Chiral MOFs magnetic nanocomposite enzyme and preparation method and application thereof

Abstract

The application discloses a kind of chiral MOFs magnetic nano composite enzyme and its preparation method and application, belong to nanocomposite material technical field.The chiral MOFs magnetic nano composite enzyme includes magnetic nanoparticle and the chiral MOFs that the magnetic nanoparticle is covered by chemical bonding;The magnetic nanoparticle is with ferroferric oxide nanomagnetic bead as inner core, the outer surface of the ferroferric oxide nanomagnetic bead is coated with silica layer, and the outer surface of the silica layer is modified with carboxyl group.The application can cooperate chiral MOFs with magnetic nanoparticle, realize high sensitivity detection to early blood biomarker NFL of Alzheimer disease, and provide technical support for early diagnosis, prevention and treatment etc. of Alzheimer disease.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, and in particular to a chiral MOF magnetic nanocomposite enzyme, its preparation method, and its application. Background Technology

[0002] Population aging, as a global issue, has triggered a series of pressing social problems, among which Alzheimer's disease (AD) is particularly prominent. AD, a severe neurodegenerative disease, is characterized by progressive memory decline, language and orientation difficulties, accompanied by mood swings, loss of self-care abilities, and cognitive impairment. With the accelerating pace of population aging, AD not only poses a serious challenge to the healthcare system but will also have a profound impact on socioeconomic development. Neurofilament light chain protein (NF), which is closely related to neuronal damage, is considered a potential diagnostic biomarker for AD. The concentration of NFL in cerebrospinal fluid and blood increases with axonal damage, and blood NFL levels can be used to predict and reflect the progression of neurodegenerative diseases.

[0003] Currently, methods for detecting NFL mainly include enzyme-linked immunosorbent assay (ELISA), Western blotting, colorimetry, electrochemiluminescence immunoassay, fluorescence analysis, single-molecule immunoassay, and liquid chromatography-mass spectrometry (LC-MS). However, these methods suffer from insufficient sensitivity, weak anti-interference ability, poor stability, high cost, and complex sample pretreatment. Compared to the invasiveness and poor patient compliance of cerebrospinal fluid testing, blood testing has significant advantages such as simple sampling, high safety, good reproducibility, and low cost. However, the content of NFL in blood is extremely low, placing extremely high demands on detection technology. To achieve effective clinical application, it is necessary to overcome the sensitivity limitations of traditional immunoassay techniques and develop novel detection platforms.

[0004] Therefore, exploring highly sensitive and specific NFL detection methods is of great scientific value and practical significance for promoting the early diagnosis and prevention of AD. Summary of the Invention

[0005] To address the aforementioned issues, this invention aims to provide a chiral MOF magnetic nanocomposite enzyme, its preparation method, and its applications.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, a chiral MOF magnetic nanocomposite enzyme is provided, comprising magnetic nanoparticles and chiral MOFs that are chemically bonded to the magnetic nanoparticles; the magnetic nanoparticles have iron oxide nanobeads as the core, the outer surface of the iron oxide nanobeads is coated with a silica layer, and the outer surface of the silica layer is modified with carboxyl groups.

[0008] Preferably, the chiral MOFs are constructed by coordination polymerization of iron salt with L-proline as the chiral ligand.

[0009] Preferably, the chiral MOFs are constructed by coordination polymerization of zinc salt with L-histidine as the chiral ligand.

[0010] Preferably, the mass ratio of the magnetic nanoparticles to the chiral MOFs is 1:1-1.2.

[0011] On the other hand, a method for preparing the chiral MOFs magnetic nanocomposite enzyme according to any one of the above claims is also provided, comprising the following steps: preparing raw materials for the preparation of chiral MOFs and magnetic nanoparticles; using a solvothermal method to generate chiral MOFs from the raw materials for the preparation of chiral MOFs and coat the outer surface of the magnetic nanoparticles to obtain the chiral MOFs magnetic nanocomposite enzyme.

[0012] Preferably, when the chiral MOFs are prepared using iron salts and L-proline, the preparation method includes the following steps:

[0013] S1: Prepare iron salt solution, L-proline solution and magnetic nanoparticles;

[0014] S2: The magnetic nanoparticles are ultrasonically dispersed in the iron salt solution, and then the L-proline solution is added under ultrasonic dispersion conditions to obtain a mixture;

[0015] S3: The mixture is reacted at 70-85℃ for 16-25 h, and then the product is washed to obtain the chiral MOFs magnetic nanocomposite enzyme.

[0016] Preferably, in step S1, anhydrous ethanol is used as the solvent for both the iron salt solution and the L-proline solution.

[0017] Preferably, in step S1, the concentrations of the iron salt solution and the L-proline solution are both 100 mM; in step S2, 5-15 mg of the magnetic nanoparticles are added to every 1 mL of the iron salt solution, and the volume ratio of the L-proline solution to the iron salt solution is 1:1.

[0018] Furthermore, the invention also provides an application of the chiral MOF magnetic nanocomposite enzyme described in any of the above-mentioned embodiments in the detection of the Alzheimer's disease biomarker NFL.

[0019] Preferably, the chiral MOFs magnetic nanocomposite enzyme is combined with an NFL antibody to form a probe, and detection is performed using a double antibody sandwich method.

[0020] The beneficial effects of this invention are:

[0021] This invention combines the porosity of chiral MOFs with the magnetic responsiveness of magnetic nanoparticles, resulting in a chiral MOF magnetic nanocomposite enzyme exhibiting higher thermal stability and superior catalytic performance. Furthermore, the preparation of the detection probe is convenient, requiring only the application of a magnetic field without the need for additional centrifugation or filtration, significantly reducing time costs. In addition, the chiral MOF magnetic nanocomposite enzyme of this invention can efficiently load antibodies and enhance the chemiluminescent function of luminol, constructing a novel chemiluminescent immunosensor capable of highly sensitive detection of NFL in blood, providing technical support for the early diagnosis, prevention, and treatment of Alzheimer's disease. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the synthetic route of the chiral MOFs magnetic nanocomposite enzyme of the present invention;

[0024] Figure 2 This is a TEM image of the chiral MOF magnetic nanocomposite enzyme from Example 1.

[0025] Figure 3 SEM image of magnetic nanoparticles without CMOF coating in Example 1;

[0026] Figure 4 Here is a SEM image of the chiral MOF magnetic nanocomposite enzyme from Example 1.

[0027] Figure 5 The image shows a TEM image of the complex enzyme in Comparative Example 1.

[0028] Figure 6 The infrared spectrum characterization of the chiral MOF magnetic nanocomposite enzyme in Example 1 is shown below.

[0029] Figure 7The image shows the hysteresis loop (VSM) of the chiral MOF magnetic nanocomposite enzyme in Example 1.

[0030] Figure 8 The UV-Vis spectrum of the colorimetric reaction of TMB / H2O2 catalyzed by chiral MOF magnetic nanocomposite enzyme in Example 1 is shown.

[0031] Figure 9 The UV-Vis spectra of the colorimetric reaction of TMB / H2O2 catalyzed by chiral MOF magnetic nanocomposite enzymes in Examples 1 and 2 are shown.

[0032] Figure 10 Linear response curves of the detection system after adding different concentrations of NFL were obtained;

[0033] Figure 11 This is a schematic diagram of the selectivity test results of chiral MOFs magnetic nanocomposite enzyme NFL in Example 1. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0035] On the one hand, such as Figure 1 As shown, this invention provides a chiral MOF magnetic nanocomposite enzyme (denoted as Fe3O4NPs@CMOFs), comprising magnetic nanoparticles and chiral MOFs (Chiral Metal-Organic Frameworks, abbreviated as CMOFs) that are chemically bonded to the magnetic nanoparticles; the magnetic nanoparticles have a core of iron oxide nanobeads, and the outer surface of the iron oxide nanobeads is coated with a silica layer, the outer surface of which is modified with carboxyl groups.

[0036] In this invention, a hierarchical composite structure of "magnetic core-chiral shell" is constructed using the magnetic nanoparticles and chiral MOFs. The magnetic nanoparticles have a core of iron oxide nanobeads coated with a dense silica layer, which effectively protects the magnetic core, preventing aggregation and oxidation, and provides a stable carrier for subsequent activity modification. The carboxyl functional groups modified on the silica layer act as specific linking bridges, overcoming the drawbacks of physical adsorption and forming stable coordination bonds with iron ions in the chiral MOF framework. This achieves chemical bonding between the magnetic nanoparticles and the chiral MOFs, constructing an integrated composite structure of "core-intermediate modification layer-chiral active layer." The core advantage of this composite enzyme lies in ensuring rapid separation of the magnetic components while maximizing the chiral recognition and catalytic activity of the chiral MOFs, achieving synergistic effects of each component's function, and significantly enhancing the analytical and detection application potential of the composite enzyme.

[0037] In this invention, the magnetic nanoparticles are surface-carboxylated iron(III) oxide / silica magnetic nanoparticles. These nanoparticles can form a CMOF (Carbonized Metal-Metal-Oriented Facility) coating layer on their surface through the coordination of carboxyl groups with metal ions. The CMOF structure is tunable and spatially selective. Utilizing their chiral specific interaction with antibodies, the immunomodulatory activity of antibodies is maximized, and the activity of antigen-binding sites is fully protected. This improves the efficiency of the immune reaction between CMOFs on the magnetic nanoparticle surface and NFL (NFL), thereby enhancing detection sensitivity.

[0038] The chiral MOFs magnetic nanocomposite enzyme described in this invention has small particle size, excellent monodispersity, strong magnetic response, large specific surface area, strong loading capacity, tunable structure, good biocompatibility, and great medical potential. At the same time, the nanomaterial can act as both a carrier and a signal amplifier to enhance the intensity of CL (chemiluminescence), playing an important role in chemiluminescence / magnetic biosensing detection.

[0039] In one specific embodiment, the chiral MOFs are constructed by coordination polymerization of iron salts with L-proline (L-Pr) as the chiral ligand, or by coordination polymerization of zinc salts with L-histidine (L-His) as the chiral ligand. In this embodiment, constructing the chiral MOFs via coordination polymerization allows for the creation of MOF frameworks with precise chiral microenvironments, achieving concise and efficient construction of chiral components and high-density exposure of chiral active sites.

[0040] In one specific embodiment, the mass ratio of the magnetic nanoparticles to the chiral MOFs is 1:1-1.2. Optionally, the mass ratio of the magnetic nanoparticles to the chiral MOFs is 1:1.1.

[0041] On the other hand, the present invention also provides a method for preparing the chiral MOFs magnetic nanocomposite enzyme according to any one of the above claims, comprising the following steps: preparing raw materials for the preparation of chiral MOFs and magnetic nanoparticles; using a solvothermal method to generate chiral MOFs from the raw materials for the preparation of chiral MOFs and coat the outer surface of the magnetic nanoparticles to obtain the chiral MOFs magnetic nanocomposite enzyme.

[0042] In this invention, the chiral MOF magnetic nanocomposite enzyme is prepared using a solvothermal method, which effectively increases the carboxyl group density on the surface of the composite enzyme, creating conditions for subsequent immune responses. Furthermore, this method is mild, conducive to large-scale preparation, and has good versatility. It should be noted that the solvothermal method of this invention is only a preferred preparation method; other existing methods capable of producing the chiral MOF magnetic nanocomposite enzyme structure described in this invention are also applicable to this invention.

[0043] In one specific embodiment, when the chiral MOFs are prepared using iron salts and L-proline, the preparation method includes the following steps:

[0044] S1: Prepare iron salt solution, L-proline solution and magnetic nanoparticles;

[0045] S2: The magnetic nanoparticles are ultrasonically dispersed in the iron salt solution, and then the L-proline solution is added under ultrasonic dispersion conditions to obtain a mixture;

[0046] S3: The mixture is reacted at 70-85℃ for 16-25 h, and then the product is washed to obtain the chiral MOFs magnetic nanocomposite enzyme.

[0047] It should be noted that the preparation method of the magnetic nanoparticles is existing technology, and the specific preparation method will not be described in detail here.

[0048] In one specific embodiment, in step S1, anhydrous ethanol is used as the solvent for both the iron salt solution and the L-proline solution. It should be noted that, besides the preferred solvent of this embodiment, other solvents suitable for solvothermal methods in the prior art can also be used in this invention, such as methanol. However, because methanol has a low boiling point, it will affect the yield of the synthesized material.

[0049] In one specific embodiment, in step S1, the concentrations of the iron salt solution and the L-proline solution are both 100 mM; in step S2, 5-15 mg of the magnetic nanoparticles are added to every 1 mL of the iron salt solution, and the volume ratio of the L-proline solution to the iron salt solution is 1:1.

[0050] Furthermore, the present invention also provides the application of the chiral MOF magnetic nanocomposite enzyme described in any one of the above claims in the detection of the Alzheimer's disease biomarker NFL.

[0051] In one specific embodiment, the chiral MOFs magnetic nanocomposite enzyme and NFL antibody are used to make a probe, and the detection is performed using a double antibody sandwich method.

[0052] Example 1

[0053] A chiral MOF magnetic nanocomposite enzyme was prepared by the following steps: 50 mg of Fe3O4NPs@SiO2-COOH was ultrasonically dispersed in 4 mL of anhydrous ethanol solution (100 mM) of FeCl3·6H2O. Then, 4 mL of anhydrous ethanol solution (100 mM) of L-proline was added while still ultrasonically dispersed. The mixture was then reacted at 80 °C for 22 h. After the reaction was complete, the precipitate was washed three times with anhydrous ethanol to obtain the chiral MOF magnetic nanocomposite enzyme, denoted as Fe3O4@L-Pr-MOF.

[0054] Example 2

[0055] A chiral MOF magnetic nanocomposite enzyme was prepared by the following steps: 25 mg Fe3O4NPs@SiO2-COOH and 23.5 mg L-histidine were ultrasonically dispersed in 2 mL of deionized water, and then 1.25 mL of triethanolamine was added. 173 mg 2-methylimidazole and 179 mg Zn(NO3)2·6H2O were dissolved in 6 mL and 10 mL of methanol, respectively, and then added to the above dispersion. The reaction was carried out at room temperature with shaking for 4 h. After the reaction was completed, the precipitate was washed three times each with water and methanol to obtain the chiral MOF magnetic nanocomposite enzyme, denoted as Fe3O4@L-His-MOF.

[0056] Example 3

[0057] A chiral MOF magnetic nanocomposite enzyme was prepared by the following steps: 25 mg of Fe3O4NPs@SiO2-COOH was ultrasonically dispersed in 4 mL of anhydrous ethanol solution (100 mM) of FeCl3·6H2O. Then, 4 mL of anhydrous ethanol solution (100 mM) of L-proline was added while still ultrasonically dispersed. The mixture was then reacted at 80 °C for 23 h. After the reaction was complete, the precipitate was washed three times with anhydrous ethanol to obtain the chiral MOF magnetic nanocomposite enzyme.

[0058] Comparative Example 1

[0059] Unlike Example 1, the magnetic nanoparticles in this comparative example are Fe3O4NPs magnetic nanoparticles without surface carboxylation.

[0060] Test Example 1

[0061] The morphology of the complex enzymes in each example and Comparative Example 1 was observed using transmission electron microscopy and scanning electron microscopy. The test results for Example 1 are as follows: Figures 2-4 As shown, the test results for Comparative Example 1 are as follows: Figure 5 As shown.

[0062] from Figures 2-4 As can be seen, the Fe3O4@L-Pr-MOF nanocomposite enzyme prepared in Example 1 exhibits a coated structure, which can directionally grow chiral MOFs on the surface of Fe3O4NPs@SiO2-COOH as the core. The surface carboxylated magnetic nanoparticles can improve interfacial compatibility.

[0063] from Figure 5 It can be seen that a dense coating layer was not formed on the surface of the nanocomposite enzyme magnetic beads prepared in Comparative Example 1. This is because the chiral MOFs in Comparative Example 1 did not achieve a tight bond with Fe3O4NPs through interfacial interactions (such as coordination bonds) to form a core-shell structure.

[0064] Test Example 2

[0065] The complex enzymes of each embodiment and Comparative Example 1 were subjected to infrared spectroscopy tests, with the test results of Example 1 as follows: Figure 6 As shown. From Figure 6 It can be seen that 3433 cm -1 The absorption peak at 3436 cm⁻¹ corresponds to the stretching vibration of Si-OH. -1 The absorption peak at 2925 cm⁻¹ is the stretching vibration peak of the NH bond. -1 The absorption peak at 2363 cm⁻¹ represents the stretching vibration of the hydroxyl group in the carboxyl group. -1 The absorption peak at 1635 cm⁻¹ is the stretching vibration peak of the CH bond. -1 The absorption peak at 1050 cm⁻¹ corresponds to the stretching vibration of the C=O double bond in the carboxyl group. -1 The absorption peak at 879 cm⁻¹ is the symmetric stretching vibration of the Si-O bond. -1 The peak at this location is the absorption peak of Fe3O4. Figure 6 The results show that the present invention successfully prepared a structure in which chiral MOFs are coated with magnetic nanoparticles.

[0066] Test Example 3

[0067] The magnetization properties of the composite enzymes in each embodiment and Comparative Example 1 were tested, with the test results for Example 1 as follows: Figure 7 As shown. From Figure 7It can be seen that after the Fe3O4NPs@SiO2-COOH surface is coated with L-Pr-MOF, the nanocomposite magnetic beads still exhibit a high magnetic response, with a saturation magnetization of 60 emu / g and a coercivity close to zero, exhibiting superparamagnetism.

[0068] Test Example 4

[0069] Take 120 μL of the 1 mg / mL composite enzymes from Examples 1 and 2 (dispersed in water), add 2.7 mL of 0.2 M, pH 3.84 HAc-NaOAc (acetic acid-sodium acetate) buffer solution, 120 μL of 20 mM TMB (3,3',5,5'-tetramethylbenzidine) solution, and 60 μL of 20 mM H2O2 (hydrogen peroxide) solution, mix well, incubate at room temperature for 30 min, and measure the absorbance at 400-800 nm. The test results are as follows. Figure 8 and Figure 9 As shown.

[0070] from Figure 8 and Figure 9 It can be seen that the peroxidase activity of the Fe3O4@L-Pr-MOF nanocomposite enzyme in Example 1 is higher than that of Fe3O4NPs (i.e., Fe3O4NPs@SiO2-COOH, which is abbreviated in the text and figures of this invention). The Fe3O4@L-His-MOF in Example 2 also showed good peroxidase activity, but it was slightly lower than that of Fe3O4@L-Pr-MOF.

[0071] Test Example 5

[0072] Take 5 mg of Fe3O4@L-Pr-MOF from Example 1, add 1 mL of 100 mM, pH 5 MES (2-morpholinoethanesulfonic acid) buffer, and sonicate. Take 500 μL each of EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, concentration 2 mg / mL) and Sulfo-NHS (N-hydroxythiosuccinimide, concentration 6 mg / mL) to make the final EDC to Sulfo-NHS concentration ratio 1:3, shake and activate for 20 min, wash 3 times with 500 μL of 100 mM, pH 5 MES buffer. Add 1 mL of NFL Ab2 (detection antibody, 200 μg / mL), incubate at room temperature for 2 h, wash 3 times with 10 mM, pH 7.2-7.4 PBS buffer (phosphate buffer). Add 1 mL of 1% BSA (bovine serum albumin) solution, block at room temperature for 2 h. The probe was washed three times with 10 mM PBS buffer solution (pH 7.2-7.4) for h. The Fe3O4@L-Pr-MOF / Ab2 probe was diluted to 1 mg / mL with 5 mL PBST (1‰ Tween) + 1% BSA solution and stored in a glass bottle at 4 °C.

[0073] NFL Ab1 (capture antibody) was diluted to 1 μg / mL using pH 10 CBS (carbonate buffer solution). 100 μL was added to a 96-well plate (white plate) and incubated overnight at 4 °C. After the reaction, unreacted NFL Ab1 was removed, and the plate was washed with 200 μL PBST, repeated 5 times. 150 μL of 2 wt% BSA was added, and the plate was incubated at 37 °C for 2 h, followed by 6 washes. Then, gradient antigens (0 pg / mL, 1 pg / mL, 2 pg / mL, 10 pg / mL, 100 pg / mL, 300 pg / mL) were added, and the plate was incubated at 37 °C for 2 h, followed by 6 washes. Finally, 100 μL of 1 μg / mL Fe3O4@L-Pr-MOF / Ab2 probe was added, and the plate was incubated at 37 °C for 2 h, followed by 6 washes. 100 μL of pH 10 CBS and 40 μL of 10 mM PBST were added. Luminol (40 μL) and 50 mM H2O2 were added, and the chemiluminescence signal of the system was recorded. The results are as follows: Figure 10 As shown.

[0074] from Figure 10It can be seen that as the concentration of NFL gradually increases within the range of 0–300 pg / mL, the chemiluminescence intensity of the detection system also increases accordingly. This indicates that the Fe3O4@L-Pr-MOF / Ab2 probe has a good response to changes in NFL concentration. The change in NFL concentration shows a good linear relationship with the change in chemiluminescence intensity of the detection system. The linear range for NFL detection is 1 pg / mL to 300 pg / mL, and the detection limit is calculated to be 0.33 pg / mL based on empirical values.

[0075] Test Example 6

[0076] This test example was designed to evaluate the anti-interference ability of the Fe3O4@L-Pr-MOF nanocomposite enzyme in detecting NFL. The detection procedure was the same as in Test Example 5, except that the target analyte NFL in the detection system was sequentially replaced with interfering substances that might be present in the actual sample, namely immunoglobulin G (IgG), carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), and prostate-specific antigen (PSA). After the reaction, the change in chemiluminescence signal intensity was measured. The specific results are as follows: Figure 11 As shown.

[0077] from Figure 11 It can be seen that when there are anti-interference substances that may coexist with NFL in the detection system, only NFL can significantly cause changes in the chemiluminescence signal, while other interfering substances do not show significant changes. This indicates that the Fe3O4@L-Pr-MOF / Ab2 probe described in this invention has strong anti-interference ability and is suitable for the detection of NFL in complex environments.

[0078] It should be noted that the above test examples are only test results of some embodiments of the present invention. The chiral MOFs magnetic nanocomposite enzymes of other embodiments of the present invention have similar performance, all of which can detect NFL in blood with high sensitivity and have strong anti-interference ability.

[0079] In summary, the chiral MOF magnetic nanocomposite enzyme described in this invention can utilize the peroxidase-like activity of the material to catalyze the oxidation of luminol, thereby amplifying the CL signal and constructing a highly sensitive CL immunosensor. Through a double-antibody sandwich protein recognition and CL detection technique, the porous Fe3O4@L-Pr-MOF structure can enhance antibody loading capacity and promote targeted antibody recognition during the immune response through chiral-specific interactions, achieving highly specific recognition of NFL and opening a new pathway for luminol-involved CL technology. This invention establishes a novel method for highly sensitive detection and specific recognition of the AD biomarker NFL, providing a detection method for early blood biomarkers of Alzheimer's disease and a new platform for AD drug development.

[0080] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. The use of chiral MOFs magnetic nanocomposite enzyme in the preparation of an Alzheimer's disease marker NFL detection tool, characterized by, The chiral MOFs magnetic nanocomposite enzyme comprises magnetic nanoparticles and chiral MOFs that are chemically bonded to the magnetic nanoparticles; the magnetic nanoparticles have iron oxide nanobeads as the core, and the outer surface of the iron oxide nanobeads is coated with a silica layer, the outer surface of which is modified with carboxyl groups. The chiral MOFs are constructed by coordination polymerization of iron salt with L-proline as the chiral ligand, or by coordination polymerization of zinc salt with L-histidine as the chiral ligand.

2. The application of the chiral MOF magnetic nanocomposite enzyme according to claim 1 in the preparation of an Alzheimer's disease biomarker, NFL detection tool, is characterized in that, The mass ratio of the magnetic nanoparticles to the chiral MOFs is 1:1-1.

2.

3. Use of the chiral MOFs magnetic nanohybrid enzyme according to claim 1 or 2 for the preparation of a tool for the detection of the Alzheimer's disease marker NFL, characterized in that, The method for preparing the chiral MOFs magnetic nanocomposite enzyme includes the following steps: preparing raw materials for the preparation of chiral MOFs and magnetic nanoparticles; using a solvothermal method to generate chiral MOFs from the raw materials for the preparation of chiral MOFs and coat the outer surface of the magnetic nanoparticles to obtain the chiral MOFs magnetic nanocomposite enzyme.

4. Use of chiral MOFs magnetic nanohybrid enzymes according to claim 3 for the preparation of a tool for the detection of the Alzheimer's disease marker NFL, characterized by, When the chiral MOFs are prepared using iron salts and L-proline, the preparation method includes the following steps: S1: Prepare iron salt solution, L-proline solution and magnetic nanoparticles; S2: The magnetic nanoparticles are ultrasonically dispersed in the iron salt solution, and then the L-proline solution is added under ultrasonic dispersion conditions to obtain a mixture; S3: The mixture is reacted at 70-85℃ for 16-25 h, and then the product is washed to obtain the chiral MOFs magnetic nanocomposite enzyme.

5. Use of chiral MOFs magnetic nanohybrid enzymes according to claim 4 for the preparation of a tool for the detection of the Alzheimer's disease marker NFL, characterized in that, In step S1, anhydrous ethanol is used as the solvent for both the iron salt solution and the L-proline solution.

6. The application of the chiral MOF magnetic nanocomposite enzyme according to claim 4 in the preparation of an Alzheimer's disease biomarker, NFL detection tool, is characterized in that... In step S1, the concentrations of the iron salt solution and the L-proline solution are both 100 mM; in step S2, 5-15 mg of the magnetic nanoparticles are added to every 1 mL of the iron salt solution, and the volume ratio of the L-proline solution to the iron salt solution is 1:

1.

7. The application of the chiral MOF magnetic nanocomposite enzyme according to claim 1 in the preparation of an Alzheimer's disease biomarker, NFL detection tool, is characterized in that, The chiral MOF magnetic nanocomposite enzyme was combined with an NFL antibody to form a probe, which was then detected using a double antibody sandwich method.

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