An ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controllable particle size

Abstract

The invention discloses a kind of ultrasonic-assisted particle size accurate controllable polydopamine nanoparticle preparation method, comprise the following steps: (1) absolute ethanol EtOH is added to deionized water, obtain clear solution;(2) dopamine hydrochloride powder is added to above-mentioned clear solution, and by 0.1mol / L NaOH solution adjustment reaction solution pH, dopamine hydrochloride solution concentration is 1 4mg / mL in system, auxiliary ultrasonication, reacts after 3 6 hours, through high-speed centrifugation, washing, drying, obtain polydopamine nanoparticles. The present invention generates active oxygen by ultrasonication to accelerate dopamine polymerization speed, and reduces polydopamine nucleation activation energy, realizes effective regulation and control to polydopamine nanoparticle nucleation and growing process, obtains the polydopamine nanoparticles of uniform dispersion, high sphericity, wide size range, the method for the present invention is simple, time-saving and efficient, is convenient to promote and large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials and relates to an ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controllable particle size. Background Art

[0002] In recent years, polydopamine nanoparticles have been successfully used as drug carriers, free radical scavengers, medical imaging agents, structural dyes, and photothermal agents due to their good biocompatibility, rich functional groups (such as catechol and imine), and similarity to natural melanin. In addition to the above characteristics, the particle size of polydopamine nanoparticles plays an important role in the application process. For example, the specific surface area of ​​polydopamine nanoparticles significantly affects the photothermal effect, the binding of metal ions, and the drug loading efficiency. In addition, changes in the size of polydopamine nanoparticles will cause their dispersions to exhibit different colors. Therefore, various structural colors can be designed by adjusting the particle size of polydopamine nanoparticles.

[0003] The widespread application of polydopamine nanoparticles has put forward an urgent demand for their size-controllable synthesis methods. Polydopamine nanoparticles are usually prepared by the self-oxidative polymerization reaction of dopamine in an alkaline solution. At present, researchers at home and abroad have proposed many methods to control the size of polydopamine nanoparticles. For example, additives such as free radicals, microemulsions and Pluronic block polymers are used to mediate the nucleation and growth process of dopamine, thereby adjusting the particle size of the synthesized polydopamine nanoparticles (Polym.Chem.10(2019)4194-4200; J.Mater.Chem.B 3(2015)6731-6739; Chinese patent CN110498946A). However, the foreign substances introduced by this method will affect the composition and structure of PDA nanoparticles, thereby affecting their properties. In addition, the particle size range of PDA nanoparticles prepared by this method is narrow, and nanoparticles with a large size range cannot be obtained. Another commonly used strategy is to use external energy such as microplasma electrochemistry and UV irradiation. This method achieves the directional design of the size of polydopamine nanoparticles by regulating the self-assembly / polymerization reaction of dopamine (Chem.Eng.J.344(2018)480-486; ACS Appl.Bio Mater.2(2019)4667-4674.). However, microplasma electrochemistry and UV irradiation can easily have an adverse effect on the morphology of polydopamine nanoparticles, and the synthesized nanoparticles are unevenly dispersed and easy to agglomerate.

[0004] "A hollow mesoporous polydopamine nanocarrier, preparation method and application thereof" (CN 202110960482.5) discloses a hollow mesoporous polydopamine nanocarrier. This method uses mesoporous silica as a hard template, and then utilizes the surface modification properties of polydopamine to form an mSiO2@PDA nanocomposite. Finally, the hard template is removed to prepare a hollow mesoporous polydopamine nanocarrier. This method uses ultrasonic treatment in the process of preparing the silica hard template, specifically involving the dispersing effect of ultrasound to form a uniformly dispersed silica nanosystem, but cannot regulate the size of the silica particles.

[0005] “A preparation method and application of polydopamine-modified magnetic nanoparticles” (CN201910437453.3) discloses a method for preparing polydopamine-modified magnetic nanoparticles. In this method, ultrasonic treatment is used when preparing nano-Fe3O4 particles and dissolving dopamine hydrochloride powder. The ultrasonic treatment is also to make the particles in the solution system evenly dispersed and cannot control the particle size. In addition, the researchers found that ultrasonic action is conducive to the rapid formation of polydopamine coating on the surface of the substrate (Chem. Commun. 57 (2021) 13740-13743), but there is no report on whether ultrasonic action can regulate the size distribution of polydopamine nanoparticles.

[0006] Therefore, the controllable synthesis of polydopamine nanoparticles with uniform spherical shape and a wide range of sizes remains a huge challenge. Therefore, proposing a simple, precise, and controllable preparation strategy for highly dispersed polydopamine nanoparticles with a wide range of sizes has always been a technical challenge that has been urgently addressed by those skilled in the art. Summary of the Invention

[0007] Purpose of the Invention: To address the problems of existing technologies, such as the adverse effects of added substances on the composition and structure of polydopamine nanoparticles, the poor size controllability and narrow size range of the synthesized polydopamine nanoparticles, and the uneven morphology and low sphericity caused by applied energy, the present invention provides an ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controlled particle size. This method, for the first time, efficiently regulates the nucleation and growth of polydopamine through the action of an ultrasonic field, thereby achieving precise design of the polydopamine nanoparticle size and obtaining uniformly dispersed, highly spherical polydopamine nanoparticles. This strategic process is simple, highly efficient, and amenable to large-scale production.

[0008] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0009] The present invention provides an ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controllable particle size, comprising the following steps:

[0010] (1) Add anhydrous ethanol (EtOH) to deionized water to obtain a clear solution;

[0011] (2) The weighed dopamine hydrochloride powder was added to the above-mentioned clear solution, and the pH of the reaction solution was adjusted by 0.1 mol / L NaOH. The concentration of the dopamine hydrochloride solution in the system was 1-4 mg / mL, and the mixture was stirred continuously and assisted by ultrasonication. The reaction was carried out for 3-6 hours, and then the mixture was repeatedly washed with deionized water by high-speed centrifugation and dried to obtain polydopamine nanoparticles.

[0012] The existing technology involves "ultrasonic dispersion" or "polydopamine", which utilizes the film-forming properties of the surface of polydopamine. In the process of forming polydopamine coatings on different templates, ultrasound is used to effectively disperse the particles and prevent particle agglomeration.

[0013] In the application process of polydopamine or polydopamine-based surface coatings, there are ultrasonic dispersion treatment steps involved, but these applications all use ultrasound to disperse particles in liquid systems (such as the technology mentioned in the background technology), and are all used to disperse template particles during the preparation of polydopamine coatings.

[0014] Currently, there are no reports in the art of using ultrasound to form polydopamine nanoparticles through oxidative self-polymerization of dopamine, and even fewer reports of techniques for further controlling the size of polydopamine nanoparticles through ultrasound. Whether and how the size of polydopamine nanoparticles changes under ultrasound, or whether ultrasound can facilitate size control of polydopamine nanoparticles, remain unreported. Therefore, the precise ultrasound-assisted size control of polydopamine nanoparticles is the key innovation of the present invention.

[0015] Preferably, the volume fraction of the anhydrous ethanol EtOH in the reaction system is 10-30%.

[0016] Preferably, in step (2), the pH of the reaction solution is adjusted to 8.5-9.5. Conventional polydopamine synthesis pathways require a slightly alkaline environment. The present invention provides a specific pH range for the oxidative self-polymerization of dopamine under ultrasound.

[0017] Preferably, in step (2), the ultrasonic treatment time is 1-3 hours.

[0018] Preferably, in step (2), the frequency of the ultrasonic action is 22-40 KHz.

[0019] The ultrasonic treatment used for the aggregation and dispersion of particles in the liquid phase is short-term, while in the present invention, the ultrasonic treatment is long-term (1-3 hours). The present invention provides limitations on both the ultrasonic time and the ultrasonic frequency.

[0020] Preferably, in step (2), the high-speed centrifugation speed is 13000-14000 r / min.

[0021] Preferably, the particle size of the polydopamine nanoparticles is 162.81-666.73 nm.

[0022] Beneficial effects:

[0023] (1) The present invention uses ultrasound to mediate the dopamine formation process, generates reactive oxygen species (ROS) through ultrasound to accelerate the dopamine polymerization rate, and reduces the activation energy of polydopamine nanoparticle nucleation, thereby efficiently regulating the nucleation rate and growth rate of polydopamine, thereby obtaining polydopamine nanoparticles with controllable particle size and a large size range.

[0024] (2) The present invention can effectively control the size of polydopamine nanoparticles without the need for the introduction of additional external additives, so the obtained polydopamine nanoparticles are high in purity, free of other impurities, and have high biosafety.

[0025] (3) The ultrasonic action of the present invention does not have a negative impact on the morphology and structure of polydopamine nanoparticles, avoiding the disadvantage of uneven morphology existing in other external energy fields, and can reduce its reaction activation energy while improving the dispersibility of dopamine monomers.

[0026] (4) The preparation method of the present invention does not require a long oxidative polymerization reaction of dopamine monomer, which is time-saving and efficient, and the process is simple and easy to promote and mass-produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the preparation process of polydopamine nanoparticles of the present invention;

[0028] Figure 2 FTIR spectra of the dopamine raw material and polydopamine nanoparticles in Example 1 of the present invention;

[0029] Figure 3 The color changes of the solutions at different reaction times in Example 1 and Comparative Example 1 of the present invention are shown in the following photos:

[0030] Figure 4 This is a SEM image of polydopamine nanoparticles prepared in Example 2 of the present invention;

[0031] Figure 5 This is a SEM image of polydopamine nanoparticles prepared in Example 3 of the present invention;

[0032] Figure 6 This is the size distribution result of the polydopamine nanoparticles prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0034] like Figure 1 As shown, first, a certain amount of EtOH is dissolved in deionized water under magnetic stirring; then, weighed dopamine hydrochloride powder is added to the above-mentioned clear solution, and 0.1 mol / L NaOH solution is added to adjust the pH of the reaction solution to 8.5-9.5, while assisting with ultrasonic action and continuous magnetic stirring. The reaction is carried out for 3-6 hours, and then the reaction is carried out by high-speed centrifugation, repeated washing with deionized water, and drying to obtain polydopamine nanoparticles.

[0035] Example 1

[0036] Accurately measure 30 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0037] 200 mg of dopamine hydrochloride was accurately weighed and added to the clear solution. 0.1 mol / L NaOH solution was then added to adjust the pH of the reaction solution to 9, and the solution was then topped up with deionized water so that the total volume of deionized water, EtOH, and NaOH solution was 100 mL. At this point, the volume fraction of EtOH in the reaction system was 30%, and the concentration of the dopamine hydrochloride solution was 2 mg / mL.

[0038] An ultrasonic probe was placed in the solution and ultrasonicated for 3 hours at an ultrasonic frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 r / min for 15 minutes, washed with deionized water, centrifuged at 13,000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0039] The size distribution of polydopamine nanoparticles is shown in Table 1. The results show that the average size of polydopamine nanoparticles is 381.25 nm, and d10, d50, and d90 are 291.34 nm, 352.41 nm, and 407.81 nm, respectively.

[0040] Table 1 Size distribution of polydopamine nanoparticles

[0041]

[0042] Figure 2 This is the infrared spectrum of the dopamine raw material and polydopamine nanoparticles in Example 1. The results show that 1608 cm -1 The peak at 1508 cm is the overlapping peak of C=C vibration and NH bending vibration in polydopamine. -1 The peak at 3400 cm is the stretching vibration of NH in the polydopamine structure. -1The broad peak at 400 nm is formed by the stretching vibration of NH and OH of the phenol group. Thus, polydopamine was successfully synthesized by the ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controllable particle size.

[0043] Example 2

[0044] Accurately measure 30 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0045] 200 mg of dopamine hydrochloride, accurately weighed, was added to the clear solution, and 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9. The total volume of deionized water, EtOH, and NaOH solution was maintained at 100 mL. At this point, the volume fraction of EtOH in the reaction system was 30%, and the concentration of the dopamine hydrochloride solution was 2 mg / mL.

[0046] An ultrasonic probe was placed in the solution and sonicated for 1.5 hours at a frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 rpm for 15 minutes, rinsed with deionized water, centrifuged at 13,000 rpm for 15 minutes, and dried at 60°C to produce polydopamine nanoparticles. Table 2 shows the size distribution of the polydopamine nanoparticles, which shows an average size of 431.08 nm, with d10, d50, and d90 values ​​of 308.58, 394.44, and 482.66 nm, respectively.

[0047] Figure 4 This is a SEM image of the polydopamine nanoparticles prepared in Example 2. As can be seen from the figure, the method of the present invention successfully synthesized spherical polydopamine nanoparticles, which are evenly distributed, well dispersed, and highly spherical.

[0048] Table 2 Size distribution of polydopamine nanoparticles in Example 2

[0049]

[0050] Example 3

[0051] Accurately measure 30 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0052] 100 mg of dopamine hydrochloride, accurately weighed, was added to the clear solution, and 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9, maintaining the total volume of deionized water, EtOH, and NaOH solution at 100 mL. At this point, the volume fraction of EtOH in the reaction system was 30%, and the concentration of the dopamine hydrochloride solution was 1 mg / mL.

[0053] An ultrasonic probe was placed in the solution and sonicated for 3 hours at a frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 rpm for 15 minutes, rinsed with deionized water, centrifuged at 13,000 rpm for 15 minutes, and then dried at 60°C to produce polydopamine nanoparticles. Table 3 shows the size distribution of the polydopamine nanoparticles, which shows an average size of 162.81 nm, with d10, d50, and d90 values ​​of 123.74 nm, 149.02 nm, and 172.79 nm, respectively.

[0054] Table 3 Size distribution of polydopamine nanoparticles in Example 3

[0055]

[0056] Figure 5 This is an SEM image of the polydopamine nanoparticles prepared in Example 3. The synthesized polydopamine nanoparticles are evenly dispersed and exhibit spherical characteristics.

[0057] Example 4

[0058] Accurately measure 30 mL of EtOH and dissolve it in 50 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0059] 400 mg of dopamine hydrochloride, accurately weighed, was added to the clear solution, and 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9, maintaining the total volume of deionized water, EtOH, and NaOH solution at 100 mL. At this point, the volume fraction of EtOH in the reaction system was 30%, and the concentration of the dopamine hydrochloride solution was 4 mg / mL.

[0060] An ultrasonic probe was placed in the solution and ultrasonicated for 3 hours at an ultrasonic frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 r / min for 15 minutes, washed with deionized water, centrifuged at 13,000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0061] Table 4 shows the size distribution of polydopamine nanoparticles in Example 4. The results show that the average size of the polydopamine nanoparticles is 666.73 nm, and d10, d50, and d90 are 508.99 nm, 620.3 nm, and 739.21 nm, respectively.

[0062] Table 4 Size distribution of polydopamine nanoparticles in Example 4

[0063]

[0064] Example 5

[0065] Accurately measure 10 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0066] 200 mg of dopamine hydrochloride, accurately weighed, was added to the clear solution, and 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9, maintaining the total volume of deionized water, EtOH, and NaOH solution at 100 mL. At this point, the volume fraction of EtOH in the reaction system was 10%, and the concentration of the dopamine hydrochloride solution was 2 mg / mL.

[0067] An ultrasonic probe was placed in the solution and ultrasonicated for 1 hour at an ultrasonic frequency of 40 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 14,000 r / min for 15 minutes, washed with deionized water, centrifuged at 14,000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0068] Table 5 shows the size distribution of polydopamine nanoparticles in Example 5. The results show that the average size of the polydopamine nanoparticles is 393.12 nm, and d10, d50, and d90 are 343.65 nm, 372.91 nm, and 403.02 nm, respectively.

[0069] Table 5 Size distribution of polydopamine nanoparticles in Example 5

[0070]

[0071] Example 6

[0072] Accurately measure 30 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0073] 200 mg of dopamine hydrochloride accurately weighed was added to the above clear solution, and 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 8.5, while maintaining the total volume of deionized water, EtOH, and NaOH solution at 100 mL.

[0074] An ultrasonic probe was placed in the solution and ultrasonicated for 3 hours at an ultrasonic frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 r / min for 15 minutes, washed with deionized water, centrifuged at 13,000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0075] Table 6 shows the size distribution of polydopamine nanoparticles in Example 6. The results show that the average size of the polydopamine nanoparticles is 443.58 nm, and d10, d50, and d90 are 355.19 nm, 414.4 nm, and 486.1 nm, respectively.

[0076] Table 6 Size distribution of polydopamine nanoparticles in Example 6

[0077]

[0078] Example 7

[0079] Accurately measure 30 mL of EtOH and dissolve it in 50 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0080] 200 mg of dopamine hydrochloride accurately weighed was added to the above clear solution, and then 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9.5, and the total volume of deionized water, EtOH and NaOH solution was kept at 100 mL.

[0081] An ultrasonic probe was placed in the solution and ultrasonicated for 3 hours at an ultrasonic frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 6 hours, it was centrifuged at 13,000 r / min for 15 minutes, washed with deionized water, centrifuged at 13,000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0082] Figure 6 This is the size distribution result of the polydopamine nanoparticles prepared in Example 7 of the present invention. As can be seen from the figure, the polydopamine nanoparticles show a good size distribution. The average size of the polydopamine nanoparticles is 186.11 nm, and d10, d50, and d90 are 138.89 nm, 176.9 nm, and 202.88 nm, respectively.

[0083] Example 8

[0084] Accurately measure 15 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0085] 200 mg of dopamine hydrochloride accurately weighed was added to the above clear solution, and then 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9, and the total volume of deionized water, EtOH and NaOH solution was kept at 100 mL.

[0086] An ultrasonic probe was placed in the solution and ultrasonicated for 1 hour at a frequency of 22 kHz while maintaining continuous magnetic stirring. After the solution reacted for 3 hours, it was centrifuged at 13,000 rpm for 15 minutes, washed with deionized water, centrifuged at 13,000 rpm for 15 minutes, and then fully dried at 60°C to produce polydopamine nanoparticles. The method of the present invention successfully synthesized spherical polydopamine nanoparticles with high sphericity and uniform distribution.

[0087] Comparative Example 1

[0088] Accurately measure 30 mL of EtOH and dissolve it in 60 mL of deionized water while maintaining magnetic stirring to obtain a clear solution.

[0089] 200 mg of dopamine hydrochloride accurately weighed was added to the above clear solution, and then 0.1 mol / L NaOH solution was added to adjust the pH of the reaction solution to 9. The total volume of deionized water, EtOH, and NaOH solution was kept at 100 mL, while continuous magnetic stirring was maintained. After the solution was reacted for 6 hours, it was centrifuged at 13000 r / min for 15 minutes, washed with deionized water, centrifuged at 13000 r / min for 15 minutes, and then fully dried at 60°C to obtain polydopamine nanoparticles.

[0090] Figure 3 The following are photos of the color changes of the reaction solutions at different times in Example 1 and Comparative Example 1. It can be seen that the color change rate of the solution was significantly increased after ultrasound treatment, indicating a faster generation rate of polydopamine.

[0091] Table 7 shows the size distribution of the polydopamine nanoparticles in Comparative Example 1. The results show that the average size of the polydopamine nanoparticles is 495.59 nm, and the d10, d50, and d90 are 411.34 nm, 472.11 nm, and 530.91 nm, respectively. Compared with Example 1 and Comparative Example 1, the size of the polydopamine nanoparticles prepared under ultrasound is significantly reduced.

[0092] Table 7 Comparative Example Polydopamine Nanoparticle Size Distribution

[0093]

[0094] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. An ultrasound-assisted method for preparing polydopamine nanoparticles with precisely controllable particle size, characterized in that: The following steps are involved: (1) Add anhydrous ethanol (EtOH) to deionized water to obtain a clear solution; (2) Add the weighed dopamine hydrochloride powder to the above-mentioned clear solution, and adjust the pH of the reaction solution with 0.1 mol / L NaOH. The concentration of the dopamine hydrochloride solution in the system is 1-4 mg / mL. Stir continuously and ultrasonicate for 3-6 hours. Then, high-speed centrifugation, water washing, and drying are performed to obtain polydopamine nanoparticles. In step (1), the volume fraction of the anhydrous ethanol EtOH in the reaction system is 10-30%; In step (2), the pH of the reaction solution is adjusted to 8.5-9.5; the ultrasonic treatment time is 1-3 hours; the ultrasonic treatment frequency is 22-40 KHz; and the high-speed centrifugation speed is 13000-14000 r / min.

2. The preparation method according to claim 1, characterized in that The particle size of the polydopamine nanoparticles is 162.81-666.73 nm.

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