Preparation method of gold nanoparticles based on plant extract and application thereof

Abstract

The application belongs to the technical field of gold nanoparticles, and particularly relates to a preparation method of gold nanoparticles based on plant extracts and application thereof; and comprises the following steps: preparing a purslane extract solution; preparing a chloroauric acid solution; mixing the purslane extract solution and the chloroauric acid solution according to a volume ratio of 1:2-9, stirring and reacting under normal temperature and pressure, and obtaining a gold nanoparticle suspension when the solution color changes from brown yellow to purple; the gold nanoparticles synthesized by the purslane mediation are about 20 nanometers, have more complex molecules with group attachment, and have shapes of pentagon, hexagon, sphere and rod, etc. pH and Fourier infrared detection show that oxalic acid, phenols and ketones in the plant extracts participate in the formation and stability of the gold nanoparticles. The participation of the plant source highlights and strengthens the antioxidant performance of the gold nanoparticles in the synthesis process of the gold nanoparticles under the conditions of reduced cost and energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of gold nanoparticle technology, specifically a method for preparing gold nanoparticles based on plant extracts and their application. Background Technology

[0002] Gold nanotechnology, as a typical nanobiomaterial, more clearly demonstrates the advantages and disadvantages of nanotechnology. Gold (Au) is considered inert in its macroscopic state, but its physicochemical properties change dramatically when its size is reduced to the nanoscale. Gold nanoparticles (AuNPs) are hailed as the "Swiss Army knife" of nanotechnology due to their unique surface plasmon resonance properties, ease of functionalization, and excellent biocompatibility. Over the past five years, their application in biomedicine, optoelectronics, and catalysis has deepened. Surface plasmon resonance causes them to exhibit peaks in the 520nm-800nm ​​ultraviolet-visible absorption spectrum, displaying visible colors such as red, purple, and blue. Regarding modifiability, the surface of gold nanoparticles readily forms Au-S / Au-N bonds with -SH and -NH2, allowing them to load antibodies, DNA, peptides, hyaluronic acid, etc. Therefore, gold nanoparticles are often used as drug or gene carriers for targeted therapy. They can also specifically bind to certain target DNA chains to form hybridization bands, leading to gold nanoparticle aggregation and visible color changes. Furthermore, the unique surface plasmon resonance (LSPR) effect of gold nanoparticles significantly increases the proportion of surface atoms, leading to changes in their electronic structure and surface energy, and endowing them with catalytic properties that traditional bulk metals do not possess.

[0003] Meanwhile, the disadvantages of general nanomaterials are even more pronounced in gold nanoparticles. The plasmon resonance properties of gold nanoparticles, besides providing high catalytic and antioxidant properties, also allow them to penetrate cells, easily inducing oxidative stress and mitochondrial damage. The European Union Scientific Committee on Consumer Safety (SCCS) points out that 2-5 nm cationic gold nanoparticles can significantly reduce mitochondrial membrane potential and increase intracellular (reactive oxygen species) ROS, leading to DNA breaks, cell cycle arrest, and inflammation in liver and kidney tissues. Furthermore, particles smaller than 10 nm can penetrate the nuclear membrane, accumulate in the cell nucleus, and produce genotoxicity, with the toxicity increasing with decreasing size. In vivo clearance is slow; 13 nm PEGylated gold particles, after intravenous injection, mainly accumulate in the liver with a half-life of up to 120 hours, which can induce acute neutrophil infiltration and altered enzyme activity. The long-term accumulation risk poses a barrier to clinical translation.

[0004] In addition, the preparation and surface modification of gold nanoparticles are costly and environmentally harmful. In order to obtain a particle size distribution within ±5%, a two-step "seed growth" method is usually adopted: first, 3-5 nm seeds are prepared, and then the seeds are reduced and grown in a second time. Each step is accompanied by centrifugation and ultrafiltration purification, and the loss of gold elemental is about 10% to 20%, which directly increases the effective cost by more than 20%.

[0005] Traditional chemical methods generate gold-ion-containing waste liquid, organic solvents, and sodium borohydride residue, requiring precious metal recovery and hazardous waste treatment; while traditional physical methods such as laser ablation, sputtering, and arc evaporation, which are "top-down" processes, must be carried out under high vacuum or inert atmospheres, with power densities greater than 10⁶ W / cm². -2 The electricity cost for a single batch can reach several hundred US dollars, the material utilization rate is less than 40%, the gold loss is large, and the dust-containing exhaust gas generated by the physical method must be equipped with HEPA filters. + Activated carbon is used for end-of-pipe treatment. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by this invention to solve its technical problem is: a method for preparing gold nanoparticles based on plant extracts, comprising the following steps: Step S1: Prepare purslane extract; Step S2: Prepare chloroauric acid solution; Step S3: Mix the purslane extract and the chloroauric acid solution at a volume ratio of 1:2-9, and stir the mixture at room temperature and pressure. When the solution color changes from brownish-yellow to purple, a gold nanoparticle suspension is obtained.

[0008] Preferably, step S1 specifically includes: The dried purslane powder was added to water and heated to 80°C to obtain the original purslane extract. After cooling the original solution, centrifuge it, take the supernatant and filter it at least three times, collect the filtrate, and obtain purslane extract.

[0009] Preferably, the ratio of purslane powder to water is 5g:250mL.

[0010] Preferably, the centrifugation speed is 4000 r / min and the centrifugation time is 20 minutes.

[0011] Preferably, step S2 specifically includes: Weigh 4.12 g of chloroauric acid tetrahydrate granules, dissolve them in deionized water, and dilute to 100 mL in a volumetric flask. Shake well to obtain a chloroauric acid solution.

[0012] Preferably, in step S3, the total volume of the purslane extract and the chloroauric acid solution is 30 mL.

[0013] Preferably, in step S3, the stirring reaction time is 2 hours.

[0014] Preferably, in step S3, the reaction is carried out under normal temperature and pressure conditions.

[0015] Preferably, in step S3, the volume ratio of the solute in the purslane extract to the chloroauric acid solution is 1:2-9.

[0016] Application of gold nanoparticles prepared by the above method in the preparation of antioxidants.

[0017] The beneficial effects of this invention are as follows: This invention aims to reduce costs, decrease toxicity, improve biocompatibility and green chemistry by improving plant-derived gold nanoparticles, showcasing optimized solutions for nanotechnology, and providing a reference for research on plant-derived gold nanoparticles.

[0018] Plant-derived gold nanoparticles have further enhanced their performance in biological and pharmaceutical applications. These nanoparticles, derived from water extracts of flowers, leaves, fruits, and stems that act as both reducing agents and stabilizers, possess a unique "plant coating." Polyphenols, alkaloids, and saponins, for example, bind to the gold core via Au–S / Au–O bonds, forming an organic shell of approximately 2 nm. This coating prevents aggregation, provides additional bioactivity, enhances antioxidant capacity, and strengthens biocompatibility. Furthermore, different plant species, extracts, pH levels, and temperatures can all potentially yield gold nanoparticles of varying sizes, shapes, and bioactivities. The plant sources for the biosynthesis of gold nanoparticles are diverse; green plants such as tamarind, aloe vera, camphor trees, and white willow can all be used for the green synthesis of gold nanoparticles.

[0019] Under the influence of plant extracts, the formation of gold nanoparticles mainly involves three processes, namely, Au in chloroauric acid. 3+ Ions are reduced by reducing substances in plant extracts; gold nanoparticles grow under the influence of functional groups (such as polyols and carboxylic acids) in plant extracts; secondary metabolites (such as secondary alcohols) of plant extracts stabilize the newly formed gold nanoparticles. Compared with traditional physical methods and sodium citrate-sodium borohydride methods, the biosynthesis method not only endows gold nanoparticles with different properties, but also has a mild and green reaction process with no precious metal waste liquid at room temperature and pressure, and lower cost.

[0020] The gold nanoparticles synthesized in this invention via purslane-mediated synthesis are approximately 20 nanometers in size and contain numerous complex molecules with aggregated structures, exhibiting shapes such as pentagons, hexagons, spheres, and rods. pH and Fourier transform infrared spectroscopy (FTIR) analysis revealed that oxalic acid, phenols, and ketones from the plant extract participated in the formation and stabilization of the gold nanoparticles. The involvement of plant sources allows the synthesis process of the gold nanoparticles to highlight and enhance their antioxidant properties while reducing costs and energy consumption. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 This is a color change diagram during the synthesis of plant-derived gold nanoparticles; Figure 2 These are graphs showing pH changes during the synthesis of three groups of plant-derived gold nanoparticles. Figure 3 These are the UV-Vis absorption spectra of three groups of plant-derived gold nanoparticle solutions and purslane extract; Figure 4 These are the Fourier transform infrared spectra of three groups of plant-derived gold nanoparticle solutions and purslane extract; Figure 5 This is a structural diagram of biomolecular groups attached to gold nanoparticles at 100 nm. Figure 6 This is a diagram showing the dispersed arrangement of multiple nano-gold composite groups; Figure 7 This is a comparison of the antioxidant effects of three groups of plant-derived gold nanoparticles and gold nanoparticles produced by traditional chemical methods; Figure 8 This is a comparison of the antioxidant effects of three groups of plant-derived nano-gold. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0024] Example 1 The method for preparing gold nanoparticles based on plant extracts according to an embodiment of the present invention includes the following steps: S1. Preparation of Portulaca oleracea extract Fresh purslane was washed to remove dirt and sand, then placed in an oven at 35°C for 24 hours. The dried purslane was then ground and sieved to obtain purslane powder. 5g of the powder was added to a 250mL round-bottom flask, along with 100mL of water, and heated to 80°C to obtain the purslane extract stock solution. After cooling, the solution was transferred to centrifuge tubes. The stock solution was centrifuged at 4000 rpm for 20 minutes, and the supernatant was filtered at least three times. The filtrate was collected to obtain the purslane extract. The extract was stored at 5°C in a refrigerator.

[0025] Preparation of S2 chloroauric acid solution Weigh 4.12 g of chloroauric acid tetrahydrate granules, dissolve them in deionized water, and dilute to 100 mL in a volumetric flask. Shake well. Store the prepared chloroauric acid in a brown glass bottle and wrap it with aluminum foil.

[0026] S3, reduction of chloroauric acid solution The prepared purslane extract and chloroauric acid aqueous solution were placed in an Erlenmeyer flask at a volume ratio of 1:2, ensuring a total volume of 30 mL. A magnetic stir bar was added, and the mixture was stirred at room temperature and pressure for 2 hours. When the solution was observed to slowly change from brownish-yellow to purple, it indicated that the gold nanoparticles had been generated. The solution was collected and stored in a refrigerator at 5°C.

[0027] Example 2 The method for preparing gold nanoparticles based on plant extracts according to an embodiment of the present invention includes the following steps: S1. Preparation of Portulaca oleracea extract Fresh purslane was washed to remove dirt and sand, then placed in an oven at 35°C for 24 hours. The dried purslane was then ground and sieved to obtain purslane powder. 5g of the powder was added to a 250mL round-bottom flask, along with 100mL of water, and heated to 80°C to obtain the purslane extract stock solution. After cooling, the solution was transferred to centrifuge tubes. The stock solution was centrifuged at 4000 rpm for 20 minutes, and the supernatant was filtered at least three times. The filtrate was collected to obtain the purslane extract. The extract was stored at 5°C in a refrigerator.

[0028] Preparation of S2 chloroauric acid solution Weigh 4.12 g of chloroauric acid tetrahydrate granules, dissolve them in deionized water, and dilute to 100 mL in a volumetric flask. Shake well. Store the prepared chloroauric acid in a brown glass bottle and wrap it with aluminum foil.

[0029] S3, reduction of chloroauric acid solution The prepared purslane extract and chloroauric acid aqueous solution were placed in an Erlenmeyer flask at a volume ratio of 1:4, ensuring a total volume of 30 mL. A magnetic stir bar was added, and the mixture was stirred at room temperature and pressure for 2 hours. When the solution was observed to slowly change from brownish-yellow to purple, it indicated that the gold nanoparticles had been generated. The solution was collected and stored in a refrigerator at 5°C.

[0030] Example 3 The method for preparing gold nanoparticles based on plant extracts according to an embodiment of the present invention includes the following steps: S1. Preparation of Portulaca oleracea extract Fresh purslane was washed to remove dirt and sand, then placed in an oven at 35°C for 24 hours. The dried purslane was then ground and sieved to obtain purslane powder. 5g of the powder was added to a 250mL round-bottom flask, along with 100mL of water, and heated to 80°C to obtain the purslane extract stock solution. After cooling, the solution was transferred to centrifuge tubes. The stock solution was centrifuged at 4000 rpm for 20 minutes, and the supernatant was filtered at least three times. The filtrate was collected to obtain the purslane extract. The extract was stored at 5°C in a refrigerator.

[0031] Preparation of S2 chloroauric acid solution Weigh 4.12 g of chloroauric acid tetrahydrate granules, dissolve them in deionized water, and dilute to 100 mL in a volumetric flask. Shake well. Store the prepared chloroauric acid in a brown glass bottle and wrap it with aluminum foil.

[0032] S3, reduction of chloroauric acid solution The prepared purslane extract and chloroauric acid aqueous solution were placed in an Erlenmeyer flask at a volume ratio of 1:9, ensuring a total volume of 30 mL. A magnetic stir bar was added, and the mixture was stirred at room temperature and pressure for 2 hours. When the solution was observed to slowly change from brownish-yellow to purple, it indicated that the gold nanoparticles had been generated. The solution was collected and stored in a refrigerator at 5°C.

[0033] To facilitate the subsequent summary of experimental results, the plant-derived gold nanoparticles generated in Examples 1-3 are referred to as Group a, Group b, and Group c, respectively.

[0034] like Figure 1 As shown, the reactant mixture solution is dark yellow. During the synthesis experiment, the solution color gradually turns brown, then begins to change towards purple. When it becomes light purple, it indicates that the color of the gold nanoparticles is deepening. As the reaction time increases, the purple color of the solution becomes increasingly deeper, indicating that more and more gold nanoparticles are generated and the concentration is increasing. The color change observed throughout the experiment is presumably due to the formation of gold nanoparticles and plasmon resonance on their surface.

[0035] Furthermore, the color of gold nanoparticles synthesized in different proportions changes, except for the depth of color. Due to the plasmon resonance effect on the surface of the gold nanoparticles, the more reddish the color, the more dispersed the gold nanoparticles are, while the more blue the color, the more aggregated the gold nanoparticles are.

[0036] like Figure 2 As shown, the pH of the gold nanoparticle synthesis reaction in Examples 1-3 was monitored by dynamically measuring the pH of the extract and the product, i.e., the gold nanoparticle suspension, using a pH meter.

[0037] With changes in the feed ratio, the initial, process, and termination pH of the plant-derived gold nanoparticle solution formation are different, the pH change trends and curves are different, and the time for complete reaction is also different.

[0038] Because the feed ratio was changed during the preparation of plant-derived gold nanoparticles while ensuring the total volume remained the same, changing the feed ratio essentially altered the relative concentrations of the two materials.

[0039] Characterization of plant-derived gold nanoparticles UV-Vis absorption spectrum After sonicating the three nano-gold solutions for 10 minutes, 1 ml of each solution was placed in a quartz cuvette with a 1 cm optical path. The ultraviolet spectrophotometer was used to measure the ultraviolet spectra at 200 to 800 nm, and the absorption peaks of the nano-gold particles were scanned.

[0040] like Figure 3 As shown, to eliminate the influence of possible functional groups contained in purslane itself on ultraviolet light in the nano-gold solution, a control group was used. It was found that no peak was observed in the range of 500 to 600 nanometers. Therefore, it can be confirmed that the peak in the range of 500 to 600 nanometers is the result of the formation of nano-gold particles.

[0041] A peak appears between 500 and 600 nanometers. This peak shape is caused by plasmon resonance on the surface of the gold nanoparticles, which indicates that gold nanoparticles have been generated.

[0042] Fourier transform infrared spectroscopy Fourier transform infrared spectroscopy is helpful in characterizing the surface groups of gold nanoparticles. This experiment aims to investigate which groups participate in the reduction reaction process during the synthesis of plant-derived gold nanoparticles, and to study the formation process of groups or sites to infer the characteristics of gold nanoparticles synthesized by this method. Infrared spectroscopy was used to measure the characteristic absorption of the extract and solid gold nanoparticles.

[0043] like Figure 4 As shown, the present invention uses infrared spectroscopy to measure the extract and gold nanoparticles, and compares the two to infer the changes in functional groups during the reaction process.

[0044] Transmission electron microscope The morphology and size of gold nanoparticles can be further studied using TEM (Electron Microscopy). After ultrasonic separation, the samples were photographed at different scales using an experimental voltage of 5,000 volts.

[0045] like Figure 5 and Figure 6 As shown in the TEM image, the average size of the gold nanoparticles observed is approximately 20 nm. Furthermore, various shapes of gold nanoparticles, such as cubes, cylinders, and other polyhedral shapes, were observed attached to large functional groups.

[0046] Meanwhile, some gold nanoparticles also exhibited irregular shapes with attached substances, such as Figure 8 It is speculated that this is one of the reasons why the gold nanoparticle solution remains stable. In the process of reducing chloroauric acid to generate gold nanoparticles, the extract may provide some of its own biomacromolecule groups as attachment sites for the gold nanoparticles, thereby achieving the dispersion and stability of the gold nanoparticles, replacing the traditional method of achieving dispersion and stability through physical means such as high temperature or discharge.

[0047] Performance testing Antioxidant properties of purslane plant-derived gold nanoparticles determined Preparation of DPPH solution Weigh 0.02 g of DPPH solid, dissolve it in anhydrous ethanol solution, and dilute to a final volume of 250 mL in a volumetric flask. Shake well. Transfer to a brown bottle and store in a refrigerator at 5°C, protected from light.

[0048] Preparation of sample solution Three different gold nanoparticle solutions were prepared by mixing 2 mL, 1.5 mL, 1 mL, 0.5 mL, and 0.2 mL of deionized water to form solutions with a volume of 2 mL and concentrations of 100%, 75%, 50%, 25%, and 10%, respectively, for testing.

[0049] 2 mL, 1.5 mL, 1 mL, 0.5 mL, and 0.2 mL of ordinary gold nanoparticle solution were respectively mixed with deionized water to prepare solutions with a volume of 2 mL and concentrations of 100%, 75%, 50%, 25%, and 10%, respectively, for testing.

[0050] Free radical scavenging experiment Add the DPPH solution and the sample solution to the test tube in a 1:1 ratio and shake well to allow them to react fully. After about 30 minutes, observe that part of the solution turns brownish-yellow and the brownish-yellow part no longer diffuses. Then centrifuge it at 8000 r / min for 20 minutes and measure its absorbance at 520 nm.

[0051] Calculation of DPPH free radical scavenging rate DPPH free radical scavenging rate (%) = 1 (Ao) Ap) / Aq) * 100% Where Ao is the absorbance after the sample solution and DPPH solution react, Ap is the absorbance after the sample solution and deionized water are mixed, and Aq is the absorbance after the DPPH solution and deionized water are mixed.

[0052] like Figure 7As shown, overall, the first two types of plant-derived gold nanoparticle solutions with different degrees of dispersion significantly improved the antioxidant properties of gold nanoparticles compared to those produced by traditional chemical methods, while group C only showed a slight improvement at low concentrations.

[0053] Among the three groups, group a showed a significant advantage in antioxidant performance at low concentrations, and exhibited the largest difference in free radical scavenging rate against nano-gold prepared by traditional chemical methods. Group b, on the other hand, showed a relatively smaller advantage in antioxidant performance, which, combined with the UV spectroscopy results mentioned earlier, is likely due to its lower concentration.

[0054] The UV spectrum of group C shows that its concentration of plant-derived gold nanoparticles is the same as that of group B, but its advantage in antioxidant experiments is far less than that of the first two groups, and its antioxidant performance at high sample concentrations is not as good as that of traditional methods.

[0055] like Figure 8 As shown, after demonstrating the advantages of plant-derived nano-gold in antioxidant properties, this invention removes the control group of traditional nano-gold and directly compares the three groups (a, b, and c) to analyze the effect of the feeding ratio on the antioxidant properties of plant-derived nano-gold.

[0056] The comparison revealed that the antioxidant advantage of group a was more obvious at low sample concentrations, while the difference between groups b and c was not significant at low concentrations. It was only at high concentrations that the difference between the two groups widened, and the advantage of group a gradually decreased at high concentrations.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing gold nanoparticles based on plant extracts, characterized in that: Includes the following steps: Step S1: Prepare purslane extract; Step S2: Prepare chloroauric acid solution; Step S3: Mix the purslane extract and the chloroauric acid solution at a volume ratio of 1:2-9, and stir the mixture at room temperature and pressure. When the solution color changes from brownish-yellow to purple, a gold nanoparticle suspension is obtained.

2. The method for preparing gold nanoparticles based on plant extracts according to claim 1, characterized in that: Step S1 specifically includes: The dried purslane powder was added to water and heated to 80°C to obtain the original purslane extract. After cooling the original solution, centrifuge it, take the supernatant and filter it at least three times, collect the filtrate, and obtain purslane extract.

3. The method for preparing gold nanoparticles based on plant extracts according to claim 2, characterized in that: The ratio of purslane powder to water is 5g:250mL.

4. The method for preparing gold nanoparticles based on plant extracts according to claim 2, characterized in that: The centrifuge speed was 4000 r / min and the centrifugation time was 20 minutes.

5. The method for preparing gold nanoparticles based on plant extracts according to claim 4, characterized in that: Step S2 specifically includes: Weigh 4.12 g of chloroauric acid tetrahydrate granules, dissolve them in deionized water, and dilute to 100 mL in a volumetric flask. Shake well to obtain a chloroauric acid solution.

6. The method for preparing gold nanoparticles based on plant extracts according to claim 5, characterized in that: In step S3, the total volume of the purslane extract and the chloroauric acid solution is 30 mL.

7. The method for preparing gold nanoparticles based on plant extracts according to claim 6, characterized in that: In step S3, the stirring reaction takes 2 hours.

8. The method for preparing gold nanoparticles based on plant extracts according to claim 7, characterized in that: In step S3, the reaction is carried out under normal temperature and pressure conditions.

9. The method for preparing gold nanoparticles based on plant extracts according to claim 8, characterized in that: In step S3, the volume ratio of the solute in the purslane extract to the chloroauric acid solution is 1:2-9.

10. The application of gold nanoparticles prepared by the preparation method according to any one of claims 1-9 in the preparation of antioxidants.

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