Application of a sulfur quantum dot fluorescent probe in tryptophan detection

Abstract

This invention belongs to the field of fluorescence analysis technology and relates to the application of a sulfur quantum dot fluorescent probe in tryptophan detection. This invention utilizes sulfur quantum dot probes to explore exogenous tryptophan cell imaging technology, studies the role of ultraviolet light in cell imaging, and enhances the fluorescence signal intensity of the sulfur quantum dot fluorescent probe by ultraviolet light irradiation, effectively achieving in vitro quantitative detection of tryptophan and highly sensitive, highly selective in situ detection in living cells. This invention can be used for the detection of tryptophan in vitro and in living cells, and has promising clinical application prospects in the biomedical field.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence analysis technology, specifically relating to the application of a sulfur quantum dot fluorescent probe in tryptophan detection. Background Technology

[0002] Amino acids, as core molecules constituting the basic structure and function of living organisms, play an indispensable role in physiological processes such as metabolic regulation, signal transduction, and biosynthesis. Among them, tryptophan holds a crucial position due to its unique structure. It is not only an essential amino acid for protein synthesis but also a key precursor to neuroactive substances such as serotonin and melatonin, directly participating in higher neurological functions such as mood regulation and sleep maintenance. Abnormal tryptophan levels in the body are closely related to various mental disorders, and excessive intake may lead to the accumulation of metabolites through the kynurenine pathway, even causing kidney damage. Therefore, achieving quantitative detection of tryptophan in vitro and in situ monitoring of tryptophan concentration and distribution in living cells is of significant scientific importance for a deeper understanding of its physiological and pathological mechanisms of action.

[0003] Currently, tryptophan detection mainly relies on traditional analytical techniques such as high-performance liquid chromatography (HPLC), capillary electrophoresis, spectrophotometry, and electrochemical methods. While these methods offer high sensitivity and accuracy, they typically require complex sample pretreatment, expensive instruments, and specialized operating environments, and are difficult to apply directly to monitoring in live cell systems. Therefore, developing a novel sensing strategy that is easy to operate, low-cost, and suitable for in vitro and live cell detection has become a critical issue that urgently needs to be addressed in this field.

[0004] In recent years, sulfur quantum dots (SQDs), as an emerging non-metallic fluorescent nanomaterial, have shown broad application prospects in fields such as biosensing, environmental monitoring, and antibacterial materials due to their excellent optical properties, good biocompatibility, significant Stokes shift, and ease of functionalization. Studies have shown that by rationally designing synthesis methods, the fluorescence properties of SQDs can be regulated, and they can be used to construct highly selective and sensitive fluorescent probes. For example, existing studies have applied SQDs to metal ion detection and antibacterial coating construction, demonstrating their application potential in multidisciplinary fields. However, current research on the application of SQDs in in vitro and intracellular detection remains relatively limited. Summary of the Invention

[0005] To address the above problems, this invention provides an application of a sulfur quantum dot fluorescent probe in tryptophan detection. This invention enhances the fluorescence intensity of the sulfur quantum dot fluorescent probe by ultraviolet light irradiation, achieving both in vitro quantitative detection of tryptophan and highly sensitive, highly selective in situ detection within living cells. This method is simple to operate, reacts rapidly with tryptophan, and has high detection sensitivity. It can be used for in vitro quantitative detection of tryptophan and in situ detection of tryptophan within living cells, showing promising clinical application prospects.

[0006] To achieve the above objectives, the present invention includes the following technical solutions:

[0007] This invention provides a sulfur quantum dot fluorescent probe that, under UV enhancement, is applied to the in vitro quantitative detection and in situ intracellular detection of tryptophan. The in situ intracellular detection includes both qualitative and quantitative detection. The preparation method of the sulfur quantum dot fluorescent probe is as follows: Step S1: 2.8g of sublimed sulfur, 100mL of ultrapure water, 8.0g of sodium hydroxide and 6mL of polyethylene glycol-400 were added sequentially to a round-bottom flask. Under stirring, the mixture was refluxed at 70°C for 72 hours to obtain a uniform orange-red solution. The product obtained was sulfur quantum dots. In step S2, the sulfur quantum dots obtained in step S1 are mixed with 4.1 wt% hydrogen peroxide solution at a volume ratio of 1.5:2 for 5 minutes and then purified by rotary evaporation for 20 minutes to remove excess unreacted hydrogen peroxide and obtain purified sulfur quantum dots. The purified sulfur quantum dots are then freeze-dried and stored in powder form. When used, they are dissolved in purified water to the target concentration to prepare sulfur quantum dot fluorescent probes.

[0008] Furthermore, the in vitro quantitative detection of tryptophan using sulfur quantum dot fluorescent probes includes the following steps: Step S1: The sulfur quantum dot fluorescent probe, PBS buffer, and tryptophan solutions of different gradient concentrations are mixed at a volume ratio of 2:1:2. After irradiation with ultraviolet light, the fluorescence intensity is measured and a standard curve is plotted. The equation of the standard curve is: y=4.3x-55.2, R²=0.9735, where x is the tryptophan concentration, y is the luminescence intensity of the sulfur quantum dot fluorescent probe, the linear range is 12~40μmol / L, and the detection limit is 4.35μmol / L. In step S2, sulfur quantum dot fluorescent probe and PBS buffer are added to the test solution, wherein the volume ratio of sulfur quantum dot fluorescent probe, PBS buffer and test solution is 2:1:2. After irradiation with ultraviolet light, the fluorescence intensity is measured, and the concentration of tryptophan is calculated based on the measured fluorescence intensity and the standard curve equation obtained in step S1.

[0009] Furthermore, the concentration of the sulfur quantum dot fluorescent probe is 1.477 mg / mL.

[0010] Furthermore, the ultraviolet light wavelength is 365 nm, the power is 20-90 W, and the ultraviolet light irradiation time is 5-30 min. The fluorescence intensity of the reaction between the sulfur quantum dot fluorescent probe and tryptophan after ultraviolet irradiation is significantly improved compared to the reaction without ultraviolet irradiation, and this improvement increases with increasing ultraviolet light power. After 15 min of ultraviolet light irradiation, the fluorescence intensity of the reaction between the sulfur quantum dot fluorescent probe and tryptophan has already significantly increased, and the fluorescence intensity increases stepwise with time.

[0011] Furthermore, the excitation wavelength used to measure the fluorescence intensity was 360 nm.

[0012] Furthermore, the in-situ qualitative detection of tryptophan in cells using sulfur quantum dot fluorescent probes includes the following steps: Cells were seeded in confocal culture dishes. After cell maturation, sulfur quantum dot fluorescent probes and PBS buffer were added to the dishes at a volume ratio of 2:1:2. After UV irradiation, the cells were incubated at 37°C for 30 min. The culture medium was then discarded, and the cells were washed three times with PBS buffer before cell imaging. The presence or absence of fluorescence signals indicates the presence of tryptophan in the cells.

[0013] Furthermore, the in situ quantitative detection of tryptophan in cells using sulfur quantum dot fluorescent probes includes the following steps: Step S1: Seed cells in confocal culture dishes and culture them in an incubator until mature. Then, treat them with different gradient concentrations of tryptophan. Add sulfur quantum dot fluorescent probes and PBS buffer to the cells treated with tryptophan. The volume ratio of sulfur quantum dot fluorescent probes, PBS buffer and cell test liquid is 2:1:2. After irradiation with ultraviolet light, incubate at 37°C for 30 min, remove the cells, discard the culture medium, wash them three times with PBS buffer, and then perform cell imaging. Measure the fluorescence intensity and plot a standard curve. In step S2, sulfur quantum dot fluorescent probe and PBS buffer are added to the cells to be tested. The volume ratio of sulfur quantum dot fluorescent probe, PBS buffer and cell test liquid is 2:1:2. After irradiation with ultraviolet light, the cells are incubated at 37°C for 30 min. After washing three times with PBS buffer, cell imaging is performed and the fluorescence intensity is measured. The concentration of tryptophan in the cells is calculated based on the measured fluorescence intensity and the standard curve equation obtained in step S1.

[0014] Furthermore, the concentration of the sulfur quantum dot fluorescent probe used in the in situ intracellular detection was 1.477 mg / mL. After incubating the cells with the 1.477 mg / mL sulfur quantum dot fluorescent probe for 24 hours, followed by irradiation with 30-50 W of ultraviolet light, the cell viability reached 80%.

[0015] Furthermore, the ultraviolet light wavelength used in the in situ intracellular detection was 365 nm, with a power of 30-50 W and an irradiation time of 15 min. When the ultraviolet light power was within the 30-50 W range, the cell viability reached over 80%. The highest cell viability was achieved when the ultraviolet light irradiation power was 50 W.

[0016] Furthermore, the excitation wavelength used for cell imaging in in situ intracellular detection is 408 nm. Attached Figure Description

[0017] Figure 1 The transmission electron microscopy (TEM) morphology characterization results of sulfur quantum dots in Example 1 are shown.

[0018] Figure 2 The results show the fluorescence intensity of the sulfur quantum dot fluorescent probe from Example 1 reacting with different amino acids, ionic liquids, and ascorbic acid.

[0019] Figure 3 The results show the fluorescence intensity of the sulfur quantum dot fluorescent probe and different concentrations of tryptophan in Example 1.

[0020] Figure 4 This is a graph showing the linear relationship between the fluorescence intensity measured by the sulfur quantum dot fluorescent probe in Example 1 and the change in tryptophan concentration.

[0021] Figure 5 The fluorescence ratio changes of sulfur quantum dot fluorescent probe reacting with tryptophan under different pH conditions in Example 1.

[0022] Figure 6 Example 1 illustrates the effect of different power ultraviolet light irradiation on the fluorescence intensity generated by the reaction of sulfur quantum dot fluorescent probe with tryptophan.

[0023] Figure 7 Example 1 illustrates the effect of different UV irradiation times on the fluorescence intensity generated by the reaction of sulfur quantum dot fluorescent probes with tryptophan.

[0024] Figure 8 This is Example 1, which illustrates the effect of different detection times on the fluorescence intensity generated by the reaction of sulfur quantum dot fluorescent probes with tryptophan.

[0025] Figure 9 Example 1 illustrates the effect of ultraviolet light irradiation power on cell activity.

[0026] Figure 10 This is a comparison of the signal intensity of the sulfur quantum dot fluorescent probe recognizing intracellular tryptophan under ultraviolet light irradiation in Example 1.

[0027] Figure 11 The signal intensity results for Example 1, which uses a sulfur quantum dot fluorescent probe to identify cells containing different concentrations of tryptophan, are shown. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. It should be understood that the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the embodiments of this application.

[0029] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0030] Example 1 (1) Preparation of sulfur quantum dot fluorescent probes The preparation method of sulfur quantum dot fluorescent probes by simple reflux synthesis includes the following steps: Step S1: 2.8g of sublimed sulfur, 100mL of ultrapure water, 8.0g of sodium hydroxide and 6mL of polyethylene glycol-400 were added sequentially to a 100mL round-bottom flask. Under stirring, the mixture was refluxed at 70°C for 72 hours to obtain a uniform orange-red solution. The product obtained was sulfur quantum dots. Step S2: The sulfur quantum dots obtained in step S1 are mixed with 4.1 wt% hydrogen peroxide solution at a volume ratio of 1.5:2 for 5 minutes, followed by rotary evaporation for 20 minutes to purify the mixture and remove excess unreacted hydrogen peroxide, thus obtaining purified sulfur quantum dots. The purified sulfur quantum dots are then lyophilized and stored as powder. When needed, they are dissolved in purified water to the target concentration to prepare a sulfur quantum dot fluorescent probe.

[0031] pass Figure 1 Transmission electron microscopy (TEM) characterization results show that the purified sulfur quantum dot nanomaterials are uniformly dispersed and have a spherical morphology.

[0032] (2) Selectivity of sulfur quantum dot fluorescent probes for tryptophan 2 mL of sulfur quantum dot fluorescent probe with a concentration of 1.477 mg / mL, 1 mL of PBS buffer with a concentration of 0.01 mol / L (pH=7.2~7.4) and 2 mL of ascorbic acid, different types of amino acids or ionic liquids were reacted, and then the mixture was irradiated with 90W ultraviolet light at a wavelength of 365 nm for 30 minutes before fluorescence intensity was detected.

[0033] The ascorbic acid concentration was 40 μmol / L, and the concentrations of different amino acids were 40 μmol / L for glycine, arginine, aspartic acid, glutathione, histidine, proline, lysine, glutamic acid, cysteine, phenylalanine, methionine, and tryptophan. The concentration of each amino acid and each ionic liquid was 2.4 mmol / L. + 56 mmol / L Na + and 4µmol / L Fe 3+ . Figure 2 This indicates that the UV-enhanced sulfur quantum dot fluorescent probe has high specificity for tryptophan detection, while other interfering substances, even after UV-assisted treatment, still failed to induce a fluorescence response in the sulfur quantum dot fluorescent probe sensing system.

[0034] Two mL of a 1.477 mg / mL sulfur quantum dot fluorescent probe and one mL of a 0.01 mol / L PBS buffer (pH 7.2–7.4) were reacted with two mL of tryptophan test solutions of different concentrations. After irradiation with 365 nm ultraviolet light at 90 W for 30 minutes, fluorescence detection was performed. The results are as follows: Figure 3 As shown, with the increase of tryptophan concentration, the fluorescence intensity of the sulfur quantum dot fluorescent probe at 455 nm is significantly enhanced, and the position of the fluorescence peak is red-shifted. Figure 4 The results show that within the tryptophan concentration range of 12–40 μmol / L, the luminescence intensity of the sulfur quantum dot fluorescent probe exhibits a good linear relationship with the tryptophan concentration, with the linear equation being: y = 4.3x - 55.2 (R² = 0.9735), and the limit of detection (LOD) being 4.35 μmol / L (3σ / k), where x is the tryptophan concentration and y is the luminescence intensity of the sulfur quantum dot fluorescent probe.

[0035] (3) Determination of reaction conditions for sulfur quantum dot fluorescent probe 1.477 mg / mL of sulfur quantum dot fluorescent probe and 0.01 mol / L PBS buffer were added to the tryptophan test solution for reaction, with the volume ratio of sulfur quantum dot fluorescent probe to buffer and tryptophan test solution being 2:1:2. After irradiation with ultraviolet light at a wavelength of 365 nm for a certain period, fluorescence spectroscopy was performed with a fixed excitation wavelength of 360 nm.

[0036] To investigate the effect of pH on the sulfur quantum dot fluorescent probe, other reaction conditions were kept constant, and reactions were carried out with 0.01 mol / L PBS buffer at different pH values. The results are as follows. Figure 5 As shown, the sulfur quantum dot fluorescent probe exhibits high stability and good fluorescence performance in the pH range of 6.0 to 8.0.

[0037] To investigate the effect of ultraviolet light irradiation power on the sulfur quantum dot fluorescent probe, other reaction conditions were kept constant, and the system was irradiated with ultraviolet light at a power of 20–90 W. A control group without ultraviolet irradiation was also included. The results are as follows: Figure 6 As shown, the fluorescence intensity of the sulfur quantum dot fluorescent probe was significantly improved after ultraviolet irradiation compared with the control group, and the intensity increased with the increase of ultraviolet light power.

[0038] To investigate the effect of UV irradiation time on the sulfur quantum dot fluorescent probe, other reaction conditions were kept constant, and the probe was irradiated with 90W UV light for 5–30 minutes. The results are as follows: Figure 7 As shown, after 15 minutes of ultraviolet light irradiation, the fluorescence intensity generated by the reaction of the sulfur quantum dot fluorescent probe with tryptophan has been significantly improved, and the fluorescence intensity increases stepwise with time.

[0039] To investigate the effect of detection time on the sulfur quantum dot fluorescent probe, other reaction conditions were kept constant, and fluorescence measurements were performed within 1–10 minutes after the system reaction. The results are as follows: Figure 8 As shown, the fluorescence intensity generated by the reaction of the sulfur quantum dot fluorescent probe with tryptophan remains highly stable, indicating that the system has a rapid response capability to tryptophan.

[0040] Based on the above results, the sulfur quantum dot fluorescent probe can achieve rapid detection of trace amounts of tryptophan under physiological pH conditions.

[0041] (4) Effects of sulfur quantum dot fluorescent probes on living cells Add 1.477 mg / mL of sulfur quantum dot fluorescent probe and 0.01 mol / L PBS buffer (pH=7.2~7.4) to cell culture dishes. The volume ratio of sulfur quantum dot fluorescent probe, PBS buffer, and cells is 2:1:2. After irradiation with ultraviolet light at a wavelength of 365 nm and a power of 30~50W for 15 minutes, cell viability is measured. A control group is also included. The results are as follows: Figure 9 As shown, with ultraviolet light power ranging from 30 to 50 W, cell viability reached over 80%. The highest cell viability was observed at an ultraviolet light power of 50 W. Furthermore, these results indicate that the sulfur quantum dot fluorescent probe possesses good biocompatibility and low cytotoxicity.

[0042] MCF-7 cells were seeded in confocal culture dishes and cultured until mature before being treated with 80 μmol / L tryptophan. 1.477 mg / mL sulfur quantum dot fluorescent probe and 0.01 mol / L PBS buffer (pH 7.2–7.4) were added to the tryptophan-treated cells at a volume ratio of 2:1:2. The cells were then divided into two groups: the first group served as the control group, and the second group was irradiated with 50 W UV light at 365 nm for 15 minutes, followed by incubation at 37°C for 30 minutes. After incubation, the culture medium was discarded, and the cells were washed three times with PBS before imaging using a Leica TCS SP8 DIVE two-photon confocal microscope (Leica Microsystems, Germany) with an excitation wavelength of 408 nm. The cell imaging results are shown below. Figure 10 As shown, ultraviolet light irradiation significantly enhances the signal intensity of the sulfur quantum dot fluorescent probe in recognizing tryptophan.

[0043] MCF-7 cells were seeded in confocal culture dishes and cultured until mature. The cells were then divided into four groups: group 1 served as the control group, group 2 received 20 μmol / L tryptophan treatment, and group 3 received 5 mmol / L tryptophan treatment. Subsequently, 1.477 mg / mL sulfur quantum dot fluorescent probe and 0.01 mol / L PBS buffer (pH 7.2–7.4) were added to each group of cells for reaction, with a volume ratio of sulfur quantum dot fluorescent probe, PBS buffer, and cells of 2:1:2. All three groups of cells were irradiated with 50 W UV light at 365 nm for 15 minutes and then incubated at 37°C for 30 minutes. After removal, the culture medium was discarded, and the cells were washed three times with PBS solution. Cell imaging was performed using a Leica TCS SP8 DIVE two-photon confocal microscope (Leica Microsystems, Germany) with an excitation wavelength set to 408 nm. The cell imaging results are shown below. Figure 11 As shown, different concentrations of tryptophan induced fluorescence emission in the blue channel, confirming that the sulfur quantum dot fluorescent probe has the ability to specifically recognize intracellular tryptophan. Furthermore, the fluorescence signal increases with increasing tryptophan concentration, indicating a positive correlation between the fluorescence signal recognized by the sulfur quantum dot fluorescent probe and the intracellular tryptophan concentration.

[0044] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An application of a sulfur quantum dot fluorescent probe in tryptophan detection, characterized in that, The sulfur quantum dot fluorescent probe is used for in vitro quantitative detection and intracellular in situ detection under ultraviolet enhancement. The intracellular in situ detection includes intracellular in situ qualitative detection and intracellular in situ quantitative detection. The preparation method of the sulfur quantum dot fluorescent probe is as follows: Step S1: 2.8g of sublimed sulfur, 100mL of ultrapure water, 8.0g of sodium hydroxide and 6mL of polyethylene glycol-400 were added sequentially to a round-bottom flask. Under stirring, the mixture was refluxed at 70°C for 72 hours to obtain a uniform orange-red solution. The product obtained was sulfur quantum dots. In step S2, the sulfur quantum dots obtained in step S1 are mixed with 4.1 wt% hydrogen peroxide solution at a volume ratio of 1.5:2 for 5 minutes and then purified by rotary evaporation for 20 minutes to remove excess unreacted hydrogen peroxide and obtain purified sulfur quantum dots. The purified sulfur quantum dots are then freeze-dried and stored in powder form. When used, they are dissolved in purified water to the target concentration to prepare sulfur quantum dot fluorescent probes.

2. The application of the sulfur quantum dot fluorescent probe according to claim 1 in tryptophan detection, characterized in that, In vitro quantitative detection includes the following steps: Step S1: The sulfur quantum dot fluorescent probe, PBS buffer, and tryptophan solutions of different gradient concentrations are mixed at a volume ratio of 2:1:

2. After irradiation with ultraviolet light, the fluorescence intensity is measured and a standard curve is plotted. The equation of the standard curve is: y=4.3x-55.2, R²=0.9735, where x is the tryptophan concentration, y is the luminescence intensity of the sulfur quantum dot fluorescent probe, the linear range is 12~40μmol / L, and the detection limit is 4.35μmol / L. In step S2, sulfur quantum dot fluorescent probe and PBS buffer are added to the test solution, wherein the volume ratio of sulfur quantum dot fluorescent probe, PBS buffer and test solution is 2:1:

2. After irradiation with ultraviolet light, the fluorescence intensity is measured, and the concentration of tryptophan is calculated based on the measured fluorescence intensity and the standard curve equation obtained in step S1.

3. The application of the sulfur quantum dot fluorescent probe according to claim 2 in tryptophan detection, characterized in that, The concentration of the sulfur quantum dot fluorescent probe in steps S1 and S2 is 1.477 mg / mL.

4. The application of the sulfur quantum dot fluorescent probe according to claim 2 in tryptophan detection, characterized in that, The ultraviolet light wavelength in steps S1 and S2 is 365nm, the power is 20~90W, and the ultraviolet light irradiation time is 5~30min.

5. The application of the sulfur quantum dot fluorescent probe according to claim 2 in tryptophan detection, characterized in that, The excitation wavelength used to measure fluorescence intensity in steps S1 and S2 is 360 nm.

6. The application of the sulfur quantum dot fluorescent probe according to claim 1 in tryptophan detection, characterized in that, Intracellular in situ qualitative detection includes the following steps: Cells were seeded in confocal culture dishes. After the cells matured, sulfur quantum dot fluorescent probes and PBS buffer were added to the culture dishes. The volume ratio of sulfur quantum dot fluorescent probes, PBS buffer and cell test liquid was 2:1:

2. After irradiation with ultraviolet light, the cells were incubated at 37°C for 30 min. After removal, the culture medium was discarded, and the cells were washed three times with buffer before cell imaging.

7. The application of the sulfur quantum dot fluorescent probe according to claim 1 in tryptophan detection, characterized in that, In situ quantitative detection of intracellular contents includes the following steps: Step S1: Seed cells in confocal culture dishes and culture them in an incubator until mature. Then, treat them with different gradient concentrations of tryptophan. Add sulfur quantum dot fluorescent probes and PBS buffer to the cells treated with tryptophan. The volume ratio of sulfur quantum dot fluorescent probes, PBS buffer and cell test liquid is 2:1:

2. After irradiation with ultraviolet light, incubate at 37°C for 30 min, remove the cells, discard the culture medium, wash them three times with PBS buffer, and then perform cell imaging. Measure the fluorescence intensity and plot a standard curve. In step S2, sulfur quantum dot fluorescent probe and PBS buffer are added to the cells to be tested. The volume ratio of sulfur quantum dot fluorescent probe, PBS buffer and cell test liquid is 2:1:

2. After irradiation with ultraviolet light, the cells are incubated at 37 °C for 30 min. Cell imaging is performed and fluorescence intensity is measured. The concentration of tryptophan in the cells is calculated based on the measured fluorescence intensity and the standard curve equation obtained in step S1.

8. The application of a sulfur quantum dot fluorescent probe according to claim 6 or 7 in tryptophan detection, characterized in that, The concentration of the sulfur quantum dot fluorescent probe was 1.477 mg / mL.

9. The application of a sulfur quantum dot fluorescent probe according to claim 6 or 7 in tryptophan detection, characterized in that, The ultraviolet light wavelength is 365nm, the power is 30~50W, and the ultraviolet light irradiation time is 15min.

10. The application of a sulfur quantum dot fluorescent probe according to claim 6 or 7 in tryptophan detection, characterized in that, The excitation wavelength used for cell imaging was 408 nm.

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