Preparation method and application of Gd / Ho bimetallic doped carbon dots

Abstract

The present invention discloses a preparation method and application of Gd / Ho bimetallic doped carbon dots, relating to the field of nanomaterial technology. The method comprises the following steps: 1. Ultrasonication of urea, gallic acid, a Ho-containing compound, and a Gd-containing compound in deionized water to obtain a mixed emulsion; 2. Adding the mixed emulsion obtained in step 1 to a microwave oven for sealed, high-temperature reaction to obtain a reaction solution; and 3. Treating the reaction solution obtained in step 2 with deionized water, centrifuging it, and dialyzing the supernatant in water to obtain a dialysate. The dialysate is freeze-dried to obtain Ho / Gd-doped carbon dots. The carbon dots synthesized by doping Gd and Ho in the present invention simultaneously possess triple-modal imaging capabilities: fluorescence, magnetic resonance imaging, and computed tomography. All three imaging modalities exhibit excellent imaging capabilities, making them advantageous for practical applications in biological imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and more particularly to a preparation method and application of Gd / Ho bimetallic doped carbon dots. Background Art

[0002] Cancer (malignant tumors) is one of the major threats to human health. With the rapid development of science and technology, new tumor diagnosis and treatment methods continue to emerge. Emerging treatment methods such as photothermal therapy (PTT) are constantly being studied in depth and gradually entering clinical trials, providing a broader space and richer ideas for the development of the field of tumor treatment. In addition, diagnostic and treatment technologies that combine tumor diagnosis and treatment have received widespread attention in tumor treatment. They can achieve real-time monitoring of treatment effects and then adjust the dosage or treatment plan in time, thereby achieving individualized drug administration for patients and improving treatment effects. Nanomedicines have attracted widespread attention in the field of tumor treatment due to their multifunctionality and multi-therapy combination advantages, while medical imaging technology can achieve tumor screening, monitoring and treatment response due to its real-time and non-invasive advantages. Therefore, new nano-integrated diagnostic and treatment probes are developed for imaging-guided combined cancer treatment.

[0003] Medical imaging technologies play an indispensable role in the diagnosis, treatment, and prognosis of cancer. Magnetic resonance imaging (MRI) has garnered widespread attention due to its advantages, including high temporal and spatial resolution, unlimited penetration depth, and lack of radiation exposure. T1, referred to as longitudinal relaxation time, is used for T1-weighted imaging, primarily for observing adipose tissue or anatomical structures. T2, referred to as transverse relaxation time, is used for T2-weighted imaging to identify pathological tissue. Magnetic resonance imaging contrast agents can further enhance the MRI signal by reducing the T1 or T2 of water protons. Simultaneously acquiring T1- and T2-weighted images during a single MRI scan can better visualize local lesions and structural information of the observed area, allowing for cross-validation and more accurate diagnostic results. Specifically, T1-T2 dual-modality MRI can be used for precise imaging of early-stage tumors, the vascular system, the central nervous system, and other areas, avoiding the impact of single-modality MRI artifacts on diagnostic results. Therefore, developing a multifunctional nano-theranostic agent with ultra-high-field T1-T2 dual-modality imaging capabilities is of great significance for imaging visualization in cancer therapy.

[0004] Carbon quantum dots (CQDs) have been selected as the ideal framework for constructing nanoprobes due to their excellent optical properties, superior biocompatibility, and ease of doping and surface modification. CQDs are further doped to give nanoprobes a variety of medical imaging functions.

[0005] Therefore, it is necessary to propose a preparation method of Gd / Ho bimetallic doped carbon dots and its application to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of the influence of MRI artifacts on diagnostic results under single modality.

[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0008] A method for preparing Gd / Ho bimetallic doped carbon dots comprises the following steps:

[0009] Step 1: Ultrasonication of urea, gallic acid, a Ho-containing compound, and a Gd-containing compound in deionized water to obtain a mixed emulsion;

[0010] Step 2: adding the mixed emulsion obtained in step 1 into a microwave oven, and reacting at high temperature to obtain a reaction solution;

[0011] Step 3: The reaction solution obtained in step 2 is treated with deionized water, and after centrifugation, the supernatant is dialyzed in water to obtain a dialysate, and the dialysate is freeze-dried to obtain Ho / Gd-doped carbon dots.

[0012] Furthermore, in step 1, the doping ratio of urea to gallic acid is in the range of 20:5-10.

[0013] Furthermore, in step 1, the ratio of urea to the Gd-containing compound is 20:1.

[0014] Furthermore, in step 1, the ratio of urea to the Ho-containing compound is in the range of 20:1-2.

[0015] Furthermore, the volume of the deionized water in step 1 is 10 to 30 ml.

[0016] Furthermore, the microwave time in step 2 is 5 to 10 minutes.

[0017] Furthermore, the Gd-containing compound includes but is not limited to GdCl3·6H2O and Gd(NO3)3; the Ho-containing compound includes but is not limited to HoCl3·6H2O.

[0018] Furthermore, in step 2, the high temperature reaction temperature is 140-200° C., and the reaction time is 6-12 hours.

[0019] Furthermore, the reaction solution of step 2 was mixed evenly with deionized water, centrifuged at 8000 rpm for 5-10 minutes, and the supernatant was added to a dialysis bag and dialyzed in pure water for 2-3 days. The dialyzate obtained after dialysis was freeze-dried to obtain Gd / Ho-doped carbon dots.

[0020] An application of Gd / Ho bimetallic doped carbon dots, including Gd / Ho bimetallic doped carbon dots prepared by the above-mentioned preparation method of Gd / Ho bimetallic doped carbon dots, wherein the Gd / Ho bimetallic doped carbon dots are used to prepare biomimetic nanodiagnostic and therapeutic preparations for performing magnetic resonance T1 / T2 dual-mode imaging of tumor sites.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention, by doping Gd and Ho to synthesize carbon dots, enables the carbon dots to simultaneously possess the functions of fluorescence / magnetic resonance / computer tomography triple-modality imaging, and enables all three imaging modalities to have excellent imaging capabilities, making it beneficial for the practical application of biological imaging.

[0023] 2. Through the aforementioned improvements, the present invention enhances the optical properties of carbon quantum dots, shifting their emission peak to the green region and improving their fluorescence imaging capabilities. Furthermore, the incorporation of Gd and Ho gives the carbon dots superior MRI / CT imaging capabilities. Furthermore, because the selected compounds are commonly used clinical contrast agents or their precursors, and these compounds are chelated into the carbon quantum dots, the biotoxicity of the contrast agent is extremely low. Furthermore, the present invention utilizes a simple, one-step microwave method to synthesize the carbon dots, making it easy to operate and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagrams of the fluorescence effects of three embodiments of the present invention;

[0025] Figure 2 The T1 effect diagrams and mapping diagrams of MRI of three embodiments of the present invention are shown in order from top to bottom: embodiment 1, embodiment 2, and embodiment 3;

[0026] Figure 3 The T2 effect diagrams and mapping diagrams of MRI of three embodiments of the present invention are shown in the figure, from top to bottom, respectively: embodiment 1, embodiment 2, and embodiment 3;

[0027] Figure 4 These are CT renderings of three embodiments of the present invention, from top to bottom, they are embodiment 1, embodiment 2, and embodiment 3. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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 are within the scope of protection of the present invention.

[0029] See also Figure 1-4 , a preparation method of Gd / Ho bimetallic doped carbon dots, comprising the following steps.

[0030] Step 1: 1.0 g urea, 0.5 g gallic acid, 0.025 g HoCl3·6H2O, and 0.05 g GdCl3·6H2O were weighed and dissolved in 10 mL deionized water (H2O), and ultrasonically dispersed for 5 minutes to obtain a white mixed emulsion;

[0031] Urea in the raw material is rich in amino groups, which act as a passivating agent during the reaction. Its functions are: 1. Surface passivation can increase the fluorescence quantum yield of carbon quantum dots; 2. The presence of amino groups helps to improve the water solubility of carbon quantum dots;

[0032] Step 2: adding the white mixed emulsion obtained in step 1 into a microwave oven, heating and reacting at 180° C. for 5 minutes to obtain a reaction solution;

[0033] The one-step microwave synthesis method first chelates Gd and Ho into the carbon dot structure through a simple method, giving the carbon dots the imaging function of magnetic resonance / CT. Among them, Gd can interact with water protons in the external environment, thereby increasing the longitudinal relaxation rate (R1) of water protons. Its chelate is often used to enhance magnetic resonance longitudinal (T1) angiography; Ho, as a rare earth metal, has a high magnetic moment and non-zero electron spin. These properties make Ho have strong magnetism, which can enhance the local magnetic field, thereby enhancing the transverse relaxation rate (R2) of protons, thereby improving image contrast. And because of its high atomic coefficient, Ho can absorb X-rays, thereby enhancing CT angiography, and its compounds are often used as CT contrast agents in clinical practice. Selecting compounds of these two elements as raw materials can give carbon dots a better magnetic resonance / CT imaging enhancement effect and ensure its biocompatibility.

[0034] During the high-temperature preparation of carbon dots using urea, urea provides them with abundant functional groups that can absorb light energy and emit light, forming specific fluorescence properties. This improves their ability to perform deep tissue fluorescence imaging, making them more suitable for in vivo biological imaging.

[0035] Step 3: Take out the reaction solution obtained in step 2, add 10 mL of deionized water, and shake to mix evenly to obtain a dark brown solution; the dark brown solution is centrifuged at 8000 rpm for 10 minutes, the supernatant is taken, added to a dialysis bag (molecular cutoff of 1000), and dialyzed in pure water for 2 days. The solution obtained after dialysis is freeze-dried to obtain the product Ho / Gd@CDs, which is stored in a desiccator.

[0036] Example 2

[0037] Step 1: Weigh 1.0 g of urea, 0.25 g of gallic acid, 0.05 g of HoCl3·6H2O, and 0.05 g of GdCl3·6H2O, respectively, dissolve them in 10 mL of deionized water (H2O), and ultrasonically disperse them for 5 minutes to obtain a white mixed emulsion;

[0038] Step 2: adding the white mixed emulsion obtained in step 1 into a microwave oven, heating and reacting at 180° C. for 5 minutes to obtain a reaction solution;

[0039] Step 3: Remove the above reaction solution, add 10 mL of deionized water, and shake to mix evenly to obtain a dark brown solution; the dark brown solution is centrifuged at 8000 rpm for 10 minutes, and the supernatant is taken and added to a dialysis bag (molecular cutoff of 1000), and dialyzed in pure water for 2 days. The solution obtained after dialysis is freeze-dried to obtain the product Ho / Gd@CDs, which is stored in a desiccator.

[0040] Example 3

[0041] Step 1: Weigh 1.0 g of urea, 0.5 g of gallic acid, 0.1 g of HoCl3·6H2O, and 0.05 g of GdCl3·6H2O, respectively, dissolve them in 10 mL of deionized water (H2O), and ultrasonically disperse them for 5 minutes to obtain a white mixed emulsion;

[0042] Step 2: adding the white mixed emulsion obtained in step 1 into a microwave oven, heating and reacting at 180° C. for 5 minutes to obtain a reaction solution;

[0043] Step 3: Remove the above reaction solution, add 10 mL of deionized water, and shake to mix evenly to obtain a dark brown solution; the above dark brown solution is centrifuged at 8000 rpm for 10 minutes, and the supernatant is taken and added to a dialysis bag (molecular cutoff of 1000), and dialyzed in pure water for 2 days. The solution obtained after dialysis is freeze-dried to obtain the product Ho / Gd@CDs, which is stored in a desiccator.

[0044] During the heating reaction, the raw materials dehydrate and carbonize to form carbon dots. Gd and Ho are chelated within the carbon quantum dot structure, respectively, endowing the contrast agent with enhanced fluorescence, magnetic resonance, and computed tomography imaging capabilities. The carbonization and condensation of urea at high temperatures form carbon-rich nanoparticles. These particles self-assemble into fluorescent carbon dots during their formation. This provides the contrast agent with superior fluorescence, magnetic resonance, and CT imaging capabilities, enhancing its potential for application in bioimaging.

[0045] According to the experimental results, Figure 1 The fluorescence effects of the three examples are shown. It can be seen that the fluorescence effect of Case 2 is stronger.

[0046] Figure 2The T1 effect diagram and mapping diagram of MRI of the three embodiments show that all of them have good T1 imaging capabilities;

[0047] Figure 3 The T2 effect diagram and mapping diagram of MRI of the three embodiments are shown. It can be seen that the T2 imaging capability of embodiment 3 is stronger;

[0048] Figure 4 From the CT renderings of the three embodiments, it can be seen that all of them have good CT imaging capabilities.

[0049] From the above results, it can be seen that the MRI and CT imaging effects of Examples 2 and 3 are both good, but since the fluorescence effect of Example 2 is the best, Example 2 is the best choice.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. The scope of patent protection of the present invention shall be based on the claims. Any equivalent structural changes made using the description and drawings of the present invention should also be included in the scope of protection of the present invention.

Claims

1. A method for preparing Gd / Ho bimetallic doped carbon dots, characterized in that: The following steps are involved: Step 1: Ultrasonication of urea, gallic acid, a Ho-containing compound, and a Gd-containing compound in deionized water to obtain a mixed emulsion; Step 2: adding the mixed emulsion obtained in step 1 into a microwave oven, and conducting a sealed high-temperature reaction at a temperature of 140-200° C. to obtain a reaction solution; Step 3: The reaction solution obtained in step 2 is treated with deionized water, and after centrifugation, the supernatant is dialyzed in water to obtain a dialysate, and the dialysate is freeze-dried to obtain Ho / Gd-doped carbon dots.

2. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: The doping ratio of urea to gallic acid in step 1 is in the range of 20:5-10.

3. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: In step 1, the ratio of urea to the Gd-containing compound is 20:

1.

4. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: In step 1, the ratio of urea to the Ho-containing compound is in the range of 20:1-2.

5. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: The volume of the deionized water in step 1 is 10 to 30 ml.

6. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: The microwave time in step 2 is 5 to 10 minutes.

7. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: The Gd-containing compounds include but are not limited to GdCl3·6H2O and Gd(NO3)3; the Ho-containing compounds include but are not limited to HoCl3·6H2O.

8. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: In step 2, the high temperature reaction time is 6 to 12 hours.

9. The method for preparing Gd / Ho bimetallic doped carbon dots according to claim 1, wherein: The reaction solution of step 2 was mixed evenly with deionized water, centrifuged at 8000 rpm for 5-10 minutes, and the supernatant was added to a dialysis bag and dialyzed in pure water for 2-3 days. The dialyzate obtained after dialysis was freeze-dried to obtain Gd / Ho doped carbon dots.

10. An application of Gd / Ho bimetallic doped carbon dots, comprising the Gd / Ho bimetallic doped carbon dots prepared by the method for preparing Gd / Ho bimetallic doped carbon dots according to any one of claims 1 to 9, characterized in that: The Gd / Ho bimetallic doped carbon dots are used to prepare bionic nano-diagnostic and therapeutic preparations, and perform magnetic resonance T1 / T2 dual-mode imaging of tumor sites.

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