A method for visual detection of uric acid based on fluorescent carbon dots

Abstract

The application discloses a method for visual detection of uric acid based on fluorescent carbon dots, and belongs to the field of analysis and detection. The carbon dots are prepared by taking 3-amino phenyl boronic acid and L-glutamine as raw materials, and anhydrous ethanol and deionized water as solvents. The imino group in uric acid has a positive charge, while the boronic acid group on the surface of the carbon dots after doping treatment has a negative charge. There is an electrostatic interaction between the two and a complex is formed, so that the fluorescence is quenched, and in this process, the fluorescence color also changes. Based on this, a relationship curve between the uric acid concentration and the fluorescence quenching degree is constructed, the detection limit is as low as 33.0nM, and the method is applied to visual detection of uric acid in water samples, serum and urine, visual detection of uric acid is realized, and the detection limits are 33.0nM, 37.6nM and 72.0nM respectively. The method is simple, safe and efficient, and is suitable for routine analysis.

Description

Technical Field

[0001] This invention relates to a method for detecting uric acid based on fluorescent carbon dots visualization, belonging to the field of analytical detection. Background Technology

[0002] Uric acid (UA, 2,6,8-trihydroxypurine) is the final product of purine metabolism in the human body, mainly found in urine and serum. It plays a role in scavenging oxygen free radicals, maintaining immune function, and resisting oxidative stress. Normally, the concentration of UA in blood is between 0.13-0.46 mM, while the concentration in urine is between 1.49-4.46 mM. Abnormal UA levels in the human body can lead to gout, kidney disease, hypertension, hyperlipidemia, atherosclerosis, Parkinson's disease, Alzheimer's disease, and other related diseases. Therefore, monitoring uric acid levels in the human body is crucial for our health.

[0003] In recent years, various analytical methods for detecting UA have been developed, including high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), electrochemical methods, colorimetric methods, and capillary electrophoresis. While these methods offer high precision and reliability, they suffer from drawbacks such as poor selectivity, high toxicity, low sensitivity, and complex operation. Therefore, there is an urgent need to find a simpler, faster, and more sensitive method for UA detection.

[0004] Fluorescence spectroscopy, with its advantages of high sensitivity, good selectivity, and the ability to provide information such as excitation spectrum, emission spectrum, luminescence intensity, luminescence lifetime, and quantum yield, has become an important trace analysis technique. With the emergence of various novel luminescent materials, especially carbon quantum dots (carbon-based nanomaterials), fluorescence spectroscopy is finding increasingly widespread applications in environmental, pharmaceutical, biomedical, and sensing fields. In recent years, many researchers have used carbon dots as probes to detect uric acid (UA), but these methods are relatively conventional and mostly require enzyme participation, placing high demands on experimental conditions. Methods for directly detecting uric acid using fluorescent probes are rarely reported. Summary of the Invention

[0005] Technical issues:

[0006] Currently, various analytical methods for detecting uric acid have been developed, mainly including high-performance liquid chromatography (HPLC), electrochemical methods, and chemiluminescence methods. These methods suffer from problems such as poor selectivity, high toxicity, low sensitivity, and complex operation. Meanwhile, there are few reports on the use of fluorescence sensing technology to detect uric acid in serum (or urine), and it usually requires the participation of enzymes.

[0007] Technical solution:

[0008] A method for detecting uric acid based on fluorescent carbon dots includes the following steps:

[0009] (1) Carbon dots were prepared by a one-step hydrothermal method using 3-aminophenylboronic acid and L-glutamine as raw materials and anhydrous ethanol and deionized water as solvents. The carbon dot solution was obtained by filtration and dialysis purification.

[0010] (2) Prepare a series of uric acid standard solutions of different concentrations, mix the uric acid standard solutions of different concentrations with the sample solution, carbon dot solution and buffer solution to obtain a mixed reaction solution, and perform fluorescence spectroscopy detection after incubation for a period of time;

[0011] (3) A linear model of fluorescence quenching degree and uric acid concentration was constructed based on the change in fluorescence intensity after the addition of uric acid solutions of different concentrations;

[0012] (4) The sample to be tested is subjected to fluorescence spectroscopy detection, and the concentration of uric acid in the sample is obtained according to the linear model in step (3).

[0013] In one embodiment of the present invention, in step (1), the mass ratio of 3-aminophenylboronic acid to L-glutamine is 1:1.

[0014] In one embodiment of the present invention, in step (1), the volume ratio of anhydrous ethanol to deionized water is 1:2.

[0015] In one embodiment of the present invention, in step (1), the ratio of the total mass of 3-aminophenylboronic acid and L-glutamine raw materials to deionized water is 1g:20mL.

[0016] In one embodiment of the present invention, in step (1), the reaction temperature of the hydrothermal method is 180-200℃ and the time is 3-10h.

[0017] In one embodiment of the present invention, the synthesis step of carbon dots in step (1) is as follows: weigh 0.5g of 3-aminophenylboronic acid, 0.5g of L-glutamine and 20mL of deionized water into a beaker, add 10mL of anhydrous ethanol, sonicate for 10min to fully dissolve the mixture, and then react at 200℃ for 6h.

[0018] In one embodiment of the present invention, in step (1), the purification step of carbon dots is as follows: the synthesized crude carbon dot solution is centrifuged at 8000 rpm for 5 min, then filtered through a 0.22 μm microporous membrane to remove unreacted particles, and finally purified by dialysis with a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h to obtain the final carbon dots.

[0019] In one embodiment of the present invention, in step (2), the sample solution includes water sample, serum sample, and urine sample.

[0020] In one embodiment of the present invention, in step (2), the sample solution needs to be pretreated as follows before use: filtered through a 0.22 μm microporous membrane and diluted 50 times.

[0021] In one embodiment of the present invention, in step (2), the conditions for fluorescence spectroscopy detection are as follows: the fluorescence spectrum is measured using a fluorescence spectrometer, the width of the excitation slit and the emission slit of the spectrometer are both 1 nm, the integration time is 0.1 s; the excitation wavelength of the fluorescence spectrometer is 295 nm, the emission wavelength range is 320 nm-440 nm, and the step size is 1 nm.

[0022] In one embodiment of the present invention, the incubation time in step (2) is 3 minutes.

[0023] In one embodiment of the present invention, the buffer solution in step (2) is phosphate buffer (PBS) with a concentration of 10 mM and pH = 7.4.

[0024] In one embodiment of the present invention, the volume ratio of the sample solution, uric acid standard solution, phosphate buffer and carbon dot solution in step (2) is 1:1:1:1.

[0025] In one embodiment of the present invention, in step (3), when the sample solution is water, the linear model is: (F0-F) / F0=0.02197c(UA)-0.06278, the linear range is 7-30μM, and the detection limit is 33.0nM. Wherein F0 and F represent the fluorescence intensity of the system before and after the addition of uric acid, respectively, and c(UA) represents the concentration of uric acid.

[0026] In one embodiment of the present invention, in step (3), when the sample solution is serum, the linear model is: (F0-F) / F0=0.01909c(UA)-0.09767, where F0 and F represent the fluorescence intensity of the system before and after the addition of uric acid, respectively, and c(UA) represents the concentration of uric acid. The linear range is 6-40 μM, and the detection limit is 37.6 nM.

[0027] In one embodiment of the present invention, in step (3), the linear model for the sample solution in urine is: F0-F) / F0=0.01778c(UA)-0.04561, where F0 and F represent the fluorescence intensity of the system before and after the addition of uric acid, respectively, and c(UA) represents the concentration of uric acid. The linear range is 6-40 μM, and the detection limit is 72.0 nM.

[0028] This invention also provides the application of the above method in the field of biomedical detection.

[0029] Beneficial effects:

[0030] 1. This invention constructs a fluorescent sensor for the visual detection of uric acid in serum and urine. The carbon dots are spherical or near-spherical in appearance and have abundant functional groups on their surface, which improves the water solubility of the carbon dots and their binding ability with uric acid.

[0031] 2. This invention prepares nitrogen-boron co-doped carbon dots (N,B-CDs) using 3-aminophenylboronic acid and L-glutamine as raw materials, and anhydrous ethanol and deionized water as solvents. Uric acid exhibits a significant fluorescence quenching effect on these dots, and the degree of quenching is related to the uric acid concentration. This enables the quantitative detection of uric acid in serum and urine. Furthermore, this method is simple, rapid, and safe, suitable for routine analysis. In this invention, the imino groups in uric acid are positively charged, while the boric acid groups on the surface of the doped carbon dots are negatively charged. An electrostatic interaction exists between the two, forming a complex that quenches fluorescence, accompanied by a change in fluorescence color. Based on this, a curve showing the relationship between the degree of fluorescence quenching and uric acid concentration is constructed, enabling the visual detection of uric acid in serum and urine.

[0032] This invention achieves a linear detection range of 7-30 μM and a detection limit of 33.0 nM for uric acid in water samples, and a linear detection range of 6-40 μM for uric acid in serum and urine samples, with detection limits of 37.6 nM and 72.0 nM, respectively. The sample recoveries are 99.8%-104.2% and 99.5%-105.5%, respectively. Compared with other fluorescence detection methods, such as those requiring uricase to participate in fluorescence sensing, this invention utilizes the specific quenching of fluorescence by uric acid to achieve direct detection of uric acid. Furthermore, it allows for visual monitoring of uric acid based on changes in fluorescence color and has a low detection limit, which is of great significance in the biomedical field. Attached Figure Description

[0033] Figure 1 A flowchart for visually detecting uric acid in serum and urine using fluorescent carbon dots.

[0034] Figure 2 The fluorescence response results of carbon dots before and after the addition of uric acid in Example 2 are shown.

[0035] Figure 3 The fluorescence spectra are those of serum with different concentrations of uric acid added in Example 3.

[0036] Figure 4 This is the curve showing the relationship between the degree of fluorescence quenching and uric acid concentration in serum in Example 3.

[0037] Figure 5 This is a linear fitting curve of the fluorescence quenching degree in serum and the concentration range of 6-40 μM uric acid in Example 3.

[0038] Figure 6The fluorescence spectra of urine with different concentrations of uric acid added in Example 3 are shown.

[0039] Figure 7 This is the curve showing the relationship between the degree of fluorescence quenching in urine and the concentration of uric acid in Example 3.

[0040] Figure 8 This is a linear fitting curve of the fluorescence quenching degree in urine and the concentration range of 6-40 μM uric acid in Example 3.

[0041] Figure 9 This is a photograph showing the change in fluorescence color after adding carbon dots to uric acid in Example 4.

[0042] Figure 10 This is a graph showing the test results of the selective experiment in Example 5.

[0043] Figure 11 The figure shows the test results of the anti-interference experiment in Example 6.

[0044] Figure 12 Fluorescence images showing selectivity and interference resistance in Examples 5 and 6.

[0045] Figure 13 The graph shows the test results of the effect of pH on the detection effect of phosphate buffer solution in Example 7.

[0046] Figure 14 The graph shows the test results of the effect of reaction time on the detection of uric acid in Example 8. Detailed Implementation

[0047] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0048] Example 1: Preparation of Carbon Dot (CDs) Solution

[0049] Weigh 0.5 g of 3-aminophenylboronic acid and 0.5 g of L-glutamine into a beaker, add 20 ml of deionized water and 10 ml of anhydrous ethanol sequentially, and sonicate for 10 min to ensure complete dissolution. Then react at 200 °C for 6 h. Centrifuge the synthesized crude carbon dot solution at 8000 rpm for 5 min, then filter through a 0.22 μm microporous membrane to remove unreacted particles. Finally, dialysis the carbon dots using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h to obtain the final carbon dot solution. The carbon dot solutions used in subsequent experiments were all based on this.

[0050] Example 2: Preliminary investigation of the fluorescence response of uric acid before and after the addition of carbon dots

[0051] 0.4 ml of 1 mM uric acid solution was added to 0.4 ml of carbon dot solution (prepared in Example 1), and 0.4 ml of deionized water was added to 0.4 ml of carbon dot solution as a control. Both samples were diluted to 4 ml with deionized water, incubated for 3 minutes, and then fluorescence spectra were scanned. The test results are as follows: Figure 2 As shown, the addition of uric acid significantly quenches the fluorescence of the carbon dots, preliminarily indicating that this fluorescent probe has the potential to detect uric acid and is feasible for uric acid detection.

[0052] Example 3: Constructing a linear model for uric acid determination

[0053] Serum (or urine) samples are pretreated by filtering the samples through a 0.22 μm microporous membrane and then diluting them 50 times for later use.

[0054] Prepare sample solutions: carbon dot solution, phosphate buffer (pH=7.4), serum (or urine) sample, and uric acid standard solutions with concentrations of 0 (blank control), 6 μM, 9 μM, 15 μM, 20 μM, 30 μM, 40 μM, 50 μM, 60 μM, 70 μM, 80 μM, 90 μM, and 100 μM.

[0055] First, add 0.4 ml of carbon dot solution, 0.4 ml of serum (or urine) solution, 0.4 ml of uric acid standard solutions of different concentrations, and 0.4 ml of phosphate buffer (PBS, 10 mM, pH = 7.4) to the test tube in sequence, mix well, and finally make up to 4 ml with deionized water. Let stand and incubate for 3 min to obtain serum (or urine) solutions spiked with different uric acid concentrations and perform fluorescence spectroscopy detection.

[0056] Fluorescence spectrum of the determination system: Scanning conditions: excitation wavelength 295 nm, emission wavelength scanning range 320-440 nm, scanning once every 1 nm, slit width set to 1 nm / 1 nm (excitation slit / emission slit), obtaining the fluorescence intensity peak at 369 nm. The fluorescence spectrum in serum (or urine) is as follows. Figure 3 (or Figure 6 As shown in the figure; a sample solution with a uric acid concentration of 0 was added and fluorescence spectroscopy was performed. The fluorescence intensity peak F0 was obtained at 369 nm. The fluorescence intensity peak obtained by adding sample solutions with other concentrations of uric acid was F. The fluorescence quenching degree (F0-F) / F0 was recorded.

[0057] Plot a curve showing the relationship between the degree of fluorescence quenching and uric acid concentration in serum (or urine) sample solutions, such as... Figure 4 (or Figure 7 As shown in the figure, the linear fitting curves for fluorescence quenching degree and uric acid concentration are as follows: Figure 5 (or Figure 8As can be seen from the images, when the uric acid concentration is 6-40 μM, the degree of fluorescence quenching is linearly related to the uric acid concentration. The linear equations in serum and urine are (F0-F) / F0=0.01909c(UA)-0.09767 and (F0-F) / F0=0.01778c(UA)-0.04561, respectively, with correlation coefficients of 0.99589 and 0.99705, and detection limits of 37.6 nM and 72.0 nM, respectively.

[0058] In addition, without adding actual samples (i.e., using an equal volume of deionized water instead of serum or urine solution), and following the same incubation process as described above, aqueous solutions spiked with different uric acid concentrations were obtained and subjected to fluorescence spectroscopy detection. A curve showing the relationship between the degree of fluorescence quenching in the aqueous solution and the uric acid concentration was plotted. The specific linear relationship was: (F0-F) / F0=0.02197c(UA)-0.06278, with a linear range of 7-30 μM and a detection limit of 33.0 nM. Here, F0 and F represent the fluorescence intensity of the system before and after the addition of uric acid, respectively, and c(UA) represents the concentration of uric acid.

[0059] Example 4: Investigating the changes in fluorescence color during uric acid detection

[0060] Referring to Example 3, in a deionized water environment, 0.4 ml of uric acid solutions of different concentrations (0, 6, 7, 8, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100 μM) were added to 0.4 ml of carbon dots. The results obtained under 365 nm ultraviolet light irradiation are as follows. Figure 9 As shown, when uric acid is added to carbon dots, the fluorescence color changes from blue-violet to blue-green, and the higher the concentration of uric acid, the more obvious the change in fluorescence color.

[0061] Example 5 explores the selectivity of fluorescent carbon dot-based visualization for detecting uric acid in serum (or urine).

[0062] Referring to Example 3, more than twenty substances commonly found in serum and urine (Ca) were used. 2+ Cl - Cu 2+ Fe 2+ Fe 3+ ,K + Mg 2+ NH4 + P2O7 4- SO4 2- Zn 2+Cysteine, glutathione, creatinine, allantoin, urea, glucose, glycine, methionine, tyrosine, threonine, and histidine were used as interfering agents to study the selectivity of uric acid detection in serum (or urine). The concentration of both uric acid and the interfering agents was 100 μM. The blank control was the fluorescence intensity without added uric acid (i.e., only carbon dots). Detection results are as follows: Figure 10 As shown.

[0063] It is obvious that, although Fe 3+ It also has a certain quenching effect on fluorescence, but its effect is negligible compared to uric acid. Furthermore, iron in the human body is primarily metabolized as Fe. 2+ It exists in the form of Fe, even if Fe exists. 3+ It will also be reduced to Fe. 2+ Then it is absorbed by the human body. Additionally, the color of the fluorescence, such as... Figure 12 As shown in Figures A and B, these are photographs taken under sunlight and ultraviolet light, respectively. After fluorescence quenching, the color turns blue-green.

[0064] Example 6 investigates the anti-interference capability of fluorescence carbon dot-based visualization for detecting uric acid in serum (or urine).

[0065] Referring to Examples 3 and 5, the anti-interference effect of the same substance as the interfering agent was studied to detect uric acid in serum (or urine). Uric acid and the interfering agent were mixed separately, and the reaction solution was prepared according to step (2) in Example 3. The concentrations of both uric acid and the interfering agent were 100 μM. The blank control was the fluorescence intensity without the addition of uric acid. The detection results are as follows: Figure 11 As shown.

[0066] As the image shows, even with the simultaneous addition of uric acid and interfering substances, a significant fluorescence quenching phenomenon still occurs, further demonstrating that the presence of interfering substances has virtually no impact on the detection of uric acid. Additionally, considering the fluorescence color, such as... Figure 12 As shown in C and D, these are photographs taken under sunlight and ultraviolet light, respectively. The fluorescence color changes to blue-green when uric acid is present.

[0067] Combined with Examples 5 and 6, it was demonstrated that the fluorescence sensing platform can detect uric acid in serum (or urine) with high selectivity and sensitivity, and can also visualize uric acid with the naked eye, further demonstrating the feasibility and accuracy of this detection scheme.

[0068] Example 7 Investigates the effect of phosphate buffer solution on uric acid detection

[0069] Referring to step (2) in Example 3, phosphate buffer solutions with different pH values ​​(4-12) were added to a mixed solution of carbon dots and uric acid, and the results were measured as follows. Figure 13As shown, the fluorescence quenching is most ideal when the pH of the buffer solution is 9. Considering that the detection environment is serum and urine, the pH of the buffer solution is fixed at 7.4 when detecting uric acid.

[0070] Example 8 investigates the effect of reaction time on uric acid detection.

[0071] Referring to Example 3, a standard uric acid solution was added to the carbon dots, and the fluorescence spectrum of the system was recorded every minute. The results are as follows: Figure 14 As shown, the entire reaction process is relatively rapid; fluorescence quenching occurs almost immediately after the addition of uric acid, and there is virtually no significant change within approximately 30 minutes. Therefore, all samples were incubated for 3 minutes before fluorescence testing of uric acid.

[0072] In conjunction with Examples 7 and 8, when detecting uric acid in serum (or urine), the pH of the phosphate buffer was fixed at 7.4, the incubation time of the reaction solution was controlled at 3 min, and fluorescence spectroscopy was finally performed under these conditions.

[0073] Example 9: Detection of uric acid in serum (or urine) environment

[0074] Referring to Example 3, uric acid concentrations of 20, 30, and 40 μM were measured. The results are shown in Table 1. The results are satisfactory, indicating that this method is accurate, feasible, and can be applied to the detection of uric acid in the biomedical field.

[0075] Table 1 Test results of Example 9

[0076]

[0077] Comparative Example 1: Optimization of Carbon Dot Raw Materials

[0078] Referring to Example 1, 0.5 g of 3-aminophenylboronic acid and 0.5 g of polyethyleneimine were weighed into a beaker, and 20 ml of deionized water and 10 ml of anhydrous ethanol were added sequentially. The mixture was sonicated for 10 min to ensure complete dissolution, and then reacted at 200 °C for 6 h. The synthesized crude carbon dot solution was centrifuged at 8000 rpm for 5 min, then filtered through a 0.22 μm microporous membrane to remove unreacted particles. Finally, the carbon dots were purified by dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h to obtain the corresponding carbon dot solution.

[0079] Comparative Example 2: Optimization of Carbon Dot Raw Materials

[0080] Referring to Example 1, 0.5 g of 3-aminophenylboronic acid and 0.5 g of L-arginine were weighed into a beaker, and 20 ml of deionized water and 10 ml of anhydrous ethanol were added sequentially. The mixture was sonicated for 10 min to ensure complete dissolution, and then reacted at 200 °C for 6 h. The synthesized crude carbon dot solution was centrifuged at 8000 rpm for 5 min, then filtered through a 0.22 μm microporous membrane to remove unreacted particles. Finally, the carbon dots were purified by dialysis using a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h to obtain the corresponding carbon dot solution.

[0081] The fluorescence response of the corresponding carbon dots before and after the addition of uric acid was tested according to Example 2, and the results are shown in Table 2.

[0082] Table 2 Performance results of different carbon points

[0083] Carbon dot raw materials performance 3-Aminophenylboronic acid + L-glutamine The fluorescence exhibits significant quenching, and the fluorescence color changes. 3-Aminophenylboronic acid + polyethyleneimine The fluorescence exhibits weak quenching, but the fluorescence color remains unchanged. 3-Aminophenylboronic acid + L-arginine Fluorescence did not quench, and the fluorescence color did not change.

[0084] Based on the results in Table 2, the carbon dots synthesized from 3-aminophenylboronic acid and L-glutamine showed a significant fluorescence response to uric acid and can be used for the detection of uric acid.

[0085] Comparative Example 3: Comparison of Existing Methods for Uric Acid Detection

[0086] The method of Example 3 of this invention was compared with other fluorescence detection methods, and the results are shown in Table 3. The data in Table 3 clearly show that this method has a lower detection limit, which is one to two orders of magnitude lower than most methods, demonstrating significant advantages and broad application prospects.

[0087] Table 3 Comparison of detection results from different methods

[0088] method raw material Detection limit (nM) source N-CDs Citric acid monohydrate, diethylenetriamine 60 [1] CDs melodramatic 500 [2] <![CDATA[Fe 3+ @b-CDs]]> aminonaphthalene, chloroform 67640 [3] Fe / N-CDs Ferric chloride, ethylenediaminetetraacetic acid, diethylenetriamine 140 [4] N,P-CDs Citric acid, urea, formamide, phosphoric acid 400 [5] CDs pork 50 [6] S,N-CDs Citric acid, thiourea 70 [7] S,N-CDs Citric acid, L-cysteine 800 [8] Si / N-CDs 3-Aminopropyltriethoxysilane, citric acid 140 [9] MnO2@CDs Citric acid, ethylenediamine 45

[10] Ag NPs / N-CDs Hydroxyethyl cellulose, L-citrulline 530

[11] g-CDs Passion fruit shell powder, m-phenylenediamine 940

[12] MCDs Maleic acid, benzoic acid 2260

[13] Arg-CDs L-arginine, DL-malic acid 7140

[14] N,B-CDs 3-Aminophenylboronic acid, L-glutamine 33 This method

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[0103] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined in the claims of this invention.

Claims

1. A method for detecting uric acid based on fluorescent carbon dots for visualization, characterized in that, Includes the following steps: (1) Carbon dots were prepared by a one-step hydrothermal method using 3-aminophenylboronic acid and L-glutamine as raw materials and anhydrous ethanol and deionized water as solvents. The carbon dots were then purified to obtain a carbon dot solution. (2) Prepare a series of uric acid standard solutions of different concentrations, mix the uric acid standard solutions of different concentrations with the sample solution, carbon dot solution and buffer solution to obtain a mixed reaction solution, and perform fluorescence spectroscopy detection after incubation for a period of time; (3) A linear model of fluorescence quenching degree and uric acid concentration was constructed based on the change in fluorescence intensity after the addition of uric acid solutions of different concentrations; (4) The sample to be tested is subjected to fluorescence spectroscopy detection, and the concentration of uric acid in the sample is obtained according to the linear model in step (3).

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of 3-aminophenylboronic acid and L-glutamine is 1:1; the volume ratio of anhydrous ethanol and deionized water is 1:2; and the ratio of the total mass of 3-aminophenylboronic acid and L-glutamine raw materials to deionized water is 1g:20mL.

3. The method according to claim 1, characterized in that, In step (1), the reaction temperature of the hydrothermal method is 180-200℃ and the time is 3-10h.

4. The method according to claim 1, characterized in that, In step (1), the purification steps of carbon dots are as follows: the synthesized crude carbon dot solution is centrifuged at 8000 rpm for 5 min, then filtered through a 0.22 μm microporous membrane to remove unreacted particles, and finally purified by dialysis with a dialysis membrane with a molecular weight cutoff of 1000 Da for 24 h to obtain carbon dot solution.

5. The method according to claim 1, characterized in that, In step (2), the volume ratio of the sample solution, uric acid standard solution, buffer solution and carbon dot solution is 1:1:1:

1.

6. The method according to claim 1, characterized in that, In step (2), the sample solution includes water sample, serum sample, and urine sample.

7. The method according to claim 1, characterized in that, In step (2), the sample solution needs to be pretreated as follows before use: filtered through a 0.22 μm microporous membrane and diluted 50 times.

8. The method according to claim 1, characterized in that, In step (2), the conditions for fluorescence spectroscopy detection are as follows: the fluorescence spectrum is measured using a fluorescence spectrometer, the width of the excitation slit and the emission slit of the spectrometer are both 1 nm, the integration time is 0.1 s; the excitation wavelength of the fluorescence spectrometer is 295 nm, the emission wavelength range is 320 nm-440 nm, and the step size is 1 nm.

9. The method according to claim 1, characterized in that, The incubation time mentioned in step (2) is 3 minutes.

10. The method according to any one of claims 1-9, characterized in that, The buffer solution in step (2) is a phosphate buffer with a concentration of 10 mM and pH = 7.4.

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