Preparation method of honey-mediated silver nanoparticle / attapulgite composite antibacterial material

Abstract

The application discloses a preparation method of honey-mediated silver nanoparticle / attapulgite composite antibacterial material, which comprises the following steps: dissolving natural honey in water to form a honey aqueous solution under stirring, dispersing attapulgite powder into the honey aqueous solution to obtain a uniform mixed solution, adding silver nitrate aqueous solution dropwise into the mixed solution, adjusting the pH of the mixed solution to 8-9, and continuously stirring the mixed solution at room temperature for 3-6 hours; and centrifuging, washing and drying the obtained product to obtain the silver nanoparticle / attapulgite composite antibacterial material. The active components in the honey are used as a reducing agent and a stabilizer, the silver nanoparticle / attapulgite composite antibacterial material is synthesized by one-step method, the preparation process is green, simple and efficient; the natural attapulgite is used as a carrier, on the one hand, the generation process of the silver nanoparticles is regulated, and the technical problem of effectively reducing the agglomeration of the silver nanoparticles is solved; and on the other hand, the biological activity is synergistically enhanced, so that the silver nanoparticles can play a more efficient antibacterial role and the application safety is improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a honey-mediated silver nanoparticle / attapulgite composite antibacterial material, which can be applied to the fields of polymer materials, membrane materials, functional coatings and medical wound dressings, and belongs to the fields of clay mineral functional materials and composite material technology. Background Technology

[0002] Silver nanoparticles are the most common type of metal nanoparticles with broad-spectrum antibacterial properties. They can inhibit bacterial cell membrane structure, induce leakage of intracellular contents, bind to the sulfhydryl groups of enzymes to inactivate proteins, and inhibit DNA replication and Ag release. + Effective methods such as [list of methods] can inhibit microbial growth (Sustainable Materials and Technologies, 2017, 13: 18-23). ​​Currently, many methods exist for synthesizing silver nanoparticles. Physical methods (such as metal salt pyrolysis and laser ablation) offer advantages such as simplicity, no need for other solvents, and uniform nanoparticle synthesis; however, the calcination process consumes a large amount of energy. While chemical reduction is the most common method for synthesizing metal nanoparticles, it requires the introduction of toxic reducing agents or stabilizers (to stabilize the size of the prepared nanoparticles and prevent aggregation) or the generation of environmentally unfriendly byproducts. In recent years, green synthesis has received widespread attention. To date, there are few reports on research involving the reduction of metal nanoparticles from animal products or animal extracts.

[0003] Honey is a viscous liquid, mostly amber in color, composed of approximately 85% carbohydrates (mainly fructose and glucose), 15-17% water, 0.1-0.4% protein, and small amounts of amino acids, vitamins, minerals, and antioxidant molecules (phenolic compounds, such as flavonoids and phenolic acids) (Journal of Nanomaterials, 2017, 2017:5919836). Honey is not only used as a functional food but also holds significant research value in medicine, pharmacy, and chemistry due to its antioxidant, anti-diabetic, and anti-cancer bioactive compounds. However, few have noticed that honey's unique chemical properties also make it suitable for the green synthesis of metal nanoparticles, as its carbohydrates can act as reducing agents and proteins as stabilizers. Compared to plants or plant extracts, honey-mediated biosynthesis is simpler and more efficient, as the former often requires additional drying or extraction processes.

[0004] In recent years, to avoid the aggregation problem of synthesized nanoparticles, carrier-based composite antibacterial materials have seen significant development. Attapulgite, a hydrous magnesium-aluminate silicate clay mineral with a layered chain structure, possesses a unique one-dimensional nanorod-like crystal structure, making it an ideal nanoparticle carrier material (Attapulgite: Novel Functional Materials and Applications, Beijing: Science Press, December 2021). Attapulgite's unique structure endows it with excellent adsorption, colloidal, carrier, and reinforcing properties, and it has been widely used in many fields, including adsorbents, cosmetics, antibacterial agents, and polymer fillers (Science in China: Chemistry, 2018, 48: 1432-1451). However, there are no reports on the preparation of composite antibacterial materials by loading silver nanoparticles onto attapulgite using a honey-mediated method. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a honey-mediated silver nanoparticle / attapulgite composite antibacterial material.

[0006] I. Preparation of Nanoparticle / Attapulgite Composite Antibacterial Materials

[0007] The present invention provides a method for preparing honey-mediated silver nanoparticle / attapulgite composite antibacterial material. The method involves dissolving natural honey in water under stirring to form a honey-water solution, then dispersing attapulgite powder into the honey-water solution to obtain a uniform mixture. Next, silver nitrate aqueous solution is added dropwise to the mixture, and the pH of the mixture is adjusted to 8-9. The mixture is stirred continuously at room temperature for 3-6 hours. The resulting product is centrifuged, washed, and dried to obtain the silver nanoparticle / attapulgite composite antibacterial material.

[0008] The honey aqueous solution has a mass percentage of 10% to 25%; the attapulgite in the honey aqueous solution has a mass percentage of 0.5% to 10%.

[0009] The concentration of the silver nitrate aqueous solution is 1.5~5 g / L, and its dropping rate is controlled at 2~5 mL / min. The amount of silver nitrate added is 0.5%~15% of the mass of attapulgite.

[0010] The synthesis mechanism of this invention is as follows: Honey contains fructose, glucose, amino acids, vitamins, minerals, flavonoids, and phenolic acids, which can reduce silver ions to elemental silver. Among these substances, flavonoids and amino acid molecules can stabilize silver nanoparticles. First, attapulgite adsorbs silver ions through ion exchange and electrostatic interactions. Then, silver nanoparticles are generated in situ on the surface of attapulgite through reduction by honey.

[0011] Figure 1The color changes and product color comparison of the honey-mediated attapulgite-supported silver nanoparticle system before and after the reaction were investigated. It can be seen that before the reaction, the system solution was light gray. With increasing attapulgite content, the light gray color of the system deepened. After 3 hours of reaction, the system color significantly deepened, turning dark brown.

[0012] Figure 2 TEM images of honey-mediated silver nanoparticle loading in Examples 1-5 are shown. It can be seen that attapulgite exhibits a typical and smooth rod-like morphology, mainly attributed to the continuous extension of sandwich-type structural units composed of SiO4 tetrahedra and MO6 octahedra along a single direction. More importantly, monodisperse silver nanoparticles can be clearly observed on the surface of the attapulgite rods. This is partly due to the reducing effect of honey, and partly indicates that using attapulgite as a carrier can effectively reduce the aggregation of silver nanoparticles, primarily because the silanol groups on the surface of the attapulgite rods can serve as nucleation sites for silver nanoparticles. With increasing attapulgite content, the uniformity of the silver nanoparticles improves, achieving uniform deposition of silver nanoparticles.

[0013] Figure 3 The image shows the EDS elemental mapping of the composite antibacterial material prepared in Example 1, which further confirms the presence of silver and the uniform distribution of silver nanoparticles in the composite material.

[0014] II. Antibacterial Performance Testing of Nanoparticle / Attapulgite Composite Antibacterial Materials

[0015] The antibacterial properties of the composite material were evaluated by determining the minimum inhibitory concentration (MIC) using the agar dilution method. First, sterilized test samples were uniformly dispersed into agar medium at 40–50°C according to different concentrations, and after cooling, sample plates were obtained. Then, logarithmic-phase bacteria were used to prepare 10... 4 CFU·mL -1 The bacterial suspension was inoculated at three different locations on an agar plate (1-2 µL). A positive control was prepared by inoculating the bacterial suspension on an agar plate without the sample, and a negative control was prepared by inoculating an agar plate without either the antibacterial sample or the bacterial suspension. The inoculated plates were then placed in a 37°C incubator and incubated for 18-24 hours. The minimum sample concentration at which bacterial growth was completely inhibited in the agar plate was defined as the MIC value.

[0016] Figure 4 and Figure 5Digital photographs of *Escherichia coli* and *Staphylococcus aureus* after treatment with honey-mediated attapulgite-supported silver nanoparticles in Examples 1-5, respectively. Compared with the positive control group that formed obvious bacterial colonies, honey-mediated attapulgite-supported silver nanoparticles exhibited superior antibacterial activity against both Gram-negative and Gram-positive bacteria. The excellent antibacterial properties of this composite material are attributed, on the one hand, to the physical damage to the bacterial cell membrane caused by the rod-like structure of the attapulgite, and on the other hand, to the disruption of the bacterial cell membrane structure by the silver nanoparticles, as well as the induction of intracellular solute leakage, binding to the sulfhydryl groups of enzymes leading to protein inactivation, and inhibition of DNA replication and Ag release. + And so on. As the amount of attapulgite added increases, the inhibitory effect of the nanocomposite material on the growth of Gram-negative bacteria (Escherichia coli) weakens accordingly, which not only successfully proves the successful synthesis of silver nanoparticles in this invention, but also shows that the antibacterial effect of silver nanoparticles dominates in the composite material.

[0017] In summary, this invention utilizes the active ingredients in honey as reducing agents and stabilizers to synthesize a one-step silver nanoparticle / attapulgite composite antibacterial material. The preparation process is green, simple, and efficient. Using natural attapulgite as a carrier, the generation process of silver nanoparticles is regulated, effectively reducing the technical challenge of silver nanoparticle aggregation. Furthermore, it synergistically enhances biological activity, enabling the silver nanoparticles to exert a more efficient antibacterial effect and improving their application safety. Experiments also show that the silver nanoparticle / attapulgite composite antibacterial material synthesized in this invention exhibits excellent antibacterial activity against bacteria, making it an ideal antibacterial functional additive that can be used as an antibacterial functional filler in fields such as polymer materials, membrane materials, functional coatings, and medical wound dressings. Attached Figure Description

[0018] Figure 1 This invention presents a comparison of color changes and product color before and after the reaction of the honey-mediated attapulgite-supported silver nanoparticle system.

[0019] Figure 2 These are TEM images of honey-mediated attapulgite-supported silver nanoparticles obtained in Examples 1-5 of this invention. (a) Example 1, (b) Example 2, (c) Example 3, (d) Example 4, (e) Example 5.

[0020] Figure 3 This is an EDS elemental mapping diagram of honey-mediated attapulgite-supported silver nanoparticles obtained in Example 1 of the present invention.

[0021] Figure 4 These are digital photographs of honey-mediated attapulgite-supported silver nanoparticles and Escherichia coli after treatment with Escherichia coli, obtained in Examples 1-5 of this invention.

[0022] Figure 5Digital photographs of honey-mediated attapulgite-supported silver nanoparticles and Staphylococcus aureus after treatment with Staphylococcus aureus, obtained in Examples 1-5. Detailed Implementation

[0023] The following specific embodiments further illustrate the preparation method and antibacterial properties of the honey-mediated silver nanoparticle / attapulgite composite antibacterial material of the present invention.

[0024] Example 1

[0025] Measure 15 mL of a 5% (w / w) honey aqueous solution, then add attapulgite (0.5% (w / w) to the solution and mechanically stir (200 rpm) until homogeneous. Next, add 20 mL of a 1.5 g / L silver nitrate aqueous solution dropwise to the mixture at a rate of 3 mL / min. Adjust the pH of the mixture to 8.5 with a 1 mol / L NaOH aqueous solution. Continue stirring at room temperature for 4 hours. Centrifuge, wash, and dry to obtain the attapulgite-supported silver nanoparticle antibacterial material. The elemental content of this antibacterial material is shown in Table 1. Its MIC values ​​against *Escherichia coli* and *Staphylococcus aureus* are 1 mg / mL and 0.25 mg / mL, respectively, showing the strongest inhibitory effect on the tested bacteria compared to other examples.

[0026] Example 2

[0027] Measure 15 mL of a 5% (w / w) honey aqueous solution, then add attapulgite (1.0% (w / w) to the solution and mechanically stir (200 rpm) until homogeneous. Next, add 20 mL of a 1.5 g / L silver nitrate aqueous solution dropwise to the mixture at a rate of 3 mL / min. Adjust the pH of the mixture to 8.5 with a 1 mol / L NaOH aqueous solution. Continue stirring at room temperature for 4 hours. After centrifugation, washing, and drying, the attapulgite-supported silver nanoparticle antibacterial material is obtained. The elemental content of this antibacterial material is shown in Table 1. Its MIC values ​​against Escherichia coli and Staphylococcus aureus are 2.5 mg / mL and 0.25 mg / mL, respectively.

[0028] Example 3

[0029] Measure 15 mL of a 5% (w / w) honey aqueous solution, then add attapulgite (2.0% (w / w) to the solution, and mechanically stir (200 rpm) until homogeneous. Next, add 20 mL of a 1.5 g / L silver nitrate aqueous solution dropwise to the mixture at a rate of 3 mL / min. Adjust the pH of the mixture to 8.5 with a 1 mol / L NaOH aqueous solution. Continue stirring at room temperature for 4 hours. After centrifugation, washing, and drying, the attapulgite-supported silver nanoparticle antibacterial material is obtained. The elemental content of this antibacterial material is shown in Table 1. Its MIC values ​​against Escherichia coli and Staphylococcus aureus are 5 mg / mL and 0.25 mg / mL, respectively.

[0030] Example 4

[0031] Measure 15 mL of a 5% (w / w) honey aqueous solution, then add attapulgite (5.0% (w / w) to the solution and mechanically stir (200 rpm) until homogeneous. Next, add 20 mL of a 1.5 g / L silver nitrate aqueous solution dropwise to the mixture at a rate of 3 mL / min. Adjust the pH of the mixture to 8.5 with a 1 mol / L NaOH aqueous solution. Continue stirring at room temperature for 4 hours. After centrifugation, washing, and drying, the attapulgite-supported silver nanoparticle antibacterial material is obtained. The elemental content of this antibacterial material is shown in Table 1. Its MIC value against Escherichia coli exceeds 5 mg / mL, and its MIC value against Staphylococcus aureus is 0.25 mg / mL.

[0032] Example 5

[0033] Measure 15 mL of a 5% (w / w) honey aqueous solution, then add 10.0% attapulgite (10.0% (w / w) to the solution. Stir mechanically (200 rpm) until homogeneous. Next, add 20 mL of a 1.5 g / L silver nitrate aqueous solution dropwise to the mixture at a rate of 3 mL / min. Adjust the pH of the mixture to 8.5 with a 1 mol / L NaOH aqueous solution. Continue stirring for 4 hours. Centrifuge, wash, and dry to obtain the attapulgite-supported silver nanoparticle antibacterial material. The elemental content of this antibacterial material is shown in Table 1. Its MIC value against Escherichia coli exceeds 5 mg / mL, and its MIC value against Staphylococcus aureus is 0.25 mg / mL.

[0034]

Claims

1. A method for preparing a honey-mediated silver nanoparticle / attapulgite composite antibacterial material, characterized in that: Natural honey was dissolved in water under stirring to form a honey-water solution. Attapulgite powder was then dispersed into the honey-water solution to obtain a uniform mixture. Silver nitrate solution was then added dropwise to the mixture, and the pH of the mixture was adjusted to 8-9. The mixture was stirred continuously at room temperature for 3-6 hours. The resulting product was centrifuged, washed, and dried to obtain a silver nanoparticle / attapulgite composite antibacterial material. The mass percentage of the honey-water solution was 10%-25%. The mass percentage of attapulgite in the honey-water solution was 0.5%-10%. The amount of silver nitrate added was 0.5%-15% of the mass of attapulgite.

2. The preparation method of the honey-mediated silver nanoparticle / attapulgite composite antibacterial material according to claim 1, characterized in that: The concentration of the silver nitrate aqueous solution is 1.5~5 g / L, and its dropping rate is controlled at 2~5 mL / min.

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