Method for regulating and controlling size of nano silicon dioxide and method for preparing DNA (Deoxyribose Nucleic Acid) tracer agent

Abstract

The invention discloses a nano silicon dioxide size control method and a DNA tracer preparation method, and the method comprises the following steps: mixing absolute ethyl alcohol, triethylamine and ultrapure water, and stirring to obtain an initial solution; adding tetraethoxysilane into the initial solution, stirring, standing and reacting for a period of time to obtain a silicon dioxide reaction stock solution; mixing the silicon dioxide reaction stock solution with absolute ethyl alcohol, and stirring; and adding tetraethoxysilane into the stirred mixed solution, reacting for a period of time, and repeating the operation until the silicon dioxide particles in the reactant reach the required size to obtain the final reactant. According to the method, complex reaction conditions are not needed, the method has a larger time advantage in obtaining the silicon dioxide inner core with the specific size, reaction from beginning to end is not needed to obtain the inner core with the specific particle size, the method has a better industrial production prospect, and the adaptability of the preparation process of the DNA tracer agent to different scenes is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to a method for regulating the size of nano silicon dioxide and a method for preparing a DNA tracer. Background Art

[0002] Different sizes of DNA tracers have different permeability in different scenarios. Choosing the size corresponding to the usage scenario makes the data more reliable. Different sizes of DNA tracers depend on the acquisition of nano-silica of different sizes. The existing method of obtaining nano-silica requires a reaction from beginning to end to obtain a core of a specific particle size, which results in a long time to obtain a silica core of a specific size, causing the DNA tracer to lack adaptability to different size demand scenarios.

[0003] Therefore, the applicant has developed a method for controlling the size of nano-silica and a method for preparing a DNA tracer to solve the above problems. Summary of the invention

[0004] The present invention provides a method for regulating the size of nano-silicon dioxide and a method for preparing a DNA tracer, so as to solve the problems in the prior art that it takes a long time to obtain a silicon dioxide core of a specific size and the DNA tracer lacks adaptability to scenarios with different size requirements.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: The present invention provides a method for controlling the size of nano-silicon dioxide, comprising the following steps: Anhydrous ethanol, triethylamine and ultrapure water are mixed and stirred to obtain an initial solution; Adding ethyl orthosilicate to the initial solution, stirring and standing for a period of time to react, to obtain a silicon dioxide reaction stock solution; Determine whether the size of the silica particles in the silica reaction stock solution reaches the required size. If so, obtain the final reactant. If not, mix the silica reaction stock solution with anhydrous ethanol and stir, add ethyl orthosilicate to the stirred mixture and react for a period of time, repeat the operation until the silica particles in the reactant reach the required size, and obtain the final reactant.

[0006] In this reaction, various raw materials are first mixed evenly by stirring, and ethyl orthosilicate is hydrolyzed to generate silanol Si-OH. As the hydrolysis reaction proceeds, silanol gradually forms a network structure of Si-O-Si under the catalysis of triethylamine. This condensation reaction causes the formation and growth of particles until a three-dimensional network structure of silica core is formed. Silica nucleates, and the hydroxyl groups on the surface are negatively charged. Under static conditions, positively charged triethylamine is adsorbed. As the inclusion of triethylamine increases, triethylamine produces a steric effect, preventing the silica surface from continuing to condense with free silanols or oligomers, inhibiting the growth of the particle size of the silica core. The balance point between the amount of triethylamine and ethyl orthosilicate and the size of silica is about 50 nanometers. The surface of silica synthesized in this way has a large number of reactive sites, and a large number of silanols and oligomers that have not reached the nucleation concentration are retained outside of triethylamine. When triethylamine is detached from adsorption, silica can continue to condense with silanol to increase the particle size. The most significant advantage of this method for synthesizing silica is that it does not require complicated reaction control steps, can be stored for a long time under static conditions, has a convenient reaction, and has the conditions for industrial preparation.

[0007] The concentration of silica in the silica reaction stock solution is diluted with anhydrous ethanol so that the cores are not easily agglomerated during the stirring process.

[0008] The adsorption equilibrium between triethylamine and silica is broken by stirring, exposing the hydroxyl groups on the surface of silica. At this time, free silanols and oligomers will condense on the surface of silica, and the silica particle size will increase.

[0009] The purpose of adding ethyl orthosilicate is to hydrolyze and replenish the silanols in the solution. The purpose of adding ethyl orthosilicate in small amounts and multiple times is to control the concentration of free silanols produced by hydrolysis, avoid secondary nucleation causing uneven silica size, and steadily increase the existing silica particle size.

[0010] Furthermore, anhydrous ethanol, triethylamine and ultrapure water in a volume ratio of 30:1:10 are mixed and stirred to obtain the initial solution.

[0011] Furthermore, anhydrous ethanol, triethylamine and ultrapure water were mixed, and stirred at a speed of 900 r / min at 25° C. for 20 minutes to obtain the initial solution.

[0012] Furthermore, the volume ratio of the initial solution to the added tetraethyl orthosilicate is 41:3.

[0013] Furthermore, ethyl orthosilicate was added to the initial solution, stirred at a speed of 900 r / min for 5 min, and allowed to react at 25° C. for 20-30 h to obtain the silicon dioxide reaction stock solution.

[0014] Furthermore, the silicon dioxide reaction stock solution and anhydrous ethanol in a volume ratio of 1:1 are mixed and stirred.

[0015] Furthermore, the diameter of the silica particles in the silica reaction stock solution is 50 nm, and the diameter of the silica particles in the final reactant is 50 nm-507 nm.

[0016] The particle size is adjusted between 50-507nm in order to meet the use requirements of the final synthesized DNA nanoparticles in different environments. For example, DNA nanoparticles below 200 nanometers can meet the requirements of circulation in the body and have a good in vivo circulation effect. DNA nanoparticles below 100 nanometers are more evenly distributed in the fluid, have a higher synchronization effect, and can also have a higher passability. Moreover, DNA nanoparticles of different nanometer sizes can be used to determine the connectivity and dominant channels of the channel. Silica exceeding 500 nanometers in size simply requires more times of superimposed silicon sources to extend the overall nucleation time. Moreover, after exceeding 500 nanometers, the concentration of silica in the stock solution can be further diluted by increasing the amount of silicon source added, or a larger-sized core can be used for micro-superposition to finely control the size of silica.

[0017] Furthermore, the silicon dioxide reaction stock solution was mixed with anhydrous ethanol and stirred at a speed of 500 r / min.

[0018] Furthermore, the volume ratio of the mixed liquid to the ethyl orthosilicate added therein is 4000:1-400:1.

[0019] Furthermore, ethyl orthosilicate is added to the stirred mixed solution and reacted for 20-50 minutes.

[0020] The present invention also provides a method for preparing a DNA nano-tracer, comprising the following steps: The final reactant obtained by the nano-silicon dioxide size control method is centrifuged, the supernatant is discarded, the centrifuged precipitate is resuspended, and then washed and centrifuged, and the solid after washing and centrifugation is dried; Dispersing the dried silicon dioxide with isopropanol, repeating the operation until the silicon dioxide is completely dispersed, to obtain a silicon dioxide isopropanol dispersion; APTES is added to the silica isopropanol dispersion and stirred, followed by centrifugation and discarding the supernatant, suspending the precipitate with isopropanol, vortexing and ultrasonicating in an ultrasonic bath, repeating the stirring and centrifugation operations in this step until unreacted APTES is completely removed, and finally drying the precipitate to obtain amino silica; Dispersing the amino-modified silica in ultrapure water, vortexing and sonicating in an ultrasonic bath, then adding the DNA solution, vortexing and sonicating in an ultrasonic bath, repeating the vortexing operation until the solution is uniform to obtain a dispersion, and then allowing the dispersion to stand; The dispersion is centrifuged and the supernatant is discarded, then the precipitate is suspended with ultrapure water, vortexed and sonicated in an ultrasonic bath until a uniform solution is formed, then centrifuged and the supernatant is discarded, then the precipitate is suspended with ultrapure water, vortexed and sonicated in an ultrasonic bath until a uniform solution is formed, then TMAPS methanol solution or APTES is added to the solution and vortexed, then tetraethyl orthosilicate is added, reacted at room temperature under vortexing, then tetraethyl orthosilicate is added to the solution, then the mixture is stirred, the stirred mixture is centrifuged and the supernatant is discarded to obtain a DNA tracer.

[0021] The beneficial effects of the present invention are: The present invention proposes a method for regulating the size of nano-silica and a method for preparing a DNA tracer, which do not require complicated reaction conditions, have a greater time advantage in obtaining a silica core of a specific size, do not require a reaction from beginning to end to obtain a core of a specific particle size, have better prospects for industrial production, and improve the adaptability of the preparation process of the DNA tracer to different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of 50 nm amino-containing silicon dioxide in the examples of this application; Figure 2 This is a scanning electron micrograph of 80 nm DNA nanoparticles in the examples of this application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0027] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0030] Anhydrous ethanol, triethylamine, tetraethyl orthosilicate, isopropanol, and APTES (γ-aminopropyltriethoxysilane) used in this application are all known commercially available products. The TMAPS methanol solution is a commercially available trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (50% in methanol) solution. The DNA dry powder is a commercially available product or a DNA dry powder designed by the user according to needs.

[0031] The preparation method of the DNA solution in this application is as follows: Two sample tubes containing 50 nmol / tube DNA dry powder were placed at room temperature for slow thawing for 10-15 minutes. They were centrifuged at 3000 r / min for 3 minutes to place the dry powder at the bottom of the tubes. 1 mL of ultrapure water was added to each tube to disperse the DNA dry powder. The tubes were centrifuged at 3000 r / min for 3 minutes. The solutions after centrifugation were taken out and added to 15 mL centrifuge tubes. The sample tubes were washed twice with 1 mL of ultrapure water and added to the 15 mL centrifuge tubes. 3.86 mL of ultrapure water were then added to the 15 mL centrifuge tubes (total volume 9.86 mL). At this time, the DNA concentration was 50 μg / mL to obtain a DNA solution.

[0032] The present invention is further described below by means of specific embodiments: Example 1: Preparation of 50 nm silicon dioxide.

[0033] Mix 15 mL of anhydrous ethanol, 0.5 mL of triethylamine and 5 mL of ultrapure water in a 25 mL round-bottom flask, stir the mixture at 900 r / min and 25°C for 20 min, then add 1.5 mL of tetraethyl orthosilicate (TEOS). Then stir the mixture at 900 r / min for 5 min, let it stand at 25°C for 24 h, monitor the diameter of silica, and obtain a 50 nm silica reaction stock solution.

[0034] The diameter monitoring method of silica can be achieved through existing particle size monitoring methods.

[0035] Example 2: Preparation of 187nm silicon dioxide Mix 15mL of anhydrous ethanol, 0.5mL of triethylamine and 5mL of ultrapure water in a 25mL round-bottom flask, and stir the mixture at 900r / min and 25°C for 20min. Then add 1.5mL of tetraethyl orthosilicate (TEOS). Then stir the mixture at 900r / min for 5min. Let it stand at 25°C for 24h. Stir 10mL of silica reaction stock solution with 10mL of anhydrous ethanol at 500r / min. Add 25μL of tetraethyl orthosilicate and react for 25min, monitor the diameter of silica, and repeat this operation twice to obtain a silica reaction stock solution of 187nm.

[0036] Example 3: Preparation of 206nm silicon dioxide Mix 15mL of anhydrous ethanol, 0.5mL of triethylamine and 5mL of ultrapure water in a 25mL round-bottom flask, and stir the mixture at 900r / min and 25°C for 20min. Then add 1.5mL of tetraethyl orthosilicate (TEOS). Then stir the mixture at 900r / min for 5min. Let it stand at 25°C for 24h. Stir 10mL of silica reaction stock solution with 10mL of anhydrous ethanol at 500r / min. Add 25μL of tetraethyl orthosilicate and react for 25min, monitor the diameter of silica, and repeat this operation 4 times to obtain a silica reaction stock solution of 206nm.

[0037] Example 4: Preparation of 213nm silicon dioxide Mix 15mL of anhydrous ethanol, 0.5mL of triethylamine and 5mL of ultrapure water in a 25mL round-bottom flask, and stir the mixture at 900r / min and 25°C for 20min. Then add 1.5mL of tetraethyl orthosilicate (TEOS). Then stir the mixture at 900r / min for 5min. Let it stand and react at 25°C for 24h. Stir 10mL of silica reaction stock solution with 10mL of anhydrous ethanol at 500r / min. Add 25μL of tetraethyl orthosilicate and react for 25min, monitor the diameter of silica, and repeat this operation 5 times to obtain a silica reaction stock solution of 213nm.

[0038] Example 5: Preparation of 507nm silicon dioxide core Mix 15mL of anhydrous ethanol, 0.5mL of triethylamine and 5mL of ultrapure water in a 25mL round-bottom flask, and stir the mixture at 900r / min and 25°C for 20min. Then add 1.5mL of tetraethyl orthosilicate (TEOS). Then stir the mixture at 900r / min for 5min. Let it stand and react at 25°C for 24h. Stir 10mL of silica reaction stock solution with 10mL of anhydrous ethanol at 500r / min. Add 50μL of tetraethyl orthosilicate and react for 20min, monitor the diameter of silica, and repeat this operation 13 times to obtain a silica reaction stock solution of 507nm.

[0039] In some embodiments, anhydrous ethanol, triethylamine, and ultrapure water in a volume ratio of 30:1:10 are mixed and stirred to obtain the initial solution.

[0040] In some embodiments, anhydrous ethanol, triethylamine and ultrapure water are mixed and stirred at 900 r / min at 25° C. for 20 min to obtain the initial solution.

[0041] In some embodiments, the volume ratio of the initial solution to the added tetraethyl orthosilicate is 41:3.

[0042] In some embodiments, ethyl orthosilicate is added to the initial solution, stirred at a speed of 900 r / min for 5 minutes, and allowed to react at 25° C. for 20-30 hours to obtain the silicon dioxide reaction stock solution.

[0043] In some embodiments, the silica reaction stock solution and anhydrous ethanol are mixed in a volume ratio of 1:1 and then stirred.

[0044] In some embodiments, the diameter of the silica particles in the silica reaction stock solution is 50 nm, and the diameter of the silica particles in the final reactant is 50 nm-507 nm.

[0045] The particle size is adjusted between 50-507nm in order to meet the use requirements of the final synthesized DNA nanoparticles in different environments. For example, DNA nanoparticles below 200 nanometers can meet the requirements of circulation in the body and have a good in vivo circulation effect. DNA nanoparticles below 100 nanometers are more evenly distributed in the fluid, have a higher synchronization effect, and can also have a higher passability. Moreover, DNA nanoparticles of different nanometer sizes can be used to determine the connectivity and dominant channels of the channel. Silica exceeding 500 nanometers in size simply requires more times of superimposed silicon sources to extend the overall nucleation time. Moreover, after exceeding 500 nanometers, the concentration of silica in the stock solution can be further diluted by increasing the amount of silicon source added, or a larger-sized core can be used for micro-superposition to finely control the size of silica.

[0046] In some embodiments, the silica reaction stock solution is mixed with anhydrous ethanol and stirred at a speed of 500 r / min.

[0047] In some embodiments, the volume ratio of the mixed solution to the ethyl orthosilicate added thereto is 4000:1-400:1.

[0048] In some embodiments, ethyl orthosilicate is added to the stirred mixture and the mixture is reacted for 20-50 minutes.

[0049] The present invention is further described below by taking a 50 nm silicon dioxide core as an example to prepare a DNA nano-tracer: Preparation of silicon dioxide isopropanol dispersion Centrifuge the 50nm silica core at 12000r / min for 3min, discard the supernatant, remove triethylamine and free silanol, resuspend with anhydrous ethanol, wash and centrifuge, repeat the washing operation twice to further remove ethyl orthosilicate and triethylamine. Finally, take the solid and dry it in a 60℃ forced air dryer for 4h to completely dry.

[0050] Disperse the silica with isopropanol (vortex for 30 seconds and sonicate in an ultrasonic bath for 15 minutes). Repeat until the silica is completely dispersed and there is no stratification or precipitation in the liquid. Prepare a 10 mg / mL silica isopropanol dispersion.

[0051] Amide modification of silica Take 20mL of silica isopropanol dispersion. Add 100μl APTES. Stir at 900r / min at 60℃ for 6h. Centrifuge at 12000r / min for 3min and discard the supernatant. Suspend the precipitate with isopropanol (vortex oscillation for 30s and ultrasonicate in an ultrasonic bath for 5min). Repeat the stirring and centrifugation operations in this step until the unreacted APTES is completely removed, and finally dry the precipitate in a 60℃ forced air dryer for 4h. 50mg 50nm amino silica (SiO 2 -NH 2 ).

[0052] Silica encapsulated DNA Prepare a DNA working solution with a concentration of 50 nmol / mL in ultrapure water. Disperse 50 mg of 50 nm amino-modified silica in 1 mL ultrapure water (vortex oscillation for 30 seconds and ultrasonication in an ultrasonic bath for 5 minutes), add 1 mL of DNA solution (vortex oscillation for 30 seconds and ultrasonication in an ultrasonic bath for 2 minutes) and repeat the dispersion operation until the solution is uniform. Let it stand for 25 minutes to allow the DNA to fully adsorb to the silica surface. Centrifuge the mixture at 16000 r / min for 5 minutes and discard the supernatant. Resuspend the precipitate with 1 mL ultrapure water, vortex oscillation for 30 seconds and ultrasonication in an ultrasonic bath for 2-5 minutes until a uniform solution is formed, then centrifuge at 16000 r / min for 5 minutes and discard the supernatant. Resuspend the precipitate with 8 mL ultrapure water, vortex oscillation for 30 seconds and ultrasonication in an ultrasonic bath for 2 minutes until a uniform solution is formed. Add 10 μL APTES and vortex oscillation for 30 seconds, then add 20 μL TEOS. The mixture was stirred at 900 r / min for 4 h at 25°C, and then 160 μL of TEOS (tetraethyl orthosilicate) was added to the solution. The mixture was stirred at 900 r / min for 48 h at 25°C. The mixture was centrifuged at 16000 r / min for 2-5 min, and the supernatant was discarded to obtain 80 nm DNA nanoparticles (SiO 2 -DNA-SiO 2 ), namely DNA nanotracer.

[0053] The scanning electron microscopy image of 50 nm amination silicon dioxide in the present application example is as follows Figure 1As shown, the scanning electron microscopy image of the 80nm DNA nanoparticles prepared based on the 50nm silica core in the embodiment of the present application is as follows Figure 2 shown.

[0054] The advantages of the present invention compared to the prior art are: 1. A large number of silica cores of about 50 nanometers can be prepared at one time without complicated reaction conditions. In the present invention, triethylamine is both a catalyst and can adsorb with negatively charged silica after nucleation to prevent the silica from continuing to grow, which is conducive to the synthesis of small-particle silica cores, and the reaction process will not be affected by the reaction volume, which is conducive to large-scale production; 2. Mix the 50-nanometer silica core stock solution with anhydrous ethanol. Add ethyl orthosilicate and react for 20-50 minutes, and repeat this operation. The silica particle size can be adjusted between 50nm and 507nm. The silica particle size is adjustable and can be constructed for different application scenarios. The nanoparticles can move synchronously with the fluid. Data reliability is improved; 3. By repeatedly superimposing silicon sources in trace amounts, the time required to prepare a silicon dioxide core of a specific size is shortened. By repeatedly superimposing silicon sources in trace amounts, the market demand for control of parameters such as particle size can be met more quickly without the need to readjust the core synthesis parameters. 4. Multiple micro-additions can avoid the enlargement effect of the core in the expanded production, which has better prospects for industrial production. The hydrolysis and polycondensation of the silicon source occur successively and exist simultaneously. The change in the reaction rate of the two will make the number of nuclei and the particle size uncontrollable. Multiple micro-additions of silicon source after the core stock solution is diluted can avoid the conflict between particle size control and nucleation control, which is conducive to the condition control in the industrial production process. At the same time, it also avoids the experimental results after the experimental parameters are expanded from being affected by the enlargement effect caused by factors such as stirring.

[0055] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling the size of nano-silicon dioxide, characterized in that: The following steps are involved: Anhydrous ethanol, triethylamine and ultrapure water are mixed and stirred to obtain an initial solution; Adding ethyl orthosilicate to the initial solution, stirring and standing for a period of time to react, to obtain a silicon dioxide reaction stock solution; Determine whether the size of the silica particles in the silica reaction stock solution reaches the required size. If so, obtain the final reactant. If not, mix the silica reaction stock solution with anhydrous ethanol and stir, add ethyl orthosilicate to the stirred mixture and react for a period of time, repeat the operation until the silica particles in the reactant reach the required size, and obtain the final reactant.

2. A method for controlling the size of nano-silicon dioxide according to claim 1, characterized in that: Anhydrous ethanol, triethylamine and ultrapure water in a volume ratio of 30:1:10 were mixed and stirred to obtain the initial solution.

3. A method for controlling the size of nano-silicon dioxide according to claim 1 or 2, characterized in that: After mixing anhydrous ethanol, triethylamine and ultrapure water, the mixture was stirred at a speed of 900 r / min at 25° C. for 20 min to obtain the initial solution.

4. A method for controlling the size of nano-silicon dioxide according to claim 1, characterized in that: The volume ratio of the initial solution to the added ethyl orthosilicate is 41:

3.

5. A method for controlling the size of nano-silicon dioxide according to claim 1 or 4, characterized in that: Add ethyl orthosilicate to the initial solution, stir at a speed of 900 r / min for 5 minutes, and allow to react at 25° C. for 20-30 hours to obtain the silicon dioxide reaction stock solution.

6. A method for controlling the size of nano-silicon dioxide according to claim 1, characterized in that: The silica reaction stock solution and anhydrous ethanol were mixed in a volume ratio of 1:1 and stirred.

7. A method for controlling the size of nano-silicon dioxide according to claim 1, characterized in that: The diameter of the silica particles in the silica reaction stock solution is 50 nm, and the diameter of the silica particles in the final reactant is 50 nm-507 nm.

8. A method for controlling the size of nano-silicon dioxide according to claim 7, characterized in that: The volume ratio of the mixed liquid to the ethyl orthosilicate added therein is 4000:1-400:

1.

9. A method for controlling the size of nano-silicon dioxide according to claim 1 or 8, characterized in that: Add ethyl orthosilicate to the stirred mixture and allow to react for 20-50 minutes.

10. A method for preparing a DNA tracer, characterized in that: The following steps are involved: Centrifuge the final reactant obtained by the method for controlling the size of nano-silicon dioxide according to any one of claims 1 to 9, discard the supernatant, resuspend the centrifuged precipitate, wash and centrifuge it, and dry the solid after washing and centrifugation; Dispersing the dried silicon dioxide with isopropanol, repeating the operation until the silicon dioxide is completely dispersed, to obtain a silicon dioxide isopropanol dispersion; APTES is added to the silica isopropanol dispersion and stirred, followed by centrifugation and discarding the supernatant, suspending the precipitate with isopropanol, vortexing and ultrasonicating in an ultrasonic bath, repeating the stirring and centrifugation operations in this step until unreacted APTES is completely removed, and finally drying the precipitate to obtain amino silica; The amino-modified silica is dispersed in ultrapure water, vortexed and sonicated in an ultrasonic bath, and then the DNA working solution is added, vortexed and sonicated in an ultrasonic bath, and the dispersion operation is repeated until the solution is uniform to obtain a dispersion solution, and then the dispersion solution is allowed to stand; The dispersion is centrifuged and the supernatant is discarded, then the precipitate is suspended with ultrapure water, vortexed and sonicated in an ultrasonic bath until a uniform solution is formed, then centrifuged and the supernatant is discarded, then the precipitate is suspended with ultrapure water, vortexed and sonicated in an ultrasonic bath until a uniform solution is formed, then TMAPS methanol solution or APTES is added to the solution and vortexed, then tetraethyl orthosilicate is added, reacted at room temperature under vortexing, then tetraethyl orthosilicate is added to the solution, then the mixture is stirred, the stirred mixture is centrifuged and the supernatant is discarded to obtain a DNA tracer.

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