GRAPHENE QUANTUM DOTS-GADOLINIUM ION CHELATE AS MAGNETIC RESONANCE IMAGING CONTRAST AGENT AND PREPARATION METHOD THEREOF

Abstract

A graphene quantum dots-gadolinium ion chelate (Gd@GQDs) nanomaterial with hydrophilic groups on the surface has a preparation method that includes: preparing graphene oxide by using a Hummers method; subsequently, subjecting the graphene oxide to heating, oxidation, and purification to obtain pure graphene quantum dots; and finally, chelating the graphene quantum dots with Gd.sup.3+ to form stable Gd@GQDs. The Gd@GQDs is easily dispersed in water, phosphate buffered solution (PBS), biological medium and other aqueous system, has good biocompatibility and low cytotoxicity, shows an excellent T.sub.1-weighted contrast performance in a 1.5-Tesla magnetic resonance testing system, and has a relaxation rate r.sub.1 as high as 72 mM.sup.−1s.sup.−1, the value of r.sub.1 being 20 times higher than that of the current commercial T.sub.1-weighted magnetic resonance imaging contrast agent Gd-DTPA.

Claims

1. A graphene quantum dots-gadolinium ion chelate, wherein the graphene quantum dots-gadolinium ion chelate is a nanomaterial with a dendrite-like morphology formed by a coordination and self-assembly of graphene quantum dots and gadolinium ions, and a surface of the graphene quantum dots-gadolinium ion chelate has hydrophilic groups comprising hydroxyl groups, carboxyl groups, and amino groups.

2. A method for preparing the graphene quantum dots-gadolinium ion chelate according to claim 1, comprising: preparing graphene oxide by using a Hummers method; subjecting the graphene oxide to a heating and oxidation to obtain the graphene quantum dots; and chelating the graphene quantum dots with Gd.sup.3+ to form the graphene quantum dots-gadolinium ion chelate, wherein the graphene quantum dots-gadolinium ion chelate is stable.

3. The method according to claim 2, further comprising the following steps: 1) preparing the graphene oxide by using the Hummers method; 2) weighing and dissolving the graphene oxide in deionized water to obtain a first solution, performing an ultrasonic treatment on the first solution, and then adding a predetermined amount of a strong oxidant for being fully dissolved to obtain a second solution; 3) adding 400-1,000 μL of a basic compound to the second solution to obtain a resulting solution, and then refluxing the resulting solution for 7-12 h at 70-120° C.; 4) after the resulting solution is refluxed, performing a purification and a drying on the resulting solution to obtain the graphene quantum dots; 5) preparing the graphene quantum dots into a third solution with a predetermined concentration, wherein the graphene quantum dots are pure, and then adding a predetermined amount of a gadolinium chloride solution to perform a chelation reaction under predetermined conditions to obtain a solution after the chelation reaction; and 6) performing a purification and a drying on the solution after the chelation reaction to obtain the graphene quantum dots-gadolinium ion chelate.

4. The method according to claim 3, wherein an ultrasonic power in step 2) is 500-800 W.

5. The method according to claim 3, wherein the strong oxidant in step 2) is a mixture of at least one of potassium persulfate, hydrogen peroxide, concentrated sulfuric acid, concentrated nitric acid, and hypochloric acid.

6. The method according to claim 3, wherein in step 2), a mass ratio of the graphene oxide to the strong oxidant is (1-3): (1,000-3,000); and a mass ratio of the graphene oxide to the deionized water is (1-3): (1,000-3,000).

7. The method according to claim 3, wherein the basic compound in step 3) is a mixture of at least one of potassium hydroxide, sodium hydroxide, ammonia, hydrazine hydrate, ethylenediamine, and hydroxylamine.

8. The method according to claim 3, wherein each of the purification in step 4) and the purification in step 6) is at least one selected from the group consisting of suction filtration, chromatography, dialysis, filtration, extraction, distillation,. and fractionation; each of the drying in step 4) and the drying in step 6) at least one selected from the group consisting of vacuum drying, freeze drying, and high temperature drying.

9. The method according to claim 3, wherein in step 5), the predetermined concentration of the third solution prepared by the graphene quantum dots is 0.05-0.4 mg.Math.mL.sup.−1; and a concentration of the gadolinium chloride solution is 0.1-0.5 mmol.Math.L.sup.−1.

10. The method gadolinium ion chelate according to claim 3, wherein the chelation reaction in step 5) is performed by one selected from the group consisting of water bath heating, hydrothermal reaction, solution dialysis, and room temperature treatment.

11. A method of preparing a medical imaging contrast agent, comprising: using the graphene quantum dots-gadolinium ion chelate according to claim 1 or a graphene quantum dots-gadolinium ion chelate prepared by the method according to claim 2.

12. The method according to claim 11, wherein the medical imaging contrast agent comprises a magnetic resonance imaging contrast agent and a fluorescent imaging agent.

13. The method according to claim 11, wherein 1) preparing the graphene oxide by using the Hummers method; 2) weighing and dissolving the graphene oxide in deionized water to obtain a first solution, performing an ultrasonic treatment on the first solution, and then adding a predetermined amount of a strong oxidant for being fully dissolved to obtain a second solution; 3) adding 400-1,000 μL of a basic compound to the second solution to obtain a resulting solution, and then refluxing the resulting solution for 7-12 h at 70-120° C.; 4) after the resulting solution is refluxed, performing a purification and a drying on the resulting solution to obtain the graphene quantum dots; 5) preparing the graphene quantum dots into a third solution with a predetermined concentration, wherein the graphene quantum dots are pure, and then adding a predetermined amount of a gadolinium chloride solution to perform a chelation reaction under predetermined conditions to obtain a solution after the chelation reaction; and 6) performing a purification and a drying on the solution after the chelation reaction to obtain the graphene quantum dots-gadolinium ion chelate.

14. The method according to claim 13, wherein an ultrasonic power in step 2) is 500-800 W.

15. The method according to claim 13, wherein the strong oxidant in step 2) is a mixture of at least one of potassium persulfate, hydrogen peroxide, concentrated sulfuric acid, concentrated nitric acid, and hypochloric acid.

16. The method according to claim 13, wherein in step 2), a mass ratio of the graphene oxide to the strong oxidant is (1-3): (1,000-3,000); and a mass ratio of the graphene oxide to the deionized water is (1-3): (1,000-3,000).

17. The method according to claim 13, wherein the basic compound in step 3) is a mixture of at least one of potassium hydroxide, sodium hydroxide, ammonia, hydrazine hydrate, ethylenediamine, and hydroxylamine.

18. The method according to claim 13, wherein each of the purification in step 4) and the purification in step 6) is at least one selected from the group consisting of suction filtration, chromatography, dialysis, filtration, extraction, distillation, and fractionation; each of the drying in step 4) and the drying in step 6) is at least one selected from the group consisting of vacuum drying, freeze drying, and high temperature drying.

19. The method according to claim 13, wherein in step 5), the predetermined concentration of the third solution prepared by the graphene quantum dots is 0.05-0.4 mg.Math.mL.sup.−1; and a concentration of the gadolinium chloride solution is 0.1-0.5 mmol.Math.L.sup.−1.

20. The method according to claim 13, wherein the chelation reaction in step 5) is performed by one selected from the group consisting of water bath heating, hydrothermal reaction, solution dialysis, and room temperature treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a transmission electron microscopy (TEM) image of Gd@GQDs prepared by the present invention;

[0034] FIG. 2 is a Fourier transform infrared (FT-IR) spectrum of Gd@GQDs prepared by the present invention;

[0035] FIG. 3 is a diagram showing cytotoxicity test results by using MTT assay of Gd@GQDs (different concentrations of Gd@GQDs co-incubated with CHO cells and MCF-7 cells for 24 h, respectively) prepared by the present invention;

[0036] FIG. 4 is a diagram showing relaxation rates r.sub.1 and r.sub.2 of an aqueous solution of Gd@GQDs prepared by the present invention in a 1.5-Tesla magnetic resonance imaging system (R.sup.2 in the figure is a fitting correlation coefficient); and

[0037] FIGS. 5A-5D are diagrams showing T.sub.1-weighted magnetic resonance images of Gd@GQDs prepared by the present invention, GQDs, gadolinium chloride and Gd-DTPA after co-incubated with MCF-7 cells, measured with the 1.5-Tesla magnetic resonance imaging system, wherein FIG. 5A is a diagram showing a T.sub.1-weighted magnetic resonance image of GQDs, FIG. 5B is a diagram showing a T.sub.1-weighted magnetic resonance image of gadolinium chloride, FIG. 5C is a diagram showing a T.sub.1-weighted magnetic resonance image of Gd-DTPA, and FIG. 5D is a diagram showing a T.sub.1-weighted magnetic resonance image of Gd@GQDs.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following embodiments are further descriptions of the contents of the present invention as explanations of the technical contents of the present invention, but the essential content of the present invention is not limited to those described in the embodiments below. Those of ordinary skill in the art can and should be aware that any simple changes or substitutions based on the essential spirit of the present invention should fall within the protective scope claimed by the present invention.

Embodiment 1

[0039] A preparation method of a graphene quantum dots-gadolinium ion chelate, specifically including the steps as follows.

[0040] 1) Graphene oxide is prepared by using a Hummers method (this method is cited from the literature: ACS Nano, 2010, 4(8), 4806-4814.).

[0041] 2) 20 mg of the above graphene oxide is weighed, dissolved in 60 g of deionized water, treated with an ultrasonic power of 500 W, and then 60 g of hydrogen peroxide is added and then fully dissolved to obtain a solution.

[0042] 3) 1,000 μL of a hydrazine hydrate solution is added to the above solution, and then the resulting solution is transferred to a round bottom flask, and refluxed in an oil bath at 100° C. for 8 h.

[0043] 4) After the reflux reaction, the resulting solution is filtered and purified to remove bulk impurities, and then dried at a temperature of 80° C. to obtain GQDs, and the GQDs have the characteristics of two-dimensional regular morphology, a uniform size, a lateral dimension ranging from 3 nm to 6 nm, a thickness ranging from 1 nm to 2 nm, and excitation-independent fluorescence.

[0044] 5) The GQDs prepared above are formulated into a solution with a concentration of 0.35 mg.Math.mL.sup.−1, and then gadolinium chloride is added, a concentration of the gadolinium chloride solution is controlled to 0.45 mmol.Math.L.sup.−1, and a chelation reaction is carried out in a hydrothermal autoclave at 120° C. to obtain a solution after the reaction.

[0045] 6) The above-mentioned solution after the reaction is subjected to rotary evaporation and a lyophilization treatment to obtain Gd@GQDs.

[0046] The performance of Gd@GQDs prepared in Embodiment 1 is tested.

[0047] FIG. 1 is a TEM image of the Gd@GQDs. It can be found that after the addition of gadolinium ions, GQDs exhibit a self-assembly behavior, which has the characteristics of a large specific surface area, stable optical properties, and hydrophilic groups on the surface.

[0048] FIG. 2 is an FT-IR spectrum of the Gd@GQDs prepared by the present invention. In the figure, 3398 cm.sup.−1 is the hydroxyl (O—H) stretching vibration peak, 2948 cm.sup.−1 is the secondary amino group N—H stretching vibration peak, 1725 cm.sup.−1 is the C═O asymmetric stretching vibration peak, and 1600 cm.sup.−1 is the C═C stretching vibration peak, indicating that the Gd@GQDs prepared by the present invention has a large number of hydrophilic groups and maintains a certain graphene structure.

[0049] FIG. 3 is a diagram showing the cytotoxicity of the prepared Gd@GQDs measured by the MTT assay. The MTT assay is a common method for detecting cell viability and growth. The detection principle is that succinate dehydrogenase in the mitochondria of living cells can reduce exogenous MTT (thiazole blue) into water-insoluble blue-purple crystalline formazan that deposits in cells, while dead cells do not have such function. Then, dimethyl sulfoxide (DMSO) is used to dissolve the formazan in the cells, and then its light absorption value is measured by an enzyme-linked immunosorbent reader at a wavelength of 540 nm or 720 nm, which can indirectly reflect the number of living cells.

[0050] The cytotoxicity test results by using MTT assay showed that after co-cultivating MCF-7 cells and CHO cells (both provided by the School of Life Sciences, Anhui University) with Gd@GQDs for 24 h, the viability of the cells was still remained above 90%, indicating that the prepared Gd@GQDs has very low cytotoxicity.

[0051] FIG. 4 shows relaxation rates r.sub.1 and r.sub.2 of Gd@GQDs prepared by the present invention in a 1.5-Tesla MRI system, indicating that Gd@GQDs has an extremely high relaxation rate r.sub.1.

[0052] FIGS. 5A-5D show T.sub.1-weighted magnetic resonance images of Gd@GQDs (0.2 mg.Math.mL.sup.−1 with a Gd.sup.3+ content of 0.2 mmol.Math.L.sup.−1) prepared by the present invention, graphene quantum dots (0.2 mg.Math.mL.sup.−1), gadolinium chloride (0.2 mmol.Math.L.sup.−1) and Gd-DTPA (0.2 mmol.Math.L.sup.−1) after co-incubated with MCF-7 cells respectively and measured with the 1.5-Tesla MRI system, showing that Gd@GQDs has an excellent contrast effect in cellular MRI.

Embodiment 2

[0053] A preparation method of a graphene quantum dots-gadolinium ion chelate, specifically including the steps as follows.

[0054] 1) Graphene oxide is prepared by using a Hummers method.

[0055] 2) 60 mg of the above graphene oxide is weighed, dissolved in 60 g of deionized water, treated with an ultrasonic power of 800 W, and then 60 g of a potassium persulfate solution with a concentration of 1 mol.Math.L.sup.−1 is added and then fully dissolved to obtain a solution.

[0056] 3) 800 μL of an ammonia solution is added to the above solution, and then the resulting solution is transferred to a round bottom flask, and refluxed in an oil bath at 70° C. for 12 h.

[0057] 4) After the reflux reaction, the resulting solution is purified by chromatography to remove bulk impurities, and then freeze-dried to obtain GQDs.

[0058] 5) The GQDs prepared above are formulated into a solution with a concentration of 0.2 mg.Math.mL.sup.−1, and then gadolinium chloride is added, a concentration of the gadolinium chloride solution is controlled to 0.2 mmol.Math.L.sup.−1, and a chelation reaction is carried out at room temperature to obtain a solution after the reaction.

[0059] 6) The above-mentioned solution after the reaction is dialyzed, and then dried at a temperature of 100° C. to obtain Gd@GQDs.

Embodiment 3

[0060] A preparation method of a graphene quantum dots-gadolinium ion chelate, specifically including the steps as follows.

[0061] 1) Graphene oxide is prepared by using a Hummers method.

[0062] 2) 60 mg of the above graphene oxide is weighed, dissolved in 60 g of deionized water, treated with an ultrasonic power of 600 W, and then 20 g of a mixture of concentrated sulfuric acid and concentrated nitric acid is added and then fully dissolved to obtain a solution.

[0063] 3) 400 μL of a 1 mol.Math.L.sup.−1 sodium hydroxide solution is added to the above solution, and then the resulting solution is transferred to a round bottom flask, and refluxed in an oil bath at 80° C. for 10 h.

[0064] 4) After the reflux reaction, the resulting solution is subjected to suction filtration and a purification treatment to remove bulk impurities, and then subjected to a vacuum drying treatment to obtain GQDs.

[0065] 5) The GQDs prepared above are formulated into a solution with a concentration of 0.05 mg.Math.mL.sup.−1, and then gadolinium chloride is added, a concentration of the gadolinium chloride solution is controlled to 0.1 mmol.Math.L.sup.−1, and a chelation reaction is carried out in a water bath at 60° C. to obtain a solution after the reaction.

[0066] 6) The above-mentioned solution after the reaction is subjected to distillation and a drying treatment to obtain Gd@GQDs.

[0067] The graphene quantum dots-gadolinium ion chelate (Gd@GQDs) prepared by the present invention is used according to the same operation steps as commercial contrast agents. The Gd@GQDs can be used as an MRI contrast agent as well as a fluorescent imaging agent.

[0068] The Gd@GQDs prepared by the present invention is easily dispersed in aqueous systems such as water, PBS, and biological medium, has good biocompatibility and low cytotoxicity, shows an excellent T.sub.1-weighted contrast performance in a 1.5-Tesla magnetic resonance testing system, and has a relaxation rate r.sub.1 as high as 72 mM.sup.−1s.sup.−1, the value of r.sub.1 being 20 times higher than that of the current commercial T.sub.1-weighted MRI contrast agent Gd-DTPA. In practical applications, the injection dosage of Gd.sup.3+ in Gd@GQDs is one-fiftieth of that of the gadolinium-based T.sub.1 contrast agent in the above-mentioned literature and the general commercial gadolinium-based T.sub.1 contrast agent. In addition, although the content of Gd.sup.3+ in the Gd@GQDs material of the present invention is only one quarter to one third of that of the gadolinium-based T.sub.1 contrast agent in the above-mentioned literature, it can still achieve a good MRI effect, which avoids the hidden danger of a large number of Gd.sup.3+leakage at source. The Gd@GQDs of the present invention can be used as a medical imaging contrast agent, and has a good application prospect in clinical practice.

[0069] The foregoing descriptions are merely preferred embodiments of the present invention, which are not used to limit the present invention. Any modifications, equivalent substitutions or improvements within the spirit and principle of the present invention shall all fall within the protective scope of the present invention.