was added and the mixture was subsequently stirred at 50 ° C. overnight. After allowing to cool to room temperature, it is concentrated, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and freeze-dried to 3-[(3,4-dimethoxyphenyl) (ethyl) (methyl) azaniumyl. ] Propane-1-sulfonate (2.14 g) was obtained.
[0144]
Production Example 20
　3-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} propan-1-sulfonate (5.41 g), 57% hydroiodide (24 mL) mixture at 110 ° C. for 15 hours Stirred. After allowing to cool to room temperature, water (30 mL) was added and concentrated under reduced pressure. This operation was repeated once again. Water (6 mL) was added to this to dissolve it, then acetone (100 mL) was added, and the mixture was stirred under an ice bath for 3 minutes. After allowing to stand, the supernatant was removed by decantation. Further, water (6 mL) and acetone (75 mL) were added, and the same operation was performed again. Water (6 mL) and acetone (75 mL) were added to this, and after stirring for 3 minutes under an ice bath, the solid was collected by filtration, washed with acetone, dried under reduced pressure, and 3-{[(2,3-dihydroxyphenyl). Methyl] (dimethyl) azanium-yl} propan-1-sulfonate (5.02 g) was obtained.
[0145]
Production Example 21
　Under an argon atmosphere and under cooling in a dry ice-acetone bath, 3-{[(2,3-dimethoxyphenyl) methyl] bis (2-methoxyethyl) azaniumyl} propan-1-sulfonate (2.59 g), dichloromethane ( A 1 mol / L boron tribromide dichloromethane solution (19.2 mL) was added dropwise to the mixture of 52 mL), the temperature was slowly raised to room temperature over 3 hours, and the mixture was stirred at room temperature for 2 hours. Methanol was added under ice-cooling, and the mixture was stirred at room temperature for 30 minutes and concentrated under reduced pressure. Methanol was added to the residue and the mixture was concentrated again under reduced pressure. This operation is performed twice later, purified by reverse phase column chromatography (developing solvent: acetonitrile-water), and lyophilized by 3-{[(2,3-dihydroxyphenyl) methyl] bis (2-methoxy). Ethyl) azaniumyl} propan-1-sulfonate (674 mg) was obtained.
[0146]
Production Example 22
　A mixture of 4-{[(2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate (2.28 g) and 57% hydroiodide (9.6 mL) at 110 ° C. The mixture was stirred for 4 hours. After allowing to cool to room temperature, water was added and the mixture was concentrated under reduced pressure. This operation was repeated once more. Water (4 mL) was added to this to dissolve it, and then acetone (80 mL) was added, and the mixture was stirred and allowed to stand, and then the supernatant was removed by decantation. Further, millipore water (4 mL) and acetone (60 mL) were added, and the same operation was performed. Millipore water (4 mL) and acetone (60 mL) are added to this, and after stirring, the solid is collected by filtration, washed with acetone, dried under reduced pressure, and 4-{[(2,3-dihydroxyphenyl) methyl] ( Dimethyl) azaniumyl} butane-1-sulfonate (2.45 g) was obtained.
[0147]
Production Example 23
　3-{[(6-fluoro-2,3-dimethoxyphenyl) methyl] (dimethyl) azaniumyl} Propane-1-sulfonate (1.79 g), 57% hydroiodic acid (7.5 mL) mixture Was stirred at 110 ° C. for 6 hours. After allowing to cool to room temperature, water was added and the mixture was concentrated under reduced pressure. This operation was repeated once again. Acetone (70 mL) was added thereto, and the mixture was stirred under ice-cooling. After allowing to stand overnight to precipitate a solid, the mixture was stirred under ice-cooling for 1 hour. After allowing to stand, the supernatant was removed by decantation. After adding acetone to this, the solid was collected by filtration, washed with acetone, dried under reduced pressure, and 3-{[(6-fluoro-2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} propane-1. -Sulfonate (1.58 g) was obtained.
[0148]
Production Example 24
　3- (diethoxyphosphoryl) -N-[(2,3-dimethoxyphenyl) methyl] -N, N-dimethylpropan-1-aminium = bromide (2.80 g), 57% hydroiodic acid ( 8 mL) of the mixture was stirred at 100 ° C. for 18 hours. After allowing to cool to room temperature, water and acetone were added, and the mixture was concentrated under reduced pressure. Water was added thereto, and the mixture was concentrated under reduced pressure. Water was added thereto, the insoluble material was filtered off, and the filtrate was concentrated under reduced pressure. Acetone was added to this, and the resulting solid was filtered. This was washed with acetone and dried under reduced pressure to obtain N-[(2,3-dihydroxyphenyl) methyl] -N, N-dimethyl-3-phosphonopropane-1-aminium-iodide (571 mg).

WE CLAIMS

[Claim 1 Nanoparticles containing iron oxide-containing metal particles to which one or more zwitterionic ligands represented by the formula (I) are coordinated.
[Chemical

formula 1] (In the formula, one of
R 1 and R 2 is a group represented by the formula (a) or the formula (b), and the other is H, a lower alkyl, an —O- lower alkyl or a halogen. ,
[Chemical formula 2]

X 1 may be a bond or methylene, and X 1 may be ethylene when R 1 is a group represented by the formula (a), and X 2 may be substituted with OH. When a good C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene - and R 1 is a group represented by the formula (b), X 2 may be a bond. , R A and R B

Are the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are with the quaternary nitrogen atom to which they are attached. to form a 5- or 6-membered nitrogen-containing saturated heterocyclic ring
together, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, It is H, C 1-3 alkyl, -OC 1-3 alkyl or halogen,
n is an integer of 0 to 2
, and
i) R 1 is a group represented by the formula (a), and , X 1When is methylene, R 2 and Ra or R b may be integrated to form ethylene,
ii) R 1 is a group represented by the formula (a), and X 1 is ethylene. When, R 2 and Ra or R b may be integrated to form methylene, and
iii) R 2 is a group represented by the formula (a), and X 1 is methylene. At some point, R 3 and Ra or R b may be integrated to form ethylene,
where R 2 is the group represented by formula (a) and R a and R b are methyl. , X 1 is a bond and X 2There, C 1-4 alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
[Claim 2]
　In the zwitterionic ligand, one of
R 1 and R 2 is a group represented by the formula (a) or the formula (b), the other is H, a lower alkyl or halogen, and
X 1 is a bond or methylene. Further, when R 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 may be C 1-5 alkylene substituted with OH , or -C 1 -2 alkylene -O-C 1-3 alkylene - and further R 1 X when groups are represented by the formula (b) 2 may be a
binding, R a and R b are same or different from each other C 1-3 alkyl, -C 1-3 alkylene-OC 1-2Alkyl, or, R a and R b are, they become a quaternary nitrogen atom to which attached form a pyrrolidine
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - in
and, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, or halogen,
n is 1,
further,
i) R 1 group is represented by formula (a) The nanoparticles according to claim 1, which are zwitterionic ligands , wherein R 2 and Ra or R b may be integrated to form ethylene when X 1 is methylene .
[Claim 3]
　In the zwitterionic ligand,
R 1 is the group represented by the formula (a) or the formula (b), R 2 is H or halogen,
X 1 is bound or methylene, and R 1 is further. When the group is represented by the formula (a), X 1 may be ethylene,
X 2 is C 1-5 alkylene, and when R 1 is the group represented by the formula (b), X 2 is bonded. may also
be, R a and R b are both
methyl, Y - is SO 3 - or, CO 2 - and is,
nanoparticles of claim 2 wherein the zwitterionic ligands.
[Claim 4]
Claims that the zwitterionic ligand is a zwitterionic ligand in which one of 　R 1 and R 2 is the group represented by the formula (a) and the other is H, lower alkyl, -O-lower alkyl or halogen. Item 1. The nanoparticles according to Item 1.
[Claim 5]
　The zwitterionic ligand is
1) a zwitterionic ligand in which R 1 is the group represented by the formula (a) and R 2 is H, lower alkyl, -O-lower alkyl or halogen, or ,
2) A zwitterionic ligand in which R 1 is H, R 2 is the group represented by formula (a), R 3 is C 1-3 alkyl or halogen, and R 4 is H.
The nanoparticle according to claim 4.
[Claim 6]
　5. The zwitterionic ligand is a zwitterionic ligand in which R 1 is the group represented by the formula (a) and R 2 is H, a lower alkyl, an —O- lower alkyl or a halogen. The nanoparticles described.
[Claim 7]
　Zwitterionic
ligands, R 2 is H or
halogen, X 1 is a bond, methylene or
ethylene, X 2 is C 2-4
alkylene, R a and R b both are
methyl, R When 3 and R 4 are the same or different from each other and are H, C 1-3 alkyl or halogen, and when
X 1 is methylene, R 2 and Ra or R b are integrated to form ethylene.
The nanoparticles according to claim 6, which may be zwitterionic ligands.
[Claim 8]
　Zwitterionic ligands,
R 2 is is H or F,
X 2 is ethylene or propylene,
R 3 and R 4 both are H,
a zwitterionic ligands, nanoparticles of claim 7, wherein ..
[Claim 9]
Zwitterionic ligands,
R 2 is is H,
X 1 is a bond or ethylene,
zwitterionic ligands, nanoparticles of claim 8.
[Claim 10]
　Zwitterionic
ligands, Y - is SO 3 - or CO 2 - in which,
a zwitterionic ligands, nanoparticles according to any one of claims 4-9.
[Claim 11]
　In the zwitterionic ligand,
R 1 is the group represented by the following formula (b-1),
[Chemical Formula 3]

R 2 is H or halogen,
X 1 is bound or methylene, and
X 2 is, C 1-5 alkylene or a
bond, R a is
methyl, Y - is SO 3 - , or, CO 2 - and is,
zwitterionic ligands, nanoparticles of claim 3.
[Claim 12]
　The nanoparticles according to any one of claims 1 to 11, wherein the metal particles containing iron oxide are metal particles containing only iron oxide.
[Claim 13]
　Nanoparticles are particles formed by coordination-bonding one or more twin ion ligands to the outer surface of metal particles containing iron oxide, and the metal particles are coated with the twin ion ligands. The nanoparticle according to any one of claims 1 to 12, which is a nanoparticle.
[Claim 14]
　Any of claims 1 to 12, wherein the nanoparticles are a complex consisting of iron oxide-containing metal particles to which one or more biionic ligands are coordinated and one or more biionic ligands. Or the nanoparticles according to item 1.
[Claim 15]
　Nanoparticles,
2 or more zwitterionic ligand compounds, and two or more "one or more zwitterionic metal particles ionic ligand compound contains iron oxide bound coordination" is a cluster of claim The nanoparticle according to any one of 1 to 12.
[Claim 16]
　A contrast agent for magnetic resonance imaging, which comprises the nanoparticles according to any one of claims 1 to 15.
[Claim 17]
　The contrast medium for magnetic resonance imaging according to claim 16, which is a positive contrast medium.
[Claim 18]
　Use of a zwitterionic ligand compound represented by the following formula (I) for producing the nanoparticles according to claim 1.
[Chemical

formula 4] (In the formula, one of
R 1 and R 2 is a group represented by the following formula (a) or formula (b), and the other is H, lower alkyl, -O-lower alkyl or halogen. Yes,
[Chemical 5]

X 1 is a bond or methylene, and when R 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 is substituted with OH. It may be C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene-, and when R 1 is a group represented by the formula (b), X 2 may be a bond.
well, R A and R BAre the same or different from each other, C 1-3 alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are with the quaternary nitrogen atom to which they are attached. to form a 5- or 6-membered nitrogen-containing saturated heterocyclic ring
together, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, It is H, C 1-3 alkyl, -OC 1-3 alkyl or halogen,
n is an integer of 0 to 2
, and
i) R 1 is a group represented by the formula (a), and , X 1When is methylene, R 2 and Ra or R b may be integrated to form ethylene,
ii) R 1 is a group represented by the formula (a), and X 1 is ethylene. When, R 2 and Ra or R b may be integrated to form methylene, and
iii) R 2 is a group represented by the formula (a), and X 1 is methylene. At some point, R 3 and Ra or R b may be integrated to form ethylene,
where R 2 is the group represented by formula (a) and R a and R b are methyl. , X 1 is a bond and X 2There, C 1-4 alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
[Claim 19]
　The zwitterionic ligand compound is a zwitterionic ligand compound in which one of R 1 and R 2 is the group represented by the formula (a) and the other is H, lower alkyl, -O-lower alkyl or halogen. The use according to claim 18.
[Claim 20]
　A compound represented by the following formula (I) or a salt thereof.
[Chemical

formula 6] (In the formula, one of
R 1 and R 2 is a group represented by the following formula (a) or formula (b), and the other is H, lower alkyl, -O-lower alkyl or halogen. Yes,
[Chemical 7]

X 1 is a bond or methylene, and when R 1 is a group represented by the formula (a), X 1 may be ethylene, and
X 2 is substituted with OH. It may be C 1-5 alkylene or -C 1-2 alkylene-OC 1-3 alkylene-, and when R 1 is a group represented by the formula (b), X 2 may be a bond.
well, R a and R b are the same or different from each other, C 1-3Alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or Ra and R b are 5- or 6-membered nitrogen-containing saturated heteros integrated with the quaternary nitrogen atom to which they are attached. forms a
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 are the same or different from each other, H, C 1-3 alkyl, -O-C When 1-3 alkyl or halogen,
n is an integer of 0 to 2
,
i) R 1 is the group represented by the formula (a), and X 1 is methylene, then R 2 and R A or R b may be integrated to form ethylene, and
ii) when R 1 is a group represented by the formula (a) and X 1 is ethylene, R 2 and Ra or R b may be integrated to form methylene, and when
iii) R 2 is a group represented by the formula (a) and X 1 is methylene, R 3 and Ra or R Ethylene may be formed integrally with b ,
except that R 2 is a group represented by the formula (a), Ra and R b are methyl, X 1 is a bond, and X 2 But C 1-4Alkylene, and, R 1 , R 3 and R 4 when the both are H, Y - is HPO 3 - , or, CO 2 - is. )
[Claim 21]
　One of R 1 and R 2 is a group represented by the formula (a) or the formula (b), the other is H, a lower alkyl or halogen,
X 1 is a bond or methylene, and R 1 When is a group represented by the formula (a), X 1 may be ethylene, and
X 2 may be substituted with OH C 1-5 alkylene or -C 1-2 alkylene-O-. C 1-3 alkylene - and further R 1 X when groups are represented by the formula (b) 2 may be a
binding, R a and R b are the same or different from each other, C 1-3 Alkyl, -C 1-3 alkylene-OC 1-2 alkyl, or R a and R b are, they, together with the quaternary nitrogen atom attached to form a pyrrolidine
ring, Y - is SO 3 - , HPO 3 - , or, CO 2 - and
is, R 3 and R 4 Are the same or different from each other, H, C 1-3 alkyl, or halogen,
n is 1, and
i) R 1 is the group represented by the formula (a), and X 1 is. The compound according to claim 20, or a salt thereof, wherein when it is methylene, R 2 and Ra or R b may be integrated to form ethylene
.
[Claim 22]
　R 1 is the group represented by the formula (a) or the formula (b), R 2 is H or the halogen,
X 1 is the bond or methylene, and R 1 is represented by the formula (a). X 1 may be ethylene,
X 2 may be C 1-5 alkylene, and X 2 may be a bond when R 1 is a group represented by the formula (b) . R a and R b are both methyl, Y - is SO 3 - or, CO 2 - and is, compound or its salt according to claim 21, wherein.

[Claim 23]
The compound according to claim 20, or a salt thereof, wherein one of 　R 1 and R 2 is a group represented by the formula (a) and the other is H, a lower alkyl, an —O— lower alkyl or a halogen.
[Claim 24]
　4-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate,
3-{[(6-fluoro-2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} propane- 1-sulfonate,
hydrogen = (3-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} propyl) phosphonate,
5-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} penta Noart,
{1-[(2,3-dihydroxyphenyl) methyl] -1-methylpiperidin-1-ium-4-yl} acetate,
1-[(2,3-dihydroxyphenyl) methyl] -1-methyl Piperidine-1-ium-4-carboxylate,
4-{[2- (2,3-dihydroxyphenyl) ethyl] (dimethyl) azaniumyl} butanoate,
2-{[2- (2,3-dihydroxyphenyl) ethyl] The compound according to claim 20, or a salt thereof, selected from the group consisting of (dimethyl) azaniumyl} ethane-1-sulfonate and
3-[(2,3-dihydroxyphenyl) (dimethyl) azaniumyl] propan-1-sulfonate
.
[Claim 25]
　{1-[(2,3-dihydroxyphenyl) methyl] -1-methylpiperidin-1-ium-4-yl} acetate, and
2-{[2- (2,3-dihydroxyphenyl) ethyl] (dimethyl)
The compound according to claim 24 or a salt thereof selected from the group consisting of azaniumyl} ethane-1-sulfonate .
[Claim 26]
　4-{[(2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} butane-1-sulfonate, and
3-{[(6-fluoro-2,3-dihydroxyphenyl) methyl] (dimethyl) azaniumyl} propane
The compound according to claim 24 or a salt thereof selected from the group consisting of -1-sulfonate .