Preparation and application of nano-emulsion for treating skin photoaging

Abstract

The invention belongs to the technical field of biological medicines, and particularly relates to preparation and application of a nanoemulsion. The PDA / TEMPO NMsE nano-emulsion prepared by the invention can block lipid peroxidation chain reaction of a skin photoaging part and effectively reduce the inflammatory mediator level, and compared with retinoic acid or polydopamine, the PDA / TEMPO NMsE nano-emulsion has a more excellent skin photoaging treatment effect, can keep a protection effect for a long time, and has a good application prospect. The problem that the efficiency of removing alkoxy and alkyl peroxy free radicals by a single PDA material is insufficient is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biological medicine, and particularly relates to preparation and application of a nanoemulsion. BACKGROUND

[0002] Photoaging is a phenomenon of premature skin aging caused by long-term repeated exposure to ultraviolet (UV) radiation, and is the result of the combined action of internal natural aging and external environmental factors (mainly sunlight), in which ultraviolet radiation plays an absolutely dominant role. With the increasingly serious environmental problems, the destruction of the ozone layer causes the gradually increasing ultraviolet radiation reaching the ground, and the skin photoaging disease is also more and more common, and the number of patients shows a rising trend year by year. At the same time, more and more people begin to pay attention to anti-photoaging, and the demand for delaying aging and treating photoaging is increasing.

[0003] The core mechanism of photoaging of skin caused by external environmental factors is that ultraviolet radiation induces the production of reactive oxygen species (ROS) to cause oxidative stress, triggering a series of damage such as lipid peroxidation, protein oxidation and cross-linking (especially collagen and elastin), DNA damage, and further activating key signaling pathways AP-1 and NF-κB, resulting in overexpression of matrix metalloproteinases (MMPs) to degrade collagen; meanwhile, it also inhibits the synthesis of new collagen, causing serious damage and remodeling abnormalities of the extracellular matrix (collagen, elastic fibers) of the dermis (Doxercalciferol alleviates UVB-induced HaCaT cell senescence and skin photoaging[J]. Int Immunopharmacol. 2024; 127: 111357.). Ultimately, photoaging will cause rough, dry, wrinkled, and reduced skin elasticity, local pigmentation, and capillary dilation in the aging area. Moreover, with the accumulation of ultraviolet radiation, photoaging will cause premature aging of the skin, and more seriously, it can even induce diseases such as malignant skin tumors, melanoma, and squamous cell carcinoma. Therefore, removing excess ROS is a breakthrough point for effectively treating photoaging.

[0004] The ROS involved in the process of photoaging mainly include hydroxyl radicals (OH·), hydrogen peroxide (H2O2), superoxide anion (O 2- ), singlet oxygen ( 1O2) etc. Among them, hydrogen peroxide and superoxide anion are relatively easy to be scavenged. While the free radical active oxygen has extremely strong chemical reactivity, in many cases, the free radical active oxygen can attack the polyunsaturated fatty acids (PUFAs) in the cell, and a large number of alkoxy or alkylperoxy radicals (RO· or ROO·) can be produced. Ultraviolet light can also directly induce polyunsaturated fatty acids to convert into alkoxy or alkylperoxy radicals. Such radicals have the characteristics of long half-life and high affinity for PUFAs. Unlike the local transient damage of hydroxyl radicals OH·, such radicals can continuously diffuse in the lipid environment of the cell membrane, trigger lipid peroxidation chain reaction, directly cause cell membrane structure damage, inflammation signal activation and MMPs overexpression, and then degrade collagen and elastic fibers, forming wrinkles, relaxation and other photoaging characteristics. Therefore, the damage of alkoxy or alkylperoxy radicals to the skin is higher than that of other several types of radicals.

[0005] However, the current scavenging means for such radicals has limitations. Traditional antioxidants are easily oxidized and consumed, and need to be continuously and repeatedly supplemented. Enzymatic antioxidants are easily inactivated and have poor skin permeability, making it difficult to play a long-acting role in the local area. The first-line treatment drugs for skin photoaging in clinical practice are mainly retinol compounds and fruit acid drugs (Comparison of five retinoids for anti-photoaging therapy: Evaluation of anti-inflammatory and anti-oxidative activities in vitro and therapeutic efficacy in vivo [J]. Photochem Photobiol. 2024; 100(3): 633-645.) (Comparison of clinical efficacy of fruit acid and left-handed vitamin C in the treatment of facial skin photoaging [J]. Dermatology and Sexually Transmitted Diseases, 2021, 43(04): 533-535.). Generally, in the early stage of retinoid drug treatment, side effects such as erythema, desquamation and burning will occur; in addition, retinoid drugs have potential teratogenicity, and may also increase the sensitivity of the skin to ultraviolet light when used for a long time and in large quantities, thereby increasing the potential risk of skin damage. Fruit acid treatment can also cause local adverse reactions, such as transient redness, tingling of the skin after treatment, and even scabbing and pigmentation in a small number of people; the concentration and residence time of fruit acid use are highly dependent on the professional level of the operator, and it is difficult to achieve the expected therapeutic effect under low concentration and short residence time; otherwise, it will significantly increase the risk of adverse reactions.

[0006] In addition, polydopamine (PDA) is a kind of mussel biomimetic material, which has simple preparation method, good biocompatibility, and can remove strong oxidative hydroxyl radicals, and can also load drugs, and is one of the commonly used materials in the field of nanomedicine. Recent studies have shown that polydopamine can remove alkoxy or alkylperoxy radicals. Its main removal mechanism is to provide electrons to alkoxy radicals through the catechol-like structure on its surface, thereby reducing alkoxy radicals and removing alkoxy radicals. However, polydopamine exists in a spherical form during polymerization, and the spherical surface has high chemical reactivity, which causes most of the catechol-like structures on the surface to be oxidized during self-polymerization, and converted into quinone structure, thereby seriously reducing its removal performance on such radicals.

[0007] Therefore, in order to completely, stably and efficiently remove alkoxy or alkylperoxy radicals, it is urgent to design a new type of scavenger. SUMMARY

[0008] The application prepares a PDA / TEMPO NMs copolymer material, and emulsifies the copolymer material with various adjuvants to obtain a nanoemulsion, and the nanoemulsion has excellent free radical removal capacity and can effectively treat skin photoaging.

[0009] In a first aspect, the application provides a nanoemulsion for treating skin photoaging, wherein the main components of the nanoemulsion include PDA / TEMPO NMs nanoparticles, polyethylene glycol-6 monooleate, oil and surfactant.

[0010] Further, the PDA / TEMPO NMs nanoparticles are obtained by adding TEMPO during the polymerization of dopamine.

[0011] Further, the concentration ratio of TEMPO to dopamine is 1:6-10.

[0012] Preferably, the concentration ratio of TEMPO to dopamine is 1:8.

[0013] Further, the surfactant is selected from one or more of Tween-80, Tween-60, gelatin and / or polyoxyethylene hydrogenated castor oil.

[0014] Preferably, the surfactant is Tween-80.

[0015] Further, the oil is selected from one or more of soybean oil, sesame oil, tea oil, castor oil, olive oil and / or medium-chain triglyceride.

[0016] Preferably, the oil is medium-chain triglyceride.

[0017] Further, the ratio of PDA / TEMPO NMs nanoparticles, polyethylene glycol-6 monooleate, oil and surfactant in the nanoemulsion is 1:8-12:6-8:4-6.

[0018] The nanoemulsion of the present application achieves treatment of skin photoaging through the following (1-4) approaches:

[0019] (1) The PDA / TEMPO NMs nanoparticles themselves have the ability to scavenge free radicals;

[0020] (2) The donor-acceptor special structure formed after emulsification can achieve cyclic supply of PDA / TEMPO NMs E electrons inside and outside, so that the PDA / TEMPO NMs E surface always maintains a catechol-like structure, blocks the lipid peroxidation chain reaction, and improves the skin microenvironment;

[0021] (3) The emulsification structure formed after emulsification can improve the structural stability of DA / TEMPO NMs E, so that the affinity with alkoxy or alkylperoxy is increased;

[0022] (4) The emulsification structure formed after emulsification can improve the skin penetration ability of PDA / TEMPO NMs nanoparticles.

[0023] In a second aspect, the present application provides a preparation method of the nanoemulsion of the first aspect, and the method comprises the following steps:

[0024] S01, preparing polydopamine: adding water and ethanol to dopamine hydrochloride, and then adding ammonia water to react to obtain polydopamine;

[0025] S02, preparing PDA / TEMPO NMs nanoparticles: respectively dissolving TEMPO and dopamine hydrochloride in water, injecting the TEMPO solution into the dopamine hydrochloride solution to react to obtain PDA / TEMPO NMs nanoparticles;

[0026] S03, preparing PDA / TEMPO NMs E nanoemulsion: mixing the PDA / TEMPO NMs nanoparticles prepared in S02 with oil, and then sequentially adding polyethylene glycol-6 monooleate, surfactant, ethanol and water to obtain the PDA / TEMPO NMs nanoemulsion.

[0027] Further, in step S02, the PDA / TEMPO NMs nanoparticles have a new characteristic peak at 1352 cm -1 .

[0028] Further, in step S03, the PDA / TEMPO NMsE nanoemulsion has a particle size distribution of 80-100 nm, PDO<0.15, and a Zeta potential absolute value greater than 30 mV.

[0029] Further, in step S03, the surfactant is selected from one or more of Tween-80, Tween-60, gelatin, and / or polyoxyethylene hydrogenated castor oil.

[0030] Preferably, the surfactant is selected from Tween-80.

[0031] Further, the oil is selected from one or more of soybean oil, sesame oil, tea oil, castor oil, olive oil, and / or medium-chain triglyceride.

[0032] Preferably, the oil is selected from medium-chain triglyceride.

[0033] Further, in step S01, the mass ratio of dopamine hydrochloride, ethanol, and water is 1: 2-4: 2-4.

[0034] Further, in step S02, the concentration ratio of TEMPO to dopamine is 1:6-10.

[0035] Preferably, the concentration ratio of TEMPO to dopamine is 1:8.

[0036] Further, in step S03, the ratio of PDA / TEMPO NMs nano-material, medium-chain triglyceride, polyethylene glycol-6 monooleate, and Tween-80 is 1:8-12:6-8:4-6.

[0037] In a third aspect, the present application provides a use of the nanoemulsion of the first aspect in treating skin photoaging.

[0038] Further, the nanoemulsion is a PDA / TEMPO NMsE nanoemulsion.

[0039] Still further, the main components of the PDA / TEMPO NMsE nanoemulsion include PDA / TEMPO NMs material, polyethylene glycol-6 monooleate, oil, and surfactant.

[0040] Further, the skin photoaging is damage caused by long-term exposure of the skin to sunlight and is a result of the combined action of natural aging and ultraviolet radiation.

[0041] Beneficial effects

[0042] The PDA / TEMPO NMsE nanoemulsion prepared by the present application makes up for the insufficient efficiency of single PDA material in removing alkoxy and alkylperoxy free radicals. Among them, TEMPO forms a donor-acceptor special structure with PDA, so that the internal polydopamine of DA / TEMPO NMsE nanoemulsion can provide electrons to the external polydopamine through TEMPO, so that the surface of PDA / TEMPO NMsE nanoemulsion always maintains a catechol-like structure, solves the limitation of long-term repeated use of traditional antioxidants, and can significantly improve the removal efficiency and action time after single application, blocks the lipid peroxidation chain reaction to improve the skin microenvironment, thereby preventing the loss of skin collagen and elastic fibers.

[0043] In addition, the PDA / TEMPO NMsE nanoemulsion can block the lipid peroxidation chain reaction at the site of skin photoaging and effectively reduce the level of inflammatory mediators, and has more excellent treatment effect on skin photoaging than using retinoic acid or polydopamine, and can maintain the protection effect for a long time.

[0044] More importantly, the emulsified structure of PDA / TEMPO NMsE nanoemulsion can improve the structural stability of PDA / TEMPO NMsE, endow DA / TEMPO NMs nanoparticles with high affinity to alkoxy or alkylperoxy, and more easily remove such free radicals; in addition, the emulsified structure also enhances its transdermal performance through the intercellular pathway and the transcellular pathway of the stratum corneum, so that the material penetrates into the dermis layer of the skin to play a role in removing alkoxy free radicals; in particular, the biomimetic mussel characteristics endowed by the nanoemulsion structure also improve the residence time of the drug on the skin, maintain the effective concentration of the drug for a long time, and ultimately achieve long-acting treatment and protection of skin photoaging. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The Fourier transform infrared spectrograms of the prepared PDA / TEMPO NMs and PDA monomer nanoparticles.

[0046] Figure 2 The X-ray photoelectron spectrograms of the prepared PDA / TEMPO NMs and PDA monomer nanoparticles.

[0047] Figure 3 The Raman spectrograms of the prepared PDA / TEMPO NMs and PDA monomer nanoparticles.

[0048] Figure 4 The ultraviolet-visible spectrograms of the prepared PDA / TEMPO NMs and PDA monomer nanoparticles.

[0049] Figure 5TEM images of PDA / TEMPO (left) and PDA / TEMPO NMsE (right) nanodispersions.

[0050] Figure 6 Particle size distribution (A), Zeta potential (B) and particle size stability (C) of PDA / TEMPO NMsE.

[0051] Figure 7 Comparison of free radical scavenging performance of PDA / TEMPO NMsE with different concentrations.

[0052] Figure 8 Comparison of free radical scavenging performance of PDA, PDA / TEMPO NMs and PDA / TEMPO NMsE, p<0.05.

[0053] Figure 9 Changes in cellular level ROO· after treatment with PDA, PDA / TEMPO NMsE.

[0054] Figure 10 mRNA expression levels of LPS-stimulated macrophages after treatment with PDA, PDA / TEMPO NMs or PDA / TEMPO NMsE, p<0.05.

[0055] Figure 11 Effect of PDA / TEMPO NMsE on treating photoaging in mice, p<0.05. DETAILED DESCRIPTION

[0056] The specific embodiments of the present application are described below. It should be noted that the description of these embodiments is intended to help understand the present application, but does not constitute a limitation on the present application. In addition, the technical features involved in the following described embodiments can be combined with each other as long as they do not conflict with each other.

[0057] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0058] Terminology

[0059] In the present application, the "TEMPO" is "2,2,6,6-tetramethylpiperidine-N-oxide".

[0060] In the present application, the "PDA / TEMPO NMsE" is "PDA / TEMPO NMs nanoemulsion" or "PDA / TEMPO NMs nanoemulsion".

[0061] Example 1 Preparation of PDA / TEMPO NMsE nanoemulsion

[0062] PDA nanoparticles were prepared by a dissolution-oxidation method. 500 mg of dopamine hydrochloride was dissolved in a mixed solvent of 90 mL of deionized water and 40 mL of absolute ethanol, and stirred thoroughly; then 2.5 mL of 28%-30% ammonia water was added, and magnetic stirring was continued for 16 h; the resulting solution was centrifuged, and the precipitate was resuspended, precipitated and centrifuged alternately using deionized water and absolute ethanol, and the purified precipitate was dispersed in deionized water.

[0063] PDA / TEMPO NMs nanoparticles were synthesized by a one-pot method. 200 mg of dopamine hydrochloride was dissolved in 10 mL of deionized water and stirred thoroughly to prepare solution A; 200 mg of TEMPO was dissolved in 80 mL of deionized water and stirred thoroughly to prepare solution B; solution A was rapidly injected into solution B at room temperature, and magnetic stirring was continued; then high-speed centrifugation was performed, and the precipitate was resuspended, precipitated and centrifuged alternately using deionized water and absolute ethanol, and the purified precipitate was dispersed in 10 mL of deionized water to obtain a PDA / TEMPO NMs nanoparticle suspension.

[0064] PDA / TEMPO NMsE was synthesized by a self-emulsification method. 15 mL of medium-chain triglyceride was mixed and dissolved with 2 mL of PDA / TEMPO NMs. Then, 20 mL of polyethylene glycol-6 monooleate, 10 mL of Tween-80 and finally 30 mL of ethanol were sequentially added to the above solution and mixed thoroughly. 23 mL of deionized water was added dropwise to the above solution system at a rate of 5 mL / min while stirring, and after the dropwise addition was completed, stirring was continued for 30 min, and a semi-transparent PDA / TEMPO NMs nanoemulsion was obtained.

[0065] The polydopamine nanoparticles PDA and PDA / TEMPO NMs nanoparticles prepared above were subjected to Fourier infrared spectroscopy detection, and the results are shown in FIG. 1. A new characteristic peak at 1352 cm-1 is due to the stretching vibration of the N-O bond of the TEMPO moiety. Figure 1 X-ray photoelectron spectroscopy (XPS) analysis (see FIG. 2) was performed. Figure 2), the peaks of carbon-oxygen-nitrogen 1s orbit were observed in both PDA NPs and PDA NPs doped with TEMPO. The fine spectrum of carbon 1s mainly contained three kinds of carbon bonds, which were sp3-C (C-C) bond at 285 eV, C=0 bond at 288 eV and C-O / C-N bond at 286 eV. In the n1s spectrum, two peaks near 400 eV were attributed to C-N-C (pyridine nitrogen) and N-O, respectively, indicating the presence of TEMPO and pyridine ring. In addition, the o1s region peak near 532 eV corresponded to C=0 and C-O / N-O. Meanwhile, the Raman spectra of PDA and TPDA NPs (see Figure 3 ), showed that the single peak between 1600 cm -1 and 1520 cm -1 was attributed to the stretching vibration of benzene ring in dopamine, and the multiple peaks between 1340 cm -1 and 1280 cm -1 were composed of aldehyde bond in aldehyde hydrocarbon biomolecules. The UV-Vis spectra of several materials were also detected (see Figure 4 ), and it could be obviously seen that the doped materials showed stronger absorption.

[0066] PDA / TEMPO NMsE were characterized by transmission electron microscopy, surface potential (Zeta) and dynamic light scattering particle size instrument. In the transmission electron microscopy image (see Figure 5 ), compared with PDA / TEMPO NMs nanoparticles, PDA / TEMPO NMsE nanoemulsion had larger size and better dispersibility. The dynamic light scattering results showed (see Figure 6 ) that the particle size distribution of PDA / TEMPO NMsE was 120 nm and had good monodispersity, and PDI < 0.15. In addition, the absolute value of Zeta potential of PDA / TEMPO NMsE was greater than 30 mV, which proved that it had good colloidal stability. Within one month of room temperature storage, the size of PDA / TEMPO NMsE was stable at 80-100 nm, and no aggregation phenomenon occurred.

[0067] Example 2 Study on the performance of PDA / TEMPO NMsE in scavenging free radicals

[0068] ABTS and DPPH were used as the reaction substrates to evaluate the free radical scavenging performance of PDA / TEMPO NMsE nanoemulsion. PDA / TEMPO NMsE was prepared as a 1 mg / mL stock solution and further diluted to gradient concentration sample solutions; then mixed with ABTS radical or DPPH radical solution and incubated at 500 Hz, room temperature, in the dark for 1 h (blank control group was set); the sample's ABTS / DPPH radical scavenging efficiency was calculated according to the absorbance at 734 nm (corresponding to ABTS radical) or 517 nm (corresponding to DPPH radical). The results are shown in Figure 7 PDA / TEMPO NMsE exhibited high scavenging activity, and the activity was related to the concentration of PDA / TEMPO NMsE solution. As shown in Figure 8 Compared with PDA material (100 μg / mL) of the same concentration, the PDA / TEMPO NMsE's ABTS / DPPH radical scavenging efficiency was more than 2 times higher than that of PDA material.

[0069] The hydrogen peroxide-induced human skin fibroblast cell model was used to evaluate the material's ability to scavenge ROO· in cells. HSF cells were cultured in a confocal dish at a seeding density of 1000-2000 / well, incubated for 12 h, then the original culture medium was replaced with fresh cell culture medium containing PDA, PDA / TEMPO NMs, PDA / TEMPO NMsE material (200 μg / mL) or retinoic acid (VC), and hydrogen peroxide was added to make the final concentration in the well 1 mM, and the incubation was continued (at this time, 0 h). Then, at different time points (24 h, 48 h), ROO· probe working solution was added, and incubated in the incubator for 1 h in the dark. Finally, washed several times with PBS, added HBSS buffer and detected using a fluorescence microscope. As shown in Figure 9 The cell layer ROO· level was significantly reduced to the level of the retinoic acid treatment group after PDA / TEMPO NMsE treatment at 24 h, and the ROO· scavenging rate was increased by about 80% compared with the PDA treatment group; the PDA / TEMPO NMsE-treated cells maintained long-term strong ROO· scavenging activity at 48 h, while the retinoic acid-treated group's ROO· scavenging performance was significantly reduced at 48 h.

[0070] Example 3 Study on the efficacy of PDA / TEMPO NMsE in treating skin photoaging

[0071] The anti-inflammatory ability of the material was evaluated using an LPS-induced macrophage inflammation model. RAW264.7 cells were cultured in well plates at a seeding density of 150,000 cells / well and incubated for 12 h. Then, the original culture medium was replaced with fresh cell culture medium containing PDA, PDA / TEMPO NMs nanoparticles, and PDA / TEMPO NMsE material (200 μg / mL), and incubated for another 12 h. Subsequently, LPS was added to bring the final concentration in the wells to 100 ng / mL, and after incubation for 4 h, the culture medium was discarded. Cells were fully lysed using lysis buffer, and RNA was extracted. The RNA samples were then reverse transcribed, and the expression levels of IL-1β, TNF-α, and IL-6 in the samples were determined by quantitative real-time PCR.

[0072] A mouse model of photoaging was used to evaluate the therapeutic effect of PDA / TEMPO NMsE on photoaging. Female nude mice aged 10-12 weeks were irradiated with ultraviolet light (311 nm, 60 mJ / cm², 9 cm from the back) every other day for 9 weeks. On the first day of the ninth week, PDA / TEMPO NMs (20 mg / kg), PDA / TEMPO NMsE (20 mg / kg), and retinoic acid (2 mg / kg) were applied to the irradiated skin. The model group was given ethanol-propylene glycol as a solvent. After administration, macroscopic characteristics such as wrinkles, thickness, elasticity, and erythema in the irradiated skin were observed and recorded regularly. Transdermal water loss (TEWL) in the irradiated skin was measured using a multi-probe skin analyzer. After modeling, collagen content in the photoaged skin was analyzed.

[0073] The test results are as follows Figure 10 As shown, the experimental group treated with PDA / TEMPO NMsE exhibited the best inhibitory effect on the mRNA expression levels of inflammatory factors IL-1β, TNF-α, and IL-6 in stimulated cells. Eight days after PDA / TEMPO NMsE treatment, the skin water content and elastic fiber content of mice remained essentially at the levels of the sham-operated group (see...). Figure 11 The therapeutic effect of PDA / TEMPONMsE can be maintained for up to a week after administration, causing TEWL to continue to decrease to a level comparable to the sham surgery group and superior to PDA / TEMPON NMs nanoparticles without emulsification treatment; while the TEWL of the retinoic acid treatment group stopped decreasing 4-5 days after administration, indicating the time limitation of its therapeutic effect.

[0074] Based on the above cell experiments and animal model tests, the PDA / TEMPO NMsE nanoemulsion provided by this invention has an absolute advantage over existing technologies in the treatment of skin photoaging.

Claims

1. A nanoemulsion for treating photoaging of the skin, the main components of the nanoemulsion comprising PDA / TEMPO NMs nanoparticles, polyethylene glycol-6 monooleate, oil, and surfactant.

2. The nanoemulsion as described in claim 1, wherein the PDA / TEMPO NMs nanoparticles are obtained by adding TEMPO during the dopamine polymerization process.

3. The nanoemulsion according to claim 1, wherein the concentration ratio of TEMPO to dopamine is 1:6 to 10.

4. The nanoemulsion of claim 1, wherein the surfactant is selected from one or more of Tween-80, Tween-60, gelatin and / or polyoxyethylene hydrogenated castor oil, and the oil is selected from one or more of soybean oil, sesame oil, tea oil, castor oil, olive oil and / or medium-chain triglycerides.

5. The nanoemulsion as described in claim 1, wherein the ratio of PDA / TEMPO NMs nanoparticles, polyethylene glycol-6 monooleate, oil, and surfactant in the nanoemulsion is 1:8 to 12:6 to 8:4 to 6.

6. The nanoemulsion of claim 1, wherein the nanoemulsion achieves the treatment of skin photoaging through the following pathways (1-4): (1) The free radical scavenging properties inherent in PDA / TEMPO NMs nanoparticles; (2) The donor-acceptor special structure formed after emulsification can realize the cyclic supply of electrons inside and outside PDA / TEMPO NMsE, so that the surface of PDA / TEMPO NMsE always maintains a catechol-like structure, blocks the lipid peroxidation chain reaction, and improves the skin microenvironment. (3) After emulsification, an emulsion structure is formed, which can improve the structural stability of DA / TEMPO NMsE and increase the affinity with alkoxy or alkylperoxy groups. (4) After emulsification, an emulsion structure is formed, which can improve the skin penetration ability of PDA / TEMPO NMs nanoparticles.

7. A method for preparing the nanoemulsion as described in claim 1, the method comprising the following steps: S01, Preparation of polydopamine: Water and ethanol are added to dopamine hydrochloride, followed by the addition of ammonia to react and obtain polydopamine; S02, preparation of PDA / TEMPO NMs nanoparticles: dissolve TEMPO and dopamine hydrochloride in water respectively, inject the TEMPO solution into the dopamine hydrochloride solution for reaction, and obtain PDA / TEMPO NMs nanoparticles. S03, Preparation of PDA / TEMPO NMsE nanoemulsion: PDA / TEMPO NMs nanoparticles obtained in S02 are mixed with oil, and then polyethylene glycol-6 monooleate, surfactant, ethanol and water are added in sequence to obtain PDA / TEMPO NMs nanoemulsion.

8. The method of claim 7, wherein the PDA / TEMPO NMs nanoparticles are at 1352 cm⁻¹ -1 A new characteristic peak is present at the point where the PDA / TEMPO NMsE nanoemulsion has a particle size distribution of 80-100 nm, PDO < 0.15, and an absolute value of Zeta potential greater than 30 mV.

9. The use of the nanoemulsion as described in claim 1 in the treatment of photoaging of the skin.

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