Preparation method of near-infrared second-region photo-thermal agent based on dendritic silver particles

Abstract

The invention relates to a preparation method of a near-infrared two-zone photo-thermal agent based on dendritic silver particles, which comprises the following steps: quickly adding a sodium hydroxide solution into a silver nitrate solution under the conditions of room temperature and continuous stirring, uniformly mixing, and adjusting the pH value of the solution to be alkaline; after a certain period of time, adding a hydroxylamine solution; and reacting for a certain time, adding a polyvinylpyrrolidone solution, continuously stirring for 30 seconds, centrifuging, and purifying to obtain the product. According to the method, silver nitrate is used as a silver source, hydroxylamine is used as a reducing agent, polyvinylpyrrolidone (PVP) is used as a stabilizer, and the silver particles with the size range of 1175-80 nm and the branch length / central core size ratio range of 1.6: 1-0: 1 can be prepared in one step by regulating and controlling the pH value of a solution. Under the irradiation of 1064 nm laser (1.9 W / cm < 2 >), the photothermal efficiency of the dendritic silver particle photothermal agent prepared under optimized conditions can reach up to 43.1%. According to the preparation method of the near-infrared second-region photothermal agent based on the dendritic silver particles, a substrate does not need to be used, the preparation method is simple, the regulation and control effect is good, and the obtained particles are high in photothermal conversion efficiency and good in photothermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of micro / nano material preparation, and in particular relates to a method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles. Background Art

[0002] Photothermal agents are inorganic materials or organic molecules that can convert light energy into heat energy. They can kill tumor cells under the irradiation of external light sources such as near-infrared light, and thus have become a research hotspot for photothermal therapy ( Int. J. Mol. Sci. 2022,23, 7909-7924). Developing photothermal agents with near-infrared absorption and high photothermal conversion efficiency is the key to achieving ideal photothermal therapy effects. Photothermal agents are mainly divided into two categories: inorganic and organic. Among them, photothermal agents based on inorganic metal particles (such as Au, Ag, Pt, Cu, etc.) have good antioxidant properties, biocompatibility, excellent surface plasmon resonance effect (LSPR) and high photothermal conversion efficiency, and have become the most studied inorganic photothermal agents ( J. Phys. Chem. C 2024,128, 13778-13786). Compared with other precious metals, metallic silver particles have a higher extinction coefficient and are relatively cheap. Therefore, inorganic photothermal agents based on silver particles have better photothermal performance and are more suitable for quantitative production and application.

[0003] In recent years, researchers have successfully prepared a series of silver-based photothermal agents by loading silver particles on substrates. For example, in 2023, Yang et al. prepared Ag nanoparticle-doped SnS2 composite materials, which were exposed to 808 nm laser (1.2 W / cm 2 ) The photothermal conversion efficiency of the composite material under irradiation conditions η 30.0% ( Colloids Surf., A 2023, 667, 131407-131414); In 2024, Jiang et al. prepared Ag nanoparticle-loaded lignin composites. The silver-based composites were irradiated by 808 nm laser (1.8 W / cm 2 ) Photothermal conversion efficiency under irradiation conditions η 29.7% ( Int. J. Biol. Macromol. 2024, 262, 129827-129835); In 2024, Li et al. reported the AgPd loaded with elm pod polysaccharide. 1.5 The nanoparticle composite material was exposed to 808 nm laser (1.75 W / cm 2 ) under irradiation conditions η The value is 39.7% ( Int. J. Biol. Macromol.2024, 264, 130673-130680). Most of these silver-based near-infrared photothermal agents are suitable for near-infrared region I (700-1000 nm). However, biological tissues significantly absorb and scatter light in the near-infrared region I, resulting in poor tissue penetration depth and spatial resolution, which limits the application of these silver-based photothermal agents in vivo in fields such as optical imaging and phototherapy. Biological tissues weakly absorb and scatter light in the near-infrared region II (1000-1700 nm), so near-infrared region II photothermal agents have greater application value in vivo. At present, only a few literatures have reported silver-based photothermal agents suitable for near-infrared region II. For example, in 2022, Li et al. prepared an ultra-thin layered CoFe double hydroxide-supported Ag@Ag2O core / shell particle photothermal agent, and utilized the plasma coupling between the substrate and the silver particles and the reduction of the band gap caused by the vacancy defects of Ag2O to enhance the absorption in the second region of the near-infrared. The photothermal conversion efficiency of the photothermal agent under 1064 nm laser irradiation was as high as 76.9% ( ACS Biomater. Sci. & Eng. 2022, 8, 540-550). In 2024, Zheng et al. prepared a silver particle-modified carbon nanotube film material, which formed a silver / carbon nanotube heterojunction and exhibited photothermal conversion performance under 1064 nm near-infrared light irradiation conditions ( Carbon 2024, 219, 118810-118818). However, the preparation methods of these near-infrared second-zone silver-based photothermal agents are relatively complicated and the steps are cumbersome. There are few reports on near-infrared photothermal agents based on anisotropic pure silver particles without substrates, such as near-infrared photothermal agents based on dendritic pure silver particles. Compared with silver particle / substrate complexes, dendritic silver particles can avoid the use of substrates and have simple preparation steps; in addition, by regulating the ratio of the branch length to the central core size of the dendritic silver particles, its LSPR peak position can be more accurately and continuously regulated ( Appl. Surf. Sci . 2020, 532, 147457-147465; Mater. Chem. Front 2021, 5, 5478-5485), which makes it easier to achieve the overlap of its LSPR peak with the near-infrared excitation light, thereby enhancing the photothermal effect. Up to now, it is still a challenge to prepare a substrate-free near-infrared second-zone photothermal agent based on dendritic pure silver particles. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the background technology and provide a method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles with simple steps. The method adopts a one-pot method and can prepare silver particles with a size of 1175~80 nm and a branch length / central core size ratio ranging from 1.6:1 to 0:1 in just one step. The optimized dendritic silver particle photothermal agent can be used for the preparation of near-infrared second-zone photothermal agents under the influence of 1064 nm laser (1.9 W / cm 2) irradiation, the photothermal efficiency can be as high as 43.1%, and the photothermal stability is high.

[0005] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles comprises the following steps: Under normal temperature and continuous stirring conditions, sodium hydroxide solution is quickly added to silver nitrate solution, mixed evenly, and the pH of the solution is adjusted to alkaline. After a certain interval, a reducing agent hydroxylamine solution is added. After a certain reaction time, polyvinyl pyrrolidone solution is added, and stirring is continued for 30 seconds, followed by centrifugation and purification.

[0006] In the preparation method of the present invention, the stirring speed is 1000 rpm.

[0007] In the above preparation method, the final concentration of silver nitrate in the reaction system is 0.25 mM.

[0008] Specifically, in the reaction system, the adjustment range of the solution pH is 10.2~11.9.

[0009] Furthermore, in the reaction system, the final concentration of hydroxylamine was 0.5 mM.

[0010] Furthermore, in the reaction system, the interval time is 10 seconds.

[0011] Furthermore, in the reaction system, the reaction time is 30 seconds.

[0012] 5%。 In the above-mentioned preparation method, the reaction system, the final mass fraction of polyvinyl pyrrolidone is 0.5%.

[0013] In the preparation method of the present invention, silver nitrate is used as the silver source, hydroxylamine is used as the reducing agent, and polyvinyl pyrrolidone (PVP) is used as the stabilizer. By adjusting the pH of the solution, silver particles with a size range of about 1175-80 nm and a branch length / central core size ratio range of 1.6:1-0:1 can be prepared in one step. The dendritic silver particle photothermal agent prepared under the optimized conditions was irradiated with a 1064 nm laser (1.9 W / cm 2 ) irradiation, the photothermal efficiency can be as high as 43.1%.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The method of the present invention adopts a wet chemical reduction method, and the experimental operation is simple. A substrate-free near-infrared second-zone photothermal agent based on dendritic pure silver particles can be prepared by a one-pot method.

[0015] 2. By changing the reaction conditions, dendritic silver particles with different branch length / central core size ratios can be prepared. When the pH value is 10.2-11.9, the size range of the obtained silver particles is about 1175 nm-80 nm, the branch length is about 450 nm-0 nm, the central core size is about 275 nm-80 nm, and the ratio of branch length / central core size is about 1.6:1-0:1. The ratio of branch length to central core size of the product dendritic silver particles is adjustable to meet a wider range of application needs.

[0016] 3. The near-infrared second-zone photothermal agent based on dendritic silver particles prepared by the present invention is 2 ) irradiation, the photothermal efficiency can be as high as 43.1%, and the photothermal stability is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a scanning electron microscope (SEM) image of silver particles prepared under the condition of pH=10.2 in Example 1 of the present invention.

[0018] Figure 2 : is a SEM image of silver particles prepared under the condition of pH=10.5 in Example 1 of the present invention.

[0019] Figure 3 : is a SEM image of silver particles prepared under the condition of pH=10.7 in Example 1 of the present invention.

[0020] Figure 4 : is a SEM image of silver particles prepared under the condition of pH=10.9 in Example 1 of the present invention.

[0021] Figure 5 : is a SEM image of silver particles prepared under the condition of pH=11.9 in Example 1 of the present invention.

[0022] Figure 6 It is the UV-visible absorption spectrum of the silver particles prepared under the condition of pH=10.2~11.9 in Example 1 of the present invention.

[0023] Figure 7 In Example 2 of the present invention, the silver particle solution and pure water with a volume of 1 mL prepared under different pH conditions were subjected to 1064 nm laser (1.9 W / cm 2 )Temperature difference under irradiation conditions Δ T Over time t The temperature difference Δ T = T - T surr , T The silver particle solution t The temperature of the moment,T surr is the ambient temperature.

[0024] Figure 8 The temperature difference Δ is the temperature difference of the silver particle solution prepared under pH=10.5 with a volume of 1 mL in Example 3 of the present invention during three consecutive cycles of "laser irradiation (heating)-laser off (cooling)" T Over time t The laser wavelength is 1064 nm and the laser power density is 1.9 W / cm 2 In each cycle, the laser irradiation time was 20 min and the laser off time was 20 min.

[0025] Fig. 9 The temperature difference Δ is the temperature difference of the silver particle solution with a volume of 1 mL and pH = 10.5 in Example 3 of the present invention during a "laser irradiation-laser off" cycle. T Over time t The laser wavelength is 1064nm and the laser power density is 1.9 W / cm 2 The laser irradiation time was 20 min, and the laser off time was 20 min.

[0026] Fig.10 In Example 3 of the present invention, the cooling time of the silver particle solution with a volume of 1 mL and pH = 10.5 undergoes a "laser irradiation-laser off" cycle t Follow-ln θ The change curve of θ = ( TT surr ) / ( T max -T surr ). The laser wavelength is 1064 nm and the laser power density is 1.9 W / cm 2 The laser irradiation time is 20 min, and the laser off time is 20 min. T max It is the highest temperature that the silver particle solution can reach under laser irradiation. DETAILED DESCRIPTION

[0027] The following are basic conditions used in the embodiments of the present invention, but the scope of implementation of the present invention is not limited to these conditions or these embodiments.

[0028] Ambient temperature 25°C, 1 atmosphere pressure; Water (H2O), density 1 g / mL, molecular weight 18 g / mol; Silver nitrate (AgNO3), molecular weight 169.7 g / mol; Sodium hydroxide (NaOH), molecular weight 40.00 g / mol; Hydroxylamine (NH2OH), molecular weight 33.03 g / mol; Polyvinylpyrrolidone (PVP), average molecular weight 24000 g / mol.

[0029] Example 1: A method for preparing a near-infrared second-zone photothermal agent based on dendritic pure silver particles Under room temperature and continuous stirring at 1000 rpm, a certain volume of 0.2 M NaOH solution was quickly added to the silver nitrate solution and mixed evenly. The pH of the silver nitrate solution was adjusted to 10.2, 10.5, 10.7, 10.9 and 11.9, respectively, so that the total volume of the final solution was 10 mL and the final concentration of silver nitrate was 0.25 mM. After stirring for 10 s, 100 μL of 50 mM hydroxylamine solution was added. After stirring for 30 s, 1 mL of 5% PVP solution was added, and the reaction was stopped after stirring for another 30 s to obtain a near-infrared second-zone photothermal agent based on dendritic silver particles.

[0030] The SEM images of the silver particles prepared in Example 1 are as follows: Figure 1 , 2 , 3, 4 and 5, from Figure 1-5 It can be seen that in the range of pH = 10.2~11.9, with the increase of pH value, the morphology of silver particles changes from dendrite to cube, and the branch length of silver particles gradually decreases, the particle surface gradually becomes smooth, and the size of the central core first increases and then decreases. When the pH values ​​are 10.2, 10.5, 10.7, 10.9 and 11.9, the size of silver particles is about 1175 nm, 960 nm, 470 nm, 240 nm and 80 nm, respectively, the branch length is about 450 nm, 290 nm, 90 nm, 0 nm and 0 nm, the central core size is about 275 nm, 380 nm, 290 nm, 240nm and 80 nm, and the ratio of branch length / central core size is 1.6:1, 0.8:1, 0.3:1, 0:1 and 0:1.

[0031] The UV-visible absorption spectrum of the silver particles prepared in Example 1 is as follows: Figure 6 As shown in the figure, the LSPR peak of silver particles gradually shifts from the second near-infrared region to the visible region (450 nm) with the increase of pH.

[0032] It can be seen from this example that the present invention can achieve regulation of the ratio of branch length / central core size and optical properties of dendritic silver particles by changing the pH value.

[0033] Example 2: Characterization of the photothermal conversion performance of silver particles prepared under different pH conditions 1 mL of silver particle solution and pure water prepared under different pH conditions were taken and laser beam with wavelength of 1064 nm (1.9 W / cm 2 ) for 20 min, and use an infrared thermal imager to record the temperature of the silver particle solution / pure water and the environment. T = TT surr , T Silver particle solution or pure water t The temperature of the moment, T surr is the ambient temperature.

[0034] The temperature difference Δ obtained in the above embodiment 2 T Over time t The change curve of Figure 7 As shown, from Figure 7 It can be seen that the temperature of the silver particle solutions prepared at pH 10.2, 10.5, 10.7, 10.9 and 11.9 increased by 8.8 ℃, 19.0 ℃, 11.8 ℃, 8.9 ℃ and 5.5 ℃ respectively under laser irradiation, while the temperature of pure water increased by 5.3 ℃.

[0035] It can be seen from this embodiment that the present invention can achieve regulation of the photothermal conversion performance of silver particles by changing the pH, and the dendritic silver particles prepared under pH 10.5 have the best photothermal conversion performance under 1064 nm laser irradiation.

[0036] Example 3: Determination of photothermal efficiency and characterization of photothermal stability of silver particles prepared under pH = 10.5 A 1 mL volume of the silver particle solution prepared at pH = 10.5 was placed under a laser with a wavelength of 1064 nm (1.9 W / cm 2 ) for 20 min, then turn off the laser switch and let the solution cool at room temperature for 20 min. The solution was subjected to three consecutive "laser irradiation-laser off" cycles, and the temperature change of the silver particle solution during the cycle was recorded.

[0037] The temperature difference Δ between the silver particle solution and the environment during the three "laser irradiation-laser off" cycles obtained in Example 3 above is T Over time t Changes such as Figure 8 As shown, from Figure 8 It can be seen that the maximum temperature that can be reached by the silver particle solution prepared under pH=10.5 remains basically unchanged after three cycles of "laser irradiation-laser off".

[0038] The temperature difference Δ between the silver particle solution and the environment during a "laser irradiation-laser off" cycle obtained in the above Example 3 is T Over time t Changes such as Fig. 9 As shown, -ln θ With cooling time t The change curve of Fig.10 As shown. θ = ( T- T surr ) / ( T max -T surr ), T max is the highest temperature reached by the silver particle solution under laser irradiation. 2 ) can achieve a photothermal conversion efficiency of up to 43.1% under irradiation.

[0039] It can be seen from this example that in the present invention, the silver particles prepared under the condition of pH=10.5 have good photothermal conversion effect and photothermal stability, and the photothermal conversion efficiency can be as high as 43.1%.

[0040] In summary, the method for preparing the near-infrared second-zone photothermal agent based on dendritic silver particles of the present invention does not require the use of a substrate, is easy to operate, has a good control effect, and the obtained particles have high photothermal conversion efficiency and good photothermal stability, and are highly valuable for promotion and application.

Claims

1. A method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles, characterized in that: At room temperature and under continuous stirring, the sodium hydroxide solution is quickly added to the silver nitrate solution and mixed evenly to adjust the pH of the solution to alkaline. After a certain interval, the reducing agent hydroxylamine solution is added. After a certain reaction time, the stabilizer polyvinyl pyrrolidone solution is added thereto. The mixture is stirred for 30 seconds and then centrifuged and purified.

2. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the stirring speed is preferably 1000 rpm.

3. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the final concentration of the silver nitrate solution is 0.25 mM.

4. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the pH of the solution is adjusted in the range of 10.2 to 11.

9.

5. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the final concentration of hydroxylamine is 0.5 mM.

6. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the interval time is preferably 10 seconds.

7. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the reaction time is preferably 30 seconds.

8. The method for preparing a near-infrared second-zone photothermal agent based on dendritic silver particles according to claim 1, characterized in that: In the reaction system, the final mass fraction of the polyvinyl pyrrolidone is 0.5%.

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