阅读说明：本技术 一种具有大斯托克斯位移特征的酪氨酸酶识别近红外荧光探针及其制备方法与应用 (Tyrosinase recognition near-infrared fluorescent probe with large Stokes displacement characteristics and preparation method and application thereof ) 是由 王晓春 马翠萍 于 2021-09-30 设计创作，主要内容包括：本发明公开了一种具有大斯托克斯位移特征的酪氨酸酶识别近红外荧光探针的制备与应用。本发明的近红外荧光探针是EQR-TYR,其结构式为式I。EQR-TYR本身无荧光,但可以选择性的与TYR发生荧光打开反应,由于具有较大的斯托克斯位移(130nm),大大降低了系统背景荧光的干扰,提高了对TYR活性检测的灵敏度。同时,各种常见干扰离子或物质对TYR荧光检测几乎无干扰。因此,EQR-TYR适用于对TYR进行高选择性和高灵敏度的荧光检测。(The invention discloses preparation and application of a tyrosinase recognition near-infrared fluorescent probe with a large Stokes displacement characteristic. The near-infrared fluorescent probe is EQR-TYR, and the structural formula of the near-infrared fluorescent probe is shown as a formula I. The EQR-TYR has no fluorescence, but can selectively generate fluorescence opening reaction with TYR, and due to the fact that the EQR-TYR has larger Stokes shift (130nm), interference of system background fluorescence is greatly reduced, and sensitivity of TYR activity detection is improved. Meanwhile, various common interfering ions or substances hardly interfere with the TYR fluorescence detection. Therefore, EQR-TYR is suitable for the fluorescence detection of TYR with high selectivity and high sensitivity.)

1. A compound of formula I:

2. a process for the preparation of a compound of formula I as claimed in claim 1, comprising the steps of:

1) reacting cyclohexanone and phosphorus tribromide to synthesize a compound 1;

2) reacting the compound 1 with 4-methoxy salicylaldehyde to generate a compound 2;

3) reacting 4-methylquinoline with iodoethane to generate a compound 3;

4) reacting a compound 2 with a compound 3 in anhydrous acetic anhydride to obtain a solid substance, and generating EQR shown in a formula II by the solid substance under the action of boron tribromide;

5) reacting EQR with 3-hydroxybenzyl bromide to obtain EQR-TYR shown as a formula I;

3. the method of claim 2, wherein:

in the step 1), the reaction of cyclohexanone and phosphorus tribromide is as follows: adding cyclohexanone into a mixed solution in which phosphorus tribromide, dimethylformamide and dichloromethane coexist, wherein the temperature of the mixed solution is 0 ℃, and then heating for reaction; in the reaction, the molar ratio of cyclohexanone to phosphorus tribromide is 1: 1.1; the volume ratio of the dimethylformamide to the dichloromethane is 0.224: 1; the reaction temperature is 20-25 ℃, and the reaction time is 12 hours;

in the step 2), the compound 1 and the 4-methoxysalicylaldehyde react in the presence of cesium carbonate, specifically: dissolving the compound 1 in dimethylformamide and 4-methoxysalicylaldehyde, and then adding cesium carbonate into the system; in the reaction, the molar ratio of the compound 1, the 4-methoxysalicylaldehyde to the cesium carbonate is 1.2: 1: 3; the reaction temperature is room temperature, and the reaction time is 24 hours;

in the step 3), the reaction of the 4-methylquinoline and the iodoethane is carried out in acetonitrile; in the reaction, the molar ratio of 4-methylquinoline to iodoethane is 1: 1.5; the reaction temperature is 80 ℃, and the reaction time is 12 hours;

in the step 4), the specific operation steps are as follows: firstly, dissolving a compound 2 and a compound 3 in anhydrous acetic anhydride to perform a first-step reaction to obtain an intermediate product, then dropwise adding boron tribromide into a dichloromethane solution of the intermediate product under the condition of vigorous stirring, and heating to room temperature to perform a second-step reaction to obtain EQR; in the first step of reaction, the molar ratio of the compound 2 to the compound 3 is 1: 1.25, the reaction temperature is 140 ℃, and the reaction time is 12 hours; in the second step of reaction, the molar ratio of the intermediate product to boron tribromide is 1: 10, the reaction temperature is room temperature, and the reaction time is 12 hours;

in the step 5), the EQR and the 3-hydroxybenzyl bromide react under the protection of nitrogen; the reaction is carried out in a solvent, wherein the solvent is acetonitrile; the reaction is specifically operated as follows: dropwise and slowly adding the acetonitrile solution of the 3-hydroxybenzyl bromide into the acetonitrile solution in which the EQR and the potassium carbonate coexist to carry out reaction; in the reaction, the mol ratio of EQR, 3-hydroxybenzyl bromide and potassium carbonate is 1: 3: 2; the reaction temperature was 60 ℃ and the reaction time was 24 hours.

4. The production method according to claim 2 or 3, characterized in that: the method also comprises the step of purifying the obtained EQR-TYR, which comprises the following steps: cooling the system containing EQR-TYR to room temperature, adding dichloromethane, and extracting with saturated aqueous sodium chloride solution for three times; collecting an organic phase, drying the organic phase by using anhydrous sodium sulfate, and removing the solvent by rotary evaporation; purifying by column chromatography, wherein the eluent is a mixed solution of dichloromethane and methanol at a volume ratio of 100:1, and finally obtaining a purple solid product EQR-TYR.

5. A fluorescent probe characterized in that: the fluorescent probe is the compound of claim 1.

6. A chemical sensor, characterized by: the chemical sensor comprising the compound of claim 1.

7. The fluorescent probe of claim 5 or the chemical sensor of claim 6, wherein: the fluorescent probe or the chemical sensor is used for fluorescence imaging for detecting TYR or TYR.

8. Use of a compound according to claim 1, or a fluorescent probe according to claim 5 or 7, or a chemical sensor according to claim 6 or 7 for the detection of TYR or for fluorescence imaging of TYR.

9. Use of a compound according to claim 1 in at least one of the following 1) -2):

1) the application of the fluorescent probe as a fluorescent probe or a fluorescent probe for detecting TYR;

2) the application in the preparation of a chemical sensor or a chemical sensor for detecting TYR.

10. Use according to claim 8 or 9, characterized in that: the object to which the fluorescent probe or the chemical sensor is applied is a cell or a living organism.

Technical Field

The invention belongs to the technical field of analysis and detection, and particularly relates to a tyrosinase recognition near-infrared fluorescent probe EQR-TYR with a large Stokes displacement characteristic, and a preparation method and application thereof.

Background

Tyrosinase (TYR) is a cytoplasmic melanocyte differentiation protein that plays a crucial role in the biosynthesis of melanin by oxidizing tyrosine to quinone compounds. TYR can cause neurotoxicity and neurodegeneration of dopamine, thereby inducing parkinson's disease. Meanwhile, abnormal expression of TYR in cells will lead to excess or deficiency of melanin in the body, resulting in skin diseases such as melanoma, skin pigmentation, albinism or vitiligo. Melanoma is one of the most serious skin cancers, has high malignant transformation rate, and has high early malignant metastasis rate and high lethality rate. At present, TYR is recognized as an important biomarker for melanoma diagnosis and prognosis. Therefore, the development of a highly selective and sensitive monitoring technology for the activity of TYR is crucial, which not only facilitates the deepening of understanding of the physiological and pathological functions of TYR, but also plays an extremely important role in the diagnosis, pre-diagnosis and treatment monitoring of TYR-related diseases.

The traditional detection method for the TYR activity comprises a colorimetric method, an electrochemical method, a photoelectrochemical method, a Raman spectroscopy method and the like. However, the above methods suffer from various drawbacks such as long time consumption, high time and labor consumption, low spatial and temporal resolution, poor interference resistance, and poor water solubility, especially background interference from cells, which affect the sensitivity and accuracy of the methods. Compared with the traditional method, the chemical sensor is gradually applied to the detection of TYR activity due to the advantages of high sensitivity, high selectivity, anti-interference capability, simple operation, nondestructive detection of cells, tissues and organisms and the like in combination with the laser confocal imaging technology. However, the current chemical sensor for detecting the TYR activity has the defects of small Stokes shift, long detection time (3h), high susceptibility to interference of active oxygen species, over-high detection limit, poor water solubility and the like. The task of developing new chemical sensors that overcome the above-mentioned drawbacks is therefore particularly urgent.

Disclosure of Invention

An object of the present invention is to provide a near-infrared chemical sensor molecule-EQR-TYR capable of detecting TYR activity with high selectivity and high sensitivity.

The EQR-TYR provided by the invention has the structure as shown in formula I:

the EQR-TYR salt can be specifically an iodide salt.

Another objective of the invention is to provide a preparation method of EQR-TYR shown in formula I.

The preparation method of EQR-TYR provided by the invention comprises the following steps (the preparation flow chart is shown in figure 1):

1) reacting cyclohexanone and phosphorus tribromide to synthesize a compound 1 (2-bromo-1-cyclohexene-1-formaldehyde); 2) reacting the compound 1 with 4-methoxy salicylaldehyde to generate a compound 2(2, 3-dihydro-6-methoxy-1H-xanthene-4-formaldehyde); 3) reacting 4-methylquinoline with iodoethane to generate a compound 3; 4) reacting a compound 2 with a compound 3 in anhydrous acetic anhydride to obtain a solid substance, and generating EQR shown in a formula II by the solid substance under the action of boron tribromide; 5) and reacting the EQR with 3-hydroxybenzyl bromide to obtain the EQR-TYR shown in the formula I.

In the step 1), the cyclohexanone and the phosphorus tribromide are reacted by adding the cyclohexanone to a mixed solution (the solution temperature is 0 ℃) of phosphorus tribromide, dimethylformamide and dichloromethane, and then heating for reaction. In the reaction, the molar ratio of cyclohexanone to phosphorus tribromide is 1: 1.1; the volume ratio of the dimethylformamide to the dichloromethane is 0.224: 1. the reaction temperature was room temperature (20-25 ℃) and the reaction time was 12 hours.

In step 2) of the above method, the compound 1 and 4-methoxysalicylaldehyde react in the presence of cesium carbonate, specifically: dissolving the compound 1 in dimethylformamide and 4-methoxysalicylaldehyde, and adding cesium carbonate into the system. In the reaction, the molar ratio of the compound 1, the 4-methoxysalicylaldehyde to the cesium carbonate is 1.2: 1: 3. the reaction temperature was room temperature (20-25 ℃) and the reaction time was 24 hours.

In step 3) of the above process, the reaction of 4-methylquinoline and iodoethane is carried out in acetonitrile. In the reaction, the molar ratio of 4-methylquinoline to iodoethane is 1: 1.5. the reaction temperature was 80 ℃ and the reaction time was 12 hours.

In the step 4), the method comprises the following specific operation steps: firstly, dissolving a compound 2 and a compound 3 in anhydrous acetic anhydride to perform a first-step reaction to obtain an intermediate product, then dropwise adding boron tribromide into a dichloromethane solution (the system temperature is 0 ℃) of the intermediate product under the condition of vigorous stirring, and heating to room temperature (20-25 ℃) to perform a second-step reaction, thereby obtaining the EQR. In the first step of reaction, the molar ratio of the compound 2 to the compound 3 is 1: 1.25, the reaction temperature is 140 ℃, and the reaction time is 12 hours; in the second step of reaction, the molar ratio of the intermediate product to boron tribromide is 1: the reaction temperature is room temperature (20-25 ℃), and the reaction time is 12 hours.

In the step 5), the EQR and the 3-hydroxybenzyl bromide are reacted under the protection of nitrogen. The reaction is carried out in a solvent, which may be acetonitrile. The reaction is specifically operated as follows: the acetonitrile solution of the 3-hydroxybenzyl bromide is slowly added dropwise into the acetonitrile solution of the EQR and the potassium carbonate for reaction. In the reaction, the mol ratio of EQR, 3-hydroxybenzyl bromide and potassium carbonate is 1: 3: 2. the reaction temperature was 60 ℃ and the reaction time was 24 hours.

The method further comprises the step of purifying the obtained EQR-TYR, and the method comprises the following specific steps: the EQR-TYR containing system was cooled to room temperature (20-25 deg.C), 20mL of dichloromethane was added and extracted three times with saturated aqueous sodium chloride; collecting an organic phase, drying the organic phase by using anhydrous sodium sulfate, and removing the solvent by rotary evaporation; purifying by column chromatography, eluting with dichloromethane/methanol (100:1, v/v), and collecting the purple solid product EQR-TYR.

It is a further object of the invention to provide the use of EQR-TYR.

The EQR-TYR provided by the invention is selected from at least one of the following 1) to 7):

1) a fluorescent probe made of EQR-TYR;

2) the application of EQR-TYR as a fluorescent probe or a fluorescent probe for detecting TYR;

3) a chemical sensor comprising EQR-TYR;

4) the application of EQR-TYR in preparing a chemical sensor or preparing a chemical sensor for detecting TYR;

5) the application of EQR-TYR in detecting TYR;

6) the use of the fluorescent probe of 1) above in the detection of TYR;

7) use of the chemical sensor of 3) above for detecting TYR.

Wherein, 1) the fluorescent probe and 3) the chemical sensor can be used for the fluorescence imaging of TYR or the detection of TYR.

The object to which the fluorescent probe or the chemical sensor is applied may be a cell or a living organism. Specifically, the method comprises the following steps: the fluorescent imaging method can be applied to fluorescent imaging of TYR in mouse melanoma cells B16F 10; it can also be applied to fluorescence imaging of TYR in a mouse living body.

The inventor of the invention proves through experiments that: the EQR-TYR has no fluorescence, but can selectively perform fluorescence opening reaction with TYR to generate a system with excellent optical performance, and the emission wavelength is in a near infrared region (740nm), and generates 130nm Stokes shift compared with the excitation wavelength of 610 nm. The characteristics can greatly reduce the interference of background fluorescence of a biological system and improve the detection sensitivity and selectivity of TYR. Therefore, EQR-TYR is suitable for the highly selective and sensitive detection of TYR, which can be performed by fluorescence spectroscopy.

When the fluorescence spectroscopy is adopted and EQR-TYR is used as a detection reagent to detect TYR, the detection limit of the method is 0.035U/mL, which shows that the EQR-TYR has good response sensitivity to TYR and is superior to the sensitivity of the reported TYR fluorescence detection method at present. Meanwhile, EQR-TYR has good selectivity for fluorescent response of TYR, and common ions and interfering species (such as K)⁺、Ca²⁺、Mg²⁺、Cys、GSH、GLU、Urea、Ascorbic acid、Creatinine、Alkaline phosphatase、BSA、H₂O₂、·OH、¹O₂、O₂·^-、ClO^-And ONOO^-Etc.) has little interference to the measurement of TYR, thus being capable of eliminating the interference of a plurality of interfering ions and species to the detection result and having high detection specificity. In addition, when the EQR-TYR is used for detecting TYR, the detection sensitivity is high, and only a trace of sample is needed to finish the detectionThus, the application range of the method is widened.

Drawings

FIG. 1 is a flow chart of the preparation of EQR-TYR.

FIG. 2 is a NMR spectrum of EQR.

FIG. 3 is a NMR carbon spectrum of EQR.

FIG. 4 is a high resolution mass spectrum of EQR.

FIG. 5 is a NMR spectrum of EQR-TYR.

FIG. 6 is a NMR carbon spectrum of EQR-TYR.

FIG. 7 is a high resolution mass spectrum of EQR-TYR.

FIG. 8 is a graph of the fluorescence spectra of EQR-TYR and EQR (a); fluorescence intensity change diagrams (b) of a coexistent EQR-TYR and TYR (50U/mL) system and a single EQR-TYR system at different pH values; fluorescence intensity changes of the coexisting system of EQR-TYR and tyrosinase and the single EQR-TYR system at different temperatures (c); the system response speed (d) under the coexistence of EQR-TYR and tyrosinase with different concentrations; graph (e) showing the change in fluorescence intensity at 740nm of the coexisting system of EQR-TYR and different concentrations of TYR; and (f) is a linear relation graph between the fluorescence intensity of the EQR-TYR and different concentrations of TYR in the 740nm coexisting system and the TYR concentration.

FIG. 9 shows the selectivity of EQR-TYR for tyrosinase detection (a); influence of different concentrations of aspergillic acid on fluorescence intensity of an EQR-TYR and TYR (50U/mL) coexisting system (b); inhibition effect of different concentrations of aspergillic acid on EQR-TYR and EQR fluorescence intensity (c).

FIG. 10 shows MTT assay results for EQR-TYR cytotoxicity (a); EQR-TYR for B16F10 cell and HeLa cell imaging (B); EQR-TYR was used for mouse imaging experiments (c).

Detailed Description

The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention. The examples provided below serve as a guide for further modifications by a person skilled in the art and do not constitute a limitation of the invention in any way.

The experimental procedures in the following examples, unless otherwise indicated, are conventional and are carried out according to the techniques or conditions described in the literature in the field or according to the instructions of the products. Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1 preparation of the chemical sensor molecule EQR-TYR

The reaction scheme is shown in figure 1, and the specific method is as follows:

4.48mL of dimethylformamide and 20mL of dichloromethane were mixed and cooled to 0 ℃. Under vigorous stirring, 5mL of phosphorus tribromide was added dropwise to the system. After 30 minutes, 4.9mL of cyclohexanone was added to the system. The reaction was stirred at room temperature (20-25 ℃ C.) for 12 hours, and then poured into 30mL of pure water and neutralized with sodium bicarbonate. The aqueous phase was extracted three times with 60mL of dichloromethane. The organic phases were combined and dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to give a yellow oily solid (compound 1, 2-bromo-1-cyclohexene-1-carbaldehyde). The compound 1 was used in the next reaction without purification.

Compound 1(0.204g, 1.08mmol) was taken and dissolved in 6mL dimethylformamide and 4-methoxysalicylaldehyde (0.137g, 0.9 mmol). Cesium carbonate (0.88g, 2.7mmol) was added to the system with vigorous stirring. The reaction was stirred at room temperature (20-25 ℃ C.) for 24 hours, then 60mL of methylene chloride was added to the system, and washed with water three times (20 mL each), the organic phases were combined and dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation to obtain a solid. Purification by column chromatography with dichloromethane as eluent gave compound 2 as a bright yellow colour (63% yield).

4-methylquinoline (0.48g, 3.35mmol) and iodoethane (0.78g, 5mmol) were dissolved in 25mL acetonitrile, heated to 80 ℃ and reacted under reflux for 12 hours. And (3) performing rotary evaporation to remove the solvent to obtain a solid, performing ultrasonic treatment by using diethyl ether, performing suction filtration, washing the filtered product by using the diethyl ether for three times, and performing vacuum drying to obtain a green solid compound 3 (the yield is 88%), wherein the green solid compound can be directly used for the next reaction without further treatment.

Compound 2(0.4mmol) and compound 3(0.5mmol) were dissolved in 10mL of anhydrous acetic anhydride and heated under reflux for 12 hours. After the reaction is completed, the solvent is evaporated to dryness, the solid substance is redissolved by dichloromethane, the solid substance is washed by water for three times, the water phase is discarded after liquid separation, and the solid substance is obtained after the organic phase solvent is dried by spinning. The above solid material (0.25mmol) was dissolved in 10mL of dichloromethane, and the solution was cooled to 0 ℃. Under vigorous stirring, 2.5mmoL of boron tribromide was added dropwise to the system. After completion of the dropwise addition, the temperature was returned to room temperature (20-25 ℃ C.), and the reaction was stirred for 12 hours. After the reaction was completed, the reaction system was poured into ice water, neutralized to neutrality with a saturated sodium bicarbonate solution, and extracted with dichloromethane. Purification was performed by column chromatography using dichloromethane/methanol (15:1, v/v) as eluent. Finally, the product EQR is obtained as a purple solid with a yield of 70%.

1.0mmol of EQR was dissolved in 20mL of acetonitrile and 2mmol of potassium carbonate was added. Under the protection of nitrogen, the system is heated to 60 ℃ and stirred for reaction for 10 minutes. 3mmol of 3-hydroxybenzyl bromide was dissolved in 2mL of acetonitrile and slowly added dropwise to the aforementioned reaction system, and the reaction was stirred at 60 ℃ for 24 hours. The system was cooled to room temperature (20-25 ℃), 20mL of dichloromethane was added, and extraction was performed three times with saturated aqueous sodium chloride solution. The organic phase was collected, dried over anhydrous sodium sulfate and the solvent was removed by rotary evaporation. Purification was performed by column chromatography using dichloromethane/methanol (100:1, v/v) as eluent. Finally, the purple solid product EQR-TYR is obtained with the yield of 42%.

Nuclear magnetic identification of EQR:¹H NMR(300MHz,DMSO-d₆)δ10.44(s,1H),9.04(d,1H),8.79(d,1H),8.48–8.21(m,3H),8.15–8.06(m,1H),7.91–7.81(m,1H),7.27(d,1H),7.13(d,1H),6.84(s,2H),6.64(d,1H),4.87(q,2H),2.67(t,2H),2.56(t,2H),1.76(t,2H),1.53(t,3H)。¹³C-NMR(75MHz,DMSO-d₆) δ 159.92,154.46,153.62,152.33,145.23,137.56,134.42,128.22,127.70,127.08,126.24,125.89,125.82,118.58,114.05,113.69,113.54,112.20,112.02,102.09,89.79,50.92,28.75,24.28,20.36, 15.03. The nuclear magnetic hydrogen spectrum and the carbon spectrum are shown in fig. 2 and fig. 3, respectively. The instrument model is as follows: the Varian Mercury 300BB NMR System (300M). High resolution mass spectrometry identification of EQR: m/z 382.1804[ C₂₆H₂₄NO₂]⁺(calcd.382.1802), the results are shown in FIG. 4. The above results indicate that the obtained compound was identified as the target compound EQR.

Nuclear magnetic identification results of EQR-TYR:¹H-NMR(300MHz,DMSO-d₆)δ10.41(s,1H),9.04(d,1H),8.81(d,1H),8.45(d,1H),8.34(d,2H),7.87(t,1H),7.30(d,1H),7.15(d,1H),6.92–6.84(m,3H),6.77–6.71(m,3H),6.64(d,1H),4.88(q,2H),3.74(s,2H),2.70(t,2H),2.57(t,2H),1.78(t,2H),1.53(t,3H).¹³C-NMR(75MHz,DMSO-d₆) δ 159.89,154.48,153.62,152.45,147.63,146.61,145.24,137.69,137.57,134.36,128.19,127.67,126.98,126.18,125.89,120.85,119.05,118.49,115.58,114.06,113.71,113.59,112.55,112.19,112.00,102.15,55.61,50.98,28.71,24.29,20.35, 14.91. The nuclear magnetic hydrogen spectrum and the carbon spectrum are shown in fig. 5 and fig. 6, respectively. The instrument model is as follows: the Varian Mercury 300BB NMR System (300M). And (3) identifying the result of the EQR-TYR by high-resolution mass spectrometry: MS m/z 488.2208[ C ]₃₃H₃₀NO₃]⁺(calcd.488.2220). The results are shown in FIG. 7. The above results indicate that the obtained compound is indeed the target compound EQR-TYR.

Example 2 fluorescence detection of TYR by EQR-TYR as analytical reagent

1. Sensitivity of fluorescence detection of TYR by EQR-TYR

In a 5mL plastic EP tube, the appropriate amount of TYR was dissolved in 3mL of 0.1M PBS buffer solution (pH 7.4), then 20. mu.L of the reagent EQR-TYR in dimethyl sulfoxide (DMSO) at a concentration of 1.0mM was added, and the appropriate volumes of 0.1M PBS buffer solution (pH 7.4) were added to give TYR concentrations of 0, 1.0, 5.0, 10, 20, 30, 40 and 50U/mL and EQR-TYR concentrations of 5. mu.M in each test system. After keeping the reaction system at 37 ℃ for 1 hour, the reaction system was transferred to a 1cm quartz cell, and the fluorescence spectrum of the reaction system was measured.

FIG. 8(a) is a graph showing the fluorescence response of EQR-TYR to TYR. The excitation wavelength and emission wavelength of the system were 610nm and 740nm, respectively. As can be seen in fig. 8 (a): the EQR-TYR does not have fluorescence, and when the TYR is added into the system, the fluorescence intensity of the system is obviously increased, which shows that the EQR-TYR has better fluorescence response to the TYR. FIGS. 8(b) and 8(c) are graphs showing the change in fluorescence intensity at different pH and different temperatures in a coexistent EQR-TYR and TYR (50U/mL) system and an EQR-TYR alone system, respectively. As can be seen from fig. 8(b) and (c): when the pH is in the range of 4.0-10.0 and the temperature is 20-45 ℃, the EQR-TYR is almost free of fluorescence, and the fluorescence intensity of the EQR-TYR is not changed along with the change of the pH and the temperature. When TYR exists, the fluorescence intensity of the system is obviously increased at the pH value of 7.4 and the temperature of 37 ℃, which indicates that EQR-TYR is suitable for the fluorescence recognition of TYR under physiological conditions. FIG. 8(d) is a result of a fluorescence kinetic study of a coexisting system of EQR-TYR and TYR. The fluorescence intensity of the coexisting EQR-TYR and TYR systems increased with time within 1 hour at different TYR concentrations (5U/mL, 20U/mL, 30U/mL and 50U/mL), while the fluorescence intensity of the systems reached a maximum and remained almost unchanged after 1 hour. The above facts indicate that the optimal reaction time for fluorescence detection of TYR using EQR-TYR is 1 hour.

FIGS. 8(e) and 8(f) are graphs of the change in fluorescence intensity at 740nm for the coexisting system EQR-TYR with different concentrations of TYR and a linear relationship between the fluorescence intensity at 740nm and the concentration of TYR for the coexisting system EQR-TYR with different concentrations of TYR. As shown in FIG. 8(e), the fluorescence intensity of the reaction system gradually increased with the increase in the TYR concentration. Fig. 8(f) shows: within the range of 1.0-50U/mL, the TYR concentration and the fluorescence intensity of the system are in a linear relation, the linear equation is that DeltaF is 33.35C (U/mL) +43.82, and the detection limit of the method is 0.035U/mL calculated by dividing the standard deviation of blank signals by the slope of a standard curve by 3 times. The results show that the EQR-TYR has excellent performance and can realize high-sensitivity fluorescent detection of TYR.

2. Specificity of fluorescent detection of TYR by EQR-TYR

Taking a plurality of EP tubes at the same time, carrying out the similar operation as above, except that the TYR addition is changed into the TYR addition of various common interfering ions or substances, and the samples corresponding to No. 1-19 are: blank, K⁺(100mM)、Ca²⁺(2.5mM)、Mg²⁺(2.5mM)、Cys(1.0mM)、GSH(1.0mM)、GLU(10mM)、Urea(10mM)、Ascorbic acid(1.0mM)、Creatinine(10mM)、Alkaline phosphatase(20U/L)、BSA(100mM)，H₂O₂、·OH、¹O₂、O₂·^-And ClO^-(all concentrations are 100. mu.M), ONOO^-(10. mu.M) and TYR (50U/mL), the results of the tests are shown in FIG. 9 (a). As can be seen in fig. 9 (a): sample No. 1-18The product produced no significant fluorescence response, whereas the addition of 50U/mL TYR (sample No. 19) produced intense fluorescence. The above phenomena are illustrated: the interference ions do not influence the EQR-TYR as an analysis reagent to perform fluorescence detection on TYR, and the EQR-TYR has high selectivity on the fluorescence detection of TYR as a detection reagent.

3. Inhibition effect of aspergillic acid on fluorescence intensity of EQR-TYR and TYR coexisting system

FIGS. 9(b) and 9(c) show the effect of different concentrations of aspergillic acid on the fluorescence intensity of the coexisting system of EQR-TYR (5. mu.M) and TYR (50U/mL) and the inhibitory effect of different concentrations of aspergillic acid on the fluorescence intensity of EQR-TYR and EQR, respectively. The results in FIG. 9(b) show: the EQR-TYR has almost no fluorescence, and when the EQR-TYR and the TYR coexist, the system has stronger fluorescence intensity. When 100. mu.M of aspergillic acid was added to the coexisting EQR-TYR and TYR systems, the fluorescence intensity of the systems was reduced by about 80%; when the concentration of the kojic acid is increased to 150 mu M, the fluorescence intensity of the system is reduced by about 95%. In addition, fig. 9(c) shows: the fluorescence intensity of EQR-TYR and EQR is hardly influenced by the aspergillic acid within the concentration range of 0-200 mu M. The above results illustrate that: the aspergillic acid can effectively inhibit the activity of TYR.

4. Performance comparison of EQR-TYR with other related TYR chemical sensors

The fluorescence detection performance of EQR-TYR versus TYR was summarized and compared to the performance of the relevant chemical sensors in the literature for detecting TYR, and the results are shown in table 1. As can be seen from Table 1, the fluorescence detection response of EQR-TYR to TYR is fast. Importantly, when the EQR-TYR is used for detecting the TYR, the TYR has larger Stokes shift (130nm), the interference of background fluorescence can be effectively reduced, and the detection sensitivity is improved, and the detection limit of the method reaches 0.035U/mL, which is superior to the reported chemical sensor.

TABLE 1 comparison of EQR-TYR with TYR chemical sensors in literature

Reference documents:

1、Chai,Z.,Shang,J.,Shi,W.,Li,X.H.,Ma,H.M.Increase of tyrosinase activity at the wound site in zebrafish imaged by a new fluorescent probe.Chem.Commun.2021,57:2764-2767

2、Hua,S.S.,Wang,T.L.,Zou,J.J.,Zhou,Z.,Lu,C.F.,Nie,J.Q.,Ma,C.,Yang,G.C.,Chen,Z.X.,Zhang,Y.X.,Sun,Q.,Fei,Q.,Ren,J.,Wang,F.Y.Highly chemoselective fluorescent probe for the detection of tyrosinase in living cells and zebrafish model.Sens.Actuators B:Chem.2019,283:873-880

3、Park,S.Y.,Won,M.,Kim,J.S.,Lee,M.H.Ratiometric fluorescent probe for monitoring tyrosinase activity in melanosomes of melanoma cancer cells.Sens.Actuators B:Chem.2020,319:128306

4、Wu,X.F.,Li,L.H.,Shi,W.,Gong,Q.Y.,Ma,H.M.Near-infrared fluorescent probe with new recognition moiety for specific detection of tyrosinase activity:design,synthesis,and application in living cells and zebrafish.Angew.Chem.Int.Ed.2016,55:14728-14732

5、Yang,S.,Jiang,J.X.,Zhou,A.X.,Zhou,Y.B.,Ye,W.L.,Cao,D.S.,Yang,R.H.Substrate-photocaged enzymatic fluorogenic probe enabling sequential activation for light-controllable monitoring of intracellular tyrosinase activity,Anal.Chem.2020,92:7194-7199

6、Zhang,P.,Li,S.,Fu,C.,Zhang,Q.,Xiao,Y.,Ding,C.A colorimetric and near-infrared ratiometric fluorescent probe for the determination of endogenous tyrosinase activity based on cyanine aggregation.Analyst,2019,144:5472-5478

example 3 fluorescent imaging Studies of TYR in cell and mouse samples with EQR-TYR as reagents

The MTT cytotoxicity test of EQR-TYR was carried out. The MTT experiment was performed by culturing cells after treatment with different concentrations of EQR-TYR (0-50. mu.M) for 24 hours, and the results are shown in FIG. 10 (a). From FIG. 10(a), it can be seen that the survival rate of the cells is greater than 80%, indicating that EQR-TYR has low cytotoxicity and can be applied to cell imaging studies.

Takes a mouse melanoma cell B16F10 cell and a normal cell Hela cell as a researchAnd (5) researching the object, and verifying the feasibility of the EQR-TYR as a fluorescence imaging reagent. B16F10 cell and Hela cell culture and imaging: B16F10 cells and Hela cells in a sterile culture dish were cultured in DMEM medium containing 10% embryonic serum for 24h at 37 ℃ while maintaining 5% CO₂Culturing atmosphere; B16F10 cells and Hela cells were transferred to 6-well plates overnight; after being washed by HEPES buffer solution (pH 7.4), adding a certain volume of EQR-TYR solution to ensure that the final concentration of the EQR-TYR is 5 mu M, culturing for 1 hour, washing by the HEPES buffer solution (pH 7.4) again, and carrying out laser confocal microscopic imaging; after adding a kojic acid solution to B16F10 cells to make the concentration of kojic acid in the system 1.0mM and continuing the culture for 1 hour, laser confocal microscopy was performed by rinsing with a HEPES buffer solution (pH 7.4), and the results are shown in fig. 10 (B). As can be seen from fig. 10 (b): when B16F10 cells were incubated with EQR-TYR for 1 hour, a distinct red color appeared in the cells, whereas when incubation was continued with additional aspergillic acid, the fluorescence intensity in the cells was significantly reduced compared to that when incubated with EQR-TYR alone. Hela cells served as a control group, and no obvious fluorescence was generated in the cells after the cells were cultured by EQR-TYR. The above experimental results prove that: EQR-TYR can be used as a reagent to realize fluorescence imaging of B16F10 cells. Mouse culture and imaging: normal Hela cells and melanoma cells B16F10 cells were injected into the left and right sides of experimental mice, respectively. Five days later, the EQR-TYR solution was injected intravenously into the mice, and one hour later, the effect of fluorescence imaging was observed. FIG. 10(c) shows the fluorescence imaging results of TYR in mice. From FIG. 10(c) we can see that: when EQR-TYR was injected into the body of mice, where melanoma cells B16F10 were injected on the right side of the body, a distinct red fluorescence was produced, while the fluorescence intensity was very weak where normal Hela cells were injected on the left side of the body. The above phenomena are illustrated: the EQR-TYR can be applied to fluorescence imaging of TYR in organisms, and has good application prospect in improving the research level of TYR generation mechanism in organisms and promoting the pre-diagnosis and accurate treatment of TYR related diseases.