Oil-in-water microspheres for wrapping cosmetic active matters

Abstract

The invention discloses an oil-in-water (o / w) microsphere for wrapping cosmetic active matters. In the microspheres, the water phase forms a shell layer to wrap the inner oil phase, the core composition of the inner oil phase comprises an oil-soluble active matter or a dispersible matter, the shell layer water phase can provide good protection and isolation effects, and meanwhile the good skin feeling needed by cosmetic application is met. After the active substances are wrapped by the wrapping technology, the unstable active substances can be isolated from external water, air, ultraviolet rays, other incompatible substances and the like, and oxidation, hydrolysis and other reactions are reduced, so that the stability of the active substances is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of cosmetics and application technology, and specifically relates to an oil-in-water (o / w) microsphere for encapsulating active ingredients in cosmetics. Background Technology

[0002] Oil-soluble active ingredients are very common in cosmetics, and many of them are highly sensitive, such as retinol, coenzyme Q10, and most antioxidants. These active ingredients face two major enemies: oxygen and light. They are prone to oxidation, decomposition, isomerization, and other chemical reactions, leading to inactivation. Take retinol as an example. Retinol is widely recognized as one of the most effective anti-aging and skin regeneration ingredients. However, retinol is extremely sensitive to light, heat, and oxygen, and is easily degraded and oxidized in conventional formulations. While traditional cream formulations provide basic protection, they fall far short of ideal results. This not only leads to product degradation within its shelf life, yellowing, and altered odor, but also results in consumers using far less than the labeled dosage, significantly reducing effectiveness. Therefore, developing an innovative protection system that can address the issue of unstable oil-soluble active ingredients has become crucial.

[0003] Microfluidics is a technology that uses immiscible fluids to generate and manipulate monodisperse microdroplets within microchannels. It offers advantages such as small droplet volume, easily controllable particle size, and high monodispersity. Based on an oil-in-water (O / W) structure, microfluidics is a necessary choice and a key technological breakthrough to address this industry pain point. However, the production of cosmetic microcapsules using microfluidics is still in its early stages, unable to simultaneously achieve stability and user experience. Compared to micron or nanometer-scale microcapsules, the inability to balance stability and user experience is increasingly prominent in millimeter-scale microcapsules. To achieve strong stability, microspheres are often prepared using single or rigid wall materials (such as certain brittle polymers), which may result in a noticeable "granular," "friction-like," or even "gritty" feel during application, or a stiff, difficult-to-break texture. Furthermore, the microspheres leave behind a lot of debris and sticky substances after they break, making it difficult to spread evenly and resulting in a noticeable gritty and film-like feel. This leads to a poor user experience and limits their practical application, resulting in very few millimeter-sized water-in-oil microsphere products for cosmetics being launched.

[0004] CN 117064767 A discloses a water-in-oil composition with excellent skin feel, a topical skin preparation, and a method for preparing the same; it includes at least: water as a medium; optically isotropic oil particles; and optically anisotropic oil crystals; wherein both the oil crystals and oil particles are distributed in the water. Compared to conventional water-in-oil systems, the solid oil in this patent application exists in the aqueous phase in crystalline form (physical morphology is plate-like or layered crystals, rather than emulsified spherical shapes), thus significantly improving spreadability and refreshing feel, and eliminating any sense of obstruction. Simultaneously, the solid oil can form a closed film on the skin surface, providing excellent moisturizing properties. However, this water-in-oil composition is an open emulsion system and does not belong to microcapsules; naturally, it fails to provide guidance on how to balance the stability and user experience of millimeter-level microcapsules. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art: to provide a water-in-oil (o / w) capsule for encapsulating (unstable, oil-soluble) oil-soluble active ingredients. This ensures the stability of the active ingredients while also considering the user experience of the microbeads. In the context of this patent application, "active ingredient" refers to the "efficacy ingredient" or "functional ingredient" in cosmetics, such as moisturizing and barrier repair agents: ceramides; whitening and spot-removing agents: ascorbate palmitate, glycyrrhizin, phenylethyl resorcinol; anti-aging agents: retinol, retinyl palmitate, retinaldehyde, peptides (such as acetyl hexapeptide-8, palmitoyl tripeptide-5, cyclic peptides), coenzyme Q10; sunscreens: octocrylene, ethylhexyl triazine. Using microfluidic technology, the cosmetic active ingredients are encapsulated in an oily core, with an outer aqueous shell, which acts as a "protective chamber." By encapsulating the active ingredient using the encapsulation technology of this invention, unstable active substances can be isolated from external air, sunlight, water, and other incompatible substances, significantly delaying their degradation process and thus greatly improving the stability of the active ingredient. Results show that the encapsulation technology of this invention can improve the stability of retinol several times, ensuring that the product maintains high activity throughout its entire life cycle; simultaneously, it also provides a good skin feel, as assessed by evaluation of cracking / melting sensation, spreadability, skin absorption, skin softness, and residual film; the overall skin feel score is ≥ 4.0.

[0006] The objective of this invention is achieved through the following technical solutions:

[0007] <First Aspect> This invention provides an oil-in-water microsphere for encapsulating active ingredients. In the microsphere, an aqueous phase forms a shell encapsulating an inner oil phase, the core component of which comprises oil-soluble or dispersible active substances. The outer diameter of the microsphere is 0.2-4 mm; the storage modulus G' of the microsphere is 0.5 kPa ≤ G' ≤ 20 kPa. The aqueous shell in the microsphere of this invention provides isolation while meeting the skin feel indicators required for cosmetic applications. The isolation function includes isolating some water, air, ultraviolet light, and other incompatible substances, thereby protecting the unstable active substances within the oil phase. Skin feel indicators are used to evaluate the skin feel of cosmetics, including spreadability, smoothness, and stickiness. Specifically, trained sensory evaluators can assess the feel of the microspheres on the skin, evaluating factors such as cracking / melting sensation, spreadability, skin absorption, skin softness, and residual film. A comprehensive skin feel score ≥ 4.0 is considered a good skin feel.

[0008] As one implementation scheme, the air permeability of the aqueous shell in the microspheres is less than 0.08 cm⁻¹. 3 / day.

[0009] As one implementation scheme, in o / w microspheres, the inner diameter is 0.1-3 mm; the inner diameter / outer diameter ratio is 0.1-0.9.

[0010] As one implementation method, the o / w microspheres underwent a 3-month stability test at 45ºC, and the internal oil phase loss rate was less than or equal to 20%. Loss description: Includes both physical loss and deterioration loss.

[0011] As one embodiment, the aqueous phase comprises a gelling agent and an optional crosslinking agent, wherein the gelling agent comprises 0.1-50% and the crosslinking agent comprises 0-5% by mass percentage in the aqueous phase. Specifically, the gelling agent percentage can be 0.5%-1%, 1%-5%, 5%-10%, 10%-15%, 15%-20%, 20%-25%, 25%-30%, 30%-35%, 35%-40%, 45%-50%, etc. The crosslinking agent percentage can be 0.1%-0.4%, 0.4%-0.8%, 0.8%-1.2%, 1%-1.5%, 1.5%-2.5%, 2.5%-3.5%, 3.5%-4%, 4%-4.5%, 4.5%-5%.

[0012] As one embodiment, the gelling agent includes at least one of cellulose gum, agar, gelatin, chitosan, gellan gum, carrageenan, guar gum, gum arabic, konjac gum, sodium alginate, locust bean gum, sodium hyaluronate, xanthan gum, sclerotium gum, magnesium aluminum silicate, bentonite, carbomer, and acrylic polymers.

[0013] As one embodiment, the crosslinking agent includes dipotassium EDTA or calcium EDTA.

[0014] As a specific implementation example, the aqueous phase comprises 0.6%-3.1% κ-carrageenan, 0.1%-0.5% konjac gum, and 1.2%-1.5% crosslinking agent by mass percentage. Preferably, the aqueous phase comprises 0.6%-2.2% κ-carrageenan, 0.1%-0.3% konjac gum, and 1.5% crosslinking agent; in this case, the storage modulus G' of the microspheres is: 0.5 kPa ≤ G' ≤ 11 kPa.

[0015] As another specific embodiment, the aqueous phase comprises 0.6%-3% agar and 0.1%-0.5% xanthan gum by mass percentage. Preferably, the aqueous phase comprises 0.6%-2% agar and 0.1%-0.4% xanthan gum; in this case, the storage modulus G' of the microspheres is: 0.5kPa≤G'≤11kPa.

[0016] As another specific implementation example, the aqueous phase comprises 0.4%-2.2% sodium alginate and 0.1%-0.25% agar, and 1.2%-1.5% crosslinking agent, by mass percentage. Preferably, the aqueous phase comprises 0.4%-1.5% sodium alginate and 0.1%-0.2% agar, and 1.2% crosslinking agent; in this case, the storage modulus G' of the microspheres is: 0.5kPa≤G'≤11kPa.

[0017] As one implementation, the core component of the internal oil phase further includes grease, which accounts for 0.5-99.5% of the total mass of the internal oil phase. This percentage can be 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 98%, 99%, etc.

[0018] As one embodiment, the oil comprises at least one of the following: triglyceride (ethylhexanoate), caprylic / capric triglyceride, coconut oil-caprylate / capric acid ester, isononyl isononanoate, cetyl ethylhexanoate, candelilla wax, rice bran wax, palm wax, ceresin, cetyl wax, lignite wax, microcrystalline wax, myristyl myristate, jojoba wax, beeswax, lanolin, jojoba oil, squalane, vegetable oil, and silicone oil.

[0019] As one embodiment, the oil-soluble active ingredient includes at least one of retinol and its derivatives, vitamin C derivatives, vitamin E and its derivatives, coenzyme Q10, unsaturated plant extracts, sunscreens, and essential oils.

[0020] As one embodiment, the dispersible material includes at least one of zinc oxide, titanium dioxide, iron oxide, pearlite, and mica.

[0021] As one implementation, the core components of the aqueous shell may also include emulsifiers, preservatives, and colorants.

[0022] As one embodiment, the emulsifier comprises a water-soluble nonionic emulsifier, anionic emulsifier, or amphoteric emulsifier. As a preferred embodiment, the emulsifier is a water-soluble nonionic emulsifier. The nonionic emulsifier includes Tween 20, Tween 40, Tween 60, Tween 80, methyl glucoside derivatives, cetearyl alcohol ether, polyvinyl alcohol, poloxamer, and silica.

[0023] As one implementation, the preservative includes at least one of phenoxyethanol, ethylhexylglycerin, p-hydroxyacetophenone, octyl glycol, pentylene glycol, and parabens.

[0024] As one implementation, the colorant includes water-soluble natural pigments and synthetic pigments; wherein the natural pigment is at least one of beet red, sodium copper chlorophyllin, and gardenia blue / yellow; and the synthetic pigment is at least one of tartrazine, sunset yellow, carmine, allura red, brilliant blue, and caramel color.

[0025] As one implementation scheme, the core components of the inner oil phase include greases, waxes, oil phase thickeners, emulsifiers, colorants, and oil-soluble active ingredients.

[0026] As one implementation, the oil-phase thickener includes thickeners dissolved in oil and solid powder thickeners insoluble in oil.

[0027] As one implementation, the thickener dissolved in the oil includes one or more of the following: dextrin palmitate, castor oil / IPDI copolymer, hydrogenated castor oil / sebacic acid copolymer, dibutylethylhexanoyl glutamine, dibutyllauroyl glutamine, hydrogenated styrene / butadiene copolymer, and silicon elastomer.

[0028] As one implementation, the oil-insoluble solid powder oil phase thickener includes at least one of silica, hydropyrite, montmorillonite, bentonite, clay, and plant cellulose.

[0029] As one implementation method, the emulsifier includes nonionic emulsifiers, anionic emulsifiers, or zwitterionic emulsifiers.

[0030] As one embodiment, the nonionic emulsifier includes at least one of glycerol ester emulsifiers, polyglycerol emulsifiers, and glycoside emulsifiers.

[0031] As one implementation, the colorant includes pigments, lakes, or inorganic pigments. The pigments include natural pigments and synthetic pigments.

[0032] As one implementation method, the natural pigments include at least one of carotene, lutein, chlorophyll, astaxanthin, lycopene, comfrey oil, and turmeric.

[0033] As one implementation, the synthetic pigment or lake includes at least one of Red 4, Blue 1, Yellow 5, Yellow 6, and Green 6.

[0034] As one implementation scheme, the inorganic pigments include at least one of ultramarine, chrome green, manganese violet, titanium dioxide, mica, carbon black, and iron oxide.

[0035] <Second aspect> This invention provides a method for preparing oil-in-water microspheres for encapsulating active ingredients. The method employs a continuous flow, same-order shear microfluidic process and includes the following steps: S1. Inject the aqueous phase, external oil phase, and internal oil phase into the microchannel of the microfluidic device, respectively. The external oil phase shears the aqueous phase flowing in the same direction into external droplets, and after the external droplets are generated, they flow out into the receiving tube. S2. The internal phase oil is sheared into the external droplets by the co-current flowing aqueous phase, forming O / W droplets containing active substances, which are then collected and cooled.

[0036] As one implementation scheme, an aqueous phase, an outer oil phase, and an inner oil phase are injected into microchannels using a pneumatic pump. The inner diameter of the microchannel (where the inner core is formed) is 50–500 μm, and the outer diameter (where the outer droplet is formed) is 900–2000 μm. The solution flow rate is controlled by adjusting the parameters of the pressure pump: the pressure corresponding to the aqueous phase is 8–13 kPa, the pressure corresponding to the outer oil phase is 10–18 kPa, and the pressure corresponding to the inner oil phase is 2–8 kPa.

[0037] As one implementation, the outer oil phase comprises 0.1%-1% EM 90 and 99%-99.9% soybean oil.

[0038] As another implementation, the outer oil phase comprises 0.1%-1% EM 90 and 99%-99.9% sunflower seed oil.

[0039] As one implementation, the receiving phase comprises 0.5%-2% acetic acid and 98%-99.5% soybean oil.

[0040] As another implementation, the receiving phase comprises 0.5%-2% acetic acid and 98%-99.5% sunflower seed oil.

[0041] Compared with the prior art, the present invention has the following beneficial effects: 1) The microcapsules generated by the microfluidic technology of the present invention can encapsulate and retain various complex oil-soluble active substances for a long time, such as vitamin A and its derivatives (e.g., retinol), carotenoids (e.g., astaxanthin), essential oils containing active ingredients such as terpenes and aromatic hydrocarbons (e.g., citrus essential oils), some flavonoids, polyphenols and other natural antioxidants (e.g., resveratrol), plant oils, etc.

[0042] 2) By selecting or combining shell materials with excellent skin affinity and good flexibility, this invention can control the elasticity and hardness of the shell material, resulting in millimeter-sized microcapsules with excellent skin feel: they can be easily and evenly spread on the skin surface, and after the active ingredients are delivered, they can be quietly dissipated by sebum, moisture or external friction, leaving no residue or film-forming feeling, giving users a refreshing experience.

[0043] 3) The microcapsules obtained by this invention have regular morphology, uniform wall thickness, and consistent strength distribution, resulting in a high encapsulation rate, eliminating core leakage, and ensuring the product remains intact.

[0044] 4) This invention discovers that by controlling the shell material of the microspheres, the air permeability of the aqueous phase shell in the microspheres can be made to meet the requirement of "less than 0.08 cm³". 3 The microspheres' energy storage modulus G' is 0.5kPa≤G'≤20kPa, which simultaneously resolves the critical contradiction between product stability and end-user skin feel. Specifically, this elastic design ensures that the microspheres can resist external stress during production, storage, and transportation, maintaining structural integrity and content stability. Simultaneously, its elastic critical point matches the typical external force during use, allowing the microspheres to break down in a controlled and immediate manner during application, precisely triggering content release, texture changes, or alterations in friction, directly optimizing the final skin feel. Attached Figure Description

[0045] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings / tables: Figure 1 This is a schematic diagram of the O / W microsphere preparation process of the present invention; Figure 2 This is a diagram of the apparatus for preparing the O / W microspheres of the present invention; Figure 3 The image shows the appearance of the O / W microbeads encapsulating retinol generated in Example 1; Figure 4 This is an image of the O / W microspheres obtained by cooling in Example 1; Figure 5 This is a magnified microscopic image of the O / W microspheres obtained by cooling in Example 1. Detailed Implementation

[0046] This invention provides an oil-in-water (o / w) microsphere for encapsulating oil-soluble active ingredients. The microsphere has a core-shell structure, where the core is the oil phase and the shell is the aqueous phase. The outer diameter of the microsphere is 0.2-4 mm, the inner diameter is 0.1-3 mm, and the ratio of inner diameter to outer diameter is 0.1-0.9. The core component of the aqueous shell layer includes a gelling agent. The gelling agent includes at least one of the following: cellulose gum, agar, gelatin, chitosan, gellan gum, carrageenan, guar gum, gum arabic, konjac gum, sodium alginate, locust bean gum, sodium hyaluronate, xanthan gum, sclerotium gum, magnesium aluminum silicate, bentonite, carbomer, and acrylic polymers. The gelling agent comprises 0.1-50% by mass in the aqueous phase. Optionally, a crosslinking agent may also be included, comprising 0-5% by mass in the aqueous phase.

[0047] The aqueous phase, acting as the shell of the microspheres, serves to isolate some water, air, ultraviolet radiation, and other incompatible substances, thereby protecting the active cosmetic ingredients within the shell. To effectively protect these active ingredients, the aqueous shell possesses the following characteristics: 1. Raw materials that can be used in cosmetics, 2. Chemical inertness: It does not react chemically with the core material and does not affect the basic properties of the core material. 3. It can solidify and has a certain strength after processing, and it has film-forming properties; 4. After curing, it exhibits good density and heat resistance, with a melting point greater than 50 ºC. 5. It also possesses a certain degree of strength; the beads produced have the following characteristics: Sufficient strength: The shell must be able to resist external pressure, friction, and impact to prevent the microspheres from breaking during processing or transportation. Good elasticity: It should not easily crack under deformation and should elastically protect the core material. Strength and elasticity need to be balanced, similar to an eggshell; it cannot be too brittle to break easily, nor too soft to be flattened. Through extensive creative work, this invention has determined that the storage modulus G' of the microspheres is 0.5 kPa ≤ G' ≤ 20 kPa, which provides sufficient and suitable strength and good elasticity.

[0048] Further investigation into air permeability revealed that the shell exhibited significantly reduced permeability to substances such as oxygen and water vapor, with a permeability parameter below 0.08 cm⁻¹. 3 / day. The microspheres consist of a continuous, dense shell, formed by a low-permeability material, which physically blocks the penetration of external substances.

[0049] This invention also discloses a method for preparing the microcapsules. The O / W microspheres of this invention are prepared using microfluidic technology, employing a capillary glass tube assembly method to fabricate a microfluidic chip, achieved through a one-step emulsification method, such as... Figure 1 Three mobile phases were selected: the inner phase IP (core material, i.e., the oil phase containing active ingredients), the intermediate phase MP (shell material, aqueous phase), and the outer phase OP (soybean oil containing 0.5% (w / w) EM90). Each phase was pumped into a capillary glass tube from its corresponding inlet using a syringe pump, such as... Figure 2 The first step involves the outer phase OP flowing in through injection needle #3. Upon encountering the intermediate phase MP (aqueous phase) flowing in through injection needle #2, it is sheared into outer droplets. These outer droplets then flow out through the receiving tube. The second step involves the inner phase IP flowing in through injection needle #1. Upon encountering the co-flowing outer droplets, the inner phase IP is sheared into the outer droplets, forming a double droplet with a shell and core. This droplet is then collected and cooled through the collecting tube. The specific presentation is continuous flow with simultaneous shearing.

[0050] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0051] Example 1 This embodiment relates to the preparation of O / W microcapsules with κ-carrageenan and konjac gum as the main wall materials: (1) Preparation of inner oil phase: Weigh 2 parts of retinol and 98 parts of caprylic / capric triglyceride, mix them evenly to obtain oil phase inner core A; (2) Preparation of the intermediate phase: Weigh 1.5 parts of κ-carrageenan and 0.3 parts of konjac gum and add them to water (the amount of water is to be made up to 100 parts of the intermediate phase). Heat at 85°C to dissolve. Then add 0.5 parts of EDTA dipotassium (EDTA dipotassium) to dissolve. Homogenize for 5 min using a homogenizer to prepare the aqueous shell B. (3) Preparation of external oil phase: Weigh 0.5 parts of EM 90 and 99.5 parts of soybean oil and mix them evenly.

[0052] (4) Preparation of receiving phase: Weigh 1 part acetic acid and 99 parts soybean oil and mix them evenly.

[0053] (5) For microfluidic chips made of capillary glass tubes, the glass tubes for generating inner droplets are ground to a size of 220 μm, and the glass tubes for generating outer droplets are 1800 μm. The capillary glass tubes for generating inner droplets need to be locally modified by soaking in octadecyltrimethoxysilane for 3 to 5 minutes.

[0054] (6) Inject the three-phase solution into the material bottle, raise the chamber temperature to 85°C until the intermediate phase is completely melted and the external phase preheating temperature is stable. Inject the three-phase solution into the microfluidic chip using a pneumatic pump, and control the solution flow rate by adjusting the parameters of the pressure pump. Adjust the internal phase solution to 6 kPa, the intermediate phase to 10 kPa, and the external phase to 15 kPa until O / W droplets with oil phase are generated.

[0055] (7) The receiving phase receives the generated double emulsion droplets. Acetic acid diffuses into the droplets, lowering the pH and causing EDTA dipotassium to release potassium ions. The potassium ions crosslink with κ-carrageenan and konjac gum, and the droplets gradually gel, as shown in the figure. Figure 3 As shown; the outer diameter is ~1400um, the inner diameter is ~1000um, and it forms a spherical solid after cooling, as... Figure 4 As shown.

[0056] (8) Filter to remove most of the oil. Wash the filtered beads with deionized water, repeating at least 3 times to ensure complete removal of oil. The encapsulation efficiency of the microcapsules prepared above was investigated. The results showed that the encapsulation efficiency of the microcapsules prepared in Example 1 was 97.28%, which has a good encapsulation effect.

[0057] (10) Take a microbead sample onto a glass slide, add oil to disperse it, and observe it under an Olympus SZX16 optical microscope (1× objective lens). The microbeads are clearly spherical with distinct core-shell boundaries: a clear and continuous annular boundary exists between the central and peripheral regions; this boundary is round, closed, and without breaks or gaps, as shown in the image. Figure 5 As shown, this confirms that a complete core-shell structure has been formed inside the microspheres.

[0058] (11) Energy storage modulus Storage modulus G' is the modulus characterizing the energy stored and elastically released by a material during dynamic deformation. It directly quantifies the material's solid-state properties, structural strength, and elastic response. A higher storage modulus (G') results in a gel that feels firmer, more supportive, and less prone to collapse when touched by skin. G' is a major contributor to the spreading resistance (initial shear stress), which is related to "spreading resistance." A higher G' typically requires greater force to spread, resulting in a "thicker" and "difficult-to-spread" feel. The storage modulus (G') of the shell sample from Example 1 was obtained through small-amplitude oscillating shear (SAOS) testing to evaluate its structural elasticity and spreadability. The testing steps are as follows: ① Instruments and conditions Instrument: TA Discovery HR rotational rheometer (TRIOS software) Geometry: 60 mm parallel plate, 25°C temperature control Mode: Controlled Strain Oscillation Test ② Sample preparation Clean the parallel plates.

[0059] Place the sample (cut into approximately 60mm round slices) in the center of the lower plate.

[0060] Set a gap close to the original thickness of the sample and apply light pressure (normal force < 0.3 N).

[0061] Let it stand still for 1-2 minutes to reach equilibrium.

[0062] ③ Test steps A: Amplitude scan (to determine LVR) Fixed frequency: 10 rad / s Strain range: 0.01% → 1%, LVR determination: The relative deviation between two points G' in the platform area is ≤10%; B: Frequency scan (performance comparison) Mode: Oscillation Frequency Fixed strain: Select a stable strain value within the LVR platform (the same for all samples). Frequency range: 0.1 – 10 Hz Record: G ′( f ),

[0063] ④ Data Analysis The energy storage modulus in this embodiment is obtained by extracting the index at 1 Hz from the frequency scan data: .

[0064] For different shell materials, the energy storage modulus at a uniform frequency of 1 Hz is extracted: As a key comparison indicator.

[0065] (12) Stability comparison test: Stability comparison between microencapsulated and free retinol; Sample 1: 0.2 parts of retinol were solubilized in water using Tween 20.

[0066] Sample 2: The microencapsulated retinol (microsphere content 27.44%) prepared in Example 1 was dispersed in water to ensure that the final retinol content was also 0.2%.

[0067] Test conditions: All samples were placed in transparent glass bottles and stored in sunlight to simulate and accelerate the photo- and oxygen-degradation process.

[0068] Detection method: The retinol content in the samples was determined by high performance liquid chromatography (HPLC) with external standard method on days 0, 7, 14, and 30. The results are shown in Table 2. Table 2

[0069] The experimental data above show that, after 30 days of storage under the same conditions, the retinol activity retention rate of the present invention is approximately 90 times that of the comparative example. The retinol in the comparative example was almost completely degraded, while the retinol of the present invention retained the vast majority of its activity. The experimental results demonstrate that the microencapsulated retinol composition provided by the present invention exhibits unexpectedly superior stability in resisting light and oxygen degradation compared to traditional surfactant solubilization systems. Through a specific microencapsulation process, retinol is effectively encapsulated within a dense wall material, maintaining an extremely high activity retention rate even under harsh storage conditions. This provides an extremely effective and reliable solution for improving the stability of retinol, overcoming the technical bottleneck of retinol's easy inactivation and short shelf life in cosmetic formulations.

[0070] Example 2-16 Examples 2-16 differ from Example 1 in their shell aqueous phase formulation; however, the oil phase and receiver phase formulations are identical, with the inner oil phase consisting of 2 parts retinol and 98 parts caprylic / capric triglycerides. The same microcapsule preparation method is used, as detailed in Table 3.

[0071] Table 3

[0072] Examples 17-33 Examples 17-22 use the same aqueous gelling agent as Example 1, differing only in the amount added; the oil phase and receiving phase formulations are identical, with the inner oil phase consisting of 2 parts retinol and 98 parts caprylic / capric triglycerides, and the same microcapsule preparation method is used; Examples 23-28 use the same aqueous gelling agent as Example 12, differing only in the amount added; the oil phase and receiving phase formulations are identical, with the inner oil phase consisting of 2 parts retinol and 98 parts caprylic / capric triglycerides, and the same microcapsule preparation method is used; Examples 29-33 use the same aqueous gelling agent as Example 13, differing only in the amount added; the oil phase and receiving phase formulations are identical, with the inner oil phase consisting of 2 parts retinol and 98 parts caprylic / capric triglycerides, and the same microcapsule preparation method is used; see Table 4 for details.

[0073] Table 4

[0074] The comparative data above show that, when using the same aqueous gelling agent, reducing its amount results in softer microspheres with a lower storage modulus under the same conditions; conversely, increasing its amount results in harder microspheres with a higher storage modulus under the same conditions. Examples 17, 23, and 29, due to their excessively soft microspheres, could not be stably stored and were not included in subsequent skin feel evaluation tests. Considering both skin feel and bead storage stability, a storage modulus falling within the range of 0.5 kPa to 20 kPa meets the requirements for cosmetic applications.

[0075] Skin feel assessment test example Based on the user experience of the microbeads during application, after application, and after absorption, each of the five performance aspects was scored (1-5 points), and the dynamic changes in skin feel were monitored throughout the entire process from "contact with the skin" to "release of active ingredients".

[0076] 1. Sample preparation: Take a number of microbead samples obtained in Examples 1-16 and Examples 17-33 (except for 17, 23, and 29) and place them in an equilibration environment of 25℃ ± 1℃ and 50% ± 5% relative humidity for 2 hours.

[0077] 2. Evaluation Indicators and Scoring Standards: Thirteen trained sensory evaluators conducted a blind evaluation of the skin feel of the microbeads. The evaluation items and scoring standards are shown in Table 5 below: Table 5

[0078] Note: The evaluation area is the inner forearm. The amount of each microbead sample is 0.1g. Gently massage for 30 seconds and let it stand for 2 minutes before scoring.

[0079] 3. Data processing: The average value of each indicator is taken as the final score for that indicator; the overall average score is calculated as the "comprehensive skin feel score".

[0080] 4. Results Recording and Judgment: A comprehensive skin feel score ≥ 4.0 is considered "good skin feel"; 3.0–3.9 is "moderate"; < 3.0 is "poor skin feel".

[0081] 5. Skin feel assessment conclusion Following the "Sensory Performance Test Example" method described above, 13 evaluators scored the microbeads obtained in Examples 1-16 and Examples 17-33 (except for 17, 23, and 29). The results are shown in Table 6 below: Table 6

[0082] Examples 1-16 all had a comprehensive skin feel score ≥ 4.0, and were considered to have a "good skin feel". Examples 17, 23, and 29 had too low a storage modulus, resulting in poor storage and transportation stability, so no skin feel evaluation was performed. Comparative Examples 2, 3, 4, 5, 8, 9, 10, 11, 14, 15, and 16 all had a comprehensive skin feel score ≥ 4.0, and were considered to have a "good skin feel". Example 33 had a comprehensive skin feel score between 3.0 and 3.9, and was considered to have a "moderate skin feel". Examples 22 and 28 had a comprehensive skin feel score < 3.0, and were considered to have a "poor skin feel". When the storage modulus G' is 0.5 kPa ≤ G' ≤ 20 kPa, the microspheres are stable in storage and have a good skin feel. A storage modulus > 20 kPa indicates that the microsphere structure is too tough, which directly leads to a poor skin feel. The most prominent problem is that the microbeads are difficult to crush or break on the skin, which is reflected in the low scores of the two evaluation indicators of cracking / melting sensation and spreadability.

[0083] Stability test of encapsulated active ingredients Examples 4, 12, and 13 were selected to encapsulate different active ingredients, and corresponding stability tests were performed. Experimental method: Retinol, ascorbate palmitate and coenzyme Q10 (microsphere content 27.44%) were encapsulated in Examples 4, 12 and 13 respectively and dispersed in water.

[0084] Test conditions: All samples were placed in transparent glass bottles and stored in sunlight to simulate and accelerate the photo- and oxygen-degradation process.

[0085] Detection method: The content of active ingredients in the samples was determined by high performance liquid chromatography (HPLC) with external standard method on days 0, 7, 14, and 30. The results are shown in Table 7. Table 7

[0086] Similar to the test results in Example 1, the microsphere aqueous phase formed a dense hydrogel shell, which possesses naturally low air permeability (meeting the requirement that the air permeability of the aqueous phase shell is less than 0.08 cm). 3 ( / day) can isolate oxygen in the environment, thereby preventing oxygen from penetrating the hydrogel shell and entering the inner oil phase, which would cause the active ingredients to become inactive.

[0087] In summary, the water-in-oil (o / w) microspheres provided by this invention for encapsulating active ingredients in cosmetics, through the design and compounding of the aqueous gelling agent, allow the shell of the microspheres to isolate some water, air, ultraviolet rays, and other incompatible substances, effectively maintaining the activity and stability of the core material. Simultaneously, these microspheres exhibit a pleasant user experience, providing an effective and reliable solution to the stability issues of active ingredients such as retinol. Furthermore, they resolve the key contradiction between the stability of millimeter-scale microcapsule products and the final skin feel, demonstrating broad application prospects in the cosmetics field.

[0088] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A water-in-oil microsphere for encapsulating active ingredients, characterized in that, In the microspheres, an aqueous phase forms a shell that encapsulates an inner oil phase, the core components of which include oil-soluble active substances or dispersible substances; the outer diameter of the microspheres is 0.2-4 mm; the storage modulus G' of the microspheres is 0.5 kPa ≤ G' ≤ 20 kPa.

2. The oil-in-water microspheres for encapsulating active ingredients according to claim 1, characterized in that, The microspheres have an inner diameter of 0.1-3 mm and an inner diameter / outer diameter ratio of 0.1-0.9:

1.

3. The oil-in-water microspheres for encapsulating active ingredients according to claim 1, characterized in that, The aqueous phase comprises a gelling agent and an optional crosslinking agent, wherein the gelling agent accounts for 0.1-50% and the crosslinking agent accounts for 0-5% by mass percentage in the aqueous phase.

4. The oil-in-water microspheres for encapsulating active ingredients according to claim 3, characterized in that, The gelling agent includes at least one of cellulose gum, agar, gelatin, chitosan, gellan gum, carrageenan, guar gum, gum arabic, konjac gum, sodium alginate, locust bean gum, sodium hyaluronate, xanthan gum, sclerotium gum, magnesium aluminum silicate, bentonite, carbomer, and acrylic polymers; the crosslinking agent includes dipotassium EDTA or calcium EDTA.

5. The oil-in-water microspheres for encapsulating active ingredients according to claim 1, characterized in that, The core component of the internal oil phase also includes grease, which accounts for 0.5-99.5% of the total mass of the internal oil phase.

6. The oil-in-water microspheres for encapsulating active ingredients according to claim 5, characterized in that, The oils and fats include at least one of the following: triglycerides (ethylhexanoate), caprylic / capric triglycerides, coconut oil-caprylate / capric acid ester, isononyl isononanoate, cetyl ethylhexanoate, candelilla wax, rice bran wax, palm wax, ceresin, whale wax, lignite wax, microcrystalline wax, myristyl myristate, jojoba wax, beeswax, lanolin, jojoba oil, squalane, vegetable oils, and silicone oils.

7. The oil-in-water microspheres for encapsulating active ingredients according to claim 1, characterized in that, The oil-soluble active ingredients include at least one of retinol and its derivatives, vitamin C derivatives, vitamin E and its derivatives, coenzyme Q10, unsaturated plant extracts, sunscreens, and essential oils.

8. The oil-in-water microspheres for encapsulating active ingredients according to claim 1, characterized in that, The dispersible material includes at least one of zinc oxide, titanium dioxide, iron oxide, pearlite, and mica.

9. A method for preparing oil-in-water microspheres for encapsulating active ingredients according to any one of claims 1-8, characterized in that, The method employs a microfluidic process of continuous flow shearing, and includes the following steps: S1. Inject the aqueous phase, external oil phase, and internal oil phase into the microchannel of the microfluidic device, respectively. The external oil phase shears the aqueous phase flowing in the same direction into external droplets, and after the external droplets are generated, they flow out into the receiving tube. S2. The internal phase oil is sheared into the external droplets by the co-current flowing aqueous phase, forming O / W droplets containing active substances, which are then collected and cooled.

10. The preparation method according to claim 9, characterized in that, The aqueous phase, outer oil phase, and inner oil phase are injected into the microchannel using a pneumatic pump. The inner diameter of the microchannel at the core formation point is 50-500 μm, and the outer diameter at the droplet formation point is 900-2000 μm. The flow rate of the solution is controlled by adjusting the parameters of the pressure pump. The pressure corresponding to the aqueous phase is 8-13 kPa, the pressure corresponding to the outer oil phase is 10-18 kPa, and the pressure corresponding to the inner oil phase is 2-8 kPa.

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