Sulfur-containing polydopamine melanin nanoparticle, preparation method and application thereof

Abstract

The application discloses a kind of sulphur-containing polydopamine melanin nanoparticles and preparation method and application, preparation raw materials include polyhydroxy compound and sulphur-containing compound, the weight ratio of the polyhydroxy compound and the sulphur-containing compound is (1-100) :(1-100), the preparation raw materials also include water, organic solvent and acid-base regulator.The application occurs self-polymerization reaction under alkaline condition with dopamine and sulphur-containing compound, without additional crosslinking agent and oxidant, and the nanoparticles obtained have excellent photothermal performance.In photothermal therapy, biomedical imaging, water purification, functional coating and other aspects, it shows great application potential.And preparation reaction condition is mild, without additional catalyst and oxidant, process is safe, post-processing is simple, and no harmful waste water and waste residue to environment, meet the requirements of green chemistry.

Description

Technical Field

[0001] This invention relates to the field of compositions for polymers, and more specifically to a sulfur-containing polydopamine melanin nanoparticle, its preparation method, and its application. Background Technology

[0002] Melanin plays crucial roles in nature and organisms, including pigmentation, structural coloration, photoprotection, radiation absorption, and thermoregulation. The application of polydopamine in melanin preparation shows great potential in photothermal therapy, biomedical imaging, water purification, and functional coatings. However, introducing heterostructures into polydopamine can disrupt its internal macromolecular structure. Therefore, developing a polydopamine-melanin composite material with excellent photothermal properties that does not affect the compatibility of melanin within the polymer is crucial.

[0003] Chinese invention patent CN108383765B discloses a synthesis of chlorambucil-dopamine conjugate and the preparation of prodrug nanoparticles. First, ethyl 2-(2-hydroxyethyl)dithio)ethyl-2,2-dimethyl-1,3-benzodioxane-pentene-5-propionate is synthesized, then the chlorambucil-dopamine conjugate is synthesized, and finally, chlorambucil-polydopamine prodrug nanoparticles are synthesized, resulting in a polymeric drug carrier with near-infrared light absorption, reduction responsiveness, and integrated photothermal therapy and chemotherapy. However, the process is complex. Chinese invention patent CN107510842B discloses a method for preparing a clean composite photothermal agent with excellent photothermal effects. Uniform polydopamine nanoparticles are prepared through a fully reactive oxidative self-polymerization reaction. A sulfide is added as a sulfur source, and after a fully reactive reaction, composite microspheres loaded with CuS on a PDA are prepared. This method exhibits good photothermal effects, is environmentally friendly, and produces clean products. However, its compatibility with polymers is poor, making it unsuitable for use in polymer films. Summary of the Invention

[0004] In order to develop a polydopamine melanin composite material with excellent photothermal properties and without affecting the compatibility of melanin in polymers, the first aspect of the present invention provides sulfur-containing polydopamine melanin nanoparticles, the raw materials for preparation including a polyhydroxy compound and a sulfur-containing compound, wherein the weight ratio of the polyhydroxy compound and the sulfur-containing compound is (1-100):(1-100), and the raw materials for preparation also include water, organic solvent and acid-base regulator.

[0005] In one embodiment, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-50):(1-50).

[0006] In one embodiment, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-25):(1-25).

[0007] In one embodiment, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-10):(1-10).

[0008] In one embodiment, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-5):(1-5).

[0009] In one embodiment, the weight ratio of the polyhydroxy compound to the sulfur-containing compound includes 1:1, 1:2, 1:3, 1:4, 1:5, 2:1, 2:2, 2:3, 2:4, 2:5, etc.

[0010] In one embodiment, the sulfur-containing compound includes at least one of thiocyclic compounds, thiol compounds, and polysulfide compounds.

[0011] In one embodiment, the sulfide ring compound includes at least a disulfide five-membered ring compound.

[0012] In one embodiment, the disulfide pentacyclic compound includes at least one of disulfide pentacyclic carboxylic acids and their derivatives, and disulfide pentacyclic amides and their derivatives.

[0013] As one embodiment, the structural formula of the disulfide five-membered ring carboxylic acid and its derivatives is shown in Formula 1 or Formula 2:

[0014] Formula 1 or Formula 2; In Formula 1 or Formula 2, R1 and R3 each include one of hydrogen, C1-C4 straight-chain alkyl, or C1-C4 branched alkyl; R2 and R4 each include one of hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, or carboxyl, and a and b are both integers from 1 to 6.

[0015] As one embodiment, the structural formula of the disulfide five-membered ring carboxylic acid and its derivatives includes, but is not limited to, the following structural formulas:

[0016] .

[0017] As one embodiment, the structural formula of the disulfide pentaneous amide and its derivatives is shown in Formula 3 or Formula 4:

[0018] Formula 3 or Equation 4; R5-R9 and R in Equation 3 or Equation 4 15 -R 19 All include one of hydrogen, C1-C4 straight-chain alkyl, or C1-C4 branched alkyl; R 10 -R 14 and R 20 -R 24All include one of hydrogen, hydroxyl or methyl; c and d are integers from 1 to 6, and e and f are integers from 1 to 3.

[0019] As one embodiment, the structural formulas of the disulfide pentaneous amide and its derivatives include, but are not limited to, the following structural formulas:

[0020]

[0021] .

[0022] In one embodiment, the thiocyclic compound further includes the following structural formula, as shown in Formula 5 or Formula 10:

[0023] Formula 5 Formula 6 Formula 7 Formula 8 Formula 9 Equation 10; R in Equation 5 or Equation 10 25 -R 30 Including but not limited to hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, hydroxyl, carboxyl, mercapto, phenyl or amino.

[0024] In one embodiment, the sulfide compound also includes, but is not limited to, the following structural formulas:

[0025] .

[0026] As one embodiment, the structural formula of the thiol compound is shown in Formula 11: Equation 11; R in Equation 11 31 and R 32 All of these include, but are not limited to, one of hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched alkyl, hydroxyl, carboxyl, mercapto, phenyl or amino, where n is an integer from 1 to 10.

[0027] As one embodiment, the structural formula of the thiol compound includes, but is not limited to, the following structural formulas:

[0028] .

[0029] As one embodiment, the polysulfide compound has the structural formula S g g is an integer between 2 and 20.

[0030] As one embodiment, the structural formula of the polysulfide compound includes, but is not limited to, the following structural formulas:

[0031] .

[0032] In one embodiment, the polyhydroxy compound includes at least one of dopamine, catechol, or a catechol derivative.

[0033] As one embodiment, the structural formula of the catechol derivative is shown in Formula 12:

[0034] Equation 12, R in Equation 12 33 Includes one of hydrogen, C1-C4 straight-chain alkyl, or C1-C4 branched alkyl; R 34 -R 35 It includes one of hydrogen, amino, carboxyl or amide, where m is an integer from 1 to 3.

[0035] In one embodiment, the acid-base regulator is at least one of an organic alkaline substance and an inorganic alkaline substance.

[0036] In one embodiment, the organic alkaline substance includes, but is not limited to, at least one of methylamine, ethylamine, triethylamine, aniline, pyridine, imidazole, or tetramethylammonium hydroxide; the inorganic alkaline substance includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide, ammonia, sodium carbonate, or sodium bicarbonate.

[0037] As one embodiment, the organic solvent includes, but is not limited to, at least one of ethanol, acetonitrile, acetone, tetrahydrofuran, dimethylformamide, or dimethyl sulfoxide.

[0038] A second aspect of the present invention provides a method for preparing sulfur-containing polydopamine melanin nanoparticles, comprising the following steps:

[0039] Dissolve the polyhydroxy compound in water and stir at room temperature for 1-10 minutes to obtain an aqueous solution of the polyhydroxy compound;

[0040] A sulfur-containing compound is dissolved in an organic solvent to obtain a sulfur-containing compound solution;

[0041] The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, stirred until homogeneous, and the pH was adjusted to 8-9 with an acid-base adjuster. The reaction was carried out at room temperature.

[0042] After the reaction was completed, the supernatant was discarded by centrifugation to obtain the lower layer. The lower layer was washed and then freeze-dried to obtain the melanin nanoparticles.

[0043] In one embodiment, the room temperature reaction time is 16-24 hours.

[0044] In one embodiment, the concentration of the aqueous solution of the polyhydroxy compound is 0.001-0.01 g / mL; the concentration of the sulfur-containing compound solution is 0.005-0.01 g / mL.

[0045] In one embodiment, the concentration of the aqueous solution of the polyhydroxy compound is 0.003-0.008 g / mL; and the concentration of the sulfur-containing compound solution is 0.005-0.008 g / mL.

[0046] In one embodiment, the concentration of the aqueous solution of the polyhydroxy compound is 0.0055 g / mL; and the concentration of the sulfur-containing compound solution is 0.00625 g / mL.

[0047] The inventors discovered during experiments that melanin nanoparticles formed by the reaction of sulfur-containing compounds with dopamine exhibit superior photothermal conversion performance, far exceeding the total photothermal efficiency of traditional polydopamine nanoparticles. This is because sulfur atoms graft onto polydopamine via a Michael addition reaction. The introduction of electron donor sulfur atoms and electron acceptor carboxyl groups constructs a donor-acceptor microstructure within the melanin nanoparticles, effectively reducing the molecular energy level gap and promoting electron transfer. Simultaneously, the intermolecular conjugation is disrupted, preventing the formation of large aggregates and increasing the concentration of free radicals, thus limiting non-thermal radiation conversion. The combined effect of these two factors enhances the light absorption and photothermal conversion efficiency of the sulfur-containing nanoparticles.

[0048] A third aspect of the present invention provides an application of sulfur-containing polydopamine melanin nanoparticles in the preparation of polymer films with photothermal properties.

[0049] As one embodiment, the method for preparing the polymer film with photothermal properties includes the following steps:

[0050] Sulfur-containing polydopamine melanin nanoparticles were mixed with a solvent, and then a polymer was added. The mixture was stirred and dispersed evenly, and then a film was formed. The film was transferred into a mold, allowed to stand, and the solvent was allowed to evaporate to obtain a polymer film with photothermal properties.

[0051] In one embodiment, the weight ratio of the sulfur-containing polydopamine melanin nanoparticles to the polymer is (0.1-0.5):1.

[0052] As one implementation method, the film-forming method includes, but is not limited to, static film formation, room temperature pressing film formation, hot pressing film formation, or aging film formation.

[0053] In one embodiment, the polymer includes, but is not limited to, at least one of the following: polymethyl methacrylate, polyurethane, polyethylene, polystyrene, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyimide, polyoxymethylene, polyphenylene sulfide, polysulfone, polyethersulfone, polyaryletherketone, liquid crystal polymer, polyphthalamide, polybenzimidazole fiber, polylactic acid, polycarbonate, polyvinyl alcohol, polyacrylamide, polyetheretherketone, polyetherketoneketone, polytetrafluoroethylene, polythioctic acid, epoxy resin, cellulose, starch, or chitosan.

[0054] During the experiment, the inventors discovered that the prepared sulfur-containing polydopamine melanin nanoparticles exhibited good compatibility with polymers and maintained excellent photothermal properties. This is because the abundant carboxyl hydrogen bonds and dynamic disulfide sites on the surface of the sulfur-containing polydopamine melanin nanoparticles enable covalent and non-covalent interactions between the particles and the polymer matrix. These interactions act as nano-crosslinking agents to construct a high-performance dynamic crosslinked polymer network, thereby giving the sulfur-containing polydopamine melanin nanoparticles excellent compatibility in different polymer matrices. This effectively enhances interfacial photothermal conversion and heat transfer, thus achieving efficient, light-controlled, real-time self-healing.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The sulfur-containing polydopamine melanin nanoparticles of the present invention are obtained by self-polymerization of dopamine and sulfur-containing compounds under alkaline conditions without the need for additional crosslinking agents and oxidants, and the resulting nanoparticles have excellent photothermal properties.

[0057] (2) The sulfur-containing polydopamine melanin nanoparticles and polymers described in this invention are in a weight ratio of (0.01-0.05):1. The amount of melanin nanoparticles added is low, the cost is reduced, and the compatibility with polymers is excellent.

[0058] (3) The sulfur-containing polydopamine melanin nanoparticles of the present invention can construct a high-performance dynamic cross-linked polymer network in the polymer, which effectively enhances the interfacial photothermal conversion and heat transfer, thereby realizing efficient light-controlled real-time self-healing.

[0059] (4) The preparation method of sulfur-containing polydopamine melanin nanoparticles of the present invention has mild reaction conditions, no need to add additional catalysts and oxidants, safe process, simple post-treatment, and does not produce wastewater and waste residue that are harmful to the environment, which meets the requirements of green chemistry.

[0060] (5) The sulfur-containing polydopamine melanin nanoparticles of the present invention are prepared from raw materials that are beneficial to the human body, have good biocompatibility, are widely available, inexpensive and readily available, and have industrial feasibility. They show great application potential in photothermal therapy, biomedical imaging, water purification, functional coatings and other fields. Attached Figure Description

[0061] Figure 1 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 The appearance of polydopamine (PDA) nanoparticles (top left) and their scanning electron microscope image (bottom left), and the appearance of polydopamine (PDA) nanoparticles (top right) and their scanning electron microscope image (bottom right).

[0062] Figure 2 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 X-ray diffraction (XRD) pattern of the sample.

[0063] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 of this invention; from top to bottom, the images show polydopamine (PDA) nanoparticles, sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)... 125 ), thioctic acid (TA).

[0064] Figure 4 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 X-ray photoelectron spectroscopy of sulfur in ))

[0065] Figure 5 X-ray photoelectron spectroscopy of sulfur in thioctic acid (TA).

[0066] Figure 6 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 The ultraviolet-visible-near-infrared absorption and transmission spectra of polydopamine (PDA).

[0067] Figure 7 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 Polydopamine nanoparticles (PDA) at 808 nm wavelength, 1 W / cm 2 Power, aqueous phase photothermal conversion data under 100 μg / mL concentration conditions.

[0068] Figure 8 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 )) and polydopamine (PDA) nanoparticles at 808 nm wavelength, 1 W / cm 2 Photothermal cycling data at power and concentration of 100 μg / mL.

[0069] Figure 9 This is a schematic diagram of the time-temperature superimposed rheological curve of a polythiooctanoic acid (PTA) film.

[0070] Figure 10 A schematic diagram of the time-temperature superimposed rheological curve of a thin film prepared by photopolymerization of polydopamine nanoparticles (PDA) and thioctic acid after melting.

[0071] Figure 11 The sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA)) prepared in Example 1.1 of this invention 125 A schematic diagram of the time-temperature superimposed rheological curve of a thin film prepared by photopolymerization of thioctic acid after melting.

[0072] Figure 12 The top row, from left to right, shows schematic diagrams of polymer films prepared by incorporating polydopamine (PDA) into polyacrylamide (PAM), polymethyl methacrylate (PMMA), polyurethane (PU), polyvinyl alcohol (PVA), polyethylene (PE), polycarbonate (PC), and bisphenol A type epoxy resin (DGEBA). The bottom row, from left to right, shows schematic diagrams of polymer films prepared by incorporating sulfur-containing polydopamine melanin nanoparticles into polyacrylamide (Application Example 2), polymethyl methacrylate (Application Example 3), polyurethane (Application Example 5), polyvinyl alcohol (Application Example 6), polyethylene (Application Example 8), polycarbonate (Application Example 4), and bisphenol A type epoxy resin (Application Example 7), as described in Example 1.1 of this invention. Detailed Implementation

[0073] Example 1.1

[0074] A sulfur-containing polydopamine melanin nanoparticle is prepared from raw materials including a polyhydroxy compound and a sulfur-containing compound, wherein the weight ratio of the polyhydroxy compound to the sulfur-containing compound is 2:1, and the raw materials also include water, an organic solvent and an acid-base regulator.

[0075] The polyhydroxy compound is dopamine hydrochloride, the sulfur-containing compound is lipoic acid, the organic solvent is anhydrous ethanol, and the acid-base regulator is ammonia.

[0076] A method for preparing sulfur-containing polydopamine melanin nanoparticles includes the following steps:

[0077] Dissolve 3g of the polyhydroxy compound in 540mL of water and stir at room temperature for 5min to obtain an aqueous solution of the polyhydroxy compound;

[0078] 1.5g of a sulfur-containing compound was dissolved in 240mL of organic solvent to obtain a sulfur-containing compound solution;

[0079] The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, and the mixture was stirred for 30 minutes until the solution was completely mixed. The pH was adjusted to 8.5 by adding an acid-base adjuster, and the reaction was carried out at room temperature for 24 hours.

[0080] After the reaction was completed, the supernatant was discarded by centrifugation at 8000 rpm for 5 min, and the lower layer was obtained. The lower layer was washed three times and then freeze-dried under vacuum to obtain the melanin nanoparticles P(TA1-DA). 125 ).

[0081] Example 1.2

[0082] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as in Example 1.1, except that the weight ratio of the polyhydroxy compound and the sulfur-containing compound is 10:1.

[0083] A method for preparing sulfur-containing polydopamine melanin nanoparticles includes the following steps:

[0084] Dissolve 3g of the polyhydroxy compound in 540mL of water and stir at room temperature for 5min to obtain an aqueous solution of the polyhydroxy compound;

[0085] 0.3g of the sulfur-containing compound was dissolved in 240mL of organic solvent to obtain a sulfur-containing compound solution;

[0086] The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, and the mixture was stirred for 30 minutes until the solution was completely mixed. The pH was adjusted to 8.5 by adding an acid-base adjuster, and the reaction was carried out at room temperature for 24 hours.

[0087] After the reaction was completed, the supernatant was discarded by centrifugation at 8000 rpm for 5 min, and the lower layer was obtained. The lower layer was washed three times and then freeze-dried under vacuum to obtain the melanin nanoparticles P(TA1-DA). 400 ).

[0088] Example 1.3

[0089] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as in Example 1.1, except that the weight ratio of the polyhydroxy compound and the sulfur-containing compound is 1:1.

[0090] A method for preparing sulfur-containing polydopamine melanin nanoparticles includes the following steps:

[0091] Dissolve 3g of the polyhydroxy compound in 540mL of water and stir at room temperature for 5min to obtain an aqueous solution of the polyhydroxy compound;

[0092] Dissolve 3g of the sulfur-containing compound in 240mL of organic solvent to obtain a sulfur-containing compound solution;

[0093] The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, and the mixture was stirred for 30 minutes until the solution was completely mixed. The pH was adjusted to 8.5 by adding an acid-base adjuster, and the reaction was carried out at room temperature for 24 hours.

[0094] After the reaction was completed, the supernatant was discarded by centrifugation at 8000 rpm for 5 min, and the lower layer was obtained. The lower layer was washed three times and then freeze-dried under vacuum to obtain the melanin nanoparticles P(TA1-DA). 65 ).

[0095] Example 1.4

[0096] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as in Example 1.1, except that the weight ratio of the polyhydroxy compound and the sulfur-containing compound is 1:2.

[0097] A method for preparing sulfur-containing polydopamine melanin nanoparticles includes the following steps:

[0098] Dissolve 3g of the polyhydroxy compound in 540mL of water and stir at room temperature for 5min to obtain an aqueous solution of the polyhydroxy compound;

[0099] Dissolve 6g of a sulfur-containing compound in 240mL of organic solvent to obtain a sulfur-containing compound solution;

[0100] The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, and the mixture was stirred for 30 minutes until the solution was completely mixed. The pH was adjusted to 8.5 by adding an acid-base adjuster, and the reaction was carried out at room temperature for 24 hours.

[0101] After the reaction was completed, the supernatant was discarded by centrifugation at 8000 rpm for 5 min, and the lower layer was obtained. The lower layer was washed three times and then freeze-dried under vacuum to obtain the melanin nanoparticles P(TA1-DA). 55 ).

[0102] Example 2-15

[0103] A sulfur-containing polydopamine melanin nanoparticle and its preparation method are described. The specific implementation method is the same as in Example 1.1, except that the sulfur-containing compound is a disulfide five-membered ring derivative, as shown in Table 1.

[0104] Table 1

[0105]

[0106] Examples 16-28

[0107] A sulfur-containing polydopamine melanin nanoparticle and its preparation method are disclosed. The specific implementation method is the same as in Example 1.1, except that the sulfur-containing compound has the following structural formula, as shown in Table 2.

[0108] Table 2

[0109]

[0110] Examples 29-40

[0111] A sulfur-containing polydopamine melanin nanoparticle and its preparation method are described. The specific implementation method is the same as in Example 1.1, except that the sulfur-containing compound is a thiol compound, as shown in Table 3.

[0112] Table 3

[0113]

[0114] Examples 41-48

[0115] A sulfur-containing polydopamine melanin nanoparticle and its preparation method are described. The specific implementation method is the same as in Example 1.1, except that the sulfur-containing compound is a polysulfide compound, as shown in Table 4.

[0116] Table 4

[0117]

[0118] Application Example 1

[0119] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0120] 25 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were mixed with 500 mg of thioctic acid, heated to 140 °C until melted, stirred for 15 min, transferred to a mold while hot and pressed into a film, and then irradiated with a 365 nm light source on both sides for 2 h to obtain a polymer film doped with sulfur-containing polydopamine melanin nanoparticles.

[0121] Application Example 2

[0122] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0123] 5 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were dissolved in 2 mL of water and sonicated for 5 min until uniformly dispersed. 0.5 g of acrylamide (AM) was added and stirred for 30 min. Then, 25 mg of ammonium persulfate, 5 mg of N,N-methylenebisacrylamide, and 10 μL of tetramethylethylenediamine were added and stirred for 5 min to form a pregel. The hydrogel was aged for 6 h.

[0124] Application Example 3

[0125] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0126] 5 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were dissolved in 5 mL of tetrahydrofuran and sonicated for 5 min until uniformly dispersed. 0.5 g of polymethyl methacrylate (PMMA) was added and stirred until completely dissolved. The mixture was then transferred to a mold and allowed to stand for 24 h to evaporate the solvent, resulting in a polymethyl methacrylate film doped with sulfur-containing polydopamine melanin nanoparticles.

[0127] The polymethyl methacrylate was purchased from Adamas. (beta), CAS number 9011-14-7, MDL number MFCD00134349.

[0128] Application Example 4

[0129] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0130] 5 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were dissolved in 5 mL of tetrahydrofuran and sonicated for 5 min until uniformly dispersed. 0.5 g of polycarbonate (PC) was added and stirred until completely dissolved. The mixture was then transferred to a mold and allowed to stand for 24 h to evaporate the solvent, resulting in a polycarbonate film doped with sulfur-containing polydopamine melanin nanoparticles.

[0131] The polycarbonate was purchased from Aladdin, CAS number 25037-45-0, MDL number MFCD00084476.

[0132] Application Example 5

[0133] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0134] 5 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were dissolved in 5 mL of tetrahydrofuran and sonicated for 5 min until uniformly dispersed. 0.5 g of polyurethane (PU) was added and stirred until completely dissolved. The mixture was then transferred to a mold and allowed to stand for 24 h to evaporate the solvent, resulting in a polyurethane film doped with sulfur-containing polydopamine melanin nanoparticles.

[0135] The polyurethane was purchased from Aladdin, CAS number 68084-39-9.

[0136] Application Example 6

[0137] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0138] 5 mg of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 were dissolved in 5 mL of water and sonicated for 5 min until uniformly dispersed. 0.5 g of polyvinyl alcohol (PVA) was added, and the mixture was heated to 90 °C and stirred under reflux until completely dissolved. The mixture was then transferred to a mold and allowed to stand for 24 h to evaporate the solvent, resulting in a polyvinyl alcohol film doped with sulfur-containing polydopamine melanin nanoparticles.

[0139] The polyvinyl alcohol was purchased from Macklin, and its full name is polyvinyl alcohol 1799, with CAS number 9002-89-5 and MDL number MFCD00081922.

[0140] Application Example 7

[0141] An application of the sulfur-containing polydopamine melanin nanoparticles is used in the preparation of polymer films with photothermal properties. The preparation method includes the following steps: 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is dissolved in 5 g of bisphenol A diglycidyl ether, 10 wt% of the total mass of the epoxy resin film diluent (n-butyl glycidyl ether) is added and stirred until uniformly mixed, 10 wt% of the total mass of the epoxy resin film amine curing agent (diethylenetriamine) is added, stirred for 5 min, transferred to a mold, allowed to stand for 24 h, and cured at 60 °C for 2 h to obtain an epoxy resin film doped with sulfur-containing polydopamine melanin nanoparticles.

[0142] Application Example 8

[0143] An application of the sulfur-containing polydopamine melanin nanoparticles is in the preparation of polymer films with photothermal properties. The preparation method includes the following steps:

[0144] 5 mg of sulfur-containing polydopamine melanin nanoparticles and 0.5 g of linear low-density polyethylene particles prepared in Example 1.1 were mechanically mixed evenly and pressed into a film at 120°C using a hot press to obtain a polyethylene film doped with sulfur-containing polydopamine melanin nanoparticles.

[0145] The linear low-density polyethylene was purchased from MERYER, CAS number 9002-88-4.

[0146] Performance testing

[0147] The appearance of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown in the figure below. Figure 1 The top left image shows its scanning electron microscope image. Figure 1 The lower left image shows the appearance of polydopamine nanoparticles. Figure 1 The upper right corner shows its scanning electron microscope image. Figure 1 Bottom right. Scanning electron microscopy images show that, compared to polydopamine nanoparticles, sulfur-containing polydopamine melanin nanoparticles have a rougher surface and a more pronounced granular texture. This indicates that lipoic acid did indeed interact with dopamine, leading to the change in macroscopic appearance. The presence of the lipoic acid carboxyl groups provides more molecular binding sites on the rough surface of the nanoparticles, giving them better compatibility with a wider range of matrices. Compared to polydopamine particles, the sulfur-containing polydopamine melanin nanoparticles are significantly darker in color, corresponding to enhanced light absorption. The sulfur-containing polydopamine melanin nanoparticles prepared in this invention exhibit good stability, are not easily soluble in water or common organic solvents, are not easily melted, and maintain their properties even after prolonged storage.

[0148] The X-ray diffraction (XRD) pattern of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown below. Figure 2 .from Figure 2 The absence of sharp diffraction peaks indicates that the sulfur-containing polydopamine melanin nanoparticles are amorphous and do not exhibit microphase separation.

[0149] X-ray photoelectron spectroscopy (XPS) of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown below. Figure 3 .from Figure 3 As can be seen, there are nitrogen atom peaks near 400 eV and sulfur atom peaks near 160 eV and 230 eV, indicating that the sulfur-containing polydopamine melanin nanoparticles contain sulfur.

[0150] X-ray photoelectron spectroscopy of sulfur in sulfur-containing polydopamine melanin nanoparticles is shown in [reference needed]. Figure 4 The X-ray photoelectron spectrum of sulfur in lipoic acid is shown in [reference needed]. Figure 5 ,Depend on Figure 4 and Figure 5The comparison shows that the chemical state of sulfur in sulfur-containing polydopamine melanin nanoparticles has changed, and the two newly added carbon-sulfur bonds prove that the sulfur atoms in lipoic acid are covalently linked to polydopamine.

[0151] The UV-Vis-NIR absorption and transmission spectra of the sulfur-containing polydopamine melanin nanoparticles and polydopamine prepared in Example 1.1 are shown in [Figure 1]. Figure 6 .Depend on Figure 6 It can be seen that, under the same concentration (100 μg / mL) conditions, the absorption value of sulfur-containing polydopamine melanin nanoparticles at a wavelength of 808 nm is much higher than that of polydopamine nanoparticles, while the corresponding transmission spectrum is smaller than that of polydopamine nanoparticles. This indicates that sulfur-containing polydopamine melanin nanoparticles improve the light absorption of polydopamine nanoparticles in the near-infrared region, theoretically proving that sulfur-containing melanin nanoparticles have the potential to enhance the photothermal efficiency of polydopamine.

[0152] Example 1.1 The sulfur-containing polydopamine melanin nanoparticles and polydopamine nanoparticles prepared at 808 nm wavelength, 1 W / cm 2 The power and aqueous phase photothermal conversion data under the condition of 100 μg / mL concentration are shown in the figure. Figure 7 ,Depend on Figure 7 It can be seen that under the same experimental conditions, the temperature of sulfur-containing polydopamine melanin nanoparticles is much higher than that of polydopamine nanoparticles, proving that sulfur-containing polydopamine melanin nanoparticles have a stronger photothermal conversion effect.

[0153] Example 1.1 The sulfur-containing polydopamine melanin nanoparticles and polydopamine nanoparticles prepared at 808 nm wavelength, 1 W / cm 2 The photothermal cycling data at power and a concentration of 100 μg / mL are shown in the figure. Figure 8 ,Depend on Figure 8 It can be seen that the solution temperature remains stable under multiple cycles, proving that the sulfur-containing melanin nanoparticles have good stability.

[0154] A schematic diagram of the time-temperature superimposed rheological curve of the polythiooctanoic acid film is shown below. Figure 9 A schematic diagram of the time-temperature superimposed rheological curve of the thin film prepared by photopolymerization of polydopamine nanoparticles and lipoic acid is shown below. Figure 10 The time-temperature superimposed rheological curve of the thin film prepared by photopolymerization of sulfur-containing polydopamine melanin nanoparticles and lipoic acid (Application Example 1) is shown in the figure. Figure 11 .Depend on Figure 9-11The master curve of polythioctic acid shows a direct transition from the glassy state to a viscous flow dynamic, indicating active linear chain segment movement and dissociation tendency due to discrete carboxyl hydrogen bonds. The master curve of the sulfur-containing polydopamine melanin nanoparticle-doped film includes additional dissipation and rubber regions between the glass transition frequency and structural relaxation frequency, indicating that a highly cross-linked network structure is generated by synergistic interfacial assembly mediated by dynamic covalent disulfide bonds and hydrogen bonds. Its highly dynamic characteristics are also demonstrated by the almost overlapping storage modulus and loss modulus curves. For the polydopamine nanoparticle-doped film, although the introduction of more rigid polydopamine nanoparticles results in a higher modulus of the composite network, the weaker interfacial interaction between the nanoparticles and the polymer leads to faster network relaxation, with a shorter terminal relaxation time (approximately 250 seconds) compared to the sulfur-containing polydopamine melanin nanoparticle-doped film (approximately 1250 seconds). This demonstrates better compatibility between the sulfur-containing polydopamine melanin nanoparticles and the polymer.

[0155] Absorbance at 808 nm, total photothermal efficiency, molar absorptivity, system time constant, wavelength at 808 nm, and W / cm² of polydopamine nanoparticles (PDA) and sulfur-containing polydopamine melanin nanoparticles. 2 Power, temperature difference under a concentration of 100 μg / mL, and test results are shown in Table 5.

[0156] Table 5

[0157]

Claims

1. A sulfur-containing polydopamine melanin nanoparticle, characterized in that, The raw materials for preparation include a polyhydroxy compound and a sulfur-containing compound, wherein the polyhydroxy compound is dopamine and the sulfur-containing compound is lipoic acid, and the weight ratio of the polyhydroxy compound to the sulfur-containing compound is 2:

1. The raw materials for preparation also include water, organic solvents and acid-base regulators.

2. The sulfur-containing polydopamine melanin nanoparticles according to claim 1, characterized in that, The acid-base regulator is at least one of organic alkaline substances and inorganic alkaline substances.

3. A method for preparing sulfur-containing polydopamine melanin nanoparticles according to claim 1 or 2, characterized in that, Includes the following steps: Dissolve the polyhydroxy compound in water and stir at room temperature for 1-10 minutes to obtain an aqueous solution of the polyhydroxy compound; A sulfur-containing compound is dissolved in an organic solvent to obtain a sulfur-containing compound solution; The sulfur-containing compound solution was added dropwise to the aqueous solution of the polyhydroxy compound, stirred until homogeneous, and the pH was adjusted to 8-9 with an acid-base adjuster. The reaction was carried out at room temperature. After the reaction was completed, the supernatant was discarded by centrifugation to obtain the lower layer. The lower layer was washed and then freeze-dried to obtain the melanin nanoparticles.

4. The method for preparing sulfur-containing polydopamine melanin nanoparticles according to claim 3, characterized in that, The reaction time at room temperature is 16-24 hours.

5. The method for preparing sulfur-containing polydopamine melanin nanoparticles according to claim 3, characterized in that, The concentration of the aqueous solution of the polyhydroxy compound is 0.001-0.01 g / mL; the concentration of the sulfur-containing compound solution is 0.005-0.01 g / mL.

6. An application of sulfur-containing polydopamine melanin nanoparticles according to claim 1 or 2, characterized in that, The sulfur-containing polydopamine melanin nanoparticles are used in the preparation of polymer films with photothermal properties.

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