Application of IRMOF-8 or IRMOF-10 in ultrasensitive magnetic resonance imaging at room temperature

Abstract

The present invention discloses an application of IRMOF-8 or IRMOF-10 in ultrasensitive magnetic resonance imaging at room temperature, wherein a series of metal organic framework nanoparticles with different pore structures are obtained by regulating the structure of the organic framework, and the metal organic framework nanoparticles are used as super xenon-129 ( 129 Xe) carrier, a series of chemically shift-distinguishable super- 129 Xe spectroscopy and imaging signals provide a variety of contrast agents with simple synthesis and excellent properties for ultra-sensitive magnetic resonance imaging, which are expected to be applied in the biomedical field.

Description

Technical Field

[0001] This invention is a divisional application. The original Chinese patent application number is 202010331381.7. The application date is April 24, 2020. The patent name at the time of application is: Application of metal-organic framework nanoparticles in ultra-sensitive magnetic resonance imaging.

[0002] The invention belongs to the technical field of magnetic resonance imaging, and in particular relates to an application of metal organic framework nanoparticles in ultra-sensitive magnetic resonance imaging. Background Art

[0003] Magnetic resonance imaging (MRI) is an imaging technique based on the nuclear magnetic resonance phenomenon. It has no ionizing radiation, is non-invasive, has high tissue penetration and spatial resolution, and has been widely used in clinical practice as a routine detection technique. 1 The sensitivity of MRI for H nucleus detection is low because only one in 100,000 signal atoms can be directly detected at room temperature under thermal equilibrium. Usually, the concentration of the detected substance needs to reach the millimolar (mM) level before MRI can be performed, which greatly limits the development of MRI in emerging fields such as molecular imaging.

[0004] Super Xenon-129 Magnetic Resonance Imaging ( 129 Xe MRI provides a new technical means to solve the above problems. The super-magnification technology transfers the angular momentum of photons to 129 Xe atoms make 129 The spins of Xe atoms are in the same direction. Compared with the thermal equilibrium state, the super-magnetic resonance sensitivity is increased by more than 50,000 times. In other words, through the super-magnetic resonance technology, 1 / 2 of the super-magnetic resonance 129 Xe atoms can be directly detected by magnetic resonance technology. It is precisely because of the greatly improved sensitivity that the low proton density in the lung cavity cannot be imaged. 129 Xe MRI illuminates the blind spot of traditional magnetic resonance imaging - the lungs. 129 Xe has good lipid solubility and chemical shift sensitivity, and can be used to quantitatively visualize and evaluate changes in ventilation function, microstructure, and gas-blood exchange function in patients with lung diseases. 129 Xe is a chemically inert atom and is difficult to bind to specific small molecules, proteins, or RNA.

[0005] To give 129 Xe targeting, researchers developed a series of 129 Xe "cage" and achieved through the targeting group connected to the cage 129 Selective imaging with Xe MRI. 129After Xe enters the "cage", due to the change in the chemical environment, it will obtain a different chemical environment from the free Xe in the blood and tissues. 129 Different magnetic resonance signals of Xe atoms. Nanostructured particles such as microemulsions, proteins, and dendrimers can provide 129 Xe's space, but what it gets 129 Xe magnetic resonance signals are broad and difficult to distinguish. Axon is a supramolecule with an inner diameter of about 5 Å. Its inner hole is just enough for a Xe atom to enter, which can produce a strong magnetic resonance signal. However, axon is expensive, difficult to synthesize, insoluble in water, and has poor biocompatibility, making it difficult to apply in the field of molecular probes. So far, no suitable "cage" has been found for it. 129 Xe habitat, and there is no information yet 129 Xe molecular probes have been reported at the in vivo level in animals. Therefore, only by developing a suitable "cage" can 129 Xe magnetic resonance, a new ultra-sensitive imaging technology that is non-radioactive, non-invasive, and has no depth limit, can better serve biomedicine.

[0006] Metal organic frameworks (MOFs) are a type of crystalline porous material with a periodic network structure formed by the self-assembly of inorganic metal centers and bridging organic ligands. They have been widely studied in the fields of gas separation, energy storage, drug delivery, and bioimaging. Compared with other porous materials, the pore structure of MOF can be precisely controlled by designing the starting metal center and organic ligands. If a pore structure similar to that of "Xe" can be obtained through precise design and control, the problem of poor Xe cage signal and difficulty in obtaining can be solved. In addition, 129 Xe atoms are very sensitive to their surroundings: traditional 1 The chemical shift spectrum width of H NMR is about 20 ppm, while 129 The chemical shift spectrum width of Xe exceeds 5000 ppm. 129 Xe magnetic resonance signals will be easier to distinguish and the imaging signal-to-noise ratio will be better. Summary of the invention

[0007] Based on the above discussion, the present invention designs and obtains a series of MOFs by adjusting the organic ligand structure. 129 MOF nanoparticles for Xe MRI. They can not only act as cages to capture 129 Xe, thus obtaining a magnetic resonance signal that is completely separated from the free Xe signal, and each of the two MOF nanoparticles 129 The intervals between Xe magnetic resonance signals are all greater than 9 ppm. 129The Xe signal in each MOF nanoparticle can also be completely separated. Therefore, the present invention will provide a variety of different carrier cages for 129 Further applications of Xe MRI provide new tools.

[0008] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0009] Application of metal-organic framework nanoparticles in ultrasensitive magnetic resonance imaging.

[0010] Furthermore, hyperpolarized 129Xe is used as a signal source for magnetic resonance imaging, and metal organic framework nanoparticles are carriers of hyperpolarized 129Xe.

[0011] Furthermore, the metal organic framework nanoparticles are IRMOFs materials, which are a single microporous structure with a micropore inner diameter of 3.8-19.1 Å, and are composed of [Zn 4 O] 6+ The inorganic groups and aromatic carboxylic acid ligands are connected in an octahedral manner to form a three-dimensional cubic microporous framework. 4 O] 6+ The inorganic group is connected to 6 carboxylic acid ligands, each of which is connected to 2 [Zn 4 O] 6+ Inorganic group connection.

[0012] Furthermore, the metal organic framework nanoparticles are IRMOF-1, IRMOF-8, and IRMOF-10.

[0013] Furthermore, [Zn 4 O] 6+ Inorganic groups react with different aromatic carboxylic acid ligands to prepare a variety of IRMOF nanoparticles, at least two IRMOF nanoparticles are dispersed in a sample solution to obtain at least two sample solutions, 129Xe gas is passed through a polarization device and then directly introduced into the two sample solutions, and the gas is stopped and bubbles are removed to serve as a hyperpolarizer. 129 Xe carriers are injected into the object to be tested, and Hyper-CEST imaging is performed to obtain the different hyperpolarizations in the object to be tested. 129 Magnetic resonance imaging signal of Xe carriers.

[0014] Furthermore, the three nanoparticles IRMOF-1, IRMOF-8, and IRMOF-10 were dispersed in the same solution to obtain a mixed solution of the three nanoparticles. After 129Xe gas passed through a polarization device, it was directly introduced into the mixed solution. After the gas was stopped and the bubbles were removed, Hyper-CEST spectroscopy and imaging tests were performed. Three chemical shifts that could be distinguished were obtained in one magnetic resonance spectrum. 129Xe signal, and the corresponding magnetic resonance imaging signals can be obtained under three chemical shifts.

[0015] Compared with the prior art, the beneficial effects and advantages of the present invention are:

[0016] 1. Compared with the lower sensitivity (millimolar) of conventional MRI, the ultra-sensitive 129 Xe MRI has a sensitivity of nanomolar (nM), which is six orders of magnitude lower than conventional MRI. 129 Xe MRI is more suitable for molecular imaging research.

[0017] 2. Other reported Xe-carrying cages, such as caveflies, CB6, and microemulsions, can only produce one signal, or two signals that are very different and difficult to distinguish. However, through reasonable molecular design, MOFs with similar chemical structures but slight differences can be obtained. 129 The signal difference of Xe in various MOFs can be greater than 9 ppm, and the signals are easy to distinguish.

[0018] 3. Compared with the traditional "hole-shaped" cage, MOF has a simple synthesis process, high yield, good stability, and has the potential for large-scale application.

[0019] 4. Compared with other reported nanoscale cages, such as microemulsions, proteins, dendrimers, etc. 129 The signal peak of Xe in MOF is narrower and more stable.

[0020] 5. The most widely studied carrier "Xuanfan" can provide hydrophobic inner pores for 129Xe exchange, and its inner diameter is 5.5~5.6 Å. By adjusting the chain length of the aromatic carboxylic acid ligand, IRMOF nanoparticles with a micropore inner diameter of 3.8-19.1 Å can be obtained, and its micropores are also hydrophobic, so IRMOF can provide a microporous structure similar to "Xuanfan" for 129Xe exchange. In addition, compared with other mesoporous nanomaterials, IRMOF has a regular pore structure and can provide a single microenvironment, so the obtained 129Xe magnetic resonance signal is narrow and strong;

[0021] For example, IRMOF-1 has an inorganic group Zn 4 O(CO 2 ) 6 and carboxylic acid ligand terephthalic acid (H 2BDC), IRMOF-8 and IRMOF-10 have inorganic groups Zn4O(CO2)6 and dicarboxylic acid ligands: 2, 6-naphthalene dicarboxylic acid and 4, 4'-biphenyl dicarboxylic acid. The structural chain lengths of the carboxylic acid ligands are similar, so the inner diameters of the micropores of IRMOF-1, IRMOF-8 and IRMOF-10 are similar. ZIF-8 is a zeolite imidazole framework material, and ZIF-s is a ZnN formed by the metal Zn ion connected to the N atom in methyl imidazole ester. 4 Tetrahedral structural unit, the organic framework of ZIF-8 is 2-methylimidazole with five-membered aromatic heterocyclic ring, with multi-level micropores, mainly 2 types of micropores of 0.4~0.7nm and 0.75~1.0nm. The obtained nanomaterial micropore structure and chemical environment are relatively simple, and the pore structure, size and chemical environment of ZIF-s cannot be designed and adjusted. The organic skeleton of IRMOF is terephthalic acid and its extended structure, such as naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, etc. By controlling the chain length of the benzene ring structure, a series of organic metal skeleton nanoparticles with large differences in pore structure, size and chemical environment can be obtained, so a variety of 129Xe MRI contrast agents with large differences in chemical shift values ​​and easy-to-distinguish signals can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Hyper-CEST spectrum of metal organic framework nanoparticles IRMOF-1;

[0023] Figure 2 Hyper-CEST spectrum of metal organic framework nanoparticles IRMOF-8;

[0024] Figure 3 Hyper-CEST spectrum of metal organic framework nanoparticles IRMOF-10;

[0025] Figure 4 Control the skeleton structure of metal organic framework nanoparticles to obtain Hyper-CEST imaging signals with different ultra-sensitive magnetic resonance. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to specific embodiments.

[0027] The main reagents, instruments and physical quantities used in the following examples are as follows:

[0028] The preparation method of metal organic framework nanoparticles is based on the literature ( Angew. Chem. Int. Ed. 2014,53, 429–433).

[0029] Nuclear magnetic resonance instrument (400 MHz Bruker AV400 wide bore spectrometer).

[0030] ppm refers to the unit of chemical shift. The relative numerical representation method is now used, that is, a standard substance is selected, and the position of the resonance absorption peak of the standard substance is taken as the zero point. The chemical shift values ​​of other absorption peaks are determined based on the distance between the positions of these absorption peaks and the zero point.

[0031] Chemical shift values ​​are generally expressed as dimensionless δ values, which are defined as:

[0032] .

[0033] Polarization is defined as the difference between the two energy level configurations with opposite spin orientations, that is, P = (N 1 – N 2 ) / (N 1 + N 2 ) where N 1 and N 2 There are two spin energy levels M 1 =-1 / 2, M 2 =1 / 2 the number of layouts.

[0034] Example 1

[0035] Hyper-CEST spectroscopy test of metal-organic framework nanoparticles IRMOF-1.

[0036] Experimental methods:

[0037] The specific experimental steps are as follows:

[0038] 1.1 Weigh 5 mg terephthalic acid, 24 mg Zn(NO 3 ) 2 6H 2 O and 312 mg polyvinyl pyrrolidone were dissolved in a mixture of 13.5 mL N, N-dimethylformamide (DMF) and ethanol and ultrasonicated for 10 minutes. The resulting mixture was reacted at 150°C for 12 hours in a 25 mL autoclave. After the reaction, the temperature was gradually lowered to room temperature, and then the reaction solution was centrifuged at 10,000 rmp for 15 minutes, the supernatant was discarded, and the white solid obtained by centrifugation was washed with DMF and ethanol three times each. The obtained nanoparticles were named IRMOF-1.

[0039] 1.2 Add the IRMOF-1 nanoparticles obtained in 1.1 to 2 mL of ethanol and sonicate at room temperature (25°C) for 20 min to fully disperse the IRMOF-1 nanoparticles. Then transfer the mixed sample to a 10 mm NMR sample tube and place the NMR sample tube in a magnetic resonance spectrometer for testing.

[0040] 1.3 Xe gas is hyperpolarized by the permanent magnet polarizer described in CN102364333B to obtain a hyperpolarized gas with a polarization degree of 10%. 129 Xe gas. During the test, the volume percentage is 10% N 2 , 88% He, 2% Xe (natural abundance) mixed gas components after flowing through the permanent magnetic polarizer, into the nuclear magnetic resonance sample tube containing IRMOF-1 dispersed solution placed in the nuclear magnetic resonance spectrometer, set the flow rate to 100 mL / min, and continue ventilation for 20s. After the ventilation is completed, wait for 3s to remove the bubbles. Then, a continuous wave pulse with an intensity of 6.0 μT and a duration of 5s is used to selectively saturate the signal of Xe in the IRMOF-1 nanoparticles, and then the spectrum is collected. The test temperature is controlled at 298 K using the temperature control unit of the nuclear magnetic resonance instrument. The spectrum width selected in the experiment is 80 pm, the saturation irradiation range is -20 ppm -60 ppm, and the saturation irradiation pulse intensity is 6.5μT. A point is taken every 1 ppm or 2 ppm, and each point is saturated for 10 s.

[0041] Each Xe spectrum is obtained by single sampling and processed using a 6Hz LB window function. 129 The Xe signal was calibrated to 0 ppm. 129 Integrate the Xe signal and record its integral value M z , after turning off the saturation irradiation pulse, collect 129 Xe spectrum, for dissolved 129 Integrate the Xe signal and record its integral value M 0 , then M z / M 0 The Hyper-CEST spectrum can be obtained by plotting the saturated irradiation site as the vertical axis and the saturated irradiation site as the horizontal axis.

[0042] Experimental results: Figure 1 As shown in Figure 2, IRMOF-1 nanoparticles have a better Hyper-CEST effect. 129 Compared with Xe, IRMOF-1 nanoparticles 129 The Hyper-CEST signal of Xe is located at 48 ppm.

[0043] Example 2

[0044] Regulating the skeleton structure of metal-organic framework nanoparticles to obtain multiple ultrasensitive magnetic resonance spectroscopy signals

[0045] Experimental methods:

[0046] The specific experimental steps are as follows:

[0047] 2.1 Weigh 6.5 mg 2, 6-naphthalenedicarboxylic acid, 24 mg Zn(NO 3 ) 2 6H 2 O and 312 mg polyvinyl pyrrolidone were dissolved in a mixture of 13.3 mL N, N-dimethylformamide (DMF) and ethanol and ultrasonicated for 10 minutes. The resulting mixture was reacted at 150°C for 12 hours in a 25 mL autoclave. After the reaction, the temperature was gradually cooled to room temperature, and then the reaction solution was centrifuged at 10,000 rpm for 15 minutes, the supernatant was discarded, and the white solid obtained by centrifugation was washed with DMF and ethanol three times each. The obtained nanoparticles were named IRMOF-8.

[0048] 2.2 Weigh 7.3 mg 4, 4'-biphenyl dicarboxylic acid, 24 mg Zn(NO 3 ) 2 6H 2 O and 312 mg polyvinyl pyrrolidone were dissolved in a mixture of 13.3 mL N, N-dimethylformamide (DMF) and ethanol and ultrasonicated for 10 minutes. The resulting mixture was reacted at 150°C for 12 hours in a 25 mL autoclave. After the reaction, the temperature was gradually cooled to room temperature, and then the reaction solution was centrifuged at 10,000 rmp for 15 minutes, the supernatant was discarded, and the white solid obtained by centrifugation was washed with DMF and ethanol three times each. The obtained nanoparticles were named IRMOF-10.

[0049] 2.3 The IRMOF-8 and IRMOF-10 nanoparticles obtained in 2.1 and 2.2 were added to 2 mL of ethanol, and ultrasonicated for 20 min at room temperature (25 °C) to fully disperse the IRMOF-8 and IRMOF-10 nanoparticles, respectively. The mixed samples were then transferred to a 10 mm NMR sample tube, and the NMR sample tube was placed in a magnetic resonance spectrometer for testing.

[0050] 2.4 According to the description in step 1.3 of Example 1, IRMOF-8 and IRMOF-10 were super-treated. 129 XeHyper-CEST spectroscopy test.

[0051] Experimental results: Figure 2 and Figure 3 As shown in Figure 2, both IRMOF-8 and IRMOF-10 nanoparticles have good Hyper-CEST effects. 129 Compared with Xe, IRMOF-8 nanoparticles 129 The Xe Hyper-CEST signal is located at 17 ppm in IRMOF-10 nanoparticles. 129The Hyper-CEST signal of Xe is located at 26 ppm. IRMOF-1 ( Figure 1 ) Nanoparticles 129 The Xe signal is located at 48 ppm, and three different 129 Xe superposition in metal-organic framework nanoparticles 129 Xe Hyper-CEST. Therefore, using metal organic framework nanoparticles as carriers can not only obtain 129 Xe's new Hyper-CEST signal can also obtain a variety of Hyper-CEST signals with large differences and easy to distinguish by designing and controlling the skeleton structure.

[0052] Example 3

[0053] Regulating the skeleton structure of metal-organic framework nanoparticles to obtain multiple ultrasensitive magnetic resonance imaging signals

[0054] Experimental methods:

[0055] The specific experimental steps are as follows:

[0056] 3.1 The IRMOF-1, IRMOF-8 and IRMOF-10 obtained in step 1.1 of Example 1, step 2.1 and step 2.2 of Example 2 were dispersed in 2 mL of ethanol, ultrasonicated for 20 minutes, and then transferred to a 10 mm NMR sample tube.

[0057] 3.2 Tune, homogenize, collect positioning images, and select appropriate layers and layer thicknesses in the imaging spectrometer.

[0058] 3.3 As described in step 1.1 of Example 1, 129 After the Xe gas flows through the polarization device, it is directly introduced into the NMR sample tube containing the dispersed solution of IRMOF-1, IRMOF-8, and IRMOF-10 at a flow rate of 100 mL / min and aerated for 20 seconds. After the aeration is completed, wait for 3 seconds to remove the bubbles. 129 Xe MRI uses the RARE sequence for sampling, with 4 repetitions, a slice thickness of 30 mm, a sampling matrix of 30 × 32, and a FOV of 20 × 20 mm. 2 , echo time 4.6 ms, repetition time 28 ms, acceleration factor 8, K space encoding using center encoding; when sampling, first use a 6.5μT saturation pulse to saturate the cage 129 Xe signal for 5s to obtain a saturated image; then the same pulse is used to saturate the cage 129 The symmetric position of Xe signal (in dissolved state 129 Xe is the symmetry center) to obtain an unsaturated image.

[0059] 3.4 During data processing, the 32×32 sampling matrix was interpolated to 64×64, and the average CEST effect was calculated using the formula (Soff-Son) / Soff, where Soff represents the average signal intensity of the off-resonance image and Son represents the average signal intensity of the on-resonance image. Matlab program was used for data processing and image reconstruction. The difference between the unsaturated image and the saturated image was divided by the unsaturated image to reconstruct the Hyper-CEST image. The CEST effect image was then filtered using a 3*3 median filter and segmented using a threshold.

[0060] Experimental results: Figure 4 As shown, IRMOF-1, IRMOF-8 and IRMOF-10 solutions were saturated irradiated at 48 ppm, 26 ppm and 17 ppm, respectively: IRMOF-1 only has an obvious signal at its characteristic value of 48 ppm, the signal at 26 ppm is very weak, and there is no signal at 17 ppm which is far away from its characteristic value; IRMOF-8 only has an obvious signal at its characteristic value of 17 ppm, the signal at 26 ppm is very weak, and there is no signal at 48 ppm which is far away from its characteristic value; IRMOF-10 only has an obvious signal at its characteristic value of 26 ppm, and the signals at 17 ppm and 48 ppm are both very weak.

Claims

1. Use of metal organic framework nanoparticles in the preparation of ultrasensitive magnetic resonance imaging agents, characterized in that: Hyperpolarization 129 Xe as a signal source for magnetic resonance imaging, metal organic framework nanoparticles as hyperpolarized 129 The carrier of Xe, the metal organic framework nanoparticles are IRMOF-8 or IRMOF-10, IRMOF-8 or IRMOF-10 is dispersed in the sample solution, 129 After the Xe gas flows through the polarization device, it is directly introduced into the sample solution. After the ventilation is stopped and the bubbles are removed, Hyper-CEST imaging is performed to obtain different hyperpolarizations in the object to be tested. 129 Magnetic resonance imaging signal of Xe carriers; The IRMOF-8 is prepared by dissolving 6.5 mg 2, 6-naphthalene dicarboxylic acid, 24 mg Zn(NO3)2·6H2O and 312 mg polyvinyl pyrrolidone in a mixture of 13.3 mL N, N-dimethylformamide (DMF) and ethanol, ultrasonicating for 10 minutes, reacting the mixture at 150° C. for 12 hours in a 25 mL autoclave, cooling to room temperature at a gradient after the reaction, and then centrifuging the reaction solution at 10,000 rpm for 15 minutes, discarding the supernatant, and washing the centrifuged white solid with DMF and ethanol for 3 times each; The IRMOF-10 is prepared by dissolving 47.3 mg of 4, 4'-biphenyldicarboxylic acid, 24 mg of Zn(NO3)2·6H2O and 312 mg of polyvinylpyrrolidone in a mixture of 13.3 mL of N, N-dimethylformamide (DMF) and ethanol, ultrasonicating for 10 minutes, reacting the mixture at 150°C for 12 hours in a 25 mL high-pressure reactor, cooling to room temperature gradually after the reaction, and then centrifuging the reaction solution at 10,000 rmp for 15 minutes, discarding the supernatant, and washing the white solid obtained by centrifugation with DMF and ethanol three times each.

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