Composite microcapsule as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of cosmetics, and discloses a composite microcapsule as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing a gelatin solution and an Arabic gum solution in an acetic acid solution, and adding a sodium hydroxide solution to adjust the pH value to 4.0 to obtain a mixed solution; (2) mixing n-butyl cyanoacrylate with tea tree essential oil, dropwise adding the mixture into the mixed solution obtained in the step (1), stirring, cooling with cold water, and adding transglutaminase for curing; and (3) cleaning impurities with purified water, and then freeze-drying to obtain the composite microcapsule. On the basis of a gelatin-Arabic gum single-layer microcapsule, n-butyl cyanoacrylate is selected to coat the single-layer microcapsule, so that the ion stability, the storage stability and the permeation stability of the composite microcapsule are obviously improved, and the composite microcapsule has good essential oil controlled release capability and long-acting oxidation resistance; and the application capability of the composition as a cosmetic component is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of cosmetics, and more specifically relates to a composite microcapsule and a preparation method and application thereof. Background Art

[0002] Microcapsules are sealed or semipermeable microcapsules formed by encapsulating active substances in film-forming materials (natural, synthetic or semi-synthetic materials) through physical, chemical or physicochemical methods. Tea tree essential oil has antibacterial, anti-inflammatory, whitening and free radical scavenging effects, so it is widely used in cosmetics. However, tea tree essential oil is volatile and easily affected by light and oxidative decomposition, so there are certain limitations in its application in cosmetics. Therefore, the development of microcapsules encapsulating tea tree essential oil may effectively improve the stability of essential oil, and then use it as a cosmetic ingredient.

[0003] The main problem with the application of microcapsules is stability. The internal reason is mainly the choice of wall materials. The surface of microcapsules prepared from natural proteins has high viscosity, which easily causes adhesion and aggregation of microcapsules. Such highly aggregated microcapsules will cause ruptures between the shells, causing leakage of internal active substances. The external problems of microcapsule application are factors such as osmotic pressure and oxidation. In actual application, microcapsules are in an environment where multiple active substances coexist. The increase in the content of active substances will gradually increase the osmotic pressure in the solution. Microcapsules generally have a single shell structure. When the osmotic pressure reaches a certain level, the microcapsules will gradually expand and eventually rupture. The shell cannot protect the active substances inside the microcapsules.

[0004] The current technology for preparing microcapsules is chemical polymerization, mainly complex coacervation, which is a method of encapsulating active substances by polymerization of wall material monomers. This method achieves polymerization between wall materials and can retain the original properties. However, more binding sites will be exposed during the polymerization process. Therefore, factors such as ions in the external environment, heat, internal osmotic pressure and pH value have a great influence on the polymer monolayer, and the storage stability and osmotic stability of microcapsules are also affected.

[0005] Therefore, how to provide a composite microcapsule and a preparation method and application thereof is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0006] In order to overcome the shortcomings and deficiencies in the prior art, the present invention provides a composite microcapsule and a preparation method and application thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing a composite microcapsule comprises the following steps:

[0009] (1) mixing a gelatin solution and a gum arabic solution in an acetic acid solution, adding a sodium hydroxide solution to adjust the pH value to 4.0, and obtaining a mixed solution;

[0010] (2) mixing n-butyl cyanoacrylate with tea tree essential oil, dripping the mixture into the mixed solution obtained in step (1), stirring, cooling with cold water, and adding transglutaminase to solidify;

[0011] (3) The impurities are washed away with purified water and then freeze-dried to obtain composite microcapsules.

[0012] Preferably, the mass concentration of the gelatin solution is 2%, the mass concentration of the gum arabic solution is 2%, and the concentration of the acetic acid solution is 0.5%.

[0013] The beneficial effect of the above technical solution is that at this mass concentration, the formed composite microcapsules are relatively stable.

[0014] Preferably, the volume ratio of the gelatin solution to the gum arabic solution is 1:1.

[0015] Preferably, the temperature of the acetic acid solution is 40°C.

[0016] Preferably, the mass ratio of n-butyl cyanoacrylate to tea tree essential oil is 1:4.

[0017] The beneficial effect of the above technical solution is that n-butyl cyanoacrylate, as a fast-acting adhesive, will rapidly undergo polymerization reaction to form a polycyanoacrylate polymer film under the action of a nucleophilic reagent.

[0018] Preferably, the mass ratio of the tea tree essential oil to the mixed liquid is 15:4.

[0019] Preferably, the stirring time in step (2) is 2 hours.

[0020] The beneficial effect of the above technical solution is that by adjusting the volume ratio of gelatin and gum arabic, the temperature of the acetic acid solution, the stirring time and other parameters, the formed composite microcapsules can have a higher encapsulation rate.

[0021] Preferably, the added amount of the transglutaminase is 0.2% (w / v).

[0022] The present invention also provides a composite microcapsule prepared according to the above preparation method.

[0023] The present invention also provides application of the above-mentioned composite microcapsule in cosmetic ingredients.

[0024] It can be seen from the above technical scheme that compared with the prior art, the present invention provides a composite microcapsule and a preparation method and application thereof, which have the following beneficial effects: the present invention adopts a composite coacervation method-interfacial polymerization method to prepare composite microcapsules loaded with tea tree essential oil, and on the basis of gelatin-gum arabic single-layer microcapsules, another wall material, cyanoacrylate n-butyl ester, is selected to coat the single-layer microcapsules, thereby effectively improving the performance of the composite microcapsules, and the ion stability, storage stability and penetration stability of the composite microcapsules are significantly improved, and the composite microcapsules have good essential oil controlled release ability and long-lasting antioxidant ability, thereby improving their application ability as cosmetic ingredients. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 The present invention provides a process for preparing the composite microcapsules.

[0027] Figure 2 a and b are scanning electron microscope images of the condensed microcapsules obtained in Comparative Example 1 and the composite microcapsules obtained in Example 1, respectively.

[0028] Figure 3 The ionic stability of the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1.

[0029] Figure 4 The storage stability of the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1.

[0030] Figure 5 The penetration stability of the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1.

[0031] Figure 6 The release curves of the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1 within 15 days are shown.

[0032] Figure 7a It is the DPPH scavenging rate of tea tree essential oil, the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1.

[0033] Figure 7b It is the ABTS clearance rate of tea tree essential oil, the composite microcapsules obtained in Example 1 and the condensed microcapsules obtained in Comparative Example 1. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] Preparation of composite microcapsules by complex coacervation-in-situ polymerization

[0037] (1) mixing 10 mL of a 2% gelatin solution and 10 mL of a 2% gum arabic solution in a 0.5% acetic acid solution at 40° C., and adding a sodium hydroxide solution to adjust the pH value to 4.0 to obtain a mixed solution;

[0038] (2) mixing n-butyl cyanoacrylate and tea tree essential oil in a mass ratio of 1:4, dripping into the mixed solution, wherein the mass ratio of tea tree essential oil to the mixed solution is 15:4, stirring for 2 h, cooling with cold water, and adding transglutaminase for solidification, wherein the amount of transglutaminase added is 0.2% (w / v);

[0039] (3) washing impurities with purified water, and then placing the mixture in a freeze dryer for freeze drying to obtain composite microcapsules, namely, tea tree essential oil / n-butyl cyanoacrylate / gelatin / gum arabic composite microcapsules.

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that n-butyl cyanoacrylate is not added in step (2), and the rest is the same. The obtained condensed microcapsules are tea tree essential oil / gelatin / gum arabic condensed microcapsules.

[0042] from Figure 2 As can be seen in a, the surface shape of the unoptimized condensed microcapsules is irregular, with large depressions and an overall irregular shape. Under 2000 times magnification, it can be seen that the microcapsules are in an irregular flake shape, which may be due to the lack of stability of the microcapsules and the rupture after freeze-drying. Figure 2 As can be seen in b, the composite microcapsule is spherical in shape, with a smooth surface and slight depressions, which may be caused by drying. Under a 2000x magnifying glass, it can be seen that the whole is relatively intact without any cracks.

[0043] 1. Stability test

[0044] 1. Ionic stability

[0045] Sodium chloride solutions of different concentrations (20, 40, 60, 80, 100 mmol / L) were prepared, 0.5 g of the composite microcapsules obtained in Example 1 were taken, 4.5 g of deionized water was added, 5 mL of sodium chloride solution was added after sufficient mixing, and the mixture was gently stirred. After being stored at room temperature for 24 hours, the mixture was centrifuged and filtered, and the absorbance of the supernatant was measured at 265 nm to investigate the effect of different ionic strengths on the stability of the composite microcapsules. The same was true for the condensed microcapsules of Comparative Example 1.

[0046] like Figure 3 As shown in the figure, with the increase of ion concentration, the concentration of essential oil in the composite microcapsules and condensed microcapsules increased, indicating that the ion concentration has an effect on both composite microcapsules and condensed microcapsules, which can affect the stability of the condensed layer and thus destroy the microcapsules. As can be seen from the figure, the rate of increase of the concentration of essential oil in the composite microcapsule solution is slower than that of the condensed microcapsules, which shows that the composite microcapsules have a strong resistance to anions and cations and have better stability.

[0047] 2. Storage stability

[0048] Take 0.5 g of the composite microcapsules obtained in Example 1, add 4.5 g of deionized water, mix thoroughly and place in dark conditions, and measure the peroxide value of the composite microcapsules on the 5th, 10th, 15th, 20th, 25th and 30th days to investigate the effect of storage time on the stability of the microcapsules. The same is true for the condensed microcapsules of Comparative Example 1.

[0049] like Figure 4 As shown in the figure, the peroxide value of the composite microcapsules and the condensed microcapsules showed a rising trend. The oxidation value of the composite microcapsules increased more slowly than that of the condensed microcapsules, indicating that the composite microcapsules could further reduce the oxidation rate of the core material. The reason may be that the double-layer membrane of the composite microcapsules could further play a role in sustained release, effectively improving the sustained release capacity of the capsules. The results showed that the composite microcapsules had better storage stability.

[0050] 3. Penetration stability

[0051] Take 0.5 g of the composite microcapsules obtained in Example 1 and add 10 mL of a 4.1×10 -2 mol / L sodium dodecyl sulfate solution, mix thoroughly, take part of the supernatant at 3, 6, 9, 12, and 15 hours, centrifuge and filter, measure the absorbance of the solution at 265 nm, and investigate the effect of osmotic pressure on the stability of the composite microcapsules. The same is true for the condensed microcapsules of Comparative Example 1.

[0052] like Figure 5As shown in the figure, during the observation period, the essential oil content in the condensed microcapsules increased sharply. In the osmotic environment, the essential oil in the condensed microcapsules was released in large quantities. The reason may be that the osmotic pressure inside and outside the condensed microcapsules in the osmotic environment caused the condensed microcapsules to rupture in large quantities, and they could not protect the essential oil. In the osmotic environment, the essential oil content in the solution of the composite microcapsules increased slowly, maintaining a sustained release effect, indicating that the composite microcapsules maintained a high stability in the osmotic environment. The reason may be that the addition of the polymer membrane enhanced the overall rigidity of the composite microcapsules and made them more resistant to osmotic pressure.

[0053] 2. Study on the release behavior of composite microcapsules

[0054] 1. In vitro release

[0055] The release behaviors of the condensed microcapsules of comparative example 1 and the composite microcapsules of example 1 at room temperature were compared. The composite microcapsules were placed in an open environment at 37°C and pH 5.5, and the same number of samples were collected at regular intervals (3, 6, 9, 12 and 15 days). The content of essential oil in the microcapsules was detected by UV-visible spectrophotometry. The amount of essential oil released was calculated, and the curve of the amount of essential oil released over time was obtained.

[0056] Figure 6 The release curves of composite microcapsules and coacervate microcapsules at 15 days show that both types of capsules gradually release more and more essential oils as time goes on. It is worth noting that coacervate microcapsules show burst release behavior at the beginning, followed by a gradual slowing of the release rate, while composite microcapsules maintain a more stable release throughout the process, with a slightly slower rate. The results show that both coacervate microcapsules and composite microcapsules have a controlled release effect on essential oils, and composite microcapsules show a stronger ability to control the release of essential oils compared to coacervate microcapsules.

[0057] 2. Study on the antioxidant capacity of composite microcapsules

[0058] According to the mass of tea tree essential oil, a certain amount of tea tree essential oil, the condensed microcapsules obtained in comparative example 1 and the composite microcapsule samples obtained in example 1 were weighed and dissolved in equal volumes of anhydrous ethanol, respectively, to ensure that the concentration of tea tree essential oil in the three solutions was the same. Sample solutions (2 mL) were taken out at a certain time interval from each of the above samples, gently shaken and centrifuged to obtain a transparent sample solution. Under human skin conditions (37°C, pH 5.5), the clearance rates of 2,2-diphenyl-1-phenylpicrylhydrazyl (DPPH) and 2,2-azobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt) (ABTS) were determined.

[0059] As shown in Figure 7, on day 0, tea tree oil (TTO) showed the highest activity in scavenging DPPH and ABTS free radicals, followed by coacervate microcapsules, and the composite microcapsules had the lowest activity. During the entire storage period, the antioxidant capacity of the composite microcapsules decreased the slowest, while the antioxidant capacity of TTO decreased the fastest. On the 15th day of storage, the composite microcapsules had a higher scavenging rate for both free radicals than the coacervate microcapsules.

[0060] In summary, the essential oil-loaded composite microcapsules prepared by the composite coacervation-in-situ polymerization method of the present invention are superior to the essential oil-loaded coacervate microcapsules in ion stability, storage stability and anti-penetration stability; the essential oil-loaded composite microcapsules have better essential oil controlled-release ability than the essential oil-loaded coacervate microcapsules; compared with the pure essential oil and the essential oil-loaded coacervate microcapsules, the essential oil-loaded composite microcapsules have the slowest weakening antioxidant ability, showing excellent long-acting antioxidant ability; and their application ability as cosmetic ingredients is improved.

[0061] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0062] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite microcapsule, characterized in that: The following steps are involved: (1) mixing a gelatin solution and a gum arabic solution in an acetic acid solution, adding a sodium hydroxide solution to adjust the pH value to 4.0, and obtaining a mixed solution; (2) mixing n-butyl cyanoacrylate with tea tree essential oil, dripping the mixture into the mixed solution obtained in step (1), stirring, cooling with cold water, and adding transglutaminase to solidify; (3) The impurities are washed away with purified water and then freeze-dried to obtain composite microcapsules.

2. The method for preparing a composite microcapsule according to claim 1, characterized in that: The mass concentration of the gelatin solution is 2%, the mass concentration of the gum arabic solution is 2%, and the concentration of the acetic acid solution is 0.5%.

3. The method for preparing a composite microcapsule according to claim 1, characterized in that: The volume ratio of the gelatin solution to the gum arabic solution is 1:

1.

4. The method for preparing a composite microcapsule according to claim 1, characterized in that: The temperature of the acetic acid solution was 40°C.

5. The method for preparing a composite microcapsule according to claim 1, characterized in that: The mass ratio of the n-butyl cyanoacrylate to the tea tree essential oil is 1:

4.

6. The method for preparing a composite microcapsule according to claim 1, characterized in that: The mass ratio of the tea tree essential oil to the mixed liquid is 15:

4.

7. The method for preparing a composite microcapsule according to claim 1, characterized in that: The stirring time in step (2) is 2 h.

8. The method for preparing a composite microcapsule according to claim 1, characterized in that: The added amount of the transglutaminase is 0.2% (w / v).

9. A composite microcapsule prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the composite microcapsule according to claim 9 in cosmetic ingredients.

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