Citric acid series carbon dots and their application in the preparation of calcium crystal inhibitors

Abstract

The present invention discloses a class of citric acid series carbon dots and their application in the preparation of calcium crystal inhibitors. The citric acid series carbon dots are carbon dots obtained by chemically synthesizing citric acid series substances. The citric acid series carbon dots of the present invention have the advantages of good water solubility, good stability, low biological toxicity, and renal clearance. Therefore, they can replace common organic small molecule acids with poor stability, high biological toxicity, and difficult metabolism to regulate the crystallization process of calcium oxalate crystals. Such carbon dots can not only promote the transformation of calcium oxalate monohydrate crystals into calcium oxalate dihydrate crystals that are easier to excrete from the body, but also inhibit the growth of calcium oxalate crystals, reducing their average crystal grain size by 20%. At the same time, through the renal clearance mechanism of carbon dots, the fluorescence in urine can be used to study their metabolism in the body. Such carbon dots show great application potential in the treatment of calcium oxalate stones.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation and application of nanomaterials, and specifically relates to citric acid series carbon dots and their application in influencing the crystallization of calcium oxalate crystals. Background Art

[0002] The incidence of urolithiasis is high, and it is prone to recurrence after treatment (the recurrence rate within ten years is as high as 50%), making it difficult to prevent and treat. It has become a common and frequently-occurring disease threatening human health. Calcium oxalate is a common component in urinary system stones, accounting for about 70% of the causes of urolithiasis. Among them, calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), and calcium oxalate trihydrate (COT) are the main forms of calcium oxalate crystals. Among these three crystal forms, COM has the highest thermodynamic stability, and the surface of COM crystals is positively charged, with the strongest adhesion ability to damaged renal epithelial cells with negative charges and the strongest pathogenicity. In contrast, COD crystals with nearly neutral surface charges are easily excreted from the body with urine; while COT with poor thermal stability is less common in kidney stones. Therefore, in addition to directly inhibiting the crystallization of COM, converting COM into COD is also beneficial to reducing the risk of urinary stone formation.

[0003] In 2016, the University of Houston in the United States published a study on the effect of hydroxycitric acid on the crystallization of calcium oxalate crystals in Nature, Volume 536, Issue 7617, pages 446 - 450. The literature mentioned that hydroxycitric acid can significantly inhibit the crystal growth of calcium oxalate by adsorbing on the surface of calcium oxalate crystals, and at the same time, it can also break the ionic chemical bonds in calcium oxalate, thereby destroying the stability of the internal structure of the crystal and causing it to dissolve. In addition, there are also reports on the application of small molecule organic acids and their derivatives in controlling the crystallization process of calcium oxalate. For example, the invention patent with the application number CN201911304432.0 discloses an application method of small molecule acids in influencing the crystallization of calcium oxalate, that is, controlling the crystallization process of calcium oxalate through gallic acid and its derivatives. However, in the process of controlling the crystallization of calcium oxalate by the two small molecule organic acids and their derivatives reported above, the small molecule acids have poor stability, are difficult to be metabolized, have poor biocompatibility, and are difficult to enter cells. These disadvantages limit their practical application in inhibiting the crystallization of calcium oxalate in the human body.

[0004] Carbon dots are a type of carbon nanoparticles with a size less than 10 nanometers, having a graphitized carbon core and an amorphous outer shell composed of organic surface groups (such as carboxyl, hydroxyl, and carbonyl groups, etc.). This unique structure and composition endow carbon dots with good stability, water solubility, and biocompatibility. At the same time, the structure of carbon dots can be designed by choosing synthesis raw materials and methods. In this invention, a series of citric acid-based carbon dots with rich hydroxyl and carboxyl functional groups on the surface are synthesized by design. These carbon dots not only retain the effect of small molecule organic acids (citric acid) in inhibiting calcium oxalate crystallization but also have excellent properties such as the intrinsic high-brightness fluorescence of carbon dots. Therefore, the series of citric acid-based carbon dots show great application potential in the treatment of calcium oxalate stones. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a series of citric acid-based carbon dots with good water solubility, good stability, good biocompatibility, and a neutral pH value in aqueous solution, and their application in influencing the crystallization of calcium oxalate crystals, that is, in the aspect of inhibiting calcium crystallization, so that they can be expected to be used for the prevention and treatment of calcium stones.

[0006] To achieve the above object, the present invention provides a series of citric acid-based carbon dots with good stability. This type of carbon dots can improve the hydrophilicity of calcium oxalate crystals, inhibit the growth of calcium oxalate crystals, and promote the transformation of calcium oxalate monohydrate to calcium oxalate dihydrate; at the same time, the surface of this type of carbon dots has rich carboxyl and hydroxyl functional groups, which can combine with free calcium ions to form soluble complexes, reducing the supersaturation of calcium oxalate crystals in urine.

[0007] The series of citric acid-based carbon dots described in the present invention include hydroxycitric acid carbon dots, potassium citrate carbon dots, citric acid carbon dots, etc. They have good stability, good biocompatibility, and a neutral pH value in aqueous solution, and their surface contains rich carboxyl and hydroxyl functional groups.

[0008] The application of the series of citric acid-based carbon dots of the present invention in the preparation of calcium crystallization inhibitors, wherein the series of citric acid-based carbon dots are carbon dots obtained by chemical synthesis from a series of citric acid-based substances, and the series of citric acid-based substances are at least one of citric acid, hydroxycitric acid, and their salts, or at least one of substances containing citric acid, hydroxycitric acid, or their salts.

[0009] Preferably, the calcium crystallization can be at least one of calcium oxalate, calcium phosphate, calcium carbonate, and their hydrates, and the hydrates include but are not limited to at least one of monohydrates and polyhydrates.

[0010] Preferably, the calcium crystallization is calcium stones, including but not limited to at least one of urinary stones, kidney stones, gallstones, dental calculus, and bladder stones.

[0011] Preferably, the calcium crystal inhibitor may be a citric acid series of carbon dots or a substance containing a citric acid series of carbon dots. The substance containing a citric acid series of carbon dots may be some natural products, such as a substance containing hydroxycitric acid, which may be Garcinia cambogia fruit powder (containing about 90% hydroxycitric acid). Of course, it may also be some synthetic substances or some artificially compounded mixtures. Further, by adding some excipients commonly used in pharmaceutical preparations, a convenient drug or preparation can be formed, so that the substance containing a citric acid series of carbon dots becomes a drug or preparation containing a citric acid series of carbon dots. Of course, based on the citric acid series of carbon dots of the present invention, various types of pharmaceutically acceptable drug preparations, such as oral preparations, injection preparations, etc., can be prepared by basic pharmaceutical means.

[0012] The calcium crystal inhibition of the present invention is mainly achieved by the citric acid series of carbon dots of the present invention promoting the conversion of calcium stone components such as calcium oxalate from calcium oxalate monohydrate to calcium oxalate dihydrate or even to calcium oxalate trihydrate, that is, inhibiting the formation of calcium oxalate monohydrate with high thermal stability and promoting the formation of calcium oxalate dihydrate that is easily excreted with urine, so as to be used for preventing the formation of calcium oxalate stones.

[0013] In the present invention, the citric acid series of carbon dots can be prepared by the following method: using a citric acid series of substances as reaction raw materials, reacting by hydrothermal method or microwave method at high temperature, then adding water to dissolve, filtering and dialyzing, and then freeze-drying to complete the preparation; urea is added or not added to the reaction precursor. In the synthesis of carbon dots, the addition of urea is beneficial to the stability of some carbon dot structures, such as the carbon dot structures formed by citric acid and its salts, which can not only improve the synthesis yield but also improve their optical properties. For some carbon dots, such as the carbon dots formed by hydroxycitric acid and its salts, urea may not be added because the carbon dots themselves have a relatively stable structure, and at the same time have a high synthesis yield and excellent optical properties. On the other hand, for this type of carbon dots of hydroxycitric acid, it is also for the consideration of making its functional part more pure. Specifically:

[0014] In the present invention, the method for preparing carbon dots from Garcinia cambogia fruit powder containing hydroxycitric acid can be:

[0015] Weigh a certain amount of gamboge fruit powder (containing about 90% hydroxycitric acid), transfer it to a small crucible, and then put it into a muffle furnace for pyrolysis reaction for a certain period of time. After the reaction is completed, take out the pyrolysis sample in the small crucible and transfer it to a small beaker; add an appropriate amount of deionized water to the small beaker, stir it ultrasonically to dissolve it fully, and then let it stand for a period of time; filter the above solution by suction, collect the filtrate, put it into a dialysis bag with a certain molecular weight cut-off, dialyze it in ultrapure water, and obtain dark yellow carbon dots after freeze-drying the dialyzed solution; preferably, the reaction temperature of the muffle furnace is 160 - 220 °C, the reaction time is 6 - 10 hours, more preferably 200 °C for 8 hours; when filtering by suction, use a hydrophilic microporous membrane with a pore size of 0.22, the molecular weight cut-off of the dialysis bag is 500 - 2000 Da, preferably 800 - 1000 Da, most preferably 1000 Da, the dialysis time is 72 - 120 hours, and the freeze-drying time is 48 - 72 hours.

[0016] In the present invention, the method for preparing carbon dots using potassium citrate can be:

[0017] Weigh potassium citrate and urea, add them to ultrapure water, stir ultrasonically to accelerate complete dissolution, transfer the solution to a reaction kettle, and then put it into a muffle furnace for hydrothermal reaction for a certain period of time. After the reaction is completed, take out the reaction kettle and transfer the solution to a small beaker, stir it ultrasonically to mix it fully; filter the above solution by suction, collect the filtrate, put it into a dialysis bag with a certain molecular weight cut-off, dialyze it in ultrapure water, and obtain brown carbon dots after freeze-drying the dialyzed solution; preferably, add 1 - 2 g of potassium citrate, 1 - 1.5 g of urea and 20 - 40 mL of ultrapure water, the reaction temperature of the muffle furnace is 160 - 220 °C, the reaction time is 6 - 10 hours, more preferably 160 °C for 8 hours; when filtering by suction, use a hydrophilic microporous membrane with a pore size of 0.22, the molecular weight cut-off of the dialysis bag is 500 - 2000 Da, preferably 800 - 1000 Da, most preferably 1000 Da, the dialysis time is 72 - 120 hours, and the freeze-drying time is 48 - 72 hours.

[0018] In the present invention, the method for preparing carbon dots using citric acid can be:

[0019] Weigh citric acid and urea, add them to ultrapure water, and use ultrasonic waves and stirring to accelerate the complete dissolution. Transfer the solution to a small beaker, then place it in a microwave oven and carry out microwave reaction for a certain period of time. After the reaction ends, take out the small beaker; add an appropriate amount of deionized water to the small beaker and use ultrasonic waves and stirring to make it dissolve fully; filter the above solution by suction, collect the filtrate, put it into a dialysis bag with a certain molecular weight cut-off, and dialyze it in ultrapure water. The solution after dialysis is freeze-dried to obtain dark brown carbon dots; preferably add 4 - 5 grams of anhydrous citric acid, 1 - 1.5 grams of urea and 5 - 20 milliliters of ultrapure water. The microwave reaction power is medium-high fire (400 - 500 watts), and the reaction time is 4 - 8 minutes; when filtering by suction, use a water-based microporous membrane with a pore size of 0.22. The molecular weight cut-off of the dialysis bag is 500 - 2000 Daltons, preferably 800 - 1000 Daltons, and most preferably 1000 Daltons. The dialysis time is 72 - 120 hours, and the freeze-drying time is 48 - 72 hours.

[0020] In the above preparation method of the present invention, adding urea can be used as a nitrogen-doping auxiliary to form carbon dots to improve the properties of carbon dots.

[0021] In the present invention, there are great differences between the citric acid series carbon dots and common citric acid in terms of binding to calcium. Specifically: Although citric acid can directly form a calcium citrate complex with calcium, this substance, although not easily dissociated, can dissolve in water, unlike calcium oxalate which does not dissolve in water and forms a precipitate. However, because citric acid is absorbed into the body from the intestine or enters the body through direct injection, it will be decomposed by the liver into carbonic acid... very little can be excreted through the kidney in its original form. While the abundant -COOH on the surface of the citric acid series carbon dots of the present invention can coordinate with calcium ions, the calcium ion concentration around the citric acid series carbon dots increases rapidly, locally increasing the concentration ratio of calcium ions to oxalate ions; in addition, due to the enrichment of positively charged calcium ions on the surface of the citric acid series carbon dots, a high-energy interface is formed. At the same time, the freedom degree of the adsorbed calcium ions decreases and the energy state increases. This high-energy interface and high-energy environment will both promote the formation of calcium oxalate dihydrate (COD). The adhesion force between COD crystals and the renal cell membrane surface is much lower than that of calcium oxalate monohydrate (COM), and it is relatively easy to be excreted from the body with urine. At the same time, the citric acid series has good stability and is not easily decomposed or damaged. After its function is completed, it will be excreted from the body in the form of renal clearance. At this time, the metabolic situation can also be studied through the fluorescence properties of carbon dots.

[0022] The citric acid series carbon dots of the present invention can combine with free calcium ions to form soluble complexes, reduce the supersaturation of calcium oxalate in urine, and can also combine with the growth sites of calcium oxalate crystals to inhibit crystal growth. The citric acid series carbon dots contain acidic groups such as -COOH and -OH, and have low cytotoxicity and good stability. Therefore, the citric acid series carbon dots can be used to prevent the formation of calcium oxalate stones.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) The citric acid series carbon dots used in the present invention have good water solubility, good stability, low biological toxicity, and renal clearance, and can replace common organic small molecule acids with poor stability, high biological toxicity, and difficult metabolism to regulate the crystallization process of calcium oxalate stones;

[0025] 2) The citric acid series carbon dots prepared in the present invention have certain fluorescence properties. Based on the renal clearance mechanism of carbon dots, their metabolic situation can be studied by detecting whether fluorescence appears in the excreted fluid. At the same time, this property is also beneficial to some fluorescence detections.

[0026] 3) The citric acid series carbon dots prepared in the present invention can promote the transformation of calcium oxalate monohydrate into calcium oxalate dihydrate, which is easier to excrete from the body, and at the same time can reduce the average crystal grain size of calcium oxalate crystals; the addition of the citric acid series carbon dots also improves the hydrophilicity of calcium oxalate crystals and their solubility in water; such carbon dots show great application potential in the treatment of calcium stones. Description of the Drawings

[0027] Figure 1 It is the X-ray diffraction spectrum of calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots;

[0028] Figure 2 It is the scanning electron microscope image of calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots;

[0029] Figure 3 It is the infrared spectrum of calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots;

[0030] Figure 4 It is the X-ray diffraction spectrum of calcium oxalate monohydrate crystals and calcium oxalate monohydrate crystals under the influence of citric acid carbon dots. Detailed Embodiments

[0031] The following embodiments are further descriptions of the content of the present invention to illustrate the technical content of the present invention. However, the substantial content of the present invention is not limited to the following embodiments. Those of ordinary skill in the art can and should know that any simple changes or substitutions based on the substantial spirit of the present invention should fall within the protection scope required by the present invention.

[0032] Example 1

[0033] Application of hydroxycitric acid carbon dots in influencing the crystallization of calcium oxalate aqueous solution, specifically including the following steps:

[0034] 1) Weigh 3 grams of gamboge fruit powder. After grinding it thoroughly, transfer it to a small crucible.

[0035] 2) Place the small crucible in a muffle furnace and react at 200 °C for 8 hours to allow the reactants to react fully. After it cools to room temperature, take out the yellowish-brown solid in the small beaker. Add an appropriate amount of deionized water to the small beaker and stir it ultrasonically to dissolve it fully.

[0036] 3) Vacuum filter the above-obtained solution through an organic microporous membrane with a pore size of 0.22 μm, collect the filtrate, put it into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyze it in ultrapure water for 72 hours, and freeze-dry it for 48 - 72 hours to obtain brown carbon dots.

[0037] 4) Weigh 10 mg of hydroxycitric acid carbon dots and dissolve them in 8 mL of deionized water to prepare a hydroxycitric acid carbon dot solution. Then add it dropwise to 40 mL of solution A (22 mmol / L calcium chloride solution) and stir it ultrasonically to mix it evenly. Another 40 mL of solution B (22 mmol / L sodium oxalate solution) is measured and set aside for later use.

[0038] 5) Place the mixed solution A in a water bath at 37 °C, slowly add solution B to solution A, and obtain a calcium oxalate precipitate suspension after reacting for 10 minutes. Then let it stand for 2 hours to complete the precipitation.

[0039] 6) Pour the above suspension into a 100 mL centrifuge tube and centrifuge it at 8000 rpm for 10 minutes. After centrifugation, pour out the supernatant in the centrifuge tube, transfer the precipitate to a watch glass, and freeze-dry it to obtain calcium oxalate crystals affected by hydroxycitric acid carbon dots.

[0040] Example 2

[0041] Application of citric acid carbon dots in influencing the crystallization of calcium oxalate aqueous solution, which specifically includes the following steps:

[0042] 1) Weigh 4.5 grams of citric acid and 1.5 grams of urea, add 10 mL of ultrapure water, and stir it ultrasonically to accelerate the complete dissolution.

[0043] 2) Transfer the solution to a 50 mL small beaker, put it into a microwave oven, and keep it warm and react at medium-high power (400 - 500 W) for 4 minutes to allow the reactants to react fully. After it cools to room temperature, take out the dark brown solid in the small beaker. Add an appropriate amount of deionized water to the small beaker and stir it ultrasonically to dissolve it fully.

[0044] 3) Vacuum filter the above-obtained solution through an organic microporous membrane with a pore size of 0.22 μm, collect the filtrate, put it into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyze it in ultrapure water for 72 hours, and freeze-dry it for 48 - 72 hours to obtain dark brown carbon dots.

[0045] 4) Weigh 10 mg of citric acid carbon dots, dissolve them in 8 mL of deionized water to prepare a citric acid carbon dot solution, and add it dropwise to 40 mL of solution A (22 mmol / L calcium chloride solution), and stir it ultrasonically to make it mix evenly; Another 40 mL of solution B (22 mmol / L sodium oxalate solution) was measured and set aside for later use.

[0046] 5) Place the mixed solution A in a water bath at 37 °C, slowly add solution B to solution A, and after reacting for 10 minutes, obtain a calcium oxalate precipitate suspension, and then let it stand for 2 hours to complete the precipitation.

[0047] 6) Pour the above suspension into a 100 mL centrifuge tube and centrifuge it at 8000 rpm for 10 minutes; After centrifugation, pour out the supernatant in the centrifuge tube, transfer the precipitate to a watch glass, and obtain calcium oxalate crystals affected by citric acid carbon dots after freeze-drying.

[0048] Example 3

[0049] Application of potassium citrate carbon dots in influencing the crystallization of calcium oxalate aqueous solution, specifically including the following steps:

[0050] 1) Weigh 3 g of potassium citrate and 1 g of urea, add them to 30 mL of ultrapure water, and stir ultrasonically to accelerate complete dissolution.

[0051] 2) Transfer the solution to a reaction kettle, place it in a muffle furnace, and keep it at 160 °C for 8 hours to allow the reactants to react fully. After the reaction is complete, take out the inner liner and transfer the solution to a beaker.

[0052] 3) Vacuum filter the above-obtained solution through an organic microporous filter membrane with a pore size of 0.22 μm, collect the filtrate, put it into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyze it in ultrapure water for 72 hours, and freeze-dry it for 48 - 72 hours to obtain dark brown carbon dots.

[0053] 4) Weigh 10 mg of potassium citrate carbon dots, dissolve them in 8 mL of deionized water to prepare a potassium citrate carbon dot solution, and add it dropwise to 40 mL of solution A (22 mmol / L calcium chloride solution), and stir it ultrasonically to make it mix evenly; Another 40 mL of solution B (22 mmol / L sodium oxalate solution) was measured and set aside for later use.

[0054] 5) Place the mixed solution A in a water bath at 37 °C, slowly add solution B to solution A, and after reacting for 10 minutes, obtain a calcium oxalate precipitate suspension, and then let it stand for 2 hours to complete the precipitation.

[0055] 6) Pour the above suspension into a 100-ml centrifuge tube and centrifuge at 8,000 revolutions per minute for 10 minutes. After centrifugation, pour off the supernatant in the centrifuge tube, transfer the precipitate to a petri dish, and obtain calcium oxalate crystals affected by potassium citrate carbon dots after freeze-drying.

[0056] Figure 1 It is the energy spectrum diagram of X-ray diffractometer for calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots. It can be seen that the addition of hydroxycitric acid carbon dots significantly changes the crystal XRD signal. According to the control, the addition of hydroxycitric acid carbon dots significantly promotes the transformation of calcium oxalate monohydrate crystals to calcium oxalate dihydrate, which objectively facilitates the excretion of urinary calculus crystals out of the body.

[0057] Figure 2 It is the scanning electron microscope image of calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots. It can be known from this that the addition of hydroxycitric acid carbon dots promotes the transformation of calcium oxalate crystallization from calcium oxalate monohydrate to calcium oxalate dihydrate. The left figure a is the scanning electron microscope of the original calcium oxalate crystals, and its main body presents flaky crystals, belonging to calcium oxalate monohydrate; the right figure b is the calcium oxalate crystals affected by carbon dots, and it can be seen that it is mainly cubic crystals, belonging to calcium oxalate dihydrate; because calcium oxalate dihydrate is more easily excreted from the body, this kind of transformation is beneficial to inhibiting the aggregation of calcium oxalate crystals in the body.

[0058] Figure 3 It is the infrared spectrum diagram of calcium oxalate monohydrate crystals and calcium oxalate dihydrate crystals transformed under the influence of hydroxycitric acid carbon dots. The ν as (COO-) of calcium oxalate monohydrate and calcium oxalate dihydrate are 1617 and 1647 wavenumbers respectively, and the ν s (COO-) are 1318 and 1328 wavenumbers respectively. The addition of hydroxycitric acid carbon dots makes the ν as (COO-) and ν s (COO-) of calcium oxalate crystals blue-shift by 24 wavenumbers and 7 wavenumbers respectively, which indicates that the addition of hydroxycitric acid carbon dots promotes the transformation of calcium oxalate monohydrate to calcium oxalate dihydrate crystals, which is consistent with the Figure 1 XRD data and Figure 2 scanning electron microscope data.

[0059] Figure 4 It is the X-ray diffraction pattern of calcium oxalate monohydrate crystals and calcium oxalate monohydrate crystals under the influence of citric acid carbon dots. It can be seen that the addition of citric acid carbon dots significantly reduces the signal intensity of the crystal diffraction peak. According to the Scherrer formula D = Kλ / Bcosθ, the average grain size (D) can be calculated. The average grain size of calcium oxalate monohydrate crystals calculated from the XRD data in Figure 4 decreases from the original 365 nm to 292 nm after being affected by carbon dots, and the inhibition rate is 20%.

[0060] It should be noted that the above embodiments are only general verification examples of the technical content of the present invention, and it cannot be simply considered that the present invention is only limited to what is described in the above embodiments. The scope of the substantial protection of the present invention shall be subject to what is described in the claims. Those skilled in the art should be aware that any modifications, equivalent replacements, improvements, etc. made based on the substantial spirit of the present invention should all be within the scope of the substantial protection of the present invention.

Claims

1. Use of citric acid series carbon dots in the preparation of calcium crystallization inhibitors, wherein the citric acid series carbon dots are prepared by the following method: using citric acid series substances as reaction precursors, reacting by hydrothermal method or microwave method at high temperature, then adding water to dissolve, filtering by suction, dialyzing, and then freeze-drying; urea is added or not added to the reaction precursors; wherein, The high-temperature hydrothermal method involves reacting at 150 - 220 °C in a muffle furnace for 6 - 10 hours; the microwave method has a reaction power of medium-high fire, 400 - 500 watts, and a reaction time of 4 - 8 minutes; the citric acid series of substances is at least one of citric acid, hydroxycitric acid, and their salts, or is Garcinia cambogia fruit powder; the calcium crystal is calcium oxalate monohydrate crystal.

2. The application according to claim 1, characterized in that The citric acid series of carbon dots is used to prevent the formation of calcium oxalate stones.

3. The application according to claim 2, characterized in that, The calcium oxalate stone is a urinary stone.

4. The application according to claim 2, characterized in that, The calcium oxalate stone is at least one of kidney stones and bladder stones.

5. The application according to claim 1, characterized in that, The calcium crystal inhibitor is the citric acid series of carbon dots or a substance containing the citric acid series of carbon dots.

6. The application according to claim 5, characterized in that, The substance containing the citric acid series of carbon dots is a drug or preparation containing the citric acid series of carbon dots.

7. The application according to claim 1, characterized in that, During suction filtration, a water-based microporous membrane with a pore size of 0.22 microns is used, the dialysis bag has a molecular weight cut-off of 500 - 2000 Daltons, the dialysis time is 72 - 120 hours, and the freeze-drying time is 48 - 72 hours.

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