A double-concave disc-shaped nanometer manganese carbonate contrast agent and a preparation method thereof

Abstract

The application discloses a kind of double concave disc-shaped nanometer manganese carbonate contrast agent and preparation method thereof, belong to medical imaging contrast agent technical field, the preparation method of a kind of double concave disc-shaped nanometer manganese carbonate contrast agent, comprising the following steps: manganese acetate, cationic surfactant, micellar stabilizer and nanometer manganese carbonate stabilizer are added in water, then chloroform is added, stirring is dissolved, and inverse micelle stock solution is obtained;Under low-temperature stirring condition, sodium carbonate solution is added to the inverse micelle stock solution;After reaction is completed, the obtained solution is low-temperature centrifugation, and the double concave disc-shaped nanometer manganese carbonate contrast agent is obtained.The double concave disc-shaped nanometer manganese carbonate contrast agent provided by the application has a unique double concave disc-shaped morphology, and the unique double concave disc-shaped morphology gives the nanometer manganese carbonate contrast agent a larger specific surface area, and the larger specific surface area enables the double concave disc-shaped nanometer manganese carbonate contrast agent to coordinate with more water molecules, so that the double concave disc-shaped nanometer manganese carbonate contrast agent has a higher longitudinal relaxation rate in magnetic resonance imaging.

Description

Technical Field

[0001] This invention belongs to the field of medical imaging contrast agent technology, and in particular relates to a biconcave disc-shaped nano-manganese carbonate contrast agent and its preparation method. Background Technology

[0002] Contrast agents in magnetic resonance imaging (MRI) accelerate the relaxation of surrounding water molecules, thereby improving the contrast of MRI images. Contrast agents are generally ionic compounds of gadolinium (III), iron (III), and manganese (II), because these ions have a half-filled d-shell orbital structure, possessing the largest magnetic moment. For a contrast agent to exert its relaxation effect on water molecules, its paramagnetic center (paramagnetic ion) must influence the relaxation of water molecules; the more water molecules influenced, the better the relaxation performance. The relaxation rate is generally used as the evaluation criterion for relaxation performance and imaging capability.

[0003] There are two main types of existing magnetic resonance imaging contrast agents: paramagnetic gadolinium complexes and nano-manganese oxide (MnO4). x ), iron oxide (FeO) x Contrast agents. However, gadolinium ions are nephrotoxic; nano-manganese oxide and iron oxide often contain Mn. 3+ Mn 4+ and Fe 3+ It has oxidizing properties, which can disrupt the redox balance of cells and trigger inflammation (J. Wahsner, EM Gale, A. Rodríguez-Rodríguez, and P. Caravan, Chem. Rev. 2019, 119(2), 957. DOI: 10.1021 / acs.chemrev.8b00363).

[0004] Nano-manganese carbonate (MnCO3) is a novel manganese-based contrast agent containing only divalent Mn. 2+ Furthermore, it is rapidly metabolized in vivo and has better biocompatibility than nano-manganese oxide contrast agents. However, current nano-manganese carbonate contrast agents generally have a particle size ≥30nm, which results in a smaller specific surface area and fewer paramagnetic centers (Mn). 2+ The number of water molecules affected is limited, therefore the relaxation rate of these nano-manganese carbonate contrast agents is not high, generally <10 mM. -1 s -1 (Y. Cheng, S, Zhang, N, Kang, J, Huang, X, Lv, K, Wen, S, Ye, Z. Chen, X. Zhou, and L. Ren, ACS Appl. Mater. Interfaces2017, 9(22), 19296. DOI: 10.1021 / acsami.7b03087; T. Liu, Q. Wan, Y.Luo, M. Chen, C. Zou, M. Ma, X. Liu, and H. Chen, ACS Appl Mater Interfaces2019, 11(18), 16285. DOI: 10.1021 / acsami.9b02062).

[0005] Therefore, there is an urgent need in this field for a nano-manganese carbonate contrast agent with a higher specific surface area and a higher relaxation rate. Summary of the Invention

[0006] To address the above problems, this invention provides a biconcave disc-shaped nano-manganese carbonate contrast agent and its preparation method. To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent, comprising adding manganese acetate, a cationic surfactant, a micelle stabilizer and a nano-manganese carbonate stabilizer to water, then adding chloroform and stirring until uniformly dispersed to obtain a reversed micelle stock solution; adding sodium carbonate solution to the reversed micelle stock solution under low-temperature stirring conditions; after the reaction is completed, centrifuging the resulting solution at low temperature to obtain the biconcave disc-shaped nano-manganese carbonate contrast agent.

[0007] Furthermore, the nano-manganese carbonate stabilizer is sodium citrate.

[0008] Furthermore, the cationic surfactant is selected from tetraoctylammonium bromide.

[0009] Furthermore, the micelle stabilizer is polyvinylpyrrolidone, and the average molecular weight of the polyvinylpyrrolidone is 10,000.

[0010] The role of polyvinylpyrrolidone is to stabilize micelles and prevent them from breaking down.

[0011] Further, the molar ratio of manganese acetate, cationic surfactant and sodium carbonate is 1:(0.2~0.4):(0.1~0.2).

[0012] Furthermore, the volume ratio of water to chloroform is (1~1.5):100.

[0013] Furthermore, the temperature for both the low-temperature stirring and the low-temperature centrifugation is 0 °C.

[0014] The preparation method of the biconcave disk-shaped nano-manganese carbonate contrast agent provided by this invention is a reverse micelle method, which relies on micellar microreactors, asymmetric deposition, and differential crystal plane growth to achieve morphology control. The specific principle of this method is as follows: (1) Biconcave disc-shaped nano-manganese carbonate contrast agents were prepared using micellar microreactors. The cationic surfactant molecules are amphiphilic, with one end being a hydrophilic group that is soluble in water and the other end being a hydrophobic group that is soluble in nonpolar organic solvents. With the help of the surfactant, a small amount of aqueous solution in a nonpolar solvent will form micelles, i.e., a water core at the center, a nonpolar solvent in the surrounding environment, and a surfactant encapsulation at the interface, i.e., reverse micelles. The size of reverse micelles is generally at the nanoscale, and their water core forms a nanoscale microreactor.

[0015] (2) This invention prepares a biconcave disk-shaped nano-manganese carbonate contrast agent by asymmetric deposition. The surface energies of different crystal faces are greatly different. The cationic surfactant tetraoctylammonium bromide adsorbs the high-energy crystal face, preventing the deposition and growth of the crystal face in the axial direction. At this time, the newly generated manganese carbonate crystals are deposited quickly in the lateral (radial) direction, resulting in lateral extension growth and forming a disk-shaped morphology.

[0016] (3) During the rapid lateral growth of the crystal, the cationic surfactant tetraoctylammonium bromide cannot be adsorbed on the upper and lower end faces (disk axial direction) of the newly formed crystal in time; therefore, the edge face of the lateral manganese carbonate nanocrystals can continue to grow along the axial direction, eventually forming a biconcave disk structure with convex edges and a concave center. The above mechanisms work together to give the manganese carbonate nanocontrast agent a characteristic biconcave disk morphology.

[0017] Secondly, the present invention provides a biconcave disc-shaped nano-manganese carbonate contrast agent prepared by the preparation method described above. The biconcave disc-shaped nano-manganese carbonate contrast agent is biconcave disc-shaped with an average particle diameter of 6.3 to 7.5 nm and an average thickness of 1.1 nm.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: The biconcave disc-shaped nano-manganese carbonate contrast agent provided by this invention possesses a unique biconcave disc morphology, with an average particle diameter of 6.3~7.5 nm and an average thickness of 1.1 nm. Its chemical composition is manganese carbonate. The unique biconcave disc morphology endows the nano-manganese carbonate contrast agent with a large specific surface area; BET adsorption experiments demonstrate that its specific surface area reaches 164.2465 m². 2 / g. The large specific surface area allows the biconcave disk-shaped manganese carbonate nanocontrast agent to coordinate with more water molecules, resulting in a high longitudinal relaxation rate (13.84 mM) in magnetic resonance imaging. -1 s -1 This effectively improves the contrast of magnetic resonance imaging. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the biconcave disc-shaped nano-manganese carbonate contrast agent prepared according to the present invention; Figure 2 The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1, where a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, c) is a histogram of the disc diameter distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent, and d) is a histogram of the disc thickness distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent. Figure 3 X-ray powder diffraction pattern of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1 and comparison with standard card JCPDS#83-1763; Figure 4 a) is the nitrogen adsorption-desorption surface area curve of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1, and b) is the t-plot curve of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1. Figure 5 a) Longitudinal relaxation weighted magnetic resonance imaging of the biconcave disk-shaped nano-manganese carbonate contrast agent prepared in Example 1 at different concentrations; b) Linear fitting relationship between longitudinal relaxation rate (1 / T1) and manganese ion concentration. Figure 6 a) is a longitudinal relaxation-weighted magnetic resonance imaging of the abdomen of mice with liver metastases before injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1; b) is a longitudinal relaxation-weighted magnetic resonance imaging of the abdomen of mice with liver metastases after injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1. Figure 7 a) is a longitudinal relaxation-weighted magnetic resonance imaging of the tumor site in a subcutaneous tumor-bearing mouse before injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1; b) is a longitudinal relaxation-weighted magnetic resonance imaging of the tumor site in a subcutaneous tumor-bearing mouse after injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1. Figure 8The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 2, where a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, c) is a histogram of the disc diameter distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent, and d) is a histogram of the disc thickness distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent. Figure 9 The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 3, where a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent, c) is a histogram of the disc diameter distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent, and d) is a histogram of the disc thickness distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent. Figure 10 A schematic diagram illustrating the coordination of the biconcave disc-shaped nano-manganese carbonate contrast agent with water molecules and the enhanced relaxation provided by the present invention. Figure 11 This is a schematic diagram illustrating the principle of synthesizing biconcave disc-shaped nano-manganese carbonate contrast agents using the reverse micelle method according to the present invention. Figure 12 a) is a TEM (transmission electron microscope) morphology image of the nano-manganese carbonate prepared in Comparative Example 1; b) is a linear fitting relationship between the longitudinal relaxation rate (1 / T1) and the manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 1. Figure 13 a) is a TEM (transmission electron microscope) morphology image of the nano-manganese carbonate prepared in Comparative Example 2; b) is a linear fitting relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 2. Figure 14 a) is a TEM (transmission electron microscope) morphology image of the nano-manganese carbonate prepared in Comparative Example 3; b) is a linear fitting relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 3. Figure 15 a) is a TEM (transmission electron microscope) morphology image of the nano-manganese carbonate prepared in Comparative Example 4; b) is a linear fitting relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 4. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] Increasing the specific surface area of ​​nano-manganese carbonate contrast agents, thereby influencing the relaxation of more water molecules, is key to improving the relaxation rate. There are two ways to increase the specific surface area: one is to reduce the particle size; the other is to change the morphology to allow more Mn to relax. 2+ Exposed to the particle surface. This invention provides a method for increasing specific surface area through a special morphology. An embodiment of this invention provides a method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent. Manganese acetate, a cationic surfactant, a micelle stabilizer, and a nano-manganese carbonate stabilizer are added to water, followed by the addition of chloroform. The mixture is stirred until dissolved to obtain a reversed-phase micelle stock solution. Under low-temperature stirring conditions, a sodium carbonate solution is added to the reversed-phase micelle stock solution, and the resulting solution is centrifuged at low temperature to obtain the biconcave disc-shaped nano-manganese carbonate contrast agent.

[0027] In some preferred embodiments of the present invention, the nano-manganese carbonate stabilizer is sodium citrate.

[0028] In some preferred embodiments of the present invention, the cationic surfactant is selected from tetraoctylammonium bromide.

[0029] In some preferred embodiments of the present invention, the micelle stabilizer is polyvinylpyrrolidone, and the average molecular weight of the polyvinylpyrrolidone is 10,000.

[0030] In some preferred embodiments of the present invention, the molar ratio of manganese acetate, cationic surfactant and sodium carbonate is 1:(0.2~0.4):(0.1~0.2), (exemplary ratios are 1:0.2:0.15, 1:0.24:0.1, 1:0.4:0.2).

[0031] In some preferred embodiments of the present invention, the volume ratio of water to chloroform is (1~1.5):100 (exemplary, 1:100, 1.5:100).

[0032] In some preferred embodiments of the present invention, the temperature of both the low-temperature stirring and the low-temperature centrifugation is 0 °C.

[0033] Figure 1 The flowchart illustrates the biconcave disc-shaped nano-manganese carbonate contrast agent prepared according to this invention.

[0034] The preparation method of the biconcave disk-shaped nano-manganese carbonate contrast agent provided by the present invention is the reverse micelle method, which relies on micelle microreaction vessels, asymmetric deposition, and differential crystal plane growth to achieve morphology control. Figure 11 This is a schematic diagram illustrating the principle of synthesizing biconcave disc-shaped nano-manganese carbonate contrast agents using the reverse micelle method according to the present invention.

[0035] The present invention also provides a biconcave disc-shaped nano-manganese carbonate contrast agent prepared by the preparation method described above. The biconcave disc-shaped nano-manganese carbonate contrast agent is biconcave disc-shaped with an average particle diameter of 6.3 ~ 7.5 nm and an average thickness of 1.1 nm.

[0036] Figure 10 This is a schematic diagram illustrating the coordination of the biconcave disc-shaped nano-manganese carbonate contrast agent with water molecules and the enhanced relaxation provided by the present invention.

[0037] The room temperature in this invention refers to 25 ± 2 °C.

[0038] Example 1: A method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent S1, 173 mg (1.00 mmol) anhydrous manganese acetate, 109.4 mg (0.2 mmol) tetraoctylammonium bromide, 25 mg (0.0025 mmol) polyvinylpyrrolidone (M W=10000) and 12.9 mg (0.05 mmol) of anhydrous sodium citrate were dissolved in 1 mL of ultrapure water. The resulting aqueous solution was added to a round-bottom flask containing 100 mL of chloroform and magnetically stirred until uniformly dispersed to obtain the reversed micelle stock solution. S2. Stir the reversed micelle stock solution prepared in step S1 at 0 ℃. While stirring, slowly add 0.3 mL of sodium carbonate solution (0.5 mol / L) dropwise into the reversed micelle stock solution. Continue stirring for 1 h. Then, centrifuge the resulting mixed solution at low temperature for 10 min (0 ℃, 8000 rpm), discard the supernatant, and the resulting precipitate is the biconcave disc-shaped nano-manganese carbonate contrast agent.

[0039] Figure 2 The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1. a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; c) is a histogram showing the diameter distribution of the discs; and d) is a histogram showing the thickness distribution of the discs. Statistical analysis revealed that the diameter of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1 was 6.6–7.8 nm, with an average diameter of 7.0 nm, and the thickness was 0.8–1.4 nm, with an average thickness of 1.1 nm.

[0040] Figure 3 The X-ray powder diffraction pattern of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1 and the comparison diagram with the standard card JCPDS#83-1763 show that the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1 is manganese carbonate.

[0041] Figure 4 In Figure a), nitrogen adsorption-desorption surface area curve of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1 is shown; in Figure b), t-plot curve of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1 is shown. The specific surface area of ​​the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 1 was calculated to be 164.2465 m². 2 / g.

[0042] The biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1 was added to phosphate buffer (pH = 7.4), and the manganese concentration was determined by atomic absorption spectrometry. The solution was then diluted to obtain biconcave disc-shaped nano-manganese carbonate contrast agent solutions with different manganese concentrations. Figure 5(a) Longitudinal relaxation-weighted magnetic resonance imaging of the biconcave disk-shaped manganese carbonate nano-contrast agent prepared in Example 1 at different manganese concentrations; (b) Linear fitting relationship between longitudinal relaxation rate (1 / T1) and manganese ion concentration, indicating that the biconcave disk-shaped manganese carbonate nano-contrast agent prepared in Example 1 has good imaging effect and a high relaxation rate of 13.84 mM. -1 s -1 .

[0043] The 0.072 mg biconcave disc-shaped nano-manganese carbonate contrast agent prepared in this embodiment was dissolved in 0.2 mL of phosphate buffer (pH = 7.4) and injected via the tail vein into mice with liver metastases and mice with subcutaneous tumors, respectively. The injection dose was 4 mg / kg. Two hours after injection, longitudinal relaxation-weighted magnetic resonance imaging of the abdomen and longitudinal relaxation-weighted magnetic resonance imaging of the tumor site were performed, respectively.

[0044] Figure 6 Image a) shows longitudinal relaxation-weighted magnetic resonance imaging (MRI) of the abdomen of mice with liver metastases before injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1; image b) shows longitudinal relaxation-weighted MRI of the abdomen of mice with liver metastases after injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1. Comparison of images before and after injection shows a significant improvement in the contrast between liver metastases and normal liver tissue, indicating that the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in this invention can effectively improve tumor contrast and enhance the imaging effect.

[0045] Figure 7 Image a) shows longitudinal relaxation-weighted magnetic resonance imaging (MRI) of the tumor site in subcutaneous tumor-bearing mice before injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1; image b) shows longitudinal relaxation-weighted MRI of the tumor site in subcutaneous tumor-bearing mice after injection of the biconcave disc-shaped nano-manganese carbonate contrast agent prepared in Example 1. Comparison of images before and after injection shows a significant improvement in contrast between the subcutaneous tumor and normal subcutaneous tissue, indicating that the biconcave disc-shaped nano-manganese carbonate contrast agent can effectively improve tumor contrast and enhance the imaging effect.

[0046] Example 2: A method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent S1, 173 mg (1.00 mmol) anhydrous manganese acetate, 131.3 mg (0.24 mmol) tetraoctylammonium bromide, and 25 mg polyvinylpyrrolidone (M W =10000) and 12.9 mg (0.05 mmol) sodium citrate were dissolved in 1 mL of ultrapure water. The resulting aqueous solution was added to a round-bottom flask containing 100 mL of chloroform and magnetically stirred until uniformly dispersed to obtain the reversed micelle stock solution. S2. Stir the reversed micelle stock solution a prepared in step S1 at 0 ℃. At the same time, slowly add 0.2 mL of sodium carbonate solution (0.5 mol / L) dropwise into the reversed micelle stock solution and continue stirring for 1 h. Then, centrifuge the resulting mixed solution at low temperature for 10 min (0 ℃, 8000 rpm), discard the supernatant, and the resulting precipitate is the biconcave disc-shaped nano-manganese carbonate contrast agent.

[0047] Figure 8 The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 2. a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; c) is a histogram showing the diameter distribution of the discs; and d) is a histogram showing the thickness distribution of the discs. Statistical analysis revealed that the diameter of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 2 was 6.0–7.0 nm, with an average diameter of 6.3 nm, and the thickness was 0.8–1.4 nm, with an average thickness of 1.1 nm.

[0048] Example 3: A method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent S1, 173 mg (1.00 mmol) anhydrous manganese acetate, 218.7 mg (0.4 mmol) tetraoctylammonium bromide, and 40 mg polyvinylpyrrolidone (M W =10000) and 25.8 mg (0.1 mmol) sodium citrate were dissolved in 1.5 mL of ultrapure water. The resulting aqueous solution was added to a round-bottom flask containing 100 mL of chloroform and magnetically stirred until uniformly dispersed to obtain the reversed micelle stock solution. S2. Stir the reversed micelle stock solution a prepared in step S1 at 0 ℃. At the same time, slowly add 0.4 mL of sodium carbonate solution (0.5 mol / L) dropwise into the reversed micelle stock solution and continue stirring for 1 h. Then, centrifuge the resulting mixed solution at low temperature for 10 min (0 ℃, 8000 rpm), discard the supernatant, and the resulting precipitate is the biconcave disc-shaped nano-manganese carbonate contrast agent.

[0049] Figure 9The images show the TEM (transmission electron microscope) morphology and size distribution of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 3. a) is a low-magnification TEM image (scale bar 50 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; b) is a high-magnification TEM image (scale bar 10 nm) of the biconcave disc-shaped manganese carbonate nano-contrast agent; c) is a histogram showing the diameter distribution of the discs; and d) is a histogram showing the thickness distribution of the discs. Statistical analysis revealed that the diameter of the biconcave disc-shaped manganese carbonate nano-contrast agent prepared in Example 3 was 7.1–8.1 nm, with an average diameter of 7.5 nm, and the thickness was 0.8–1.4 nm, with an average thickness of 1.1 nm.

[0050] Comparative Example 1 Same as Example 1, except that in step S1, the cationic surfactant tetraoctylammonium bromide is replaced with sodium dodecyl sulfate. The specific preparation process is as follows: S1, 173 mg (1.00 mmol) anhydrous manganese acetate, 57.7 mg (0.2 mmol) sodium dodecyl sulfate, and 25 mg polyvinylpyrrolidone (M W =10000) and 12.9 mg (0.05 mmol) sodium citrate were dissolved in 1 mL of ultrapure water. The resulting aqueous solution was added to a round-bottom flask containing 100 mL of chloroform and magnetically stirred until uniformly dispersed to obtain the reversed micelle stock solution. S2, same as Example 1.

[0051] Figure 12 Image a) shows the TEM (transmission electron microscopy) morphology of the nano-manganese carbonate prepared in Comparative Example 1; image b) shows the linear relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 1. Because sodium dodecyl sulfate cannot specifically bind to the high-energy crystal planes of manganese carbonate, the resulting nano-manganese carbonate is conventionally prismatic and relatively large in size. Its longitudinal relaxation rate is only 3.44 mM. -1 s -1 .

[0052] Comparative Example 2 Same as Example 1, except that the micelle stabilizer polyvinylpyrrolidone was not added in step S1. The specific preparation process is as follows: S1. Dissolve 173 mg (1.00 mmol) anhydrous manganese acetate, 109.4 mg (0.2 mmol) tetraoctylammonium bromide and 12.9 mg (0.05 mmol) sodium citrate in 1 mL of ultrapure water. Add the resulting aqueous solution to a round-bottom flask containing 100 mL of chloroform and stir magnetically until evenly dispersed to obtain a reversed micelle stock solution. S2, same as Example 1.

[0053] Figure 13 Image a) shows the TEM (transmission electron microscopy) morphology of the nano-manganese carbonate prepared in Comparative Example 2; image b) shows the linear relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 2. Due to the absence of the micelle stabilizer polyvinylpyrrolidone, the micelles are prone to breakage and adhesion to other micelles, resulting in interconnections between the nano-manganese carbonate particles. Furthermore, due to the instability of the micelles, the cationic surfactant tetraoctylammonium bromide cannot stably bind to the high-energy crystal planes of manganese carbonate to inhibit its growth, thus failing to form a disk-like morphology. Its longitudinal relaxation rate is only 6.97 mM. -1 s -1 .

[0054] Comparative Example 3 Same as Example 1, except that in step S1, chloroform is replaced with cyclohexane.

[0055] Figure 14 Image a) shows the TEM (transmission electron microscopy) morphology of the nano-manganese carbonate prepared in Comparative Example 3; image b) shows the linear relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 3. Due to the poor micelle-forming ability of the cationic surfactant tetraoctylammonium bromide in cyclohexane, nano-manganese carbonate particles with uniform morphology and suitable size could not be obtained. The electron microscopy images show that some manganese carbonate exhibits a porous structure. Literature reports that alkylammonium bromide acts as a mesoporous template agent, which may explain this phenomenon. The nano-manganese carbonate prepared in Comparative Example 3 has a longitudinal relaxation rate of only 2.37 mM. -1 s -1 .

[0056] Comparative Example 4 S1, Same as Example 1; S2. Stir the reversed micelle stock solution prepared in step S1 at room temperature. At the same time, slowly add 0.3 mL of sodium carbonate solution (0.5 mol / L) dropwise into the reversed micelle stock solution and continue stirring for 1 h. Then, centrifuge the resulting mixed solution at room temperature for 10 min, discard the supernatant, and the resulting precipitate is the nano-manganese carbonate contrast agent.

[0057] Figure 15 Image a) shows the TEM (transmission electron microscopy) morphology of the nano-manganese carbonate prepared in Comparative Example 4; image b) shows the linear relationship between the longitudinal relaxation rate (1 / T1) and manganese ion concentration of the nano-manganese carbonate prepared in Comparative Example 4. Because the higher temperature disrupted the specific binding between the cationic surfactant tetraoctylammonium bromide and the high-energy crystal plane of manganese carbonate, the growth of this crystal plane could not be inhibited, resulting in nano-manganese carbonate with a conventional prismatic shape similar to that of Comparative Example 1. Its longitudinal relaxation rate was only 3.56 mM.-1 s -1 .

[0058] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a biconcave disc-shaped nano-manganese carbonate contrast agent, characterized in that, Includes the following steps: Manganese acetate, cationic surfactant, micelle stabilizer and nano-manganese carbonate stabilizer were added to water, then chloroform was added, and the mixture was stirred until it was evenly dispersed to obtain a reversed micelle stock solution; sodium carbonate solution was added to the reversed micelle stock solution under low temperature stirring conditions. After the reaction was completed, the resulting solution was centrifuged at low temperature to obtain the biconcave disc-shaped nano-manganese carbonate contrast agent.

2. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The nano-manganese carbonate stabilizer is sodium citrate.

3. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The cationic surfactant is tetraoctylammonium bromide.

4. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The micelle stabilizer is polyvinylpyrrolidone, and the average molecular weight of the polyvinylpyrrolidone is 10,000.

5. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The molar ratio of manganese acetate, cationic surfactant, and sodium carbonate is 1:(0.2~0.4):(0.1~0.2).

6. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The volume ratio of water to chloroform is (1~1.5):

100.

7. The method for preparing the biconcave disc-shaped nano-manganese carbonate contrast agent according to claim 1, characterized in that, The temperature for both the low-temperature stirring and low-temperature centrifugation is 0 ℃.

8. A biconcave disc-shaped nano-manganese carbonate contrast agent prepared by the preparation method according to claims 1-7, characterized in that, The biconcave disc-shaped nano-manganese carbonate contrast agent is biconcave disc-shaped, with an average particle diameter of 6.3 ~ 7.5 nm and an average thickness of 1.1 nm.

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