阅读说明：本技术 一种β-半乳糖苷酶活力检测试剂盒和检测方法 (Beta-galactosidase activity detection kit and detection method ) 是由 马英新 于 2019-02-20 设计创作，主要内容包括：本申请涉及一种基于比率荧光法的β-半乳糖苷酶活力检测试剂盒,包括二-β-D-吡喃半乳糖苷(FDG)和CdZnTeS量子点溶于反应缓冲液中所得的反应试剂,其中FDG的浓度为5-15ng/mL,CdZnTeS量子点的浓度为15-25nmol/mL。该检测试剂盒还可包括标准色卡和/或β-半乳糖苷酶标准品。本申请还提供了采用该β-半乳糖苷酶活力检测试剂盒检测样品中的β-半乳糖苷酶活力的方法。本发明的β-半乳糖苷酶活力检测试剂盒和检测方法提供了基于荧光比率的变化的β-半乳糖苷酶活力可视化检测平台,能便捷地对待测样品中的β-半乳糖苷酶活力进行定性或定量检测。(The application relates to a beta-galactosidase activity detection kit based on a ratio fluorescence method, which comprises a reaction reagent obtained by dissolving di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots in a reaction buffer solution, wherein the concentration of the FDG is 5-15ng/mL, and the concentration of the CdZnTeS quantum dots is 15-25 nmol/mL. The detection kit can also comprise a standard color card and/or a beta-galactosidase standard. The application also provides a method for detecting the activity of the beta-galactosidase in a sample by adopting the beta-galactosidase activity detection kit. The beta-galactosidase activity detection kit and the detection method provide a visual detection platform for the beta-galactosidase activity based on the change of the fluorescence ratio, and can conveniently carry out qualitative or quantitative detection on the beta-galactosidase activity in a sample to be detected.)

1. The beta-galactosidase activity detection kit based on the ratiometric fluorescence method is characterized by comprising a reaction reagent obtained by dissolving di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots in a reaction buffer solution, wherein the concentration of the FDG is 5-15ng/mL, and the concentration of the CdZnTeS quantum dots is 15-25 nmol/mL.

2. The detection kit according to claim 1, wherein in the reaction reagent, the concentration of the FDG is 10ng/mL, and the concentration of the CdZnTeS quantum dot is 20 nmol/mL.

3. The detection kit of claim 1, wherein the reaction buffer is Tris buffer or PBS buffer, and the pH is 7.5-8.5.

4. The test kit according to any one of claims 1 to 3, further comprising a standard color chart, wherein the standard color chart is prepared by the following method:

(A) preparing a reaction reagent in which di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots are dissolved in a Tris buffer solution, wherein the concentration of the FDG is 10ng/mL, the concentration of the CdZnTeS quantum dots is 20nmol/mL, and the pH value of the reaction buffer solution is 8.0;

(B) taking an aliquot of the reaction reagent, adding or not adding a beta-galactosidase standard substance into the reaction reagent to ensure that the concentration of the beta-galactosidase is 0, 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500U/L to obtain a series of reaction mixtures;

(C) incubating the series of reaction mixtures at 32 ℃ for 60 minutes to perform an enzymatic reaction, resulting in a series of enzymatic reactants;

(D) exciting the series of enzymatic reactants with an excitation wavelength of 480nm to display a series of emitted fluorescent colors and acquiring images of the series of emitted fluorescent colors of the series of enzymatic reactants;

(E) the standard color card was prepared using the series of images emitting fluorescent colors in order of β -galactosidase concentration.

5. The test kit of any one of claims 1-3, wherein the test kit further comprises a β -galactosidase standard.

6. A method for the non-diagnostic detection of β -galactosidase activity based on ratiometric fluorescence, said method comprising the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) incubating the sample with a reaction reagent in the beta-galactosidase activity detecting kit according to any one of claims 1-3 to perform an enzymatic reaction;

(3) exciting the enzymatic reactant with an excitation wavelength of 480nm to exhibit an emission fluorescent color;

(4) and judging the activity of the beta-galactosidase in the sample according to the emission fluorescence color, wherein the more red the emission fluorescence color is, the smaller the activity of the beta-galactosidase is, and the more green the emission fluorescence color is, the larger the activity of the beta-galactosidase is.

7. A method for the non-diagnostic detection of β -galactosidase activity based on ratiometric fluorescence, said method comprising the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) incubating the sample with a reaction reagent in the beta-galactosidase activity detecting kit according to claim 4 to perform an enzymatic reaction;

(3) exciting the enzymatic reactant with an excitation wavelength of 480nm to exhibit an emission fluorescent color;

(4) comparing the emitted fluorescence color with the color of the standard color card in the beta-galactosidase activity detection kit according to claim 4, and determining the value of the beta-galactosidase activity in the sample.

8. A method for the non-diagnostic detection of β -galactosidase activity based on ratiometric fluorescence, said method comprising the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) preparing a series of standard solutions containing beta-galactosidase with the concentration of 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500U/L by using the beta-galactosidase standard in the beta-galactosidase activity detection kit according to claim 5;

(3) incubating the sample and the series of standard solutions, respectively, with a reaction reagent in the beta-galactosidase activity detecting kit according to claim 5 to perform an enzymatic reaction;

(4) exciting each enzymatic reactant separately with an excitation wavelength of 480nm, and measuring the ratio of the intensity of the fluorescence emitted at an emission wavelength of 512nm to the intensity of the fluorescence emitted at an emission wavelength of 632nm, i.e., the F512/F632 ratio;

(5) plotting the F512/F632 ratio obtained by the series of standard solutions to the corresponding beta-galactosidase concentration to obtain a beta-galactosidase activity standard curve;

(6) and according to the obtained F512/F632 ratio of the sample, calculating the value of the beta-galactosidase activity in the sample according to the beta-galactosidase activity standard curve.

9. The detection method according to any one of claims 6 to 8, wherein the temperature of the enzymatic reaction is 30 to 40 ℃ and the time is 50 to 70 minutes.

10. The detection method according to claim 10, wherein the temperature of the enzymatic reaction is 32 ℃ and the time is 60 minutes.

Technical Field

The invention relates to the technical field of biochemical detection, in particular to a beta-galactosidase activity detection kit based on a ratio fluorescence method and a detection method for detecting beta-galactosidase by adopting the detection kit.

Background

The lacZ gene encodes beta-galactosidase (beta-Gal), a glycoside hydrolase, which catalyzes the hydrolysis of beta-galactosides, removing galactose residues from sphingolipids, glycoproteins, gangliosides, and keratin sulfate. The beta-galactosidase has been widely used in the processing of dairy products in the food industry, can hydrolyze lactose in the dairy products into galactose, reduce the phosphorus content of the lactose in the dairy products, and improve the digestibility of the dairy products, and can be used for producing low-lactose milk and galactooligosaccharides. Meanwhile, in the biomedical field, β -galactosidase has been found to be overexpressed in cancers such as cell senescence and primary ovarian cancer. Cancer is currently a significant cause of death in the population worldwide, accurate diagnosis is crucial for cancer therapy, and overexpressed enzymes are often one of the essential markers in cancer diagnosis. Therefore, the activity of beta-galactosidase needs to be detected in the fields of food industry, medical diagnosis industry and biological research.

In recent years, several methods for the detection of β -galactosidase activity have been developed, such as colorimetry, magnetic resonance imaging, surface enhanced raman scattering, and fluorescence. Fluorescence methods have attracted considerable interest because of their simplicity, sensitivity, high selectivity and non-invasiveness. However, the developed fluorescence method still has some limitations, such as single wavelength emission, low quantum yield, poor light stability, and the like, and especially has poor visualization and inconvenient use. Therefore, the present invention still needs a convenient method for detecting the activity of beta-galactosidase.

Disclosure of Invention

The invention aims to overcome the problem of poor visualization of the existing beta-galactosidase fluorescence detection method, and provides a beta-galactosidase activity detection kit based on a ratio fluorescence method and a method for detecting beta-galactosidase by using the detection kit.

Therefore, in a first aspect, the invention provides a beta-galactosidase activity detection kit based on a ratiometric fluorescence method, which is characterized by comprising a reaction reagent prepared by dissolving di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots in a reaction buffer solution, wherein the concentration of FDG is 5-15ng/mL, and the concentration of CdZnTeS quantum dots is 15-25 nmol/mL.

In embodiments of the invention, the concentration of FDG in the reaction reagents may be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15ng/mL and the concentration of CdZnTeS quantum dots may be 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nmol/mL. In a preferred embodiment of the invention, the concentration of FDG is 10ng/mL and the concentration of CdZnTeS quantum dots is 20nmol/mL in the reaction reagents.

Further, the reaction buffer is Tris buffer or PBS buffer. Preferably, the reaction buffer is Tris buffer. The pH of the reaction buffer is 7.5-8.5, e.g. 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4 or 8.5, preferably 8.0.

Further, the detection kit can also comprise a standard color card, and the standard color card is manufactured by the following method:

(A) preparing a reaction reagent in which di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots are dissolved in a Tris buffer solution, wherein the concentration of the FDG is 10ng/mL, the concentration of the CdZnTeS quantum dots is 20nmol/mL, and the pH value of the reaction buffer solution is 8.0;

(B) taking an aliquot of the reaction reagent, adding or not adding a beta-galactosidase standard substance to the reaction reagent to ensure that the concentration of the beta-galactosidase is 0, 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500U/L to obtain a series of reaction mixtures;

(C) incubating the series of reaction mixtures at 32 ℃ for 60 minutes to perform an enzymatic reaction, resulting in a series of enzymatic reactants;

(D) exciting the series of enzymatic reactants with an excitation wavelength of 480nm to display a series of emitted fluorescent colors, and acquiring images of the series of emitted fluorescent colors of the series of enzymatic reactants;

(E) the standard color chart was prepared using the series of images emitting fluorescent colors in order of β -galactosidase concentration.

Furthermore, the detection kit can also comprise a beta-galactosidase standard.

In a second aspect, the invention provides a method for detecting β -galactosidase activity based on ratiometric fluorescence.

In one embodiment of the second aspect of the invention, the detection method comprises the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) incubating the sample with the reaction reagent of the beta-galactosidase activity detecting kit of the first aspect to perform an enzymatic reaction;

(3) exciting the enzymatic reactant with an excitation wavelength of 480nm to exhibit an emission fluorescent color;

(4) and judging the activity of the beta-galactosidase in the sample according to the emission fluorescence color, wherein the more red the emission fluorescence color is, the smaller the activity of the beta-galactosidase is, the more green the emission fluorescence color is, and the larger the activity of the beta-galactosidase is.

In another embodiment of the second aspect of the invention, the detection method comprises the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) incubating the sample with the reagents of the beta-galactosidase activity detecting kit of the first aspect comprising a standard color chip to perform an enzymatic reaction;

(3) exciting the enzymatic reactant with an excitation wavelength of 480nm to exhibit an emission fluorescent color;

(4) comparing the emitted fluorescence color with the color of a standard color card in the beta-galactosidase activity detection kit, and judging the numerical value of the beta-galactosidase activity in the sample.

In yet another embodiment of the second aspect of the invention, the detection method comprises the steps of:

(1) providing a sample comprising a beta-galactosidase;

(2) preparing a series of standard solutions containing beta-galactosidase with a concentration of 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500U/L with the beta-galactosidase standard in the beta-galactosidase activity detection kit comprising the beta-galactosidase standard according to the first aspect;

(3) respectively incubating the sample and the series of standard solutions with a reaction reagent in the beta-galactosidase activity detection kit to perform enzymatic reaction;

(4) exciting each enzymatic reactant separately with an excitation wavelength of 480nm, and measuring the ratio of the intensity of the fluorescence emitted at an emission wavelength of 512nm to the intensity of the fluorescence emitted at an emission wavelength of 632nm, i.e., the F512/F632 ratio;

(5) plotting the F512/F632 ratio obtained by the series of standard solutions to the corresponding beta-galactosidase concentration to obtain a beta-galactosidase activity standard curve;

(6) and according to the obtained F512/F632 ratio of the sample, calculating the value of the beta-galactosidase activity in the sample according to the beta-galactosidase activity standard curve.

In the above detection method, the temperature of the enzymatic reaction is 30 to 40 ℃ and the time is 50 to 70 minutes. Preferably, the temperature of the enzymatic reaction is 32 ℃ and the time is 60 minutes.

The beta-galactosidase activity detection kit and the detection method based on the ratio fluorescence method can detect the activity of the beta-galactosidase in the fields of food industry, medical diagnosis industry and biological scientific research. In particular, the above-described detection method can be applied to the non-diagnostic detection of β -galactosidase activity.

The invention has the beneficial effects that:

the beta-galactosidase activity detection kit and the detection method adopt di-beta-D-galactopyranoside (FDG) as a substrate of beta-galactosidase and CdZnTeS quantum dots as a built-in fluorescence correction substance. In the presence of beta-galactosidase, the enzymolysis product fluorescein of FDG generates green fluorescence, the green fluorescence generated by different beta-galactosidase concentrations has different intensity, and the CdZnTeS quantum dots generate red fluorescence with fixed intensity, so that the fluorescence color generated by the enzymatic reaction system is the fluorescence mixed color of the green fluorescence and the red fluorescence. When the concentration of beta-galactosidase is lower, the mixed color is biased to red; with the increase of the concentration of the beta-galactosidase, the fluorescence mixed color gradually changes into orange, yellow and light yellow; at higher concentrations of beta-galactosidase, the mixed color is biased towards green. In the detection of a sample to be detected containing beta-galactosidase, after enzymatic reaction, the activity of the beta-galactosidase in the sample to be detected can be judged according to the fluorescence mixed color of the sample; according to the fluorescence mixed color of the sample and the combination of the standard color card of the activity of the beta-galactosidase, the numerical value of the activity of the beta-galactosidase in the sample to be detected can be judged; and (3) obtaining the value of the activity of the beta-galactosidase in the sample to be detected according to the fluorescence mixed color of the sample and the combination of the standard curve of the activity of the beta-galactosidase. Therefore, the invention develops a visual detection platform for the activity of the beta-galactosidase based on the change of the fluorescence ratio, and can conveniently carry out qualitative or quantitative detection on the activity of the beta-galactosidase in a sample to be detected.

Drawings

FIG. 1 schematically shows that non-fluorescent di-beta-D-galactopyranoside (FDG) produces green fluorescent fluorescein under the enzymatic action of beta-galactosidase (. beta. -Gal);

FIG. 2 schematically shows the preparation of CdZnTeS quantum dots;

fig. 3 shows the morphology of CdZnTeS quantum dots, where (a) shows TEM images of CdZnTeS quantum dots and (B) shows the size distribution of CdZnTeS quantum dots;

FIG. 4 is a fluorescence spectrum and photograph of a mixed solution of FDG and CdZnTeS quantum dots with or without the addition of β -galactosidase, showing a significant increase in green fluorescence at 512nm and stabilization of red fluorescence at 632nm after the enzymatic reaction with the addition of β -galactosidase ((+) β -Gal) compared to the addition of β -galactosidase ((-) β -Gal);

FIG. 5 shows the effect of (A) reaction temperature on the highest fluorescence intensity ratio (F512/F632) of the enzymatic reaction product fluorescein molecules of FDG to CdZnTeS quantum dots and (B) reaction time on the F512/F632 ratio in the beta-galactosidase activity assay;

fig. 6 shows the effect of β -galactosidase concentration on β -galactosidase activity detection, wherein (a) shows the fluorescence spectra of the mixed solution of FDG and CdZnTeS quantum dots when β -galactosidase of different concentrations was added, (B) shows the standard curve of β -galactosidase concentration versus F512/F632 ratio, indicating that within a certain β -galactosidase concentration range, β -galactosidase concentration and F512/F632 ratio are in a linear relationship, the error bars are obtained based on three repeated experiments, the excitation wavelength is 480 nm;

FIG. 7 shows the selectivity of the fluorescence ratio detection method for beta-galactosidase in accordance with the present invention for the detection of beta-galactosidase activity, wherein the experimental setup is as follows: a control blank (1) without any enzyme, beta-galactosidase (2), and trypsin (3), pepsin (4), lysozyme (5), tyrosinase (6), alkaline phosphatase (7), glucose oxidase (8), acetylcholinesterase (9) as beta-galactosidase analogues, was run for comparative experiments;

FIG. 8 shows the results of comparative experiments for detecting beta-galactosidase according to example 1 of the present invention, the beta-galactosidase ratio fluorescence detection method (A) and the pure fluorescence detection method (B), wherein the beta-galactosidase concentration is 0, 25, 100, 250, 750, 1000, 2000 and 2500U/L from left to right, respectively.

Detailed Description

The present invention is described in further detail below with reference to the attached drawing figures. It should be understood that these descriptions are for the purpose of illustrating the invention only, and are not intended to limit the invention in any way.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict, the present specification, including definitions, will control. The chemicals and equipment used herein are commercially available, unless otherwise indicated. The materials, methods, and examples used herein are illustrative only and are not intended to be limiting unless otherwise specified.

The term "sample comprising beta-galactosidase" as used herein refers to any sample in which beta-galactosidase activity needs to be measured, for example a food sample such as a dairy product or the like, or a biological sample such as interstitial fluid, cellular fluid or the like. Generally, food samples can be directly sampled, and biological samples can be obtained by disrupting biological tissues, cells to obtain interstitial or cellular fluids, as is well known in the art.

The term "β -galactosidase concentration" as used herein is expressed in units of β -galactosidase activity (U) per liter (L) of sample, and thus, the units of β -galactosidase concentration are U/L. The β -galactosidase activity units are defined as follows: taking o-nitrobenzene-beta-D-galactoside (ONPG) as a substrate, carrying out enzymolysis at the temperature of 32 ℃, and releasing the enzyme amount of L mu mol/L o-nitrophenol per minute, wherein the enzyme amount is defined as 1 enzyme activity unit.

The beta-galactosidase activity detection kit comprises di-beta-D-galactopyranoside (FDG) and CdZnTeS quantum dots, and the principle of detecting the beta-galactosidase is partially shown in figure 1. Di-beta-D-galactopyranoside (FDG) is a non-fluorescent substrate that can be specifically digested by beta-galactosidase. FDG does not fluoresce in the absence of beta-galactosidase; when beta-galactosidase is present, the enzymolysis product fluorescein emits green fluorescence with the wavelength of 512nm under the excitation wavelength of 480nm, and the intensity of the fluorescence increases along with the increase of the enzyme concentration. The CdZnTeS quantum dots emit red fluorescence with 632nm wavelength under 480nm excitation wavelength, and the fluorescence intensity is not influenced by enzyme concentration. When the beta-galactosidase is actually detected, the di-beta-D-galactopyranoside (FDG) in the beta-galactosidase activity detection kit is subjected to enzymolysis in the presence of the beta-galactosidase to generate green fluorescence, green fluorescence intensities generated by different beta-galactosidase concentrations are different, and the CdZnTeS quantum dots generate red fluorescence with fixed intensity, so that the fluorescence color generated by an enzymatic reaction system is mixed color of the green fluorescence and the red fluorescence. When the concentration of beta-galactosidase is lower, the mixed color is biased to red; with the increase of the concentration of the beta-galactosidase, the mixed color gradually changes into orange, yellow and light yellow; at higher concentrations of beta-galactosidase, the mixed color is biased towards green. Thus, the present invention develops a platform for the visual detection of β -galactosidase activity based on changes in the fluorescence ratio.

I. Experimental part

1. Materials and instruments

The following materials and instruments were used in the experiments:

Na₂TeO₃、CdCl₂·2.5H₂o and ZnCl₂Purchased from Shanghai Chemicals, Inc.

N-acetyl-L-cysteine (NAC), dimercaptosuccinic acid (DMSA), di-beta-D-galactopyranoside (FDG), and beta-galactosidase were purchased from Sigma-Aldrich, USA.

All chemical reagents were analytical reagent grade and used without further purification.

All solutions were prepared with ultra pure water obtained by Millipore water purification system (18.25M Ω cm,25 ℃).

Fluorescence spectra were obtained using an RF-6000PC spectrophotometer (Shimadzu, Japan).

Transmission Electron Microscopy (TEM) images were acquired on a JEOL (JEM 2100) electron microscope (japan). Preparation and characterization of CdZnTeS quantum dots

The CdZnTeS quantum dots are prepared by a one-pot method, as shown in figure 2. Briefly, CdCl is added₂·2.5H₂O(6.25mM)、ZnCl₂(6.25mM) and NAC (25mM) were dissolved in ultrapure water, and then NaOH solution (1.0M) was added thereto, and the pH was adjusted to 9.0 with stirring at room temperature to prepare Zn²⁺-Cd²⁺-a solution of NAC precursor. Then, a 0.1M NaOH solution of DMSA (1.25mM) and Na were mixed under vigorous stirring₂TeO₃(1.25mM) was added to the precursor solution and the pH was adjusted to 11.0. The resulting solution was transferred to a Teflon-lined stainless steel autoclave and heated at 200 ℃ for about 17 minutes. After cooling to room temperature, the solution is centrifuged at 8000rpm for 10 minutes to obtain a purified CdZnTeS quantum dot solution, and the solubility of the CdZnTeS quantum dots in the solution is good.

The morphology of the CdZnTeS quantum dots was characterized by Transmission Electron Microscopy (TEM). As shown in fig. 3, the TEM images showed that the CdZnTeS quantum dots had a uniform spherical morphology with an average size of about 5.5 nm. Studies of the optical properties of CdZnTeS quantum dots show that CdZnTeS quantum dots exhibit maximum emission at 632nm at an excitation wavelength of 480 nm.

3. Detection of beta-galactosidase

For the detection of β -galactosidase, FDG (10ng/mL), aqueous CdZnTeS quantum dots solution (20nm) and β -galactosidase solution were added to 20mM Tris buffer solution (pH 8.0). The total volume of the reaction reagents was 300. mu.L. The reaction reagents were incubated at 32 ℃ for 60 minutes. Then, a fluorescence spectrum was obtained at an excitation wavelength of 480 nm.

Fig. 4 shows a fluorescence spectrum and a photograph of a mixed solution of FDG and CdZnTeS quantum dots with or without the addition of β -galactosidase. As can be seen, the green fluorescence at 512nm wavelength increased significantly during the enzymatic reaction and the red fluorescence at 632nm wavelength stabilized when β -galactosidase was added, relative to when no β -galactosidase was added. Therefore, a mixture of CdZnTeS quantum dots with two independent emission peaks and fluorescein molecules can provide a ratiometric fluorescent signal for the visual detection of β -galactosidase.

4. Influence of reaction temperature and reaction time on detection of beta-galactosidase activity

In order to optimize the detection of beta-galactosidase, the influence of the reaction temperature and reaction time of the enzymatic reaction of beta-galactosidase with FDG to produce fluorescein molecules on the amount of fluorescein molecules produced was investigated. As shown in fig. 5A, during the enzymatic reaction of β -galactosidase, the fluorescence intensity of the fluorescein molecule increased with increasing reaction temperature, while the fluorescence intensity of the CdZnTeS quantum dot did not change, and the highest fluorescence intensity ratio of the fluorescein molecule and the CdZnTeS quantum dot was obtained at 32 ℃. As shown in fig. 5B, the fluorescence ratio of fluorescein molecules to CdZnTeS quantum dots increased with the extension of the reaction time during the enzymatic reaction of β -galactosidase, reaching a maximum at 60 minutes (fig. 5B). Therefore, 32 ℃ was selected as the optimum reaction temperature, and 60 minutes was selected as the optimum reaction time.

5. Influence of beta-galactosidase concentration on beta-galactosidase activity detection

Under the optimal experimental conditions of 32 ℃ reaction temperature and 60 min reaction time, fluorescence spectra of fluorescein molecules (10ng/mL) and CdZnTeS quantum dots (20nmol/mL) and beta-galactosidase with different concentrations are obtained, so as to study the influence of the beta-galactosidase concentration on the detection of the beta-galactosidase activity. As shown in FIG. 6A, the fluorescence intensity of fluorescein molecules at 512nm gradually increased with increasing β -galactosidase concentration. As shown in FIG. 6B, in the beta-galactosidase concentration range between 12.5 and 500U/L, the fluorescence ratio of fluorescein molecules and CdZnTeS quantum dots is in a linear relationship with the beta-galactosidase concentration, and the detection limit is determined to be 2.8U/L according to the 3 sigma equation.

6. Selectivity of beta-galactosidase activity detection

In order to prove the selectivity of the beta-galactosidase activity detection kit and the detection method based on the ratio fluorescence method to the beta-galactosidase activity detection, trypsin, pepsin, lysozyme, tyrosinase, alkaline phosphatase, glucose oxidase and acetylcholinesterase are used as beta-galactosidase analogs, a comparison experiment is carried out under the optimal experimental conditions of 10ng/mL fluorescein molecules, 20nmol/mL CdZnTeS quantum dots and 100U/L enzyme at the reaction temperature of 32 ℃ and the reaction time of 60 minutes, and a blank control group without any enzyme is arranged. The experimental results are shown in fig. 7, the fluorescence ratio of the fluorescein molecule to the CdZnTeS quantum dot in the presence of β -galactosidase is much higher than that of the fluorescein molecule to the CdZnTeS quantum dot in the presence of various β -galactosidase analogs, and the fluorescence ratio of the fluorescein molecule to the CdZnTeS quantum dot in the presence of various β -galactosidase analogs is similar to that of the fluorescein molecule to the CdZnTeS quantum dot in the blank control group. The result shows that the beta-galactosidase activity detection kit and the detection method based on the ratiometric fluorescence method have high selectivity for detecting the beta-galactosidase activity.

Example II