Carbon-doped molybdenum-based MOF-derived porous MRI probe and preparation method and anti-infection application thereof

Abstract

The invention discloses a carbon-doped molybdenum-based MOF (Metal Organic Framework) derived porous MRI (Magnetic Resonance Imaging) probe as well as a preparation method and anti-infection application thereof, and belongs to the technical field of nano medicines. According to the scheme, the method comprises the steps that a copper-molybdenum-based precursor is subjected to high-temperature sintering in an inert atmosphere, then NH3 is introduced, heat preservation is continued, a nitridation reaction is promoted, and a carbon-doped MoN MOF material is prepared; and immersing the material into a gadolinium salt solution, stirring, centrifuging, washing and drying to obtain the gadolinium ion-loaded porous MRI probe. According to the invention, efficient loading and stable fixation of gadolinium ions are realized, and the MRI imaging contrast ratio is improved while the biotoxicity risk is reduced. The porous skeleton structure is combined with the carbon doping design, so that the structural stability of the material in a biological environment is enhanced, and the performance maintenance of the probe during long-term use in vivo is ensured. The conductive network formed by the nitridation reaction further optimizes the magnetic response characteristic, and provides a basis for high-sensitivity imaging.

Description

Technical Field

[0001] The present invention belongs to the field of nanomedicine technology, and specifically relates to a carbon-doped molybdenum-based MOF-derived porous MRI probe, a preparation method thereof, and anti-infection applications. Background Art

[0002] Magnetic resonance imaging (MRI) is a non-invasive imaging technique widely used in modern medicine, offering excellent soft tissue contrast and high spatial resolution. However, MRI inherently has low contrast, requiring the use of exogenous contrast agents to enhance imaging. Traditional gadolinium-based (Gd³⁺) contrast agents are widely used due to their strong magnetism and excellent imaging performance, but their in vivo toxicity has sparked widespread concern. In particular, in patients with renal insufficiency, Gd³⁺-based contrast agents can cause serious side effects, such as gadolinium deposition disease and nephrogenic systemic fibrosis (NSF). Therefore, developing an MRI probe that enhances imaging performance while exhibiting good biocompatibility has become a research priority in the field of medical imaging.

[0003] Metal-organic frameworks (MOFs) are a class of porous materials composed of metal ions or clusters linked to organic ligands through coordination bonds. They possess highly tunable pore structures, large specific surface areas, and excellent chemical stability. Molybdenum-based MOFs, due to their unique electronic structure and excellent electrical conductivity, have shown great potential in a variety of applications, particularly as carrier materials for MRI probes. The introduction of molybdenum imparts MOF materials with excellent electron transfer capabilities, which is crucial for enhancing magnetic resonance signals. Furthermore, the chemical stability of molybdenum-based MOFs ensures their structural integrity in complex biological environments, reducing the risk of degradation during in vivo use.

[0004] Although molybdenum-based MOF materials have promising applications in MRI probes, their performance still needs to be improved, such as in terms of dispersibility and biocompatibility in biological environments. Furthermore, existing molybdenum-based MOF materials have poor thermal stability and photothermal effects, and cannot remain stable in the body for long periods of time. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a carbon-doped molybdenum-based MOF-derived porous MRI probe, its preparation method and anti-infection application, so as to solve the technical problems of poor thermal stability and photothermal effect of existing MRI probes prepared by molybdenum-based MOF. The probe constructs a porous molybdenum-based MOF structure through carbon doping technology and loads gadolinium ions (Gd³⁺) on it, thereby realizing the simultaneous integration of MRI precise diagnosis and photothermal therapy of infected tissues.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF, comprising the following steps: 1) The copper-molybdenum-based precursor is first sintered at high temperature under an inert atmosphere, and then NH3 is introduced and kept warm to promote the nitridation reaction to obtain a carbon-doped MoN MOF material; 2) The carbon-doped MoN MOF material was immersed in a gadolinium salt solution, stirred thoroughly at room temperature, and centrifuged to separate the solid material. The solid material was then washed and dried to obtain a carbon-doped MoN MOF material that adsorbed gadolinium ions, namely a carbon-doped molybdenum-based MOF-derived porous MRI probe.

[0007] Preferably, the thermal stability issue of molybdenum-based MOF materials during sintering is addressed by limiting the specific process parameters for high-temperature sintering. Specifically, using argon as an inert atmosphere can prevent side reactions with oxygen at high temperatures, thus preventing structural damage. A slow heating rate of 2°C / min can reduce thermal stress cracking caused by sudden temperature changes within the material, ensuring the integrity of the skeleton structure. A temperature range of 800-900°C is set to meet the activation energy requirements for carbon doping while avoiding excessive temperatures that could lead to over-sintering and pore collapse. After introducing NH3, the treatment is maintained at this temperature for 2-4 hours to allow the nitridation reaction to proceed fully and promote the transformation of the copper-molybdenum-based precursor to a stable crystalline form, forming a carbon-doped MoN MOF material with high crystallinity. Too short a holding time prevents nitrogen from fully penetrating the molybdenum-based skeleton, affecting the formation of the carbon-doped structure. Too long a holding time can lead to excessive nitridation, resulting in collapse of the material's pore structure. The specific time window of 2-4 hours ensures sufficient reaction between NH3 and the copper-molybdenum precursor, promoting the stable formation of Mo-N bonds, while also maintaining the integrity of the MOF's octahedral framework through the synergistic effect of carbon doping. This time parameter, by balancing reaction kinetics and thermodynamics, optimizes both the depth of the nitridation reaction and the structural stability of the material, providing a stable porous support for the subsequent efficient loading of gadolinium ions. These parameters work synergistically to produce a support material with both high thermal stability and a porous structure, providing a stable substrate for subsequent gadolinium ion loading.

[0008] Furthermore, in step 2), the gadolinium salt solution is selected to be a Gd(NO3)3·6H2O solution with a concentration of 0.01~0.1 M.

[0009] By limiting the concentration range and specific compound type of the gadolinium salt solution, controlled loading and uniform distribution of gadolinium ions were achieved. A 0.01–0.1 M Gd(NO₃)₃·6H₂O solution was selected. The lower concentration limit ensured sufficient contact between gadolinium ions and the pore surfaces of the carbon-doped MoN MOF material, preventing insufficient adsorption at too low a concentration and thus compromising MRI signal enhancement. The upper concentration limit prevented excessive concentration from causing oversaturation and aggregation of gadolinium ions within the pores, which could lead to structural damage or local toxicity. Gadolinium nitrate hexahydrate was used as the gadolinium source. Its nitrate ions promote interactions with the surface charge of the MOF material, enhancing adsorption stability. The hexahydrate form, through its crystalline water, modulates the solution osmotic pressure, preventing material aggregation caused by salting-out. The synergistic effect of this concentration range and compound type ensured efficient loading of gadolinium ions while achieving uniform dispersion within the nanopores through matching physicochemical properties, ultimately improving the biocompatibility and imaging performance of the probe.

[0010] Preferably, the copper-molybdenum-based precursor has an octahedral structure and is prepared according to the following method: The copper source, amino acid and phosphomolybdic acid hydrate were dissolved in deionized water, stirred at room temperature for 1 h, and then an ethanol solution of an organic ligand was injected therein for complexation and coordination, and the reaction was stirred at room temperature to obtain the product.

[0011] More preferably, the molar ratio of the copper source, amino acid and phosphomolybdic acid is (10-15): (5-10): (16-24).

[0012] More preferably, the copper source is copper acetate, copper nitrate or copper chloride; the amino acid is L-glutamic acid or aspartic acid; and the ethanol solution of the organic ligand is 1,3,5-benzenetricarboxylic acid ethanol solution with a concentration of 0.5-1.0 mmol / L.

[0013] The present invention also discloses a carbon-doped molybdenum-based MOF-derived porous MRI probe prepared by the above-mentioned preparation method. The porous MRI probe has an octahedral structure, and Gd³⁺ is uniformly loaded in the nanopores.

[0014] The octahedral structure originates from a specific preparation process of a copper-molybdenum-based precursor. Its regular geometric form can enhance the material's dispersibility in the biological environment and prevent gadolinium ion leakage due to structural collapse. The carbon-doped molybdenum-based MOF framework provides a high specific surface area through its porous properties, making the nanopores a stable anchoring point for Gd³⁺, ensuring that the ions are evenly dispersed rather than aggregated. This spatial confinement effect not only reduces the toxicity risk of free gadolinium ions, but also significantly improves MRI signal response by enhancing local magnetic field perturbations. The integrity of the octahedral structure ensures the structural stability of the material during in vivo circulation, while the uniform loading characteristics of the nanopores avoid the signal unevenness problem caused by ion agglomeration in traditional contrast agents.

[0015] The present invention also discloses the use of the carbon-doped molybdenum-based MOF-derived porous MRI probe in the preparation of an MRI contrast agent.

[0016] Preferably, the MRI contrast agent is capable of enhancing the MRI signal intensity of the infected area.

[0017] Compared with the existing technology, the present invention has the following beneficial effects: The present invention has significant technical advantages, especially in terms of material synthesis process, functional integration and clinical application potential, showing unique innovation and superiority. Specifically, it is reflected in: First, the present invention optimizes the electronic structure of molybdenum-based MOF materials through a precisely controlled carbon doping process. Carbon doping not only improves the electrical conductivity of the material, but also increases its thermal stability during high-temperature treatment, thereby ensuring the structural integrity and functional consistency of the material in subsequent synthesis steps. The present invention has made a breakthrough in the multifunctional integration of materials. By introducing molybdenum elements and carbon doping into MOF materials, the photothermal conversion efficiency of the material is significantly improved, enabling it to have the ability of photothermal therapy. The realization of this functional integration is due to the improvement of the electrical conductivity and thermal stability of the material by carbon doping technology, which ensures the stability of the material and efficient energy conversion during photothermal therapy.

[0018] Second, by sintering a highly ordered octahedral copper-molybdenum-based precursor under an inert atmosphere and combining it with a specific heating rate control, the pore structure of the resulting carbon-doped MoN MOF can be precisely controlled, providing an ideal carrier for the subsequent efficient and uniform loading of gadolinium ions (Gd³⁺). This optimized porous structure allows the gadolinium ions to be fully and uniformly adsorbed within the material's pores, directly leading to a significant increase in their longitudinal relaxation rate (r1), thereby greatly enhancing the material's T1-weighted magnetic resonance imaging (MRI) contrast.

[0019] Third, the gadolinium-loaded carbon-doped molybdenum-based MOF material not only enhances signal intensity in MRI imaging but also, through its excellent biocompatibility and chemical stability, reduces the potential toxicity risk of gadolinium-based contrast agents in vivo. This innovative functional integration holds great promise for clinical applications, particularly in the integration of precise diagnosis of infection sites and photothermal therapy.

[0020] Fourth, the present invention's synthesis process is simple and controllable, with high reproducibility and consistency, making it suitable for large-scale production and practical application. By achieving efficient gadolinium ion loading and uniform carbon doping under mild conditions, the present invention not only ensures high-performance material output, but also reduces production costs and process complexity, further enhancing the technology's potential for application in medical imaging and therapeutics. These synthetic advantages enable the present invention to demonstrate superior performance not only in the laboratory but also lay a solid foundation for its clinical translation.

[0021] As can be seen, the present invention effectively combines the advantages of both by loading gadolinium ions into carbon-doped molybdenum-based MOF materials, leveraging the imaging enhancement benefits of gadolinium ions while also improving the material's stability and photothermal performance through the MOF's porous structure and carbon doping. Gadolinium-loaded molybdenum-based MOF materials enable precise imaging of target tissues or lesions while reducing the risk of gadolinium ion toxicity in the body.

[0022] Furthermore, the present invention treats the copper-molybdenum-based precursor in Ar with a precisely controlled heating rate (2°C / min) and introduces NH3 for nitridation, critically achieving simultaneous carbon doping. This process not only optimizes the material's electronic structure but also significantly enhances its high-temperature thermal stability, ensuring the integrity of the material's structure and functional consistency in subsequent steps.

[0023] Furthermore, during the synthesis process, the copper-molybdenum-based precursor used forms a highly ordered octahedral structure through complex coordination reactions. This structure provides an ideal matrix for subsequent carbon doping and gadolinium ion loading. This porous structure not only increases the material's specific surface area but also enhances the adsorption efficiency of Gd³⁺, making gadolinium ion loading more uniform and significantly improving MRI imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a SEM image of the carbon-doped molybdenum-based MOF porous MRI probe prepared in Example 1 of the present invention; Figure 2 This is the UV-Vis-NIR spectrum of the carbon-doped molybdenum-based MOF porous MRI probe prepared in Example 2 of the present invention; Figure 3 This is a photothermal temperature rise curve of a carbon-doped molybdenum-based MOF porous MRI probe prepared in Example 3 of the present invention; Figure 4 This is an in vitro MRI image of the carbon-doped molybdenum-based MOF porous MRI probe prepared in Example 4; Figure 5 This is a diagram showing the antibacterial effect of the carbon-doped molybdenum-based MOF porous MRI probe prepared in Example 4. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] The present invention is described in further detail below with reference to the accompanying drawings: This application proposes a preparation method comprising the following steps: The copper-molybdenum-based precursor is first sintered at high temperature under an inert atmosphere, and then NH3 is introduced and kept warm to promote the nitridation reaction to obtain a carbon-doped MoN MOF material; this material is immersed in a gadolinium salt solution, and after stirring, centrifugation, washing and drying, a porous MRI probe loaded with gadolinium ions is obtained.

[0028] Specifically, a stable porous skeleton structure is formed under the protection of inert gas during the high-temperature sintering stage to avoid pore collapse caused by metal oxidation. Subsequently, NH3 is introduced to trigger the nitridation reaction. The doping of carbon elements not only improves the conductivity of the material, but also enhances the skeleton strength through synergistic effects with molybdenum. The resulting carbon-doped MoN MOF material has a high specific surface area and uniform pore distribution, providing sufficient active sites for subsequent gadolinium ion loading. During the impregnation process, the ions in the gadolinium salt solution diffuse into the pores and achieve uniform adsorption under stirring conditions at room temperature. The centrifugation and drying steps retain the loading structure, and finally a probe material with a stable gadolinium ion distribution is obtained.

[0029] Compared with the prior art, traditional gadolinium-based contrast agents directly use free ions, which leads to biological toxicity. However, the present invention fixes gadolinium ions inside the pores through the confinement effect of porous materials, significantly reducing the risk of free ion release. Conventional molybdenum-based MOF materials are prone to structural collapse when treated at high temperatures. The present invention overcomes the problem of poor thermal stability by forming a stable MoN structure while maintaining porous properties through the synergistic effect of carbon doping and nitridation reactions. In addition, the nitridation treatment gives the material higher conductivity, which is beneficial to enhancing the magnetic resonance signal response. Therefore, the present invention can achieve efficient loading and stable fixation of gadolinium ions, while improving MRI imaging contrast and reducing the risk of biological toxicity. The porous skeleton structure combined with the carbon doping design enhances the structural stability of the material in the biological environment, ensuring that the performance of the probe is maintained during long-term use in the body. The conductive network formed by the nitridation reaction further optimizes the magnetic response characteristics, providing a basis for high-sensitivity imaging.

[0030] Specifically, a carbon-doped molybdenum-based MOF-derived porous MRI probe and its anti-infection application include the following steps: Step 1: Dissolve the copper source, amino acid, and phosphomolybdic acid hydrate in deionized water, stir at room temperature for 1 hour, inject an organic ligand ethanol solution into the solution for complexation, and react with stirring at room temperature to obtain a copper-molybdenum-based precursor, namely, NENU-5 octahedron; The molar ratio of the copper source, amino acid and phosphomolybdic acid is (10-15) mmol: (5-10) mmol: (16-24) mmol.

[0031] The copper source is one of copper acetate, copper nitrate and copper chloride.

[0032] Amino acids are one of L-glutamic acid and aspartic acid, which contain two carboxyl groups and one amino group.

[0033] The organic ligand ethanol solution is 1,3,5-benzenetricarboxylic acid ethanol solution, and its concentration is 0.5-1.0 mmol / L.

[0034] Step 2: NENU-5 precursor (0.1 g) was placed in a tube furnace. Under Ar protection, the furnace temperature was raised to 800°C–900°C at a rate of 2°C / min and maintained at this temperature for 1–3 hours. NH3 was then introduced into the furnace, and the temperature was maintained for another 2–4 hours in the NH3 flow to promote the nitridation reaction, thereby forming a carbon-doped MoN MOF structure.

[0035] Step 3: 0.05 g of dried MoN MOF material was placed in a 0.01–0.1 M solution of Gd(NO₃)₃·6H₂O and magnetically stirred at room temperature for 12 h to allow the gadolinium ions to fully adsorb into the pores of the MOF material. The solid material was then separated by centrifugation and washed multiple times with deionized water to remove unadsorbed gadolinium ions. Finally, the solid material was dried in a vacuum oven at 60°C to constant weight, yielding a carbon-doped MoN MOF material adsorbing gadolinium ions.

[0036] The carbon-doped molybdenum-based MOF porous MRI probe was tested for antibacterial efficiency (Escherichia coli, Staphylococcus aureus) by plate count method. Test conditions: bacterial density was 2.0×10 6 CFU / mL, incubation temperature 37℃ ± 2℃, antibacterial dose 80 μg / mL; 980 nm laser irradiation power 1 W / cm 2 , the irradiation time is 10 min. Example 1

[0037] A carbon-doped molybdenum-based MOF-derived porous MRI probe and its anti-infection application, comprising the following steps: Step 1: Dissolve copper acetate, L-glutamic acid, and phosphomolybdic acid hydrate in deionized water at a ratio of 10 mmol: 5 mmol: 16 mmol, and stir at room temperature for 1 h. Then, inject 0.5 mmol / L 1,3,5-benzenetricarboxylic acid ethanol solution into the solution for complexation and coordination. Stir the reaction at room temperature to obtain NENU-5 octahedron. Step 2: NENU-5 precursor (0.1 g) was placed in a tube furnace. Under Ar protection, the furnace temperature was raised to 800°C at a rate of 2°C / min and maintained at this temperature for 1 hour. Subsequently, NH3 was introduced into the furnace and the temperature was maintained for another 2 hours in the NH3 flow to promote the nitridation reaction, thereby forming a carbon-doped MoN MOF structure.

[0038] Step 3: 0.05 g of dried MoN MOF material was placed in a 0.01 mol / L Gd(NO₃)₃·6H₂O solution and magnetically stirred at room temperature for 12 hours to allow the gadolinium ions to fully adsorb into the pore structure of the MOF material. The solid material was then separated by centrifugation and washed multiple times with deionized water to remove unadsorbed gadolinium ions. Finally, it was dried in a vacuum oven at 60°C to constant weight, yielding a carbon-doped MoN MOF material adsorbing gadolinium ions.

[0039] The morphology of carbon-doped molybdenum-based MOF porous MRI probe was characterized by scanning electron microscopy (SEM). Figure 1 As shown. Figure 1 The carbon-doped MoN exhibits an octahedral structure with numerous nanopores on its surface. Under 980 nm laser irradiation, the antibacterial activity against Escherichia coli was 99.3% and against Staphylococcus aureus was 98.3%. Example 2

[0040] A carbon-doped molybdenum-based MOF-derived porous MRI probe and its anti-infection application, comprising the following steps: Step 1: Dissolve copper nitrate, aspartic acid, and phosphomolybdic acid hydrate in deionized water at a ratio of 15 mmol: 10 mmol: 24 mmol. Stir at room temperature for 1 hour. Then, inject 1.0 mmol / L 1,3,5-benzenetricarboxylic acid ethanol solution into the solution for complexation and coordination. Stir the reaction at room temperature to obtain NENU-5 octahedron. Step 2: NENU-5 precursor (0.1 g) was placed in a tube furnace. Under Ar protection, the furnace temperature was raised to 900°C at a rate of 2°C / min and maintained at this temperature for 3 hours. NH3 was then introduced into the furnace and the temperature was maintained for another 4 hours in the NH3 flow to promote the nitridation reaction, thereby forming a carbon-doped MoN MOF structure.

[0041] Step 3: 0.05 g of dried MoN MOF material was placed in a 0.1 mol / L Gd(NO₃)₃·6H₂O solution and magnetically stirred at room temperature for 12 hours to allow the gadolinium ions to fully adsorb into the pore structure of the MOF material. The solid material was then separated by centrifugation and washed multiple times with deionized water to remove unadsorbed gadolinium ions. Finally, the solid material was dried in a vacuum oven at 60°C to constant weight, yielding a carbon-doped MoN MOF material adsorbing gadolinium ions.

[0042] UV-Vis-NIR full spectrum ( Figure 2) showed that the carbon-doped molybdenum-based MOF porous MRI probe exhibited significant absorption properties in the near-infrared region. Under irradiation with a 980 nm laser, its antibacterial efficiency against Escherichia coli was 97.3% and against Staphylococcus aureus was 97.9%. Example 3

[0043] A carbon-doped molybdenum-based MOF-derived porous MRI probe and its anti-infection application, comprising the following steps: Step 1: Dissolve copper chloride, aspartic acid, and phosphomolybdic acid hydrate in deionized water at a ratio of 10 mmol: 5 mmol: 24 mmol, and stir at room temperature for 1 hour. Then, inject 0.8 mmol / L 1,3,5-benzenetricarboxylic acid ethanol solution into the solution for complexation and coordination. Stir the reaction at room temperature to obtain NENU-5 octahedron. Step 2: NENU-5 precursor (0.1 g) was placed in a tube furnace. Under Ar protection, the furnace temperature was raised to 850°C at a rate of 2°C / min and maintained at this temperature for 2 hours. Subsequently, NH3 was introduced into the furnace and the temperature was maintained for another 3 hours in the NH3 flow to promote the nitridation reaction, thereby forming a carbon-doped MoN MOF structure.

[0044] Step 3: 0.05 g of dried MoN MOF material was placed in a 0.1 mol / L Gd(NO₃)₃·6H₂O solution and magnetically stirred at room temperature for 12 hours to allow the gadolinium ions to fully adsorb into the pore structure of the MOF material. The solid material was then separated by centrifugation and washed multiple times with deionized water to remove unadsorbed gadolinium ions. Finally, the solid material was dried in a vacuum oven at 60°C to constant weight, yielding a carbon-doped MoN MOF material adsorbing gadolinium ions.

[0045] Photothermal experiment ( Figure 3 ) demonstrated that the photothermal performance of a carbon-doped molybdenum-based porous MOF MRI probe increased with prolonged 980 nm laser irradiation. Under 980 nm laser irradiation, the probe demonstrated an antibacterial efficiency of 98.4% against Escherichia coli and 98.9% against Staphylococcus aureus. Example 4

[0046] A carbon-doped molybdenum-based MOF-derived porous MRI probe and its anti-infection application, comprising the following steps: Step 1: Dissolve copper acetate, aspartic acid, and phosphomolybdic acid hydrate in deionized water at a ratio of 12 mmol: 7 mmol: 20 mmol. Stir at room temperature for 1 hour. Then, inject 0.6 mmol / L 1,3,5-benzenetricarboxylic acid ethanol solution into the solution for complexation and coordination. Stir the reaction at room temperature to obtain NENU-5 octahedron. Step 2: NENU-5 precursor (0.1 g) was placed in a tube furnace. Under Ar protection, the furnace temperature was raised to 850°C at a rate of 2°C / min and maintained at this temperature for 2 hours. Subsequently, NH3 was introduced into the furnace and the temperature was maintained for another 3 hours in the NH3 flow to promote the nitridation reaction, thereby forming a carbon-doped MoN MOF structure.

[0047] Step 3: 0.05 g of dried MoN MOF material was placed in a 0.08 mol / L Gd(NO₃)₃·6H₂O solution and magnetically stirred at room temperature for 12 hours to allow the gadolinium ions to fully adsorb into the pore structure of the MOF material. The solid material was then separated by centrifugation and washed multiple times with deionized water to remove unadsorbed gadolinium ions. Finally, the solid material was dried in a vacuum oven at 60°C to constant weight, yielding a carbon-doped MoN MOF material adsorbing gadolinium ions.

[0048] Magnetic resonance imaging and antibacterial effect testing of carbon-doped molybdenum-based MOF nanoprobes ( Figure 4 and Figure 5 ).like Figure 4 As shown in the figure, in vitro magnetic resonance imaging showed that the carbon-doped MoN MRI nanoprobe had good imaging capabilities. Under 980 nm laser irradiation, its antibacterial rate against Escherichia coli was 99.3% and its antibacterial rate against Staphylococcus aureus was 99.5% ( Figure 5 ).

[0049] The antibacterial rate results of Examples 1-4 are shown in Table 1.

[0050] Table 1 Antibacterial efficiency of Examples 1-4 Test items Example 1 Example 2 Example 3 Example 4 Escherichia coli 99.3% 97.3 % 98.4 % 99.3 % Staphylococcus aureus 98.3% 97.9 % 98.9 % 99.5% In summary, the present invention discloses a carbon-doped molybdenum-based metal-organic framework (MOF)-derived porous MRI probe and its anti-infective application. A copper source, amino acid, and phosphomolybdic acid hydrate are mixed and stirred in deionized water, and an organic ligand solution in ethanol is added for complexation reaction to produce a NENU-5 octahedral precursor. The precursor is then treated at 800-900°C under an inert atmosphere and further reacted in NH₃ to form a carbon-doped MoN MOF structure. The dried MoN MOF material is then stirred in a Gd(NO₃)₃·6H₂O solution to allow gadolinium ions to adsorb into the material's pores, resulting in a carbon-doped MoN MOF nanoprobe. This invention optimizes the electronic structure of the molybdenum-based MOF material through a precisely controlled carbon doping process. Carbon doping not only improves the material's conductivity but also enhances its thermal stability during high-temperature treatment, thereby ensuring structural integrity and functional consistency in subsequent synthesis steps. During the synthesis process, the NENU-5 precursor used forms a highly ordered octahedral structure through complexation and coordination reactions. This structure provides an ideal matrix for subsequent carbon doping and gadolinium ion loading. This porous structure not only increases the material's specific surface area but also enhances the adsorption efficiency of Gd³⁺, resulting in more uniform gadolinium ion loading and significantly improving MRI imaging. Furthermore, the introduction of molybdenum and carbon doping into the MOF material significantly increases the material's photothermal conversion efficiency, enabling photothermal therapy. This integrated functionality enables the nanoprobe to achieve precise diagnosis and photothermal therapy at the site of infection. This nanoprobe has promising clinical application prospects.

[0051] It can be seen that by introducing carbon elements into the framework structure of MOF, its conductivity and chemical stability can be significantly improved. The carbon doping of the present invention not only enhances the electronic conductivity of the molybdenum-based MOF material, thereby increasing the intensity of the MRI signal, but also improves the dispersibility and biocompatibility of the material in the biological environment, ensuring that the probe can be stably present in the body for a long time. At the same time, the carbon doping in the present invention also gives the molybdenum-based MOF material better thermal stability and photothermal effect, providing a new opportunity for integrated photothermal diagnosis and treatment of infection.

[0052] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF, characterized in that: The following steps are involved: 1) The copper-molybdenum-based precursor is first sintered at high temperature under an inert atmosphere, and then NH3 is introduced and kept warm to promote the nitridation reaction to obtain a carbon-doped MoN MOF material; 2) The carbon-doped MoN MOF material was immersed in a gadolinium salt solution, stirred thoroughly at room temperature, and centrifuged to separate the solid material. The solid material was then washed and dried to obtain a carbon-doped MoN MOF material that adsorbed gadolinium ions, namely a carbon-doped molybdenum-based MOF-derived porous MRI probe.

2. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to claim 1, wherein: In step 1), the high-temperature sintering treatment is carried out in an argon atmosphere, starting from room temperature and heating to 800-900° C. at a heating rate of 2° C. / min, and then maintaining the temperature for 1-3 hours.

3. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to claim 1, characterized in that: In step 1), after the introduction of NH3, the temperature is kept at room temperature for 2-4 hours to promote the nitriding reaction.

4. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to claim 1, wherein: In step 2), the gadolinium salt solution is a Gd(NO3)3·6H2O solution with a concentration of 0.01-0.1 M.

5. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to any one of claims 1 to 4, characterized in that: The copper-molybdenum-based precursor has an octahedral structure and is prepared according to the following method: The copper source, amino acid and phosphomolybdic acid hydrate were dissolved in deionized water, stirred at room temperature for 1 h, and then an ethanol solution of an organic ligand was injected therein for complexation and coordination, and the reaction was stirred at room temperature to obtain the product.

6. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to claim 5, characterized in that: The molar ratio of the copper source, amino acid and phosphomolybdic acid is (10-15): (5-10): (16-24).

7. The method for preparing a porous MRI probe derived from a carbon-doped molybdenum-based MOF according to claim 5, wherein: The copper source is copper acetate, copper nitrate or copper chloride; the amino acid is L-glutamic acid or aspartic acid; and the ethanol solution of the organic ligand is 1,3,5-benzenetricarboxylic acid ethanol solution with a concentration of 0.5-1.0 mmol / L.

8. A carbon-doped molybdenum-based MOF-derived porous MRI probe prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The porous MRI probe has an octahedral structure, and Gd³⁺ is uniformly loaded in the nanopores.

9. Use of the carbon-doped molybdenum-based MOF-derived porous MRI probe according to claim 8 in the preparation of an MRI contrast agent.

10. The use according to claim 9, characterized in that The MRI contrast agent can enhance the MRI signal intensity of the infected area.

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