Sulfur-containing polydopamine melanin nano particle as well as preparation method and application thereof

Abstract

The invention discloses sulfur-containing polydopamine melanin nanoparticles and a preparation method and application thereof, preparation raw materials comprise a polyhydroxy compound and a sulfur-containing compound, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-100): (1-100), and the preparation raw materials further comprise water, an organic solvent and an acid-base regulator. According to the preparation method, the dopamine and the sulfur-containing compound are subjected to self-polymerization reaction under the alkaline condition, additional cross-linking agents and oxidizing agents are not needed, and the obtained nanoparticles have excellent photo-thermal performance. The method shows huge application potential in the aspects of photo-thermal therapy, biomedical imaging, water purification, functional coatings and the like. The preparation method has the advantages of mild reaction conditions, no need of additional addition of a catalyst and an oxidizing agent, safe process, simple post-treatment, no generation of wastewater and waste residues harmful to the environment, and meeting of green chemical requirements.

Description

Technical Field

[0001] The present invention relates to the field of compositions for polymers, and particularly to a sulfur-containing polydopamine melanin nanoparticle, a preparation method thereof, and an application thereof. Background Art

[0002] Melanin plays important roles in nature and organisms, such as pigment, structural color, light protection, radiation absorption, and body temperature regulation. Applying polydopamine to the preparation of melanin shows great application potential in aspects such as photothermal therapy, biomedical imaging, water purification, and functional coatings. However, introducing a heterostructure into polydopamine will destroy the internal macromolecular structure of polydopamine. Therefore, it is crucial to develop a polydopamine melanin composite material with excellent photothermal performance and without affecting the compatibility of melanin in polymers.

[0003] Chinese Patent CN108383765B discloses the synthesis of a chlorambucil-dopamine conjugate and the preparation of prodrug nanoparticles. First, ethyl 2-((2-hydroxyethyl)disulfanyl)ethyl-2,2-dimethyl-1,3-benzodioxole-5-carboxylate is synthesized, then the chlorambucil-dopamine conjugate is synthesized, and finally the chlorambucil-polydopamine prodrug nanoparticles are synthesized to obtain a polymer drug carrier with near-infrared light absorption, reduction responsiveness, and integration of photothermal therapy and chemotherapy. However, the process steps are complex. Chinese Patent CN107510842B discloses a preparation method of a clean composite photothermal agent with excellent photothermal effects. Uniformly sized polydopamine nanoparticles are prepared by sufficient oxidative self-polymerization reaction, and sulfide is added as a sulfur source. After sufficient reaction, a composite microsphere with CuS loaded on PDA is prepared. The photothermal effect is good, the synthesis method is green, and the product is clean. However, the compatibility with polymers is poor and it is not suitable for application in polymer films. Summary of the Invention

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

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

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

[0007] As an implementation manner, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1 - 10):(1 - 10).

[0008] As an implementation manner, the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1 - 5):(1 - 5).

[0009] As an implementation manner, 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] As an implementation manner, the sulfur-containing compound includes at least one of sulfur ring compounds, mercapto compounds, and polysulfur compounds.

[0011] As an implementation manner, the sulfur ring compound at least includes a dithiolane compound.

[0012] As an implementation manner, the dithiolane compound includes at least one of dithiolane carboxylic acid and its derivatives, and dithiolane amide and its derivatives.

[0013] As an implementation manner, the structural formula of the dithiolane carboxylic acid and its derivatives is shown as Formula 1 or Formula 2:

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

[0015] As an implementation manner, the structural formula of the dithiolane carboxylic acid and its derivatives includes but is not limited to the following structural formulas:

[0016]

[0017] As an implementation manner, the structural formula of the dithiolane amide and its derivatives is shown as Formula 3 or Formula 4:

[0018]

[0019] 4; in Formula 3 or Formula 4, R5 - R9 and R 15 -R 19 both include one of hydrogen, C1 - C4 straight-chain alkyl, or C1 - C4 branched-chain alkyl; R 10 -R 14 and R 20 -R 24Each includes one of hydrogen, hydroxyl or methyl; c and d are both integers from 1 to 6, and e and f are both integers from 1 to 3.

[0020] As an embodiment, the structural formula of the dithiol five-membered ring amide and its derivatives includes but is not limited to the following structural formulas:

[0021]

[0022]

[0023] As an embodiment, the sulfur ring compound further includes the following structural formulas, such as those shown in Formula 5 or Formula 10:

[0024]

[0025] In Formula 5 or Formula 10, R 25 -R 30 includes but is not limited to one of hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched-chain alkyl, hydroxyl, carboxyl, mercapto, phenyl or amino.

[0026] As an embodiment, the sulfur ring compound further includes but is not limited to the following structural formulas:

[0027]

[0028] As an embodiment, the structural formula of the mercapto compound is as shown in Formula 11: In Formula 11, R 31 and R 32 both include but are not limited to one of hydrogen, C1-C4 straight-chain alkyl, C1-C4 branched-chain alkyl, hydroxyl, carboxyl, mercapto, phenyl or amino, and n is an integer from 1 to 10.

[0029] As an embodiment, the structural formula of the mercapto compound includes but is not limited to the following structural formulas:

[0030]

[0031] As an embodiment, the structural formula of the polysulfide compound is S g , and g is an integer from 2 to 20.

[0032] As an embodiment, the structural formula of the polysulfide compound includes but is not limited to the following structural formulas:

[0033]

[0034] As an embodiment, the polyhydroxy compound includes at least one of dopamine, catechol or catechol derivatives.

[0035] As an embodiment, the structural formula of the catechol derivative is shown in Formula 12: In Formula 12, R 33 includes one of hydrogen, a C1-C4 straight-chain alkyl group, or a C1-C4 branched-chain alkyl group; R 34 -R 35 includes one of hydrogen, an amino group, a carboxyl group, or an amide, and m is an integer from 1 to 3.

[0036] As an embodiment, the acid-base regulator is at least one of an organic base and an inorganic base.

[0037] As an embodiment, the organic base includes, but is not limited to, at least one of methylamine, ethylamine, triethylamine, aniline, pyridine, imidazole, or tetramethylammonium hydroxide; the inorganic base includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide, ammonia water, sodium carbonate, or sodium bicarbonate.

[0038] As an embodiment, the organic solvent includes, but is not limited to, at least one of ethanol, acetonitrile, acetone, tetrahydrofuran, dimethylformamide, or dimethyl sulfoxide.

[0039] The second aspect of the present invention provides a method for preparing sulfur-containing polydopamine melanin nanoparticles, comprising the following steps:

[0040] Dissolve the polyhydroxy compound in water and stir at room temperature for 1-10 min to obtain an aqueous solution of the polyhydroxy compound;

[0041] Dissolve the sulfur-containing compound in an organic solvent to obtain a sulfur-containing compound solution;

[0042] Drop the sulfur-containing compound solution into the aqueous solution of the polyhydroxy compound, stir evenly, add an acid-base regulator to adjust the pH to 8-9, and react at room temperature;

[0043] After the reaction is completed, centrifuge to discard the supernatant to obtain the lower layer, and wash and freeze-dry the lower layer to obtain the melanin nanoparticles.

[0044] As an embodiment, the reaction time at room temperature is 16-24 h.

[0045] As an 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.

[0046] As an embodiment, the concentration of the aqueous solution of the polyhydroxy compound is 0.003 - 0.008 g / mL; the concentration of the sulfur-containing compound solution is 0.005 - 0.008 g / mL.

[0047] As an embodiment, the concentration of the aqueous solution of the polyhydroxy compound is 0.0055 g / mL; the concentration of the sulfur-containing compound solution is 0.00625 g / mL.

[0048] During the experiment, the inventors found that the melanin nanoparticles formed by the reaction of the sulfur-containing compound and dopamine have excellent photothermal conversion performance, far higher than the total photothermal efficiency of traditional polydopamine nanoparticles. The reason is that sulfur atoms are grafted onto polydopamine through Michael addition reaction, and the introduction of electron donor sulfur atoms and electron acceptor carboxyl groups constructs a donor-acceptor microstructure in the melanin nanoparticles, effectively reducing the molecular energy level gap and promoting electron transfer. At the same time, the intermolecular conjugation is disrupted, and large aggregates cannot be formed, resulting in an increase in the radical concentration and limiting non-thermal radiation conversion. The combined effect of the two enhances the light absorption and photothermal conversion efficiency of the sulfur-containing nanoparticles.

[0049] The third aspect of the present invention provides an application of sulfur-containing polydopamine melanin nanoparticles, and the sulfur-containing polydopamine melanin nanoparticles are applied to the preparation of a polymer film with photothermal properties.

[0050] As an embodiment, the preparation method of the polymer film with photothermal properties includes the following steps:

[0051] Mix the sulfur-containing polydopamine melanin nanoparticles with a solvent, add a polymer, stir and disperse evenly, form a film, transfer it into a mold, let it stand, and volatilize the solvent to obtain a polymer film with photothermal properties.

[0052] As an embodiment, the weight ratio of the sulfur-containing polydopamine melanin nanoparticles to the polymer is (0.1 - 0.5):1.

[0053] As an embodiment, the film-forming method includes, but is not limited to, standing film formation, room temperature pressing film formation, hot pressing film formation, or aging film formation.

[0054] As an embodiment, the polymer includes, but is not limited to, at least one of polymethyl methacrylate, polyurethane, polyethylene, polystyrene, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyimide, polyformaldehyde, 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.

[0055] During the experiment, the inventors found that after the prepared sulfur-containing polydopamine melanin nanoparticles were combined with the polymer, the compatibility effect was better, and excellent photothermal performance could still be maintained. The reason is that 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, constructing a high-performance dynamic cross-linked polymer network as a nano-crosslinking agent, so that the sulfur-containing polydopamine melanin nanoparticles have excellent compatibility in different polymer matrices, effectively enhancing the interfacial photothermal conversion and heat transfer, thus realizing efficient light-controlled real-time self-healing.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) For the sulfur-containing polydopamine melanin nanoparticles of the present invention, dopamine and a sulfur-containing compound undergo a self-polymerization reaction under alkaline conditions without the need for additional cross-linking agents and oxidants, and the obtained nanoparticles have excellent photothermal performance.

[0058] (2) The sulfur-containing polydopamine melanin nanoparticles of the present invention and the polymer are in a weight ratio of (0.01 - 0.05):1. The addition amount of the melanin nanoparticles is low, the cost is reduced, and the compatibility in the polymer is excellent.

[0059] (3) For the sulfur-containing polydopamine melanin nanoparticles of the present invention, a high-performance dynamic cross-linked polymer network can be constructed in the polymer, effectively enhancing the interfacial photothermal conversion and heat transfer, thus realizing efficient light-controlled real-time self-healing.

[0060] (4) For the preparation method of the sulfur-containing polydopamine melanin nanoparticles of the present invention, the reaction conditions are mild, no additional catalysts and oxidants are required, the process is safe, the post-treatment is simple, and no waste water and waste residues harmful to the environment are generated, meeting the requirements of green chemistry.

[0061] (5) For the sulfur-containing polydopamine melanin nanoparticles of the present invention, the raw materials for preparation are beneficial to the human body, have good biocompatibility, wide sources, are cheap and easy to obtain, have industrial feasibility, and show great application potential in photothermal therapy, biomedical imaging, water purification, functional coatings, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 The appearance (upper left) of the sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) prepared in Example 1.1 of the present invention, and its scanning electron microscope image (lower left), the appearance (upper right) of polydopamine (PDA) nanoparticles, and its scanning electron microscope image (lower right).

[0063] Figure 2X-ray diffraction (XRD) pattern of sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) prepared in Example 1.1 of the present invention.

[0064] Figure 3 X-ray photoelectron spectroscopy (XPS) of sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 of the present invention; from top to bottom in the figure are polydopamine (PDA) nanoparticles, sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )), and thioctic acid (TA).

[0065] Figure 4 X-ray photoelectron spectroscopy of sulfur element in sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) prepared in Example 1.1 of the present invention.

[0066] Figure 5 X-ray photoelectron spectroscopy of sulfur element in thioctic acid (TA).

[0067] Figure 6 Ultraviolet-visible-near-infrared absorption spectra and transmission spectra of sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) and polydopamine (PDA) prepared in Example 1.1 of the present invention.

[0068] Figure 7 Photothermal conversion data graph of sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) and polydopamine nanoparticles (PDA) under the conditions of 808 nm wavelength, 1 W / cm 2 power, and 100 μg / mL concentration.

[0069] Figure 8 Photothermal cycling data graph of sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA 125 )) and polydopamine (PDA) nanoparticles under the conditions of 808 nm wavelength, 1 W / cm 2 power, and 100 μg / mL concentration.

[0070] Figure 9 Schematic diagram of time-temperature superposition rheological curve of polythioctic acid (PTA) film.

[0071] Figure 10 Schematic diagram of time-temperature superposition rheological curve of the film prepared by photopolymerization after melting of polydopamine nanoparticles (PDA) and thioctic acid.

[0072] Figure 11Sulfur-containing polydopamine melanin nanoparticles (P(TA1-DA) prepared in Example 1.1 of the present invention 125 ) and the schematic diagram of the time-temperature superposition rheological curve of the film prepared by photopolymerization after melting with lipoic acid.

[0073] Figure 12 In the upper row, from left to right in sequence, are the schematic diagrams of polymer films prepared by doping polydopamine (PDA) into polyacrylamide (PAM), polymethyl methacrylate (PMMA), polyurethane (PU), polyvinyl alcohol (PVA), polyethylene (PE), polycarbonate (PC), and bisphenol A epoxy resin (DGEBA). In the lower row, from left to right in sequence, are the schematic diagrams of polymer films prepared by doping the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 of the present invention 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 epoxy resin (Application Example 7). Detailed implementation manners

[0074] Example 1.1

[0075] A kind of sulfur-containing polydopamine melanin nanoparticles, the preparation raw materials include polyhydroxy compounds and sulfur-containing compounds, the weight ratio of the polyhydroxy compounds and the sulfur-containing compounds is 2:1, and the preparation raw materials also include water, organic solvents and acid-base regulators.

[0076] The polyhydroxy compound is dopamine hydrochloride, the sulfur-containing compound is lipoic acid, the organic solvent is absolute ethanol, and the acid-base regulator is ammonia water.

[0077] A preparation method of sulfur-containing polydopamine melanin nanoparticles, comprising the following steps:

[0078] Dissolve 3 g of polyhydroxy compounds in 540 mL of water, stir at room temperature for 5 min to obtain an aqueous solution of polyhydroxy compounds;

[0079] Dissolve 1.5 g of sulfur-containing compounds in 240 mL of organic solvents to obtain a solution of sulfur-containing compounds;

[0080] Drop the solution of sulfur-containing compounds into the aqueous solution of polyhydroxy compounds, stir for 30 min until the solution is completely mixed evenly, add an acid-base regulator to adjust the pH to 8.5, and react at room temperature for 24 h;

[0081] After the reaction is completed, centrifuge at 8000 rpm for 5 min to discard the supernatant to obtain the lower layer, wash the lower layer 3 times and then vacuum freeze-dry to obtain the melanin nanoparticles P(TA1-DA 125 ).

[0082] Example 1.2

[0083] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as that of Example 1.1, the difference is that the weight ratio of the polyhydroxy compound to the sulfur-containing compound is 10:1.

[0084] A preparation method of sulfur-containing polydopamine melanin nanoparticles, comprising the following steps:

[0085] Dissolve 3 g of the polyhydroxy compound in 540 mL of water, stir at room temperature for 5 min to obtain an aqueous solution of the polyhydroxy compound;

[0086] Dissolve 0.3 g of the sulfur-containing compound in 240 mL of an organic solvent to obtain a sulfur-containing compound solution;

[0087] Drop the sulfur-containing compound solution into the aqueous solution of the polyhydroxy compound, stir for 30 min until the solution is completely mixed evenly, add an acid-base regulator to adjust the pH to 8.5, and react at room temperature for 24 h;

[0088] After the reaction, centrifuge at 8000 rpm for 5 min to discard the supernatant to obtain the lower layer, wash the lower layer 3 times and then vacuum freeze-dry to obtain the melanin nanoparticles P(TA1-DA 400 )

[0089] Example 1.3

[0090] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as that of Example 1.1, the difference is that the weight ratio of the polyhydroxy compound to the sulfur-containing compound is 1:1.

[0091] A preparation method of sulfur-containing polydopamine melanin nanoparticles, comprising the following steps:

[0092] Dissolve 3 g of the polyhydroxy compound in 540 mL of water, stir at room temperature for 5 min to obtain an aqueous solution of the polyhydroxy compound;

[0093] Dissolve 3 g of the sulfur-containing compound in 240 mL of an organic solvent to obtain a sulfur-containing compound solution;

[0094] Drop the sulfur-containing compound solution into the aqueous solution of the polyhydroxy compound, stir for 30 min until the solution is completely mixed evenly, add an acid-base regulator to adjust the pH to 8.5, and react at room temperature for 24 h;

[0095] After the reaction, centrifuge at 8000 rpm for 5 min to discard the supernatant to obtain the lower layer, wash the lower layer 3 times and then vacuum freeze-dry to obtain the melanin nanoparticles P(TA1-DA 65 )

[0096] Example 1.4

[0097] A sulfur-containing polydopamine melanin nanoparticle, the specific implementation method is the same as that of Example 1.1, the difference is that the weight ratio of the polyhydroxy compound to the sulfur-containing compound is 1:2.

[0098] A preparation method of a sulfur-containing polydopamine melanin nanoparticle, comprising the following steps:

[0099] Dissolve 3 g of the polyhydroxy compound in 540 mL of water, stir at room temperature for 5 min to obtain an aqueous solution of the polyhydroxy compound;

[0100] Dissolve 6 g of the sulfur-containing compound in 240 mL of an organic solvent to obtain a sulfur-containing compound solution;

[0101] Drop the sulfur-containing compound solution into the aqueous solution of the polyhydroxy compound, stir for 30 min until the solution is completely mixed evenly, add an acid-base regulator to adjust the pH to 8.5, and react at room temperature for 24 h;

[0102] After the reaction, centrifuge at 8000 rpm for 5 min to discard the supernatant to obtain the lower layer, wash the lower layer 3 times and then vacuum freeze-dry to obtain the melanin nanoparticle P(TA1-DA 55 ).

[0103] Examples 2-15

[0104] A sulfur-containing polydopamine melanin nanoparticle and its preparation method, the specific implementation method is the same as that of Example 1.1, the difference is that the sulfur-containing compound is a dithiol five-membered ring derivative, as shown in Table 1 for details.

[0105] Table 1

[0106]

[0107]

[0108] Examples 16-28

[0109] A sulfur-containing polydopamine melanin nanoparticle and its preparation method, the specific implementation method is the same as that of Example 1.1, the difference is that the sulfur-containing compound has the following structural formula, as shown in Table 2 for details.

[0110] Table 2

[0111]

[0112]

[0113] Examples 29-40

[0114] A sulfur-containing polydopamine melanin nanoparticle and its preparation method. The specific implementation method is the same as that of Example 1.1, except that the sulfur-containing compound is a mercapto compound, as shown in Table 3 specifically.

[0115] Table 3

[0116]

[0117]

[0118] Examples 41 - 48

[0119] A sulfur-containing polydopamine melanin nanoparticle and its preparation method. The specific implementation method is the same as that of Example 1.1, except that the sulfur-containing compound is a polysulfide compound, as shown in Table 4 specifically.

[0120] Table 4

[0121]

[0122]

[0123] Application Example 1

[0124] An application of the sulfur-containing polydopamine melanin nanoparticle in the preparation of a polymer film with photothermal properties. The preparation method includes the following steps:

[0125] Mix 25 mg of the sulfur-containing polydopamine melanin nanoparticle prepared in Example 1.1 and 500 mg of lipoic acid, heat to melting at 140 °C, stir for 15 min, transfer to a mold while it is hot and press into a film, and then irradiate both sides with a 365 nm light source for 2 h to obtain a polymer film doped with the sulfur-containing polydopamine melanin nanoparticle.

[0126] Application Example 2

[0127] An application of the sulfur-containing polydopamine melanin nanoparticle in the preparation of a polymer film with photothermal properties. The preparation method includes the following steps:

[0128] Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticle prepared in Example 1.1 in 2 mL of water, ultrasonicate for 5 min until evenly dispersed, add 0.5 g of acrylamide (AM) and stir for 30 min, then add 25 mg of ammonium persulfate, 5 mg of N,N'-methylenebisacrylamide, and 10 μL of tetramethylethylenediamine and stir for 5 min to form a pre-gel, and age for 6 h to obtain a hydrogel.

[0129] Application Example 3

[0130] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties. The preparation method includes the following steps:

[0131] Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 in 5 mL of tetrahydrofuran, ultrasonicate for 5 min until evenly dispersed, add 0.5 g of polymethyl methacrylate (PMMA), stir until completely dissolved, transfer to a mold, and let stand for 24 h to evaporate the solvent to obtain a polymethyl methacrylate film doped with sulfur-containing polydopamine melanin nanoparticles.

[0132] The polymethyl methacrylate is purchased from Adamas (adamas-beta), with a CAS number of 9011-14-7 and an MDL number of MFCD00134349.

[0133] Application Example 4

[0134] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties. The preparation method includes the following steps:

[0135] Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 in 5 mL of tetrahydrofuran, ultrasonicate for 5 min until evenly dispersed, add 0.5 g of polycarbonate (PC), stir until completely dissolved, transfer to a mold, and let stand for 24 h to evaporate the solvent to obtain a polycarbonate film doped with sulfur-containing polydopamine melanin nanoparticles.

[0136] The polycarbonate is purchased from Aladdin, with a CAS number of 25037-45-0 and an MDL number of MFCD00084476.

[0137] Application Example 5

[0138] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties. The preparation method includes the following steps:

[0139] Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 in 5 mL of tetrahydrofuran, ultrasonicate for 5 min until evenly dispersed, add 0.5 g of polyurethane (PU), stir until completely dissolved, transfer to a mold, and let stand for 24 h to evaporate the solvent to obtain a polyurethane film doped with sulfur-containing polydopamine melanin nanoparticles.

[0140] The polyurethane is purchased from Aladdin, with a CAS number of 68084-39-9.

[0141] Application Example 6

[0142] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties, and the preparation method includes the following steps:

[0143] Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 in 5 mL of water, ultrasonically treat for 5 min until evenly dispersed, add 0.5 g of polyvinyl alcohol (PVA), heat and reflux with stirring at 90 °C until completely dissolved, transfer to a mold, and let stand for 24 h to volatilize the solvent to obtain a polyvinyl alcohol film doped with sulfur-containing polydopamine melanin nanoparticles.

[0144] The polyvinyl alcohol is purchased from Macklin, with the full name of polyvinyl alcohol type 1799, CAS number 9002-89-5, and MDL number MFCD00081922.

[0145] Application Example 7

[0146] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties, and the preparation method includes the following steps: Dissolve 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 in 5 g of bisphenol A diglycidyl ether, add a diluent (n-butyl glycidyl ether) accounting for 10 wt% of the total mass of the epoxy resin film and stir until evenly mixed, add an amine curing agent (diethylenetriamine) accounting for 10 wt% of the total mass of the epoxy resin film, stir for 5 min and then transfer to a mold, let stand for 24 h, and cure at 60 °C for 2 h to obtain an epoxy resin film doped with sulfur-containing polydopamine melanin nanoparticles.

[0147] Application Example 8

[0148] An application of the sulfur-containing polydopamine melanin nanoparticles, which is applied to the preparation of a polymer film with photothermal properties, and the preparation method includes the following steps:

[0149] Mechanically mix 5 mg of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 and 0.5 g of linear low-density polyethylene particles evenly, and press into a film at 120 °C with a hot press to obtain a polyethylene film doped with sulfur-containing polydopamine melanin nanoparticles.

[0150] The linear low-density polyethylene is purchased from MERYER, and the CAS number is 9002-88-4.

[0151] Performance Test

[0152] The appearance diagram of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown in Figure 1 the upper left, and its scanning electron microscope picture is shown in Figure 1 the lower left, and the appearance diagram of the polydopamine nanoparticles is shown in Figure 1Upper right, and its scanning electron microscope image is shown in Figure 1 Lower right. It can be seen from the scanning electron microscope image that compared with polydopamine nanoparticles, the surface of sulfur-containing polydopamine melanin nanoparticles is rougher and has obvious granularity, indicating that lipoic acid does interact with dopamine, resulting in the change of the macroscopic appearance. The presence of the carboxyl group of lipoic acid provides more molecular binding sites on the rough surface of the nanoparticles, making the sulfur-containing nanoparticles have better compatibility with more substrates. Compared with polydopamine particles, the color of sulfur-containing polydopamine melanin nanoparticles becomes significantly darker, corresponding to the enhanced light absorption ability. The sulfur-containing polydopamine melanin nanoparticles prepared in the present invention have good stability, are not easily soluble in water or common organic solvents, are not easily melted, and can still maintain the stability of their properties after long-term storage.

[0153] The X-ray diffraction (XRD) pattern of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown in Figure 2 . It can be seen from Figure 2 that there are no sharp diffraction peaks, indicating that the sulfur-containing polydopamine melanin nanoparticles are amorphous and there is no microphase separation.

[0154] The X-ray photoelectron spectroscopy (XPS) of the sulfur-containing polydopamine melanin nanoparticles prepared in Example 1.1 is shown in Figure 3 . It can be seen from Figure 3 that there is a nitrogen atom peak near 400 eV and sulfur atom peaks near 160 eV and 230 eV, indicating that the sulfur-containing polydopamine melanin nanoparticles contain sulfur.

[0155] The X-ray photoelectron spectroscopy of sulfur in sulfur-containing polydopamine melanin nanoparticles is shown in Figure 4 , and the X-ray photoelectron spectroscopy of sulfur in lipoic acid is shown in Figure 5 . It can be known from the comparison of Figure 4 and Figure 5 that the chemical state of sulfur in sulfur-containing polydopamine melanin nanoparticles has changed, and the newly added two carbon-sulfur bonds prove that the sulfur atoms in lipoic acid are covalently linked to polydopamine.

[0156] The ultraviolet-visible-near-infrared absorption spectra and transmission spectra of the sulfur-containing polydopamine melanin nanoparticles and polydopamine prepared in Example 1.1 are shown in Figure 6 . It can be known from Figure 6 that under the condition of equal concentration (100 μg / mL), the absorption value of sulfur-containing polydopamine melanin nanoparticles at a wavelength of 808 nm is much higher than that of polydopamine nanoparticles, and the corresponding transmission spectrum is smaller than that of polydopamine nanoparticles, indicating that the sulfur-containing polydopamine melanin nanoparticles improve the light absorption of polydopamine nanoparticles in the near-infrared region, theoretically proving that the sulfur-containing melanin nanoparticles have the potential to enhance the photothermal efficiency of polydopamine.

[0157] The aqueous photothermal conversion data graphs of the sulfur-containing polydopamine melanin nanoparticles and polydopamine nanoparticles prepared in Example 1.1 at a wavelength of 808 nm, a power of 1 W / cm 2 , and a concentration of 100 μg / mL are shown in Figure 7 . It can be seen from Figure 7 that under the same experimental conditions, the temperature of the sulfur-containing polydopamine melanin nanoparticles is much higher than that of the polydopamine nanoparticles, which proves that the sulfur-containing polydopamine melanin nanoparticles have stronger photothermal conversion effects.

[0158] The photothermal cycling data graphs of the sulfur-containing polydopamine melanin nanoparticles and polydopamine nanoparticles prepared in Example 1.1 at a wavelength of 808 nm, a power of 1 W / cm 2 , and a concentration of 100 μg / mL are shown in Figure 8 . It can be seen from Figure 8 that the solution temperature can still remain stable under multiple cycles, which proves that the sulfur-containing melanin nanoparticles have good stability.

[0159] The schematic diagram of the time-temperature superposition rheological curve of the polythioctic acid film is shown in Figure 9 . The schematic diagram of the time-temperature superposition rheological curve of the film prepared by photopolymerization after melting polydopamine nanoparticles and thioctic acid is shown in Figure 10 . The schematic diagram of the time-temperature superposition rheological curve of the film prepared by photopolymerization after melting sulfur-containing polydopamine melanin nanoparticles and thioctic acid (Application Example 1) is shown in Figure 11 . It can be seen from Figures 9 - 11 that the master curve of polythioctic acid shows a direct transition from the glassy state to the viscous flow state, which indicates that due to discrete carboxyl hydrogen bonds, there are active linear chain segment movements and dissociation tendencies. The master curve of the sulfur-containing polydopamine melanin nanoparticle-doped film contains an additional dissipation zone and a rubber zone between the glass transition frequency and the structural relaxation frequency, indicating that a highly cross-linked network structure is generated by the synergistic interfacial assembly mediated by dynamic covalent disulfide bonds and hydrogen bonds. Its highly dynamic characteristics are also proved by the almost overlapping storage modulus and loss modulus curves. For the polydopamine nanoparticle-doped film, although the introduction of more rigid polydopamine nanoparticles makes the resulting composite network have a higher modulus, due to the weak interfacial interaction between the nanoparticles and the polymer, the network relaxation is faster, and its terminal relaxation time (about 250 seconds) is shorter than that of the sulfur-containing polydopamine melanin nanoparticle-doped film (about 1250 seconds). It proves that the sulfur-containing polydopamine melanin nanoparticles have better compatibility with the polymer.

[0160] The absorbance at 808 nm, the total photothermal efficiency, the molar extinction coefficient, the system time constant of the polydopamine nanoparticles (PDA) and the sulfur-containing polydopamine melanin nanoparticles, at a wavelength of 808 nm, a power of 1 W / cm 2Power, temperature difference under the condition of a concentration of 100 μg / mL, and the test results are shown in Table 5.

[0161] Table 5

[0162]

Claims

1. A sulfur-containing polydopamine melanin nanoparticle, characterized in that, The preparation raw materials include a polyhydroxy compound and a sulfur-containing compound, and the weight ratio of the polyhydroxy compound to the sulfur-containing compound is (1-100):(1-100). The preparation raw materials further include water, an organic solvent and an acid-base regulator.

2. The sulfur-containing polydopamine melanin nanoparticles according to claim 1, wherein The sulfur-containing compound includes at least one of a sulfur ring compound, a mercapto compound or a polysulfide compound; the structural formula of the mercapto compound is as shown in Formula 11: In Formula 11, R 31 , R 32 is one of hydrogen, a C1-C4 straight-chain alkyl group, a C1-C4 branched-chain alkyl group, a hydroxyl group, a carboxyl group, a mercapto group, a phenyl group or an amino group, and n is an integer from 1 to 10; the structural formula of the polysulfide compound is S g , and g is an integer from 2 to 20.

3. The sulfur-containing polydopamine melanin nanoparticles according to claim 2, wherein The sulfur ring compound at least includes a dithiolane compound.

4. The sulfur-containing polydopamine melanin nanoparticles according to claim 3, wherein The dithiolane compound includes at least one of dithiolane carboxylic acid and its derivatives, and dithiolane amide and its derivatives.

5. The sulfur-containing polydopamine melanin nanoparticles according to claim 1, characterized in that, The polyhydroxy compound includes at least one of dopamine, catechol or catechol derivatives.

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

7. A preparation method of the sulfur-containing polydopamine melanin nanoparticles according to any one of claims 1-6, characterized in that, It includes the following steps: Dissolve the polyhydroxy compound in water and stir at room temperature for 1-10 min to obtain an aqueous polyhydroxy compound solution; Dissolve the sulfur-containing compound in an organic solvent to obtain a sulfur-containing compound solution; Drop the sulfur-containing compound solution into the aqueous polyhydroxy compound solution, stir evenly, add an acid-base regulator to adjust the pH to 8-9, and react at room temperature; After the reaction is completed, centrifuge to discard the supernatant to obtain the lower layer. Wash the lower layer and freeze-dry to obtain the melanin nanoparticles.

8. The preparation method of the sulfur-containing polydopamine melanin nanoparticles according to claim 7, characterized in that, The reaction time at room temperature is 16-24 h.

9. The preparation method of the sulfur-containing polydopamine melanin nanoparticles according to claim 7, wherein, The concentration of the aqueous polyhydroxy compound solution is 0.001-0.01 g / mL; the concentration of the sulfur-containing compound solution is 0.005-0.01 g / mL.

10. Use of the sulfur-containing polydopamine melanin nanoparticles according to any one of claims 1-6, characterized in that, The sulfur-containing polydopamine melanin nanoparticles are applied to the preparation of a polymer film with photothermal properties.

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