Sunscreen microcapsules of a starch-based wall material, and methods of making and using the same

Abstract

The application discloses a sunscreen microcapsule of starch-based wall material and a preparation method and application thereof, and the method comprises the following steps: using starch nanoparticles and polyphenols of natural sources to emulsify oil-soluble chemical sunscreen agents, so as to obtain an oil-soluble chemical sunscreen agent Pickering emulsion; introducing metal ions into the emulsion and adjusting the pH of the system; and after a network structure is formed by the metal ions and the polyphenols, centrifugal washing is performed to obtain the sunscreen microcapsule. The sunscreen microcapsule preparation method has the advantages of simple steps, high controllability, low cost and environmental friendliness. The sunscreen microcapsule prepared by the method has excellent light stability, biocompatibility and bioadhesion.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals technology, specifically relating to a sunscreen microcapsule with starch-based wall material, its preparation method, and its application. Background Technology

[0002] Prolonged exposure to ultraviolet (UV) radiation can lead to sunburn, tanning, premature aging, and even skin cancer. UV radiation is mainly divided into UVA (320-400nm) and UVB (280-320nm). UVA rays can reach the dermis, damaging cellular DNA and causing skin aging and even skin cancer. UVB rays can cause skin allergies, sunburn, and tanning. Sunscreens reduce the damage to the skin by reflecting, scattering, or absorbing UV rays. Physical sunscreens, such as titanium dioxide and zinc oxide, feel oily and heavy, may clog pores, and are prone to photocatalytic reactions that produce reactive oxygen species (ROS) that damage the skin. Chemical sunscreens are more popular with consumers due to their light, easy-to-apply texture and high transparency. Chemical sunscreens are generally aromatic small molecules, such as avobenzone, cinnamic acid esters, and salicylic acid esters. They can penetrate into the dermis and even enter the bloodstream; in addition, they have poor photostability and are easily decomposed under ultraviolet radiation, resulting in poor sun protection performance. At the same time, the free radicals they generate can affect the stability of other ingredients in the formula and may even directly damage the skin.

[0003] Microencapsulation technology can improve the above-mentioned shortcomings of chemical sunscreens to some extent. However, the existing methods for preparing sunscreen microcapsules are complex, have poor controllability, are costly, and inevitably use harmful chemical reagents. At the same time, most sunscreen microcapsules use synthetic polymers or inorganic materials as wall materials, which have poor biocompatibility, are not environmentally friendly, and do not meet the requirements of sustainable development.

[0004] Therefore, developing a simple, controllable, and environmentally friendly method to prepare sunscreen microcapsules with high photostability, good biocompatibility, and bioadhesion has great research significance and economic value. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing sunscreen microcapsules with starch-based wall materials.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing sunscreen microcapsules with starch-based wall material, comprising,

[0009] Starch nanoparticle dispersion and polyphenol solution were prepared separately.

[0010] A starch nanoparticle dispersion, a polyphenol solution, and an oil-soluble chemical sunscreen were mixed and emulsified to obtain a water-in-oil soluble chemical sunscreen, Pickering emulsion.

[0011] Metal ions were introduced into the resulting emulsion, and the pH of the system was adjusted to promote the formation of a network structure between the metal ions and polyphenols. After centrifugation and washing, sunscreen microcapsules were obtained.

[0012] In a preferred embodiment of the preparation method described in this invention, the starch nanoparticles are derived from one or more of corn, rice, potato, oats, and barley.

[0013] As a preferred embodiment of the preparation method described in this invention, the polyphenols are derived from gallnut, chestnut wood, hardwood, green tea, and witch hazel.

[0014] As a preferred embodiment of the preparation method described in this invention, the preparation of the starch nanoparticle dispersion includes,

[0015] Weigh out starch nanoparticle powder and disperse it in deionized water, adjust the pH of the aqueous phase to 3-8, and its concentration, expressed in g / mL, is 0.1-5 w / v.

[0016] As a preferred embodiment of the preparation method described in this invention, the preparation of the polyphenol solution includes,

[0017] Weigh out polyphenol powder, dissolve it in deionized water, and adjust the pH of the solution to 3-8 to obtain a polyphenol solution with a concentration of 0.01-10 w / v (g / mL).

[0018] As a preferred embodiment of the preparation method described in this invention, the oil-soluble chemical sunscreen agent includes one or more of the following: ethylhexyl methoxycinnamate, ethylhexyl salicylate, homosalate, octocrylene, dimethyl PABA ethylhexyl ester, avobenzone, and diethylaminohydroxybenzoylhexyl benzoate.

[0019] As a preferred embodiment of the preparation method described in this invention, the mass ratio of the starch nanoparticles to polyphenols is 10:1 to 1:2.

[0020] The emulsification method includes one or more of vortexing, homogenization, and ultrasound, and the emulsification time is 0.5 to 10 minutes;

[0021] The oil phase volume fraction is 5–80 v / v%.

[0022] In a preferred embodiment of the preparation method described in this invention, the metal ion is one or more of divalent copper ion, divalent zinc ion, trivalent iron ion, trivalent aluminum ion and tetravalent zirconium ion; the molar ratio of the metal ion to the polyphenol is 1:4 to 4:1; and the pH of the system is 3 to 9.

[0023] The centrifugation speed is 3000-15000 rpm, the centrifugation time is 1-10 minutes, and the number of centrifugations is 2-8.

[0024] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of sunscreen microcapsules with starch-based wall material in the preparation of cosmetics.

[0025] Another object of the present invention is to overcome the shortcomings of the prior art and provide the application of starch-based wall material microcapsules in the preparation of biocompatible sunscreens, including,

[0026] A starch nanoparticle dispersion, a polyphenol solution, and an oil-soluble chemical sunscreen ingredient were mixed and emulsified to obtain a water-in-oil soluble chemical sunscreen agent, Pickering emulsion.

[0027] Metal ions were introduced into the resulting emulsion, and the pH of the system was adjusted to promote the formation of a network structure between the metal ions and polyphenols. After centrifugation and washing, a biocompatible sunscreen was obtained.

[0028] Beneficial effects of this invention:

[0029] (1) The present invention provides a starch-based wall material microcapsule and its preparation method, and applies it to the preparation of a biocompatible sunscreen agent. The preparation method is simple, highly controllable, low-cost and environmentally friendly, overcoming the shortcomings of the existing sunscreen microcapsule preparation methods, which are complex, poorly controllable, expensive, and inevitably use harmful chemical reagents, have poor biocompatibility and are not environmentally friendly.

[0030] (2) The present invention uses naturally sourced starch nanoparticles and metal-polyphenol network with good biocompatibility and bioadhesion as wall materials, giving sunscreen microcapsules excellent biocompatibility, bioadhesion and photostability. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0032] Figure 1 An optical microscope image of the sunscreen microcapsules prepared in Example 1.

[0033] Figure 2 The image shows the appearance of the sunscreen microcapsule aqueous dispersion prepared in Example 1.

[0034] Figure 3 The in vitro SPF test values ​​are for the microcapsule sunscreen and the cream without sunscreen ingredients prepared in Example 1.

[0035] Figure 4 The sunscreen retention rate of the sunscreen microcapsule aqueous dispersion prepared in Example 1 and the unencapsulated chemical sunscreen after 8 hours of ultraviolet irradiation.

[0036] Figure 5 Laser confocal microscopy test images of the sunscreen microcapsule / saline dispersion prepared in Example 1 and the unencapsulated chemical sunscreen agent after 12 hours of penetration into pig skin.

[0037] Figure 6 This is a SEM image of the microcapsules prepared in Example 2.

[0038] Figure 7 The image shows the FT-IR spectrum of the microcapsules prepared in Example 2. Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] Unless otherwise specified in the embodiments of the present invention, the conditions are as follows; the raw materials and reagents used without specified manufacturers are all conventional reagents, methods and equipment in this technical field.

[0043] Example 1

[0044] (1) Take 8g of starch nanoparticles and disperse them in 400mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0045] (2) Dissolve 4g of polyphenol powder in 400mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0046] (3) Mix 3 mL of starch nanoparticle dispersion from step (1) and 3 mL of polyphenol solution from step (2), then add 0.6 mL of ethylhexyl methoxycinnamate and sonicate at 400 W for 5 minutes to obtain Pickering emulsion template.

[0047] (4) Add 6 mL of 3 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 8, and finally wash the mixture three times by centrifugation with deionized water at a speed of 8000 rpm for 5 minutes to obtain sunscreen microcapsules with starch-based wall material. Disperse the sunscreen microcapsules in deionized water to make the total volume of the sunscreen microcapsule aqueous dispersion 6 mL.

[0048] (5) The sunscreen microcapsules obtained in step (4) are mixed with Dabao Vitamin E lotion without sunscreen ingredients to obtain sunscreen cream, with the sunscreen microcapsule content being 10wt%.

[0049] Figure 1 The image shown is an optical microscope photograph of the aqueous dispersion of the sunscreen microcapsules in Example 1. It can be clearly observed that the sunscreen microcapsules have a good spherical morphology with an average particle size of about 1 μm, indicating that the method can control the size of the microcapsules through emulsification conditions and system composition.

[0050] Figure 2 The image shows the appearance of the aqueous dispersion of the sunscreen microcapsules in Example 1, indicating that the sunscreen microcapsules have good water dispersibility.

[0051] SPF test:

[0052] According to the ISO 24443:2012 standard method, the UV transmittance analyzer (UV-2000S) was used to test the Dabao Vitamin E lotion and the microcapsule sunscreen obtained in step (5).

[0053] Figure 3The in vitro SPF test values ​​of the microcapsule sunscreen prepared in Example 1 and the Dabao Vitamin E lotion without sunscreen ingredients are shown. Compared with Dabao Vitamin E lotion, the microcapsule sunscreen has better sun protection performance.

[0054] Light stability test:

[0055] The microcapsules prepared in step (4) of Example 1 were dispersed in anhydrous ethanol, vortexed and centrifuged, and the ultraviolet absorbance of the supernatant at 311 nm was measured and recorded as A1.

[0056] Unencapsulated chemical sunscreen ethylhexyl methoxycinnamate was dispersed in anhydrous ethanol, vortexed, and centrifuged. The ultraviolet absorbance of the supernatant at 311 nm was measured and denoted as A2.

[0057] The microcapsules prepared in step (4) of Example 1 and the unencapsulated chemical sunscreen were irradiated with an 800W ultraviolet lamp. After irradiation for 8 hours, the samples were dispersed in anhydrous ethanol, vortexed and centrifuged. The absorbance of the supernatant of both samples at 311 nm was measured and recorded as A3 and A4, respectively.

[0058] Retention rate of unencapsulated chemical sunscreen agents (%) = A4 / A2 × 100%.

[0059] The sunscreen retention rate (%) of starch-based wall material sunscreen microcapsules = A3 / A1 × 100%.

[0060] Figure 4 The sunscreen microcapsule aqueous dispersion prepared in Example 1, the unencapsulated chemical sunscreen agent, and the Pickering emulsion prepared in Comparative Example 3 were compared under 800W UV light irradiation for 8 hours to determine the sunscreen agent retention rates. The unencapsulated chemical sunscreen agent had a retention rate of only about 10%, the retention rate of the chemical sunscreen agent in the Pickering emulsion stabilized by starch nanoparticles alone was 25%, while the retention rate of the chemical sunscreen agent in the microcapsules was close to 60%, approximately 5 times and 2 times that of the former, respectively. This demonstrates that the sunscreen microcapsules effectively improve the photostability of the encapsulated chemical sunscreen agent.

[0061] Laser confocal test:

[0062] Skin penetration was simulated using the Franz diffusion model;

[0063] The microcapsules prepared in step (4) of Example 1 were dispersed in 600 mL of PBS buffer solution to obtain a PBS dispersion of sunscreen microcapsules.

[0064] Pigskin was sandwiched between the donor and receiver cells of the Franz diffusion cell. The diffusion solutions were PBS dispersion of the sunscreen microcapsules and unencapsulated chemical sunscreen ethylhexyl methoxycinnamate, respectively, and the receiver solution was PBS buffer.

[0065] The Franz pool was placed in a 37°C water bath for 12 hours, after which the pigskin was removed. The surface of the pigskin was rinsed with 20 mL of PBS buffer, and then sliced ​​into thin sections at -20°C using a cryostat. The penetration of microcapsules and unencapsulated chemical sunscreens into the pigskin was observed under a laser confocal scanning microscope.

[0066] Figure 5 Laser confocal microscopy test image of the sunscreen microcapsules prepared in Example 1 and the unencapsulated chemical sunscreen agent after 12 hours of residence on the surface of pigskin; Figure 5 As can be seen, the sunscreen microcapsules mainly reside on the surface of pig skin. Even after multiple rinsings with PBS buffer, sunscreen microcapsules still adhere to the surface of the pig skin, while the unencapsulated chemical sunscreen has penetrated into the dermis of the pig skin. This demonstrates the excellent bioadhesion of the sunscreen microcapsules. At the same time, the wall material of the microcapsules can prevent the chemical sunscreen from directly contacting the skin, thus enhancing its safety of use.

[0067] Example 2

[0068] (1) Take 6g of starch nanoparticles and disperse them in 300mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0069] (2) Dissolve 1g of polyphenol powder in 100mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0070] (3) Mix 1.5 mL of starch nanoparticle dispersion from step (1) and 1.5 mL of polyphenol solution from step (2), then add 0.6 mL of n-hexane and sonicate at 500 W for 4 minutes to obtain Pickering emulsion template.

[0071] (4) Add 3 mL of 3.2 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 7.4, and finally wash the microcapsules three times by centrifugation with deionized water at a speed of 4000 rpm for 6 minutes to obtain microcapsules.

[0072] Volatile n-hexane was chosen to replace chemical sunscreens as the core material to further confirm the formation and composition of the microcapsule wall material.

[0073] Figure 6 The image shown is a SEM image of the microcapsules in Example 2. The morphology of the collapsed sample confirms the formation of the microcapsule wall material and its hollow structure.

[0074] Figure 7The FT-IR spectrum of the microcapsules in Example 2 shows the characteristic absorption peaks of starch nanoparticles and polyphenols. Furthermore, the intensity of the C-OH characteristic peak in the polyphenols decreases significantly, confirming the formation of a metal-polyphenol network. This demonstrates that the main component of the microcapsule wall material is starch nanoparticles / metal-polyphenol network.

[0075] Example 3

[0076] (1) Take 60g of starch nanoparticles and disperse them in 3000mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0077] (2) Dissolve 1g of polyphenol powder in 100mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0078] (3) Mix and dissolve 2 mL of starch nanoparticle dispersion from step (1) and 2 mL of polyphenol solution from step (2), then add 0.4 mL of ethylhexyl methoxycinnamate and sonicate at 520 W for 4 minutes to obtain Pickering emulsion template.

[0079] (4) Add 4 mL of 5.5 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 9, and finally wash the mixture four times by centrifugation with deionized water at a speed of 9000 rpm for 7 minutes to obtain sunscreen microcapsules. Disperse the sunscreen microcapsules in deionized water to make the total volume of the sunscreen microcapsule aqueous dispersion 4 mL.

[0080] (5) The sunscreen microcapsules obtained in step (4) are mixed with a certain amount of Dabao vitamin E lotion without sunscreen ingredients to obtain a microcapsule sunscreen cream with a sunscreen content of 10wt%.

[0081] The same microcapsule preparation method, optical microscope images, appearance of microcapsule aqueous dispersion, SPF test, photostability test, and laser confocal test were used as in Example 1.

[0082] The results are respectively with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 They are basically the same.

[0083] Example 4

[0084] (1) Take 2g of starch nanoparticles and disperse them in 100mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0085] (2) Dissolve 5g of polyphenol powder in 500mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0086] (3) Mix 2.5 mL of starch nanoparticle dispersion from step (1) and 2.5 mL of polyphenol solution from step (2), then add 1 mL of n-hexane and sonicate at 390 W for 6 minutes to obtain Pickering emulsion template.

[0087] (4) Add 5 mL of 6.7 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 7.7, and finally wash the microcapsules three times by centrifugation with deionized water at a speed of 4000 rpm for 6 minutes to obtain microcapsules.

[0088] The same microcapsule preparation method, SEM images, and FT-IR images as in Example 2 were used. The results were compared with... Figure 6 , Figure 7 They are basically the same.

[0089] Example 5

[0090] (1) Take 3g of starch nanoparticles and disperse them in 150mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0091] (2) Dissolve 3g of polyphenol powder in 300mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0092] (3) Mix and dissolve 4 mL of starch nanoparticle dispersion from step (1) and 4 mL of polyphenol solution from step (2), then add 0.8 mL of ethylhexyl methoxycinnamate and sonicate for 5 minutes at 450 W to obtain Pickering emulsion.

[0093] (4) Add 8 mL of 3.5 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 7, and finally wash the mixture four times by centrifugation with deionized water at a speed of 9000 rpm for 7 minutes to obtain sunscreen microcapsules. Disperse the sunscreen microcapsules in deionized water to make the total volume of the sunscreen microcapsule aqueous dispersion 8 mL.

[0094] (5) The sunscreen microcapsules obtained in step (4) are mixed with a certain amount of Dabao vitamin E lotion without sunscreen ingredients to obtain a microcapsule sunscreen cream with a sunscreen content of 10wt%.

[0095] The same microcapsule preparation method, optical microscope images, appearance images of the microcapsule aqueous dispersion, SPF test, photostability test, and laser confocal microscopy test were used as in Example 1. The results are respectively compared with... Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 They are basically the same.

[0096] Example 6

[0097] (1) Take 0.7g of starch nanoparticles and disperse them in 35mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0098] (2) Dissolve 0.3g of polyphenol powder in 30mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0099] (3) Mix 3.5 mL of starch nanoparticle dispersion from step (1) and 3.5 mL of polyphenol solution from step (2), then add 0.7 mL of ethylhexyl methoxycinnamate and sonicate at 420 W for 4.5 minutes to obtain Pickering emulsion template.

[0100] (4) Add 8 mL of 5 mM ferric chloride solution to the Pickering emulsion template in step (3), adjust the pH of the system to 8.5, and finally wash the mixture four times by centrifugation with deionized water at a speed of 9000 rpm for 7 minutes to obtain sunscreen microcapsules. Disperse the sunscreen microcapsules in deionized water to obtain a total volume of 7 mL of the aqueous dispersion.

[0101] (5) The sunscreen microcapsules obtained in step (4) are mixed with a certain amount of Dabao vitamin E lotion without sunscreen ingredients to obtain a microcapsule sunscreen cream with a sunscreen content of 10wt%.

[0102] The same microcapsule preparation method, optical microscope images, appearance images of the microcapsule aqueous dispersion, SPF test, photostability test, and laser confocal microscopy test were used as in Example 1. The results are respectively compared with... Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 Basically the same

[0103] Comparative Example 1

[0104] (1) Take 1.5g of starch nanoparticles and disperse them in 300mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0105] (2) Dissolve 2g of polyphenol powder in 200mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0106] (3) Mix 4 mL of starch nanoparticle dispersion from step (1) and 4 mL of polyphenol solution from step (2), then add 0.8 mL of octocrylene humosaside, and sonicate at 480 W for 4 minutes to obtain Pickering emulsion template.

[0107] This emulsion template has poor stability and exhibits oil leakage, making it unsuitable for preparing sunscreen microcapsules.

[0108] Comparative Example 2

[0109] (1) Take 0.9g of starch nanoparticles and disperse them in 45mL of deionized water. Adjust the pH to 5 to obtain a 2w / v% starch nanoparticle dispersion.

[0110] (2) Dissolve 0.7g of polyphenol powder in 70mL of deionized water and adjust the pH to 5 to obtain a 1w / v% polyphenol solution.

[0111] (3) Mix 1.5 mL of starch nanoparticle dispersion from step (1) and 1.5 mL of polyphenol solution from step (2), then add 7 mL of ethylhexyl methoxycinnamate and sonicate at 470 W for 5 minutes to obtain Pickering emulsion template.

[0112] (4) Add 3 mL of 5.9 mM ferric chloride solution to the Pickering emulsion template in step (3) and adjust the pH of the system to 7.5.

[0113] The Pickering emulsion template prepared in Comparative Example 2 was gel-like and had poor flowability. The ferric chloride solution was difficult to disperse in the aqueous phase of the emulsion and could not fully form a metal-polyphenol network with the polyphenols at the oil-water interface, thus failing to form a microcapsule structure.

[0114] Comparative Example 3

[0115] (1) Take 3g of starch nanoparticles and disperse them in 300mL of deionized water. Adjust the pH to 5 to obtain a 1w / v% starch nanoparticle dispersion.

[0116] (2) Mix 6 mL of starch nanoparticle dispersion from step (1) with 0.6 mL of ethylhexyl methoxycinnamate and sonicate at 400 W for 5 minutes to obtain Pickering emulsion template.

[0117] (3) Disperse the Pickering emulsion prepared in step (2) in anhydrous ethanol and measure its ultraviolet absorbance at 311 nm, which is recorded as A4.

[0118] The Pickering emulsion prepared in step (2) was irradiated with an 800W ultraviolet lamp. After irradiation for 8 hours, it was dispersed in anhydrous ethanol, vortexed, and centrifuged. The absorbance of the supernatant at 311 nm was measured and recorded as A5.

[0119] Retention rate (%) of chemical sunscreen agents in starch nanoparticle-stabilized Pickering emulsion = A4 / A5 × 100%.

[0120] This invention discloses a starch-based wall material microcapsule and its preparation method, and applies it to the preparation of a biocompatible sunscreen. The preparation method is simple, highly controllable, low-cost, and environmentally friendly, overcoming the shortcomings of existing sunscreen microcapsule preparation methods, which are complex, poorly controllable, costly, and inevitably involve the use of harmful chemical reagents, poor biocompatibility, and are environmentally unfriendly. This invention uses naturally derived starch nanoparticles and a metal-polyphenol network with good biocompatibility and bioadhesion as the wall material, endowing the sunscreen microcapsules with excellent biocompatibility, bioadhesion, and photostability.

[0121] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing sunscreen microcapsules with a starch-based wall material, characterized in that: include, Starch nanoparticle dispersion and polyphenol solution were prepared separately. A starch nanoparticle dispersion, a polyphenol solution, and an oil-soluble chemical sunscreen were mixed and emulsified to obtain a water-in-oil soluble chemical sunscreen, Pickering emulsion. Metal ions were introduced into the resulting emulsion, and the pH of the system was adjusted to promote the formation of a network structure between the metal ions and polyphenols. After centrifugation and washing, sunscreen microcapsules were obtained. The starch nanoparticles are derived from one or more of corn, rice, potatoes, oats, and barley; the polyphenols are derived from gallnut, chestnut wood, hardwood, green tea, and witch hazel. The metal ion is one or more of divalent copper ion, divalent zinc ion, trivalent iron ion, trivalent aluminum ion and tetravalent zirconium ion, the molar ratio of the metal ion to polyphenol is 1:4 to 4:1, and the pH of the system is 3 to 9.

2. The preparation method according to claim 1, characterized in that: The preparation of the starch nanoparticle dispersion includes, Weigh out starch nanoparticle powder and disperse it in deionized water. Adjust the pH of the aqueous phase to 3-8. Its concentration, expressed in g / mL, is 0.1-5 w / v.

3. The preparation method according to claim 1, characterized in that: The preparation of the polyphenol solution includes, Weigh out polyphenol powder, dissolve it in deionized water, and adjust the pH of the solution to 3-8 to obtain a polyphenol solution with a concentration of 0.01-10 w / v in g / mL.

4. The preparation method according to claim 3, characterized in that: The oil-soluble chemical sunscreen agents include one or more of the following: ethylhexyl methoxycinnamate, ethylhexyl salicylate, homosalate, octocrylene, dimethyl PABA ethylhexyl ester, avobenzone, and diethylaminohydroxybenzoylhexyl benzoate.

5. The preparation method according to claim 4, characterized in that: The mass ratio of starch nanoparticles to polyphenols is 10:1 to 1:

2. The emulsification method includes one or more of vortexing, homogenization, and ultrasound, and the emulsification time is 0.5 to 10 minutes; The oil phase volume fraction is 5~80 v / v%.

6. The preparation method according to claim 5, characterized in that: The centrifugation speed is 3000~15000 rpm, the centrifugation time is 1~10 minutes, and the number of centrifugations is 2~8.

7. The use of sunscreen microcapsules made of starch-based wall material prepared by any of the preparation methods described in claims 1 to 6 in the preparation of cosmetics.

8. The application of a starch-based wall material microcapsule in the preparation of a biocompatible sunscreen, characterized in that: include, A starch nanoparticle dispersion, a polyphenol solution, and an oil-soluble chemical sunscreen ingredient were mixed and emulsified to obtain a water-in-oil soluble chemical sunscreen agent, Pickering emulsion. Metal ions were introduced into the resulting emulsion, and the pH of the system was adjusted to promote the formation of a network structure between the metal ions and polyphenols. After centrifugation and washing, a biocompatible sunscreen was obtained. The metal ion is one or more of divalent copper ion, divalent zinc ion, trivalent iron ion, trivalent aluminum ion and tetravalent zirconium ion, the molar ratio of the metal ion to polyphenol is 1:4 to 4:1, and the pH of the system is 3 to 9. The starch nanoparticles are derived from one or more of corn, rice, potatoes, oats, and barley; the polyphenols are derived from gallnut, chestnut wood, hardwood, green tea, and witch hazel.

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