NIR-II region fluorescent probe suitable for intrathecal injection, preparation method of NIR-II region fluorescent probe and application of NIR-II region fluorescent probe in cerebrovascular imaging

Abstract

The invention discloses an NIR-II region fluorescent probe suitable for intrathecal injection, a preparation method of the NIR-II region fluorescent probe and application of the NIR-II region fluorescent probe in cerebrovascular imaging, and belongs to the technical field of probe preparation. The problem of low resolution of current cerebrovascular imaging is solved. The rare earth nano fluorescent material is prepared into the NIR-II region fluorescent probe, delivery of large-size fluorescent imaging particles is achieved through intrathecal injection, and then cerebral vascular imaging is achieved. According to the rare earth nano fluorescent material, NaErF4: x% Ce serves as a fluorescence emission core, NaYF4: y% Yb serves as a fluorescence emission middle layer, NaYF4 serves as a fluorescence emission shell layer, through Er < 3 + > ion self-sensitization, under 808 nm excitation, an NIR-II region fluorescence emission peak of 1525 nm is achieved, NaYF4 serves as an inert shell layer, the luminous intensity of the fluorescent material is further improved, and NIR-II region high-resolution fluorescence imaging of mouse cerebral vessels is achieved in combination with intrathecal injection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of probe preparation, and relates to a NIR-II region fluorescent probe suitable for intrathecal injection, a preparation method thereof and application thereof in brain blood vessel imaging. BACKGROUND

[0002] Fluorescence imaging technology is one of the important imaging tools in biological research and clinical application. The near-infrared region I (NIR-I region) fluorescence imaging technology is interfered by light scattering, light absorption and biological tissue self-fluorescence in vivo application, resulting in limited imaging spatial resolution, signal background ratio (SBR) and tissue penetration depth. In order to overcome the above problems, the near-infrared region II (NIR-II) fluorescence imaging technology has attracted widespread attention. NIR-II region fluorescence is more conducive to fluorescence imaging. In addition to the further reduction of scattering coefficient at a fixed tissue depth, the NIR-II region fluorescence has an exponential decrease in tissue self-fluorescence, which is almost zero when the wavelength exceeds 1500 nm. Although the light absorption of various biological tissues to NIR-II region fluorescence is slightly higher than that in the NIR-I region, in the case of reducing scattering loss and almost zero self-fluorescence, NIR-II region fluorescence imaging has higher spatial resolution, signal-to-noise ratio and penetration depth. Therefore, the NIR-II region fluorescence imaging technology is suitable for high-resolution imaging requirements due to its higher tissue penetration depth.

[0003] Brain blood vessels play a crucial role in human life activities. The occurrence and development of many brain diseases are closely related to the brain blood vessel system. Therefore, it is of great significance to effectively identify and monitor the structure, morphology and dynamic changes of the brain blood vessel system. However, the existence of the blood-brain barrier makes 98% of small molecule drugs and nearly 100% of large molecule therapeutic drugs unable to penetrate into the brain to play an effective role. The high-resolution imaging of brain blood vessels is severely dependent on the concentration of imaging agents reaching the brain blood vessels, so the blood-brain barrier crossing is the main obstacle that needs to be overcome for high-resolution imaging of brain blood vessels. Current strategies for crossing the blood-brain barrier include intracranial delivery, membrane transporter or receptor-mediated transcellular transport and the like. However, traditional intracranial administration has significant defects. About 2%-5% of patients have the risk of brain hemorrhage, and there is also the risk of inducing epileptic seizures and irreversible cognitive dysfunction. Moreover, it is difficult to achieve repeated administration due to surgical trauma. In the aspect of non-invasive delivery strategies, although the membrane transporter and receptor-mediated transcellular transport technology has the advantage of non-invasion, the off-target effect may lead to accumulation of imaging agents in peripheral organs and insufficient concentration of imaging agents reaching the target. In comparison, the intrathecal injection technology has unique advantages: based on the circulation dynamics of cerebrospinal fluid, imaging agents can be rapidly distributed to the whole ventricular system through the subarachnoid space, achieving delivery of imaging agents across the blood-brain barrier; the degree of puncture damage is significantly reduced compared with craniotomy, and multiple administrations are allowed through the indwelling catheter system to maintain a stable therapeutic window concentration.

[0004] Although there are studies on probes for NIR-II region fluorescence imaging, there are few reports on intrathecal injection. The current study only involves NIR-II region fluorescence imaging materials and preparation and application, or intrathecal injection of drugs, or both. There is currently a lack of research on delivering NIR-II region fluorescence materials through intrathecal injection to cross the blood-brain barrier and achieve high-resolution imaging of cerebral blood vessels. SUMMARY

[0005] The present application provides a NIR-II region fluorescence probe suitable for intrathecal injection, a preparation method thereof and application in cerebral vascular imaging.

[0006] To achieve the above-mentioned purposes, the technical solutions of the present application are as follows: One of the purposes of the present application is to provide a NIR-II region fluorescence probe suitable for intrathecal injection, which comprises a surface ligand and a rare earth nanofluorescent material; the composition of the rare earth nanofluorescent material is NaErF4:x%Ce@NaYF4:y%Yb@NaYF4, wherein x is the doping concentration of Ce, y is the doping concentration of Yb, 0≤x≤2, 0≤y≤100; the particle size of the rare earth nanofluorescent material is less than 100 nm.

[0007] Further limited, the rare earth nanofluorescent material comprises a fluorescence emission core, a fluorescence emission intermediate layer arranged on the fluorescence emission core, and a fluorescence emission shell layer arranged on the fluorescence emission intermediate layer.

[0008] Further limited, the composition of the fluorescence emission core is NaErF4:x%Ce, wherein x is the doping concentration of Ce, 0≤x≤2; the composition of the fluorescence emission intermediate layer is NaYF4:y%Yb, wherein y is the doping concentration of Yb, 0≤y≤100; the composition of the fluorescence emission shell layer is NaYF4; the thickness of the fluorescence emission shell layer is 1-10 nm.

[0009] Further limited, the preparation method of the rare earth nanofluorescent material comprises the following steps: Step one, preparing NaErF4:x%Ce fluorescence emission core particles: mixing Er source, Ce source, oleic acid and octadecene to obtain a mixture, dissolving the mixture into a solution at high temperature, adding F source and Na source to the solution, then performing a reaction, and washing the product after the reaction to obtain NaErF4:x%Ce fluorescence emission core particles; Step 2: Preparation of NaErF4:x%Ce@NaYF4:y%Yb fluorescent emission core-intermediate layer particles: Add Na source, F source, Yb source, Y source and the product from Step 1 into a flask and react. After the reaction is complete, wash the product to obtain NaErF4:x%Ce@NaYF4:y%Yb fluorescent emission core-intermediate layer particles. Step 3: Preparation of rare earth fluorescent nanomaterials: Add the Na source, F source, Y source and the product from step 2 into a three-necked flask and react. After the reaction is complete, wash the product to obtain rare earth fluorescent nanomaterials.

[0010] Further specifying, in step one, the reaction temperature is 260-340 ℃, the amount of oleic acid is 6-15 mL, and the amount of octadecene is 10-20 mL; in step two, the reaction temperature is 260-340 ℃, the amount of oleic acid is 6-15 mL, and the amount of octadecene is 10-20 mL; in step three, the reaction temperature is 260-340 ℃, the amount of oleic acid is 6-15 mL, and the amount of octadecene is 10-20 mL.

[0011] Furthermore, in step one, the Er source is at least one of ErCl3, ErCl3·6H2O, ErCl3·xH2O, and erbium trifluoroacetate; the Ce source is at least one of CeCl3, Ce(C2H3O2)3, and CeCl3·6H2O; and the Na source is at least one of sodium trifluoroacetate and sodium hydroxide. In steps two and three, the Y source is independently selected from at least one of yttrium trifluoroacetate and yttrium acetate or yttrium chloride. In step two, the Yb source is at least one of ytterbium trifluoroacetate, ytterbium acetate, and ytterbium chloride. In steps one, two, and three, the F source is independently selected from at least one of NH4F, sodium trifluoroacetate, erbium trifluoroacetate, ytterbium trifluoroacetate, yttrium trifluoroacetate, and ytterbium trifluoroacetate.

[0012] The second objective of this invention is to provide a method for preparing the above-mentioned NIR-II region fluorescent probe suitable for intrathecal injection. The preparation method is as follows: rare earth nanofluorescent material is dissolved in a solvent, then a surface ligand is added, and the mixture is sonicated to obtain the NIR-II region fluorescent probe.

[0013] Further specified, the solvent is acetone, tetrahydrofuran, water, or cyclohexane, and the surface ligand is DSPE-PEG. 2000 -NH2,DSPE-PEG 2000 DSPE-PEG 2000 -COOH,DSPE-PEG 2000 One or more of -iRGD.

[0014] A third objective of this invention is to provide an application of the aforementioned NIR-II region fluorescent probe suitable for intrathecal injection, specifically for imaging cerebral blood vessels.

[0015] The fourth object of the present application is to provide a method for imaging cerebral blood vessels using the above-mentioned NIR-II region fluorescent probe suitable for intrathecal injection, which comprises dissolving the NIR-II region fluorescent probe in a PBS solution to prepare a NIR-II region fluorescent imaging agent, and injecting the NIR-II region fluorescent imaging agent by intrathecal injection.

[0016] Further limitation, the concentration of the NIR-II region fluorescent imaging agent is 20-40 mg / mL, and the single injection volume of the NIR-II region fluorescent imaging agent is 5-15 μL.

[0017] Further limitation, the NIR-II region probe reaches the cerebral blood vessels of the subject by intrathecal injection.

[0018] Further limitation, the NIR-II region fluorescent probe circulates through the cerebrospinal fluid to cross the blood-brain barrier and image the cerebral blood vessels.

[0019] The beneficial effects of the present application are: (1) The rare earth nanometer fluorescent material of the present application takes NaErF4:x%Ce as the fluorescent emission core, NaYF4:y%Yb as the fluorescent emission intermediate layer, and NaYF4 as the fluorescent emission shell layer (inert shell layer), and realizes NIR-II region fluorescent emission under the excitation of 808 nm laser through Er 3+ ion self-sensitization. Under the excitation of 808 nm laser, it has a NIR-II region fluorescent emission peak of 1525 nm, and NaYF4 as the inert shell layer can further improve the luminous intensity of the fluorescent material. In combination with the intrathecal injection method, high-resolution NIR-II region fluorescent imaging of biological cerebral blood vessels is realized.

[0020] (2) The NaErF4:x%Ce@NaYF4:y%Yb@NaYF4 rare earth nanometer fluorescent material of the present application has NIR-II region fluorescent emission under the excitation of 808 nm laser, and intrathecal injection can realize blood-brain barrier crossing and rapid cerebral blood vessel high-resolution fluorescent imaging. Compared with the existing cerebral blood vessel imaging method, the rare earth nanometer fluorescent material in the present application has a NIR-II region fluorescent emission peak, which is beneficial to high-resolution cerebral blood vessel fluorescent imaging; compared with the existing cerebral blood vessel imaging method, the present application can realize continuous dynamic cerebral blood vessel high-resolution fluorescent imaging, which is convenient for capturing dynamic information of cerebral blood vessels; compared with the existing cerebral blood vessel imaging method, the method of intrathecal injection of rare earth nanoparticles in the present application can directly cross the blood-brain barrier, rapidly deliver the imaging agent to the cerebral blood vessels, and realize high-resolution fluorescent imaging of the cerebral blood vessels. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the transmission electron microscope image of the product obtained in step one of the embodiment 1 of the present application. Figure 2 Transmission electron microscope image of the product obtained in step two of Example 1 of the present application; Figure 3 Transmission electron microscope image of the product obtained in step three of Example 1 of the present application; Figure 4 Fluorescence imaging probe guided mouse brain vascular imaging image of Example 1 of the present application; Figure 5 Near-infrared fluorescence emission spectrum of the rare earth nanometer fluorescent material of Example 1 of the present application under 808 nm laser excitation; Figure 6 Near-infrared fluorescence emission spectrum of the rare earth nanometer fluorescent material of Example 2 of the present application under 808 nm laser excitation; Figure 7 Near-infrared fluorescence emission spectrum of the rare earth nanometer fluorescent material of Example 3 of the present application under 808 nm laser excitation. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be described in detail below with the specific embodiments of the description.

[0023] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the scope of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0024] The experimental methods used in the following specific embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0025] Example 1 The rare earth nanometer fluorescent material of the present embodiment is NaErF4:2%Ce@NaYF4:40%Yb@NaYF4, the particle size is 45 nm, which includes a fluorescence emission core NaErF4:2%Ce, a fluorescence emission intermediate layer NaYF4:40%Yb arranged on the fluorescence emission core and a fluorescence emission shell layer NaYF4 arranged on the fluorescence emission intermediate layer, the thickness of the fluorescence emission shell layer NaYF4 is 1-10 nm, and the specific preparation process of the rare earth fluorescent material is as follows: Step one, preparation of NaErF4:2%Ce fluorescent emission core particles: 0.98 mmol of ErCl3, 0.02 mmol of CeCl3 and 1 mmol of sodium trifluoroacetate were added into a three-neck flask containing 12 mL of oleic acid and 15 mL of octadecene, the system was heated to 300 °C under vacuum until a transparent solution was formed, then cooled to room temperature, 4 mmol of NH4F and 2.5 mmol of NaOH were added, then the reaction system was kept at 305 °C for reaction, and kept for 80 min, after the reaction was completed, the system was cooled to room temperature, an excess of ethanol was added, and centrifuged at 10000 rpm for 10 min, after removing the supernatant, the obtained solid was washed with a mixed solution of anhydrous ethanol and acetone (volume ratio of anhydrous ethanol to acetone was 3:1) for 3 times, to obtain NaErF4:2%Ce fluorescent emission core particles, which were dispersed in cyclohexane for standby; Step two, preparation of NaErF4:2%Ce@NaYF4:40%Yb fluorescent emission core-intermediate layer particles: 0.18 mmol of yttrium trifluoroacetate, 0.12 mmol of ytterbium trifluoroacetate, 0.3 mmol of sodium trifluoroacetate and 0.3 mmol of the product obtained in step one were added into a three-neck flask containing 8 mL of oleic acid and 12 mL of octadecene, the mixture was heated to 100 °C under vacuum until a transparent solution was formed, then the temperature of the reaction system was increased to 310 °C under argon atmosphere and kept for 45 min, after the reaction was completed, the system was cooled to room temperature and an excess of anhydrous ethanol was added, and centrifuged at 10000 rpm for 8 min, after removing the supernatant, the obtained solid was washed with anhydrous ethanol for 2 times, to obtain NaErF4:2%Ce@NaYF4:40%Yb fluorescent emission core-intermediate layer particles, which were dispersed in cyclohexane for standby; Step three, preparation of rare earth nanometer fluorescent material: 0.4 mmol of yttrium trifluoroacetate, 0.4 mmol of sodium trifluoroacetate and 0.3 mmol of the product obtained in step two were added into a three-neck flask containing 7 mL of oleic acid and 14 mL of octadecene, the mixture was heated to 100 °C under vacuum until a transparent solution was formed, then the temperature of the reaction system was increased to 305 °C under argon atmosphere and kept for 55 min, after the reaction was completed, the system was cooled to room temperature and an excess of anhydrous ethanol was added, and centrifuged at 10000 rpm for 15 min, after removing the supernatant, the obtained solid was washed with anhydrous ethanol for 2 times, to obtain NaErF4:2%Ce@NaYF4:40%Yb@NaYF4 fluorescent emission core-intermediate layer-outer shell layer particles, i.e. rare earth nanometer fluorescent material, which were dispersed in cyclohexane for standby.

[0026] The above-mentioned rare earth nanometer fluorescent material, i.e. NaErF4: 2%Ce@NaYF4: 40%Yb@NaYF4 fluorescent emission core-intermediate layer-outer shell nanoparticles and surface ligand DSPE-PEG 2000 -NH2 (mass ratio of nanoparticles and surface ligand is 1:2) were mixed in acetone, and ultrasonic treatment was performed under ice water bath condition for 10-20 min to obtain water-soluble nanoparticles, i.e. NIR-II region fluorescent probe (Er NPs).

[0027] The Er NPs were dissolved in PBS solution (pH=7.4) to form an imaging agent with a concentration of 25 mg / mL, and 8 μL of the imaging agent was injected into the mouse body through intrathecal injection at the midline of the mouse iliac crest.

[0028] Figures 1-3 The TEM images of the products of steps one to three of the present embodiment, respectively. Figure 4 The mouse brain blood vessel imaging diagram under the excitation of 808 nm laser of the Er NPs fluorescent imaging probe. Figure 5 The near-infrared fluorescent emission spectrum diagram of the rare earth nanometer fluorescent material of the present embodiment under the excitation of 808 nm laser, which shows that under the excitation of 808 nm laser, the rare earth nanometer fluorescent material has a fluorescent emission with a peak value of 1525 nm in the NIR-II region.

[0029] Embodiment 2 The difference between the present embodiment and embodiment 1 is that the rare earth nanometer fluorescent material of the present embodiment is NaErF4: 2%Ce@NaYF4: 60%Yb@NaYF4, the particle size is 38 nm, y in the NaErF4: 2%Ce@NaYF4:y%Yb fluorescent emission core-intermediate layer nanoparticles of step two is 60, the amount of yttrium trifluoride is 0.12 mmol, the amount of ytterbium trifluoride is 0.18 mmol, the temperature of the reaction system is increased to 315 °C under argon atmosphere and is kept for 55 min, and the centrifugation is performed at 11000 rpm for 15 min; the keeping time in step three is 65 min, and the centrifugation is performed at 12000 rpm for 20 min, and the rest of the operation and process steps are the same as those of embodiment 1.

[0030] The above-mentioned rare earth nanometer fluorescent material, i.e. NaErF4: 2%Ce@NaYF4: 60%Yb@NaYF4 fluorescent emission core-intermediate layer-outer shell nanoparticles and surface ligand DSPE-PEG 2000 -NH2 (mass ratio of nanoparticles and surface ligand is 1:2) were mixed in acetone, and ultrasonic treatment was performed under ice water bath condition for 10-20 min to obtain water-soluble nanoparticles, i.e. NIR-II region fluorescent probe (Er NPs).

[0031] The Er NPs were dissolved in PBS solution (pH=7.4) to form an imaging agent with a concentration of 25 mg / mL, and 8 μL of the imaging agent was injected into the mouse body through intrathecal injection at the midline of the mouse iliac crest.

[0032] Figure 6 The near-infrared fluorescence emission spectrum of the rare earth nanophosphor under 808 nm laser excitation in this embodiment can be seen to have a fluorescence emission peak at 1525 nm in the NIR-II region under 808 nm laser excitation.

[0033] Embodiment 3 The difference between this embodiment and Embodiment 1 is that the rare earth nanophosphor in this embodiment is NaErF4@NaYF4:80%Yb@NaYF4, the particle size is 45 nm, no CeCl3 is added in Step One, the amount of ErCl3 is 1 mmol, the amount of sodium trifluoroacetate is 1 mmol; in Step Two, the value of y in the NaErF4@NaYF4:y%Yb fluorescence emission core-intermediate layer particle is 80, the amount of yttrium trifluoroacetate is 0.06 mmol, and the amount of ytterbium trifluoroacetate is 0.24 mmol, and the remaining operations and process steps are the same as in Embodiment 1.

[0034] The above rare earth nanophosphor, i.e., the NaErF4@NaYF4:80%Yb@NaYF4 fluorescence emission core-intermediate layer-shell nanoparticle and the surface ligand DSPE-PEG 2000 -NH2(nanoparticle and surface ligand mass ratio 1:2) were mixed in acetone, and ultrasonic treatment was performed for 10-20 min under ice water bath conditions to obtain water-soluble nanoparticles, i.e., NIR-II region fluorescence probes (Er NPs).

[0035] The Er NPs were dissolved in PBS solution (pH=7.4) to form an imaging agent with a concentration of 25 mg / mL, and 8 μL of the imaging agent was injected into the mouse body through intrathecal injection at the midline of the mouse iliac crest.

[0036] Figure 7 The near-infrared fluorescence emission spectrum of the rare earth nanophosphor under 808 nm laser excitation in this embodiment can be seen to have a fluorescence emission peak at 1525 nm in the NIR-II region under 808 nm laser excitation.

[0037] The above described, only for the preferred specific embodiments of the present application, but the scope of protection of the present application is not limited to this, any skilled in the art of the technical personnel in the technical range disclosed by the present application, according to the technical scheme of the present application and the invention concept of equivalent replacement or change, should be covered within the scope of protection of the present application.

Claims

1. A fluorescent probe in the NIR-II region suitable for intrathecal injection, characterized in that, The probe comprises surface ligands and rare-earth nanofluorescent materials; The rare earth nanofluorescent material has the following composition: NaErF4:x%Ce@NaYF4:y%Yb@NaYF4, where x is the doping concentration of Ce, y is the doping concentration of Yb, 0≤x≤2, 0≤y≤100; The rare earth nanofluorescent material has a particle size of less than 100 nm.

2. The NIR-II region fluorescent probe according to claim 1, characterized in that, Rare earth nanofluorescent materials include a fluorescence emission core, a fluorescence emission intermediate layer disposed on the fluorescence emission core, and a fluorescence emission outer shell layer disposed on the fluorescence emission intermediate layer.

3. The NIR-II region fluorescent probe according to claim 2, characterized in that, The fluorescent emitting core is composed of NaErF4:x%Ce, where x is the doping concentration of Ce, 0≤x≤2; the fluorescent emitting intermediate layer is composed of NaYF4:y%Yb, where y is the doping concentration of Yb, 0≤y≤100; the fluorescent emitting outer shell is composed of NaYF4; the thickness of the fluorescent emitting outer shell is 1-10 nm.

4. The NIR-II region fluorescent probe according to claim 1, characterized in that, The preparation method of rare earth nanofluorescent materials includes the following steps: Step 1: Preparation of NaErF4:x%Ce fluorescent emission core particles: Er source, Ce source, oleic acid and octadecene are mixed to obtain a mixture. After the mixture is dissolved into a solution at high temperature, F source and Na source are added to the solution, and then the reaction is carried out. After the reaction is completed, the product is washed to obtain NaErF4:x%Ce fluorescent emission core particles. Step 2: Preparation of NaErF4:x%Ce@NaYF4:y%Yb fluorescent emission core-intermediate layer particles: Add Na source, F source, Yb source, Y source and the product from Step 1 into a flask and react. After the reaction is complete, wash the product to obtain NaErF4:x%Ce@NaYF4:y%Yb fluorescent emission core-intermediate layer particles. Step 3: Preparation of rare earth fluorescent nanomaterials: Add the Na source, F source, Y source and the product from step 2 into a three-necked flask and react. After the reaction is complete, wash the product to obtain rare earth fluorescent nanomaterials.

5. The NIR-II region fluorescent probe according to claim 4, characterized in that, The reaction temperature in step one is 260-340 ℃; the reaction temperature in step two is 260-340 ℃; the reaction temperature in step three is 260-340 ℃.

6. The NIR-II region fluorescent probe according to claim 4, characterized in that, In step one, the Er source is at least one of ErCl3, ErCl3·6H2O, ErCl3·xH2O, and erbium trifluoroacetate; the Ce source is at least one of CeCl3, Ce(C2H3O2)3, and CeCl3·6H2O; and the Na source is at least one of sodium trifluoroacetate and sodium hydroxide. In steps two and three, the Y source is independently selected from at least one of yttrium trifluoroacetate and yttrium acetate or yttrium chloride. In step two, the Yb source is at least one of ytterbium trifluoroacetate, ytterbium acetate, and ytterbium chloride. In steps one, two, and three, the F source is independently selected from at least one of NH4F, sodium trifluoroacetate, erbium trifluoroacetate, ytterbium trifluoroacetate, yttrium trifluoroacetate, and ytterbium trifluoroacetate.

7. A method for preparing a NIR-II region fluorescent probe according to any one of claims 1-6, characterized in that, The preparation method is as follows: rare earth nano-fluorescent materials are dissolved in a solvent, then surface ligands are added, and the mixture is sonicated to obtain a fluorescent probe in the NIR-II region.

8. The application of the NIR-II region fluorescent probe according to any one of claims 1-6, characterized in that, This fluorescent probe is used for imaging brain blood vessels.

9. A method for imaging cerebral blood vessels using a NIR-II region fluorescent probe in the application described in claim 8, characterized in that, This method involves dissolving a fluorescent probe in NIR-II region in PBS solution to prepare a fluorescent imaging agent for NIR-II region, and then injecting the fluorescent imaging agent for NIR-II region via intrathecal injection.

10. The method according to claim 9, characterized in that, The concentration of the NIR-II region fluorescent imaging agent is 20-40 mg / mL, and the single injection volume of the NIR-II region fluorescent imaging agent is 5-15 μL.

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