Preparation method and application of Ag-Au eight-branch nanoparticles

Abstract

The invention relates to the field of precious metal nanoparticles, in particular to a preparation method and application of Ag-Au eight-branch nanoparticles, and the preparation method comprises the following steps: adding a silver nitrate solution and histidine into ultrapure water, stirring, adjusting the pH value to 12-12.5, adding a hydroxylamine solution, stirring, adding a PVP (Polyvinyl Pyrrolidone) aqueous solution, stirring, centrifuging and washing to obtain Ag-Au eight-branch nanoparticles; dispersing the precipitate in pure water to obtain eight-branch-shaped Ag nanoparticles; the preparation method comprises the following steps: adding eight-branch-shaped Ag nanoparticles dispersed in pure water into a PVP (Polyvinyl Pyrrolidone) aqueous solution, stirring, dropwise adding a chloroauric acid solution, stirring, centrifuging, washing, and dispersing precipitates in ultrapure water to obtain the Ag-Au eight-branch nanoparticles. The Ag-Au eight-branch nano particle has high stability and good photo-thermal conversion performance, meanwhile, the Ag-Au eight-branch nano particle has good peroxidase activity, and the Ag-Au eight-branch nano particle is expected to have huge application potential in antibacterial and anti-tumor treatment.

Description

Technical Field

[0001] The invention relates to the field of noble metal nanoparticles, in particular to a preparation method and application of Ag-Au eight-branch nanoparticles. Background Art

[0002] Photothermal therapy (PTT) is a therapeutic technology that converts light energy into heat energy through photothermal agents, denatures cell active substances such as proteins, nucleic acids, enzymes, etc. through high heat, thereby inhibiting bacterial growth or destroying tumors. Due to its unique advantages such as minimally invasive, controllable, efficient, and highly penetrable, photothermal therapy has become a hot topic of research in recent years. At present, a variety of photothermal materials have been developed to destroy tumors or inhibit bacterial growth, mainly including four major categories: precious metal nanomaterials, carbon-based nanomaterials, semiconductor nanomaterials, and organic materials. Among them, precious metal nanomaterials have become the leader in this field due to their huge specific surface area and unique optical, electrical, and catalytic properties, and have won widespread attention.

[0003] Due to the powerful surface plasmon resonance (SPR) effect and the controllability of synthesis, noble metal materials are considered to be simple and effective photothermal materials. Noble metal materials have excellent optical and photothermal properties, with high absorption cross-sections in the near infrared (NIR) region. After absorbing near infrared light, they convert it into high heat, thereby producing local hyperthermia. Among them, silver (Ag) nanostructures of different shapes and sizes have great application prospects in photothermal therapy, such as nanosilver spheres, nanosilver triangles, and silver nanocages. However, Ag nanoparticles are unstable and prone to violent and rapid oxidation and subsequent structural degradation, which leads to the reduction of the physical and chemical properties of Ag nanoparticles and the weakening of the photothermal effect. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a method for preparing Ag-Au eight-branch nanoparticles.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing Ag-Au eight-branch nanoparticles comprises the following steps:

[0007] Synthesis of eight-branched Ag nanoparticles: adding 500 μL of 48-52 mmol / L silver nitrate solution and 200 μL of 0.25-1 mmol / L histidine to 94.3 mL of ultrapure water at room temperature and stirring, then adding sodium hydroxide solution thereto to obtain a first mixed solution, so that the pH value of the first mixed solution is 12-12.5, stirring the first mixed solution, adding 1 mL of 48-52 mmol / L hydroxylamine solution to the first mixed solution to obtain a second mixed solution, stirring the second mixed solution, adding 5 mL of a 5% by mass PVP (polyvinyl pyrrolidone) aqueous solution to the second mixed solution to obtain a third mixed solution, stirring, centrifuging and washing the third mixed solution, and dispersing the precipitate in 2.3 mL of pure water to obtain eight-branched Ag nanoparticles;

[0008] Synthesis of Ag-Au eight-branched nanoparticles: add the eight-branched Ag nanoparticles dispersed in 2.3 mL of pure water to 43.5-44 mL of 1 g / L PVP aqueous solution and stir for 8-13 minutes to obtain a fourth mixed solution, add 0.5-2 mL of tetrachloroauric acid solution to the fourth mixed solution, stir, centrifuge and wash, and disperse the precipitate in ultrapure water to obtain Ag-Au eight-branched nanoparticles.

[0009] As a further solution of the present invention: the stirring rate in ultrapure water is 1000 rpm, and the stirring time is 2 minutes.

[0010] As a further solution of the present invention: the concentration of the sodium hydroxide solution is 0.2 mol / L.

[0011] As a further solution of the present invention: the time for stirring the first mixed solution and the time for stirring the second mixed solution are both 1 minute.

[0012] As a further solution of the present invention: the centrifugal speed is 8000 rpm, the centrifugal time is 5 minutes, and the number of washings is three times.

[0013] As a further solution of the present invention: the concentration of the tetrachloroauric acid solution is 0.8 mmol / L.

[0014] The invention also provides the application of the Ag-Au eight-branch nanoparticles obtained by the preparation method in the preparation of antibacterial drugs.

[0015] The invention also provides the application of the Ag-Au eight-branch nanoparticles obtained by the preparation method in the preparation of anti-tumor drugs.

[0016] Compared with the prior art, the invention has the following beneficial effects: the invention plates a gold layer on the surface of the eight-branch silver nanoparticles to synthesize a new gold-silver alloy structure - Ag-Au eight-branch nanoparticles; the Ag-Au eight-branch nanoparticles have high stability and good photothermal conversion performance, enhance the absorption of near-infrared light, and further improve the photothermal conversion efficiency, which is as high as 41.5%. The Ag-Au eight-branch nanoparticles have good peroxidase activity, and the Michaelis constant (K) for hydrogen peroxide (H2O2) is m ) is 58.6mmol / L. Since Ag-Au eight-branch nanoparticles have both photothermal effect and catalytic activity, they can be applied to nanozyme-photothermal therapy (NPT), converting light energy into heat energy under near-infrared laser irradiation, while catalyzing low concentrations of exogenous H2O2 to produce highly toxic hydroxyl radicals (·OH), which is expected to show great application potential in antibacterial and anti-tumor treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 TEM image of eight-dendritic Ag nanoparticles in an embodiment of the present invention.

[0018] Figure 2 This is a TEM image of Ag-Au eight-branched nanoparticles obtained by a method for preparing Ag-Au eight-branched nanoparticles in an embodiment of the present invention.

[0019] Figure 3 This is a SEM image of eight-dendritic Ag nanoparticles in an embodiment of the present invention.

[0020] Figure 4 This is a SEM picture of Ag-Au eight-branched nanoparticles obtained by a method for preparing Ag-Au eight-branched nanoparticles in an embodiment of the present invention.

[0021] Figure 5 It is the UV-visible-near infrared absorption spectrum of eight-branched Ag nanoparticles and Ag-Au eight-branched nanoparticles in the embodiment of the present invention.

[0022] Figure 6 In the present invention, 50 μg mL -1 Temperature changes of eight-branched Ag nanoparticles and Ag-Au eight-branched nanoparticles under 808nm laser irradiation for 300s.

[0023] Figure 7 The Ag-Au eight-branch nanoparticles with different concentrations in the embodiment of the present invention are shown in Figure 1.5Wcm -2 Temperature change of 808 nm laser irradiation for 300 s.

[0024] Figure 8This is the UV-visible absorption spectrum of Ag-Au eight-branch nanoparticles catalyzed with TMB and H2O2 as substrates in the embodiment of the present invention.

[0025] Fig. 9 This is the double reciprocal curve of the Ag-Au eight-branch nanoparticles catalyzed as peroxidase when H2O2 is used as substrate in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Ag nanostructures have excellent photothermal properties and can convert light energy into heat, making them a good photothermal agent. However, Ag nanoparticles are unstable and prone to violent and rapid oxidation and subsequent structural degradation, which leads to reduced physical and chemical properties of Ag nanoparticles and weakened photothermal effects. One possible way to solve this problem is to coat the surface of Ag nanoparticles with other precious metal elements, such as gold (Au), palladium (Pd) and platinum (Pt), to form an alloy structure. For example, the chemical stability of Ag nanoparticles will be greatly improved after Au plating, and the surface plasmon resonance absorption of nanomaterials can be adjusted from visible light to near-infrared regions, thereby greatly improving the photothermal effect of gold-silver alloy materials. In addition, gold-silver alloy materials also have intrinsic catalytic activity (i.e., peroxidase activity) and produce a large amount of reactive oxygen species (ROS), which is expected to be used in synergistic antibacterial and anti-tumor applications with photothermal therapy. In order to improve the stability of Ag nanoparticles and enhance the photothermal effect, the present invention coats the surface of eight-branched Ag nanoparticles with an Au layer to synthesize a new gold-silver alloy structure-Ag-Au eight-branched nanoparticles. Ag-Au eight-branched nanoparticles have good photothermal effect and catalytic activity, and have great application potential in nanoenzyme photothermal therapy. In the present invention, histidine is used as a morphology regulator, silver nitrate is reduced by hydroxylamine in an alkaline environment to obtain eight-branched Ag nanoparticles, and then Ag-Au eight-branched nanoparticles are obtained by electrical replacement.

[0028] Example 1: Reference Figure 1 A method for preparing Ag-Au eight-branch nanoparticles comprises the following steps:

[0029] Synthesis of eight-branched Ag nanoparticles: 500 μL of 50 mmol / L silver nitrate solution and 200 μL of 0.25 mmol / L histidine were added to 94.3 mL of ultrapure water at room temperature and stirred, and then sodium hydroxide solution was added thereto to obtain a first mixed solution, so that the pH value of the first mixed solution was 12.2, and after stirring the first mixed solution for 1 minute, 1 mL of 50 mmol / L hydroxylamine solution was added to the first mixed solution to obtain a second mixed solution, and the second mixed solution was stirred for 1 minute and 5 mL of 5% PVP aqueous solution was added to the second mixed solution to obtain a third mixed solution, and the third mixed solution was stirred for 5 minutes, and then centrifuged at 8000 rpm for 5 minutes, and the third mixed solution was washed three times, and the precipitate was dispersed in 2.3 mL of pure water to obtain eight-branched Ag nanoparticles. Unless otherwise specified, all experiments were carried out at room temperature (25±2°C);

[0030] Synthesis of Ag-Au eight-branched nanoparticles: Ag-Au eight-branched nanoparticles were synthesized by galvanic replacement reaction, and the eight-branched Ag nanoparticles dispersed in 2.3 mL of pure water were added to 43.7 mL of 1 g / L PVP aqueous solution and stirred for 10 minutes to obtain a fourth mixed solution. 1.5 mL of 0.8 mmol / L tetrachloroauric acid solution was added dropwise to the fourth mixed solution, stirred for 10 minutes, and then centrifuged at 8000 rpm for 5 minutes. The mixture was washed three times, and the precipitate was dispersed in ultrapure water to obtain Ag-Au eight-branched nanoparticles. The Ag-Au eight-branched nanoparticles were stored in ultrapure water at 4°C and protected from light.

[0031] One drop of the eight-branched Ag nanoparticle solution and one drop of the Ag-Au eight-branched nanoparticle solution obtained in Example 1 were dropped onto a 300-mesh carbon-coated copper grid and air-dried to obtain a sample. The sample was photographed using a HT7820 transmission electron microscope at an accelerating voltage of 100 kV. The results are as follows: Figure 1-2 .

[0032] One drop of the eight-branched Ag nanoparticle solution and one drop of the Ag-Au eight-branched nanoparticle solution obtained in Example 1 were dropped onto a 3×3 mm silicon wafer and air-dried to obtain a sample. The sample was photographed using a SU-8020 / QUANT AX200 cold field emission scanning electron microscope at an accelerating voltage of 3.0 kV. The results are shown in FIG. Figure 3-4 .

[0033] Figure 1 and Figure 3 The diameter of the eight-branched Ag nanoparticles is about 141±4.3nm, and the branch length is about 60±0.7nm. Figure 2 and Figure 4The diameter of the Ag-Au eight-branch nanoparticles is 155±12.2nm, and the branch length is 78±1.0nm. The UV-Vis-NIR absorption spectrum is measured, and the results are shown in Figure 5 The UV-Vis-NIR absorption spectrum showed that the absorption peak of Ag-Au eight-branch nanoparticles was red-shifted from 654nm of Ag nanomaterials to 882nm. In addition, the color of the solution also changed from yellow-green to blue, all of which indicated that Ag-Au eight-branch nanoparticles were successfully synthesized.

[0034] The concentration was 50 μg mL -1 Ag-Au eight-branch nanoparticle solution, different powers (0.5, 0.9, 1.2, 1.5, 1.9 W cm -2 ) with near-infrared 808 nm laser for 300 s, and record the temperature rise of the sample. Prepare different concentrations (10, 20, 30, 40, 50 μg mL -1 ) of Ag-Au eight-branch nanoparticles, irradiated with near-infrared 808nm laser for 300s (1.5Wcm -2 ), record the temperature rise of the sample. -1 The heating effect of Ag nanomaterials and Ag-Au nanoparticles. Figure 6 As shown in the figure, the temperature rise of H2O is negligible. The temperature of Ag nanomaterials and Ag-Au eight-branch nanoparticles rises to 39.9℃ and 49.8℃ respectively after 5 minutes of irradiation, which proves that the temperature rise effect of Ag-Au eight-branch nanoparticles is better. Next, the laser power is fixed at 1.5wcm -2 , concentrations of 50, 40, 30, 20, and 10 μg mL -1 The temperatures of the eight-branch Ag-Au nanoparticle sample rose to 49.8, 47.1, 43.7, 39.3, and 33.0 °C, respectively, after 5 minutes of irradiation. Figure 7 The higher the concentration of the photothermal material, the higher the temperature of the sample, and the better the photothermal effect. The photothermal conversion efficiency of the Ag-Au eight-branch nanoparticles calculated by the cooling curve can reach 41.5%, proving that the Ag-Au eight-branch nanoparticles have a good photothermal effect.

[0035] 3,3',5,5'-Tetramethylbenzidine (TMB) (10 mM, 100 μL), hydrogen peroxide H2O2 (10-50 mM, 100 μL) and Ag-Au eight-branch nanoparticles (500 μg mL -1 , 100 μL,) were added one by one into Britton-Robinson (BR) buffer (700 μL, pH = 5.0), and the absorbance change of the solution at 652 nm was monitored by UV-visible spectrophotometer for kinetic test. Kinetic parameters, maximum reaction rate Vmax and Michaelis constant K m , the initial reaction rate V0 and substrate concentration [S] are fitted and calculated according to the formula: V0 = V max ×[S] / (K m +[S]), the results are shown in Figure 8-9 . Figure 8 It can be seen that the reaction solution produced a characteristic absorption peak at 652nm, indicating that colorless TMB quickly formed blue oxidized TMB (Ox-TMB). The blank control group (TMB+H2O2) had no absorption at 652nm. The TMB color development experiment confirmed that the Ag-Au eight-branch nanoparticles had peroxidase activity. The main mechanism was that H2O2 generated ·OH under the action of Ag-Au peroxidase, and ·OH could oxidize colorless TMB into blue oxTMB. Fig. 9 The double reciprocal curve in can be used to determine the Michaelis-Menten constant (Km) of Ag-Au eight-branched nanoparticles for H2O2. The Km value of Ag-Au eight-branched nanoparticles is 58.6mM, which indicates that Ag-Au eight-branched nanoparticles have a high affinity for its substrate H2O2.

[0036] In summary, the Ag-Au eight-branch nanoparticles prepared in the present invention have good photothermal effect and peroxidase activity, and are a nanozyme-photothermal antibacterial platform, which is expected to show great application potential in antibacterial and anti-tumor treatment.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing Ag-Au eight-branch nanoparticles, comprising the following steps: Synthesis of eight-branched Ag nanoparticles: adding 500 μL of 48-52 mmol / L silver nitrate solution and 200 μL of 0.25-1 mmol / L histidine to 94.3 mL of ultrapure water at room temperature and stirring, then adding sodium hydroxide solution thereto to obtain a first mixed solution, so that the pH value of the first mixed solution is 12-12.5, stirring the first mixed solution, adding 1 mL of 48-52 mmol / L hydroxylamine solution to the first mixed solution to obtain a second mixed solution, stirring the second mixed solution, adding 5 mL of a 5% by mass PVP aqueous solution to the second mixed solution to obtain a third mixed solution, stirring, centrifuging and washing the third mixed solution, and dispersing the precipitate in 2.3 mL of pure water to obtain eight-branched Ag nanoparticles; Synthesis of Ag-Au eight-branched nanoparticles: add the eight-branched Ag nanoparticles dispersed in 2.3 mL of pure water to 43.5-44 mL of 1 g / L PVP aqueous solution and stir for 8-13 minutes to obtain a fourth mixed solution, add 0.5-2 mL of tetrachloroauric acid solution to the fourth mixed solution, stir, centrifuge and wash, and disperse the precipitate in ultrapure water to obtain Ag-Au eight-branched nanoparticles.

2. The method for preparing Ag-Au eight-branch nanoparticles according to claim 1, characterized in that: The stirring rate in ultrapure water was 1000 rpm, and the stirring time was 2 minutes.

3. The method for preparing the Ag-Au eight-branch nanoparticles according to claim 1 or 2, characterized in that: The concentration of the sodium hydroxide solution is 0.2 mol / L.

4. The method for preparing Ag-Au eight-branch nanoparticles according to claim 1, characterized in that: The centrifugal speed was 8000 rpm, the centrifugal time was 5 minutes, and the washing times were three times.

5. The method for preparing Ag-Au eight-branch nanoparticles according to claim 1, characterized in that: The concentration of the tetrachloroauric acid solution is 0.8 mmol / L.

6. Use of the Ag-Au eight-branched nanoparticles obtained by the method for preparing the Ag-Au eight-branched nanoparticles according to any one of claims 1 to 5 in preparing antibacterial drugs.

7. Use of the Ag-Au eight-branched nanoparticles obtained by the method for preparing the Ag-Au eight-branched nanoparticles according to any one of claims 1 to 5 in preparing anti-tumor drugs.

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