CN105126716A - Method for preparing sulfydryl modified ferroferric oxide/silicon dioxide magnetic nanoparticles - Google Patents

Abstract

The invention discloses a preparation method of thiol-modified iron ferric oxide/silicon dioxide magnetic nanoparticles, comprising the following steps: 1) preparing magnetic iron ferric oxide particles by a solvothermal method using ferric salt as a raw material; 2) Using tetraethyl orthosilicate as a silicon source, the silicon dioxide produced is coated on the surface of magnetic ferric oxide particles by a sol-gel method to form ferric oxide/silicon dioxide magnetic nanoparticles; 3) four Ferric oxide/silicon dioxide magnetic nanoparticles are placed in toluene solution, dispersed uniformly to obtain solution A; dimercaptosuccinic acid is added to dimethyl sulfoxide solution, dispersed uniformly to obtain solution B; then solution A and solution B Mixing and stirring for a period of time, solid-liquid separation, washing, and drying to obtain mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles. The magnetic nano particle of the invention has good dispersion performance, good stability and biocompatibility, and has potential application value in the field of biomedicine.

Description

A kind of preparation method of mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles

technical field

The invention belongs to the field of medical materials, in particular to a preparation method of mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles.

Background technique

Due to their special magnetic properties, magnetic nanoparticles have broad application prospects in the field of biomedicine, which can be summarized into two types: in vitro application and in vivo application. In in vitro applications, it can be used to label and separate cells, proteins, DNA, bacteria and viruses, etc.; in in vivo applications, it can be used as a contrast agent for magnetic resonance imaging, a drug carrier, and overheating to treat tumors. Magnetic nanoparticles represented by iron oxides will make great contributions to human health in the near future. In order to enable magnetic nanoparticles to better serve human health as soon as possible, basic research on the preparation, modification, and functionalization of nanoparticles is necessary and one of the current research hotspots.

The preparation methods of magnetic nanomaterials can be divided into physical methods, biological methods and chemical methods. Among them, the physical method is mainly the mechanical ball milling method, which produces a wide particle size distribution, takes a long time, consumes a lot of energy, and is easy to introduce impurities, so it is not suitable for the preparation of biomedical magnetic nanomaterials. Magnetic nanoparticles prepared by biological methods have good biocompatibility, but large-scale cultivation is difficult, and the particle extraction process is cumbersome, and the controllable range of particle size is limited. Therefore, the preparation of nano-magnetic materials currently mainly depends on chemical preparation methods, among which the co-precipitation method is simple to operate and has a large yield, but it is difficult to obtain particles with uniform particle size distribution, such as the Chinese invention patent (application publication number: CN103990423A). In the preparation process of microemulsion method, a large amount of oily solvent and surfactant need to be added, which is not easy to clean. The high-temperature pyrolysis method has good particle uniformity and easy control of particle size, but it needs to precisely control the temperature, use a large amount of surfactants, and the surface of the particles is easy to absorb a large amount of organic reagents and is difficult to clean. Such as the Chinese invention patent (application publication number: CN102085381A).

Due to their small size, nanoparticles have high specific surface area and high surface activity, and are easy to accumulate in cells and tissues, and interact with biological components to produce toxicity. The biological toxicity of magnetic nanoparticles is related to its chemical composition, particle size, shape, surface modification substances, structure, aggregation and other factors. The surface modification of particles can reduce the surface energy of nanoparticles, reduce agglomeration, and adjust the biocompatibility and reaction characteristics of magnetic nanoparticles.

SiO ₂ has good biocompatibility and anti-decomposition and anti-oxidation capabilities. After the surface of Fe ₃ O ₄ nanoparticles is coated with SiO ₂ layer, the mutual attraction between particles can be well suppressed, and the water solubility, stability and biocompatibility of Fe ₃ O ₄ nanoparticles can be improved, and the surface of SiO ₂ There are abundant carboxyl groups, which make SiO ₂ /Fe ₃ O ₄ magnetic composite particles easier to modify or connect with functional polymer materials, which is beneficial to its application in biomedicine and other fields. In the method of modifying the surface of the silica-coated iron ferric oxide core-shell structure with mercapto groups, the Chinese invention patent (application publication number: CN103599751A) uses a silane coupling agent to functionalize the surface of the carrier. The Chinese invention patent (application publication number: CN104174039A) adopts the covalent interaction to introduce near-infrared functional groups and polyethylene glycol mercapto functional groups. The reaction temperature of the two in the modification process is above 60 ° C. The former needs to continuously feed nitrogen gas during the reaction process, and the solvent methanol is very volatile after heating and has a toxic effect on the human body; It is necessary to modify the surface of nanoparticles with amino groups, and the process steps are too cumbersome.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a preparation method of mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles.

In order to solve the problems of the technologies described above, the technical solution proposed by the present invention is:

A preparation method of mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles, comprising the following steps:

(1) Preparation of magnetic iron ferric oxide particles by solvothermal method with ferric salt as raw material;

(2) Using tetraethyl orthosilicate as a silicon source, the silicon dioxide generated is coated on the surface of the magnetic ferric oxide particles by a sol-gel method to form ferric oxide/silicon dioxide magnetic nanoparticles ;

(3) Place the ferric oxide/silicon dioxide magnetic nanoparticles in the toluene solution, and disperse uniformly to obtain solution A; add dimercaptosuccinic acid to the dimethyl sulfoxide solution, and disperse uniformly to obtain solution B and then mixing and stirring the solution A and the solution B for a period of time, then separating the solid from the liquid, washing and drying the obtained solid, and obtaining the mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles.

In the above preparation method, preferably, in the step (3), the mass ratio of ferric oxide/silicon dioxide magnetic nanoparticles to dimercaptosuccinic acid is 1:1˜1:5.

In the above-mentioned preparation method, preferably, in the step (3), the solid-to-liquid ratio of ferric oxide/silicon dioxide magnetic nanoparticles to the toluene solution is 5:1 to 10:1, and the solid-to-liquid ratio unit correspondence is g/L; the volume ratio of toluene solution to dimethyl sulfoxide solution is 1:2～2:1.

In the above preparation method, preferably, in the step (3), the reaction time is 12-24 hours.

In the above-mentioned preparation method, preferably, in the step (1), the specific preparation process of the magnetic ferric ferric oxide particles is as follows: disperse the ferric iron salt in the ethylene glycol solution, add a dispersant, and after the dispersion is uniform, add Anhydrous sodium acetate, continue to disperse to obtain a uniformly dispersed mixed solution, transfer the mixed solution to a high-pressure reactor, control the reaction temperature at 200°C for a period of time, and obtain magnetic ferric iron tetroxide particles with narrow particle size distribution and good dispersibility .

In the above preparation method, preferably, the dispersant is selected as polyethylene glycol 2000, the average particle diameter of the magnetic iron ferric oxide particles is 150nm-300nm, and the surface functional groups are mainly -OH.

The above-mentioned preparation method, preferably, in the step (2), the specific preparation process of ferric oxide/silicon dioxide magnetic nanoparticles is as follows: adding magnetic ferric oxide particles to ethanol and dispersing evenly; then adding ammonia water Continue to disperse with water for a period of time; then add ethyl orthosilicate, stir gently for 6 to 12 hours, and finally separate by magnetic separation, and the obtained solids are washed alternately with alcohol and water for several times and dried to obtain iron tetraoxide coated on the surface. Core-shell structured magnetic nanoparticles coated with a silica layer.

In the above preparation method, preferably, the liquid-solid ratio of the magnetic ferric ferric oxide and the solvent is 1:2 to 1:1, and the solvent refers to ethanol, ammonia and water; the magnetic ferric ferric oxide and orthosilicate The solid-to-liquid ratio of ethyl ester is 62.5:1 to 165:1, and the solid-to-liquid ratio unit corresponds to g/L.

In the above preparation method, preferably, the volume ratio of ethanol, ammonia water, and water is 75:23.5:1.5.

In the above preparation method, preferably, the average thickness of the silicon dioxide layer is 20-90 nm.

The present invention is based on the fact that _SiO2 can reduce the surface energy of nanoparticles, reduce agglomeration, and there are abundant carboxyl groups on the surface of _SiO2 , so that dimercaptosuccinic acid with two mercapto groups can more easily coat Fe on _SiO2 The surface of the ₃ O ₄ magnetic composite particles is functionally modified, thereby improving the dispersion, stability and biocompatibility of the ferroferric oxide/silicon dioxide magnetic nanoparticles to a greater extent, so that it can be used in the biomedical field be more widely used.

Compared with the prior art, the present invention has the advantages of:

1) The reaction conditions in the preparation method of the present invention are mild, the preparation process reagents are non-toxic, the operation process is simple, the prepared magnetic nanoparticles have good dispersion performance, good stability and biocompatibility, and have potential in the field of biomedicine. application value.

2) In the preparation method of the present invention, dimercaptosuccinic acid (DMSA) is used for modification. DMSA itself is exactly a kind of heavy metal antidote, and has excellent biocompatibility. Its molecular formula is HOOC(CHSH) ₂ COOH, and DMSA passes COO Functional groups are bound to the surface of ferroferric oxide/silica magnetic nanoparticles, and there are two molecular weight mercapto groups exposed on the surface per molecular weight of DMSA. The rich mercapto functional groups greatly improve the dispersion and biocompatibility of the particles. function, and can provide abundant binding sites for potential applications such as protein binding, increasing its potential application value.

Description of drawings

FIG. 1 is a transmission electron microscope image of ferric oxide/silicon dioxide magnetic nanoparticles in Example 1 of the present invention.

Fig. 2 is a relative distribution diagram of the thickness of the silica coating layer of the ferric oxide/silicon dioxide magnetic nanoparticles in Example 1 of the present invention.

Fig. 3 is a transmission electron microscopy image of ferric oxide/silicon dioxide magnetic nanoparticles in Example 2 of the present invention.

Fig. 4 is a relative distribution diagram of the thickness of the silica coating layer of the ferric oxide/silicon dioxide magnetic nanoparticles in Example 2 of the present invention.

Fig. 5 is a particle size distribution diagram of the magnetic ferric iron tetroxide prepared in Example 3 of the present invention.

Fig. 6 is a transmission electron microscopy image of ferric oxide/silicon dioxide magnetic nanoparticles in Example 3 of the present invention.

Fig. 7 is a relative distribution diagram of the thickness of the silica coating layer of the ferric oxide/silicon dioxide magnetic nanoparticles in Example 3 of the present invention.

Fig. 8 is a Fourier transform infrared detection spectrum of ferric oxide magnetic particles (a) and mercapto-modified ferric oxide/silicon dioxide (b) magnetic nanoparticles in Example 3 of the present invention.

Fig. 9 is a VSM detection diagram of ferric ferric oxide magnetic particles (a) and mercapto-modified ferric ferric oxide/silicon dioxide (b) magnetic nanoparticles in Example 3 of the present invention.

Fig. 10 is a hemolysis experiment-hemolysis rate diagram of ferric iron tetroxide magnetic particles and mercapto-modified ferric ferric oxide/silicon dioxide magnetic nanoparticles in Example 3 of the present invention.

Fig. 11 is a diagram of the relative cell proliferation rate obtained from the cytotoxicity test MTT of different concentrations of ferric ferric oxide magnetic particles and mercapto-modified ferric ferric oxide/silicon dioxide magnetic nanoparticles in Example 3 of the present invention.

Fig. 12 is a diagram of the relative proliferation rate of cells obtained from the cytotoxicity test MTT of the ferric oxide magnetic particles and the sulfhydryl-modified ferric oxide/silicon dioxide magnetic nanoparticles in Example 3 of the present invention at different culture times.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully and in detail below in conjunction with the accompanying drawings and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The terminology used herein is only for the purpose of describing specific embodiments, and is not intended to limit the protection scope of the present invention.

Unless otherwise specified, the various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

Example 1:

A method for preparing the mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles of the present invention comprises the following steps:

(1) Take 1mmol of FeCl ₃ 6H ₂ O in a beaker, then add 30ml of ethylene glycol, 2g of polyethylene glycol 2000, magnetically stir until uniformly dispersed, then continue to add 3g of anhydrous sodium acetate, stir to obtain a uniformly dispersed mixture. Then add the mixed solution into the autoclave, raise the temperature to 200°C and react for 6 hours, after the reaction is completed, water cool to room temperature, magnetically separate, wash the solid matter obtained after separation with alcohol several times, and then put it in a 60°C drying oven under vacuum Dry to obtain magnetic ferric oxide particles.

(2) Disperse 50 mg of the magnetic ferric iron tetroxide particles prepared in step (1) in 75 mL of ethanol solution, sonicate for 40 min, continue to add 23.5 mL of deionized water and 1.5 mL of ammonia (25 wt %), and sonicate for 40 min. Then the mixed solution was electrically stirred, and at the same time, 0.4 mL of ethyl orthosilicate was slowly added (the solid-to-liquid ratio of the mass of magnetic iron ferric oxide particles to ethyl orthosilicate was 125 g: 1 L), and the gentle stirring was continued for 8 hours. After the reaction, magnetically separate, wash with alcohol and water alternately for several times, and vacuum-dry at 60° C. to obtain magnetic nanoparticles with a silicon dioxide-coated ferric oxide structure (ferric oxide/silicon dioxide).

(3) Disperse 100 mg of ferric oxide/silicon dioxide magnetic nanoparticles prepared in step (2) in 20 mL of toluene solution, and sonicate for 30 min to obtain solution A. Take 250 mg of dimercaptosuccinic acid and disperse it in 10 mL of dimethyl sulfoxide solution, sonicate for 30 minutes to obtain solution B; mix and stir solution A and solution B for 24 hours, after the reaction is completed, wash with alcohol several times, and vacuum and drying to obtain mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles.

The iron ferric oxide/silicon dioxide magnetic nanoparticles obtained in step (2) of this embodiment were uniformly dispersed in ethanol, and then detected by a transmission electron microscope. The TEM results are shown in Figure 1, where a indicates that the magnification scale is 500nm; b indicates that the magnification scale is 200nm; c indicates that the magnification scale is 100nm. Statistical analysis was performed on no less than 200 particles using nanomeasurer (particle size analysis) software. The thickness distribution of the SiO ₂ coating layer is shown in Figure 2, with an average thickness of about 32.5nm.

Example 2:

A method for preparing the mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles of the present invention comprises the following steps:

(1) Take 1mmol of FeCl ₃ 6H ₂ O in a beaker, then add 30ml of ethylene glycol, 2g of polyethylene glycol 2000, magnetically stir until uniformly dispersed, then continue to add 3g of anhydrous sodium acetate, stir to obtain a uniformly dispersed mixture. Then add the mixed solution into the autoclave, raise the temperature to 200°C and react for 6 hours, after the reaction is completed, water cool to room temperature, magnetically separate, wash the solid matter obtained after separation with alcohol several times, and then put it in a 60°C drying oven under vacuum Dry to obtain magnetic ferric oxide particles.

(2) Disperse 50 mg of the magnetic ferric iron tetroxide particles prepared in step (1) in 150 mL of ethanol solution, sonicate for 40 min, then add 47 mL of deionized water and 3 mL of ammonia water (25 wt %), and sonicate for 40 min. Then the mixed solution was electrically stirred, and at the same time, 0.8 mL of ethyl orthosilicate was slowly added (the solid-to-liquid ratio of the mass of magnetic iron ferric oxide particles to ethyl orthosilicate was 62.5 g: 1 L), and the gentle stirring was continued for 12 hours. After the reaction, magnetically separate, wash with alcohol and water alternately for several times, and vacuum-dry at 60° C. to obtain magnetic nanoparticles with a silicon dioxide-coated ferric oxide structure (ferric oxide/silicon dioxide).

(3) Disperse 100 mg of ferric oxide/silicon dioxide magnetic nanoparticles prepared in step (2) in 10 mL of toluene solution, and sonicate for 30 min to obtain solution A. Take 250 mg of dimercaptosuccinic acid and disperse it in 20 mL of dimethyl sulfoxide solution, sonicate for 30 minutes to obtain solution B; mix and stir solution A and solution B for 18 hours, after the reaction is completed, wash with alcohol for several times, and vacuum and drying to obtain mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles.

The iron ferric oxide/silicon dioxide magnetic nanoparticles obtained in step (2) of this embodiment were uniformly dispersed in ethanol, and then detected by transmission electron microscopy. The TEM results are shown in Figure 3, where a indicates that the magnification scale is 500nm; b indicates the magnification scale bar is 200nm. Statistical analysis was performed on no less than 200 particles using nanomeasurer (particle size analysis) software. The thickness distribution of the SiO ₂ coating layer is shown in Figure 4, with an average thickness of about 87nm.

Example 3:

A method for preparing the mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles of the present invention comprises the following steps:

(1) Take 1mmol of FeCl ₃ 6H ₂ O in a beaker, then add 30ml of ethylene glycol, 2g of polyethylene glycol 2000, magnetically stir until uniformly dispersed, then continue to add 3g of anhydrous sodium acetate, stir to obtain a uniformly dispersed mixture. Then add the mixed solution into the autoclave, raise the temperature to 200°C and react for 6 hours, after the reaction is completed, water cool to room temperature, magnetically separate, wash the solid matter obtained after separation with alcohol several times, and then put it in a 60°C drying oven under vacuum Dry to obtain magnetic ferric oxide particles. The particle size distribution diagram is shown in Figure 5, and the average particle size is 157nm.

(2) Disperse 50 mg of the magnetic ferric iron tetroxide particles prepared in step (1) in 150 mL of ethanol solution, sonicate for 40 min, then add 47 mL of deionized water and 3 mL of ammonia water (25 wt %), and sonicate for 40 min. Then, the mixed solution was electrically stirred, and at the same time, 0.3 mL of ethyl orthosilicate was slowly added (the solid-to-liquid ratio of the mass of magnetic iron ferric oxide particles to ethyl orthosilicate was 165 g: 1 L), and the gentle stirring was continued for 6 hours. After the reaction, magnetically separate, wash with alcohol and water alternately for several times, and vacuum-dry at 60° C. to obtain magnetic nanoparticles with a silicon dioxide-coated ferric oxide structure (ferric oxide/silicon dioxide).

(3) Disperse 100 mg of ferric oxide/silicon dioxide magnetic nanoparticles prepared in step (2) in 10 mL of toluene solution, and sonicate for 30 min to obtain solution A. Take 250 mg of dimercaptosuccinic acid and disperse it in 10 mL of dimethyl sulfoxide solution, sonicate for 30 minutes to obtain solution B; mix and stir solutions A and B for 12 hours, after the reaction is completed, wash with alcohol for several times, and dry under vacuum at 60°C , to obtain mercapto-modified ferric oxide/silica magnetic nanoparticles.

The iron ferric oxide/silicon dioxide magnetic nanoparticles obtained in step (2) of this embodiment were uniformly dispersed in ethanol, and then detected by a transmission electron microscope. The TEM results are shown in Figure 6, where a indicates that the magnification scale is 1000nm; b indicates the magnification scale bar is 100nm. Statistical analysis was performed on no less than 200 particles using nanomeasurer (particle size analysis) software. The thickness distribution of the SiO2 coating layer is shown in Figure 7, with an average thickness of about 17nm.

The mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles prepared in this implementation were analyzed by Fourier transform infrared spectroscopy, and the results are shown in Figure 8. The results showed that silicon dioxide was successfully coated on the surface of ferric oxide , and dimercaptosuccinic acid modified ferric oxide/silica nanoparticles successfully. In the curve, around 575.62cm ^-1 is the characteristic absorption peak of Fe-O vibration in Fe ₃ O ₄ , 460cm ^-1 is the vibration peak of O-Si-O group, and the absorption peak at 1091.11cm ^-1 corresponds to Si The antisymmetric stretching vibration of -O ^- Si, the absorption peak at 929 cm is caused by the Si-OH stretching vibration, indicating the existence of the silica layer. The vibrational absorption peak of -SH is weak and overlaps with the _CO2 vibrational peak in the background atmosphere, so there is no obvious characteristic peak in the curve.

The magnetic iron ferric oxide particles prepared in this example and the mercapto-modified iron ferric oxide/silicon dioxide magnetic nanoparticles were subjected to VSM detection, and the detection results were shown in Figure 9. The saturation magnetization of the magnetic ferric oxide particles was 156.04emu/g, the saturation magnetization was weakened to 125.98emu/g after coating the silicon dioxide layer and DMSA modification.

The magnetic ferric oxide particles prepared in steps (1) and (3) of this example and the mercapto-modified ferric oxide/silica magnetic nanoparticles were prepared into different concentration solutions (0.0625 mg/ml, 0.0625 mg/ml, 0.25mg/ml, 1mg/ml, 3mg/ml, 5mg/ml, 7mg/ml), all sample tubes were bathed in water at 37°C for 72h; distilled water was used as positive control, and normal saline was used as negative control; 1ml of the above-mentioned different Add 25uL diluted anticoagulated whole blood, shake in an air bath at 37°C for 150min, centrifuge at 10g/min for 5min, take the supernatant and measure the absorbance at a wavelength of 540, and repeat the experiment with 3 samples in each group. The results are shown in FIG. 10 , the mercapto-modified ferric oxide/silica magnetic nanoparticles have good hemocompatibility, even at a high concentration of 7 mg/ml, the hemolysis rate is less than 5%, about 3%. The hemolysis rate of ferric oxide magnetic nanoparticles is higher than that of thiol-modified ferric oxide/silicon dioxide magnetic nanoparticles. When the concentration is 7mg/ml, the hemolysis rate is greater than 20%, far exceeding 5%.

A single cell suspension was prepared with a culture solution containing 10% fetal bovine serum, and seeded into a 96-well plate with 5×10 ³ cells per well, with a volume of 100 uL per well. After culturing for 24 hours, discard 50uL of the stock solution, add 50uL of different concentrations of the magnetic ferric oxide particles prepared in steps (1) and (3) of this example, and sulfhydryl-modified ferric oxide/silicon dioxide magnetic nanoparticles, The final concentration was 1 mg/ml, 0.25 mg/ml, 0.0625 mg/ml, 0.0156 mg/ml. The negative group is culture medium, and the positive group is dimethyl sulfoxide. They were cultured in an air incubator at 37°C and 5% (V/V) CO ₂ for 24, 36, 48, 60, and 72 hours, respectively. After the culture was completed, 20 uL of thiazolium blue (MTT) solution (5 mg/ml in phosphate buffered saline (PBS)) was added to each well. Continue to incubate for 4 hours, terminate the culture, turn the plate over and discard the culture supernatant in the well. Add 150uL dimethyl sulfoxide to each well and shake for 10 minutes to fully dissolve the crystals. Select a wavelength of 490nm, measure the light absorption value of each well on an enzyme-linked immunosorbent monitor, repeat the experiment, and record the results. Figure 11 and Figure 12 show the graphs of the relative proliferation rate of cells obtained from the cytotoxicity test MTT. It can be seen from Figure 11 that with the increase of the concentration of nanoparticles, the relative proliferation rate of mouse fibroblast L-929 cells decreased, and the sulfhydryl-modified ferroferric oxide/silica magnetic nanoparticles The cytotoxicity is small, when the nanoparticle concentration is less than 1 mg/ml, the relative cell proliferation rate is greater than 75%, and the cytotoxicity grade is grade 1, which is regarded as no cytotoxicity. It can be seen from Figure 12 that with the increase of culture time, the relative cell proliferation rate decreased, and the sulfhydryl-modified ferroferric oxide/silica magnetic nanoparticles were less cytotoxic than the ferroferric oxide magnetic nanoparticles, and the culture time was less than At 60 hours, the relative proliferation rate of the cells was greater than 75%, and the cytotoxicity grade was grade 1, which was regarded as no cytotoxicity.

Claims (10)

1. a preparation method of mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles, is characterized in that, comprises the following steps: (1) Preparation of magnetic iron ferric oxide particles by solvothermal method with ferric salt as raw material; (2) Using tetraethyl orthosilicate as a silicon source, the silicon dioxide generated is coated on the surface of the magnetic ferric oxide particles by a sol-gel method to form ferric oxide/silicon dioxide magnetic nanoparticles ; (3) Place the ferric oxide/silicon dioxide magnetic nanoparticles in the toluene solution, and disperse uniformly to obtain solution A; add dimercaptosuccinic acid to the dimethyl sulfoxide solution, and disperse uniformly to obtain solution B and then mixing and stirring the solution A and the solution B for a period of time, then separating the solid from the liquid, washing and drying the obtained solid, and obtaining the mercapto-modified ferric oxide/silicon dioxide magnetic nanoparticles. 2. preparation method as claimed in claim 1, is characterized in that, in described step (3), the mass ratio of ferric oxide/silicon dioxide magnetic nanoparticles and dimercaptosuccinic acid is 1:1～1 :5. 3. the preparation method as claimed in claim 1, is characterized in that, in described step (3), the solid-liquid ratio of ferric oxide/silicon dioxide magnetic nanoparticles and toluene solution is 5:1～10:1 , the solid-liquid ratio unit is g/L; the volume ratio of toluene solution to dimethyl sulfoxide solution is: 1:2～2:1. 4. The preparation method according to claim 1, characterized in that, in the step (3), the reaction time is 12-24 hours. 5. The preparation method according to any one of claims 1 to 4, characterized in that, in the step (1), the specific preparation process of the magnetic iron ferric oxide particles is: dispersing the ferric salt in ethylene dioxide In the alcohol solution, after adding a dispersant to disperse evenly, add anhydrous sodium acetate, continue to disperse to obtain a uniformly dispersed mixed solution, transfer the mixed solution to a high-pressure reactor, control the reaction temperature at 200°C for a period of time, and obtain a particle size distribution Narrow, good dispersion of magnetic ferric oxide particles. 6 . The preparation method according to claim 5 , wherein the dispersant is polyethylene glycol 2000, and the average particle diameter of the magnetic iron ferric oxide particles is 150 nm to 300 nm. 7. The preparation method according to any one of claims 1 to 4, characterized in that, in the step (2), the specific preparation process of ferric oxide/silicon dioxide magnetic nanoparticles is: Add triiron particles into ethanol to disperse evenly; then add ammonia water and water and continue to disperse for a period of time; then add tetraethyl orthosilicate, stir gently for 6-12 hours, and finally separate by magnetic separation, and the obtained solids are washed alternately with alcohol and water After several times of drying, the core-shell structure magnetic nanoparticles whose surface is coated with silicon dioxide layer are obtained. 8. preparation method as claimed in claim 7, is characterized in that, the liquid-solid ratio of described magnetic ferric ferric oxide and solvent is 1:2～1:1, and described solvent refers to ethanol, ammoniacal liquor and water; Magnetic The solid-to-liquid ratio of ferric oxide to tetraethyl orthosilicate is 62.5:1 to 165:1, and the solid-to-liquid ratio unit is g/L. 9. preparation method as claimed in claim 7, is characterized in that, described ethanol, ammoniacal liquor, water volume ratio are 75:23.5:1.5. 10. The preparation method according to claim 7, characterized in that the average thickness of the silicon dioxide layer is 20-90 nm.