Tea polyphenol-derived carbon dots, preparation method, and application in the preparation of antidepressants

Abstract

The present invention discloses a tea polyphenol-derived carbon dot, a preparation method thereof, and its application in the preparation of an antidepressant, comprising the following steps: tea polyphenol and fluoxetine hydrochloride are used as reaction raw materials, subjected to microwave heating reaction, dissolved in water after the reaction is complete, then filtered, dialyzed, and freeze-dried to obtain the tea polyphenol-derived carbon dot. The raw material used in the present invention is the natural product tea polyphenol. The prepared carbon dots have good fluorescence properties, rich surface groups, low toxicity, and are easily cleared by the kidneys. Cell models and zebrafish animal models have shown that the M-CDs prepared by the present invention have good biosafety and can significantly improve the depressive-like behavior of zebrafish, restoring the zebrafish's cortisol and monoamine neurotransmitters to normal levels. The M-CDs prepared by the present invention have good water solubility and are expected to be used as a new antidepressant for further application research.

Description

Technical Field

[0001] The present invention relates to tea polyphenol-derived carbon dots, a preparation method thereof, and application thereof in the preparation of antidepressants, belonging to the technical field of preparation and application of nanomaterials. Background Art

[0002] The onset of depression is influenced by the interaction of multiple factors, such as mental stress, family genetics, social environment, and physical activity. Clinical symptoms include significantly low mood, lack of interest in things, slowed thinking and cognitive function, and accompanied by psychiatric symptoms such as hallucinations and delusions, which have a great impact on the patient's daily life. What's more serious is that the onset of depression is usually accompanied by other diseases. Through a large number of association studies, researchers have found that depression not only increases the risk of patients contracting other diseases, but also worsens their condition and even leads to death. Surveys of multiple clinical samples have shown that depression greatly increases the risk of chronic diseases, including cancer, cardiovascular disease, inflammation, Parkinson's syndrome, etc. Therefore, finding active and effective methods to treat depression is of great significance to social development.

[0003] Tea polyphenols, the main active ingredient in tea, have been shown to prevent or treat depression and anxiety. However, tea polyphenols have low bioavailability, with only a small portion being absorbed by the human body. Furthermore, they are also unstable and susceptible to oxidative degradation, limiting their use as antidepressants. Fluoxetine, a commonly used SSRI antidepressant, selectively inhibits the 5-hydroxytryptamine (5-HT) transporter and blocks the reuptake of 5-HT by the presynaptic membrane, thereby prolonging the duration of 5-HT action and producing an antidepressant effect. However, fluoxetine has significant side effects. For example, a patent for an antidepressant drug and its use (CN117679431A) indicates that fluoxetine treatment causes adverse reactions such as gastrointestinal disturbances and erectile dysfunction in depression model animals, limiting its further application in depression.

[0004] Carbon dots (Cdots) are a class of carbon nanoparticles smaller than 10 nanometers in size. They possess excellent physical and chemical properties, a rich array of surface groups, and are easily functionalized. This study designed and synthesized tea polyphenol-derived Cdots (M-CDs), which exhibit anti-anxiety and anti-depressant effects while retaining the excellent fluorescence properties of Cdots. Therefore, M-CDs demonstrate significant potential for application in the development of antidepressant drugs. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides a tea polyphenol-derived carbon dot, which has good biosafety, excellent fluorescence properties, and antidepressant efficacy, making it expected to be used in the treatment of depression.

[0006] The present invention also provides a preparation method of the tea polyphenols-derived carbon dots and application thereof in the preparation of antidepressants.

[0007] In order to achieve the above-mentioned object, the present invention adopts a method for preparing tea polyphenol-derived carbon dots, comprising the following steps: tea polyphenol and fluoxetine hydrochloride are used as reaction raw materials, subjected to microwave heating reaction, dissolved in water after the reaction is complete, then filtered, dialyzed, and freeze-dried to obtain the tea polyphenol-derived carbon dots.

[0008] As an improvement, the mass ratio of the tea polyphenols to fluoxetine hydrochloride is 0.5-1:0.5-1.

[0009] As an improvement, the tea polyphenols and fluoxetine hydrochloride are dissolved in ultrapure water and then ultrasonicated and subjected to microwave heating reaction.

[0010] As an improvement, the microwave heating power used is 400-500 watts, the temperature is 95-99 degrees Celsius, and the time is 5-10 minutes.

[0011] As an improvement, the filtration is performed using a 0.22 micron water filter membrane, the cellulose dialysis bag has a molecular weight cutoff of 500-1000 Daltons, the dialysis time is 72-96 hours, and the freeze-drying time is 48-72 hours.

[0012] As a preferred technical solution, the method for preparing tea polyphenol-derived carbon dots according to the present invention may include the following steps:

[0013] 1) Weigh 0.5-1 g of tea polyphenols and 0.5-1 g of fluoxetine hydrochloride, dissolve in 30-40 ml of ultrapure water, sonicate until homogenized, and transfer to a microwave oven;

[0014] 2) Set the microwave power to 400-500 watts and the temperature to 95-99 degrees Celsius for 5-10 minutes to completely carbonize the reactants. After cooling to room temperature, a brown solid is obtained. Add an appropriate amount of ultrapure water to the cooled beaker and sonicate to fully dissolve it.

[0015] 3) The ultrasonically dissolved solution is filtered 1-4 times through a 0.22 μm water filter membrane. The filtered liquid is collected and placed into a cellulose dialysis bag with a molecular weight cutoff of 500-1000 Daltons. The filtered liquid is dialyzed in ultrapure water for 1-4 days. After the dialysis is completed, the dialysate is collected and freeze-dried for 48-72 hours to obtain a dark brown solid powder, which is the tea polyphenol-derived carbon dots M-CDs.

[0016] In addition, the present invention also provides tea polyphenol-derived carbon dots, which are prepared by the preparation method and are water-soluble.

[0017] Finally, the present invention also provides an application of tea polyphenol-derived carbon dots in the preparation of antidepressants, using the tea polyphenol-derived carbon dots.

[0018] As an improvement, the antidepressant is a drug for treating depression caused by neurasthenia.

[0019] Mechanism of the present invention:

[0020] The present invention uses tea polyphenols and fluoxetine hydrochloride as raw materials for a reaction. Tea polyphenols are carbonized at high temperature to form a carbon core. Fluoxetine hydrochloride then reacts with the tea polyphenols to form a covalent bond directly attached to the surface of the carbon core, thereby producing tea polyphenol-derived carbon dots (M-CDs) with a fluorine-rich surface. The inventors discovered that using fluoxetine hydrochloride alone under the same reaction temperature conditions would not produce carbon dots. Therefore, the present invention uses tea polyphenols and fluoxetine hydrochloride as raw materials, and through a chemical reaction and core-shell synergy, produces tea polyphenol-derived carbon dots. Their small size (typically between 1 and 10 nanometers) allows for easy renal clearance and very low in vivo residue, effectively reducing biotoxicity. These tea polyphenol-derived carbon dots primarily regulate levels of neurotransmitters such as serotonin and cortisol, improving neurotransmitter imbalance and preventing and treating depression.

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

[0022] 1) The raw material used in the present invention is the natural product tea polyphenols. The prepared carbon dots have good fluorescence properties, rich surface groups, low toxicity, and are easily cleared by the kidneys.

[0023] 2) Through cell models and zebrafish animal models, it was found that the M-CDs prepared by the present invention have good biosafety and can significantly improve the depressive-like behavior of zebrafish and restore the cortisol and monoamine neurotransmitters of zebrafish to normal levels.

[0024] 3) The M-CDs prepared by the present invention have good water solubility and are expected to be used as new antidepressants for further application research. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Transmission electron microscopy (inset is the particle size distribution histogram) and high-resolution transmission electron microscopy images of M-CDs prepared in Example 1;

[0026] Figure 2 The UV-visible absorption spectrum and excitation-dependent spectrum of M-CDs prepared in Example 1;

[0027] Figure 3 Effects of M-CDs prepared in Example 1 on the behavior of zebrafish in the novel tank test (NTT);

[0028] Figure 4 The effects of M-CDs prepared in Example 1 on the behavior of zebrafish in the light-dark tank test (LDB);

[0029] Figure 5 To measure the levels of cortisol, dopamine (DA) and 5-hydroxytryptamine (5-HT) in zebrafish;

[0030] Figure 6 The CCK-8 results of HepG2 cells co-incubated with different concentrations of M-CDs and the survival rate, body length and heart rate of zebrafish embryos treated with different concentrations of M-CDs 96 hours after fertilization. DETAILED DESCRIPTION

[0031] The following embodiments are further descriptions of the present invention to illustrate the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0032] Example 1

[0033] A method for preparing tea polyphenols-derived carbon dots comprises the following steps:

[0034] 1) Weigh 0.92 g of tea polyphenols and 0.7 g of fluoxetine hydrochloride, dissolve in 35 ml of ultrapure water, sonicate until homogenized, and transfer to a microwave oven;

[0035] 2) Set the microwave power to 500 watts and the temperature to 96 degrees Celsius for 6 minutes to completely carbonize the reactants. After cooling to room temperature, a brown solid was obtained. Add an appropriate amount of ultrapure water to the cooled beaker and sonicate to fully dissolve it.

[0036] 3) The ultrasonically dissolved solution was filtered three times through a 0.22 μm water filter membrane. The filtered liquid was collected and placed into a cellulose dialysis bag with a molecular weight cutoff of 500-1000 Daltons. The solution was dialyzed in ultrapure water for three days. After the dialysis, the dialysate was collected and freeze-dried for 48 hours to obtain a dark brown solid powder of carbon dots (M-CDs), which was then sealed and stored.

[0037] The performance of the tea polyphenols-derived carbon dots prepared in Example 1 was analyzed, and the results are as follows: Figure 1 、 Figure 2 shown.

[0038] Figure 1 Transmission electron microscopy (TEM) and high-resolution TEM images of M-CDs (the inset is the particle size distribution histogram), showing that M-CDs are spherical with good monodispersity and high crystallinity. Figure 1 (a) Transmission electron micrograph and particle size histogram (inset) of M-CDs, showing spherical and uniform particle size ranging from 1.5 to 4.5 nm, with an average size of 3.5 ± 0.1 nm. This small size gives them good biocompatibility and biosafety. Figure 1 (b) is a high-resolution transmission electron microscopy image of M-CDs, with lattice spacings corresponding to 0.218 and 0.271 nm, respectively, corresponding to the (100) crystal plane of graphitic carbon.

[0039] Figure 2 The UV-visible absorption spectra and excitation-dependent spectra of M-CDs show that M-CDs have excellent optical properties and are convenient for biological imaging. Figure 2 (a) UV-visible absorption spectrum, optimal excitation spectrum, and optimal emission spectrum of M-CDs. The optimal excitation wavelength is 365 nm, and the emission wavelength is 455 nm. Figure 2 (b) is the excitation-dependent spectrum of M-CDs. Under the excitation wavelength of 365 to 405 nm, M-CDs showed obvious excitation wavelength dependence, which may be because M-CDs have non-single luminescence center.

[0040] Example 2

[0041] A method for preparing tea polyphenols-derived carbon dots comprises the following steps:

[0042] 1) Weigh 0.9 g of tea polyphenols and 0.75 g of fluoxetine hydrochloride, dissolve in 35 ml of ultrapure water, sonicate until homogenized, and transfer to a microwave oven;

[0043] 2) Set the microwave power to 500 watts and the temperature to 99 degrees Celsius for 7 minutes to completely carbonize the reactants. After cooling to room temperature, a brown solid was obtained. Add an appropriate amount of ultrapure water to the cooled beaker and sonicate to fully dissolve it.

[0044] 3) The ultrasonically dissolved solution was filtered three times through a 0.22 μm water filter membrane. The filtered liquid was collected and placed into a cellulose dialysis bag with a molecular weight cutoff of 500-1000 Daltons. The solution was dialyzed in ultrapure water for three days. After the dialysis, the dialysate was collected and freeze-dried for 50 hours to obtain a dark brown solid powder of carbon dots (M-CDs), which was then sealed and stored.

[0045] Example 3

[0046] A method for preparing tea polyphenols-derived carbon dots comprises the following steps:

[0047] 1) Weigh 0.95 g of tea polyphenols and 0.72 g of fluoxetine hydrochloride, dissolve in 40 ml of ultrapure water, sonicate until homogenized, and transfer to a microwave oven;

[0048] 2) Set the microwave power to 400 watts and the temperature to 95 degrees Celsius for 8 minutes to completely carbonize the reactants. After cooling to room temperature, a brown solid was obtained. Add an appropriate amount of ultrapure water to the cooled beaker and sonicate to fully dissolve it.

[0049] 3) The ultrasonically dissolved solution was filtered three times through a 0.22 μm water filter membrane. The filtered liquid was collected and placed into a cellulose dialysis bag with a molecular weight cutoff of 500-1000 Daltons. The solution was dialyzed in ultrapure water for three days. After the dialysis, the dialysate was collected and freeze-dried for 60 hours to obtain a dark brown solid powder of carbon dots (M-CDs), which was then sealed and stored.

[0050] Example 4

[0051] Taking the tea polyphenols-derived carbon dots (M-CDs) prepared in Example 1 as an example, the application performance analysis was performed as follows:

[0052] ①Build a model

[0053] Based on the experience of previous studies, reserpine was selected as the zebrafish depressant at a concentration of 40 micrograms per milliliter. The preparation method was to add the dry powder directly to the system water after weighing, and ultrasonicate for 5 minutes to promote uniform mixing of the powder. Adult zebrafish were exposed to 40 micrograms per milliliter of reserpine for 20 minutes to make the zebrafish depressed (defined as acute depression). After treatment, the model was established.

[0054] ② Experimental test grouping

[0055] CG group: blank control group;

[0056] Acute group: treated with 40 μg / mL of reserpine for 20 minutes;

[0057] Model group (MG): zebrafish were treated with reserpine and then treated with system water for 3 days to establish a depression model;

[0058] Fluoxetine hydrochloride treatment group (Fluoxetine): zebrafish were treated with reserpine and then treated with fluoxetine hydrochloride (0.1 μg / mL) for 3 days;

[0059] M-CDs treatment group: zebrafish were treated with reserpine and then treated with M-CDs (200 μg / ml) for 3 days;

[0060] Each group consisted of 10 zebrafish, which were cultured independently in 2-liter water tanks. The culture medium was replaced after the zebrafish were fed every day, and the water temperature was 28 degrees Celsius.

[0061] ③ Noval tank test (NTT) on the effects of M-CDs on zebrafish

[0062] Before the NTT test, adult zebrafish should be fasted. On the day of the test, adult zebrafish should be placed in a quiet environment and allowed to adapt to the new environment for at least 60 minutes. NTT behavioral assessment should be completed between 9:00 and 18:00.

[0063] During the test, the zebrafish of the corresponding test group were placed in a transparent rectangular water tank made of plexiglass (23 cm long × 15 cm wide × 15 cm high). The midline position outside the water tank was marked with a dotted line to divide the water tank into two equal parts, the top of the new water tank was above the midline, and the bottom of the new water tank was below the midline.

[0064] A 5-minute video of the zebrafish's movements in the tank was recorded from the front using a computer. After recording, two trained experimenters were selected to statistically summarize and organize the zebrafish's movements in the recorded video without knowing the experimental group. The results are shown in Figure 3 .

[0065] Figure 3 The effects of M-CDs on zebrafish novel tank test (NTT) behavior are shown, demonstrating their ability to treat reserpine-induced depressive-like behaviors in zebrafish. Three minutes after acute reserpine treatment, no significant changes in exploratory behavior were observed in zebrafish. However, after three days of continued treatment with system water, exploratory behavior decreased significantly, and freezing and rigidity occurred, demonstrating successful establishment of a zebrafish depression model. Figures ac and c show the time spent at the top of the NTT tank, the number of times the zebrafish entered the top, and the duration of freezing and rigidity in the different test groups. Zebrafish in the MG group were treated with 0.1 μg / mL fluoxetine hydrochloride and 200 μg / mL M-CDs, respectively, to investigate the therapeutic effects of M-CDs on MG zebrafish. The results showed that treatment with 0.1 micrograms per milliliter of fluoxetine hydrochloride could significantly improve the top exploration behavior of zebrafish, basically restoring it to normal levels, while 200 micrograms per milliliter of M-CDs and 0.1 micrograms per milliliter of fluoxetine hydrochloride had comparable therapeutic effects, effectively reversing the depressive-like behavior of zebrafish caused by reserpine.

[0066] ④M-CDs affect the light-dark box test (LDB) of zebrafish

[0067] Before the LDB test, adult zebrafish were fasted. On the day of the test, adult zebrafish were placed in a quiet environment and allowed to acclimate to the new environment for at least 60 minutes. The LDB behavioral assessment should be completed between 9:00 and 18:00.

[0068] The zebrafish were placed in a rectangular tank (31 cm long, 10 cm wide, and 15 cm high) divided into two equal sections: a dark compartment and a light compartment. When introduced to a new environment, zebrafish prefer the dark compartment and avoid the bright area.

[0069] Use an external camera connected to a computer to record a 5-minute video of the zebrafish's movements in the tank from the front. After recording, two trained experimenters were selected to statistically summarize and organize the zebrafish's movement behaviors in the recorded video without knowing the experimental group. Figure 4 .

[0070] Figure 4 The effect of M-CDs on zebrafish light-dark tank (LDB) behavior was shown. In the LDB test, the MG group significantly reduced the time spent in the light tank and the number of entries compared to the CG group, indicating successful modeling with reserpine and consistent with the results of the NTT test. The left figure (a) shows the time zebrafish spent in the light tank, and the right figure (b) shows the number of entries. The results showed that treatment of the MG group with 0.1 μg / mL fluoxetine hydrochloride and 200 μg / mL M-CDs improved their light exploration behavior, essentially returning it to the level of the normal group. The treatment also significantly increased the time zebrafish spent in the light tank and the number of entries. The NTT and LDB tests preliminarily indicate that M-CDs can reverse the depressive-like behavior of zebrafish induced by reserpine.

[0071] ⑤M-CDs affect the levels of cortisol, dopamine (DA), and 5-hydroxytryptamine (5-HT) in zebrafish

[0072] S1. Prepare 2 μg / mL reserpine culture medium using E3 culture medium for later use.

[0073] S2. Incubate zebrafish eggs in a six-well plate, with 30 embryos per well, and treat with the above-prepared reserpine culture medium for 6 hours;

[0074] S3. After the treatment, the fish were washed with E3 medium and incubated with E3 medium for 2 days. At this time, the zebrafish larvae model was completed.

[0075] S4. The zebrafish larvae treated with reserpine were then treated with 0.1 μg / mL fluoxetine hydrochloride and 200 μg / mL M-CDs (prepared in Example 1) for 3 days;

[0076] S5. After treatment, wash with PBS (pH 7.2-7.4) for more than 3 times and set aside;

[0077] S6, test group, 20 juveniles per group, cleaned juveniles were homogenized in 500 μl of normal saline using a tissue homogenizer;

[0078] S7. After homogenization, the homogenate was centrifuged at 28,000 rpm for 5 minutes at 4 degrees Celsius. The supernatant was collected and stored in a -80 degree Celsius freezer.

[0079] S8. The levels of cortisol, 5-HT, and DA in zebrafish larvae incubated for 6 days were tested using a commercially available ELISA kit. The entire experimental process was carried out strictly in accordance with the kit instructions. Figure 5 shown.

[0080] Figure 5 To determine the levels of cortisol, DA and 5-HT in zebrafish. Figure 5 (a) Cortisol levels in zebrafish. Compared to the CG group, systemic cortisol levels in zebrafish in the MG group were significantly elevated, possibly due to a dysfunctional HPI axis in the MG group. After treatment with 200 μg / mL M-CDs and 0.1 μg / mL fluoxetine hydrochloride, systemic cortisol levels in zebrafish in the MG group significantly decreased, returning to normal levels. Figure 5 (b) and (c) show DA and 5-HT measurements in zebrafish, demonstrating that M-CDs can effectively restore DA and 5-HT levels in zebrafish treated with MG. Compared with the CG group, 5-HT and DA levels in zebrafish treated with MG were significantly reduced, indicating that reserpine treatment causes a sharp drop in neurotransmitter levels in zebrafish. However, M-CDs can treat the severe neurotransmitter depletion caused by reserpine. This condition was significantly improved when 200 μg / mL of M-CDs was used, and the therapeutic effect of M-CDs was comparable to that of 0.1 μg / mL of fluoxetine hydrochloride. This is consistent with the behavioral test results, indicating that M-CDs are promising for further research as antidepressants.

[0081] Example 5

[0082] Taking the tea polyphenols-derived carbon dots (M-CDs) prepared in Example 1 as an example, the application performance analysis was performed as follows:

[0083] ① Cytotoxicity experiment of M-CDs

[0084] 1) QSG7701 cells were seeded into a 96-well culture plate and cultured in a 5% CO2 environment for 12 hours. The culture medium was aspirated and set aside.

[0085] 2) Add 0, 50, 100, 150, 200, 250, or 300 μg / mL of M-CDs solution diluted with culture medium to each well and continue culturing for 24 hours;

[0086] 3) Add 110 μL of CCK-8 / DMEM (volume ratio 1:10) mixed solution to each well in the dark and continue incubation for 1 hour;

[0087] 4) Finally, use a microplate reader to measure the absorbance at 450 nm;

[0088] 5) For the above experiment, 6 replicate wells were set up in each 96-well plate at each sample concentration, and the experiment was repeated three times.

[0089] ② Zebrafish toxicity experiment

[0090] 1) One day before spawning, zebrafish with active vital signs were selected in a strict ratio of male to female = 2:1 and placed in a breeding tank overnight, separated by partitions;

[0091] 2) The next morning, remove the baffle and begin spawning. Spawning is complete approximately 2 hours later, and the embryos are collected and rinsed with embryo incubation buffer (Holt Buffer: 3.5 g sodium chloride, 0.05 g potassium chloride, 0.1 g calcium chloride, and 0.1 g sodium bicarbonate dissolved in 1 liter of deionized water, plus 1 ml of 1 / 1000 methylene blue solution).

[0092] 3) Dilute M-CDs to different concentrations (0, 50, 100, 150, 200, 250 μg / ml) in incubation solution for later use;

[0093] 4) Zebrafish embryos 1.5 hours after fertilization were exposed to incubation medium containing different concentrations of M-CDs and cultured. A blank control group was only exposed to incubation medium and placed in a constant temperature incubator.

[0094] 5) Replace half of the embryo incubation solution in the well every 24 hours and remove dead embryos and juveniles in a timely manner to avoid contamination;

[0095] 6) After 96 hours of continuous incubation, 6 juveniles were randomly selected from each well and observed and measured under an inverted fluorescence microscope. The distance from the head to the end of the tail of the zebrafish was repeated three times.

[0096] 7) Randomly select 6 juvenile zebrafish from each well and record the number of heartbeats of the zebrafish juveniles within 20 seconds. Repeat three times. Figure 6 shown.

[0097] Figure 6The results of CCK-8 incubation of HepG2 cells with different concentrations of M-CDs and the survival rate, body length and heart rate of zebrafish embryos 96 hours after fertilization treated with different concentrations of M-CDs; Figure 6 (a) The cytotoxicity of M-CDs was analyzed by the classic CCK-8 assay. It can be clearly seen that even at a high concentration of 300 μg / mL, the cell survival rate remained around 80%, demonstrating that M-CDs have minimal cytotoxicity. Figure 6 (b)-(d) show the survival rate, body length, and heart rate of zebrafish embryos treated with different concentrations of M-CDs 96 hours after fertilization. M-CDs exhibit good in vivo biosafety. These results demonstrate that M-CDs have excellent in vivo and in vitro biosafety.

[0098] It should be noted that the above embodiments are merely general examples for verifying the technical content of the present invention, and it cannot be simply assumed that the present invention is limited to the above embodiments. The substantive protection scope of the present invention shall be based on the claims. Those skilled in the art should know that any modifications, equivalent substitutions, and improvements based on the substantive spirit of the present invention shall be within the substantive protection scope of the present invention.

Claims

1. A method for preparing tea polyphenols-derived carbon dots, characterized in that: The following steps are involved: 1) Weigh 0.5-1 g of tea polyphenols and 0.5-1 g of fluoxetine hydrochloride, dissolve in 30-40 ml of ultrapure water, sonicate until homogenized, and transfer to a microwave oven; 2) Set the microwave power to 400-500 watts and the temperature to 95-99 degrees Celsius for 5-10 minutes to completely carbonize the reactants. After cooling to room temperature, a brown solid is obtained. Add an appropriate amount of ultrapure water to the cooled beaker and sonicate to fully dissolve it. 3) The ultrasonically dissolved solution is filtered 1-4 times through a 0.22 μm water filter membrane. The filtered liquid is collected and placed into a cellulose dialysis bag with a molecular weight cutoff of 500-1000 Daltons. The filtered liquid is dialyzed in ultrapure water for 1-4 days. After the dialysis is completed, the dialysate is collected and freeze-dried for 48-72 hours to obtain a dark brown solid powder, which is the tea polyphenol-derived carbon dots M-CDs.

2. A tea polyphenol-derived carbon dot, characterized in that: Prepared by the preparation method of claim 1, the tea polyphenol-derived carbon dots are water-soluble.

3. A use of tea polyphenols-derived carbon dots in the preparation of antidepressants, characterized in that: The tea polyphenols-derived carbon dots according to claim 2 are used.

4. The use of tea polyphenols-derived carbon dots in the preparation of antidepressants according to claim 3, characterized in that: The antidepressant is a drug for treating depression caused by neurasthenia.

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