Food-grade anisotropic nanoparticles with double-domain partition structure as well as preparation method and application of food-grade anisotropic nanoparticles

Abstract

The invention discloses a food-grade anisotropic nano-particle with a double-domain partition structure and a preparation method of the food-grade anisotropic nano-particle. The nanoparticles comprise shellac and ethyl cellulose, and the shellac and the ethyl cellulose form a spatially distinguishable double-domain partition structure in a single particle, so that the particles are anisotropic. The method comprises the following steps: dissolving shellac and ethyl cellulose in a water-soluble organic solvent to form an organic phase, dissolving polysorbate 80 in water to form a water phase, carrying out impurity removal treatment and temperature balance, rapidly adding the organic phase into the water phase under shear mixing conditions, and carrying out solid-liquid separation to obtain the nano-precipitate and particle internal phase separation based on solvent replacement induction. A nano-particle dispersion system with a double-domain partition structure is obtained; and performing purification treatment to obtain the nano-particle aqueous dispersion. The method is clear in process path and high in controllability, a double-domain partition anisotropic structure can be stably constructed, and the obtained dispersion system has good dispersion stability and storage stability.

Description

Technical Field

[0001] This invention specifically relates to a food-grade anisotropic nanoparticle with a dual-domain partitioned structure, its preparation method, and its application, belonging to the field of food colloid technology. Background Technology

[0002] Anisotropic particles (i.e., Janus particles) are particulate materials that exhibit spatially asymmetric composition or interfacial property distributions in different regions of the same particle. Due to this spatial asymmetry, particles can serve as the basic unit for interfacial orientation assembly and interfacial structure control, providing a material basis for constructing tunable interfacial structures and functional assemblies. Existing research on the structural construction and controllable preparation of Janus particles has developed various technical routes, including surface selective modification, microfluidic control preparation, template / masking construction, stepwise growth, and phase separation curing, to obtain anisotropic particle systems of different sizes, morphologies, and microstructures. For food-related systems, the construction of food-grade anisotropic particles based on natural or edible materials has potential applications; however, further research and application development depend on the ability to stably and reproducibly obtain target particles with well-defined structures and evaluable properties.

[0003] Compared to inorganic materials or petrochemical polymer systems, food-grade natural polymer systems have specific requirements in terms of material selection, safety compatibility, and process scale-up. Especially when the target structure is advanced to the nanoscale and a two-component polymer system is used, achieving controlled construction of "unipart partitioning" is often more difficult: the two components need to complete co-granulation within a short timescale and undergo controlled phase separation along a specific path, while avoiding the formation of non-target structures such as core-shell coatings, homogeneous mixed particles, or non-specific aggregates. This process is highly sensitive to solvent displacement behavior, mixing shear conditions, temperature windows, and the compatibility and phase separation kinetics of the two components, easily leading to insufficient partitioning clarity, morphological deviations, particle size distribution fluctuations, and poor batch-to-batch consistency, thus affecting the reliability of structural characterization and comparative evaluation. For ease of description and definition, the "food-grade anisotropic nanoparticles with dual-domain partitioned structure" described in this application refers to the formation of two spatially distinguishable partitioned regions within the same nanoparticle, and the partitions differ in composition or surface properties; this structure is distinct from core-shell coated structures, homogeneous mixed particles, and aggregates formed by non-specific aggregation of different particles.

[0004] Existing strategies for preparing anisotropic particles generally suffer from problems such as complex processes, high equipment requirements, limited yield, and difficulty in scale-up. When the target is at the nanoscale and the raw material is a dual polymer system, the structure is more sensitive to process disturbances, easily leading to unclear partitioning and widening of particle size distribution. For example, application number CN202211665278.1 and publication number CN116102892A disclose a dumbbell-shaped Janus particle made from zein and shellac, and uses a coaxial flow focusing chip (microfluidics) to prepare the particle, with a reported particle size range of 300 nm to 2 μm. However, its preparation route depends on microfluidics, and the process is relatively lengthy, which is not conducive to continuous scale-up in industrial production.

[0005] For example, application number CN202210882607.1 and publication number CN115368591A disclose a chitosan-starch composite Janus particle obtained using an O / W type Pickering emulsion as a template. Its Janus characteristics mainly originate from localized bonding / modification of the particle surface, rather than the formation of distinguishable dual-domain partitions within the same nanoparticle. Furthermore, the main particle size is on the micrometer scale (1–3 μm), which differs in scale from the target of preparing anisotropic nanoparticles and regulating interface anchoring behavior.

[0006] The article "Biocompatible amphiphilic hydrogel-solid dimer particles ascolloidal surfactants" describes the microfluidic construction of amphiphilic dimer particles composed of alginate hydrogel spheres and shellac hydrophobic solid spheres. These particles exhibit directional residence at the oil-water interface, thereby stabilizing W / O and O / W emulsions. However, these particles are micron-sized dimers (on the order of 25 μm), and their preparation involves a fluorocarbon oil continuous phase and a specific surfactant system, which limits their compatibility with food systems.

[0007] Therefore, it is still necessary to provide a preparation method based on food-grade material system, with a clear process path and repeatable implementation, to stably obtain food-grade anisotropic nanoparticles with well-defined partitions under feasible operating conditions, and to achieve effective control over particle size and morphology distribution, thereby laying a reliable material foundation for further application research of this type of particle. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing food-grade anisotropic nanoparticles with a dual-domain partitioned structure, and an aqueous dispersion of such nanoparticles obtained by this method. This addresses the problems of difficulty in controllably constructing the dual-domain partitioned structure and easy deviation of particle morphology in food-grade two-component nanosystems in existing technologies, thereby providing a reliable material basis for the stable preparation and subsequent application of this type of nanoparticle. To facilitate understanding of the structural formation basis of this invention, the formation mechanism of the dual-domain partitioned structure is explained in principle below.

[0009] The dual-domain partitioned anisotropic structure of this invention originates from the co-precipitation and single-particle-scale component partitioning process of shellac and ethyl cellulose under solvent displacement conditions. After simultaneously dissolving shellac and ethyl cellulose in a water-miscible organic solvent to form a homogeneous organic phase, an aqueous phase is rapidly added under shear mixing conditions. The water-miscible organic solvent diffuses into the aqueous phase and is diluted, causing a rapid decrease in the system's solubility for the two polymers, thereby triggering supersaturation and rapid nucleation and nanoprecipitation to form a nanoparticle dispersion system.

[0010] During particle nucleation and growth, shellac and ethyl cellulose differ in solubility, aggregation kinetics, and interactions, leading to competitive enrichment of both within the particles and the formation of spatially distinguishable enrichment regions. This results in a dual-domain partitioning structure consisting of shellac-enriched and ethyl cellulose-enriched domains. This dual-domain partitioning structure exhibits a parallel partitioning pattern, the formation of which can be attributed to the interfacial interactions between the shellac-enriched and ethyl cellulose-enriched domains, as well as between each and the continuous phase, jointly determining the partitioning arrangement within the particle formation window. When the interfacial conditions for one component to form a continuous coating layer on the other are not met, the system tends to form parallel partitioning rather than a core-shell coating structure, thus exhibiting a Janus anisotropic configuration.

[0011] Furthermore, by changing the ratio of shellac and ethyl cellulose, the shape of the nanoparticles can be altered, specifically by selecting a dumbbell shape or a snowman shape.

[0012] The above principles are used to aid in understanding the present invention and do not constitute a limitation on the scope of protection.

[0013] Based on the above principles, this invention provides a method for preparing food-grade anisotropic nanoparticles with a dual-domain partitioned structure, comprising the following steps: 1) Dissolve shellac and ethyl cellulose in an organic solvent to obtain a clear organic phase solution; wherein the mass ratio of shellac to ethyl cellulose is 0.5:1 to 2:1; the concentration of shellac in the organic phase solution is 2 to 30 mg / mL, and the concentration of ethyl cellulose is 2 to 30 mg / mL; the organic solvent is a water-miscible organic solvent.

[0014] 2) Dissolve polysorbate 80 in water to obtain an aqueous solution; wherein the concentration of polysorbate 80 in the aqueous solution is 0.01% to 1.0% (w / v).

[0015] 3) The organic phase solution obtained in step 1) and the aqueous phase solution obtained in step 2) are filtered separately to remove insoluble substances; the filtration is performed using a membrane filter with a pore size of 0.45 μm. After filtration, the organic phase solution and the aqueous phase solution are subjected to temperature equilibration treatment to make the two phases have the same temperature, which is 25-70℃.

[0016] 4) In step 2), while the aqueous solution is in a shear-mixing state, the organic solution obtained in step 1) is rapidly injected into the aqueous solution using a syringe and mixed, causing shellac and ethyl cellulose to co-precipitate and form a spatially distinguishable dual-domain partitioned structure within the particles, resulting in a nanoparticle dispersion; wherein, the volume ratio of the aqueous solution to the organic solution is 5:1 to 20:1; the shear mixing is vortex mixing, with a vortex rotation speed of 1000 to 3500 rpm; and the mixing time is 5 to 120 s.

[0017] 5) The nanoparticle dispersion obtained in step 4) is subjected to ultrafiltration purification to remove residual organic solvents and free Tween-type nonionic surfactants to obtain an aqueous dispersion of nanoparticles; the ultrafiltration purification includes: placing the nanoparticle dispersion in an ultrafiltration device for retention and washing / replacing with deionized water, repeating the process until the organic solvents and free surfactants are removed.

[0018] Preferably, in one embodiment of the present invention, the organic solvent is ethanol.

[0019] Preferably, in one embodiment of the present invention, the mass ratio of shellac to ethyl cellulose is 1:1, and the total polymer concentration is about 20 mg / mL. Studies have shown that when the mass ratio of shellac to ethyl cellulose is 1:1, the resulting nanoparticles have a dumbbell-shaped morphology; when the mass ratio is adjusted to other ratios, the particle morphology can be transformed into a snowman-like shape.

[0020] Preferably, in one embodiment of the present invention, the concentration of polysorbate 80 is 0.1% (w / v).

[0021] Preferably, in one embodiment of the present invention, the two-phase temperature balancing treatment temperature is 50°C.

[0022] Preferably, in one embodiment of the present invention, the volume ratio of the aqueous phase to the organic phase is 10:1, the vortex rotation speed is 3000 rpm, and the mixing time is 30 s.

[0023] Preferably, in one embodiment of the present invention, the ultrafiltration membrane used in the ultrafiltration device has a molecular weight cutoff of 100 kDa.

[0024] The present invention also provides a food-grade anisotropic nanoparticle aqueous dispersion with a dual-domain partitioned structure prepared by the above preparation method.

[0025] Compared with the prior art, the beneficial effects and advantages of the present invention are: (1) Using shellac and ethyl cellulose, two materials with food applicability and good biocompatibility, as building blocks, food-grade anisotropic Janus nanoparticles with a dual-domain partitioned structure were prepared. The nanoparticles form spatially distinguishable shellac and ethyl cellulose phases within the same particle, enabling the system to simultaneously possess the hydrophobic film-forming properties of shellac and the structural support / forming ability of ethyl cellulose, thereby providing a material basis for constructing stable particle and interface structural units.

[0026] (2) The preparation process is based on solvent replacement-induced co-precipitation and vortex mixing in the ethanol / water system, and purification is achieved by ultrafiltration replacement. The process path is clear, the operation steps are relatively simple, the dependence on complex special equipment is low, and it has good operability and repeatability, which is conducive to achieving stable preparation and providing a process basis for subsequent scale-up.

[0027] (3) It can achieve the controllable construction of Janus nanoparticles in terms of particle size, morphology and partitioned structure. By adjusting the concentration and mass ratio of shellac and ethyl cellulose in a good solvent, and by combining process parameters such as the volume ratio of aqueous phase to organic phase, shear strength and temperature equilibrium conditions, the particle formation process and particle size / morphology distribution can be adjusted to meet the different requirements of different systems for particle parameters.

[0028] (4) Under the conditions of a food-grade two-component system, it can achieve controlled phase separation within the same particle and form a stable dual-domain partition structure, thereby improving the stability of obtaining anisotropic target structures, reducing the probability of non-target morphologies such as core-shell coating, homogeneous mixing or non-specific aggregation, and improving the batch-to-batch consistency of the system.

[0029] (5) The obtained dual-domain partitioned anisotropic nanoparticles have the characteristics of food-grade material system and particle structure unit, and can be used as particulate structural components or interface structural units in oil-water interface related systems to support the construction of interface structure and the improvement of system stability. In addition, based on the spatial differentiation of components provided by its dual-domain partitioned structure, the nanoparticles obtained in this invention can also be used for system construction in scenarios such as the encapsulation and dispersion of hydrophobic components, providing a material and structural basis for its extended application in food-related systems. Attached Figure Description

[0030] Figure 1 The graph shows the changes in particle size and polydispersity index (PdI) of the nanoparticle dispersions obtained in Examples 1 to 15.

[0031] Figure 2 The graph shows the ζ-potential changes of the nanoparticle dispersions obtained in Examples 1 to 15.

[0032] Figure 3 The graph shows the changes in particle size and polydispersity index (PdI) of the nanoparticle dispersions obtained in Examples 16 to 27.

[0033] Figure 4 The graph shows the zeta potential changes of the nanoparticle dispersions obtained in Examples 16 to 27.

[0034] Figure 5 Scanning electron microscope (SEM) images of the nanoparticles obtained in Examples 3, 8, 13, 19, 23 and 27.

[0035] Figure 6 The images are scanning electron microscope (SEM) images of the nanoparticles obtained in Examples 16 to 19.

[0036] Figure 7 The Fourier transform infrared (FTIR) spectra of the samples obtained in Example 19 and Comparative Examples 1 to 3 are shown.

[0037] Figure 8 The thermogravimetric (TG) curves of the samples obtained in Example 19 and Comparative Examples 1 to 3 are shown.

[0038] Figure 9 The differential thermogravimetric (DTG) curves of the samples obtained in Example 19 and Comparative Examples 1 to 3 are shown.

[0039] Figure 10 Differential scanning calorimetry (DSC) curves of the samples obtained in Example 19 and Comparative Examples 1 to 3.

[0040] Figure 11 The graph shows the changes in particle size, polydispersity index (PdI), and zeta potential of the nanoparticles obtained in Example 19 during 60 days of storage.

[0041] Figure 12 The image shows the backscattering (BS) signal curves of the nanoparticle dispersions obtained in Example 19 and Comparative Examples 1 to 3.

[0042] Figure 13 The graph shows the Turbiscan stability index (TSI) changes of the nanoparticle dispersions obtained in Example 19 and Comparative Examples 1 to 3.

[0043] Figure 14 The graph shows the changes in particle size, polydispersity index (PdI), and zeta potential of the nanoparticles obtained in Example 19 after treatment at 25°C, 50°C, and 70°C.

[0044] Figure 15 The graph shows the changes in particle size, polydispersity index (PdI), and zeta potential of the nanoparticles obtained in Example 19 under different pH conditions.

[0045] Figure 16 The graph shows the changes in particle size, polydispersity index (PdI), and zeta potential of the nanoparticles obtained in Example 19 under different NaCl concentrations (ionic strengths). Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments. It should be noted that these descriptions of embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the materials and reagents used, unless otherwise specified, are commercially available.

[0048] Example 1: Shellac and ethyl cellulose were weighed and dissolved in ethanol at a mass ratio of 1:1 to prepare a clear organic phase solution. The concentration of shellac and ethyl cellulose was 2 mg / mL. Polysorbate 80 was separately weighed and dissolved in deionized water to prepare an aqueous phase solution with a polysorbate 80 concentration of 0.1% (w / v). Both the organic and aqueous phase solutions were filtered through 0.45 μm filter membranes to remove insoluble matter. The aqueous phase was placed on a vortex mixer, and the speed was set to 3000 rpm. Under vortex mixing conditions, the organic phase was rapidly injected into the aqueous phase using a syringe, allowing the shellac and ethyl cellulose to co-granulate under solvent displacement conditions, forming spatially distinguishable dual-domain partitioned structures within the particles, resulting in a nanoparticle dispersion with an aqueous phase to organic phase volume ratio of 10:1 and a total mixing time of 30 s. The obtained nanoparticle dispersion was transferred to an ultrafiltration device and purified by ultrafiltration replacement using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa to remove residual ethanol and free polysorbate 80, resulting in a dual-domain partitioned anisotropic nanoparticle aqueous dispersion.

[0049] Example 2: The difference from Example 1 is that the concentrations of shellac and ethyl cellulose are 4 mg / mL.

[0050] Example 3: The difference from Example 1 is that the concentrations of shellac and ethyl cellulose are 6 mg / mL.

[0051] Example 4: The difference from Example 1 is that the concentration of shellac and ethyl cellulose is 10 mg / mL.

[0052] Example 5: The difference from Example 1 is that the concentration of shellac and ethyl cellulose is 20 mg / mL.

[0053] Example 6: The difference from Example 1 is that the concentration of polysorbate 80 is 0.5%.

[0054] Example 7: The difference from Example 2 is that the concentration of polysorbate 80 is 0.5%.

[0055] Example 8: The difference from Example 3 is that the concentration of polysorbate 80 is 0.5%.

[0056] Example 9: The difference from Example 4 is that the concentration of polysorbate 80 is 0.5%.

[0057] Example 10: The difference from Example 5 is that the concentration of polysorbate 80 is 0.5%.

[0058] Example 11: The difference from Example 1 is that the concentration of polysorbate 80 is 1.0%.

[0059] Example 12: The difference from Example 2 is that the concentration of polysorbate 80 is 1.0%.

[0060] Example 13: The difference from Example 3 is that the concentration of polysorbate 80 is 1.0%.

[0061] Example 14: The difference from Example 4 is that the concentration of polysorbate 80 is 1.0%.

[0062] Example 15: The difference from Example 5 is that the concentration of polysorbate 80 is 1.0%.

[0063] Example 16: Shellac and ethyl cellulose were weighed and dissolved in ethanol at a mass ratio of 1:1 to prepare a clear organic phase solution. The concentration of shellac and ethyl cellulose was 2 mg / mL. Polysorbate 80 was separately weighed and dissolved in deionized water to prepare an aqueous phase solution with a polysorbate 80 concentration of 0.1% (w / v). Both the organic and aqueous phase solutions were filtered through 0.45 μm filter membranes to remove insoluble matter. After filtration, both phases were placed at 50°C for temperature equilibration. The aqueous phase was placed on a vortex mixer, and the speed was set to 3000 rpm. Under vortex mixing conditions, the organic phase was rapidly injected into the aqueous phase using a syringe, allowing the shellac and ethyl cellulose to co-granulate under solvent displacement conditions, forming spatially distinguishable dual-domain partitioned structures within the particles, resulting in a nanoparticle dispersion with an aqueous phase to organic phase volume ratio of 10:1 and a total mixing time of 30 s. The obtained nanoparticle dispersion was transferred to an ultrafiltration device and purified by ultrafiltration replacement using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa to remove residual ethanol and free polysorbate 80, resulting in a dual-domain partitioned anisotropic nanoparticle aqueous dispersion.

[0064] Example 17: The difference from Example 16 is that the concentration of shellac and ethyl cellulose is 6 mg / mL.

[0065] Example 18: The difference from Example 16 is that the concentration of shellac and ethyl cellulose is 10 mg / mL.

[0066] Example 19: The difference from Example 16 is that the concentration of shellac and ethyl cellulose is 20 mg / mL.

[0067] Example 20: The difference from Example 16 is that the concentration of polysorbate 80 is 0.5%.

[0068] Example 21: The difference from Example 17 is that the concentration of polysorbate 80 is 0.5%.

[0069] Example 22: The difference from Example 18 is that the concentration of polysorbate 80 is 0.5%.

[0070] Example 23: The difference from Example 19 is that the concentration of polysorbate 80 is 0.5%.

[0071] Example 24: The difference from Example 16 is that the concentration of polysorbate 80 is 1.0%.

[0072] Example 25: The difference from Example 17 is that the concentration of polysorbate 80 is 1.0%.

[0073] Example 26: The difference from Example 18 is that the concentration of polysorbate 80 is 1.0%.

[0074] Example 27: The difference from Example 19 is that the concentration of polysorbate 80 is 1.0%.

[0075] Comparative Example 1: Shellac was weighed and dissolved in ethanol to prepare a clear organic phase solution. The concentration of shellac was 20 mg / mL. Polysorbate 80 was separately weighed and dissolved in deionized water to prepare an aqueous phase solution with a polysorbate 80 concentration of 0.1% (w / v). Both the organic and aqueous phase solutions were filtered through 0.45 μm filter membranes to remove insoluble matter. After filtration, both phases were placed at 50°C for temperature equilibration. The aqueous phase was placed on a vortex mixer, and the mixing speed was set to 3000 rpm. Under vortex mixing conditions, the organic phase was rapidly injected into the aqueous phase using a syringe to obtain a nanoparticle dispersion with a water-to-organic phase volume ratio of 10:1 and a total mixing time of 30 s. The obtained nanoparticle dispersion was transferred to an ultrafiltration device and purified by ultrafiltration displacement using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa to remove residual ethanol and free polysorbate 80, yielding an aqueous dispersion of shellac nanoparticles.

[0076] Comparative Example 2: Ethyl cellulose was weighed and dissolved in ethanol to prepare a clear organic phase solution. The concentration of ethyl cellulose was 20 mg / mL. Polysorbate 80 was separately weighed and dissolved in deionized water to prepare an aqueous phase solution with a polysorbate 80 concentration of 0.1% (w / v). Both the organic and aqueous phase solutions were filtered separately through 0.45 μm filter membranes to remove insoluble matter. After filtration, both phases were placed at 50°C for temperature equilibration. The aqueous phase was placed on a vortex mixer, and the mixing speed was set to 3000 rpm. Under vortex mixing conditions, the organic phase was rapidly injected into the aqueous phase using a syringe to obtain a nanoparticle dispersion with a water-to-organic phase volume ratio of 10:1 and a total mixing time of 30 s. The obtained nanoparticle dispersion was transferred to an ultrafiltration device and purified by ultrafiltration displacement using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa to remove residual ethanol and free polysorbate 80, yielding an aqueous dispersion of ethyl cellulose nanoparticles.

[0077] Comparative Example 3: Aqueous dispersions of shellac nanoparticles and ethyl cellulose nanoparticles were prepared according to the methods of Comparative Examples 1 and 2, respectively. Both were filtered through a 0.45 μm filter, equilibrated at 50°C, and rapidly injected into granules at a water phase vortex speed of 3000 rpm. Ultrafiltration purification was performed using an ultrafiltration membrane with a molecular weight cutoff of 100 kDa to remove residual ethanol and free polysorbate 80. The above-mentioned aqueous dispersions of shellac nanoparticles and ethyl cellulose nanoparticles were mixed at a mass ratio of 1:1 (preferably, the two dispersions were mixed in equal volumes after conversion based on the particle solid content; if the solid content is the same, a volume ratio of 1:1 can be used). The mixture was magnetically stirred or vortexed at room temperature until fully homogeneous, resulting in a mixed dispersion of shellac nanoparticles and ethyl cellulose nanoparticles. This mixed dispersion is a coexistence system of two single-component nanoparticles, and its particle structure does not exhibit the dual-domain partitioning characteristic within the same particle, serving as a comparison with the dual-domain partitioning anisotropic nanoparticles obtained in the examples.

[0078] Experimental Example 1: Measurement of Particle Size, PdI, and Zeta Potential The nanoparticle aqueous dispersions obtained in Examples 1 to 27 were diluted with deionized water to 0.1% (w / v). The hydrated particle size, dispersion index (PdI) and zeta potential of the samples were measured using a Malvern nanoparticle size analyzer at 25°C, and the measurement results were recorded.

[0079] Figure 1 and Figure 2The effects of polysorbate 80 concentration on the particle size, PdI, and potential of Janus nanoparticle aqueous dispersions prepared at room temperature are shown. At room temperature, the polysorbate 80 concentration significantly affects the particle size distribution and apparent zeta potential of Janus nanoparticles. Taking 0.1% polysorbate 80 (Examples 1-5) as an example, the resulting particles generally exhibited a negative zeta potential (approximately -25 to -28 mV), but the particle size varied considerably with polymer concentration. Example 5 showed a significantly larger particle size (approximately 160 nm), indicating that low Tween systems at room temperature are prone to particle growth or agglomeration. Increasing the polysorbate 80 concentration to 0.5% (Examples 6-10) still resulted in particle size variations with formulation, but the zeta potential generally shifted upwards to approximately -18 to -21 mV, indicating that the enhanced adsorption and coverage of polysorbate 80 produces a certain charge-masking effect. Meanwhile, the nanoparticles in Example 10 exhibited a potential of approximately -26 mV, indicating that the increased surface charge contribution of the polymer under higher polymer concentration formulation conditions could partially offset the masking effect of polysorbate 80. When the concentration was further increased to 1.0% polysorbate 80 (Examples 11-15), the absolute value of the zeta potential decreased further. While Examples 11 and 12 showed smaller particle sizes (approximately 50-60 nm), Example 13 showed a significantly increased PdI (approximately 0.6), indicating that excessive polysorbate 80 at room temperature boundary formulations could lead to the coexistence of multiple particle size groups and poor dispersibility. Therefore, combinations with high PdI at room temperature are not preferred. Based on the above room temperature screening results, subsequent preparations were carried out at 50°C to obtain a more controllable nucleation / curing process and a more stable particle structure. It was preferred to control the polysorbate 80 concentration within the range of 0.1-0.5% to balance interfacial stability and dispersion uniformity.

[0080] Figure 3 and Figure 4The effects of polysorbate 80 concentration on the particle size, PdI, and potential of the Janus nanoparticle aqueous dispersion prepared at 50 °C are shown. At 50°C (Examples 16-27), the particle size of Janus nanoparticles increased overall as the polymer concentration increased from 2 mg / mL to 20 mg / mL (approximately from 50 nm to 160-190 nm). Furthermore, at polymer concentrations ≥6 mg / mL (Examples 17-19, 21-23, 25-27), the PdI was generally low, indicating that more concentrated particle distribution could be obtained at this temperature. The concentration of polysorbate 80 had a regulatory effect on particle size and surface charge, with more pronounced differences at higher polymer concentrations. Specifically, 0.5% polysorbate 80 corresponded to larger particle sizes (as in Example 23), while 1.0% polysorbate 80 was more effective in suppressing aggregation and obtaining relatively more stable particle sizes (as in Example 27). Regarding the zeta potential, all examples showed negative values, and in the 0.1% and 1.0% polysorbate 80 groups, the absolute value of the potential increased to -35 to -40 with increasing polymer concentration. mV (Examples 19, 27), while the overall absolute value of the 0.5% polysorbate 80 group was smaller (Examples 20-23), indicating that an engineerable balance between interfacial stability and apparent potential can be achieved by adjusting the amount of polysorbate 80.

[0081] Experiment Example 2: Observation using a scanning electron microscope The nanoparticle dispersions obtained in Examples 3, 8, 13, 19, 23, 27, and 16 to 19 were dropped onto the surface of a silicon wafer and dried under vacuum. The dried samples were then sputtered with gold to improve conductivity and reduce the influence of charging. Subsequently, the morphological characteristics of the nanoparticles were observed and images were recorded using a field emission scanning electron microscope.

[0082] The results are as follows Figure 5At a polymer concentration of 6 mg / mL, polysorbate 80 significantly affected particle formation and dispersion. Example 3 mainly showed dispersed short ellipsoids / irregular particles with generally poor morphological integrity. In Example 8, the number of particles was significantly reduced and sparsely distributed, indicating that the particle formation efficiency and deposition imaging stability of the preparation conditions in this example were insufficient. Example 13 showed more obvious agglomeration and adhesion clustering, indicating that under excessive surfactant conditions, particles are prone to agglomeration / adhesion during insufficient curing or sample drying. In contrast, it was easier to obtain the target Janus particle appearance when the polymer concentration was 20 mg / mL: Example 19 (0.1%) showed a more typical bispherical / dumbbell-shaped connection structure and was more discrete overall, which is consistent with the appearance characteristics of bispherical Janus particles, and was therefore the preferred example. When the polysorbate 80 was increased to 0.5% (Example 23), the particle boundaries became unclear and accompanied by adhesion / deformation trends. Further increasing it to 1.0% (Example 27) resulted in chain-like connections and fusion. In summary, polysorbate 80 provides interfacial coverage and steric stabilization in this system. However, when the dosage is too high, it enhances the masking effect on the surface of the polymer / new particles, making the particles more prone to fusion and aggregation during the curing stage, thus causing the morphology to change from discrete bispherical to sticky chain-like. Therefore, 0.1% polysorbate 80 is preferred at a polymer concentration of 20 mg / mL (Example 19).

[0083] The effect of polymer concentration on the morphology of Janus particles was further investigated in Examples 16–19. The results are as follows: Figure 6 When the polymer concentration was 2 mg / mL (Example 16), the field of view was dominated by small, short ellipsoidal / irregular particles with blurred boundaries, and the particle integrity and structural consistency were relatively insufficient. When the concentration was increased to 6 mg / mL, the particle outlines became clearer and the number increased, but a certain proportion of asymmetric blocks or slight adhesion were still visible, indicating that morphological dispersion due to insufficient co-aggregation or solidification still existed at this concentration. The particles in Example 18 were relatively large and exhibited a more obvious spherical / semi-fused morphology, indicating that structural solidification and phase separation were beginning to evolve towards a denser structure, but the Janus feature was not prominent enough. In contrast, Example 19 showed a typical bispherical / dumbbell-shaped connection structure with clear individual particle boundaries and the highest morphological recognizability, which better matched the target appearance of bispherical Janus particles. This phenomenon indicates that increasing the polymer concentration can improve the material supply and structural locking efficiency in the phase separation / solidification stage, thereby gradually transforming the irregular and inconsistent morphology at low concentrations into a bispherical Janus morphology that can be stably obtained at high concentrations.

[0084] Experimental Example 3: FTIR Characterization The nanoparticle samples obtained in Example 19 and Comparative Examples 1 to 3 were freeze-dried and then ground. Meanwhile, shellac raw material and ethyl cellulose raw material were ground for later use. Each of the above samples was thoroughly mixed with KBr at a mass ratio of 1:100 (w / w) and pressed into tablets. Fourier transform infrared spectroscopy was used to analyze the samples at 4000–4000 cm⁻¹. -1 Spectra were collected within the range with a resolution of 4 cm⁻¹. -1 The obtained spectra are recorded and saved for analysis of the characteristic functional group absorption peaks and their interactions in the sample.

[0085] The results are as follows Figure 7 The FTIR spectrum of Example 19 retains the characteristic absorption signals of both shellac and ethyl cellulose, which can be used to prove that the two components together constitute the same particle system. Specifically, the shellac-related ester / carboxyl C=O absorption is located at ~1730–1740 cm⁻¹. -1 The area is clearly visible (with shellac at ~1714 / 1744 cm). -1 And Comparative Example 1 at ~1733cm -1 Characteristic peaks correspond to (Ethyl cellulose-related C–H stretching vibrations at ~2927–2980 cm⁻¹). -1 The range appears, while the C–O–C / C–O fingerprint absorption of ethyl cellulose is in the range of ~1110–1115 cm⁻¹. -1 The presence of this feature indicates that the ethyl cellulose backbone structure was effectively introduced and preserved.

[0086] Furthermore, compared to Comparative Example 3 (physical mixing of shellac nanoparticles and ethyl cellulose nanoparticles), Example 19 exhibits non-simple superposition characteristics in several key regions: firstly, the –OH broad peak region is approximately 3314 cm⁻¹, as seen in Comparative Example 1. -1 Adjusted to approximately 3306 cm in Example 19 -1 First, the microenvironment related to the hydroxyl groups in shellac has changed; second, the peak shape and position in the C=O region differ from those in the physically mixed sample, indicating that the carbonyl group is in an environment different from a simple coexistence state; third, at ~1649 cm⁻¹ -1 The presence of a more pronounced absorption signal nearby can serve as evidence that interfacial coupling alters the vibrational environment of functional groups. In summary, Example 19 not only exhibits characteristic absorption peaks of both shellac and ethyl cellulose, but also shows a discernible change in peak position / shape compared to a physical mixture. This indicates that the two components form interfacial coupling within the same particle, thus supporting the conclusion that the resulting particle is a Janus structure rather than a simple physical mixture of two nanoparticles.

[0087] Experimental Example 4: Thermogravimetric Analysis (TGA) The nanoparticle samples obtained in Example 19 and Comparative Examples 1 to 3 were freeze-dried and then ground. Meanwhile, shellac raw material and ethyl cellulose raw material were ground for later use. 5–10 mg of each sample was weighed and placed in a platinum crucible. Thermogravimetric analysis (TG) and differential thermogravimetric (DTG) curves were recorded using a thermogravimetric analyzer under a synthesis air (N2 / O2=80 / 20) atmosphere, with a heating rate of 10 °C / min from 30 °C to 500 °C.

[0088] The results are as follows Figure 8 and Figure 9 Shellac and its nanoparticles (Comparative Example 1) and ethyl cellulose and its nanoparticles (Comparative Example 2) exhibit different thermal decomposition ranges: the ethyl cellulose system shows rapid primary weight loss at approximately 320–380 °C, while the shellac system shows slower, segmented weight loss at higher temperatures. Correspondingly, the TG / DTG curves of the shellac / ethyl cellulose physical mixture (Comparative Example 3) show a simple superposition of the two characteristics, with the primary weight loss peak and high-temperature shoulder peak existing simultaneously, indicating that it is merely coexisting rather than structurally coupled. In contrast, the TG curve of Example 19 (Janus particles) maintains higher quality during the primary weight loss stage (330–420 °C), and the maximum weight loss rate in the DTG is reduced, exhibiting a broader composite peak / shoulder peak, which is significantly different from the superimposed bimodal peak of Comparative Example 3. This indicates that shellac and ethyl cellulose form a tight interfacial bond within the same particle, dispersing and delaying the thermal decomposition process, thus demonstrating superior thermal stability and structural integrity compared to single nanoparticles and their physical mixtures.

[0089] Experimental Example 5: Differential Scanning Calorimetry (DSC) The nanoparticle samples obtained in Example 19 and Comparative Examples 1 to 3 were freeze-dried and then ground. Meanwhile, shellac and ethyl cellulose raw materials were ground for later use. 5–10 mg of each sample was weighed and sealed in an aluminum crucible. Differential scanning calorimetry (DSC) was used for testing, with nitrogen as both purge and protective gas at flow rates of 40 mL / min and 60 mL / min, respectively. The temperature was increased at a preset rate of 10 °C / min, and the heat flow curves were recorded to evaluate the thermal behavior of the samples.

[0090] The results are as follows Figure 10Within the temperature range of 30–210℃, the shellac sample exhibited a significant characteristic thermal effect peak at approximately 50–70℃, indicating a significant thermal response of the shellac component in this temperature range. In Comparative Example 1 (shellac nanoparticles), the intensity of this characteristic peak was significantly reduced, suggesting that nano-sizing can weaken the thermal response of shellac. The heat flow curves of ethyl cellulose raw material and Comparative Example 2 (ethyl cellulose nanoparticles) were generally stable in this temperature range, without exhibiting the same significant characteristic peak as shellac. In Comparative Example 3 (physical mixture of two nanoparticles), the response signal corresponding to the temperature range of shellac was still observed, indicating simple coexistence of components. In contrast, the characteristic thermal effect of shellac in Example 19 (Janus particles) was further weakened and tended to level off in the same temperature range, indicating that shellac and ethyl cellulose formed a tighter interfacial coupling and structural constraint within the same particle, thereby suppressing the thermal response of the shellac segments and improving the thermal stability of the particle structure.

[0091] Experimental Example 6: Evaluation of Storage Stability The aqueous dispersion of nanoparticles obtained in Example 19 was adjusted to pH 7.0 and stored at 4°C for 0–60 days. Samples were taken at preset time points, and after equilibration to 25°C, their hydrated particle size, dispersion index (PdI), and zeta potential were measured and recorded to evaluate the storage stability of the nanoparticle dispersion.

[0092] The results are as follows Figure 11 The dispersion of Example 19 exhibited good colloidal stability throughout storage. The particle size showed only a slow upward trend from 0 to 60 days, increasing from approximately 155–160 nm at 0 days to 175–180 nm at 30 days, and remaining around 180 nm at 60 days, without any sudden increases or significant fluctuations in instability. The corresponding PdI remained at a low level (approximately 0.16–0.26), although it increased slightly over time, it remained within an acceptable narrow distribution range, indicating that the system did not undergo significant widespread aggregation or severe agglomeration. The zeta potential remained within the range of -37 to -40 mV throughout the process and changed very little over time, indicating that the surface electrical properties and charge repulsion of the particles remained stable during storage. Considering the synchronous changes in particle size, PdI, and zeta potential, it can be concluded that the particle size increase in Example 19 during the 60-day storage period was mainly due to slight, slow growth / structural rearrangement, rather than rapid aggregation and sedimentation-type instability, demonstrating good storage stability and application feasibility.

[0093] Experiment Example 7: Evaluation of Physical Stability The nanoparticle aqueous dispersions obtained in Example 19 and Comparative Examples 1 to 3 were diluted to 1 mg / mL. 10 mL of the sample was added to a cylindrical glass sample cell and placed at 25°C. The sample was tested using a multiple light scattering stability analyzer. The sample was scanned every 30 seconds for 8 hours. The backscatter (BS) signal was recorded as a function of sample height and time. The Turbiscan Stability Index (TSI) was calculated to characterize the overall instability of the sample and thus evaluate the physical stability of the nanoparticle dispersion.

[0094] The Turbiscan backscattering (BS) distribution curve as a function of height is shown in the figure below. Figure 12 In Example 19, the curves at various points in time largely overlapped throughout the testing period. The BS variation along the height of the sample column was minimal, and no characteristic stratification signals such as upper layer brightening / lower layer darkening appeared, indicating that the system hardly underwent migration, stratification, or significant aggregation under accelerated conditions. In contrast, the BS curves of Comparative Examples 2 and 3 showed significant shifts and stratification trends over time, suggesting that particles migrated and rearranged their structures along the height direction, indicating insufficient stability. The variation in Comparative Example 1 was between the two, showing a certain degree of stability but still exhibiting slow structural evolution.

[0095] TSI results are as follows Figure 13 In Example 19, the TSI remained close to 0 throughout the 0–8 h period, showing almost no increase over time, indicating that the system was in a highly stable state. The TSI of Comparative Example 1 increased slowly but reached a low final value, indicating only slight instability. The TSI of Comparative Examples 2 and 3 increased rapidly, reaching approximately 10–13 after 8 h, indicating significant instability early in the testing process. Therefore, the Janus particles obtained in Example 19, compared to single-component nanoparticles and their physical mixtures, significantly suppressed particle migration, stratification, and aggregation rearrangement, demonstrating superior dispersion stability. This advantage can be attributed to the formation of a coupling interface between the two components within the same particle, making the surface stabilization layer more effective, while physical mixing merely provides simple coexistence and cannot offer the same level of stability.

[0096] Experimental Example 8: Evaluation of Thermal Stability The aqueous dispersion of nanoparticles obtained in Example 19 was subjected to a pH adjustment to 7.0, and then heat-treated in constant temperature water baths at 25°C, 50°C, and 70°C. After heat treatment, the samples were cooled and equilibrated to 25°C, and their hydrated particle size, dispersion index (PdI), and zeta potential were measured. The changes in parameters before and after treatment at different temperatures were recorded to evaluate the thermal stability of the nanoparticle dispersion.

[0097] As shown in the figure, after treatment at 25℃, 50℃, and 70℃ for 0, 30, and 60 min, the particle size of Example 19 remained within a narrow fluctuation range of approximately 155–165 nm, without any sudden increase due to rising temperature or prolonged holding time. The corresponding PdI remained at a low level (approximately 0.16–0.20), with only slight fluctuations and no significant widening trend. The zeta potential remained a stable negative value at all temperatures and time points, generally approximately -39 to -43 mV, with minimal change over time, indicating that the surface electrical properties and electrostatic repulsion of the particles were not significantly weakened during heat treatment. Example 19 did not exhibit significant aggregation, co-agglomeration, or thermally induced instability within the heat treatment window of 25–70℃ for 60 min, demonstrating good thermal stability and meeting the heat resistance requirements during subsequent processing and storage.

[0098] Experiment 9: pH Stability Evaluation The aqueous dispersion of nanoparticles obtained in Example 19 was used to adjust the pH of the sample to 2, 3, 5, 7 and 8 with HCl or NaOH, respectively. After equilibration under each pH condition, the hydrated particle size, dispersion index (PdI) and zeta potential of the sample were measured at 25°C, and the changes under different pH conditions were recorded to evaluate the pH stability of the nanoparticle dispersion.

[0099] See results Figure 15 In Example 19, the particle size remained relatively stable within a pH range of 2–8, consistently around 155–165 nm, without significant increase or abrupt changes under acidic / alkaline conditions. The PdI remained at a low level (approximately 0.15–0.20) with limited variation with pH, ​​indicating a consistently concentrated particle distribution without significant agglomeration or stratification instability. The zeta potential showed a significant pH response: the absolute value was small at pH 2–3, approaching neutrality. However, as the pH rose to 5–8, the potential rapidly became more negative and gradually increased. These results demonstrate that Example 19 exhibits good wide pH adaptability, with its particle size and dispersibility primarily maintained by the steric hindrance / interfacial structure of the particle surface layer. Furthermore, under neutral and weakly alkaline conditions, the enhanced negative potential leads to stronger electrostatic repulsion, further improving dispersion stability.

[0100] Experimental Example 10: Evaluation of Ionic Strength Stability The aqueous dispersion of nanoparticles obtained in Example 19 was used. After adjusting the pH of the sample to 7.0, NaCl was added to adjust the ionic strength of the system, resulting in final NaCl concentrations of 0, 50, 100, 150, and 200 mM. After equilibration under each ionic strength condition, the hydrated particle size, dispersion index (PdI), and zeta potential of the sample were measured at 25°C, and the changes under different ionic strength conditions were recorded to evaluate the ionic strength stability of the nanoparticle dispersion.

[0101] As shown in the figure, in Example 19, the particle size remained relatively stable within the NaCl range of 0–200 mM, generally between 155 and 165 nm, and the PdI also remained at a low level, indicating that the sample was not prone to significant agglomeration or widening of the particle size distribution over a wide range of ionic strengths. In contrast, the zeta potential decreased with increasing salt concentration, from approximately -39 mV at 0 mM to -7 to -12 mV after adding 50–200 mM NaCl. Despite the significant decrease in apparent potential, the particle size and PdI remained stable, indicating that the system could maintain good dispersion at high salinity, demonstrating good salt tolerance and suitability for practical applications.

Claims

1. A food-grade anisotropic nanoparticle having a dual domain partition structure, characterized in that, The nanoparticles comprise shellac and ethyl cellulose, the shellac phase and the ethyl cellulose phase are in a spatially distinguishable distribution in the same particle and form a biregion partition structure, so that the nanoparticles are anisotropic.

2. The food-grade anisotropic nanoparticle of claim 1, wherein, The nanoparticles have a dumbbell shape or a snowman shape.

3. A method of making the food-grade anisotropic nanoparticles of claim 1 or 2, characterized in that, The method comprises the following steps: (1) a certain amount of shellac and ethyl cellulose are weighed and added into an organic solvent, and stirred at 600 rpm until completely dissolved to obtain a clear organic phase solution; (2) a certain amount of polysorbate 80 is dissolved in deionized water, and stirred at 600 rpm until completely dissolved to obtain an aqueous phase solution; (3) the organic phase solution of step (1) and the aqueous phase solution of step (2) are respectively filtered through a 0.45 μm filter membrane to remove insoluble substances; (4) under the vortex state of the aqueous phase solution of step (2), the organic phase solution of step (1) is quickly added into the aqueous phase solution through a syringe, so that the shellac and the ethyl cellulose are co-precipitated and phase-separated in the particle to form a Janus nanoparticle dispersion liquid with a biregion partition structure; (5) the Janus nanoparticle dispersion liquid with a biregion partition structure of step (4) is subjected to ultrafiltration purification, and a molecular weight cut-off MWCO of 100 kDa is used for the ultrafiltration membrane to remove residual organic solvents and free polysorbate 80, so as to obtain a Janus nanoparticle aqueous dispersion liquid with a biregion partition structure.

4. The method of claim 3, wherein, The mass ratio of the shellac to the ethyl cellulose is 0.5:1-2:

1.

5. The method according to claim 3 or 4, characterized in that, The organic solvent is ethanol.

6. The method according to any one of claims 3 to 5, characterized in that, The concentration of the polysorbate 80 in the aqueous phase solution is 0.01%-1.0% (w / v).

7. The method according to any one of claims 3 to 6, characterized in that, The concentration of the shellac in the organic phase solution is 2-30 mg / mL, and the concentration of the ethyl cellulose is 2-30 mg / mL.

8. The method according to any one of claims 3 to 7, characterized in that, The volume ratio of the aqueous phase solution to the organic phase solution in step (4) is 5:1-20:

1.

9. The method according to any one of claims 3 to 8, characterized in that, In step (4), the shear mixing is vortex mixing, the vortex rotation speed is 1000-3500 rpm; the quick adding is a syringe quick injection mode, and the mixing time is 5-120 s; the organic phase solution and the aqueous phase solution are subjected to temperature equilibrium treatment before being mixed in step (4), and the temperature is 25-70℃.

10. Application of the food-grade anisotropic nanoparticles prepared by the method of any one of the preceding claims in functional factor delivery.

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