Preparation method of peroxide-mediated high-ultraviolet-resistance melanin nano material
By using peroxide-mediated oxidative polymerization, a melanin nanomaterial with a regular structure and strong UV resistance was prepared, solving the problems of high cost and environmental unfriendliness of enzyme-catalyzed oxidative polymerization in existing technologies, and improving the stability and reproducibility of material properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-31
AI Technical Summary
Existing technologies for preparing melanin materials suffer from problems such as high cost of enzyme-catalyzed oxidative polymerization, violent and difficult-to-control reactions, introduction of impurity ions, and environmental unfriendliness, which affect the stability and reproducibility of the materials.
A peroxide-mediated method was used to generate well-structured poly-L-DOPA nanoparticles by mixing L-DOPA and benzoyl-containing peroxides under weakly acidic conditions and carrying out an oxidative polymerization reaction. The ultraviolet absorption performance was improved by benzoyloxy radical grafting and electrostatic interaction.
A melanin nanomaterial with a regular structure and strong UV resistance was prepared. The reaction process was mild and controllable, low in cost and environmentally friendly, and the stability and reproducibility of the material properties were improved.
Smart Images
Figure CN121758747A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of melanin materials technology, specifically to a method for preparing peroxide-mediated high UV-resistant melanin nanomaterials. Background Technology
[0002] Melanin is a class of biopolymer pigments widely found in living organisms (such as human skin, hair, and bird feathers). One of its most notable properties is its ability to effectively protect biological tissues from ultraviolet (UV) radiation damage by absorbing and scattering ultraviolet (UV) radiation. Inspired by this, the development of synthetic melanin materials with similar functions shows great potential for applications in sunscreen cosmetics, UV-resistant functional fibers, polymer stabilizers, and biomedicine.
[0003] Currently, the most classic method for preparing melanin materials is the oxidative polymerization route using tyrosine or its derivatives (such as dopamine) as monomers. This includes enzyme-catalyzed oxidative polymerization and chemical oxidative polymerization. Enzyme-catalyzed oxidative polymerization utilizes biological enzymes such as tyrosinase to catalyze the oxidative polymerization of tyrosine or dopamine; chemical oxidative polymerization uses strong oxidants such as periodate, potassium permanganate, copper sulfate / hydrogen peroxide (Fenton system), and ammonia / hydrogen peroxide to initiate polymerization under alkaline conditions.
[0004] Enzyme-catalyzed oxidative polymerization is a mild reaction, but enzymes are expensive and have poor stability. It is also difficult to completely remove enzyme residues after the reaction, which limits the application of this method in large-scale production and high-end materials. Although chemical oxidant oxidative polymerization can avoid the above-mentioned drawbacks of enzyme-catalyzed oxidative polymerization, it still has shortcomings: (1) Vigorous reaction and poor controllability: Strong oxidants can easily lead to an overly vigorous polymerization process, resulting in a wide molecular weight distribution and uneven morphology of the product, which affects the stability and reproducibility of the material properties; (2) Introduction of impurity ions: The introduced metal and / or inorganic ion residues are difficult to completely remove, which may not only affect the biocompatibility of the melanin material itself, but may also catalyze the photodegradation of the material during use, thus reducing its long-term stability; (3) Environmentally unfriendly: Some strong oxidants and their byproducts may impose a burden on the environment. Summary of the Invention
[0005] The purpose of this application is to provide a method for preparing peroxide-mediated high UV-resistant melanin nanomaterials. The method for preparing melanin materials in this application can avoid the drawbacks of the two methods mentioned in the background art, and the prepared melanin materials are high-quality melanin materials with regular structure and significantly enhanced UV resistance.
[0006] This application provides a method for preparing peroxide-mediated high UV-resistant melanin nanomaterials, including:
[0007] The levodopa solution was mixed with the peroxide solution and the pH of the solution was adjusted to 5-6. The mixture was stirred at room temperature to allow the levodopa to undergo an oxidative polymerization reaction, resulting in poly-levodopa nanoparticles.
[0008] The peroxide is a peroxide with a benzoyl group.
[0009] Optionally, the oxidative polymerization reaction time is 20h~30h.
[0010] Optionally, the levodopa solution is an aqueous solution of levodopa with a concentration of 2 mg / mL to 6 mg / mL.
[0011] Optionally, the solvent for the peroxide solution is an organic solvent with a concentration of 2 mg / mL to 12 mg / mL. The organic solvent may be an aliphatic hydrocarbon organic solvent (e.g., n-hexane, cyclohexane, petroleum ether, white oil, etc.), an aromatic hydrocarbon organic solvent (e.g., toluene, xylene, etc.), a halogenated hydrocarbon organic solvent (e.g., dichloromethane, chloroform, carbon tetrachloride, etc.), an ester organic solvent (e.g., ethyl acetate, butyl acetate, dibutyl phthalate (DBP), etc.), or a ketone organic solvent (e.g., acetone, butanone, etc.).
[0012] Optionally, the peroxide with a benzoyl group is tert-butyl peroxide, 3-chlorobenzoic acid peroxide, or benzoyl peroxide.
[0013] Optionally, the molar ratio of levodopa to peroxide is 1:1 to 5.
[0014] Preferably, the molar ratio of levodopa to peroxide is 1:3~5.
[0015] As a further preferred option, the molar ratio of levodopa to peroxide is 1:4~5.
[0016] The melanin film provided in this application is a film-like material in which poly-L-DOPA nanoparticles prepared by the above preparation method are dispersed in a film-forming carrier.
[0017] Optionally, the mass percentage of poly-L-DOPA nanoparticles in the melanin film is 0.02% to 0.06%.
[0018] Optionally, the film-forming carrier is polyvinyl alcohol, polyvinyl chloride, polyurethane, polyacrylate or epoxy resin.
[0019] Organic peroxide molecules contain peroxide bonds (-OO-). Due to the instability of peroxide bonds, organic peroxides are generally considered to possess both strong oxidizing and free radical initiation activity, and theoretically can be used to initiate the oxidative polymerization of the melanin precursor L-DOPA. During the research and development of this application, various organic peroxides (see Table 1 below) were selected for mixed reactions with L-DOPA. It was found that when the organic peroxide is a peroxide with a benzoyl group, a better polymerization effect is achieved.
[0020] Therefore, this application selects peroxides with benzoyl groups. The peroxy bond in benzoyl peroxides can be broken at room temperature, while levodopa has reducing properties. In the reaction solution, the two undergo a redox reaction at room temperature, thereby promoting the oxidative self-polymerization of levodopa to generate poly-levodopa nanoparticles, i.e., melanin nanoparticles. The benzoyloxy radicals generated during the reaction can further oxidize levodopa and even replace the ortho-hydrogen of the levodopa hydroxyl group, thus integrating into the poly-levodopa system.
[0021] The incorporation of benzoyloxy radicals into the poly-L-DOPA system increases its band gap, which helps reduce the degree of intramolecular cyclization. Furthermore, in a weakly acidic environment, L-DOPA exists as a zwitterion, forming an intramolecular salt. This salt, through strong electrostatic interactions, immobilizes ammonium ions, making intramolecular cyclization difficult after L-DOPA oxidation. Reduced intramolecular cyclization weakens the conjugation effect in the poly-L-DOPA system, thus enhancing its ultraviolet absorption.
[0022] Compared with the prior art, this application has the following advantages and beneficial effects:
[0023] The preparation method of this application has the advantages of mild and controllable reaction process, low cost and environmental friendliness; the melanin nanoparticles prepared in this application have benzoyl groups grafted on them, the melanin nanoparticles have regular structure and excellent anti-ultraviolet properties. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0025] Figure 1 Photographs of solutions containing different organic peroxides and levodopa in Example 1;
[0026] Figure 2 A scanning electron microscope image of the control group sample P(L-DOPA)-0;
[0027] Figure 3 This is a scanning electron microscope image of sample P(L-DOPA)-4;
[0028] Figure 4 Here is the high-resolution mass spectrum of sample P(L-DOPA)-4;
[0029] Figure 5 Fourier transform infrared spectra of benzoyl peroxide, control sample P(L-DOPA)-0, and sample P(L-DOPA)-4;
[0030] Figure 6 The X-ray photoelectron spectrum of the control group sample P(L-DOPA)-0;
[0031] Figure 7 The X-ray photoelectron spectrum of sample P(L-DOPA)-4 is shown below.
[0032] Figure 8 The UV-Vis absorption spectra of control sample P(L-DOPA)-0 and samples P(L-DOPA)-1, P(L-DOPA)-2, P(L-DOPA)-3, P(L-DOPA)-4, and P(L-DOPA)-5 are shown.
[0033] Figure 9 shows photographs of thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4;
[0034] Figure 10 Fourier transform infrared spectra of thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4;
[0035] Figure 11 The light transmittance curves for thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4 are shown.
[0036] Figure 12 The UV-Vis absorption spectra of the thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4 are shown.
[0037] Figure 13 Photodegradation curves of RhB solutions coated with membranes;
[0038] Figure 14 Stress-strain diagrams for thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4;
[0039] Figure 15Thermogravimetric analysis (TGA) diagrams for thin film samples PVA, PVA@P(L-DOPA)-0, and PVA@P(L-DOPA)-4 are shown. Detailed Implementation
[0040] The technical solutions and effects of this application will be clearly and completely described below with reference to specific embodiments, examples, and comparative examples. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0041] In the following examples, the levodopa and organic peroxides used were all commercially available products manufactured by Shanghai Adamas Reagent Co., Ltd.
[0042] Example 1
[0043] In this embodiment, the solutions of the organic peroxides listed in Table 1 were mixed with the L-DOPA solution and stirred. The polymerization effect of L-DOPA was judged by observing the color change of the mixed solution.
[0044] The specific steps of this embodiment are as follows:
[0045] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0046] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to peroxide of 1:4, calculate the mass of peroxide and dissolve the peroxide in 30 mL of acetone.
[0047] (3) Mix the levodopa solution and the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours.
[0048] Please see Figure 1 The image shows a photograph of the solution after mixing different organic peroxides with levodopa and stirring for 24 hours in this embodiment. The organic peroxides corresponding to the images from left to right are tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,5-bis(tert-butyl)-2,5-dimethylhexane, 1,1-bis(tert-butylperoxy)cyclohexane, di-tert-butyl peroxide isopropylbenzene, tert-butyl peroxide, 3-chlorobenzoic acid peroxide, and benzoyl peroxide.
[0049] from Figure 1It can be seen that when the peroxide is a peroxide with a benzoyl group, the solution color changes significantly, indicating that the polymerization of levodopa has occurred; among them, the mixed solution of benzoyl peroxide and levodopa is the darkest, indicating that benzoyl peroxide has the best polymerization effect on levodopa.
[0050] Table 1 List of organic peroxides in Example 1
[0051] Example 2
[0052] In this embodiment, benzoyl peroxide is used as the peroxide to prepare poly-L-DOPA nanoparticles. The specific steps are as follows:
[0053] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0054] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to benzoyl peroxide being 1:1, calculate the mass of benzoyl peroxide and dissolve benzoyl peroxide in 30 mL of acetone.
[0055] (3) Mix the L-DOPA solution with the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours. Then, centrifuge the solution to separate the poly-L-DOPA nanoparticles and dry them. The resulting product is recorded as sample P(L-DOPA)-1.
[0056] Example 3
[0057] In this embodiment, benzoyl peroxide is used as the peroxide to prepare poly-L-DOPA nanoparticles. The specific steps are as follows:
[0058] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0059] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to benzoyl peroxide of 1:2, calculate the mass of benzoyl peroxide and dissolve benzoyl peroxide in 30 mL of acetone.
[0060] (3) Mix the L-DOPA solution with the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours. Then, centrifuge the solution to separate the poly-L-DOPA nanoparticles and dry them. The resulting product is recorded as sample P(L-DOPA)-2.
[0061] Example 4
[0062] In this embodiment, benzoyl peroxide is used as the peroxide to prepare poly-L-DOPA nanoparticles. The specific steps are as follows:
[0063] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0064] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to benzoyl peroxide of 1:3, calculate the mass of benzoyl peroxide and dissolve benzoyl peroxide in 30 mL of acetone.
[0065] (3) Mix the L-DOPA solution with the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours. Then, centrifuge the solution to separate the poly-L-DOPA nanoparticles and dry them. The resulting product is recorded as sample P(L-DOPA)-3.
[0066] Example 5
[0067] In this embodiment, benzoyl peroxide is used as the peroxide to prepare poly-L-DOPA nanoparticles. The specific steps are as follows:
[0068] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0069] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to benzoyl peroxide of 1:4, calculate the mass of benzoyl peroxide and dissolve benzoyl peroxide in 30 mL of acetone.
[0070] (3) Mix the L-DOPA solution with the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours. Then, centrifuge the solution to separate the poly-L-DOPA nanoparticles and dry them. The resulting product is recorded as sample P(L-DOPA)-4.
[0071] Example 6
[0072] In this embodiment, benzoyl peroxide is used as the peroxide to prepare poly-L-DOPA nanoparticles. The specific steps are as follows:
[0073] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0074] (2) Preparation of peroxide solution: Based on the molar ratio of levodopa to benzoyl peroxide of 1:5, calculate the mass of benzoyl peroxide and dissolve benzoyl peroxide in 30 mL of acetone.
[0075] (3) Mix the L-DOPA solution with the peroxide solution, adjust the pH of the solution to 6, and stir for 24 hours. Then, centrifuge the solution to separate the poly-L-DOPA nanoparticles and dry them. The resulting product is recorded as sample P(L-DOPA)-5.
[0076] Example 7
[0077] In this embodiment, control groups corresponding to Examples 2-6 were prepared, and the specific steps are as follows:
[0078] (1) Preparation of levodopa solution: Dissolve 40 mg of levodopa in 10 mL of deionized water to prepare a levodopa solution with a concentration of 4 mg / mL;
[0079] (2) Keep the levodopa solution at 75°C for 24 hours, then centrifuge the solution to separate the product and dry it. The product obtained is recorded as the control sample P(L-DOPA)-0.
[0080] Please see Figures 2-3 The images show scanning electron microscope (SEM) images of control sample P(L-DOPA)-0 and sample P(L-DOPA)-4, respectively. It can be seen from the images that sample P(L-DOPA)-4 consists of nano-sized particles with regular morphology.
[0081] Please see Figure 4 The image shows the high-resolution mass spectrum of sample P(L-DOPA)-4. The spectrum shows that the benzoyloxy radical produced by the decomposition of benzoyl peroxide replaces the hydrogen at the ortho and para positions of the phenolic hydroxyl group in poly-L-DOPA, indicating that the benzoyloxy radical is grafted onto poly-L-DOPA.
[0082] Please see Figure 5 The figure shows the Fourier transform infrared (FTIR) spectra of benzoyl peroxide, control sample P(L-DOPA)-0, and sample P(L-DOPA)-4. As can be seen from the figure, compared with the control sample P(L-DOPA)-0, the ultraviolet absorption performance of sample P(L-DOPA)-4 is significantly enhanced. The inventors analyzed that the mechanism of this significant enhancement in ultraviolet absorption performance may be: the introduction of benzoyl oxygen free radicals increases the band gap of poly-L-DOPA, reduces the degree of internal cyclization of the polymer molecule, thereby reducing the degree of conjugation, resulting in a blue shift in the absorption spectrum, accompanied by enhanced ultraviolet absorption.
[0083] Please see Figures 6-7 The figures shown are the X-ray photoelectron spectra (XPS spectra) of the control group sample P(L-DOPA)-0 and the sample P(L-DOPA)-4, respectively. Both XPS spectra are peak profiles of nitrogen (i.e., XPS N1s spectra). Comparison... Figures 6-7 It can be seen that, compared with the control group sample P(L-DOPA)-0, the degree of internal cyclization of sample P(L-DOPA)-4 is reduced.
[0084] Please see Figure 8The figure shows the UV-Vis absorption spectra of the control group sample P(L-DOPA)-0 and samples P(L-DOPA)-1, P(L-DOPA)-2, P(L-DOPA)-3, P(L-DOPA)-4, and P(L-DOPA)-5. It can be seen from the figure that sample P(L-DOPA)-4 has the best UV absorption performance in the UV region.
[0085] Example 8
[0086] In this embodiment, sample P(L-DOPA)-4 was used to prepare an anti-ultraviolet melanin film. Specifically, 10 mL of a 100 mg / mL PVA aqueous solution was taken, and 4 mg of powdered sample P(L-DOPA)-4 was added to the PVA aqueous solution and stirred for 30 min. Then, the mixture was poured into a mold and dried at 60°C. After demolding, a melanin film with a thickness of about 0.1 mm was obtained, which was denoted as film sample PVA@P(L-DOPA)-4 Film.
[0087] Example 9
[0088] In this embodiment, the control group sample P(L-DOPA)-0 was used to prepare an anti-ultraviolet melanin film. Specifically, 10 mL of a 100 mg / mL PVA aqueous solution was taken, and 4 mg of powdered control group sample P(L-DOPA)-0 was added to the PVA aqueous solution and stirred for 30 min. Then, the mixture was poured into a mold and dried at 60°C. After demolding, a melanin film with a thickness of about 0.1 mm was obtained, which was denoted as the film sample PVA@P(L-DOPA)-0 Film.
[0089] Please refer to Figure 9, where Figures (a), (b), and (c) are photographs of the film samples PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film, respectively. The PVA Film sample is a PVA film without added melanin, which is prepared by pouring 10 mL of a 100 mg / mL PVA aqueous solution into a mold and drying it at 60°C. After demolding, a PVA Film sample with a thickness of about 0.1 mm is obtained.
[0090] The UV resistance properties of PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film were characterized. Figure 10 The Fourier transform infrared spectra of the thin film samples PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film are shown below. Figure 11The light transmittance curves are shown for the thin film samples PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film. Figure 12 The images show the UV-Vis absorption spectra of the thin film samples: PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film. Figures 10-12 It can be seen that the PVA@P(L-DOPA)-4 Film sample has the best UV protection performance.
[0091] UV dye degradation resistance experiments were conducted on PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film samples. Figure 13 The graph shows the photodegradation curve of the RhB solution coated with a membrane. RhB is the classic fluorescent dye Rhodamine B. The horizontal axis t represents the UV irradiation time, and the vertical axis A... t In / A0, A0 represents the initial absorbance of the RhB solution, A t A represents the absorbance of the RhB solution after irradiation with ultraviolet light for time t. t / A0 is used to characterize the efficiency of ultraviolet protection. Figure 13 The photodegradation curves further verified that the PVA@P(L-DOPA)-4 Film sample has excellent UV resistance.
[0092] The above-mentioned experiment on resistance to UV dye degradation specifically included: 10 mL of RhB aqueous solution with a concentration of 10 mg / L was placed in the sample bottle; 5 mg of titanium dioxide was added to the sample bottle and stirred in the dark for half an hour. Before UV irradiation, the bottle opening was covered with PVA film, PVA@P(L-DOPA)-0 film, and PVA@P(L-DOPA)-4 film, respectively. Subsequently, the bottle opening was irradiated with a UV lamp at a wavelength of 365 nm, with the lamp 8 cm away from the bottle opening. At UV irradiation time t, 1 mL of the solution in the bottle was centrifuged to remove titanium dioxide. Then, the absorbance A of the RhB solution at 552 nm was measured using a UV-Vis spectrophotometer. t And calculate A t / A0, where A0 is the absorbance of the RhB solution before it is exposed to ultraviolet light.
[0093] Please see Figure 14The figure shows the stress-strain diagrams of the film samples PVA Film, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film. It can be seen from the figure that the incorporation of melanin nanoparticles can reduce the tensile strength of the film samples. The inventors analyzed that the incorporation of melanin may weaken the hydrogen bonding effect inside the PVA film. Figure 15 The thermogravimetric analysis (TGA) diagrams of the thin film samples PVAFilm, PVA@P(L-DOPA)-0 Film, and PVA@P(L-DOPA)-4 Film are shown. As can be seen from the diagrams, the addition of melanin nanoparticles can significantly enhance the thermal stability of the thin film samples.
[0094] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for preparing peroxide-mediated high ultraviolet resistant black pigment nanomaterials, characterized in that, The preparation method comprises the following steps: Mixing a levodopa solution with a peroxide solution and adjusting the pH value of the solution to 5-6, keeping stirring at room temperature to make the levodopa undergo an oxidative polymerization reaction to obtain poly-levodopa nanoparticles; The peroxide is a benzoyl-containing peroxide.
2. The preparation method of claim 1, wherein: The oxidative polymerization reaction time is 20-30 hours.
3. The preparation method of claim 1, wherein: The benzoyl-containing peroxide is tert-butyl peroxybenzoate, 3-chloro peroxybenzoic acid or benzoyl peroxide.
4. The preparation method of claim 1, wherein: The molar ratio of levodopa to peroxide is 1:1-5.
5. The preparation method of claim 1, wherein: The molar ratio of levodopa to peroxide is 1:3-5.
6. The preparation method of claim 1, wherein: The molar ratio of levodopa to peroxide is 1:4-5.
7. A melanin film, wherein: The poly-levodopa nanoparticles prepared by the preparation method of any one of claims 1-6 are dispersed in a film-shaped material of a film-forming carrier.
8. The melanin film of claim 7, wherein: The mass proportion of the poly-levodopa nanoparticles in the melanin film is 0.02%-0.06%.
9. The melanin film of claim 7, wherein: The film-forming carrier is polyvinyl alcohol, polyvinyl chloride, polyurethane, polyacrylate or epoxy resin.