Near-infrared II region fluorescence emission nano hydrogel with neovascularization targeting property as well as preparation and application of near-infrared II region fluorescence emission nano hydrogel

Abstract

The invention discloses a near-infrared II-region fluorescence emission nano hydrogel with neovascularization targeting as well as preparation and application of the near-infrared II-region fluorescence emission nano hydrogel. The preparation method of the nano hydrogel provided by the invention comprises the following steps: (1) dissolving small organic molecules containing organic amine and small organic molecules containing boric acid groups in an acid-containing ethanol solution to obtain a carbon dot precursor solution; (2) carrying out solvothermal reaction on the carbon dot precursor solution obtained in the step (1) to obtain carbon dots; (3) adding the ethanol dispersion liquid of the carbon dots in the step (2) into a fucoidin solution, and carrying out ultrasonic treatment to obtain a crude product; and (4) carrying out centrifugation, dialysis and freeze drying treatment on the crude product obtained in the step (3) to obtain the nano hydrogel. The fucoidin with neovascularization targeting is used as a raw material, the carbon dots are used as fluorescence emission and photodynamic therapy functional bodies, and different contents of the fucoidin and the carbon dots are added, so that the near-infrared II-region fluorescence emission nano hydrogel can be prepared, and the near-infrared II-region fluorescence emission nano hydrogel can be applied to abnormal neovascularization imaging and corresponding photodynamic therapy.

Description

Technical Field

[0001] The present invention relates to the field of biotechnology, and particularly to a near-infrared II region fluorescence-emitting nanogel with neovascular targeting and its preparation and application. Background Art

[0002] Vascular dysfunction, including abnormalities in vascular structure, hemodynamics, and molecular expression related to vascular function, is closely related to the occurrence and development of various diseases. For example, diabetic retinopathy is a series of fundus diseases caused by retinal microvascular leakage and obstruction due to chronic progressive diabetes. Another example is that damage to the cerebrovascular network may lead to cell death and impaired brain function due to the loss or significant reduction of blood supply. Tumor angiogenesis and its abnormal vascular structure not only participate in tumor development by providing oxygen and nutrients, but also have a profound impact on the tumor microenvironment, contributing to increased drug resistance and invasiveness. Therefore, monitoring vascular abnormalities, especially vascular structural and hemodynamic abnormalities, is of great significance for guiding the diagnosis and treatment of related diseases. Near-infrared II region (900 - 1800 nm) fluorescence can achieve deeper tissue penetration, higher spatial resolution, and signal-to-noise ratio compared to visible light and near-infrared I region fluorescence, and has broad application prospects in the fields of tissue imaging and optical therapy. Nanogels based on carbon dots have advantages such as good biocompatibility and biodegradability, and at the same time integrate the photoluminescence properties and optical therapy functions of carbon dots, which can promote in vivo near-infrared fluorescence imaging and potential clinical practice.

[0003] For example, Chinese Patent No. CN114652843B provides a nanoparticle for targeted treatment of ocular neovascularization and its preparation method. The nanoparticle includes a target precursor molecule and an ultrasmall nanoparticle; the target precursor molecule is composed of two 4,4'-bipyridine-zinc(II) molecules and a neovascular targeting polypeptide linked by a benzene ring; the ultrasmall nanoparticle is a gold / platinum-indocyanine green nanocomposite. Thus, an imaging-guided nanodrug for treating fundus neovascularization is constructed. The synthesis process parameters of this nanodrug are complex and require strict control, and it uses gold and platinum as raw materials, resulting in high costs. Summary of the Invention

[0004] In view of this, the present invention provides a near-infrared II region fluorescence-emitting nanogel with neovascular targeting and its preparation and application.

[0005] The preparation method of the nanogel provided by the present invention includes the following steps:

[0006] (1) Dissolve an organic small molecule containing an organic amine and an organic small molecule containing a borate group in an acid-containing ethanol solution to obtain a carbon dot precursor solution;

[0007] (2) Obtain carbon dots by subjecting the carbon dot precursor solution in step (1) to a solvothermal reaction;

[0008] (3) Add the ethanol dispersion of the carbon dots in step (2) to the fucoidan solution and ultrasonicate to obtain a crude product;

[0009] (4) Subject the crude product in step (3) to centrifugation, dialysis, and freeze-drying to obtain the nano-hydrogel.

[0010] Optionally, in step (1), the organic small molecule containing an organic amine is selected from at least one of ethylenediamine, aniline, o-phenylenediamine, m-phenylenediamine, or p-phenylenediamine; the organic small molecule containing a boronic acid group is selected from at least one of benzeneboronic acid, 1,4-benzenediboronic acid, or 3-aminobenzeneboronic acid.

[0011] Optionally, in step (1), in the carbon dot precursor solution, the concentration of the organic small molecule containing an organic amine is 1 g / L to 10 g / L; the concentration of the organic small molecule containing a boronic acid group is 1 g / L to 10 g / L.

[0012] Optionally, in step (1), in the carbon dot precursor solution, the molar ratio of the organic small molecule containing an organic amine to the organic small molecule containing a boronic acid group is 1:1 - 1:5.

[0013] Optionally, in step (2), the solvothermal reaction is carried out in a hydrothermal autoclave, the reaction temperature is 140 °C to 200 °C, and the reaction time is 6 h to 24 h.

[0014] Optionally, in step (3), the mass percentage concentration of the fucoidan is 0.5% - 3%, and the amount of carbon dots added is 0.5 g / L to 3 g / L.

[0015] Optionally, in step (3), the ethanol dispersion of the carbon dots is added dropwise to the fucoidan solution.

[0016] Optionally, in step (4), the rotation speed of the centrifugation is 5000 rpm - 8000 rpm; the dialysis time is 7 days - 14 days, using deionized water as the dialysis solution, and the dialysis solution is changed once a day; the temperature of the freeze-drying is -20 to -80 °C, and the drying time is 3 - 7 days.

[0017] The nano-hydrogel prepared by the method also belongs to the protection scope of the present invention.

[0018] The application of the nano-hydrogel in neonatal blood vessel fluorescence imaging and photodynamic therapy also belongs to the protection scope of the present invention.

[0019] Beneficial effects:

[0020] The present invention uses natural polysaccharide fucoidan as a raw material to simultaneously prepare boron-containing carbon dots that can generate fluorescence in the second near-infrared region. The fucoidan is crosslinked with the boron-containing carbon dots by borate bond reaction to prepare a nano-hydrogel. Compared with the prior art, the nano-hydrogel of the present invention can enrich nano-functional carbon dots in the nano-hydrogel to achieve highly efficient photodynamic therapy guided by near-infrared fluorescence imaging in the second near-infrared region. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For purposes of illustration and not limitation, the present invention will now be described in accordance with the preferred embodiments of the present invention, particularly with reference to the accompanying drawings, in which:

[0022] Figure 1 It is a transmission electron microscope photograph of the nano-hydrogel prepared in Example 1 of the present invention.

[0023] Figure 2 It is the near-infrared fluorescence emission spectrum of the nano-hydrogel prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0025] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products without special instructions or treatment techniques, or can be prepared by known methods.

[0026] The fucoidan used in the experiment was purchased from Merck, and other chemical reagents were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0027] Example 1: Preparation of a nano-hydrogel with neovascular-targeted near-infrared fluorescence emission in the second near-infrared region

[0028] This example provides a nano-hydrogel with neovascular-targeted near-infrared fluorescence emission in the second near-infrared region, and its preparation method includes the following steps:

[0029] (1) Prepare a carbon dot precursor solution: First, prepare an acidic ethanol solution, and the concentration of hydrochloric acid in the obtained acidic ethanol solution (prepared with hydrochloric acid) is 1 mol / L; then dissolve ethylenediamine and 2-carboxyphenylboronic acid in the acidic ethanol solution to obtain a carbon dot precursor solution, where the concentration of ethylenediamine is 1 g / L, the concentration of 2-carboxyphenylboronic acid is 1 g / L, and the molar ratio of ethylenediamine to 2-carboxyphenylboronic acid is 1:1.

[0030] (2) Take 30 mL of the carbon dot precursor solution obtained in step (1), put it into a hydrothermal autoclave with a volume of 100 mL, react in the hydrothermal autoclave for 6 h at a reaction temperature of 140 °C, and obtain carbon dots as the hydrothermal product after the reaction.

[0031] (3) Dissolve 1 g of fucoidan in 99 g of sterile phosphate buffer to prepare a fucoidan solution with a mass percentage concentration of 1%. Disperse the carbon dots obtained in step (2) in ethanol, and gradually add the ethanol dispersion of the carbon dots dropwise to the fucoidan solution while stirring at a stirring speed of 1200 rpm / min. The final concentration of the carbon dots is 1 g / L to obtain a crude product.

[0032] (4) Centrifuge the crude product obtained in step (3) at a speed of 5000 rpm for 10 min, dialyze for 7 days. The dialysis bag (produced by Union Carbide Corporation, USA) has a cut-off molecular weight of 1000, and freeze-dry (Toshiba) at -20 °C for 4 days to obtain the nano-hydrogel.

[0033] Detect the nano-hydrogel prepared in this example:

[0034] 1. Photodynamic therapy performance of the nano-hydrogel

[0035] Disperse the nano-hydrogel in a cell-specific medium for human umbilical vein endothelial cells (HUVEC, purchased from ATCC) (purchased from ScienCell) at a concentration of 100 mg / mL, perform light irradiation treatment on HUVEC, the light irradiation wavelength is 808 nm, the light irradiation time is 2 min, and the light irradiation intensity is 0.2 W / cm 2 . Under light irradiation, singlet oxygen is generated during the photodynamic process of the nano-hydrogel, thereby killing HUVEC. Use this model to evaluate the killing effect of the nano-hydrogel on neonatal vascular endothelial cells. Detect the cell viability by CCK-8.

[0036] 2. Size and morphology of the nano-hydrogel

[0037] The size and morphology of the nano-hydrogel are obtained from transmission electron microscope photos (FEI Tecnai F20, Thermo Fisher Scientific). The diameter of the nano-hydrogel is 46 ± 7 nm ( Figure 1 ), and it contains a certain number of carbon dots.

[0038] 3. Fluorescent properties of the nano-hydrogel

[0039] The fluorescent properties of the carbon dots are obtained from a near-infrared fluorescence emission spectrometer (FLS1000, Edinburgh Instruments). The test light source is a laser, and the concentration is 10 mg / mL.

[0040] From the near-infrared fluorescence emission spectrum, it can be seen that the fluorescence emission intensity of the nano-hydrogel is the highest at 1260 nm under the excitation of near-infrared light at 808 nm ( Figure 2 ), and this wavelength band is located in the NIR II region (1000 - 1700 nm). This fluorescence emission originates from the carbon dots in the nano-hydrogel.

[0041] Example 2: Preparation of a nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission

[0042] The specific method and steps for preparing the nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission in this example are the same as those in Example 1, except that in step (3), the final concentration of the carbon dots is 2 g / L.

[0043] Example 3: Preparation of a nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission

[0044] The specific method and steps for preparing the nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission in this example are the same as those in Example 1, except that in step (3), the final concentration of the carbon dots is 3 g / L.

[0045] Example 4: Preparation of a nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission

[0046] The specific method and steps for preparing the nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission in this example are the same as those in Example 1, except that in step (3), the final concentration of the carbon dots is 4 g / L.

[0047] Example 5: Preparation of a nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission

[0048] The specific method and steps for preparing the nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission in this example are the same as those in Example 1, except that in step (3), the mass percentage concentration of the fucoidan solution is adjusted to 2%.

[0049] Example 6: Preparation of a nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission

[0050] The specific method and steps for preparing the nano-hydrogel with neovascular-targeted near-infrared II region fluorescence emission in this example are the same as those in Example 1, except that in step (3), the mass percentage concentration of the fucoidan solution is adjusted to 3%.

[0051] The nano-hydrogels prepared in Examples 1 - 6 were detected.

[0052] (1) The diameter of the nano-hydrogel: The detection method is the same as that in Example 1.

[0053] (2) Fluorescent emission peak position of the nano-hydrogel: The detection method is the same as that in Example 1.

[0054] (3) Survival rate of HUVEC without light irradiation (%): The detection method is the same as that in Example 1.

[0055] (4) Survival rate of HUVEC under light irradiation (%): The detection method is the same as that in Example 1.

[0056] The detection results are shown in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] The nano-hydrogel is crosslinked by borate ester bonds between the boronic acid groups on the surface of carbon dots and the adjacent hydroxyl groups in the fucoidan molecular chain, as well as physical interactions such as hydrogen bonds and van der Waals forces. As can be seen from Table 1, with the increase of the carbon dot concentration (Example 1, Example 2, Example 3 and Example 4) or the fucoidan concentration (Example 1, Example 5 and Example 6), the diameter of the nano-hydrogel shows a significant upward trend. The fluorescent emission peak position of the nano-hydrogel is determined by the carbon dots, depending on the structure and chemical composition of the carbon dots, and the concentration change has no effect on the fluorescent emission peak position. In addition, the photodynamic effect is generated by the carbon dots. With the increase of the carbon dot concentration, the photodynamic killing effect on cells is enhanced, and fucoidan does not produce significant toxicity to the survival of cells.

[0061] Example 7. Preparation of a nano-hydrogel with near-infrared II region fluorescent emission and neovascular targeting

[0062] The specific method and steps for preparing the nano-hydrogel with near-infrared II region fluorescent emission and neovascular targeting in this example are the same as those in Example 1, except that in step (2), the reaction temperature in the hydrothermal autoclave is 160 °C and the reaction time is 6 h.

[0063] Example 8. Preparation of a nano-hydrogel with near-infrared II region fluorescent emission and neovascular targeting

[0064] The specific method and steps for preparing the nano-hydrogel with near-infrared II region fluorescent emission and neovascular targeting in this example are the same as those in Example 1, except that in step (2), the reaction temperature in the hydrothermal autoclave is 180 °C and the reaction time is 6 h.

[0065] Example 9. Preparation of a nano-hydrogel with near-infrared II region fluorescent emission and neovascular targeting

[0066] The specific method and steps for preparing the near-infrared II region fluorescence-emitting nanohydrogel with neovascular targeting in this example are the same as those in Example 1, except that: in step (2), the reaction temperature in the hydrothermal autoclave is 200 °C and the reaction time is 6 h.

[0067] Example 10. Preparation of a near-infrared II region fluorescence-emitting nanohydrogel with neovascular targeting

[0068] The specific method and steps for preparing the near-infrared II region fluorescence-emitting nanohydrogel with neovascular targeting in this example are the same as those in Example 1, except that: in step (2), the reaction temperature in the hydrothermal autoclave is 200 °C and the reaction time is 12 h.

[0069] The carbon dots in the nanohydrogels prepared in Examples 7 to 10 were detected, and the detection method is as follows:

[0070] 1. Size and morphology of carbon dots

[0071] The size and morphology of the carbon dots were all obtained by a transmission electron microscope (FEI Tecnai F20, Thermo Fisher Scientific).

[0072] 2. Fluorescent properties of carbon dots

[0073] The fluorescent properties of the carbon dots were all obtained by a near-infrared fluorescence emission spectrometer (FLS1000, Edinburgh Instruments). The test light source was a laser, and the concentration was 1 mg / mL.

[0074] 3. Singlet oxygen quantum yield of carbon dots: Through chemical analysis, using 1,3-diphenylbenzofuran as a singlet oxygen detection probe and methylene blue as a reference, the singlet oxygen quantum yield was detected, and the detection results are shown in Table 2.

[0075] Table 2

[0076]

[0077] By regulating the temperature and time of the solvothermal reaction conditions, the morphology and fluorescence emission characteristics of the carbon dots can be regulated. Comparing Example 1, Example 7, and Example 8, as the reaction temperature increases and the reaction time increases (Example 9 and Example 10), the particle size of the carbon dots gradually increases, the quantum yield of the carbon dots increases, and the fluorescence emission peak position has a certain degree of red shift. The nanohydrogel realizes near-infrared II region imaging and the photodynamic process through carbon dots. Therefore, with the increase in the quantum yield of the carbon dots and the red shift of the fluorescence emission peak, the nanohydrogel will have a higher neovascular killing effect and near-infrared fluorescence imaging effect.

[0078] Example 11. Performance detection of the nanohydrogel

[0079] The specific methods and steps are the same as those in Example 1, except that: in step (4), the concentration of the nano-hydrogel is 50 μg / mL.

[0080] Example 12. Performance Detection of Nano-Hydrogel

[0081] The specific methods and steps are the same as those in Example 1, except that: in step (4), the concentration of the nano-hydrogel is 200 μg / mL.

[0082] Example 13. Performance Detection of Nano-Hydrogel

[0083] The specific methods and steps are the same as those in Example 1, except that: in step (4), the light irradiation time is 30 s.

[0084] Example 14. Performance Detection of Nano-Hydrogel

[0085] The specific methods and steps are the same as those in Example 1, except that: in step (4), the light irradiation time is 5 min.

[0086] Example 15. Performance Detection of Nano-Hydrogel

[0087] The specific methods and steps are the same as those in Example 1, except that: in step (4), the light intensity is 0.1 W / cm 2 。

[0088] Example 16. Performance Detection of Nano-Hydrogel

[0089] The specific methods and steps are the same as those in Example 1, except that: in step (4), the light intensity is 0.4 W / cm 2 。

[0090] Table 3

[0091]

[0092] Comparing Example 1 with Examples 11 - 16, regulating the concentration of the nano-hydrogel and the light parameters can produce different killing effects on HUVEC. With the increase of concentration (Examples 11, Example 1 and Example 12), the extension of light irradiation time (Examples 13, Example 1 and Example 14) or the increase of light intensity (Examples 15, Example 1 and Example 16), the survival rate of HUVEC shows a downward trend, indicating a gradually enhanced photodynamic cell killing effect.

[0093] Example 17. Preparation of Near-Infrared II Region Fluorescent Emission Nano-Hydrogel with Neo-Vascular Targeting

[0094] The specific methods and steps for preparing the near-infrared II region fluorescent emission nano-hydrogel with neo-vascular targeting in this example are the same as those in Example 1, except that: the used ethylenediamine is replaced with aniline of equimolar concentration.

[0095] Example 18: Preparation of a Near-Infrared II Region Fluorescent Emission Nanogel with Neovascular Targeting

[0096] The specific method and steps for preparing the near-infrared II region fluorescent emission nanogel with neovascular targeting in this example are the same as those in Example 1, except that: the ethylenediamine used is replaced with o-phenylenediamine with an equimolar concentration.

[0097] Example 19: Preparation of a Near-Infrared II Region Fluorescent Emission Nanogel with Neovascular Targeting

[0098] The specific method and steps for preparing the near-infrared II region fluorescent emission nanogel with neovascular targeting in this example are the same as those in Example 1, except that: the ethylenediamine used is replaced with m-phenylenediamine with an equimolar concentration.

[0099] Example 20: Preparation of a Near-Infrared II Region Fluorescent Emission Nanogel with Neovascular Targeting

[0100] The specific method and steps for preparing the near-infrared II region fluorescent emission nanogel with neovascular targeting in this example are the same as those in Example 1, except that: the ethylenediamine used is replaced with p-phenylenediamine with an equimolar concentration.

[0101] Example 21: Preparation of a Near-Infrared II Region Fluorescent Emission Nanogel with Neovascular Targeting

[0102] The specific method and steps for preparing the near-infrared II region fluorescent emission nanogel with neovascular targeting in this example are the same as those in Example 1, except that: the 2-carboxyphenylboronic acid used is replaced with 3-carboxyphenylboronic acid with an equimolar concentration.

[0103] Example 22: Preparation of a Near-Infrared II Region Fluorescent Emission Nanogel with Neovascular Targeting

[0104] The specific method and steps for preparing the near-infrared II region fluorescent emission nanogel with neovascular targeting in this example are the same as those in Example 1, except that: the 2-carboxyphenylboronic acid used is replaced with 4-carboxyphenylboronic acid with an equimolar concentration.

[0105] The nanogels prepared in Examples 17 to 22 were detected, and the detection method was the same as that in Examples 1 to 6.

[0106] The detection results are shown in Table 4.

[0107] Table 4

[0108]

[0109]

[0110] Comparing Comparative Example 1, Example 17, Example 18, Example 19, and Example 20, adding a benzene ring to the precursor molecule did not have a significant effect on the particle size of the nanohydrogel. Due to the conjugation of the benzene ring, the fluorescence emission peak exhibited a red shift. The nanohydrogel did not show significant toxicity to HUVECs under dark conditions, while it could significantly kill HUVEC cells under light irradiation. Comparing Comparative Example 1, Example 21, and Example 22, regardless of the relative position of the boronic acid group to the carboxyl group on the benzene ring, the prepared nanohydrogels could generate fluorescence in the second near-infrared region and exhibit a killing effect on HUVECs under light irradiation.

[0111] Example 23. Verification of the Photodynamic Therapy Effect on Neovascularization Based on the Targeting Property of Nanohydrogels

[0112] A choroidal neovascularization model of mice (strain: C57 / BL6j, purchased from Jiangsu Jicui Yakang Biotechnology Co., Ltd.) was established. 5 μL of the nanohydrogel prepared in Example 1 was injected into the vitreous body of the mice (the microsyringe was purchased from Hamilton). After photodynamic therapy, using sodium fluorescein as a contrast agent (Abmole), the fluorescence intensity of vascular leakage was detected by fundus fluorescence angiography (Micron IV; Phoenix).

[0113] Example 24. Verification of the Photodynamic Therapy Effect on Neovascularization Based on the Targeting Property of Nanohydrogels

[0114] The difference between this example and Example 23 is that the injected nanohydrogel was replaced with a carbon dot dispersion without fucoidan.

[0115] Table 5

[0116] Test item Example 23 Example 24 Leakage fluorescence intensity value before treatment 15000 15580 Leakage fluorescence intensity value after treatment 100 12000

[0117] Comparing Example 23 and Example 24, in the absence of fucoidan, the carbon dots did not have neovascular targeting properties, so the photodynamic process could not exert a therapeutic effect on neovascularization and could not effectively inhibit the leakage caused by neovascularization. The fluorescence angiography showed a strong fluorescence intensity.

[0118] The above specific embodiments do not limit the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a nano hydrogel, characterized in that: The steps include: (1) dissolving an organic small molecule containing an organic amine and an organic small molecule containing a boric acid group in an acid-containing ethanol solution to obtain a carbon dot precursor solution; (2) subjecting the carbon dot precursor solution of step (1) to a solvothermal reaction to obtain carbon dots; (3) adding the ethanol dispersion of the carbon dots obtained in step (2) to the fucoidan solution and performing ultrasonication to obtain a crude product; (4) The crude product of step (3) is treated by centrifugation, dialysis and freeze-drying to obtain the nano hydrogel.

2. The method for preparing the nano hydrogel according to claim 1, characterized in that: In the step (1), The organic small molecule containing organic amine is selected from at least one of ethylenediamine, aniline, o-phenylenediamine, m-phenylenediamine or p-phenylenediamine; The organic small molecule containing a boronic acid group is selected from at least one of phenylboronic acid, 1,4-phenyldiboronic acid or 3-aminophenylboronic acid.

3. The method for preparing the nano hydrogel according to claim 1 or 2, characterized in that: In the step (1), in the carbon dot precursor solution, the concentration of the organic small molecules containing organic amines is 1 g / L to 10 g / L; the concentration of the organic small molecules containing boric acid groups is 1 g / L to 10 g / L.

4. The method for preparing the nano hydrogel according to claim 1 or 2, characterized in that: In the step (1), in the carbon dot precursor solution, the molar ratio of the organic small component containing the organic amine to the organic small molecule containing the boric acid group is 1:1-1:

5.

5. The method for preparing the nano hydrogel according to claim 1, characterized in that: In the step (2), the solvent thermal reaction is carried out in a hydrothermal kettle, the reaction temperature is 140° C. to 200° C., and the reaction time is 6 h to 24 h.

6. The method for preparing the nano hydrogel according to claim 1, characterized in that: The mass percentage concentration of the fucoidan in step (3) is 0.5%-3%, and the amount of carbon dots added is 0.5g / L-3g / L.

7. The method for preparing the nano hydrogel according to claim 1, characterized in that: In the step (3), the ethanol dispersion of carbon dots is added dropwise into the fucoidan solution.

8. The method for preparing the nano hydrogel according to claim 1, characterized in that: In the step (4), The centrifugal speed is 5000rpm-8000rpm; The dialysis time is 7 to 14 days, deionized water is used as the dialysis fluid, and the dialysis fluid is replaced once a day; The freeze-drying temperature is -20 to -80°C, and the drying time is 3 to 7 days.

9. The nano hydrogel prepared by the method according to any one of claims 1 to 8.

10. Use of the nano-hydrogel described in claim 9 in neovascularization fluorescence imaging and photodynamic therapy.

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