Method for preparing double-sided structure micro-nano motor based on Pickering emulsion

Abstract

The invention discloses a method for preparing a double-sided structured micro-nano motor based on Pickering emulsion, and belongs to the technical field of nano device preparation, and the method comprises the following steps: preparing a paraffin-nano particle semi-surface structure by using Pickering emulsion; after selective modification is conducted on the surfaces of the exposed nano particles in the paraffin-nano particle semi-face structure, paraffin is removed, and eccentric nano particles are obtained; the invention discloses a micro-nano motor with a double-sided structure prepared on the basis of eccentric nanoparticles. The Pickering emulsion is creatively used for preparing the micro-nano motor of the double-sided structure, the method has the advantages of being simple, efficient, independent of equipment and the like, large-scale preparation of the micro-nano motor can be achieved, and industrial application of the micro-nano motor can be promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-device preparation, and particularly relates to a method for preparing Janus-structured micro-nano motors based on Pickering emulsions. Background Art

[0002] Micro-nano motors are nano-devices that can convert other forms of energy into kinetic energy and move autonomously at the micro-nano scale. Janus-structured micro-nano motors, due to their asymmetric structures, can achieve efficient energy conversion at the micro-nano scale and have diverse motion mechanisms. They can move flexibly in different environments, adapt to various application scenarios, and show broad application prospects in the field of biomedicine.

[0003] Currently, most methods for preparing Janus-structured micro-nano motors use physical vapor deposition. Although physical vapor deposition is widely used, it is difficult to prepare small-sized motor micro-nano motors. The preparation process relies on expensive and complex equipment, and the production efficiency is very limited. The complexity and tediousness of the preparation process of Janus micro-nano motors limit their large-scale practical applications. Summary of the Invention

[0004] In view of the technical problems in the background art, the present invention provides a method for preparing Janus-structured micro-nano motors based on Pickering emulsions, aiming to solve the problems of complexity and tediousness in the preparation process of Janus micro-nano motors, and this method is very suitable for the preparation of small-sized motors.

[0005] The technical solution of the present invention is as follows: A method for preparing Janus-structured micro-nano motors based on Pickering emulsions, comprising the following steps: S1. Add paraffin to an aqueous solution dispersed with nanoparticles, and stir to form a Pickering emulsion containing a paraffin-nanoparticle half-plane structure; S2. After selectively modifying the surface of the exposed nanoparticles in the paraffin-nanoparticle half-plane structure, remove the paraffin in the product and collect the eccentric nanoparticles; S3. Prepare Janus-structured micro-nano motors based on the eccentric nanoparticles.

[0006] Preferably, in the above preparation method, a surfactant is added to the aqueous solution in step S1, and the surfactant is at least one of SDS, CTAB, CTAC, sodium dodecylbenzenesulfonate, sodium dodecylaminopropionate, and glycerol monostearate. In this reaction system, the hydrophobic chain segments of the surfactant face the oil phase, and the hydrophilic groups face the water phase, thereby reducing the surface tension at the oil-water interface, and further improving the stability and formation efficiency of the Pickering emulsion.

[0007] More preferably, the concentration of the above surfactant is 0.01 - 0.1 mg / mL. When the surfactant concentration is too high, a large number of molecules will adsorb on the surface of Pickering particles, completely covering the particle surface, resulting in the interaction between particles changing from a state of stable adsorption at the interface to mutual repulsion. The particles are over-dispersed in the solution and it is difficult to aggregate at the oil-water interface and form a close arrangement structure, so a stable Pickering emulsion cannot be formed. When the surfactant concentration is too low, the interfacial tension cannot be effectively reduced, resulting in a large interfacial energy between the oil phase and the water phase. The oil droplets or water droplets tend to coalesce to reduce the total interfacial area and lower the energy of the system, and it is also difficult to form a stable Pickering emulsion.

[0008] Preferably, in the above preparation method, ethanol and / or methanol are added to the aqueous solution in step S1. The present invention uses ethanol and methanol to adjust the surface wettability of Pickering particles, making it easier for the particles to adsorb at the oil-water interface; in addition, ethanol and methanol can also reduce the interfacial tension between the oil and water to a certain extent, making it easier to form emulsion droplets with smaller particle sizes, thereby improving the stability and uniformity of the Pickering emulsion. More preferably, the volume ratio of water to ethanol / methanol is (20 - 5):1.

[0009] Preferably, in the above preparation method, the stirring speed in step S1 is not less than 1000 r / min. Too slow stirring speed will cause problems such as insufficient dispersion of emulsion droplets, uneven particle sizes of emulsion droplets, and poor emulsion stability. Moreover, experimental data show that increasing the stirring speed has no obvious effect on the preparation of the half-plane structure above this threshold.

[0010] Preferably, in the above preparation method, the reaction temperature in step S1 is 50 - 100 °C.

[0011] Preferably, in the above preparation method, the mass ratio of nanoparticles to paraffin is 1:(15 - 150).

[0012] Preferably, in the above preparation method, the nanoparticles are elemental, oxide or sulfide nanoparticles of gold, silver, palladium, platinum, manganese, iron, cerium, titanium, aluminum or zinc, or inorganic non-metallic nanoparticles, or organic nanoparticles; the nanoparticles can be hollow, solid or porous structures. For example, in some embodiments of the present invention, the nanoparticles are spherical mesoporous silica nanoparticles.

[0013] Preferably, in the above preparation method, the size of the nanoparticles is 10 - 500 nm. Since the method of the present invention utilizes nanoparticles to form Pickering emulsions, it is more suitable for the preparation of small-sized nano-motors; experimental data show that when the size of the nanoparticles is less than 500 nm, the effect is better. When the particle size is too large, the specific surface area is relatively small, and it may be difficult to form a tight and continuous coverage on the interface, resulting in more defects and voids in the interfacial film. The oil phase and water phase between the emulsion droplets can easily contact each other through these voids, and then coalescence occurs, reducing the stability of the Pickering emulsion.

[0014] Preferably, in the above preparation method, the method for removing paraffin in step S2 is: placing the product in an organic solvent to dissolve and remove paraffin, and the organic solvent is at least one of chloroform, n-hexane, toluene, dichloromethane, acetone, and ethyl acetate. Utilizing the characteristic that paraffin is soluble in certain organic solvents, paraffin in the paraffin-nanoparticle half-plane structure can be removed without affecting the previous modification, thereby releasing the nanoparticles. At this time, the surface of the obtained nanoparticles has an asymmetric modification structure, that is, eccentric nanoparticles.

[0015] Preferably, in the above preparation method, in step S2, selective modification is carried out by covalent coupling using the functional groups on the surface of the nanoparticles. For example, in some embodiments of the present invention, the nanoparticles are surface-aminated mesoporous silica (MSNs). By using the reaction between the amino group and the aldehyde group of glutaraldehyde, selective modification of the surface of the exposed MSNs in the paraffin-MSNs half-plane structure is achieved; in addition, selective modification of the surface of the exposed MSNs can also be carried out by using the coupling reaction between the amino group and a biotinylated reagent (such as N-succinimidyl 6-biotinamidohexanoic acid).

[0016] More preferably, in the above preparation method, step S3 includes the following operations: S31. Connecting a functional molecule on the surface of the eccentric nanoparticles newly exposed after paraffin removal; S32. Modifying an enzyme on the nanoparticles based on the functional molecule by using a covalent coupling method; wherein, the enzyme includes but is not limited to urease, catalase, glucose peroxidase, arginase, lipoprotein lipase, lipase, galactosidase, transaminase, decarboxylase, carbonic anhydrase, etc. Specifically, different enzymes can be selected according to the application scenario of the motor; the covalent coupling methods include metal-thiol reaction, amide reaction, nucleophilic addition reaction, Schiff base synthesis reaction, etc.

[0017] The micro-nano motors prepared according to the method of the present invention also belong to the protection scope of the present invention.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The present invention innovatively uses the Pickering emulsion method to prepare Janus nanomotors. Compared with the conventional physical vapor deposition method, the method of the present invention is simple, efficient, independent of equipment, and is particularly suitable for the preparation of small-sized motors.

[0019] The method of the present invention can replace the types of nanoparticles, functional molecules, and bioenzymes according to needs, and can flexibly construct a variety of Janus nanomotors to meet different actual needs, with extremely high plasticity. Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solution of the present invention, the drawings used in the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a flow chart for preparing mesoporous silica nanomotors based on Pickering emulsion in the embodiment of the present invention; Figure 2 It is a scanning electron microscope image of the mesoporous silica nanomotors prepared in the embodiment of the present invention; Figure 3 It is a graph of the detection results of the motility of the mesoporous silica nanomotors prepared in the embodiment of the present invention at different urea concentrations; Figure 4 It is a morphological comparison of the paraffin-nanoparticle half structure formed in the Pickering emulsion of the embodiment of the present invention and the comparative example. Detailed Embodiments

[0022] The embodiments of the technical solution of the present invention will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The terms "including" and "having" and any variations thereof in this article are intended to cover non-exclusive inclusion.

[0024] To solve the problems of preparing Janus-structured micro-nano motors in the prior art, the present invention proposes a method for simply and efficiently preparing Janus-structured micro-nano motors based on Pickering emulsions. Pickering emulsions are emulsions formed by stabilizing the water-oil interface with colloidal-sized solid particles, and the formation principle of Pickering emulsions is based on the adsorption of solid particles at the oil-water interface. The method of the present invention greatly improves the flexibility and simplicity of preparing Janus-structured micro-nano motors, thereby expanding the application potential of nano-motors in drug delivery, biosensing and other aspects.

[0025] The following are some specific examples. It should be noted that the examples described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. For those not specified in the examples regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0026] Example 1 In this example, taking mesoporous silica nanoparticles (MSNs) as an example, a method for preparing mesoporous silica nano-motors based on Pickering emulsions is provided, as Figure 1 shown, including the following steps: ① Add paraffin to the aqueous solution in which amino-functionalized MSNs are dispersed, and stir to obtain a paraffin-MSNs half-plane structure; ② Under the action of N-hydroxysuccinimide (NHS) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC), use methoxy-polyethylene glycol-carboxyl (COOH-PEG-CH 3 O) to selectively modify the surface of the exposed MSNs in the paraffin-MSNs half-plane structure; ③ Place the product obtained after modification in an organic solvent to dissolve and remove paraffin, and collect the obtained eccentric nanoparticles; ④ React the amino groups on the surface of the eccentric nanoparticles with glutaraldehyde; ⑤ Connect biocatalysts to the eccentric nanoparticles based on glutaraldehyde to obtain mesoporous silica nano-motors.

[0027] In step ①, in order to more easily generate a stable Pickering solution and improve the synthesis efficiency, a suitable surfactant and ethanol / methanol can be further added to the aqueous solution. By controlling parameters such as the surfactant, ethanol / methanol, and high-speed stirring, the mesoporous silica nanoparticles tend to adsorb at the oil-water interface, thereby forming a stable Pickering emulsion with one end immersed in the aqueous phase and the other end embedded in paraffin. In view of the fact that one side of the mesoporous silica nanoparticles is embedded in paraffin, the biotinylation reagent can only react with the amino groups exposed on the outside of the mesoporous silica nanoparticles, thereby realizing the asymmetric modification of the mesoporous silica nanoparticles.

[0028] In the method of this example, those skilled in the art can select different bioenzymes according to the application scenarios of the motor, such as urease, catalase, glucose oxidase, etc. The motor prepared according to the method of this example has mesoporous silica as the main body, and polyethylene glycol and bioenzymes are respectively connected to both sides to form a Janus structure; active substances (such as organic small molecules, biological macromolecules, etc.) can be loaded into the pores of silica, and then drug delivery, biosensing, etc. can be achieved by means of the movement of the motor.

[0029] Example 2 Based on the method in Example 1, a mesoporous silica nanomotor with a Janus structure was prepared in this example. The specific operations are as follows: (1) Preparation of the paraffin-MSNs half-plane structure.

[0030] Add 10 mL of deionized water, 0.21 mg of SDS, and 0.75 mL of absolute ethanol into a colorimetric tube, then add 20 mg of 100 nm MSNs and disperse them by ultrasonic treatment. Add 0.5 g of paraffin, stir at 1000 r / min at 80 °C for 1 h, put it in a -20 °C environment for rapid cooling, and then collect the product (i.e., paraffin-MSNs).

[0031] (2) Preparation of eccentric nanoparticles.

[0032] Mix 0.186 mg of NHS and 0.153 mg of EDC with 2 mg of COOH-PEG-CH 3 O, react in 1 mL of PB solution (10 mM, pH = 7.4) for 0.5 h, add the obtained solution to 1 mL of paraffin-MSNs aqueous solution (the solvent is PB buffer, 10 mM, pH = 7.4), and shake and react at room temperature for 8 h. Take out the upper emulsion, dissolve it with 10 mL of chloroform solution, and centrifuge to collect the MSNs particles.

[0033] (3) Preparation of the Janus-structured micro-nano motor.

[0034] Take 1 mL of the obtained MSNs dispersion and add 1 mL of glutaraldehyde solution. After mixing, disperse it in PB solution (10 mM, pH = 7.4) and shake and react for 2 h. After the reaction is completed, add 2 mg of urease to the above solution and shake and react for 2 h, and then wash it three times with deionized water to obtain the mesoporous silica nanomotor.

[0035] The mesoporous silica nanomotor prepared in this example was characterized and detected, and the results are as follows: 1. Morphology analysis.

[0036] Figure 2Image of the nanomotor taken by a scanning electron microscope.

[0037] 2. Analysis of motility.

[0038] The mesoporous silica nanomotors were placed in 0, 2.5, 5, 7.5, 10, 15, 20, 50 mM urea solutions respectively to detect their motility. Figure 3 The mean square displacement (MSD) and diffusion coefficient of the nanomotor at different urea concentrations are shown. It can be seen that as the urea concentration increases, the moving distance of the nanomotor gradually increases, and the slope of the mean square displacement and the diffusion coefficient also gradually increase, and it can be effectively driven at the human urea concentration (~10 mM).

[0039] Example 3 Different from Example 2, in this example, SDS in step (1) was replaced with CTAB, and its concentration was 0.0175 mg / mL.

[0040] Comparative Example 1 Different from Example 2, in this example, SDS was not added in step (1). As shown in Figure 4 a, the Pickering emulsion MSNs formed without adding SDS overlapped with each other on the paraffin surface. Compared with the Pickering emulsion formed under all conditions ( Figure 4 d), the uniformity was very poor.

[0041] Comparative Example 2 Different from Example 2, in this example, the stirring speed in step (1) was lower than 1000 r / min. As shown in Figure 4 b, when the rotation speed was lower than 1000 r / min, compared with the Pickering emulsion formed under all conditions ( Figure 4 d), the shape of the paraffin was significantly irregular, and the number of MSNs growing on the paraffin surface was small and uneven.

[0042] Comparative Example 3 Different from Example 2, in this example, ethanol was not added in step (1). As shown in Figure 4 c, the Pickering emulsion MSNs formed without adding ethanol overlapped with each other on the paraffin surface. Compared with the Pickering emulsion formed under all conditions ( Figure 4 d), the uniformity was poor.

[0043] According to the above examples, those skilled in the art can replace MSNs with other nanoparticles, such as iron oxide, dopamine, manganese dioxide and other nanoparticles, and then adjust the reaction conditions to obtain various half-plane structures by using Pickering emulsions, and further construct Janus structure nanomotors with different carriers.

[0044] All the raw materials listed in the present invention, as well as the upper and lower limits and interval values of the raw materials of the present invention, and the upper and lower limits and interval values of process parameters (such as temperature, time, etc.) can achieve the present invention, and the embodiments are not listed one by one here.

[0045] In summary, the present invention successfully prepares Janus-structured micro-nano motors using Pickering emulsions. Compared with the existing preparation methods of micro-nano motors, the method of the present invention is simpler and more efficient, and large-scale preparation of micro-nano motors can be achieved.

[0046] It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same function and effect as the technical idea within the technical scope of the present invention are included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A method for preparing a Janus-structured micro-nano motor based on Pickering emulsion, characterized in that: The following steps are involved: S1, adding paraffin wax to the aqueous solution in which nanoparticles are dispersed, and stirring to form a Pickering emulsion containing a paraffin wax-nanoparticle half-face structure; S2, after selectively modifying the exposed nanoparticle surface in the paraffin-nanoparticle half-surface structure, removing the paraffin in the product and collecting the eccentric nanoparticles; S3. Preparation of Janus-structured micro-nanomotor based on eccentric nanoparticles.

2. The method according to claim 1, characterized in that A surfactant is added to the aqueous solution, and the surfactant is at least one of SDS, CTAB, CTAC, sodium dodecylbenzene sulfonate, sodium dodecylaminopropionate, and glyceryl monostearate.

3. The method according to claim 1, characterized in that At least one of ethanol and methanol is added to the aqueous solution.

4. The method according to claim 1, characterized in that: In step S1, the stirring speed is not less than 1000 r / min; the stirring temperature is 50-100°C.

5. The method according to claim 1, characterized in that The mass ratio of the nanoparticles to the paraffin is 1:(15-150).

6. The method according to claim 1, characterized in that The functional groups on the surface of the nanoparticles are selectively modified by covalent coupling.

7. The method according to claim 6, characterized in that Step S3 includes the following operations: S31, attaching functional molecules (organic molecules not involved in the catalytic reaction) on the surface of the eccentric nanoparticles that are exposed again after the paraffin is removed; S32. Modifying biological enzymes on nanoparticles by a covalent coupling method; wherein the biological enzymes include at least one of urease, catalase, glucose peroxidase, arginase, lipoprotein lipase, lipase, galactosidase, transaminase, decarboxylase, and carbonic anhydrase, and the covalent coupling method includes at least one of a metal-thiol reaction, an amide reaction, a nucleophilic addition reaction, and a Schiff base synthesis reaction.

8. The method according to claim 1, characterized in that The method for removing the paraffin in step S2 is: placing the product in an organic solvent to dissolve and remove the paraffin, and the organic solvent is at least one of chloroform, n-hexane, toluene, dichloromethane, acetone, and ethyl acetate.

9. The method according to claim 1, characterized in that: The nanoparticles include single substances, oxides or sulfide nanoparticles of gold, silver, palladium, platinum, manganese, iron, cerium, titanium, aluminum or zinc, inorganic non-metallic nanoparticles, and organic nanoparticles; the nanoparticles are hollow, solid or porous structures.

10. A Janus-structured micro-nano motor, characterized in that: Prepared according to the method according to any one of claims 1 to 9.

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