Recyclable magnetic DNA track as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of DNA tracks, and particularly relates to a recoverable magnetic DNA track as well as a preparation method and application thereof. Through a magnetic DNA track mediated recognition mode and a label-free detection method in the invention, sustainable detection of virus RNA is realized, the detection limit is as low as 0.9 fM, and high sensitivity and specificity are achieved. Besides, the magnetic DNA track provided by the invention provides an innovative and sustainable platform for detecting virus RNA, and has a great application prospect in the aspects of diagnosis of coronavirus diseases, food safety evaluation, environmental monitoring and the like, and the sustainable DNA track is beneficial to reducing resource waste and economic burden.

Description

Technical Field

[0001] The invention belongs to the technical field of DNA tracks, and in particular relates to a recyclable magnetic DNA track and a preparation method and application thereof. Background Art

[0002] DNA molecular machines are artificial molecular machines that are driven by biological motors such as myosin, kinesin and dynein, and are constructed by taking advantage of the good programmability, predictability and ease of synthetic modification of DNA molecules. Currently, DNA molecular machines with various functions have been constructed, such as DNA motors, DNA walkers, DNA tweezers, DNA gears and DNA robots. Due to their simple operation and rapid response capabilities, people are increasingly interested in developing fluorescent DNA motor biosensors.

[0003] DNA motor tracks can be classified into three types according to their dimensions: one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D). One-dimensional DNA tracks are usually characterized by linear structures. Bath et al. proposed a reversible DNA motor using one-dimensional tracks. Two-dimensional DNA tracks facilitate 180-degree directional motion. For example, Chen et al. developed a dual-drive DNA motor that runs on a DNA-modified metal-organic gel plane. Three-dimensional DNA tracks allow 360-degree directional selection and are usually associated with DNA-modified nanoparticles. Due to the DNA enrichment and signal amplification properties of nanoparticles, many DNA motors have been designed for biosensing applications of three-dimensional DNA tracks. For example, Zhong et al. introduced a self-feedback DNAzyme motor with cascade amplification for mRNA imaging in living cells, while Wang et al. proposed a highly integrated, biostable, self-driven DNA motor for autonomous operation in vivo, which improved mRNA imaging. However, DNA motors perform walking functions by consuming the material in the track. Therefore, whether running in a one-dimensional, two-dimensional, or three-dimensional track, the motor stops moving after the material is completely exhausted, resulting in the track being wasted. Therefore, there is an urgent need to construct a reproducible DNA track to achieve the detection of targets and optimize the utilization of the track in DNA motors. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a magnetic DNA track and a preparation method and application thereof. By using magnetic separation technology, the DNA track can be effectively separated under an external magnetic field, and the DNA track can be regenerated by adding hairpin structures and recognition sequences that are exhausted during the movement, thereby restoring the target recognition and signal output functions.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] The first aspect of the present invention provides a recyclable magnetic DNA track, wherein the magnetic DNA track is a signal probe and a recognition probe fixed on streptavidin-conjugated magnetic nanobeads through the affinity of streptavidin and biotin; and the magnetic nanobeads are magnetically attracted to achieve the recovery of the magnetic DNA track; The signal probe is formed by connecting the recognition sequence shown in SEQ ID NO.1 and the walking sequence shown in SEQ ID NO.2 through complementary base pairing; The recognition probe is formed by connecting the hairpin structure sequence shown in SEQ ID NO.4 and the connecting sequence shown in SEQ ID NO.3 through base complementary pairing; The 5' end of the walking sequence and the 5' end of the linker sequence are both labeled with biotin.

[0007] The present invention modifies the signal probe and the recognition probe on the magnetic nanobeads, so that after the magnetic DNA track is introduced into the target, the recognition sequence in the signal probe binds to the target, thereby releasing the walking sequence. The magnetic DNA track that releases the walking sequence is the DNA motor, and the DNA motor is gradually and autonomously walked through the walking sequence. When the DNA motor is running, the hairpin structure is exhausted, and only the connection sequence and the walking sequence are left on the track. Using magnetic separation technology, the DNA track can be effectively separated under an external magnetic field. Subsequently, by adding the hairpin structure and recognition sequence exhausted in the previous movement process, the regeneration of the DNA track is achieved, thereby restoring the target recognition and signal output functions.

[0008] The second aspect of the present invention provides a method for preparing the magnetic DNA track, comprising the following steps: The recognition sequence and walking sequence were annealed in TAE / Mg buffer at 95°C to 98°C for 5 min to 6 min, and then gradually cooled to 30°C to obtain a signal probe; The hairpin structure sequence and the linker sequence are mixed in TAE / Mg buffer to obtain a recognition probe; The signal probe, the recognition probe and the magnetic nano-beads are incubated in a Tris-HCl buffer at 23° C. to 25° C. for 120 min to 150 min to obtain the magnetic DNA track.

[0009] In another preferred embodiment, each liter of TAE / Mg buffer contains the following ingredients: 40mM~40.5mM Tris, 20mM~20.5mM acetic acid, 2mM~2.5mM EDTA, 12.5mM~12.6mM magnesium acetate.

[0010] In another preferred embodiment, the incubation process of the signal probe, the recognition probe and the magnetic nanobeads further includes adding a blocking solution, wherein the blocking solution is a mixture of Tris buffer and BSA buffer in a volume ratio of 19:1 to 1.01.

[0011] A third aspect of the present invention provides an application of a magnetic DNA track in the preparation of a product for detecting viruses.

[0012] In another preferred embodiment, the virus is SARS CoV-2.

[0013] A fourth aspect of the present invention provides a method for detecting SARS CoV-2 for non-diagnostic purposes, comprising the following steps: The sample to be tested is mixed with the magnetic DNA track, incubated at 35°C to 37°C for 70min to 75min, Exo III, Tris-HCl buffer and Exo III reaction buffer are added and incubated for 40min to 42min, N-methylporphyrin dipropionic acid and KCl solution are added and incubated for 40min to 42min, and then fluorescence detection is performed to determine whether SARS CoV-2 is still present in the sample to be tested according to the fluorescence intensity; After the fluorescence detection, the magnetic DNA track is recovered for the next detection.

[0014] In another preferred embodiment, the specific process of recycling the magnetic DNA track is as follows: performing magnetic recovery on the magnetic DNA track after SARS CoV-2 detection to obtain a recovered magnetic DNA track; After washing the recovered magnetic DNA track, the hairpin structure and the recognition sequence are added, mixed and stirred to complete the regeneration of the magnetic DNA track.

[0015] In another preferred embodiment, the mixing and stirring time is 120 min to 125 min, and the rotation speed is 18 rpm / min to 20 rpm / min.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention realizes the regeneration of magnetic DNA track by magnetic separation method, and simultaneously modifies the signal probe and the recognition probe on the surface of magnetic nanobeads to create a magnetic DNA track. After the target is introduced, the progressive and autonomous walking of the DNA motor is activated. When the DNA motor is running, the hairpin structure is exhausted, and only the connection sequence and the walking sequence are left on the track. Using magnetic separation technology, the DNA track can be effectively separated under an external magnetic field. Subsequently, by adding the hairpin structure and recognition sequence exhausted in the previous movement process, the regeneration of the DNA track is achieved, thereby restoring the target recognition and signal output functions.

[0017] The present invention is based on a renewable DNA track-mediated recognition method and a label-free detection method, which achieves sustainable detection of viral RNA with a detection limit as low as 0.9 fM. The method has high sensitivity and specificity. In addition, the track-regenerated DNA motor proposed in this study provides an innovative and sustainable platform for detecting viral RNA, which has great application prospects in the diagnosis of coronavirus diseases, food safety assessment and environmental monitoring, and the sustainable use of DNA tracks helps reduce resource waste and economic burden. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the working principle of the magnetic DNA track.

[0019] Figure 2 The figure shows the gel electrophoresis of SARS-CoV-2 RNA detection and the characterization of the practicality of sustainable detection of magnetic DNA orbitals; (a) is based on the gel electrophoresis, band a is SARS-CoV-2 RNA, band b is RP, band c is SP, band d is RP+SP, band e is SARS-CoV-2 RNA+RP, band f is SARS-CoV-2 RNA+RP+SP, band g is SARS-CoV-2 RNA+RP+SP+Exo Ⅲ, and band M is DNA Ladder Marker; (b) is a characterization of the practicality of sustainable detection of magnetic DNA orbitals. DNA orbit represents magnetic DNA orbit, RE-1~RE-8 represents the number of cycles, Negative control system represents negative control, and Positive control system represents positive control.

[0020] Figure 3 The graphs show the effects of RP and SP concentrations on fluorescence intensity; (a) shows the effects of RP concentration on fluorescence intensity, and (b) shows the effects of SP concentration on fluorescence intensity.

[0021] Figure 4 The results of the graphs showing the effects of different conditions on fluorescence intensity; among them, (a) is the effect of DNA track concentration, (b) is the effect of Exo Ⅲ dosage, (c) is the effect of the first stage reaction time, and (d) is the effect of the second stage reaction time.

[0022] Figure 5 The fluorescence spectra and relative fluorescence intensity diagrams of the magnetic DNA track under different SARS-CoV-2 RNA concentrations; (a) is the fluorescence spectrum diagram, (b) is the fluorescence intensity diagram, and b1 is the regression equation diagram.

[0023] Figure 6 Figure 2 is the fluorescence intensity response diagram of the magnetic DNA track to different targets. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0025] Sensors and Actuators B: Chemical reports a renewable detection method for viral RNA. The method consists of a track hairpin labeled with a fluorescent group and a quenching group, AuNPs functionalized with dozens of roadbed chains, and locked walking chains. By adding the target, the walking chain is released and hybridized with the exposed domains in the track chain to form a triple complex. Subsequently, it is gradually digested by Exo III, resulting in track consumption. The fluorescent group that was previously quenched by fluorescence energy resonance transfer to AuNP is released to produce fluorescence. Finally, the track hairpin labeled with a fluorescent group and a quenching group is re-added to the solution, resulting in track regeneration and sustainable use of the track.

[0026] The disadvantage of this method is that the hairpin molecular beacon labeled with the fluorescent group and the quenching group is unstable and expensive. The hairpin molecular beacon cannot be completely bound to the template during hybridization and has poor stability. In addition, the hairpin molecular beacon has a hairpin structure in the free state, and the fluorescent group and the quenching group are close to each other, which will cause the fluorescence to be quenched, affecting the sensitivity and accuracy of the detection. The regeneration track is not separated. This method does not separate the track, but chooses to directly add the hairpin molecular beacon again into the mixed solution so that it can be recycled multiple times. As the solution mixture increases, this method may affect the operating efficiency of the machine and the accuracy of the detection.

[0027] The materials and instruments involved in the following examples are: The sequences of the DNA oligonucleotides used are shown in Table 1. Streptavidin-labeled magnetic beads were synthesized and purified by Shanghai Shenggong Biotechnology Co., Ltd. (Shanghai, China). Exonuclease III (Exo III) was provided by Thermo Fisher Scientific Inc. (Shanghai, China). Serum samples were obtained from Shandong Provincial Hospital Affiliated to Shandong First Medical University. Other chemicals were of analytical grade and provided by standard reagent suppliers. Buffers were prepared with ultrapure water (>18.25 MΩ·cm).

[0028] Table 1 Oligonucleotide sequence information Note: The underlined part indicates the G-quadruplex sequence.

[0029] This example selects SARS CoV-2 RNA as a target model and proposes a method for measuring specific targets based on magnetic DNA tracks. The principle is as follows: Figure 1 As shown. The magnetic DNA track mainly consists of three parts: streptavidin-ylated MNB, signal probe SP, and recognition probe RP. The process first fixes the signal probe and recognition probe on the surface of MNB through the affinity of streptavidin and biotin to prepare a magnetic DNA track. The target detection process can be divided into three different stages. In the initial stage, the target molecule binds to the recognition sequence in the recognition probe, resulting in the release of the walking sequence. The released walking sequence hybridizes with the complementary sequence of the hairpin structure in the SP, and replaces the hairpin structure in the SP through a chain displacement reaction, thereby producing a double-stranded DNA product. Subsequently, Exo III recognizes the double-stranded DNA product and catalyzes the removal of the single nucleotide on the 3' end, resulting in the release of the walking sequence and the G-quadruplex. The released walking sequence then binds to another SP to initiate the next round of reaction. Finally, K is added + The G-quadruplex folding is promoted and then binds to NMM, ultimately generating a strong fluorescence signal, achieving signal amplification and sensitive detection of the target.

[0030] The regeneration process of the DNA track is divided into two different stages. In the first stage, an external magnetic field is applied to the reaction product, the supernatant is discarded, and the used DNA track is collected and purified. In the second stage, the recognition sequence and hairpin structure are added, and finally they are fixed on the track by hybridization with the walking sequence and the connecting sequence respectively. This method achieves the regeneration of the DNA track and restores its functions related to target recognition, signal transduction and signal output for future applications.

[0031] 1. Preparation of magnetic DNA tracks The lyophilized recognition sequence DNA powder, walking sequence hydrolyzed DNA powder, and linker sequence hydrolyzed DNA powder were diluted with TE buffer (10 mM Tris and 1.0 mM Na2EDTA, pH 8.0) for subsequent experiments.

[0032] Take 5 μL of the recognition sequence with a concentration of 1 μM and 5 μL of the walking sequence with a concentration of 1 μM and mix them to obtain a mixture. The mixture is annealed in 40 μL of TAE / Mg buffer (40 mM Tris, 20 mM acetic acid, 2 mM EDTA, 12.5 mM magnesium acetate, pH 8.0) at 95°C for 5 min, and then gradually cooled to 30°C to synthesize a signal probe with a final concentration of 0.1 μM.

[0033] 5 μL of a hairpin structure with a concentration of 20 μM and 5 μL of a linker sequence with a concentration of 20 μM were mixed in 10 μL of TAE / Mg buffer to obtain a recognition probe with a final concentration of 5.0 μM.

[0034] 10 μL of magnetic nanobeads were washed five times with 100 μL of buffer (10 mM Tris, 0.05% (w / v) TritonTM X-100, pH 7.4), and the washed MNBs were resuspended with 40 μL of Tris-HCl buffer (10 mM Tris, 100 mM NaCl, 10 mM KCl, pH 7.4) to a final concentration of 5.0 mg / mL to obtain a magnetic nanobead solution.

[0035] After mixing 3 μL of magnetic nanoparticle solution, 5 μL of signal probe and 5 μL of recognition probe, incubate with 17 μL of Tris-HCl buffer at 23°C for 120 min. To reduce nonspecific adsorption, add 10 μL of blocking solution (50 mM Tris and 5% (w / v) BSA, pH 7.4) and incubate at room temperature for 60 min. Wash three times with 50 μL of washing buffer to obtain the final product, which is resuspended in 10 μL of Tris-HCl buffer to form a magnetic DNA track with a final concentration of 1.5 mg / mL.

[0036] 2. Gel electrophoresis analysis A 15% polyacrylamide gel was prepared. Then, the sample to be tested was mixed with the loading buffer at a volume ratio of 5:1 and added to the gel for electrophoresis for 2 h (15 °C, current 30 mA). Finally, the gel was stained with 1×SYBR Gold solution for 40 min and imaged using a chemiluminescent gel imaging system.

[0037] 3. Fluorescence detection 10 μL of SARS-CoV-2 RNA was mixed with 10 μL of magnetic DNA track and incubated at 37°C for 75 min. Subsequently, 0.5 μL of 20 U / μL Exo III, 9.5 μL Tris-HCl buffer and 3 μL Exo III reaction buffer were added and mixed, and incubated at 37°C for 90 min. Then, 4.0 mM, 5 μL N-methylporphyrin dipropionic acid and 2.0 mM, 5 μL KCl solution were added and incubated at 37°C for 40 min. Finally, fluorescence detection was performed using a fluorescence spectrophotometer with an excitation wavelength of 399 nm, a bandwidth of 10 nm, a detector voltage of the photomultiplier tube (PMT) set to 400 V, and fluorescence intensity measured at 618 nm.

[0038] 4. Track regeneration The mixture after fluorescence detection was placed in a magnetic separator (Thermo Fisher Scientific Co., Ltd. (Shanghai, China)) and adsorbed using an external magnet. Subsequently, the supernatant was slowly removed and the used magnetic DNA tracks were collected.

[0039] The collected magnetic DNA tracks were washed five times with washing buffer (10 mM Tris, 0.05% (w / v) TritonTM X-100, pH=7.4), and 0.1 μM, 5 μL of the recognition sequence and 5.0 μM, 5 μL of the hairpin structure were added to the collected magnetic DNA tracks, which were rotated at 18 rpm / min for 120 min at room temperature.

[0040] The magnetic DNA track was resuspended in 10 μL of Tris-HCl buffer and washed three times using an external magnet to remove all unbound recognition sequences and hairpin structures to complete the regeneration of the magnetic DNA track.

[0041] 5. SARS-CoV-2 RNA sample detection The N gene sequence extracted from SARS-CoV-2 RNA was integrated into the pUC57 vector to generate a recombinant plasmid, which subsequently served as a virus mimic.

[0042] 6. Results 1) Feasibility verification of sustainable detection of viral RNA The detection process of this method was characterized by native polyacrylamide gel electrophoresis, such as Figure 2 As shown in (A). SARS-CoV-2 RNA is band a, RP is band b, SP is band c, and the mixture of RP and SP is band d. It can be seen in band e that the appearance of two new bands indicates the formation of an RNA / recognition sequence complex, and the walking sequence is released at the same time, thereby successfully identifying the target. It can be seen from band f with the addition of SP that a new band with the slowest migration rate was observed, which is consistent with the disappearance of the walking sequence and the appearance of the connecting sequence. This indicates that a walking sequence / hairpin structure complex has been formed. In band g with the addition of ExoIII, it can be seen that the intensity of the bands related to the walking sequence / hairpin structure complex decreases, and the bands of the walking sequence and the G-quadruplex appear. The results show that the complex is degraded by Exo III, and the above results prove that the magnetic DNA track in the present invention can sustainably detect viral RNA.

[0043] To further verify the practicality of sustainable detection by magnetic DNA tracks, the use of regenerated magnetic DNA tracks to identify novel SARS-CoV-2 RNA was characterized, e.g. Figure 2As shown in b, it can be seen that the magnetic DNA track can be regenerated up to 8 times, and the fluorescence response remains relatively stable in the first 6 regenerations. However, starting from the 7th regeneration, the fluorescence response gradually weakened despite maintaining the same concentration of SARS-CoV-2 RNA. This decline can be caused by partial loss of the track during the magnetic separation process. The first 6 regenerations did not impair its detection ability, while subsequent regenerations resulted in reduced detection ability. These results show that the proposed magnetic DNA track can be regenerated up to 6 times without degradation of performance, indicating that the magnetic DNA track is suitable for continuous detection of viral RNA.

[0044] 2) Optimization of experimental conditions To achieve the best analytical performance, the experimental conditions such as the concentration of RP and SP, the concentration of magnetic DNA tracks, the amount of Exo III, and the first and second stage reaction times were optimized, e.g. Figure 3 When the concentration of RP is 0.1μM and the concentration of SP is 5.0μM, the fluorescence intensity of the system reaches the maximum value. Therefore, the optimal concentrations of RP and SP are 0.1μM and 5.0μM, respectively. Figure 4 In a, the concentration of the magnetic DNA track was optimized in the range of 0.5 mg / mL to 2.0 mg / mL. The fluorescence intensity gradually increased with the increase of the concentration of the magnetic DNA track and reached a plateau at 1.5 mg / mL. Therefore, the optimal concentration of the DNA track is 1.5 mg / mL. Figure 4 In b, the dosage of Exo III was optimized from 2.0U to 12.0U, and the fluorescence intensity was stabilized at 10.0U. Therefore, the optimal concentration of Exo III was 10.0U. In addition, the reaction time of the first and second reaction stages was also optimized. Figure 4 As shown in Figure c, the fluorescence intensity of the first stage increases with the increase of reaction time and tends to stabilize after 75 minutes. At the same time, the fluorescence intensity of the second stage reaches equilibrium after 90 minutes, as shown in Figure d. Figure 4 Therefore, the optimal reaction time for the first stage is 75 min, and the optimal reaction time for the second stage is 90 min.

[0045] 3) Sensitivity analysis Under optimal reaction conditions, the sensitivity was evaluated by the fluorescence response of SARS-CoV-2 RNA, as Figure 5 As shown in a, the sensitivity gradually increases with the increase of SARS-CoV-2 RNA concentration. This indicates that SARS-CoV-2 RNA concentration plays a key role in target recognition and signal amplification. Figure 5b, In the range of 5.0fM~0.1μM, the fluorescence intensity is linearly correlated with the SARS-CoV-2 RNA concentration, and the regression equation is FI=2324.7+592.4 lgC(R 2 =0.998), FI represents fluorescence intensity, and C represents the corresponding SARS-CoV-2 RNA concentration. The limit of detection (LOD) of SARS-CoV-2 RNA is 0.9fM, which meets the 3σ standard.

[0046] 4) Specificity analysis To verify the specificity of this method, different sequences were tested, including single-base mismatch M1, double-base mismatch M2, triple-base mismatch M3, and complete mismatch MN. Figure 6 As shown in the figure, under the same reaction conditions, a significant fluorescence response was detected only when the target SARS-CoV-2 RNA was present, while the signals generated by the mismatched sequences of M1, M2, M3, and MN were weaker, comparable to the blank control. The above results show that the proposed method has good specificity for viral RNA detection.

[0047] 5) Analysis of clinical serum samples To further verify the reliability of the magnetic DNA track, experiments were conducted by adding SARS-CoV-RNA at spike concentrations of 1.0nM, 10pM, and 0.1pM to human serum. The results are shown in Table 2. The recovery rates were 93.76%, 97.53%, and 102.8%, and the RSDs were 1.3%, 1.5%, and 1.6%, respectively. These results indicate that this method has strong reliability and application potential for detecting viral RNA in clinical serum samples.

[0048] Table 2 Recovery rate of SARS-CoV-2 RNA in serum samples Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Obviously, various changes and modifications may be made to the present invention by those skilled in the art without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such changes and modifications if they fall within the scope of the technical equivalents of the present invention.

Claims

1. A recyclable magnetic DNA track, characterized in that The magnetic DNA track is to fix the signal probe and the recognition probe on the streptavidin-conjugated magnetic nanobeads through the affinity of streptavidin and biotin; and the magnetic nanobeads are magnetically attracted to realize the recovery of the magnetic DNA track; The signal probe is formed by connecting the recognition sequence shown in SEQ ID NO.1 and the walking sequence shown in SEQ ID NO.2 through complementary base pairing; The recognition probe is formed by connecting the hairpin structure sequence shown in SEQ ID NO.4 and the connecting sequence shown in SEQ ID NO.3 through base complementary pairing; The 5' end of the walking sequence and the 5' end of the linker sequence are both labeled with biotin.

2. A method for preparing a magnetic DNA track according to claim 1, characterized in that: The following steps are involved: The recognition sequence and walking sequence were annealed in TAE / Mg buffer at 95°C to 98°C for 5 min to 6 min, and then cooled to obtain a signal probe; The hairpin structure sequence and the linker sequence are mixed in TAE / Mg buffer to obtain a recognition probe; The signal probe, the recognition probe and the magnetic nano-beads are incubated in a Tris-HCl buffer at 23° C. to 25° C. for 120 min to 150 min to obtain the magnetic DNA track.

3. The method for preparing a magnetic DNA track according to claim 2, characterized in that: Each liter of the TAE / Mg buffer contains the following ingredients: 40mM~40.5mM Tris, 20mM~20.5mM acetic acid, 2mM~2.5mM EDTA, 12.5mM~12.6mM magnesium acetate.

4. The method for preparing a magnetic DNA track according to claim 2, characterized in that: The incubation process of the signal probe, the recognition probe and the magnetic nano-beads also includes adding a blocking solution, which is a mixture of Tris buffer and BSA buffer in a volume ratio of 19:1-1.

01.

5. Use of the magnetic DNA track according to claim 1 in the preparation of products for detecting viruses.

6. The use according to claim 7, characterized in that: The virus is SARS CoV-2.

7. A method for detecting SARS CoV-2 for non-diagnostic purposes, characterized in that: The following steps are involved: Mixing the sample to be tested with the magnetic DNA track according to claim 1, incubating at 35°C to 37°C for 70min to 75min, adding Exo III, Tris-HCl buffer and Exo III reaction buffer and incubating for 40min to 42min, adding N-methylporphyrin dipropionic acid and KCl solution and incubating for 40min to 42min, and then performing fluorescence detection to determine whether SARS CoV-2 is still present in the sample to be tested according to the fluorescence intensity; After the fluorescence detection, the magnetic DNA track is recovered and regenerated for the next detection.

8. The method for detecting SARS CoV-2 for non-diagnostic purposes according to claim 7, characterized in that: The specific process of recycling the magnetic DNA track is as follows performing magnetic recovery on the magnetic DNA track after SARS CoV-2 detection to obtain a recovered magnetic DNA track; After washing the recovered magnetic DNA track, the hairpin structure and the recognition sequence are added, mixed and stirred to complete the regeneration of the magnetic DNA track.

9. The method for detecting SARS CoV-2 for non-diagnostic purposes according to claim 8, characterized in that: The mixing and stirring time is 120 min to 125 min, and the rotation speed is 18 rpm / min to 20 rpm / min.

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