Nano-enzyme with MRI (Magnetic Resonance Imaging) radiography function based on Gd monatomic and preparation method and application of nano-enzyme

Abstract

The invention discloses a Gd single atom-based nano enzyme with an MRI (Magnetic Resonance Imaging) radiography function as well as a preparation method and application of the Gd single atom-based nano enzyme. The nano enzyme comprises porphyrin and a Gd single atom located at the center of the porphyrin, and the Gd single atom is covalently connected with the porphyrin through a Gd-N bond; the preparation method comprises the following steps: carrying out reduction reaction on a mixed solution A to prepare nano-enzyme; wherein the solution A comprises a Gd ion-porphyrin complex, copper salt, fluorine-containing organic acid, a dispersing agent and a solvent. The nano enzyme has relatively high stability, relaxation rate and biological safety when being used for MRI (Magnetic Resonance Imaging) radiography, and excellent T1WI imaging performance, and also has excellent SOD (Superoxide Dismutase) enzyme activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of pharmaceutical preparation, and specifically relates to a nanozyme with MRI contrast function based on a single Gd atom, and a preparation method and application thereof. Background Art

[0002] Since Lauterbur first realized magnetic resonance imaging (MRI) in 1973, MRI technology has been highly valued by the scientific community for its non-invasive, painless, high soft tissue contrast and spatial resolution, and has continued to develop in clinical applications. MRI has unique advantages over other medical imaging devices (DR, CT, ultrasound, PET), and has now become one of the most important medical imaging devices in imaging examinations. However, the resolution of plain scan MRI does not meet clinical requirements in some cases (such as early diagnosis of tumors, evaluation of vascular lesions, etc.). In order to enhance the imaging effect, MRI contrast agents need to be given before MRI examinations. According to literature reports, more than 45% of MRI examinations in clinical MRI currently require the use of contrast agents. Among them, gadolinium-based MRI contrast agents are the most commonly used in clinical applications. So far, there are nine gadolinium-based MRI contrast agents approved by the US FDA, which can be roughly divided into two categories: one is a chain molecule with DTPA as the gadolinium ion chelating group, and the other is a cyclic molecule with DOTA as the gadolinium ion chelating group.

[0003] The contrast agent currently used in clinical practice is Gd-DOTA, which has a cyclic porphyrin structure and therefore has high kinetic and thermodynamic stability, and is the rare earth complex with the highest stability to date. However, there are also reports that this contrast agent causes nephrogenic systemic fibrosis in some patients and is more likely to cause gadolinium ion deposition in the patient's brain. When used in excessive doses, it will be detrimental to human health.

[0004] Superoxide dismutase (SOD) has an antioxidant effect and has great application potential in the pharmaceutical, cosmetic, food, agricultural and chemical industries. For example, a large number of clinical trials have shown that SOD can prevent tumorigenesis and reduce cytotoxicity. In cosmetics, SOD is used for skin protection and as an important antioxidant enzyme. They are also used in animal husbandry to reduce oxidative stress and improve the quality of animal products such as meat, eggs, milk and wheat.

[0005] In conjunction with the medical field involved in the invention, SOD enzyme has been identified for the prevention of many different diseases, such as cancer, cardiovascular disease, diabetes, asthma, infertility, nervous system diseases and transplant rejection. In addition to preventing diseases, SOD enzyme can prevent the formation of wrinkles. It can also promote wound healing, reduce scars, and reduce skin pigmentation caused by ultraviolet radiation, and help reduce cognitive impairment and other physiological decline caused by aging.

[0006] However, the practical application of SOD enzyme is often limited due to many problems such as unstable activity, high temperature resistance, acid and alkali resistance, enzymatic resistance, easy inactivation, and difficult preservation. Even though there are related studies on SOD enzyme mimics in the prior art, there is still a lack of reports on contrast agents with SOD enzyme activity and stable existence. Summary of the invention

[0007] In view of the shortcomings of the above-mentioned technologies, the present invention provides a nanozyme with MRI angiography function based on a single Gd atom, and a preparation method and application thereof. The nanozyme has high stability, relaxation rate, and biosafety when used for MRI angiography, has excellent T1WI imaging performance, and also has excellent SOD enzyme activity.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a nanozyme with MRI angiography function based on a Gd single atom, wherein the nanozyme comprises a porphyrin and a Gd single atom located at the center of the porphyrin; wherein the Gd single atom is covalently connected to the porphyrin via a Gd-N bond.

[0010] In the present invention, the porphyrin center refers to the center of a single porphyrin, rather than a hollow or hollow-like structure formed by multiple porphyrins.

[0011] In some embodiments, the content of the Gd single atom in the nanozyme is 3 wt%-10 wt%, for example 4.9 wt%.

[0012] In some embodiments, the nanozyme has superoxide dismutase activity.

[0013] In some embodiments, the nanozyme exists in a single-layer two-dimensional sheet structure. The sheet structure can maximize the exposure of the metal sites loaded on the inner side on nitrogen, allowing the single-atom metal to fully contact with water molecules, thereby further improving its relaxation performance.

[0014] In some embodiments, the nanozyme has a particle size of 100-200 nm. Within the particle size range of 100-200 nm, the nanozyme has a strong permeability and retention effect on tumor tissue and can also increase its aggregation at the tumor site.

[0015] In some embodiments, the porphyrin is selected from one of DTPA, DOTA and TCPP, preferably TCPP.

[0016] The present invention also provides a method for preparing the nanozyme as described above, the preparation method comprising the following steps:

[0017] The nanozyme is prepared by a reduction reaction of a mixed solution A; wherein the solution A comprises a Gd ion-porphyrin complex, a copper salt, a fluorine-containing organic acid, a dispersant and a solvent.

[0018] In some embodiments, the copper salt is copper nitrate and / or copper nitrate trihydrate.

[0019] In some embodiments, the fluorine-containing organic acid is trifluoroacetic acid.

[0020] In some embodiments, the dispersant is PVP, preferably PVP K30. The dispersant can improve the dispersibility between nanozyme particles, prevent agglomeration from affecting the relaxation performance, and improve the water solubility and biocompatibility of nanozyme particles, thereby reducing chemical toxicity.

[0021] In some embodiments, the content of the Gd ion-porphyrin complex in the mixed solution A is 0.1-0.5 mg / mL, for example 0.29 mg / mL.

[0022] In some embodiments, the content of the copper salt in the mixed solution A is 0.1-0.5 mg / mL, for example 0.12 mg / mL.

[0023] In some embodiments, the content of the fluorine-containing organic acid in the mixed solution A is 1-10 mmol / L, for example, 2.5 mmol / L.

[0024] In some embodiments, the content of the dispersant in the mixed solution A is 0.1-1 mg / mL, for example 0.625 mg / mL.

[0025] In some embodiments, the solvent is a mixed solution of DMF and anhydrous ethanol; preferably, the volume ratio of DMF to anhydrous ethanol is 3:1.

[0026] In some embodiments, the temperature of the reaction is 76°C-84°C.

[0027] In some embodiments, the reaction temperature is 3-5h, such as 4h.

[0028] In some embodiments, the preparation step of the mixed solution A comprises the following steps: the Gd ion-porphyrin complex is dissolved in the solvent to obtain solution 1, the copper salt, fluorine-containing organic acid and dispersant are dissolved in the solvent to obtain solution 2, and the solution 1 and solution 2 are then mixed; preferably, the mixing is performed by adding the solution 1 to the solution 2.

[0029] In some embodiments, before the reacting step, a step of ultrasonicating the mixed solution A is also included.

[0030] In some embodiments, the reacting step further includes cooling and washing steps.

[0031] In some embodiments, the preparation of the Gd ion-porphyrin complex comprises the following steps:

[0032] The mixed solution B is reacted to obtain the Gd ion-porphyrin complex; the mixed solution B includes a Gd precursor, porphyrin and a solvent.

[0033] The Gd precursor is preferably selected from one or more of gadolinium chloride, gadolinium acetate, gadolinium nitrate and hydrates thereof, such as gadolinium acetate trihydrate.

[0034] Wherein, the porphyrin is preferably selected from one of DTPA, DOTA and TCPP, more preferably TCPP.

[0035] The molar ratio of the Gd precursor to the porphyrin is preferably (4-6):1, more preferably 5:1.

[0036] Wherein, the solvent is preferably DMF.

[0037] Wherein, the reaction is preferably carried out under a protective gas, such as nitrogen.

[0038] Wherein, the reaction temperature is preferably 95°C-105°C.

[0039] The reaction time is preferably 1-5 h, such as 2 h.

[0040] Wherein, the reaction step preferably further includes cooling and drying steps, and the drying is, for example, vacuum drying.

[0041] The present invention also provides a use of the nanozyme as described above in a magnetic resonance contrast agent.

[0042] The present invention also provides a use of the nanozyme as described above in removing active oxygen.

[0043] In some embodiments, the use comprises mimicking the action of superoxide dismutase.

[0044] In some embodiments, the use includes use in the preparation of an anti-inflammatory drug.

[0045] In some embodiments, the application includes using the nanozyme to simulate superoxide dismutase to perform a catalytic reaction of reactive oxygen to generate hydrogen peroxide. Specifically, the nanozyme is dissolved in deionized water to obtain an aqueous solution of the nanozyme and then the catalytic reaction is performed; preferably, after being dissolved in deionized water, ultrasonication is performed for 10 minutes to allow the nanozyme to be better dispersed in the solution and to fully exert the catalytic effect.

[0046] In some embodiments, the temperature of the catalytic reaction can be conventional in the art, such as 37°C.

[0047] In some embodiments, the catalytic reaction time is 10-50 min, preferably 20-40 min, more preferably 30-40 min, for example 40 min.

[0048] In some embodiments, in the aqueous solution of the nanozyme, the concentration of the nanozyme is 0.5-3 mg / mL, specifically, the concentration of the nanozyme includes but is not limited to 0.5-2 mg / mL, 0.5-1 mg / mL, 1-3 mg / mL or 1-2 mg / mL. At this time, the nanozyme has the best effect in catalyzing the removal of reactive oxygen.

[0049] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0050] The reagents and raw materials used in the present invention are commercially available.

[0051] The positive and progressive effects of the present invention are:

[0052] The nanozyme of the present invention comprises a specific structure in which a single-atom metal Gd is anchored to the porphyrin center by a Gd-N bond, and has excellent MRI imaging function and excellent SOD enzyme activity. Specifically, the single-atom metal Gd in the nanozyme is not easy to fall off, has high stability, and has excellent biological safety; the single-atom metal Gd is evenly and isolatedly dispersed in the porphyrin center to form a single-atom metal site, which ensures that the single-atom metal Gd and water are fully in contact, thereby enhancing the relaxation performance of water protons; and compared with ionic metals, the SOD enzyme activity of the single-atom metal loaded in the porphyrin center is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1This is a schematic diagram of the process for preparing a nanozyme with MRI angiography function based on a single Gd atom according to Example 1.

[0054] Figure 2 This is the TEM detection result in Effect Example 1 (scale is 0.5 μm).

[0055] Figure 3 The spherical aberration electron microscope detection result in effect embodiment 1 (scale is 10.0nm).

[0056] Figure 4 This is the N1s XPS spectrum in Effect Example 1.

[0057] Figure 5 This is the Gd 4d XPS spectrum in Effect Example 1.

[0058] Figure 6 This is the synchrotron radiation spectrum in effect embodiment 1.

[0059] Figure 7 This is the synchrotron radiation wavelet transform result of SA-Gd-TCPP in effect embodiment 1.

[0060] Figure 8 This is the synchrotron radiation wavelet transform result of Gd2O3 in effect example 1.

[0061] Fig. 9 This is a comparison chart of the relaxation rate r1 of SA-Gd-TCPP in Effect Example 1 and the commercial contrast agent.

[0062] Fig.10 This is a diagram showing the 7T magnetic resonance T1WI imaging results of SA-Gd-TCPP and commercial contrast agents in Effect Example 1.

[0063] Fig.11 Graph showing the relationship between cell viability of the lung cancer cell line LLC in Effect Example 1 at different SA-Gd-TCPP concentrations.

[0064] Fig.12 The results of SOD enzyme activity detection of SA-Gd-TCPP, Gd-TCPP-1 and Gd-TCPP-2 in Example 1 are shown. DETAILED DESCRIPTION

[0065] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0066] Example 1

[0067] like Figure 1As shown, it is a schematic diagram of the process of preparing the nanozyme (SA-Gd-TCPP) with MRI imaging function based on Gd single atom in this embodiment. The specific steps are as follows:

[0068] (1) Preparation of Gd ion-porphyrin complex (Gd-TCPP):

[0069] First, 33.16 mg of solid gadolinium acetate trihydrate and 15.97 mg of TCPP (molar ratio of 5:1) were dissolved and mixed in 25 mL of solvent (DMF) and then transferred into a reaction container. Under gas protection (such as nitrogen), the mixture was reacted at 100°C±5°C for 2 hours, cooled to room temperature, and the product was collected and vacuum dried overnight to obtain the product.

[0070] (2) Preparation of SA-Gd-TCPP:

[0071] Take 4.7 mg of Gd-TCPP powder and dissolve it in 12 mL of solvent (a mixed solution of DMF and anhydrous ethanol with a volume ratio of 3:1), which is recorded as liquid A. In addition, 2.4 mg of copper nitrate trihydrate, 40 μL of trifluoroacetic acid (1.0 M), and 10 mg of PVP (PVP K30) were dissolved in 4 mL of solvent (a mixed solution of DMF and anhydrous ethanol with a volume ratio of 3:1) and transferred into the reaction container, which is recorded as liquid B. Subsequently, the liquid B was stirred to mix well, and at the same time, the liquid A was added to the liquid B. After the mixed solution was ultrasonically treated for 15 minutes, it was reacted at 80°C ± 4°C for 4 hours, cooled at room temperature, and washed to obtain the product.

[0072] According to ICP measurement, the content of Gd single atoms in the SA-Gd-TCPP obtained in this example is 4.9 wt %.

[0073] Comparative Example 1

[0074] According to step (1) in Example 1, the Gd ion-porphyrin complex of this comparative example (denoted as Gd-TCPP-1) was prepared.

[0075] Comparative Example 2

[0076] The Gd ion-porphyrin complex (denoted as Gd-TCPP-2) of this comparative example was prepared according to the following steps.

[0077] Take 8.37mg of gadolinium chloride hexahydrate and 4.7mg of TCPP powder and dissolve them in 12mL of solvent (a mixed solution of DMF and anhydrous ethanol, with a volume ratio of 3:1), which is recorded as liquid A. In addition, 2.4mg of copper nitrate trihydrate, 40uL of trifluoroacetic acid (1.0M), and 10mg of PVP (PVP K30) are dissolved in 4mL of solvent (a mixed solution of DMF and anhydrous ethanol, with a volume ratio of 3:1) and transferred into the reaction container, which is recorded as liquid B. Subsequently, stir liquid B to mix well, and at the same time, add liquid A to liquid B. After ultrasonic treatment of the mixed solution for 15min, react at 80℃±4℃ for 4 hours, cool at room temperature, and wash to obtain the product.

[0078] Effect Example 1, morphology and structure related characterization

[0079] The SA-Gd-TCPP obtained in Example 1 was characterized as follows:

[0080] The SA-Gd-TCPP was tested by TEM, spherical aberration electron microscopy, XPS and synchrotron radiation, and the results were Figure 2-8 shown.

[0081] Depend on Figure 2 The TEM test results and Figure 3 The results of spherical aberration electron microscopy showed that the SA-Gd-TCPP had a flaky structure and a high load of Gd atoms. The particle size was 100-200 nm.

[0082] Depend on Figure 4 and Figure 5 The XPS spectrum of Gd 4d ( Figure 5 ) shows two characteristic peaks with binding energies of 147.6 eV and 142.8 eV, which are attributed to Gd 4d 3 / 2 and Gd 4d5 / 2. The high-resolution N1s XPS spectrum ( Figure 4 ) can be decomposed into four peaks, namely oxidized nitrogen (404.1 eV), graphitized nitrogen (400.8 eV), pyrrolic nitrogen (399.5 eV) and pyridinic nitrogen (398.1 eV).

[0083] Depend on Figure 6 From the synchrotron radiation spectrum, it can be seen that from the near-edge structure analysis of the L3 edge data of the element, in the near-edge structure: the Gd element in SA-Gd-TCPP is located between Gd foil and Gd2O3, indicating that the valence state of Gd is higher than 3. The above conclusions were also obtained for the position of the white line peak of SA-Gd-TCPP, and SA-Gd-TCPP has the highest white line peak intensity, indicating that its valence state is the highest, followed by Gd2O3 and Gd foil.

[0084] Furthermore, the synchrotron radiation spectrum was processed by wavelet transform, and the results are as follows: Figure 7 and Figure 8 As shown. Different colors represent the height of the peak, which can distinguish the distance of the coordinated atoms (i.e., bond length). Wavelet data combined with R space fitting information can well distinguish the coordination of the sample. The larger the atomic number, the higher the intensity of the horizontal axis. Figure 7 and Figure 8 The results show that the main path in SA-Gd-TCPP is Gd-N, and its wave center position is shifted to the left compared with Gd-O, so it is more likely to be Gd-N.

[0085] Based on the above characterization results, it is proved that the SA-Gd-TCPP of the present invention has single atoms coordinated by Gd—N.

[0086] On this basis, the present invention further tests and finds that the Gd-TCPP-1 obtained in Comparative Example 1 has a block structure as a whole, and the metal Gd exists in the form of Gd ions, and is not connected to the center of the porphyrin. Comparative Example 2 does not undergo a step of reacting under N2 (i.e., the Gd ion-porphyrin complex is not generated in advance), and although the obtained Gd-TCPP-2 has a sheet structure as a whole, the metal Gd still exists in the form of Gd ions and is not connected to the center of the porphyrin.

[0087] Effect Example 2, Magnetic Resonance Related Characterization

[0088] SA-Gd-TCPP obtained in Example 1 and clinically used Gd-DTPA (metallic Gd exists in the form of Gd ions) (Hengrui Medicine) were used for 7T magnetic resonance T1WI imaging, and the specific conditions were as follows:

[0089] T1-RARE sequence: TR = 300 ms, TE = 4.85 ms, slice thickness of acquired images was 1.0 mm, number of layers was 15, FOV = 30 × 30, MTX = 200 × 200;

[0090] T1-map sequence: TR=5500ms, TE=8.5ms, slice thickness of acquired images was 1.0mm, number of layers was 15, FOV=30×30, MTX=256×192.

[0091] The results are as follows Fig. 9 and 10 shown.

[0092] Depend on Fig. 9 The imaging results and Fig.10 The r1 value results show that, compared with the clinically used Gd-DTPA, the SA-Gd-TCPP of the present invention has a higher relaxation rate and better imaging effect.

[0093] Effect Example 3, Biosafety Related Characterization

[0094] The biosafety test was performed on the SA-Gd-TCPP obtained in Example 1, and the specific conditions were as follows:

[0095] 100 μL of cells (lung cancer cell line LLC, about 2000 cells) were added to each well of a 96-well plate. The cells were placed in a 5% CO2 cell culture incubator at 37°C for 24 hours. Then, 10 μL of different concentrations of SA-Gd-TCPP (final concentrations of 0, 20, 40, 60, 80, 100, 150, 200, 300 ppm) were added to each well for stimulation for 12 hours. Then, the cells were washed twice with PBS, and 100 μL of serum-free culture medium (containing 10 μL of CCK-8 solution) was added to each well. Subsequently, the cells were incubated in a 5% CO2 incubator at 37°C for 1 hour. The absorbance at 450 nm was measured by an enzyme-labeled instrument.

[0096] Cell viability: The OD value of each test well was subtracted from the background OD value (blank group), and the OD value of each replicate well was taken as the average ± SD.

[0097] That is: cell survival rate (%) = (OD of drug-treated cells / OD of control cells) × 100%.

[0098] The results are as follows Fig.11 As shown, it is indicated that the SA-Gd-TCPP of the present invention has good biosafety.

[0099] Effect Example 4, SOD enzyme activity related characterization

[0100] The SOD enzyme activity was determined using the SA-Gd-TCPP obtained in Example 1, the Gd-TCPP-1 obtained in Comparative Example 1, and the Gd-TCPP-2 obtained in Comparative Example 2. The specific conditions are as follows:

[0101] Dissolve it in deionized water, ultrasonicate for 10 minutes, shake well, and obtain an aqueous solution of the nanozyme; use a commercial kit, Bio-Tech Total SOD Activity Detection Kit (WST-8 method) (Cat. No.: S0101S) for detection.

[0102] The principle of the kit is: WST-8 can react with the superoxide anion (O2 - ) reaction produces a water-soluble formazan dye; since SOD can catalyze the dismutation of superoxide anions, this reaction step can be inhibited by SOD, that is, the enzyme activity of SOD is negatively correlated with the amount of formazan dye generated. The enzyme activity of SOD can be calculated by colorimetric analysis of the WST-8 product.

[0103] Compared with the control group in the kit, the inhibition rates of SA-Gd-TCPP, Gd-TCPP-1 and Gd-TCPP-2 (where the Gd concentration was 300 μM) after incubation for 30 min were as follows: Fig.12 shown.

[0104] The results showed that the SOD enzyme activities of the three were SA-Gd-TCPP, Gd-TCPP-2 and Gd-TCPP-1 from high to low. Among them, the metal utilization rate of single-atom Gd in SA-Gd-TCPP reached the maximum, the metal-carrier interface was maximized, the active site composition structure was uniform, and the morphology of the nanosheets provided more single-atom Gd binding sites.

Claims

1. A nanozyme with MRI imaging function based on a single Gd atom, characterized in that: The nanozyme includes porphyrin and a Gd single atom located at the center of the porphyrin; wherein the Gd single atom is covalently connected to the porphyrin via a Gd-N bond.

2. The nanozyme according to claim 1, characterized in that The content of the Gd single atom in the nanozyme is 3wt%-10wt%, for example 4.9wt%; And / or, the nanozyme has superoxide dismutase activity.

3. The nanozyme according to claim 1, characterized in that The nanozyme exists in a single-layer two-dimensional sheet structure; Preferably, the particle size of the nanozyme is 100-200 nm.

4. The nanozyme according to claim 1, characterized in that The porphyrin is selected from one of DTPA, DOTA and TCPP, preferably TCPP.

5. A method for preparing the nanozyme according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: The nanozyme is prepared by a reduction reaction of a mixed solution A; wherein the solution A comprises a Gd ion-porphyrin complex, a copper salt, a fluorine-containing organic acid, a dispersant and a solvent.

6. The method for preparing the nanozyme according to claim 5, characterized in that: The copper salt is copper nitrate and / or copper nitrate trihydrate; And / or, the fluorine-containing organic acid is trifluoroacetic acid; And / or, the dispersant is PVP, preferably PVP K30; And / or, the solvent is a mixed solution of DMF and anhydrous ethanol; preferably, the volume ratio of DMF to anhydrous ethanol is 3:1; and / or, the content of the Gd ion-porphyrin complex in the mixed solution A is 0.1-0.5 mg / mL, for example 0.29 mg / mL; And / or, the content of the copper salt in the mixed solution A is 0.1-0.5 mg / mL, for example 0.15 mg / mL; And / or, the content of the fluorine-containing organic acid in the mixed solution A is 1-10 mmol / L, for example, 2.5 mmol / L; and / or, the content of the dispersant in the mixed solution A is 0.1-1 mg / mL, for example 0.625 mg / mL; And / or, the reaction temperature is 76°C-84°C; And / or, the reaction temperature is 3-5h, such as 4h; And / or, the preparation step of the mixed solution A comprises the following steps: the Gd ion-porphyrin complex is dissolved in the solvent to obtain solution 1, the copper salt, fluorine-containing organic acid and dispersant are dissolved in the solvent to obtain solution 2, and the solution 1 and solution 2 are then mixed; preferably, the mixing is performed in a manner of adding the solution 1 to the solution 2; And / or, before the step of reacting, the step of ultrasonicating the mixed solution A is also included; And / or, the reaction step further includes cooling and washing steps.

7. The method for preparing the nanozyme according to claim 5, characterized in that: The preparation of the Gd ion-porphyrin complex comprises the following steps: The mixed solution B is reacted to obtain the Gd ion-porphyrin complex; the mixed solution B includes a Gd precursor, porphyrin and a solvent.

8. The method for preparing the nanozyme according to claim 7, characterized in that: The Gd precursor is selected from one or more of gadolinium chloride, gadolinium acetate, gadolinium nitrate and hydrates thereof, such as gadolinium acetate trihydrate; And / or, the porphyrin is selected from one of DTPA, DOTA and TCPP, preferably TCPP; And / or, the ratio of the amount of the Gd precursor to the amount of the porphyrin is (4-6):1, preferably 5:1; And / or, the solvent is DMF; And / or, the reaction is carried out under a protective gas, such as nitrogen; And / or, the reaction temperature is 95°C-105°C; And / or, the reaction time is 1-5h, for example 2h; And / or, the reaction step further includes cooling and drying steps, and the drying is preferably vacuum drying.

9. Use of the nanozyme according to any one of claims 1 to 4 in a magnetic resonance contrast agent.

10. A use of the nanozyme according to any one of claims 1 to 4 in removing active oxygen; Preferably, the application includes simulating the action of superoxide dismutase; Preferably, the application includes application in the preparation of anti-inflammatory drugs.

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