Application of a polarity-sensitive fluorescent probe in the preparation of non-alcoholic fatty liver disease detection reagents

Abstract

The present invention relates to the field of fluorescent probe technology, and specifically to the use of a polarity-sensitive fluorescent probe in the preparation of a non-alcoholic fatty liver disease detection reagent. The chemical name of the polarity-sensitive fluorescent probe is 6-(dimethylamino)-2-naphthaldehyde; the non-alcoholic fatty liver disease detection reagent has the following functions: (1) imaging of lipid droplets in living cells; (2) qualitative and quantitative detection of cell lipid droplet polarity; (3) distinguishing between normal cells and cancer cells; (4) dynamically monitoring the lipid droplet formation process; (5) distinguishing and detecting different degrees of non-alcoholic fatty liver tissue. The present invention provides a very promising tool for studying the polarity of lipid droplets of different types of cells and distinguishing and detecting different degrees of non-alcoholic fatty liver tissue, which is helpful for timely diagnosis of early non-alcoholic fatty liver disease.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent probes, and in particular to application of a polarity-sensitive fluorescent probe in the preparation of a non-alcoholic fatty liver disease detection reagent. Background Art

[0002] As an important intracellular organelle, lipid droplets are not only key structures for energy storage, but also play an important role in various biological processes. Abnormal intracellular lipid storage can lead to various metabolic diseases, such as obesity, fatty liver, cardiovascular disease and diabetes. The polarity of lipid droplets can affect the attachment and activity of various signaling molecules, such as fatty acid and cholesterol transport and metabolic signaling. Therefore, abnormal lipid droplet polarity often indicates the onset of disease. For example, reduced lipid droplet polarity is a key feedback to cell carcinogenesis.

[0003] In addition, the metabolic imbalance between lipid droplet synthesis and degradation can lead to the accumulation of large amounts of lipid deposits, which is a characteristic of hepatocytes in patients with fatty liver disease. In general, non-alcoholic fatty liver disease can be cured as long as it is diagnosed early and treated in time. Current detection methods for non-alcoholic fatty liver disease include ultrasound imaging, fatty liver index, liver tissue biopsy, and magnetic resonance imaging. However, these detection methods are usually limited by sensitivity, time, and price. Lipid droplet polarity is closely related to non-alcoholic fatty liver disease. The lipid content in non-alcoholic fatty liver disease increases and the polarity of lipid droplets decreases. Therefore, monitoring the polarity of lipid droplets is very important for revealing the role of lipid droplets in cell metabolism and disease, especially for detecting cell carcinogenesis and non-alcoholic fatty liver disease.

[0004] In recent years, fluorescent probes have been widely used in biological detection due to their advantages such as easy operation, in situ and real-time non-destructive detection, but there are few reports on the detection of non-alcoholic fatty liver disease. In addition, most of the existing fluorescent probes with polarity sensitivity on the market have poor biocompatibility, low photostability and insufficient polarity sensitivity.

[0005] Therefore, there is an urgent need to develop a method for efficiently detecting lipid droplet polarity using fluorescent probes in order to provide early warning and timely treatment for non-alcoholic fatty liver disease. Summary of the invention

[0006] In view of the technical problem that the prior art lacks fluorescent probes for detecting the degree of non-alcoholic fatty liver disease, the present invention provides a polarity-sensitive fluorescent probe for use in preparing a non-alcoholic fatty liver disease detection reagent. The present invention provides a promising tool for studying the polarity of lipid droplets in different types of cells and distinguishing and detecting non-alcoholic fatty liver tissues of different degrees, which helps to timely diagnose early non-alcoholic fatty liver disease.

[0007] The technical solution of the present invention is as follows:

[0008] A polarity-sensitive fluorescent probe is used in the preparation of a non-alcoholic fatty liver disease detection reagent. The chemical name of the polarity-sensitive fluorescent probe is 6-(dimethylamino)-2-naphthaldehyde, and the structural formula is shown in the following formula (I):

[0009] .

[0010] Furthermore, the non-alcoholic fatty liver disease detection reagent has the following functions:

[0011] (1) Imaging of lipid droplets in living cells;

[0012] (2) Qualitative and quantitative detection of cellular lipid droplet polarity;

[0013] (3) Differentiate between normal cells and cancer cells;

[0014] (4) Dynamic monitoring of lipid droplet formation;

[0015] (5) Differentiate and detect different degrees of non-alcoholic fatty liver tissue.

[0016] Furthermore, the living cells in (1) are cancer cells or normal cells.

[0017] Furthermore, the cancer cells are preferably HepG2 or HeLa cells.

[0018] Furthermore, the normal cells are preferably MIHA or RAW cells.

[0019] Furthermore, the imaging in (1) is two-dimensional imaging or three-dimensional imaging.

[0020] Furthermore, (3) specifically diagnoses cancer cells based on changes in emission peak wavelength by in situ spectral scanning of cells stained with 6-(dimethylamino)-2-naphthaldehyde.

[0021] Furthermore, (5) confocal microscopy imaging technology was used to perform fluorescence diagnosis of non-alcoholic fatty liver tissue stained with 6-(dimethylamino)-2-naphthaldehyde.

[0022] The beneficial effects of the present invention are:

[0023] 6-(dimethylamino)-2-naphthaldehyde contains both N,N-dimethyl groups and aldehyde groups, which can serve as electron-donating groups and electron-withdrawing groups, respectively, to form a D-π-A structure, thereby giving it an intramolecular charge transfer (ICT) effect. Based on this, the present invention utilizes 6-(dimethylamino)-2-naphthaldehyde to exhibit excellent polarity response behavior in both in vitro and cell imaging experiments, and can specifically image lipid droplets in living cells, quantitatively detect the polarity characteristics of lipid droplets in different types of cells, and achieve the distinction and detection of different degrees of non-alcoholic fatty liver tissue.

[0024] 6-(Dimethylamino)-2-naphthaldehyde can stain lipid droplets in cells and provide fluorescent images that correspond one to one with lipid droplets. It can clearly image lipid droplets in living cells with higher specificity and lower signal-to-noise ratio than the commercial lipid droplet probe Nile Red, and can detect the polarity of lipid droplets. It is of great significance for tracking lipid droplet fluctuations with high fidelity and monitoring the occurrence of certain lipid droplet-related diseases, and it brings great convenience to pathological studies related to lipid droplet changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The absorption spectra (a) and fluorescence spectra (b) of 6-(dimethylamino)-2-naphthaldehyde in solvents of different polarities.

[0027] Figure 2 It is the HOMO and LUMO energy level diagram of 6-(dimethylamino)-2-naphthaldehyde.

[0028] Figure 3 The absorption spectrum and normalized fluorescence spectrum (a) and log[I (490-540)nm / I (430-480)nm ]right E T (b) The fitting curve of (30).

[0029] Figure 4 These are the MTT staining results after incubating HepG2, HeLa, RAW and MIHA cells with different concentrations of 6-(dimethylamino)-2-naphthaldehyde for 24 hours.

[0030] Figure 5 Fluorescence image (a), DIC image (b) and merged image (c) of HepG2 cells stained with 6-(dimethylamino)-2-naphthaldehyde, and local enlarged images (d)-(f) corresponding to the white square areas in (a)-(c).

[0031] Figure 6 Fluorescence images of HepG2 cells (a) and HeLa cells (b) stained with 6-(dimethylamino)-2-naphthaldehyde and Nile red.

[0032] Figure 7 These are top and side views of three-dimensional confocal imaging of HeLa cells stained with 6-(dimethylamino)-2-naphthaldehyde and Nile red.

[0033] Figure 8 Fluorescence images of HepG2, HeLa, RAW and MIHA cells stained with 6-(dimethylamino)-2-naphthaldehyde (a) and fluorescence intensity bar graphs of the red and green channels (b).

[0034] Fig. 9 The fluorescence image and in situ emission spectrum of 6-(dimethylamino)-2-naphthaldehyde in HepG2 cells (a) and the fluorescence image and in situ emission spectrum in MIHA cells (b).

[0035] Fig.10 The fluorescence image (a), fluorescence intensity line graph (b) and Western Blot detection band graph (c) of HepG2 cells stained with 6-(dimethylamino)-2-naphthaldehyde after incubation with free fatty acids.

[0036] Fig.11 The fluorescence images of 6-(dimethylamino)-2-naphthaldehyde staining different degrees of non-alcoholic fatty liver disease (a), the fluorescence intensity bar graph of the red channel and the green channel (b), and the fluorescence intensity ratio line graph of the red channel and the green channel (c). DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] The chemical name of the polarity-sensitive fluorescent probe used in the present invention is 6-(dimethylamino)-2-naphthaldehyde, CAS No. 173471-71-1, and the structural formula is shown in the following formula (I):

[0039] .

[0040] 6-(Dimethylamino)-2-naphthaldehyde was prepared as follows:

[0041] ;

[0042] The compound of formula (II) (6-hydroxy-2-naphthaldehyde, 1.553 g, 9.02 mmol), Na2S2O5 (4.24 g, 18.1 mmol), NaOH (2.378 g, 45.4 mmol), (CH3)2NH (3.04 g, 40.6 mmol) and H2O (80 mL) were added to a 100 mL hydrothermal reactor, and after being fully mixed, the mixture was reacted at 145°C for 48 hours. After the reaction was completed, the mixture was extracted with CH2Cl2, the solvent of the organic phase was evaporated to dryness, and then the crude product was purified by column chromatography to obtain the compound of formula (I), i.e., 6-(dimethylamino)-2-naphthaldehyde.

[0043] In other embodiments, 6-(dimethylamino)-2-naphthaldehyde can also be purchased from commercial sources.

[0044] Example 1 Polar response behavior of 6-(dimethylamino)-2-naphthaldehyde

[0045] 6-(Dimethylamino)-2-naphthaldehyde was added to solvents of different polarities at a concentration of 10 μM, and its absorption spectra were detected. The results are as follows: Figure 1 As shown in (a), 6-(dimethylamino)-2-naphthaldehyde has the largest absorption peak near 380nm. The fluorescence spectra of 6-(dimethylamino)-2-naphthaldehyde solutions in the above-mentioned solvents with different polarities were detected with an excitation wavelength of 380nm. The results are as follows: Figure 1 As shown in (b), the fluorescence intensity of 6-(dimethylamino)-2-naphthaldehyde gradually decreases with the increase of solvent polarity, which is a very typical manifestation of its intramolecular charge transfer (ICT) characteristics. Figure 2 As shown, the HOMO energy level of 6-(dimethylamino)-2-naphthaldehyde is -5.39eV, and the electron cloud in the HOMO orbit is mainly concentrated on the N,N-dimethyl and naphthalene rings; the LUMO energy level is -1.703eV, and the electron cloud in the LUMO orbit is mainly concentrated on the naphthalene ring and the aldehyde group; the energy gap is 3.696eV. When 6-(dimethylamino)-2-naphthaldehyde is in different solvents, this electron density distribution feature is very conducive to the transfer of electrons in the N,N-dimethyl group to the aldehyde group to varying degrees. This property is necessary for the polarity sensitivity of 6-(dimethylamino)-2-naphthaldehyde to lipid droplets.

[0046] according to Figure 1 The detection results are plotted to obtain the absorption spectrum of 6-(dimethylamino)-2-naphthaldehyde (such as Figure 3 The normalized fluorescence spectrum (shown as dashed line in (a)) and the Figure 3As shown in the solid line in (a), it can be seen that as the solvent changes from low polarity (THF) to high polarity (H2O), the maximum emission peak of 6-(dimethylamino)-2-naphthaldehyde gradually increases from 435nm to 526nm.

[0047] To further quantify the polarity, the ratio of the fluorescence intensity of 6-(dimethylamino)-2-naphthaldehyde at 490-540 nm and 430-480 nm (I (490-540)nm / I (430-480)nm ) and the polarity index of various solvents E T (30) is fitted, and the polarity index E T (30) is a measure of the solvent ionization power (polarity). The linear function obtained by fitting is as follows Figure 3 As shown in (b), it can be seen that I (490-540)nm / I (430-480)nm It gradually increases with the increase of solvent polarity.

[0048] comprehensive Figures 1 to 3 As a result, 6-(dimethylamino)-2-naphthaldehyde has a solvatochromic property and shows an excellent linear relationship with the solvent polarity.

[0049] Example 2 Cytotoxicity of 6-(dimethylamino)-2-naphthaldehyde

[0050] HepG2, HeLa, RAW and MIHA cells were cultured in high-glucose DMEM medium supplemented with 10% fetal bovine serum (FBS) and 1% penicillin / streptomycin in an oxygen-enriched atmosphere with 5% carbon dioxide at 37°C. HepG2, HeLa, RAW and MIHA cells were incubated with different concentrations of 6-(dimethylamino)-2-naphthaldehyde in the culture medium for 24 hours, and then the cytotoxicity of 6-(dimethylamino)-2-naphthaldehyde was identified using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reagent.

[0051] The results are as follows Figure 4 As shown in the figure, after incubation with different concentrations of 6-(dimethylamino)-2-naphthaldehyde for 24 hours, the viability of HepG2, HeLa, RAW and MIHA cells was still above 86%. Therefore, the cytotoxicity of 6-(dimethylamino)-2-naphthaldehyde at short time and low dose can be ignored.

[0052] Example 3 Staining ability of 6-(dimethylamino)-2-naphthaldehyde on living cells

[0053] HepG2 cells were incubated with 2 μM 6-(dimethylamino)-2-naphthaldehyde in culture medium for 15 min, and the stained HeLa cells were observed under a fluorescence microscope. The excitation wavelength of the green channel was 405 nm, and the emission wavelength was 430-540 nm. Figure 5 (a)-(c) show the fluorescence image, DIC image and merged image of HeLa cells respectively. Figure 5 The white line in the lower right corner of (a) is a 20 μm ruler. Figure 5 As can be seen in (a)-(c), the fluorescence of 6-(dimethylamino)-2-naphthaldehyde appears randomly in the cells like "water droplets".

[0054] To further analyze the targeting position of 6-(dimethylamino)-2-naphthaldehyde, Figure 5 The white square area in (a)-(c) is enlarged, and the results are as follows Figure 5 As shown in (d)-(f), Figure 5 The white line in the lower right corner of (d) is 1 μm. Since the refractive index of lipid droplets is higher than that of other structures in the cell, Figure 5 The black dots in (e) represent lipid droplets. Figure 5 It can be seen from (f) that Figure 5 The green fluorescence in (d) and Figure 5 The black dots in (e) merged well, indicating that 6-(dimethylamino)-2-naphthaldehyde specifically stained lipid droplets in living cells.

[0055] To further confirm that the staining site of 6-(dimethylamino)-2-naphthaldehyde is lipid droplets, confocal experiments were performed using the commercial lipid droplet probe Nile Red. The excitation wavelength of 6-(dimethylamino)-2-naphthaldehyde was 405nm, and the emission wavelength was 430-540nm; the excitation wavelength of Nile Red was 530nm, and the emission wavelength was 580-630nm. The experiments were performed in HepG2 and HeLa cells, respectively. Figure 6 (a) is a fluorescent image of HepG2 cells stained with 6-(dimethylamino)-2-naphthaldehyde and Nile red, respectively. The white line in the figure is a 20 μm ruler. Figure 6 (b) is a fluorescent image of HeLa cells stained with 6-(dimethylamino)-2-naphthaldehyde and Nile red, respectively. The white line in the figure is a 10μm ruler. Figure 6 It can be seen that in HepG2 and HeLa cells, the green channel of 6-(dimethylamino)-2-naphthaldehyde completely overlaps with the red channel of Nile Red, and their colocalization coefficients are 0.95 and 0.90, respectively. In summary, 6-(dimethylamino)-2-naphthaldehyde can specifically target lipid droplets in living cells.

[0056] The three-dimensional images of Hela cells stained with 6-(dimethylamino)-2-naphthaldehyde and the three-dimensional images of Hela cells stained with Nile red were constructed based on 30 two-dimensional confocal images. The top view and side view of the three-dimensional images of the two stained cells are shown in Figure 1. Figure 7 As shown in the figure, the nonspecific staining of Nile red produces a very strong fluorescent background in the three-dimensional image, which obviously obscures the lipid droplets; compared with Nile red, the spatial distribution of lipid droplets stained with 6-(dimethylamino)-2-naphthaldehyde is more clearly visible in the three-dimensional image. Therefore, 6-(dimethylamino)-2-naphthaldehyde shows excellent practicality in three-dimensional confocal imaging.

[0057] Example 4 Detection of lipid droplet polarity using 6-(dimethylamino)-2-naphthaldehyde

[0058] HepG2, HeLa, RAW and MIHA cells were stained with 6-(dimethylamino)-2-naphthaldehyde, and fluorescence was obtained from two channels, 430-480nm and 490-540nm. The excitation wavelengths of the green and red channels were both 405nm. Figure 8 As shown in (a) (white line is 20 μm scale), HeLa and HepG2 cells showed brighter fluorescence and a large number of lipid droplets in the green channel, while little fluorescence was found in the red channel; however, the opposite phenomenon was shown in normal RAW and MIHA cells. The corresponding ratio image was calculated based on the fluorescence intensity of the two channels, and the pseudo color map was applied to the ratio image. The pseudo color gradually changed from yellow in HepG2 and HeLa cells to red in normal RAW and MIHA cells, indicating that normal cell polarity increased. Figure 8 (b) shows the fluorescence intensity of 6-(dimethylamino)-2-naphthaldehyde in the green and red channels.

[0059] The fitting equation y = 0.082-4.706x obtained in Example 1 was used to calculate the lipid droplet polarity in HepG2, HeLa, RAW and MIHA cells. E T (30) values ​​were 45.2, 46.4, 53.4 and 56.3 respectively. E T (30) is higher than that of lipid droplets in cancer cells. E T (30) is about 10 higher. To further investigate this fact, in situ spectral scanning was performed on HepG2 cells and normal MIHA cells stained with 6-(dimethylamino)-2-naphthaldehyde. Fig. 9 As shown (white line is 20 μm scale), the maximum emission peak of 6-(dimethylamino)-2-naphthaldehyde in HepG2 cells is 446 nm, while the maximum emission peak in MIHA cells is 455 nm. Figure 1 (b) Results: The polarity of lipid droplets in HepG2 and MIHA cells is similar to that of tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO), respectively.

[0060] The above experimental results show that the polarity of lipid droplets in cancer cells is lower than that in normal cells. Although some reports can distinguish normal cells from cancer cells by the fluorescence intensity of lipid droplets, the fluorescence intensity is easily affected by factors such as the intensity of the excitation light and the concentration of the fluorescent probe. The change of the emission peak based on in situ spectral scanning imaging can well avoid these interferences, highlighting the superiority of 6-(dimethylamino)-2-naphthaldehyde in cancer cell diagnosis.

[0061] Therefore, 6-(dimethylamino)-2-naphthaldehyde can not only calculate the lipid droplet polarity of different types of cells, but also distinguish normal cells from cancer cells by detecting lipid droplet polarity.

[0062] Example 5 Dynamic monitoring of lipid droplets in living cells using 6-(dimethylamino)-2-naphthaldehyde

[0063] HepG2 cells were first stained with 2 μM 6-(dimethylamino)-2-naphthaldehyde for 15 minutes, and then these HepG2 cells were incubated with free fatty acids to induce the production of lipid droplets in HepG2 cells to study the ability of 6-(dimethylamino)-2-naphthaldehyde to dynamically monitor lipid droplets in living cells. Fig.10 (a) shows the fluorescence images of HepG2 cells without incubation (Control group) and HepG2 cells at different incubation times. The white line in the figure is a 20μm ruler. The excitation wavelength of 6-(dimethylamino)-2-naphthaldehyde is 405nm, and the emission wavelength is 430-540nm. As the incubation time increases, the fluorescence intensity generated by lipid droplets gradually increases. Fig.10 The quantitative results of the fluorescence intensity of HepG2 cells without incubation and HepG2 cells at different incubation times in (b) also confirmed this point.

[0064] In addition, Western Blot experiments were performed on HepG2 cells without incubation and HepG2 cells at different incubation times to study the expression of early lipid induction marker genes (including C / EBPα, C / EBPβ, ACACA and SERBF) and late lipid formation marker genes (including PPARγ and FASN), and β-actin was used as a loading control. Fig.10 As shown in (c), the expression of these early lipid induction marker genes was the highest at 2 hours, and the expression gradually weakened with the extension of incubation time. The expression of late lipid formation marker genes gradually increased with the extension of incubation time, indicating that the lipid content increased. These Western Blot experimental results are consistent with Fig.10 (a)-(b) are consistent, further proving that 6-(dimethylamino)-2-naphthaldehyde has the ability to dynamically monitor the process of lipid droplet formation.

[0065] Example 6 6-(Dimethylamino)-2-naphthaldehyde to detect different degrees of non-alcoholic fatty liver

[0066] Compared with normal liver, nonalcoholic fatty liver showed lower polarity, which may be attributed to the lower polarity of lipid droplets in fatty liver. Therefore, the polarity reaction sensitive to 6-(dimethylamino)-2-naphthaldehyde can be used to detect early nonalcoholic fatty liver and its lipid droplet polarity.

[0067] First, mice with different degrees of fatty liver were obtained by feeding mice with high-fat diet for 4, 8, 12 and 16 weeks. The liver tissues of mice with different degrees of fatty liver were stained with H&E, and normal mice fed with standard diet were used as control (Control). The results showed that with the increase of high-fat diet feeding time, the number of vacuoles in the liver tissues of mice induced by high-fat diet gradually increased ( Fig.11 (a)). A large number of fat vacuoles were observed in the liver tissue of mice induced by a high-fat diet for 16 weeks, verifying the successful establishment of the fatty liver model. The livers of normal mice and fatty liver mice were stained with 6-(dimethylamino)-2-naphthaldehyde, revealing that the lipid droplets in the liver increased significantly with the duration of the high-fat diet ( Fig.11 In (a), the white line is a 25 μm ruler, the excitation wavelength of the green channel is 405 nm, and the emission wavelength is 430-540 nm; the excitation wavelength of the red channel is 405 nm, and the emission wavelength is 490-540 nm). Fig.11 Middle (b), Fig.11 As shown in (c), the fluorescence intensity of the red channel and the green channel gradually increased, but the fluorescence ratio decreased, which was attributed to the decrease in lipid droplet polarity in the liver. At the same time, the corresponding ratio image ( Fig.11 In (a), a pseudo-color map is applied to the ratio image. As the duration of high-fat feeding increases, the pseudo-color of the lipid droplets gradually changes from green to yellow and finally to red, also indicating that the polarity of the lipid droplets gradually decreases.

[0068] The fitting equation y = 0.082-4.706x obtained in Example 1 was used to calculate the polarity of lipid droplets in fatty livers of different degrees. The polarity of lipid droplets in the livers of normal mice in the control group and mice fed a high-fat diet for 16 weeks was E T(30) The values ​​gradually decreased from 57.5 to 56.5, 52.4, 51.2, and 50.0, further demonstrating that the polarity of lipid droplets in non-alcoholic fatty liver is smaller than that in normal liver. In addition, the size of lipid droplets in the tissues of mice with different degrees of fatty liver induced by a high-fat diet was approximately 5-30 μm, which was larger than the size of lipid droplets in the liver tissues of normal mice (0.5-2 μm). These results indicate that 6-(dimethylamino)-2-naphthaldehyde also has good potential for early detection of non-alcoholic fatty liver.

[0069] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. Application of a polarity-sensitive fluorescent probe in the preparation of a non-alcoholic fatty liver disease detection reagent, characterized in that: The chemical name of the polarity-sensitive fluorescent probe is 6-(dimethylamino)-2-naphthaldehyde, and its structural formula is shown in the following formula (I): 。 2. The use according to claim 1, characterized in that The non-alcoholic fatty liver disease test reagent has the following functions: (1) Imaging lipid droplets in living cells; (2) Qualitative and quantitative detection of cellular lipid droplet polarity; (3) Differentiate between normal cells and cancer cells; (4) Dynamic monitoring of lipid droplet formation; (5) Differentiate and detect different degrees of non-alcoholic fatty liver tissue.

3. The use according to claim 2, characterized in that The living cells in (1) are cancer cells or normal cells.

4. The use according to claim 3, characterized in that Cancer cells are HepG2 or HeLa cells.

5. The use according to claim 3, characterized in that Normal cells are MIHA or RAW cells.

6. The use according to claim 2, characterized in that (1) The imaging is two-dimensional imaging or three-dimensional imaging.

7. The use according to claim 2, characterized in that (3) Specifically, cancer cells are diagnosed based on changes in emission peak wavelength by in situ spectral scanning of cells stained with 6-(dimethylamino)-2-naphthaldehyde.

8. The use according to claim 2, characterized in that (5) Fluorescence diagnosis of non-alcoholic fatty liver tissue stained with 6-(dimethylamino)-2-naphthaldehyde was performed using confocal microscopy imaging technology.

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