AU2021100186A4

AU2021100186A4 - Method and Kit for Fluorescence Detection of Small molecule Mycotoxin Based on Metal-organic Framework and Upconversion Nanoparticles

Info

Publication number: AU2021100186A4
Application number: AU2021100186A
Authority: AU
Inventors: Zhi Xian Gao; Dian Peng Han; Tie HAN; Shuang Li; Yuan Peng; Kang QIN; Shu Yue Ren; Yu Wang; Xu Dong Zhao
Original assignee: Tianjin Key Laboratory Of Risk Assessment And Control Technology For Environment And Food Safety Tia
Current assignee: Tianjin Key Laboratory Of Risk Assessment And Control Technology For Environment And Food Safety Tianjin Institute Of Environmental And Operational Medicine
Priority date: 2021-01-13
Filing date: 2021-01-13
Publication date: 2021-04-15
Anticipated expiration: 2029-01-13

Abstract

The present invention belongs to the field of small molecule detection, and particularly relates to a method and a kit for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles. The method comprises the following steps: S1. obtaining an upconversion nanoparticle probe modified with a small molecular mycotoxin aptamer; S2. synthesis and activation of MIL-101(Cr); S3. binding of the small molecule mycotoxin to the aptamer; and S4. signal detection: detecting a fluorescence signal of the product from the S3 by using a fluorescence spectrophotometer. Due to rare-earth-doped upconversion nanoparticles used in the present invention, the fluorescence intensity is stable and the background value is low. Compared with other methods, the fluorescence detection kit of the present invention does not require complicated operation steps and is highly applicable, with high sensitivity of detection results and good specificity. The method can be applied to rapid detection of samples in the field. 1/4 Figures -- - - - - - - - - - -- - - - - - - - - - - -- - - - - - - - - - I (A ). . . . . . .. . . . . . . . .. . . . .r. . .. . . . . . . . (B 98 INY4 YT C~ StepavIi I _i-a ta e *~~ ~ ~~ihu T-2___ toxiny ______ I _ Iptme _T 98 -U T- toi * I4 *OL MI 01(r Wit T-Ioi ig r 1 Fiur 2

Description

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Method and Kit for Fluorescence Detection of Small molecule Mycotoxin Based on Metal-organic Framework and Upconversion Nanoparticles

TECHNICAL FIELD

The present invention belongs to the field of small molecule detection, and particularly relates to a method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles, and a kit for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles.

BACKGROUND

T-2 toxin is one of naturally occurring Class A trichothecene toxins of Fusarium spp. As the most toxic toxin among such toxins, T-2 toxin is widely present in such grains as maize, barley, wheat and oats. T-2 toxin enters animals and humans with contaminated food, causing great harm to the health and growth of the organisms. It can exert various toxic effects in organisms, including acute toxicity and chronic toxicity, with symptoms of vomiting, anorexia and weight loss. In addition, T-2 toxin can also induce damage and apoptosis in the liver, brain tissue, nervous system and reproductive system, endangering human health and life safety.

At present, T-2 toxin is detected by immunoaffinity clean-up liquid chromatography and ELISA in the national standard, the former has a high accuracy, but requires the support of expensive large instrument platforms; the latter, despite of good specificity, is likely to result in unstable test results due to batch differences in antibodies. In recent years, many scholars have developed a variety of new methods to detect T-2 toxin, such as HPLC-MS, immunological detection methods and electrochemical detection methods. However, these methods are difficult to be used on a large scale due to either complicated operation steps or high detection costs. With the rapid development of modern nanotechnology, researches on target detection based on new fluorescent nanomaterials have become increasingly sophisticated. It is a direction of future development to establish a method capable of detecting targets sensitively and accurately through simple and convenient operation.

Therefore, it is necessary to develop a highly sensitive detection method to detect the content of T-2 toxin in food.

SUMMARY

In order to overcome the defects in the prior art, the technical problem to be solved by the present invention is to provide a fluorescence detection kit and a detection method with simple operation, rapid detection and low cost for rapid detection of a small molecule mycotoxin.

In order to achieve the purpose, the present invention provides a method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles, comprising the following steps:

S1. obtaining an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, comprising:

(i) dissolving PEI in water, then adding a solution containing upconversion nanoparticles (UCNPs), and stirring intensely to obtain UCNPs-PEI, wherein the upconversion nanoparticles are NaYF4:Yb,Tm or NaYF4:Yb,Tm@ NaYF4;

(ii) dispersing the UCNPs-PEI in PBS by ultrasonic treatment to obtain a mixture, then adding glutaraldehyde to the mixture, and shaking the mixture slowly at room temperature before centrifuging and washing;

(iii) dispersing the UCNPs from the (ii) in a buffer solution to obtain a mixture; adding streptavidin to the mixture, then shaking the mixture slowly at room temperature for reaction, centrifuging and washing after the reaction, then collecting and resuspending streptavidin-modified UCNPs in a buffer solution; and

(iv) adding a biotin-modified small molecule mycotoxin aptamer to the resuspended mixture from the (iii), shaking slowly overnight, then centrifuging, washing and resuspending the mixture in a buffer solution to obtain a buffer solution containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer;

S2. synthesis and activation of MIL-101(Cr): preparing an aqueous solution containing Cr(N03)3•9H20, HF and terephthalic acid, adding the aqueous solution to a high pressure reactor for reaction at 200-240 0 C, and purifying after the reaction to obtain a light green product; drying the product at high temperature under vacuum before use for activation, and suspending the activated product in a buffer solution, wherein the MIL-101(Cr) has a particle size of 1-1.5 pm;

S3. binding of the small molecule mycotoxin to the aptamer: adding a sample to be tested to the buffer solution containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer prepared in the S1, adding the MIL-101(Cr) suspension prepared in the S2 after incubation, and mixing thoroughly, followed by oscillating reaction; and

S4. signal detection: detecting a fluorescence signal of the product from the S3 by using a fluorescence spectrophotometer.

The schematic diagram of a detection process of the present invention is shown in Fig. 1. According to the present invention, an aptamer sensor for sensitively detecting T-2 toxin based on fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and a metal-organic framework (MOF) is developed. Due to rr-r stacking between organic ligands of MIL-101(Cr) and nucleic acid bases, the MIL-101(Cr) adsorbs the upconversion nanoparticle probe modified with the small molecule mycotoxin aptamer, resulting in upconversion fluorescence quenching. After T-2 toxin is added, the FRET process is blocked as the T-2 toxin is away from the MIL-101(Cr) due to specific binding between the T-2 toxin and the upconversion nanoparticle probe modified with the small molecule mycotoxin aptamer, so that the fluorescence intensity recovers. The T-2 toxin at different concentrations produces different degrees of fluorescence recovery upon binding with the upconversion nanoparticle probe modified with the small molecule mycotoxin aptamer. Based on the response characteristic, the concentration of the T-2 toxin in the reaction system can be quantitatively detected by the fluorescence intensity.

The upconversion nanoparticles used in the present invention can be purchased commercially or synthesized by a conventional method in the prior art, and preferably, the upconversion nanoparticles are prepared by the following method:

(a) dissolving YCl3•6H20, YbCl3•6H20 and TmCl3•6H20 in water, and adding the resulting solution to a three-necked flask filled with OA and 1-ODE;

(b) stirring the solution at room temperature for 8-12 min, heating at 140-1600 C for 1-2 h to remove water to form a lanthanide oleate complex, and cooling the complex to 45-55°C; and

(c) adding NaOH and NH4F that are dissolved in CH30H to the mixture, and stirring at 45-55 0C for 20-40 min; heating the system to 95-100°C in a N2 atmosphere to remove CH30H, and holding at 300-350°C for 1-2 h; cooling the solution to room temperature at the end of the reaction, adding absolute ethanol, centrifuging to obtain a precipitate, then washing the precipitate repeatedly with water and ethanol to obtain the upconversion nanoparticles.

According to the present invention, preferably, the method further comprises a step of preparing a standard curve: detecting a series of standard solutions of the small molecule mycotoxin with known concentrations by the method in the S1-S4, measuring groups of fluorescence values, and plotting a standard curve of the small molecule mycotoxin with the concentrations and the fluorescence values as an x-coordinate and a y-coordinate respectively.

According to the present invention, preferably, the S4 further comprises a step of calculating the content of the small molecule mycotoxin in the sample to be tested based on the standard curve.

The method of the present invention is in principle applicable to a variety of small molecule mycotoxins meeting the above detection requirements. According to a preferred embodiment of the present invention, the small molecule mycotoxin is T-2 toxin with an aptamer sequence of 5'-CAG CTC AGA AGC TTG ATC CTG TAT ATC AAG CAT CGC GTG TTT ACA CAT GCG AGA GGT GAA GA CTC GAA GTC GTG CAT CTG-biotin-3'(SEQ ID NO:1).

According to the present invention, the buffer solution in the S1 includes but is not limited to pH7.3 10mM Tris-HCI, pH7.3 10mM PBS or HEPES, preferably pH7.3 mM Tris-HCI.

According to the present invention, the S2 preferably comprises:

adding an aqueous solution containing 2-4 mmol Cr(N3)3•9H20, 35-45% HF and 30-40 mg/mL terephthalic acid to a PTFE-lined high pressure reactor for reaction at 210-230 0C for 6-10 h; cooling naturally at the end of the reaction to obtain a green product and a crystallized H2BDC by-product; purifying the product by washing with hot ethanol and DMSO and centrifuging for more than three times, and drying the purified light green product at 70-90 0 C under vacuum; drying the product at 140-160C under vacuum for 6-10 h for activation before use, and suspending the activated product in pH7-7.5 8-12mM Tris-HCI.

According to the present invention, the S3 preferably comprises: adding a sample to be tested to a 0.4-0.6 mg/mL buffer solution containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, incubating at 370 C for 0.2-1 h, adding an MIL-101(Cr) suspension, mixing thoroughly, and shaking slowly for oscillating reaction at 37 0C for 10-30 min, wherein the mass ratio of the upconversion nanoparticles to the MIL-101(Cr) is 1:1.

According to the present invention, the particle size is controlled when the MIL-101 is prepared; and the ratio of the MIL-101 to the UCNPs added, reaction time and type of the buffer solution are optimized while detecting the T-2 toxin, so that high sensitivity detection of the T-2 toxin can be realized under optimal conditions.

According to the present invention, the S4 preferably comprises steps of: detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer with an excitation wavelength of 980nm and an emission wavelength of 482nm.

The method of the present invention is applicable to a variety of samples, and the sample to be tested is selected from corn flour, beer, bean flour and flour. Such samples can be used as the sample to be tested after simple treatment.

The second aspect of the present invention provides a kit for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles, comprising the following components:

(1) an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, prepared by the method described in the S1; and

(2) MIL-101(Cr), prepared by the method described in the S2.

Due to rare-earth-doped upconversion nanoparticles used in the present invention, the fluorescence intensity is stable and the background value is low. Compared with other methods, the fluorescence detection kit of the present invention does not require complicated operation steps and is highly applicable, with high sensitivity of detection results and good specificity. With an LOD of 0.087 ng mL-1 and a linear range of 0.1-100 ng mL- 1, the method can be applied to rapid detection of samples in the field.

Other features and advantages of the present invention will be described in detail in the following description of the invention.

BRIEF DESCRIPTION OF THE FIGURES

These and other orientations, features and advantages of the present invention will become better understood with reference to the following drawings and detailed description of exemplary embodiments therein.

Fig. 1 shows the detection principle of the present invention.

Fig. 2 is a transmission electron micrograph of upconversion nanoparticles (UCNPs).

Fig. 3 is a transmission electron micrograph of a metal-organic framework (MIL-101(Cr)).

Fig. 4 is a transmission electron micrograph of a UCNPs-MIL-101(Cr) complex with or without T-2 toxin, the scale of the left two figures is 200nm, and the scale of the right two figures is 100nm.

Fig. 5 shows a standard curve plotted with the concentrations of T-2 toxin reference standards as an x-coordinate and the fluorescence intensities corresponding to the concentrations as a y-coordinate.

Fig. 6 shows a specificity experiment for fluorescence detection of T-2 toxin based on a metal-organic framework and upconversion nanoparticles, the purple column represents 2 ng/mL and the blue column represents 10 ng/mL.

DESCRIPTION OF THE INVENTION

The present invention will be described in more detail below with reference to preferred embodiments. However, it should be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the following examples, reagents used for synthesis of upconversion nanoparticles were purchased from Sigma-Aldrich, reagents required for synthesis of MIL-101(Cr) were purchased from Aladdin Biochemical Technology Co., Ltd., and other common organic reagents were purchased from domestic chemical reagent manufacturers.

Example 1

The example is used to illustrate a rapid detection kit and a detection method for

T-2 toxin of the present invention. The specific implementation steps are as follows:

1) preparation and modification of upconversion nanoparticles modified with a small molecule mycotoxin aptamer

(a) dissolving 0.78 mmol YCl3•6H20, 0.2 mmol YbCl3•6H20 and 0.02 mmol TmCl3•6H20in 4 mL of aqueous solution, and adding the solution to a 100 mL three-necked flask containing 9 mL of OA and 15 mL of 1-ODE;

(b) stirring the solution at room temperature for 10 min, heating at 1500 C for 1.5h to remove water to form a lanthanide oleate complex (at this point, the solution was clear and light yellow), and cooling to 50°C;

(c) adding 2.5mmol NaOH and 4mmol NH4F that were dissolved in 10 mL of CH30H to the above mixture and stirring at 50 0C for 30 min; heating the system to 100°C in a N2 atmosphere, holding for 1 h to remove CH30H, and holding at 3200 C for 1.5 h; cooling the solution to room temperature at the end of the reaction, adding absolute ethanol, centrifuging to obtain a precipitate, then washing the precipitate with water and ethanol for three times to obtain the UCNPs, Fig. 2 is a transmission electron micrograph of the prepared upconversion nanoparticles (UCNPs);

(d) dissolving 300mg of PEI in 5 mL of ultrapure water, then adding a cyclohexane solution containing 10mg of UCNP, and stirring intensely for 24h; washing the UCNPs-PEI with ultrapure water and ethanol for several times after the reaction to finally obtain a product by freeze drying;

(e) dispersing 2 mg of UCNPs-PEI in 1 mL of PBS (10 mM pH 7.4) by ultrasonic treatment for 15 min, and then adding 0.5 mL of 25% glutaraldehyde to the mixture; shaking the mixture slowly at room temperature for 2 h, centrifuging and washing with PBS for 3 times;

(f) dispersing the obtained UCNPs in 1 mL of 10mM PBS; then adding 100pL of 1.0mg mL 1 streptavidin (SA) to the mixture, and shaking slowly at room temperature for reaction for 12 h; centrifuging and washing for several times, collecting and resuspending SA-modified UCNPs in 10 mM Tris-HCI (pH7.3) for later use; and

(g) adding a biotin-modified T-2 toxin aptamer (10pM, 20pL) to the resuspended mixture obtained in the (f); shaking slowly at 37C overnight, then centrifuging, washing and resuspending the mixture in 10 mM Tris-HCI(pH7.3) to obtain a buffer solution containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer for later use;

2) synthesis and activation of MIL-101(Cr): preparing 14.4 mL of aqueous solution containing Cr(N03)3•9H20 (1200mg, 3 mmol), 40% HF(120 pL) and terephthalic acid (H2BDC) (492mg), and adding the resulting mixture to a PTFE-lined high pressure reactor for reaction at 220 0C for 8 h; cooling naturally at the end of the reaction to obtain a green product and a crystallized H2BDC by-product; purifying the product by washing with hot ethanol and DMSO and centrifuging for more than three times, and drying the purified light green product at 800 C under vacuum for later use, where the MIL-101(Cr) has a particle size of 1-1.5 pm; drying the product at 1500 C under vacuum for 8 h for activation before use, and suspending the activated product in 10 mM Tris-HCI (pH 7.3) with a concentration of 2mg mL for later use (after dilution), Fig. 3 is a transmission electron micrograph of the prepared metal-organic framework (MIL-101(Cr)).

3) binding of T-2 toxin to an aptamer: to a buffer solution (100 pL, 0.5 mg/mL) containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, adding 50 pL of a series of T-2 toxin reference standards with a concentration gradient, and incubating at 37C for 0.5 h; adding an equal volume of an MOFs suspension to centrifuge tubes and mixing thoroughly, then shaking slowly for oscillating reaction at 37 0C for 20 min, Fig. 4 is a transmission electron micrograph of a UCNPs-MIL-101(Cr) complex with or without T-2 toxin; and

4) signal detection: detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer (excitation wavelength: 980 nm, slit width: nm, voltage: 900V) with an emission wavelength of 482 nm.

A series of T-2 toxin reference standards with a concentration gradient with known concentrations were determined by the above method, and a standard curve was plotted, as shown in Fig. 5.

Example 2

The example is used to illustrate a method for detecting T-2 toxin in corn flour by a fluorescence aptamer sensor based on a metal-organic framework and upconversion nanoparticles of the present invention, in which the upconversion nanoparticle probe and the metal-organic framework MIL-101(Cr) prepared in

Example 1 are adopted.

The method specifically comprises the following steps:

1) adding T-2 toxin at three different concentrations to water: 1 ng/mL, 5 ng/mL and 20 ng/mL; mixing 1 g of corn flour with 10 mL of extraction solvent containing T-2 toxin at different concentrations (methanol:water = 6:4 (v/v));

2) vortexing samples for 5 min, then centrifuging at 13000 rpm for 10 min, and collecting supernatants;

3) to the buffer solution containing the upconversion nanoparticle probe (100 pL, 0.5 mg/mL), adding 50 pL of supernatant of each of the three corn extracts, and incubating at 370 C for 0.5h;

4) adding an equal volume of an MIL-101(Cr) suspension to centrifuge tubes, mixing thoroughly, and shaking slowly for oscillating reaction at 37 0 C for 20 min;

5) detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer (excitation wavelength: 980 nm, slit width: 20 nm, voltage: 900V) with an emission wavelength of 482 nm; and

6) comparing detected concentrations calculated by the standard curve with actual concentrations, with a recovery of 97.52% - 109.53% and an RSD of 1.7% 2.4%. The results show that the detection method can be applied to actual detection of corn flour, and the pretreatment is simple.

Example 3

The example is used to illustrate a method for detecting a T-2 toxin in beer by a fluorescence aptamer sensor based on a metal-organic framework and upconversion nanoparticles of the present invention, in which the upconversion nanoparticle probe and the metal-organic framework MIL-101(Cr) prepared in Example 1 are adopted.

1) refrigerating beer at 40 C for 30 min or degassing the beer by ultrasonic wave before use, adding T-2 toxin at different concentrations to the beer, and adding 1OpL of the resulting mixture to 990pL of 10mM Tris-HCI to keep final concentrations of the T-2 toxin at 1 ng/mL, 5 ng/mL and 20 ng/mL respectively to obtain samples to be tested with three concentrations.

2) adding 50 pL of each of the three beer sample solutions to a buffer solution

(100 pL, 0.5 mg/mL) containing an upconversion particle probe, and incubating at 37 0C for 0.5 h;

3) adding an equal volume of an MOFs suspension to centrifuge tubes, mixing thoroughly, and shaking slowly for oscillating reaction at 370 C for 20 min;

4) detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer (excitation wavelength: 980 nm, slit width: 20 nm, voltage: 900 V) with an emission wavelength of 482 nm; and

5) comparing detected concentrations calculated by the standard curve with actual concentrations, with a recovery of 92.72% - 100.02% and an RSD of 2.4% 2.7%. The results show that the detection method can be applied to actual detection of beer samples, and the pretreatment is simple.

Example 4

The example is used to illustrate the specificity of fluorescence detection of T-2 toxin based on a metal-organic framework and upconversion nanoparticles.

Specificity test steps:

1) adding 100 pL of UCNPs-aptamer (0.5 mg mL- 1) to a centrifuge tube, then adding 50 pL of 2.10 ng mL-1 aflatoxin B1 (AFB1), ochratoxin A (OTA), fumonisin B1 (FB1), zearalenone (ZEN) and T-2 toxin, and shaking at 370 C for incubation for 30 min;

2) adding an equal volume of an MIL-101(Cr) suspension to centrifuge tubes, mixing thoroughly, and shaking slowly for reaction at 37C for 20 min after thorough vortex mixing; and

3) finally, adding the sample to a micro quartz cell, and detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer (excitation wavelength: 980 nm, slit width: 20 nm, voltage: 900V) with an emission wavelength of 482 nm.

Result analysis: The concentrations of the target and analogues were set at 2 ng mL-1 and 10 ng mL- 1, with the results shown in Fig. 6. It could be seen that the fluorescence intensity greatly recovered only when the T-2 toxin was added, that is, the fluorescence intensity was the highest in this case. In contrast, only a small amount of fluorescence recovered after other toxins were added. This is because only the T-2 toxin can specifically bind to the aptamer, thus causing the upconversion nanoparticle probe modified with the T-2 toxin aptamer to be far away from the MIL-101(Cr), and eventually leading to the recovery of upconversion fluorescence, which is due to the fact that other toxins cannot specifically bind to the upconversion nanoparticle probe modified with T-2 toxin aptamer, so that it is impossible to induce a significant change in fluorescence intensity. The specificity test has proved that toxin analogues have little effect on the upconversion fluorescence sensor having satisfactory specificity.

The foregoing description of the various embodiments of the present invention has been presented for the purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations can be made without departing from the spirit and scope of the invention, as will be apparent to those skilled in the art.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles, characterized by comprising the following steps:

2. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the upconversion nanoparticles are prepared by the following method:

(c) adding NaOH and NH4F that are dissolved in CH30H to the mixture, and stirring at 45-55 0C for 20-40 min; heating the system to 95-100°C in a N2 atmosphere to remove CH30H, and holding at 300-350 0C for 1-2 h; cooling the solution to room temperature at the end of the reaction, adding absolute ethanol, centrifuging to obtain a precipitate, then washing the precipitate repeatedly with water and ethanol to obtain the upconversion nanoparticles.

3. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the method further comprises a step of preparing a standard curve: detecting a series of standard solutions of the small molecule mycotoxin with known concentrations by the method in the S1-S4, measuring groups of fluorescence values, and plotting a standard curve of the small molecule mycotoxin with the concentrations and the fluorescence values as an x-coordinate and a y-coordinate respectively.

4. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 3, wherein the S4 further comprises a step of calculating the content of the small molecule mycotoxin in the sample to be tested based on the standard curve.

5. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the small molecule mycotoxin is T-2 toxin with an aptamer sequence of

'-CAG CTC AGA AGC TTG ATC CTG TAT ATC AAG CAT CGC GTG TTT ACA CAT GCG AGA GGT GAA GA CTC GAA GTC GTG CAT CTG-biotin-3'(SEQ ID NO:1).

6. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the S2 comprises steps of:

7. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the S3 comprises steps of:

adding a sample to be tested to a 0.4-0.6 mg/mL buffer solution containing an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, incubating at 370 C for 0.2-1 h, adding an MIL-101(Cr) suspension, mixing thoroughly, and shaking slowly for oscillating reaction at 37 0C for 10-30 min, wherein the mass concentration ratio of the upconversion nanoparticles to the MIL-101(Cr) is 1:1.

8. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 5, wherein the S4 comprises steps of: detecting a fluorescence signal at room temperature by using an F97pro fluorescence spectrophotometer with an excitation wavelength of 980nm and an emission wavelength of 482nm.

9. The method for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles according to claim 1, wherein the sample to be tested is selected from corn flour, beer, bean flour and flour.

10. A kit for fluorescence detection of a small molecule mycotoxin based on a metal-organic framework and upconversion nanoparticles, comprising the following components:

(1) an upconversion nanoparticle probe modified with a small molecule mycotoxin aptamer, prepared by the method described in the S1 of claim 1; and

(2) MIL-101(Cr), prepared by the method described in the S2 of claim 1.