WO2015025947A1

WO2015025947A1 - Magnetic resonance imaging contrast agent

Info

Publication number: WO2015025947A1
Application number: PCT/JP2014/071970
Authority: WO
Inventors: 芳親吉岡; 審良　静男; 石井　健; ジェヴァイアチョバン
Original assignee: 国立大学法人大阪大学
Priority date: 2013-08-23
Filing date: 2014-08-22
Publication date: 2015-02-26
Also published as: JPWO2015025947A1; JP6084294B2

Abstract

The objective of the present invention is to provide a magnetic resonance imaging contrast agent which contains a novel active ingredient. Provided is a magnetic resonance imaging contrast agent which contains an iron (III) porphyrin complex or a compound that is modified with an iron (III) porphyrin complex.

Description

Magnetic resonance contrast agent

The present invention relates to a magnetic resonance contrast agent.

The magnetic resonance method is indispensable in the medical field because it can capture a detailed and high-contrast image into the living body non-invasively like an MRI apparatus as a clinical diagnostic machine. Furthermore, it has been applied to molecular imaging in pharmaceuticals, basic research, etc., and the number of nuclear magnetic resonance apparatuses has increased dramatically. The number of domestic 3T (128 MHz) clinical devices has already exceeded 170 at the present time, 1.5T (64 MHz) exceeds 2800, and if animal devices are added, the number becomes very large.

In magnetic resonance imaging of living organisms, the sensitivity of hardware and software has been improved, the contrast of tissue images has been improved using contrast agents, and the diagnostic performance has been improved by looking at tissue information and its characteristics in detail. It was. In recent years, not only the improvement of tissue contrast of inflammation, cancer, tumors, etc. by simple MRI sequences, but also gadolinium compounds that are generally positive contrast agents, various magnetic substances that become positive and negative contrast agents depending on the concentration, etc. Attempts to improve the imaging contrast used and molecular imaging are progressing steadily (Non-Patent Documents 1 to 8).

Clinically approved and used are gadolinium compounds and super magnetic iron oxide (SPIO) (Non-Patent Documents 1 to 3).

As for gadolinium compounds, diagnostic applications utilizing characteristics such as angiography, non-selective accumulation, and invasion between tissues have been promoted. However, imaging close to the cellular level is difficult and kidney toxicity has been reported. So far, biodegradable gadolinium compounds have been proposed, but gadolinium itself is toxic, and long-term follow-up and clinical application are not possible (Non-patent Document 7).

In addition, magnetic particles have been used for drawing vascular plaque, image diagnosis of liver cancer, evaluation of lymph node metastasis of cancer, etc., and identification with high resolution is possible (Non-patent Document 4). Since magnetic particles are iron agents, they are considered to have a high affinity in the living body, and their toxicity has not been sufficiently studied. Since magnetic particles exist in the living body for a relatively long period of time, they cannot be used repeatedly to track the therapeutic effect. It has been shown that even in humans, even after half a year to one year after administration, it remains in the organ to the extent that the image is affected (Non-patent Document 8). Therefore, it has been desired to develop a contrast medium that can track the therapeutic effect in a short period of time.

An object of the present invention is to provide a magnetic resonance contrast agent containing a new active ingredient.

As a result of intensive studies to solve the above problems, the present inventors have found that the porphyrin iron (III) complex has MRI contrast ability. The present invention has been completed based on such findings, and widely encompasses the inventions described below.
Item 1. A magnetic resonance contrast agent comprising a porphyrin iron (III) complex and / or a compound modified by the porphyrin iron (III) complex.
Item 2. The magnetic resonance contrast agent according to Item 1, wherein the porphyrin iron (III) complex is a compound represented by the following formula (1) or a derivative thereof:

(Wherein X is a halogen atom or OH;
R ₁ to R ₈ are the same or different and each represents a hydrogen atom, a carboxyl group, an acetyl group, an amino group, a thiol group, a sulfo group, a sulfonyl group, a phosphinyl group, a phosphino group, or a phosphono group; A lower alkyl group, a lower alkoxy group, or a lower alkylene group which may have an amino group, a thiol group, a sulfo group, a sulfonyl group, a phosphinyl group, a phosphino group, or a phosphono group. ).
Item 3. The magnetic resonance imaging agent according to

Item

1 or 2, wherein the porphyrin iron (III) complex is β-hematin or a derivative thereof.
Item 4. The magnetic resonance contrast agent according to any one of Items 1 to 3, wherein the porphyrin iron (III) complex is a crystal.
Item 5 The magnetic resonance contrast agent according to Item 4, wherein the particle size distribution of the crystal is 5 nm to 3 μm. Item 6 The magnetic resonance contrast agent according to Item 4 or 5, wherein a particle size distribution of the crystal is 50 nm to 1.5 μm.
Item 7 Items 1 to 6
A magnetic resonance contrast kit comprising the magnetic resonance contrast agent according to any one of the above.
Item 8. A magnetic resonance imaging method including a step of acquiring a magnetic resonance signal by applying an excitation magnetic field pulse to a subject to which the magnetic resonance contrast agent according to any one of Items 1 to 6 is administered.

The magnetic resonance contrast agent of the present invention exhibits a contrast ability that can be sufficiently used for magnetic resonance imaging using an MRI apparatus or the like as a clinical diagnostic machine. Such an imaging ability is a very excellent effect showing a resolution that can be recognized at the cellular level.

The magnetic resonance contrast kit of the present invention contains the magnetic resonance contrast agent of the present invention as a constituent element, and exhibits excellent effects similar to the magnetic resonance contrast agent of the present invention as described above.

The magnetic resonance imaging method of the present invention uses the magnetic resonance contrast agent of the present invention, and this also exhibits excellent effects similar to the magnetic resonance contrast agent of the present invention as described above.

The figure which shows the experimental result which measured the particle diameter distribution of the synthetic hemozoin contained in the magnetic resonance contrast agent used in the Example of this invention. The magnetic resonance image in the mouse liver of Experimental example 1 is shown. (A) shows the result using the conventional contrast agent, and (B) shows the result using the magnetic resonance contrast agent of the present invention. The experimental result which administered the magnetic resonance contrast agent of this invention to the mouse | mouth subcutaneous of Experimental example 2 is shown. (A) shows the results for one day after administration, and (B) shows the results for four weeks after administration. The experiment result which was the phantom of Experimental example 3 and confirmed the contrast effect of the magnetic resonance contrast agent of this invention. Hemozone in PBS shows the results with the magnetic resonance contrast agent of the present invention, and Saline (saline) and PBS show control experiments. The magnetic resonance image of the mouse | mouth chest vicinity of Experimental example 4 is shown. (A) is an image immediately after the magnetic resonance contrast medium of the present invention is administered subcutaneously to the back of the mouse, (B) is one week after administration, and (C) is an image four weeks after administration. The magnetic resonance image of the mouse | mouth chest vicinity of Experimental example 4 (control experiment) is shown. (A) is an image immediately after the conventional contrast agent is administered subcutaneously to the back of the mouse, (B) is one week after administration, (C) is four weeks after administration, and (D) is an image five weeks after administration. . The experiment result of visualization of the cell level using the magnetic resonance contrast agent of this invention of Experimental example 5 is shown. Macrophage (hemozoin) indicates macrophages phagocytosed with the magnetic resonance contrast agent of the present invention, and Macrophage and Saline (saline) indicating macrophages that have not phagocytosed indicate control experiments.

<Magnetic resonance contrast agent>
The magnetic resonance contrast agent of the present invention contains a porphyrin iron (III) complex and / or a compound modified with the porphyrin iron (III) complex as an active ingredient.

Porphyrin iron (III) complex is a core of a porphyrin complex whose central metal is trivalent iron (the following formula (2))

(In the above formula, X is a halogen atom or OH.) Since this mother nucleus has trivalent iron at the center, it has a good MRI contrast capability.

Porphyrin iron (III) complexes that can be used in the present invention include those further modified with the mother nucleus at the center as long as the MRI contrast ability is not hindered.

The porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention is not particularly limited, and examples thereof include a compound represented by the following formula (1).

In the above formula, X is a halogen atom or OH. R ₁ to R ₈ are the same or different and each represents a hydrogen atom, an acetyl group, an amide group, an amino group, an epoxy group, a carboxyl group, a cyano group, a sulfo group, a thiol group, a hydroxyl group, a phosphinyl group, a phosphino group, or a phosphono group. Having an acetyl group, an amide group, an amino group, an epoxy group, a carboxyl group, a cyano group, a sulfo group, a thiol group, a hydroxyl group, a phosphinyl group, a phosphino group, a phosphono group, or a formyl group. Or a lower alkyl group, a lower alkoxyl group, or a lower alkenyl group.

The halogen is not particularly limited, but preferably includes a fluorine atom, a chlorine atom, a bromine atom and the like.

OH is synonymous with hydroxyl group or hydroxyl group.

The alkyl group, alkoxy group and alkylene group may be linear or have a branched structure.

The term “lower” is not particularly limited, but has about 1 to 8 carbon atoms, more preferably about 1 to 6, more preferably about 1 to 4, and most preferably 1 or 2.

Although it does not specifically limit with the compound modified by the porphyrin iron (III) complex, For example, it is an in-vivo molecule | numerator, such as an antibody and a lectin, and it bind | bond | couples with the target molecule in in vivo with specificity or high selectivity. The compound which has capability is mentioned.

The antibody is not particularly limited, and an antibody having an immunoglobulin structure such as IgA, IgG, IgE, IgD, IgM; a fragment having a structure such as Fab, F (ab) ′ ₂ , Fv, scFv Multimer such as these fragmented antibodies, multivalent antibodies, bispecific antibodies, short chain antibodies, fusion antibodies and the like.

Lectins include agglutinin, hemagglutinin, phytohemagglutinin, selectin and the like, and are not particularly limited.

In addition, these compounds may be directly modified with the above porphyrin iron (III) complex, or may be modified via a linker. Specific linkers are not particularly limited, and examples thereof include polyalkylene glycol which may have a functional group such as a succinimidyl group and a maleimide group.

The porphyrin iron (III) complex is preferably one exhibiting low toxicity to the living body and low retention in the living body. By using a porphyrin iron (III) complex having these characteristics, it is possible to repeatedly use it in a short period of time for tracking the therapeutic effect.

The porphyrin iron (III) complex having such excellent characteristics is not particularly limited, and examples thereof include β-hematin or a derivative thereof. β-hematin is a substance derived from a living body and exhibits the above-described characteristics. The structure of β-hematin is as follows: in the above chemical formula (1), X is OH; R ₁ and R ₂ are linear alkyl groups having 4 carbon atoms having a carboxyl group at the end; R ₃ , R ₄ , R ₆ , And R ₈ is a methyl group; and R ₅ and R ₇ are vinyl groups.

The β-hematin derivative is not particularly limited. For example, it has low toxicity to the living body as described above, has low in vivo retention, and exhibits sufficient imaging ability when used for magnetic resonance imaging. To the appropriate site of β-hematin, acetylation, amidation, amination, epoxidation, carboxylation, cyanation, sulfonation, thiolation, hydroxylation, phosphinylation, phosphinolation, phosphonolation, formyl Β-hematin derivatives in which various functional groups are appropriately introduced by derivatization, alkylation, alkenylation, halogenation, etc .; for β-hematin, at least one ribulose, xylulose, ribose, arabinose, xylose, lyxose, deoxyribose, etc. Pentose sugar and / or psicose, fructose, sorbose, tagatose, Β-hematin derivatives (also referred to as β-hematin glycosides) to which hexose sugars such as loose, altrose, glucose, mannose, gulose, idose, galactose, talose, fucose, fucose, rhamnose and the like are added; polyethylene glycol, polypropylene glycol And β-hematin derivatives (also referred to as β-hematin inclusion bodies) which are included by polyalkylene glycol such as cyclodextrin, albumin and the like.

The porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention described above may be contained in a solution state or a crystal state, and is not particularly limited. From the viewpoint of exhibiting higher contrast ability when used as an agent, it is preferably contained in a crystalline state. In particular, among the β-hematin crystals exemplified as the porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention, there is a crystal called hemozoin as a naturally occurring crystal, which is produced by chemical synthesis. Also called synthetic hemozoin.

Such a porphyrin iron (III) complex is included in a crystalline state as a magnetic resonance contrast agent, even if it is in the form of a powder or the like as it is, it is in a state of being dispersed or suspended in a liquid, It may be in the form of a suspension or the like, and is not particularly limited.

The specific crystal size that can be used in a living body is about 5 nm to 3 μm as in the case of a general contrast agent. When a crystal of several nanometers to several tens of nanometers is injected intravenously, it stays in the blood for a relatively long time, which is advantageous for imaging of slow-uptake cells and tissues. Intravenous injection of crystals of about 50 nm to 1500 nm is advantageous for imaging of liver, spleen, bone marrow, lymphoid tissue and the like. Intravenous injection of crystals of about 3 μm is advantageous for long-term imaging of blood vessels. Immediate imaging of peripheral lymph nodes is possible by subcutaneous administration of crystals of 100 nm or less. In addition, by administering a crystal of about 1 μm subcutaneously, only subcutaneous phagocytic cells can be labeled, and movement of phagocytic cells to regional lymph nodes can be traced. A more detailed biological reaction can be evaluated by appropriately using crystals having a uniform particle size.

Such particle size distribution is measured by a known method based on a dynamic light scattering method (laser diffraction / scattering method). The measurement method using the dynamic light scattering method is to suspend a porphyrin iron (III) complex by subjecting it to an ultrasonic treatment in water for 20 minutes, and then suspending it by using Shimadzu Corporation: SALD-2200 or an equivalent device. It is a method to measure using.

The porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention can be produced using a known method. Moreover, you may use what is marketed. A specific production method may be produced by bringing porphyrin or a derivative thereof into contact with a solution containing trivalent iron and appropriately performing treatments such as heating and refluxing. The obtained porphyrin iron (III) complex may be subjected to a known purification step such as recrystallization or chromatography as required. Furthermore, the process of making it contact with a halogen ion in the environment set to appropriate pH may be included.

As another method, a porphyrin iron (III) complex typified by heme contained in a living body is extracted by a known method, and the above-described known method is appropriately used as a raw material, so that the magnetic resonance of the present invention is performed. A porphyrin iron (III) complex contained in the contrast agent may be produced.

Further, when the porphyrin iron (III) complex contained in the magnetic image resonance contrast agent of the present invention is in a crystalline state, the iron (III) complex is crystallized by a known method, and further its particle size is determined by a known method. It is also possible to adjust the distribution.

The method for producing the compound modified with the porphyrin iron (III) complex is not particularly limited. For example, the porphyrin iron (III) complex produced or obtained by the above-described method and the above-described compound may be combined with a linker as necessary. Can be modified by known methods.

As a method for producing a porphyrin iron (III) complex, for example, if it is a method for obtaining or producing β-hematin or a derivative thereof, Doolan, D. et al. L. , Clin. Microbiol. Rev. 22, 13-36, Table (2009), Good, M .; F. , Eur. J. et al. Immunol. 39, 939-943 (2009); Coban, C .; et al. , Trends Microbiol. 15, 271-278 (2007), Joffre, O .; et al. , Immunol. Rev. 227, 234-247 (2009) and the like can be employed.

The content of the porphyrin iron (III) complex and / or the compound modified by the porphyrin iron (III) complex in the magnetic resonance contrast agent of the present invention is not particularly limited, but is 100 parts by weight of the magnetic resonance contrast agent. On the other hand, it is usually about 0.0001 to 100 parts by weight. That is, the porphyrin iron (III) complex and / or the compound itself modified by the porphyrin iron (III) complex may be used as the magnetic resonance contrast agent of the present invention.

For example, if the above-mentioned compound is a tissue-specific antibody, it can be provided in the blood to administer a contrast agent that can be imaged in a site-specific manner.

Note that the magnetic resonance contrast agent of the present invention may contain other components. Such components include pH adjusters, buffers, preservatives, isotonic agents, preservatives and the like.

The dosage form of the magnetic resonance contrast agent of the present invention is not particularly limited, but in view of the dosage, administration method and the like as described below, the desired dosage form together with various known pharmaceutically acceptable carriers. do it. Specific dosage forms include injections, dialysis agents, capsules, granules, powders, oral solutions, syrups, oral jelly agents, oral tablets, oral sprays, semisolid oral preparations, and gargles , Inhalants, eye drops, ear drops, nasal drops, suppositories, rectal semi-solid preparations, enemas, vaginal tablets, vaginal suppositories, external solid preparations, external liquid preparations, sprays, ointments, creams Agents, gels, patches and the like.

The above-mentioned injection includes, for example, an infusion, an implantable injection, a continuous injection and the like. Examples of the dialysis agent include a peritoneal dialysis agent and a hemodialysis agent.

Examples of the above-mentioned tablets include orally disintegrating tablets, chewable tablets, effervescent tablets, dispersible tablets, and dissolving tablets. Examples of the capsule include hard capsules and soft capsules. Examples of the granules include foamed granules, sustained-release granules, enteric granules, and the like. Examples of the oral solution include elixirs, suspensions, emulsions, and limonades. The above syrup preparations include, for example, syrup preparations. Examples of the oral tablet include troches, sublingual tablets, buccal tablets, adhesive tablets, gums and the like. The above inhalants include, for example, inhalation powders, inhalation solutions, inhalation aerosols and the like. The above eye drops include, for example, eye ointments and the like. Examples of the nasal drops include nasal powders and nasal drops.
The above-mentioned external solid preparation includes, for example, an external powder. The above-mentioned external liquid preparation includes, for example, a liniment and a lotion. The above-mentioned sprays include, for example, external aerosols and pump sprays. The above-mentioned patch includes, for example, a tape and a poultice.

These dosage forms can be manufactured based on known documents such as the 16th revised Japanese Pharmacopoeia Manual.

In addition, the above-mentioned components are not particularly limited, and for example, in the case of injections, solvents, stabilizers, preservatives, solubilizers, local anesthetics, soothing agents, buffer suspending agents and the like can be mentioned.

The above-mentioned solvents include, for example, water for injection, sesame oil, soybean oil, corn oil, olive oil and the like. Examples of the stabilizer include an inert gas, a chelating agent, and a reducing substance. Here, the inert gas includes nitrogen, carbon dioxide, and the like; the chelating agent includes EDTA, thioglycolic acid, and the like; and the reducing substance includes sodium bisulfite, L-ascorbic acid, and the like. Examples of the above-mentioned preservative include paraoxybenzoic acid ester, chlorobutanol, benzyl alcohol, phenol, benzalkonium chloride and the like. Examples of the above-described solubilizer include a binding solubilizer and a solvent-soluble solubilizer. Here, the binding solubilizer includes sodium iodide, sodium benzoate, sodium nicotinate and the like; the solvent-soluble solubilizer includes alcohol, propylene glycol, liquid macrogol and the like. Examples of the surfactant include hydrogenated castor oil for injection, polysorbate 80, polysorbate 20, and the like. The above-mentioned soothing agents include local anesthetics, glucose, sorbitol, amino acids and the like. Here, local anesthetics include procaine hydrochloride, benzyl alcohol and the like. The aforementioned buffering agents include citric acid, acetic acid, sodium phosphate salt, and those for injection. Examples of the suspending agent include carmellose sodium, PVP, aluminum monostearate, and suspending agents such as those for injection.

The dosage of the magnetic resonance contrast agent of the present invention is not particularly limited, and is in consideration of the dosage form, administration method, site of magnetic resonance imaging, purpose, sex of individual to be administered, age, weight, etc. These may be set as appropriate. Specifically, in terms of the amount of the porphyrin iron (III) complex and / or the compound modified by the porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention, usually 1 to 100 mmol / kg. It should be about.

The administration within the above numerical range is safe. For example, in the pamphlet of International Publication No. 2011/0774711 in which a porphyrin iron (III) complex of the present invention and / or a synthetic hemozoin corresponding to a compound modified with the porphyrin iron (III) complex is used as an adjuvant is described. It has been shown that this can be administered subcutaneously or intraperitoneally on the order of mmol per kg.

The administration method of the magnetic resonance contrast agent of the present invention is not particularly limited, and may be appropriately selected in view of the site, purpose, dose, dosage form, etc. of magnetic resonance imaging. Specifically, oral administration, intravenous administration, lymphatic administration, nasal administration, otic administration, transmucosal administration, transdermal administration, rectal administration, vaginal administration, epidural administration, intramuscular administration, subcutaneous Administration, intraosseous administration, subarachnoid administration, intraperitoneal administration, intravitreal administration, intravesical administration, and the like.

In addition, as a method of administering to a cell, it is possible to simply contact a desired cell with a magnetic resonance contrast agent containing the porphyrin iron (III) complex of the present invention, and a method using a known cell introduction agent. Electroporation method, French press method, virus infection method and the like may be appropriately combined.

An apparatus capable of performing magnetic resonance imaging using the magnetic resonance contrast agent of the present invention is not particularly limited, and examples thereof include an open type and a tunnel type MRI apparatus that can usually be imaged in the T2-weighted mode. Moreover, when imaging a cell, MRI for small animals used for experiment etc. is mentioned as an apparatus using the magnetic resonance image contrast agent of this invention.

In addition, the magnetic resonance contrast agent of the present invention is capable of imaging various in vivo tissues such as lymphatic contrast, blood vessel contrast, nerve contrast, and the like.

<Kit>
The kit of the present invention is a kit used for magnetic resonance imaging including the magnetic resonance contrast agent described above.

The components of the kit include a magnetic resonance contrast agent containing the porphyrin iron (III) complex described above, a liquid such as a diluent, a dispersion, and a solution; a syringe (including a plunger, a barrel, a gasket, a top cap, and the like), Includes tubes, three-way stopcocks, winged needles, needles, and the like.

In these kits, for example, a magnetic resonance contrast agent containing a porphyrin iron (III) complex adjusted to various dosage forms may be in a prefilled form stored in a syringe, and the porphyrin iron (III) complex and / or Or the kit of the aspect in which the magnetic resonance contrast agent containing the compound modified by this porphyrin iron (III) complex and another component exist separately may be sufficient.

<Magnetic resonance imaging method>
The magnetic resonance imaging method of the present invention is a method including a step of acquiring a magnetic resonance signal by applying an excitation magnetic field pulse to a subject to which the above-described magnetic resonance contrast agent is administered.

The subject may be a human, another animal, or a cell. The administration method is not particularly limited, and may be the same as the administration method described above.

It should be noted that the imaging method using a magnetic resonance apparatus such as an MRI apparatus and various conditions such as a specific type of apparatus may be the same as those described in detail in <Magnetic Resonance Contrast Agent>.

Hereinafter, the present invention will be further described. However, it goes without saying that the present invention is not limited to the following examples.

In the following experimental examples, β-hematin crystals (hemozoin) were used as the porphyrin iron (III) complex contained in the magnetic resonance contrast agent of the present invention. Specifically, synthetic hemozoin was produced by adopting the method described in International Publication No. 2011/0747411. The obtained hemozoin was suspended in deionized distilled water with ultrasonic waves for 20 minutes so as not to aggregate, and the particle size distribution was measured by a dynamic light scattering method (manufactured by Shimadzu Corporation: SALD-2200). It was 1500 nm (FIG. 1).

<Experimental example 1> Imaging ability of liver 100 mg of synthetic hemozoin described above was administered. In the administered mouse, magnetic resonance imaging was performed with an MRI apparatus in the vicinity of the abdomen immediately before administration, 1 day after administration, and 4 weeks after administration. The MRI apparatus used was a Bruker AVANCE II 500 WB, and magnetic resonance imaging was performed under conditions of the T2 enhancement mode. In addition, as a control experiment, instead of the above-mentioned synthetic hemozoin, a conventionally used liver contrast agent, Rhizovist (Fuji Film RI Pharma Co., Ltd.) was administered in the same manner. These results are shown in FIG.

In the conventional liver contrast medium, the low signal remains even after 4 weeks from the administration as shown by the arrowed part in the figure (A), but as shown in the figure (B). In synthetic hemozoin, as shown by the arrows, it is clear that low signal imaging can be seen if it is about one day after administration, and the low signal disappears if it is 4 weeks after administration. Therefore, it is clear that even if synthetic hemozoin is administered, it does not stay easily. It is also clear that synthetic hemozoin exhibits sufficient imaging ability for magnetic resonance imaging.

<Experimental example 2> Subcutaneous administration experiment of mouse 100 mg of the synthetic hemozoin described above was subcutaneously administered to the back of the mouse. One day and four weeks after the administration, the administration site was incised and observed. The photographic image is shown in FIG.

As is apparent from the results shown in FIG. 3, the synthetic hemozoin administered subcutaneously on the first day after administration remained as shown in the black spots, but no black spots were seen four weeks after administration, and subcutaneous administration was performed. It was revealed that the synthesized hemozoin did not remain.

<Experimental example 3> MRI when used as a phantom solution
The above synthetic hemozoin was dispersed in PBS to prepare a phantom. For control experiments, Saline (saline) and PBS were prepared.

These were imaged using a 11.7 T MRI apparatus under conditions of T2 enhancement mode. The obtained image is shown in FIG.

As is clear from the results shown in FIG. 3, it was clear that PBS and Sakline used as control experiments gave high signals, whereas phantoms containing synthetic hemozoin gave extremely low signals. became. Therefore, it was revealed that synthetic hemozoin has a sufficient contrast effect.

<Experimental example 4> Contrast effect when administered subcutaneously to mouse Synthetic hemozoin was subcutaneously administered to the back of the mouse. The particle diameter distribution of the administered synthetic hemozoin was 500 to 1000 nm. Immediately after administration, 1 week after administration, and 4 weeks after administration, the mice were subjected to magnetic resonance imaging in the vicinity of the chest using the above-described MRI apparatus under the T2-weighted mode conditions. The results are shown in FIG.

As a control experiment, 10 mg of Bioclone Inc., which is a magnetic particle of 1 μm, is used instead of the above-mentioned synthetic hemozoin. The mice were subcutaneously administered to the back of FA-101 mice and magnetic resonance imaging was performed immediately after administration, 1 week after administration, 4 weeks after administration, and 5 weeks after administration. The result is shown in FIG.

7 is the site where the synthetic hemozoin was administered and shows a low signal immediately after the administration, so that it is clear that a sufficient contrast effect is exhibited. In addition, it was also clear that the site of low signal decreased after 1 week and 4 weeks after administration, and it was revealed that synthetic hemozoin hardly stayed, in other words, low retention.

On the other hand, from the results shown in FIG. 6, conventionally used magnetic particles remain in large quantities even after 5 weeks have elapsed since administration, as indicated by the arrows in the figure. Also, the distortion of the image remains severe.

<Experimental Example 5> Visualization of cell level 10 mg of the above-mentioned synthetic hemozoin was mixed with macrophages collected from C57BL mice, and incubated for 12 hours in an environment of 5% CO ₂ and 37 ° C. to phagocytose the synthetic hemozoin into macrophages. It was. The phagocytic macrophages were then dispersed in PBS at a concentration of 10 ⁶ cells / ml to produce phantoms. For control experiments, phantoms and Salines containing macrophages that were not phagocytosed by synthetic hemozoin were prepared.

All of these were imaged under the conditions of the T2 enhancement mode using the MRI apparatus described above. The obtained image is shown in FIG.

As is clear from the results shown in FIG. 7, phantoms and salines containing macrophages that did not phagocytose synthetic hemozoin used as a control experiment gave only high signals, whereas phagocytosed synthetic hemozoin. In the phantom containing macrophages, spots showing low signals were observed. These indicate that there is a synthetic hemozoin taken up by macrophages in macrophages. A large spot indicates a portion where macrophages are aggregated.

From this, it has been clarified that synthetic hemozoin exhibits a contrast ability with a high resolution and a high resolution that can be distinguished at a single cell level. Therefore, it was revealed that synthetic hemozoin has a sufficient contrast effect. Furthermore, it is suggested that the behavior of cells in a living body can be observed over time by using synthetic hemozoin.

From the above results, it has been clarified that synthetic hemozoin exhibits a low retention property superior to that of resovist while having the same imaging ability as conventional resovist.

The magnetic resonance contrast agent comprising the porphyrin iron (III) complex and / or the compound modified by the porphyrin iron (III) complex of the present invention is used for diagnosis of magnetic resonance images represented by MRI in a medical field for humans, experimental animals. It can be used effectively at research sites using the above.

Claims

A magnetic resonance contrast agent comprising a porphyrin iron (III) complex and / or a compound modified by the porphyrin iron (III) complex.
The magnetic resonance contrast agent according to claim 1, wherein the porphyrin iron (III) complex is β-hematin or a derivative thereof.
The magnetic resonance contrast agent according to claim 1 or 2, wherein the porphyrin iron (III) complex is a crystal.
The magnetic resonance contrast agent according to claim 3, wherein a particle size distribution of the crystal is 5 nm to 3 µm.
5. The magnetic resonance contrast agent according to claim 4, wherein the crystal particle size distribution is 50 nm to 1.5 μm.
A magnetic resonance imaging kit comprising the magnetic resonance imaging agent according to any one of claims 1 to 5.
A magnetic resonance imaging method including a step of acquiring a magnetic resonance signal by applying an excitation magnetic field pulse to a subject to which the magnetic resonance contrast agent according to any one of claims 1 to 5 is administered.