A High-Brightness NIR-II Region Photothermal Agent Based on Aza-BODIPY, Preparation Method and Application

Abstract

The present invention provides a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, a preparation method thereof, and an application thereof, belonging to the technical field of photothermal therapy. It reveals the dual-improving mechanism of side chains in enhancing molecular brightness and photothermal performance, and side chain engineering can be used as an effective method to simultaneously regulate radiative and non-radiative transition processes. Specifically, the introduction of side chains promotes intramolecular motion in the aggregated state by further twisting the molecular conformation, extending the intermolecular distance, and providing a looser packing environment for intramolecular motion (too large side chains will cause large steric hindrance in the aggregated state), thereby promoting non-radiative transitions to generate photothermal properties. In addition, although intramolecular motion is promoted with the assistance of side chains, π-π stacking also decreases with the extended intermolecular distance, thus promoting fluorescence in the aggregated state. The introduction of alkyl chains enhances both fluorescence and photothermal properties, and can be used for photothermal therapy under fluorescence guidance.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal therapy, and particularly relates to a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, a preparation method thereof, and an application thereof. Background Art

[0002] Optodiagnostics integrates optical imaging diagnosis and light-triggered precise therapy, and is an emerging biotechnology. Due to its minimally invasive nature, high spatiotemporal resolution, high biosafety, and high anti-tumor ability, it plays a significant and increasingly important role in precise cancer treatment. As the core of the photothermal system, the development of high-performance photothermal agents is crucial for the development of photothermal research. In particular, photothermal agents emitting in the second near-infrared region (NIR-II, 1000 - 1700 nm) have attracted extensive attention in the past few years, with higher signal-to-noise ratios, deeper penetration depths, and lower light absorption, scattering, and autofluorescence interference from biological tissues. To obtain efficient NIR-II photothermal agents, four strategies are usually applied to redshift the absorption and emission wavelengths of fluorophores: 1) extending the conjugated chain of the fluorophore; 2) enhancing the intramolecular donor-acceptor (D-A) interaction; 3) adjusting the strength and number of donors / acceptors in the fluorophore; 4) preparing J-aggregates.

[0003] Despite many efforts, the structure-activity relationships of most NIR-II photothermal agents have remained largely unexplored to date. In addition, most of the above-mentioned photothermal agents have low fluorescence quantum yields (QYs) and photothermal conversion efficiencies (PCEs), resulting in low imaging resolutions and limited anti-cancer activities. Therefore, simultaneously improving the QY and PCE of NIR-II photothermal agents is of great significance for photothermal anti-cancer research.

[0004] Unfortunately, simultaneously enhancing the QY and PCE has long been considered a contradiction, making the realization of NIR-II photothermal agents with both high QY and strong PCE very challenging. Currently, the methods for improving the QY in the aggregated state mainly include: 1) using steric hindrance effects to reduce intermolecular π-π interactions; 2) suppressing the twisted intramolecular charge transfer in the excited state. The main strategies for improving the PCE rely on introducing fast-moving rotors to accelerate the non-radiative relaxation process. However, almost without exception, these methods lead to a decrease in molecular planarity and molar extinction coefficient (ε), and thus reduce the total excited state energy of the photothermal agent. Therefore, it is very crucial but quite challenging to develop NIR-II photothermal agents with good planarity, high QY, and PCE. Summary of the Invention

[0005] To overcome the disadvantages of the above-mentioned prior art, the object of the present invention is to provide a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, a preparation method thereof, and an application thereof, so as to solve the technical problems of the reduction of molecular planarity and molar extinction coefficient (ε), and thus the reduction of the total excited state energy of the photothermal agent, as well as the existing low imaging resolution and side effects of photothermal therapy.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, and the structural formula of the photothermal agent is as follows:

[0008] 。

[0009] The present invention also provides a preparation method of the high-brightness NIR-II region photothermal agent based on Aza-BODIPY according to claim 1, comprising the following steps:

[0010] Step 1: Add N,N-dimethylformamide to phosphorus oxychloride, and stir under a protective gas to obtain a Vilsmeier-Haack reagent; mix julolidine with N,N-dimethylformamide and then add it to the Vilsmeier-Haack reagent, then raise the temperature for the first reaction. After the first reaction is completed, cool to room temperature and pour the mixture into ice water to quench the reaction, then filter and dry to obtain an intermediate product S1;

[0011] Step 2: Mix the intermediate product S1, 4-bromoacetophenone, aqueous sodium hydroxide solution, and ethanol uniformly for the second reaction. After the second reaction is completed, pour the mixed solution of the second reaction product into ice water to quench the reaction, then filter and dry to obtain an intermediate product S2;

[0012] Step 3: Mix the intermediate product S2, nitromethane, N,N-diisopropylethylamine, and methanol uniformly, then raise the temperature for the third reaction. Pour the solution of the third reaction product into saturated sodium chloride aqueous solution to stop the reaction, then extract, dry, filter, and purify to obtain an intermediate product S3;

[0013] Step 4: Mix the intermediate product S3, ammonium acetate, and n-butanol uniformly, raise the temperature for the fourth reaction, then vacuum concentrate and filter by suction, separate the solid and wash to obtain an intermediate product S4;

[0014] Step 5: Mix the intermediate product S4, N,N-diisopropylethylamine with dry dichloromethane, then add boron trifluoride diethyl etherate, stir in the dark at room temperature for the fifth reaction. Dilute the fifth reaction product with ice water, then extract, dry, filter, concentrate, and purify to obtain an intermediate product S5;

[0015] Step 6: Under a protective gas, mix the intermediate product S5, 4-pyridylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and a solution of potassium carbonate, 1,4-dioxane and water, heat up for the sixth reaction, after the sixth reaction is completed, cool to room temperature, then concentrate, filter and purify to obtain the intermediate product S6;

[0016] Step 7: Under a protective gas, mix the intermediate product S6 with 1-bromododecane and chloroform, heat up for the seventh reaction, after the seventh reaction is completed, cool to room temperature, then concentrate, filter and purify to obtain WS5.

[0017] In a specific embodiment, in Step 1, the molar ratio of phosphorus oxychloride, N,N-dimethylformamide to julolidine is 7.62:22.87:6.93 mmol; the temperature of the first reaction is 20~30 °C; the time of the first reaction is 3~4 h.

[0018] In a specific embodiment, in Step 2, the molar ratio of the intermediate product S1 to 4-bromoacetophenone is 1:1; the temperature of the second reaction is 25~30 °C.

[0019] In a specific embodiment, in Step 3, the molar ratio of the intermediate product S2 to N,N-diisopropylethylamine is 5:5.5; the temperature of the third reaction is 60~70 °C.

[0020] In a specific embodiment, in Step 4, the molar ratio of the intermediate product S3 to ammonium acetate is 1:15; the temperature of the fourth reaction is 100~110 °C.

[0021] In a specific embodiment, in Step 5, the molar ratio of the intermediate product S4, N,N-diisopropylethylamine to boron trifluoride diethyl etherate is 0.11:1.1:2.

[0022] In a specific embodiment, in Step 6, the molar ratio of the intermediate product S5, 4-pyridylphenylboronic acid, tetrakis(triphenylphosphine)palladium and potassium carbonate is 0.06:0.12:0.1:7.5; the temperature of the sixth reaction is 70~80 °C; the volume ratio of 1,4-dioxane to water is 5:1.

[0023] In a specific embodiment, in Step 7, the molar ratio of the intermediate product S6 to 1-bromododecane is 1:1; the temperature of the seventh reaction is 80~90 °C.

[0024] The present invention also provides an application of the high-brightness NIR-II region photothermal agent according to the above in the preparation of photothermal therapy drugs.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a high-brightness NIR-II region photothermal agent (WS5) based on Aza-BODIPY. The introduction of an alkyl chain promotes intramolecular motion in the aggregated state by further distorting the molecular conformation, extending the intermolecular distance, and providing a looser packing environment for intramolecular motion, thereby promoting non-radiative transitions to produce efficient photothermal properties (PCE). In addition, although the intramolecular motion is promoted with the assistance of the alkyl chain, the π-π stacking also decreases with the extended intermolecular distance, thus promoting fluorescence (QY) in the aggregated state. Therefore, the introduction of the alkyl chain enhances both fluorescence and photothermal properties, and can be used for photothermal therapy under fluorescence guidance.

[0027] Furthermore, the photothermal agent (WS5) of the present invention has strong absorption in the second near-infrared region, high fluorescence quantum yield and photothermal conversion efficiency. After coating with DSPE-PEG 5000 it has good biocompatibility, low toxicity and side effects on organisms, can be biodegraded, and has certain potential for biological applications. The dual improvement mechanism of the side chain structure on improving brightness and photothermal performance is explored, which provides a new idea for solving the problem of energy distribution depending on two competing photophysical processes. The therapeutic effect of deep tumors under the guidance of near-infrared II imaging of photothermal agents with dual optimization of high brightness and high photothermal performance is studied. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a test diagram of the basic photophysical properties of the WS5 molecule of the present invention; among them, Figure 1 in (a) is the spatial configuration diagram of the WS5 molecule optimized by density functional theory; Figure 1 in (b) is the determination diagram of the molar extinction coefficient of the WS5 molecule; Figure 1 in (c) is the emission spectrum diagram of the WS5 molecule; Figure 1 in (d) is the test diagram of the photothermal performance of the WS5 molecule;

[0029] Figure 2 It is a test diagram of the basic photophysical properties of WS5@NPs of the present invention; among them, Figure 2 in (a) is the DLS and TEM characterization diagram of WS5@NPs; Figure 2 in (b) is the determination diagram of the molar extinction coefficient of WS5@NPs; Figure 2 in (c) is the emission spectrum diagram of WS5@NPs; Figure 2 in (d) is the test diagram of the photothermal performance of WS5@NPs; Figure 2 in (e) is the determination diagram of the photostability of WS5@NPs; Figure 2 in (f) is the test diagram of the thermal stability of WS5@NPs;

[0030] Figure 3 These are the in vitro cell (143B cells) experimental diagrams of WS5@NPs of the present invention; among them, Figure 3 in (a) is the cell viability test diagram of WS5@NPs at different drug concentrations (0.23 W cm -2 ); Figure 3 in (b) is the diagram for determining the IC50 value of WS5@NPs; Figure 3 in (c) is the schematic diagram of the uptake of WS5@NPs by 143B cells; Figure 3 in (d) is the live / dead staining experimental diagram of WS5@NPs, phosphate buffered saline scale bar = 100 μm; Figure 3 in (e) is the schematic diagram of detecting the apoptosis of 143B cells by flow cytometry;

[0031] Figure 4 In (a) is the whole-body vascular imaging diagram of WS5@NPs injected into a mouse under a 980 nm laser; among them, (1) in (a), (2) in (a), and (3) in (a) are respectively the whole-body vascular imaging diagrams of WS5@NPs injected into a mouse at 1100LP, 1200LP, and 1300LP; Figure 4 In (b) is the comparison diagram of the vascular diameters between the green, blue, and red lines;

[0032] Figure 5 This is the schematic diagram of the photothermal therapy process of WS5@NPs on mouse osteosarcoma; among them, Figure 5 in (a) is the schematic diagram of the in vivo experiment time axis; Figure 5 in (b) is the comparison diagram of the photothermal images of the PBS + 1064 nm group and the WS5@NPs + 1064 nm group; Figure 5 in (c) are the X-ray films of the osteosarcoma mice at 0, 6, and 10 days; Figure 5 in (d) are the camera photos of the osteosarcoma mice at 0, 6, and 10 days; Figure 5 in (e) is the schematic diagram of the change in the tumor size of the mice after 10 days of photothermal treatment (n = 5, *p <0.05); Figure 5 in (f) is the tumor photo; Figure 5 in (g) is the diagram of the tumor weight after the mice are dissected; Figure 5 in (h) is the immunohistochemical detection diagram of the treatment group; Figure 5 in (i) is the histological examination diagram; Figure 5 in (j) is the histological schematic diagram of the skin tissue in the laser irradiation area;

[0033] Figure 6Schematic diagram of the preparation method of the NIR-II photothermal agent with high brightness and high photothermal performance in Example 1 of the present invention;

[0034] Figure 7 Schematic diagram of the process of WS5 nanosizing to generate WS5@NPs;

[0035] Figure 8 Structural formula of WS5. Detailed implementation manners

[0036] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0038] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

[0039] In this article, unless otherwise specified, "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0040] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0041] The present invention provides a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, its preparation method and application.

[0042] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0043] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0044] The present invention provides a preparation method of a high-brightness NIR-II region photothermal agent based on Aza-BODIPY, and the specific steps are as follows:

[0045] Step 1: Synthesis of compound S1

[0046] Under ice-salt bath conditions, phosphorus oxychloride (POCl 3 , 7.62 mmol) was slowly dropped into a 100 mL round-bottom flask containing dry N, N -dimethylformamide (DMF, 22.87 mmol). After stirring for 2 h under the protection of N 2 , a Vilsmeier-Haack reagent was obtained. Then, julolidine (6.93 mmol) and dry DMF (10 mL) were slowly added to the flask containing the Vilsmeier-Haack reagent. After that, the mixture was stirred at 20-30 o °C for 3-4 hours. After cooling to room temperature, the mixture was poured into ice water (100 mL) to quench the reaction. Then, the precipitate was filtered to obtain a pale yellow solid. Finally, the solid was dried in a vacuum drying oven overnight to obtain compound S1. That is, the molar ratio of phosphorus oxychloride, N,N-dimethylformamide to julolidine is 7.62:22.87:6.93 mmol.

[0047] Step 2: Synthesis of compound S2

[0048] Compound S1 (10 mmol), 4-bromoacetophenone (10 mmol) and aqueous sodium hydroxide solution (NaOH, 20%, 10 mL) were slowly added to a 100 mL round-bottom flask containing ethanol (20 mL). The mixture was stirred at room temperature (25 - 30 °C) for 24 hours, and then the reaction mixture was poured into ice water (100 mL) to quench the reaction. After stirring for another 2 hours, the precipitate was filtered to obtain a red solid. Subsequently, the red solid product was dried in a vacuum drying oven overnight to obtain compound S2. That is, the molar ratio of compound S1 to 4-bromoacetophenone is 1:1

[0049] Step 3: Synthesis of compound S3

[0050] Compound S2 (5 mmol), nitromethane (1.00 mL) and N , N -diisopropylethylamine (DIPEA, 5.5 mmol) were slowly added to a round-bottom flask containing methanol (CH 3 OH, 20 mL). After stirring at 60 - 70 °C for 24 h, the reaction solution was poured into a beaker containing saturated sodium chloride aqueous solution (10 mL) to stop the reaction, and then extracted with ethyl acetate (30 mL). The obtained organic solution was dried over anhydrous sodium sulfate, filtered to obtain the crude product, and the crude product was purified by column chromatography (silica gel, ethyl acetate / petroleum ether = 1 / 10) to obtain a yellow solid. That is, the molar ratio of compound S2 to N,N-diisopropylethylamine is 5:5.5

[0051] Step 4: Synthesis of compound S4

[0052] Compound S3 (1.0 mmol) and ammonium acetate (NH 4 OAc, 15.0 mmol) were added to a 100 mL round-bottom flask containing n-butanol (n-BuOH, 20 mL). After stirring at 100 - 110 °C for 24 h, it was cooled to room temperature, and then concentrated in vacuo to 5 mL and filtered by suction. The separated solid was washed with ethanol (2 × 5 mL), and finally a blue-black solid was obtained. The molar ratio of compound S3 to ammonium acetate is 1:15

[0053] Step 5: Synthesis of compound S5

[0054] Under the protection of N 2 , compound S4 (0.11 mmol) and DIPEA (1.1 mmol) were added to a 100 mL round-bottom flask containing dry dichloromethane (DCM, 20 mL). Then, BF 3 •Et 2O (2.0 mmol) was slowly added dropwise into the solution, and the mixture was stirred in the dark at room temperature for 24 h. Then it was diluted with ice water (20 mL) and extracted with DCM (3 × 20 mL). The organic solution was dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. The crude product was purified by column chromatography (silica gel, dichloromethane / petroleum ether = 1 / 1) to obtain a solid with metallic luster. That is, the molar ratio of compound S4, N,N-diisopropylethylamine to boron trifluoride diethyl etherate is 0.11:1.1:2.

[0055] Step 6: Synthesis of compound S6

[0056] Under N 2 protection, compound S5 (0.06 mmol), 4-pyridylphenylboronic acid (0.12 mmol), tetrakis(triphenylphosphine)palladium (Pd(PPh 3 ) 4 , 0.1 mmol), potassium carbonate (K 2 CO 3 , 7.5 mmol) and 1,4-dioxane / water (10 mL, 5 / 1) were added to a 50 mL round-bottom flask respectively. The mixture was stirred at 70 - 80 °C for 24 h, then the reaction was cooled to room temperature, and the solvent was concentrated in vacuo to 5 mL. The crude product was obtained by filtration. The crude product was purified by column chromatography (silica gel, methanol / dichloromethane = 1 / 50) to obtain a blue-black solid. That is, the molar ratio of compound S5, 4-pyridylphenylboronic acid, tetrakis(triphenylphosphine)palladium and potassium carbonate is 0.06:0.12:0.1:7.5.

[0057] Step 7: Synthesis of compound WS5

[0058] Under N 2 protection, S6 (0.06 mmol) and 1-bromododecane (0.06 mmol) were added to a round-bottom flask containing chloroform (CHCl 3 , 10 mL), and the mixture was stirred at 80 - 90 °C for 24 h. The reaction was cooled to room temperature, and the solvent was concentrated in vacuo. Finally, the WS5 blue-green solid was obtained by purification through column chromatography (silica gel, methanol / dichloromethane = 1 / 25). That is, the molar ratio of compound S6 to 1-bromododecane is 1:1.

[0059] Step 8: Synthesis of compound WS5@NPs

[0060] WS5 and DSPE-mPEG 5000 were dissolved in tetrahydrofuran and mixed uniformly by ultrasonic as the stock solution. Then the above stock solution was injected into deionized water with a syringe and dispersed by a cell disruptor. After that, the solution was treated with N 2Protect by stirring in a fume hood to evaporate tetrahydrofuran. Finally, filter and purify the generated nanoparticles (volume fixed to 1 mL) with a 0.45 μm ultrafiltration filter (Millipore). Finally, WS5@NPs with a concentration of 1 mg / mL are obtained.

[0061] Among them, the introduction of the side-chain structure enhances the electron-donating and electron-withdrawing abilities of the donor and acceptor, manifested as the main absorption and emission peaks of the WS5 molecule exceeding 1000 nm. In addition, the WS5 molecule shows a red shift in the absorption / emission wavelength with the increase of solvent polarity in different polar solvents, indicating the existence of an obvious intramolecular charge transfer state in the molecule. At the same time, the ultraviolet absorption spectra at different concentrations show that the molar extinction coefficient of the WS5 molecule is higher than 10000 M -1 cm -1 , that is, the WS5 molecule shows a high light absorption ability. In addition, WS5 is coated with an amphiphilic polymer (DSPE-mPEG 5000 ) to form nanoparticles (WS5@NPs).

[0062] Compared with the WS5 molecule, the absorption spectrum of WS5@NPs changes significantly. Usually, the main reasons for these changes are the Coulomb coupling effect and the intermolecular interaction in the nanoparticles. From the results of photophysical tests, the absorption spectrum of WS5@NPs is significantly broadened compared with that of WS5, indicating the coexistence of multiple aggregation states. Compared with the absorption spectrum of WS5, the absorption spectrum of WS5@NPs has a slight blue shift, indicating the existence of the Coulomb coupling effect in the molecules of the nanoparticles after coating.

[0063] All in all, the introduction of the side chain prolongs the intermolecular distance in the nanoparticles, manifested as the weakening of the π-π intermolecular interaction and the enhancement of fluorescence. And the extended intermolecular distance provides a more loose movement space for the molecules, resulting in enhanced photothermal effect. Therefore, a NIR-II photothermal agent with high brightness and high photothermal performance is obtained.

[0064] Example 1

[0065] As Figure 6 , Figure 7 and Figure 8 shown, prepare compound S1: Under ice-salt bath conditions, slowly drip phosphorus oxychloride (POCl 3 , 1.17 g, 7.62 mmol) into a 100 mL round-bottom flask containing dry N, N -dimethylformamide (DMF, 1.67 g, 22.87 mmol). Under N 2Under protection, stir for 2 h to obtain the Vilsmeier-Haack reagent. Then slowly add julolidine (1.20 g, 6.93 mmol) and dry DMF (10 mL) to the flask containing the Vilsmeier-Haack reagent. After that, stir at 30 o °C for 4 h. After cooling to room temperature, pour the mixture into ice water (100 mL) to quench the reaction. Then, filter the precipitate to obtain a pale yellow solid. Finally, dry the solid in a vacuum drying oven overnight to obtain compound S1 (yield 78%). 1 1H NMR (500 MHz, CDCl 3 ) δ / ppm 9.60 (s, 1H), 7.29 (s, 2H), 3.29 (t, J J = 5.0, 4H), 2.77 (t, J J = 10.0, 4H), 1.97 (m, 4H). 13 13C NMR (126 MHz, CDCl 3 ) δ / ppm 190.1, 147.9, 129.5, 124.1, 120.4, 50.0, 27.6, 21.3.

[0066] Preparation of compound S2: Slowly add compound S1 (2.00 g, 10 mmol), 4-bromoacetophenone (2.00 g, 10 mmol) and aqueous sodium hydroxide solution (NaOH, 20%, 10 mL) to a 100 mL round-bottom flask containing ethanol (20 mL). Stir the mixture at room temperature for 24 h, then pour the reaction mixture into ice water (100 mL) to quench the reaction. After stirring for another 2 h, filter the precipitate to obtain a red solid. Subsequently, dry the red solid product in a vacuum drying oven overnight to obtain compound S2 (yield 80%). 1 1H NMR (500 MHz, CDCl 3 ) δ / ppm 7.85 (d, J J = 10.0 Hz, 2H), 7.69 (d, J J = 20.0 Hz, 1H), 7.59 (d, J J = 10.0 Hz, 2H), 7.18 (d, J J = 20.0 Hz, 1H), 7.11 (s, 2H), 3.26 (t, J J = 5.0 Hz, 4H), 2.76 (t, J= 5.0 Hz, 4H), 1.97 (m, 4H). 13 CNMR (126 MHz, CDCl 3 ) δ / ppm 189.3, 147.0, 145.5, 138.1, 131.6, 129.9, 128.4,126.8, 121.3, 121.0, 114.9, 108.1, 105.9, 50.0, 27.7, 21.5. IT-TOF / MS: [M +H] + calcd: 382.0728, found: 382.0804.

[0067] Preparation of Compound S3: Compound S2 (1.00 g, 5 mmol), nitromethane (1.00 mL) and N , N -diisopropylethylamine (DIPEA, 1.0 mL, 5.5 mmol) were slowly added to a round-bottom flask containing methanol (CH 3 OH, 20 mL). After stirring at 70 o °C for 24 h, the reaction solution was poured into a beaker containing saturated aqueous sodium chloride solution (10 mL) to stop the reaction, and then extracted with ethyl acetate (30 mL). The obtained organic solution was dried over anhydrous sodium sulfate, filtered to obtain the crude product, and the crude product was purified by column chromatography (silica gel, ethyl acetate / petroleum ether = 1 / 10) to obtain a yellow solid (yield 67%). 1 H NMR (500 MHz, CDCl 3 ) δ / ppm 7.76 (d, J = 15.0 Hz, 2H), 7.59 (d, J = 10.0 Hz,2H), 6.63 (s, 2H), 4,72 (t, J = 5.0 Hz, 1H), 4.60 (t, J = 5.0 Hz,1H), 3.98 (t, J =10.0 Hz, 1H). 3.38 (m, 2H). 3.10 (t, J = 5.0 Hz, 4H), 2.70 (t, J = 5.0 Hz, 4H),1.97 (m, 4H). 13 C NMR (126 MHz, CDCl 3) δ / ppm 196.5, 142.5, 135.3, 132.0, 129.6, 128.6, 125.8, 125.4, 121.8, 80.0, 49.9, 41.9, 38.6, 27.7, 21.9, 14.8. IT-TOF / MS: [M + H] + calcd: 443.0892, found: 443.0965.

[0068] Preparation of Compound S4: Compound S3 (1.00 g, 1.0 mmol) and ammonium acetate (NH 4 OAc, 1.16 g, 15.0 mmol) were added to a 100 mL round-bottom flask containing n-butanol (n-BuOH, 20 mL). After stirring at 110 o °C for 24 h, it was cooled to room temperature, then concentrated in vacuo to 5 mL and filtered by suction. The separated solid was washed with ethanol (2 × 5 mL), and finally a blue-black solid was obtained (yield 37%). 1 H NMR (500 MHz, CDCl 3 ) δ / ppm 7.77 (d, J J = 15.0 Hz, 4H), 7.63 (d, J J = 10.0 Hz, 4H), 7.56 (s, 4H), 6.94 (s, 2H), 5.30 (s, 1H), 3.22 (t, J J = 5.0 Hz, 8H), 2.76 (t, J J = 10.0 Hz, 8H), 2.01 (m, 8H). 13 C NMR (126 MHz, CDCl 3 ) δ / ppm 156.1, 150.5, 143.9, 138.8, 131.8, 128.7, 125.5, 124.5, 123.3, 121.7, 115.8, 49.9, 27.9, 21.8, 1.0.

[0069] Preparation of Compound S5: Under the protection of N 2 , Compound S4 (80 mg, 0.11 mmol) and DIPEA (0.2 mL, 1.1 mmol) were added to a 100 mL round-bottom flask containing dry dichloromethane (DCM, 20 mL). Then, BF 3 •Et 2O (0.28 mL, 2.0 mmol) was slowly added dropwise to the solution, and the mixture was stirred in the dark at room temperature for 24 h. Then it was diluted with ice water (20 mL) and extracted with DCM (3 × 20 mL). The organic solution was dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. The crude product was purified by column chromatography (silica gel, dichloromethane / petroleum ether = 1 / 1) to obtain a solid with metallic luster (yield 84%). 1 HNMR (500 MHz, CDCl 3 ) δ / ppm 7.86 (d, J = 10.0 Hz, 4H), 7.60 (s, 4H), 7.56 (d, J =10.0 Hz, 4H), 6.69 (s, 2H), 3.30 (t, J = 5.0 Hz, 8H), 2.77 (t, J = 5.0 Hz, 8H),2.00 (m, 8H). 13 C NMR (126 MHz, CDCl 3 ) δ / ppm 156.1, 150.5, 143.9, 138.8, 131.8,128.7, 125.5, 124.5, 123.3, 121.7, 115.8, 49.9, 30.9, 29.7, 27.9, 24.4, 21.8,11.2, 1.4. MALDI-TOF / MS: [M] + calcd: 845.1530, found: 845.1960.

[0070] Preparation of compound S6: Under N 2 protection, compound S5 (50 mg, 0.06 mmol), 4-pyridylphenylboronic acid (54 mg, 0.12 mmol), tetrakis(triphenylphosphine)palladium (Pd(PPh 3 ) 4 , 115 mg, 0.1 mmol), potassium carbonate (K 2 CO 3 ,1.03 g, 7.5 mmol) and 1,4-dioxane / water (10 mL, 5 / 1) were separately added to a 50 mL round-bottom flask. The mixture was stirred at 80 o °C for 24 h, then the reaction was cooled to room temperature, and the solvent was concentrated in vacuo to 5 mL. The crude product was obtained by filtration. The crude product was purified by column chromatography (silica gel, methanol / dichloromethane = 1 / 50) to obtain a blue-black solid with a yield of 61%.1 1H NMR (500 MHz, CDCl 3 ) δ / ppm 8.67 (d, J J = 5.0 Hz, 4H), 8.13 (d, J J = 5.0 Hz,4H), 7.70 (s, 4H), 7.64 (d, J J = 5.0Hz, 4H), 7.55 (d, J J = 5.0 Hz, 4H), 6.78 (s,2H) 3.31 (t, J J = 5.0 Hz, 8H), 2.78 (t, J J = 5.0 Hz, 8H), 2.01 (m, 8H). 13 13C NMR (126MHz, CDCl 3 ) δ / ppm 153.1, 150.2, 148.4, 148.2, 147.6, 143.5, 141.0, 138.1,135.9, 135.0, 134.9, 131.6, 130.3, 128.0, 127.5, 126.9, 121.8, 121.5, 121.3,121.1, 111.4, 51.4, 31.9, 30.2, 29.7, 27.9, 22.7, 22.1, 13.4. MALDI-TOF / MS:[M] + calcd: 841.3876, found: 841.7387.

[0071] Preparation of compound WS5: Under N 2 protection, S6 (50 mg, 0.06 mmol) and 1-bromododecane (9.9 mg,0.06 mmol) were added to a round-bottom flask containing chloroform (CHCl 3 , 10 mL), and stirred at 90 o °C for 24 h. The reaction was cooled to room temperature and the solvent was concentrated under vacuum. Finally, WS5 was obtained as a blue-green solid (yield 36%) by purification through column chromatography (silica gel, methanol / dichloromethane = 1 / 25). WS5: 1 1H NMR (500 MHz, d 6 d6-DMSO), δ / ppm 9.13 (d, J J = 10.0, 2H), 8.68 (m, 4H),8.27 (m, 6H), 7.96 (d, J= 10.0, 2H), 7.83 (s, 2H), 7.70 (d, J = 25.0, 4H), 7.23(d, J = 15.0, 2H), 4.58 (t, J = 10.0, 2H), 3.51 (s, 8H), 2.71 (s, 8H), 1.93 (s,10H), 1.27 (d, J = 30.0, 18H), 0.84 (t, J = 5.0, 3H). 13 C NMR (126 MHz, CDCl 3 ) δ / ppm 145.0, 130.6, 130.2, 129.3, 127.9, 127.1, 124.8, 121.4, 120.7, 114.6,77.2, 70.7, 50.4, 32.0, 31.6, 29.8, 29.7, 29.6, 29.5, 29.2, 28.2, 26.3, 22.8,21.8, 14.3. MALDI-TOF / MS: [M - 2Br] + calcd: 1011.149, found: 1011.055.

[0072] Preparation of WS5@NPs: Dissolve WS5 (1 mg) and DSPE-mPEG 5000 (5 mg) in tetrahydrofuran (1 mL), and ultrasonically mix evenly as the stock solution. Then inject the above stock solution into deionized water (9 mL) with a syringe and disperse it under a cell disruptor. After that, protect the solution with N 2 and stir it in a fume hood to evaporate tetrahydrofuran. Finally, filter and purify the generated nanoparticles (volume fixed to 1 mL) with a 0.45 μm ultrafiltration filter (Millipore). Finally, WS5@NPs with a concentration of 1 mg / mL are obtained.

[0073] Example 2

[0074] Step 1: Synthesis of Compound S1

[0075] Under ice-salt bath conditions, slowly drip phosphorus oxychloride (POCl 3 , 1.17 g, 7.62 mmol) into a 100 mL round-bottom flask containing dry N， N -dimethylformamide (DMF, 1.67 g, 22.87 mmol). Under N2 Under protection, stir for 2 h to obtain the Vilsmeier-Haack reagent. Then slowly add julolidine (1.20 g, 6.93 mmol) and dry DMF (10 mL) into the flask containing the Vilsmeier-Haack reagent. After that, stir at 30 o °C for 3 hours. After cooling to room temperature, pour the mixture into ice water (100 mL) to quench the reaction. Then, filter the precipitate to obtain a pale yellow solid. Finally, dry the solid in a vacuum drying oven overnight to obtain compound S1.

[0076] Step two: Synthesis of compound S2

[0077] Slowly add compound S1 (2.00 g, 10 mmol), 4-bromoacetophenone (2.00 g, 10 mmol) and aqueous sodium hydroxide solution (NaOH, 20%, 10 mL) into a 100 mL round-bottom flask containing ethanol (20 mL). Stir the mixture at room temperature (25 °C) for 24 hours, then pour the reacted mixed solution into ice water (100 mL) to quench the reaction. After stirring for another 2 hours, filter the precipitate to obtain a red solid. Subsequently, dry the red solid product in a vacuum drying oven overnight to obtain compound S2.

[0078] Step three: Synthesis of compound S3

[0079] Slowly add compound S2 (1.00 g, 5 mmol), nitromethane (1.00 mL) and N , N -diisopropylethylamine (DIPEA, 1.0 mL, 5.5 mmol) into a round-bottom flask containing methanol (CH 3 OH, 20 mL). After stirring at 60 o °C for 24 h, pour the reacted solution into a beaker containing saturated sodium chloride aqueous solution (10 mL) to stop the reaction, and then extract with ethyl acetate (30 mL). The obtained organic solution is dried with anhydrous sodium sulfate, filtered to obtain the crude product, and the crude product is purified by column chromatography (silica gel, ethyl acetate / petroleum ether = 1 / 10) to obtain a yellow solid.

[0080] Step four: Synthesis of compound S4

[0081] Add compound S3 (1.00 g, 1.0 mmol) and ammonium acetate (NH 4 OAc, 1.16 g, 15.0 mmol) into a 100 mL round-bottom flask containing n-butanol (n-BuOH, 20 mL), 100 oStir at C for 24 h, then cool to room temperature, and then concentrate in vacuo to 5 mL and filter by suction. The separated solid was washed with ethanol (2 × 5 mL), and finally a blue-black solid was obtained.

[0082] Step Five: Synthesis of Compound S5

[0083] Under the protection of N 2 Compound S4 (80 mg, 0.11 mmol) and DIPEA (0.2 mL, 1.1 mmol) were added to a 100 mL round-bottom flask containing dry dichloromethane (DCM, 20 mL). Then, BF 3 •Et 2 O (0.28 mL, 2.0 mmol) was slowly added dropwise to the solution, and the mixture was stirred in the dark at room temperature for 24 h, then diluted with ice water (20 mL) and extracted with DCM (3 × 20 mL). The organic solution was dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. The crude product was purified by column chromatography (silica gel, dichloromethane / petroleum ether = 1 / 1) to obtain a solid with metallic luster.

[0084] Step Six: Synthesis of Compound S6

[0085] Under the protection of N 2 Compound S5 (50 mg, 0.06 mmol), 4-pyridylphenylboronic acid (54 mg, 0.12 mmol), tetrakis(triphenylphosphine)palladium (Pd(PPh 3 ) 4 , 115 mg, 0.1 mmol), potassium carbonate (K 2 CO 3 , 1.03 g, 7.5 mmol) and 1,4-dioxane / water (10 mL, 5 / 1) were added to a 50 mL round-bottom flask respectively. The mixture was stirred at 70 o °C for 24 h, then the reaction was cooled to room temperature, the solvent was concentrated in vacuo to 5 mL, and the crude product was obtained by filtration. The crude product was purified by column chromatography (silica gel, methanol / dichloromethane = 1 / 50) to obtain a blue-black solid.

[0086] Step Seven: Synthesis of Compound WS5

[0087] Under the protection of N 2 S6 (50 mg, 0.06 mmol) and 1-bromododecane (9.9 mg, 0.06 mmol) were added to a round-bottom flask containing chloroform (CHCl 3 , 10 mL), and the mixture was heated at 80 oStir for 24 h, cool the reaction to room temperature, and concentrate the solvent under vacuum. Finally, purify to obtain the blue-green solid of WS5 by column chromatography (silica gel, methanol / dichloromethane = 1 / 25).

[0088] Step VIII: Synthesis of compound WS5@NPs

[0089] Dissolve WS5 (1 mg) and DSPE-mPEG 5000 (5 mg) in tetrahydrofuran (1 mL), ultrasonically mix evenly as the stock solution. Then inject the above stock solution into deionized water (9 mL) with a syringe and disperse it under a cell disruptor. After that, stir the solution under N 2 protection in a fume hood to evaporate the tetrahydrofuran. Finally, filter and purify with a 0.45 μm ultrafiltration filter (Millipore) to collect the generated nanoparticles (volume fixed to 1 mL). Finally, obtain WS5@NPs at 1 mg / mL.

[0090] Example 3

[0091] Step I: Synthesis of compound S1

[0092] Under ice-salt bath conditions, slowly drip phosphorus oxychloride (POCl 3 , 1.17 g, 7.62 mmol) into a 100 mL round-bottom flask containing dry N， N -dimethylformamide (DMF, 1.67 g, 22.87 mmol). Stir for 2 h under N 2 protection to obtain the Vilsmeier-Haack reagent. Then slowly add julolidine (1.20 g, 6.93 mmol) and dry DMF (10 mL) to the flask containing the Vilsmeier-Haack reagent. After that, stir at 25 o °C for 4 hours. After cooling to room temperature, pour the mixture into ice water (100 mL) to quench the reaction. Then, filter the precipitate to obtain a pale yellow solid. Finally, dry the solid in a vacuum drying oven overnight to obtain compound S1.

[0093] Step II: Synthesis of compound S2

[0094] Compound S1 (2.00 g, 10 mmol), 4-bromoacetophenone (2.00 g, 10 mmol) and aqueous sodium hydroxide solution (NaOH, 20%, 10 mL) were slowly added to a 100 mL round-bottom flask containing ethanol (20 mL). The mixture was stirred at room temperature for 24 h, then the reaction mixture was poured into ice water (100 mL) to quench the reaction. After stirring for another 2 h, the precipitate was filtered to obtain a red solid. Subsequently, the red solid product was dried in a vacuum drying oven overnight to obtain compound S2.

[0095] Step 3: Synthesis of compound S3

[0096] Compound S2 (1.00 g, 5 mmol), nitromethane (1.00 mL) and N , N -diisopropylethylamine (DIPEA, 1.0 mL, 5.5 mmol) were slowly added to a round-bottom flask containing methanol (CH 3 OH, 20 mL). After stirring at 65 o °C for 24 h, the reaction solution was poured into a beaker containing saturated sodium chloride aqueous solution (10 mL) to stop the reaction, and then extracted with ethyl acetate (30 mL). The obtained organic solution was dried over anhydrous sodium sulfate, filtered to obtain the crude product, and the crude product was purified by column chromatography (silica gel, ethyl acetate / petroleum ether = 1 / 10) to obtain a yellow solid.

[0097] Step 4: Synthesis of compound S4

[0098] Compound S3 (1.00 g, 1.0 mmol) and ammonium acetate (NH 4 OAc, 1.16 g, 15.0 mmol) were added to a 100 mL round-bottom flask containing n-butanol (n-BuOH, 20 mL). After stirring at 105 o °C for 24 h, it was cooled to room temperature, then concentrated in vacuo to 5 mL and filtered by suction. The separated solid was washed with ethanol (2 × 5 mL) to finally obtain a blue-black solid.

[0099] Step 5: Synthesis of compound S5

[0100] Under the protection of N 2 , compound S4 (80 mg, 0.11 mmol) and DIPEA (0.2 mL, 1.1 mmol) were added to a 100 mL round-bottom flask containing dry dichloromethane (DCM, 20 mL). Then, BF 3 •Et 2O (0.28 mL, 2.0 mmol) was slowly added dropwise into the solution, and the mixture was stirred in the dark at room temperature for 24 h. Then it was diluted with ice water (20 mL) and extracted with DCM (3 × 20 mL). The organic solution was dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. The crude product was purified by column chromatography (silica gel, dichloromethane / petroleum ether = 1 / 1) to obtain a solid with metallic luster.

[0101] Step VI: Synthesis of Compound S6

[0102] Under N 2 protection, compound S5 (50 mg, 0.06 mmol), 4-pyridylphenylboronic acid (54 mg, 0.12 mmol), tetrakis(triphenylphosphine)palladium (Pd(PPh 3 ) 4 , 115 mg, 0.1 mmol), potassium carbonate (K 2 CO 3 , 1.03 g, 7.5 mmol) and 1,4-dioxane / water (10 mL, 5 / 1) were respectively added into a 50 mL round-bottom flask. The mixture was stirred at 75 o °C for 24 h, then the reaction was cooled to room temperature, and the solvent was concentrated in vacuo to 5 mL. The crude product was obtained by filtration. The crude product was purified by column chromatography (silica gel, methanol / dichloromethane = 1 / 50) to obtain a blue-black solid.

[0103] Step VII: Synthesis of Compound WS5

[0104] Under N 2 protection, S6 (50 mg, 0.06 mmol) and 1-bromododecane (9.9 mg, 0.06 mmol) were added into a round-bottom flask containing chloroform (CHCl 3 , 10 mL). The mixture was stirred at 85 o °C for 24 h, and the reaction was cooled to room temperature. The solvent was concentrated in vacuo. Finally, the WS5 blue-green solid was obtained by purification through column chromatography (silica gel, methanol / dichloromethane = 1 / 25).

[0105] Step VIII: Synthesis of Compound WS5@NPs

[0106] WS5 (1 mg) and DSPE-mPEG 5000 (5 mg) were dissolved in tetrahydrofuran (1 mL), and the mixture was ultrasonically mixed uniformly as the stock solution. Then the above stock solution was injected into deionized water (9 mL) with a syringe and dispersed under a cell disruptor. After that, the solution was passed through N 2Protect by stirring in a fume hood to evaporate tetrahydrofuran. Finally, filter and purify the generated nanoparticles (volume fixed to 1 mL) with a 0.45 μm ultrafiltration filter (Millipore). Finally, WS5@NPs with a concentration of 1 mg / mL were obtained.

[0107] Figure 1 It is a schematic diagram for testing the basic photophysical properties of WS5 molecules. As Figure 1 shown in (a) of Figure 1 shown in (b) of Figure 1 shown in (c) of Figure 1 and shown in (d) of the photothermal performance test of WS5 molecules (0.2 mg mL -1 , 0.23 W cm -2 , 1064 nm). The photophysical properties of WS5 molecules indicate that its molar extinction coefficient, fluorescence brightness, and photothermal performance are relatively high. Due to the introduction of the side chain structure, the electron-withdrawing ability of the acceptor is enhanced, thereby enhancing the push-pull ability of electrons within the molecule and the delocalization ability of electrons, manifested as the main absorption and emission peaks of WS5 molecules exceeding 1000 nm. It is found that the introduction of flexible side chains enhances molecular motion and promotes the non-radiative decay process.

[0108] As Figure 2 shown, compared with the photophysical properties of organic molecules, the photophysical properties of nanoparticles have changed significantly, especially fluorescence and photothermal properties. From the results of photophysical tests, the absorption spectrum of nanoparticles is significantly broadened compared to that of organic molecules, indicating the coexistence of multiple aggregation states. Compared with the absorption spectrum of organic molecules, the absorption spectrum of nanoparticles has a slight blue shift, indicating the Coulomb coupling effect of molecules in the coated nanoparticles. The results of photophysical tests show that the introduction of a suitable side chain structure, H-aggregation, and extended intermolecular distance can promote intramolecular motion and enhance photothermal performance, and π-π stacking also decreases with the extended intermolecular distance, thereby promoting fluorescence in the aggregated state. Therefore, a NIR-II photothermal agent with high brightness and high photothermal performance is obtained.

[0109] As Figure 3 shown, in vitro cell experiments confirmed that WS5@NPs have a tumor-killing mechanism of light-induced thermal effect. Different concentrations of WS5@NPs were selected for cell viability experiments. After 5 minutes of laser irradiation at 1064 nm (0.23 W cm -2), the tumor cells undergo rapid death. Especially at concentrations of 50 μg / mL and 100 μg / mL, rapid cell death can be observed. However, in the absence of laser irradiation, the viability of the tumor cells hardly decreases, indicating that the material has excellent safety and a photothermal effect that induces tumor cell death. Meanwhile, WS5@NPs can effectively induce apoptosis in 143B cells under excitation at 1064 nm. In the laser-treated group after administration, the proportion of necrotic cells is only 5.85%, while the total number of early apoptotic and late apoptotic cells is as high as 76.02%. These results indicate that WS5@NPs induce apoptosis in cells under laser irradiation, thus achieving autonomous programmed cell death.

[0110] As Figure 4 shown, in vivo fluorescence imaging in the NIR-IIa region shows that WS5@NPs can rapidly illuminate the blood vessels and lymphatic system of mice within 5 minutes, showing high imaging resolution.

[0111] As Figure 5 shown, under the guidance of NIR-II imaging, 24 hours after intravenous administration, deep tumor photothermal therapy was performed on tumor-bearing mice, and its efficacy was evaluated. Compared with the control group, the temperature in the administration group increased significantly under laser irradiation and could reach 44 o °C in 3 minutes, and the highest temperature was 46 o °C. No obvious recurrence of the tumors in the mice was observed after the treatment was stopped. During the whole treatment process, the skin at the irradiated site was not significantly burned, showing the outstanding advantages of the high-efficiency photothermal performance of the material in deep tumor treatment.

[0112] The present invention not only discloses the deep tumor treatment under the guidance of NIR-II imaging using a photothermal agent with high brightness and high photothermal performance, but also reveals the dual-enhancing mechanism of the side chain in improving the molecular brightness and photothermal performance. Side chain engineering can be used as an effective method to simultaneously regulate the radiative transition (QY) and non-radiative transition (PCE) processes. Specifically, the introduction of the side chain promotes the intramolecular motion of the aggregated state by further twisting the molecular conformation, extending the intermolecular distance and providing a looser packing environment for intramolecular motion (a too large side chain will cause a large steric hindrance in the aggregated state), thereby promoting non-radiative transition to generate photothermal properties. In addition, although the intramolecular motion is promoted with the assistance of the side chain, the π-π stacking also decreases with the extended intermolecular distance, thus promoting fluorescence in the aggregated state. Therefore, the introduction of the alkyl chain enhances both fluorescence and photothermal properties, and can be used for photothermal therapy under fluorescence guidance, providing a new idea for solving the problem that depends on two competing photophysical processes.

[0113] The above content is only for explaining the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution in accordance with the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A high-brightness NIR-II region photothermal agent based on Aza-BODIPY, Characterized in that, The structural formula of the photothermal agent is as follows:

2. A preparation method of the high-brightness NIR-II region photothermal agent based on Aza-BODIPY according to claim 1, Characterized in that, It includes the following steps: Step 1: Add N,N-dimethylformamide to phosphorus oxychloride and stir under a protective gas to obtain a Vilsmeier-Haack reagent; mix julolidine with N,N-dimethylformamide and then add it to the Vilsmeier-Haack reagent, and then raise the temperature for the first reaction. After the first reaction is completed, cool to room temperature and pour the mixture into ice water to quench the reaction, and then filter and dry to obtain an intermediate product S1; the structural formula of the intermediate product S1 is as follows: Step 2: Mix the intermediate S1, 4-bromoacetophenone, aqueous sodium hydroxide solution, and ethanol uniformly for the second reaction. After the second reaction is completed, pour the mixed solution of the second reaction product into ice water to quench the reaction, and then filter and dry to obtain the intermediate S2; the structural formula of the intermediate S2 is as follows: Step 3: Mix the intermediate S2, nitromethane, N,N-diisopropylethylamine, and methanol evenly, then heat up for the third reaction. Pour the solution of the third reaction product into a saturated sodium chloride aqueous solution to stop the reaction, and then extract, dry, filter, and purify to obtain the intermediate S3; the structural formula of the intermediate S3 is as follows: Step Four: Mix the intermediate S3, ammonium acetate and n-butanol evenly, heat up for the fourth reaction, then concentrate under vacuum and filter, separate the solid and wash it to obtain the intermediate S4; The structural formula of the intermediate S4 is as follows: Step 5: Mix the intermediate S4, N,N-diisopropylethylamine with dry dichloromethane, add boron trifluoride diethyl etherate, and carry out the fifth reaction by stirring in the dark at room temperature. Dilute the product of the fifth reaction with ice water, extract, dry, filter, concentrate, and purify to obtain the intermediate S5; the structural formula of the intermediate S5 is as follows: Step 6: Under a protective gas, mix the intermediate S5, 4-pyridylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and a solution of potassium carbonate, 1,4-dioxane and water, heat up for the sixth reaction, cool to room temperature after the sixth reaction is completed, and then concentrate, filter and purify to obtain intermediate S6; The structural formula of intermediate S6 is as follows: Step Seven: Under a protective gas, mix the intermediate S6 with 1-bromododecane and chloroform, heat up for the seventh reaction, after the seventh reaction is completed, cool to room temperature, then concentrate, filter and purify to obtain WS5; The structural formula of WS5 is as follows:

3. According to the preparation method described in claim 2, Characterized in that, In the said Step One, the molar ratio of phosphorus oxychloride, N,N-dimethylformamide to julolidine is 7.62:22.87:6.93 mmol; The temperature of the first reaction is 20 - 30 °C; The time of the first reaction is 3 - 4 h.

4. According to the preparation method described in claim 2, Characterized in that, In the said Step Two, the molar ratio of the intermediate S1 to 4-bromoacetophenone is 1:1; The temperature of the second reaction is 25 - 30 °C.

5. According to the preparation method described in claim 2, Characterized in that, In the said Step Three, the molar ratio of the intermediate S2 to N,N-diisopropylethylamine is 5:5.5; The temperature of the third reaction is 60 - 70 °C.

6. According to the preparation method described in claim 2, Characterized in that, In the said Step Four, the molar ratio of the intermediate S3 to ammonium acetate is 1:15; The temperature of the fourth reaction is 100 - 110 °C.

7. According to the preparation method described in claim 2, Characterized in that, In the said Step Five, the molar ratio of the intermediate S4, N,N-diisopropylethylamine to boron trifluoride diethyl etherate is 0.11:1.1:

2.

8. According to the preparation method described in claim 2, Characterized in that, In the said Step Six, the molar ratio of the intermediate S5, 4-pyridylphenylboronic acid, tetrakis(triphenylphosphine)palladium and potassium carbonate is 0.06:0.12:0.1:7.5; The temperature of the sixth reaction is 70 - 80 °C; The volume ratio of 1,4-dioxane to water is 5:

1.

9. According to the preparation method described in claim 2, Characterized in that, In the said Step Seven, the molar ratio of the intermediate S6 to 1-bromododecane is 1:1; The temperature of the seventh reaction is 80 - 90 °C.

10. An application of the high-brightness NIR-II region photothermal agent according to claim 1 in the preparation of photothermal therapy drugs.

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