Binary organic-inorganic ordered capsule and preparation method thereof

Abstract

The invention discloses a preparation method of a binary organic-inorganic ordered capsule structure. The preparation method of the binary capsule structure comprises the following steps: firstly, synthesizing gold nanocubes and gold nanospheres by using a tetrachloroauric acid trihydrate solution; then, grafting polystyrene on the surfaces of the gold nanocubes and the gold nanospheres; and finally, preparing the binary organic-inorganic ordered capsule structure by adopting an emulsion interface limited assembly method. By adjusting the molecular weight of the polymers on the surfaces of the two inorganic nanoparticles, the spacing, arrangement and orientation of the two nanoparticles can be effectively regulated and controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic nanoparticle self-assembly, and specifically to a binary organic-inorganic ordered capsule and a preparation method thereof. Background Art

[0002] Binary nanoparticle superlattices are a class of long-range ordered structures with two-dimensional or three-dimensional spatial periodicity formed by the binary co-assembly of two different sizes, shapes or types of inorganic nanoparticles. On the one hand, this superstructure has many similarities with the long-range ordered array of atomic crystals and can be used as an intuitive model for studying the formation and evolution of crystal structures. On the other hand, due to the coupling and synergistic effects between different types of nanoparticles, the structure can be made more abundant and programmable, showing excellent properties that the building blocks do not possess.

[0003] In recent years, with the development of nanodiagnosis and treatment in the biomedical field, people have paid increasing attention to the construction and application of three-dimensional multifunctional organic / inorganic ordered capsules or vesicles. Ordered arrangement of functional nanoparticles on three-dimensional curved surfaces can obtain multifunctional organic-inorganic capsules that integrate bioimaging, photothermal therapy, drug loading and release. Compared with single-component capsule structures, binary capsule structures show higher application value in the fields of bioimaging, photothermal therapy, drug loading and release due to the characteristics of two inorganic nanoparticles and their coupling and synergistic effects.

[0004] The existing technical system still has the following key bottlenecks that need to be broken through urgently:

[0005] 1. The universality of the preparation method is limited: The current self-assembly strategy based on surface hydrophilic-hydrophobic regulation requires precise balancing of the surface energy parameters of nanoparticles, resulting in a very high sensitivity of the assembly process to the physical properties of the particles. It is difficult to achieve the universal preparation of different material systems, and it is easy to form metastable structures that affect the uniformity of the products.

[0006] 2. The research on the assembly mechanism is insufficient: There is a lack of systematic research on the assembly driving forces (such as entropy effect, electrostatic interaction, steric hindrance, etc.) of heterogeneous nanoparticles in a curved confined space and their influence laws on the spatial arrangement mode, which restricts the ability of structure design and performance regulation.

[0007] In view of this, aiming at the technical bottlenecks of the existing binary ordered capsule system, a universal assembly strategy has been innovatively developed, and an assembly mechanism model based on multi-physical field coupling has been proposed. By establishing a quantitative structure-activity relationship of nanoparticle surface modification-interface interaction-spatial arrangement mode, the controllable preparation of binary organic-inorganic ordered capsules with controllable structures has been successfully realized, providing a new paradigm for the construction of multifunctional nanodiagnosis and treatment platforms. Summary of the Invention

[0008] The technical problems to be solved by the present invention are the limited universality of the preparation method and the insufficient depth of research on the assembly mechanism.

[0009] The technical solution adopted by the present invention is as follows: A preparation method of a binary organic-inorganic ordered capsule structure, comprising the following steps:

[0010] (1) Synthesis of gold nanocubes and gold nanospheres:

[0011] a. Preparation of gold nanocubes: Mix an aqueous solution of cetyltrimethylammonium bromide (CTAB), an aqueous solution of ascorbic acid, and an aqueous solution of chloroauric acid trihydrate to form a growth solution, add a seed solution reduced by NaBH4, and react at a constant temperature of 27 - 30 °C for 12 - 24 hours;

[0012] b. Preparation of gold nanospheres: Under the condition of boiling reflux, add a sodium citrate solution to an aqueous solution of chloroauric acid trihydrate for a reduction reaction, and centrifuge and concentrate to obtain nanospheres with uniform particle size;

[0013] (2) Ligand modification on the surface of nanoparticles:

[0014] a. Mix a tetrahydrofuran solution of thiol-terminated polystyrene (PS-SH) with the aqueous solution of nanoparticles obtained in step (1), ultrasonically treat for 2 - 3 hours, and then let it stand for 24 hours;

[0015] b. Purify the grafted product by ethanol precipitation method, and remove free CTAB and unreacted PS-SH through 4 - 5 centrifugation-dispersion cycles to finally obtain PS-modified nanoparticles dispersed in chloroform;

[0016] (3) Confined assembly at the emulsion interface:

[0017] a. Dissolve the PS-modified gold nanocubes, gold nanospheres and n-hexadecane in chloroform according to a predetermined ratio to form a mixed organic phase;

[0018] b. Inject the mixed organic phase into an aqueous solution of polyvinyl alcohol (PVA) to form emulsion droplets, and control the slow evaporation of chloroform at room temperature for 3 days to obtain a binary ordered capsule structure.

[0019] As a further scheme of the present invention: In step (1)a, the side length of the gold nanocubes is 40 - 80 nm, and in step (1)b, the diameter of the gold nanospheres is 20 - 50 nm.

[0020] As a further scheme of the present invention: In step (2)a, the number average molecular weight of the thiol-terminated polystyrene is 5k - 30 kDa, and the grafting density is 1.2 - 2.5 chains / nm 2 .

[0021] As a further solution of the present invention: in step (3)a, the molar ratio of gold nanocubes to gold nanospheres is 1:5 to 5:1, and the addition amount of n-hexadecane is 10-30% of the total volume of the organic phase.

[0022] As a further solution of the present invention: in step (3)b, the concentration of the polyvinyl alcohol aqueous solution is 1-5 wt%, and the emulsification stirring speed is 800-1500 rpm.

[0023] A binary organic-inorganic ordered capsule structure prepared by a preparation method according to a binary organic-inorganic ordered capsule structure, comprising gold nanocubes and gold nanospheres grafted with polystyrene on the surface, and the two kinds of nanoparticles form a spatially ordered arrangement at the oil-water interface, and the capsule diameter is distributed in the range of 200-800 nm.

[0024] As a further solution of the present invention: the gold nanocubes and gold nanospheres are arranged in an alternating pattern or an aggregated pattern in regions on the capsule surface.

[0025] As a further solution of the present invention: by regulating the polystyrene ligand chain length and the mixing ratio of the two kinds of nanoparticles, the distance between the nanoparticles on the capsule surface can be accurately adjusted within the range of 5-20 nm.

[0026] As a further solution of the present invention: the capsule structure has a characteristic surface plasmon resonance absorption peak in the near-infrared region of 650-900 nm, and the photothermal conversion efficiency reaches 35-50%.

[0027] As a further solution of the present invention: the capsule encapsulates a therapeutic drug, and the drug loading amount can reach 10-30% of the mass of the capsule.

[0028] The beneficial effects of the present invention:

[0029] Improved universality: Through the emulsion interface confinement assembly strategy, the confined space formed by the oil-water interface is used as a template to reduce the interference of the external environment on the assembly process. In the emulsion system, the hydrophobic segments of polystyrene (PS)-grafted nanoparticles and n-hexadecane act synergistically and spontaneously anchor on the oil-water interface, avoiding the harsh requirements for the hydrophilic-hydrophobic parameters of the nanoparticle surface in the traditional method, and being applicable to the co-assembly of heterogeneous nanoparticles of different materials (such as gold, silver, semiconductors, etc.) and morphologies (cubes, spheres, rods, etc.).

[0030] Enhanced structural uniformity: By controlling the chloroform evaporation rate (slow evaporation at room temperature for 3 days) and the concentration of the PVA aqueous phase stabilizer (1-5 wt%), the ordered packing kinetic process of the nanoparticles at the emulsion droplet interface is ensured to be controllable, significantly reducing the generation of metastable structures, and improving the capsule diameter uniformity (200-800 nm) and the repeatability of particle arrangement.

[0031] Establishment of the assembly mechanism model: By regulating the chain length of the PS ligand (2k - 30k Da) and the mixing ratio of the two types of nanoparticles (1:5 to 5:1), the dominant effects of the entropy-driven effect (polymer chain conformational entropy) and the interfacial energy competition (geometric shape differences of nanoparticles) on the arrangement pattern were revealed. For example, short-chain PS (2k Da) induces an alternating arrangement of cubes and spheres by enhancing the steric hindrance between nanoparticles; long-chain PS (30k Da) promotes regional aggregation through chain entanglement, providing theoretical guidance for the curved surface assembly of heterogeneous particles.

[0032] Structure-property programmability: Based on the correlation between the surface plasmon resonance (SPR) coupling effect and the photothermal conversion efficiency, by precisely adjusting the nanoparticle spacing on the capsule surface (5 - 20 nm), the wavelength shift control of the near-infrared absorption peak (650 - 900 nm) and the quantitative optimization of the photothermal efficiency (35 - 50%) were achieved, providing a predictable structure-property relationship model for the design of multifunctional diagnosis and treatment platforms.

[0033] Integration of diagnosis and treatment functions: Through the synergistic effect of encapsulating drugs inside the capsule (loading amount 10 - 30%) and the photothermal nanoparticles on the surface, the integrated function of "imaging - treatment - controlled release" was achieved. For example, gold nanocubes provide photothermal effects, gold nanospheres enhance the CT imaging contrast, and n-hexadecane serves as a hydrophobic drug carrier, breaking through the performance limitations of traditional single-functional nanocarriers.

[0034] Expansion of process compatibility: By adjusting the emulsification stirring speed (800 - 1500 rpm) and the composition of the organic phase (n-hexadecane proportion 10 - 30%), it is compatible with large-scale preparation technologies such as microfluidics and membrane emulsification, laying a foundation for industrial production. Description of the drawings

[0035] Figure 1 Transmission electron microscope (TEM) images of the gold nanocubes and gold nanospheres prepared in the examples.

[0036] Figure 2 SEM image of the binary capsule structure prepared in Example 1. Detailed implementation manners

[0037] The methods of the present invention will be described below through specific examples, but the present invention is not limited thereto. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0038] In the following examples, the experimental methods are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0039] The present invention will be further described below in combination with specific examples.

[0040] (1) Synthesis of Gold Nanocubes and Gold Nanospheres

[0041] Preparation of Gold Nanocubes

[0042] Preparation of seed solution: Mix 7.5 mL of CTAB solution (0.1 M) with 0.25 mL of chloroauric acid trihydrate solution (0.01 M), quickly add 0.6 mL of freshly prepared aqueous NaBH4 solution (0.01 M), and stir vigorously for 2 minutes. The resulting solution is allowed to stand and ripen at 25 °C for 1 hour.

[0043] Preparation of growth solution: Add 3.2 mL of CTAB (0.1 M), 0.4 mL of chloroauric acid trihydrate (0.01 M), and 1.9 mL of ascorbic acid (0.1 M) to 16 mL of deionized water in sequence. After gently shaking and mixing evenly, inject 0.012 mL of the seed solution diluted 10 times. The mixed system is allowed to stand at 27 °C for 12 hours, and after two centrifugal purifications (10,000 rpm, 8 min / time), it is finally dispersed in deionized water for standby.

[0044] Preparation of gold nanospheres: Add 1 mL of chloroauric acid trihydrate solution (10 mg / mL) to 100 mL of boiling deionized water, quickly inject 3 mL of sodium citrate solution (10 mg / mL) under reflux, and continuously stir and react for 30 minutes. After cooling to room temperature, centrifuge and concentrate (14,000 rpm, 30 min) to obtain a dispersion of nanospheres with uniform particle size.

[0045] (2) Ligand Modification on the Surface of Nanoparticles

[0046] Mix 10 mL of a tetrahydrofuran solution of thiol-terminated polystyrene (PS-SH, Au / SH molar ratio 1:0.1) with the purified nanoparticle dispersion. Ultrasonically treat for 2.5 hours to promote ligand exchange. After standing for 24 hours, centrifuge (10,000 rpm, 30 min), and redisperse the precipitate in tetrahydrofuran. After repeating the PS-SH grafting step once, gradually add ethanol to induce nanoparticle precipitation. After 4 - 5 centrifugation-dispersion cycles (10,000 rpm, 30 min / time), remove free CTAB and unreacted PS-SH, and finally obtain PS-modified nanoparticles dispersed in chloroform, labeled as:

[0047] AuNCs@PS 12k (Cube, PS number-average molecular weight 12 kDa)

[0048] AuNPs@PS 2k (Sphere, PS number-average molecular weight 2 kDa)

[0049] AuNPs@PS 5k(Sphere, number-average molecular weight of PS is 5 kDa)

[0050] AuNPs@PS 12k (Sphere, number-average molecular weight of PS is 12 kDa)

[0051] (3) Preparation of binary organic / inorganic ordered capsule structure

[0052] Example 1

[0053] Take 60 μL of AuNCs@PS 12k chloroform solution (30 mg / mL), 20 μL of AuNPs@PS 2k chloroform solution (10 mg / mL) and 20 μL of n-hexadecane solution (10 mg / mL), mix them and inject into 1 mL of polyvinyl alcohol (PVA) aqueous solution (3 mg / mL), stir and emulsify at 850 rpm for 3 minutes. Let it stand at room temperature for 3 days to allow chloroform to volatilize naturally, and obtain a binary capsule with surface nanoparticles arranged alternately.

[0054] Example 2

[0055] Replace AuNPs@PS 2k in Example 1 with AuNPs@PS 5k (10 mg / mL), with other conditions unchanged, a binary capsule with a nanoparticle spacing of 12 nm is prepared, and the surface shows a gradient arrangement feature.

[0056] Example 3

[0057] Use AuNPs@PS 12k (10 mg / mL) to replace AuNPs@PS 2k in Example 1, keep other parameters the same, and obtain a binary capsule structure with nanoparticles aggregated in sub-regions, and the particle spacing is extended to 18 nm.

[0058] Note:

[0059] 1. In Examples 1 - 3, by adjusting the molecular weight of the PS ligand (2k - 12k Da), the influence of the polymer chain length on the arrangement pattern of nanoparticles was systematically verified;

[0060] 2. n-Hexadecane as a co-solvent can regulate the oil-water interfacial tension, and its addition amount (20 μL) accounts for 20% of the total volume of the organic phase, which cooperates with the PVA concentration (3 mg / mL) to ensure the stability of the emulsion droplets;

[0061] 3. The chloroform slow-release process (3 days) ensures the ordered self-assembly of nanoparticles at the interface and avoids defective structures caused by rapid volatilization.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a binary organic-inorganic ordered capsule structure, characterized in that: The following steps are involved: (1) Synthesis of gold nanocubes and gold nanospheres: a. Preparation of gold nanocubes: Mix a CTAB aqueous solution, an ascorbic acid aqueous solution and a trihydrate tetrachloroauric acid aqueous solution to form a growth solution, add a NaBH4-reduced seed solution, and react at a constant temperature of 27-30°C for 12-24 hours; b. Preparation of gold nanospheres: Under boiling reflux conditions, sodium citrate solution was added to tetrachloroauric acid trihydrate aqueous solution for reduction reaction, and centrifuged and concentrated to obtain nanospheres with uniform particle size; (2) Ligand modification of nanoparticle surface: a. Mixing a tetrahydrofuran solution of thiol-terminated polystyrene PS-SH with the aqueous solution of nanoparticles obtained in step (1), ultrasonically treating for 2-3 hours and then allowing to stand for 24 hours; b. Purify the grafted product by ethanol sedimentation method, remove free CTAB and unreacted PS-SH by 4-5 cycles of centrifugation-dispersion, and finally obtain chloroform-dispersed PS-modified nanoparticles; (3) Emulsion interface restricted assembly: a. Dissolving PS-modified gold nanocubes, gold nanospheres and n-hexadecane in chloroform at a predetermined ratio to form a mixed organic phase; b. The mixed organic phase is injected into the polyvinyl alcohol (PVA) aqueous solution to emulsify into emulsion droplets, and the chloroform is controlled to evaporate slowly at room temperature for 3 days to obtain a binary ordered capsule structure.

2. The method for preparing a binary organic-inorganic ordered capsule structure according to claim 1, characterized in that: The side length of the gold nanocube in step (1) a is 40-80 nm, and the diameter of the gold nanosphere in step (1) b is 20-50 nm.

3. The method for preparing a binary organic-inorganic ordered capsule structure according to claim 2, characterized in that: The number average molecular weight of the mercapto-terminated polystyrene in step (2) a is 5k-30kDa, and the grafting density is 1.2-2.5 chains / nm 2 .

4. The method for preparing a binary organic-inorganic ordered capsule structure according to claim 3, characterized in that: In step (3) a, the molar ratio of the gold nanocubes to the gold nanospheres is 1:5 to 5:1, and the amount of n-hexadecane added is 10-30% of the total volume of the organic phase.

5. The method for preparing a binary organic-inorganic ordered capsule structure according to claim 4, characterized in that: In the step (3) b, the concentration of the polyvinyl alcohol aqueous solution is 1-5 wt %, and the emulsification stirring speed is 800-1500 rpm.

6. A binary organic-inorganic ordered capsule structure prepared according to the method of claim 5, characterized in that: It contains gold nanocubes and gold nanospheres with polystyrene grafted on the surface. The two nanoparticles form an orderly spatial arrangement at the oil-water interface, and the capsule diameter is distributed in the range of 200-800nm.

7. The binary organic-inorganic ordered capsule structure according to claim 6, characterized in that: The gold nanocubes and gold nanospheres are arranged alternately or aggregated in different regions on the capsule surface.

8. The binary organic-inorganic ordered capsule structure according to claim 6, characterized in that: By adjusting the length of the polystyrene ligand chain and the mixing ratio of the two nanoparticles, the distance between nanoparticles on the capsule surface can be precisely adjusted within the range of 5-20nm.

9. The binary organic-inorganic ordered capsule structure according to claim 6, characterized in that: The capsule structure has a characteristic surface plasma resonance absorption peak in the near-infrared region of 650-900nm, and the light-to-heat conversion efficiency reaches 35-50%.

10. The binary organic-inorganic ordered capsule structure according to claim 6, characterized in that: The capsule contains therapeutic drugs, and the drug loading amount can reach 10-30% of the capsule mass.

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