阅读说明：本技术 一种手性半胱氨酸纳米自组装抗菌材料及其制备方法和应用 (Chiral cysteine nano self-assembly antibacterial material and preparation method and application thereof ) 是由 严文静 徐跃龙 张敏 章建浩 于 2021-01-15 设计创作，主要内容包括：本发明公开了一种手性半胱氨酸纳米自组装抗菌材料及其制备方法和应用,属于纳米材料技术领域。该方法以纳米金为核心,以少量巯基聚乙二醇为稳定剂,采用分次添加的方式将半胱氨酸通过Au-S键固定在纳米金表面,制备手性半胱氨酸纳米自组装抗菌材料。本发明方法能显著提高纳米金及单纯半胱氨酸的稳定性,并对大肠杆菌、金黄色葡萄球菌等致病菌表现出广谱抗菌性。(The invention discloses a chiral cysteine nano self-assembly antibacterial material and a preparation method and application thereof, belonging to the technical field of nano materials. The method takes nanogold as a core, takes a small amount of sulfhydryl polyethylene glycol as a stabilizer, and adopts a mode of adding cysteine by times to fix on the surface of the nanogold through Au-S bonds to prepare the chiral cysteine nano self-assembled antibacterial material. The method can obviously improve the stability of the nano-gold and the pure cysteine, and shows broad-spectrum antibacterial property to pathogenic bacteria such as escherichia coli, staphylococcus aureus and the like.)

1. A chiral cysteine nano self-assembly antibacterial material is characterized in that: the material is prepared by the following method:

(1) mixing water and a chloroauric acid solution, stirring and heating to boil, then adding a trisodium citrate solution, heating and stirring until the color of the solution is not changed, stopping heating, adding a sodium hydroxide solution, finally adding a cysteine solution, stirring and cooling to room temperature to obtain an Au/cys nanoparticle solution;

(2) adding a sulfhydryl polyethylene glycol solution into the Au/cys nanoparticle solution, stirring at room temperature, centrifuging to remove a supernatant, adding water for resuspension, and obtaining an Au/cys-PEG nanoparticle solution;

(3) adding cysteine solution into the Au/cys-PEG nano-particle solution, stirring at room temperature, centrifuging to remove supernatant, adding water for resuspension, and obtaining the Au/cys-PEG/cys nano-antibacterial solution.

2. The chiral cysteine nano self-assembled antibacterial material according to claim 1, characterized in that: the molar concentration of the chloroauric acid solution in the step (1) is 10-20 mmol/L; the mass fraction of the trisodium citrate is 0.1-2.0%; the molar concentration of the sodium hydroxide solution is 100-300 mmol/L; the molar concentration of the cysteine solution is 100-450 mmol/L; chloroauric acid solution: water: trisodium citrate solution: sodium hydroxide solution: the volume ratio of the cysteine solution is 1-2: 45-50: 0.5-10: 0.5-10: 0.5 to 10.

3. The chiral cysteine nano self-assembled antibacterial material according to claim 1, characterized in that: in the step (1), the particle size of the Au/cys nano-particles is 10-15 nm; the molar concentration of Au/cys in the Au/cys nanoparticle solution is 1-15 nmol/L.

4. The chiral cysteine nano self-assembled antibacterial material according to claim 1, characterized in that: the volume ratio of the Au/cys nanoparticle solution to the thiol-polyethylene glycol solution in the step (2) is 1 mL: (10-30) mu L; the average molecular weight of the sulfhydryl polyethylene glycol is 350-8000 kD, and the concentration of the sulfhydryl polyethylene glycol solution is 1-10 mM; the molar concentration of Au/cys-PEG in the Au/cys-PEG nanoparticle solution is 1-15 nmol/L.

5. The chiral cysteine nano self-assembled antibacterial material according to claim 1, characterized in that: in the step (3), the volume ratio of the Au/cys-PEG nanoparticle solution to the cysteine solution is 1 mL: (30-80) mu L; the molar concentration of the cysteine solution is 40-80 mmol/L; the molar concentration of Au/cys-PEG/cys in the Au/cys-PEG/cys nanoparticle solution is 1-15 nmol/L.

6. The chiral cysteine nano self-assembled antibacterial material according to claim 1, characterized in that: the cysteine in the step (1) and the step (3) is D-cysteine or L-cysteine.

7. A preparation method of a chiral cysteine nano self-assembly antibacterial material is characterized by comprising the following steps: the method comprises the following steps:

(1) mixing water and a chloroauric acid solution, stirring and heating to boil, then adding a trisodium citrate solution, heating and stirring until the color of the solution is not changed, stopping heating, adding a sodium hydroxide solution, finally adding a cysteine solution, stirring and cooling to room temperature to obtain an Au/cys nanoparticle solution;

(2) adding a sulfhydryl polyethylene glycol solution into the Au/cys nanoparticle solution, stirring at room temperature, centrifuging to remove a supernatant, adding water for resuspension, and obtaining an Au/cys-PEG nanoparticle solution;

(3) adding cysteine solution into the Au/cys-PEG nano-particle solution, stirring at room temperature, centrifuging to remove supernatant, adding water for resuspension, and obtaining the Au/cys-PEG/cys nano-antibacterial solution.

8. The method of claim 7, wherein: the molar concentration of the chloroauric acid solution in the step (1) is 10-20 mmol/L; the mass fraction of the trisodium citrate is 0.1-2.0%; the molar concentration of the sodium hydroxide solution is 100-300 mmol/L; the molar concentration of the cysteine solution is 100-450 mmol/L; chloroauric acid solution: water: trisodium citrate solution: sodium hydroxide solution: the volume ratio of the cysteine solution is 1-2: 45-50: 0.5-10: 0.5-10: 0.5 to 10; preferably: in the step (1), the particle size of the Au/cys nano-particles is 10-15 nm; the molar concentration of Au/cys in the Au/cys nanoparticle solution is 1-15 nmol/L.

9. The method of claim 7, wherein: the volume ratio of the Au/cys nanoparticle solution to the thiol-polyethylene glycol solution in the step (2) is 1 mL: (10-30) mu L; the average molecular weight of the sulfhydryl polyethylene glycol is 350-8000 kD, and the concentration of the sulfhydryl polyethylene glycol solution is 1-10 mM; the molar concentration of Au/cys-PEG in the Au/cys-PEG nano-particle solution is 1-15 nmol/L;

in the step (3), the volume ratio of the Au/cys-PEG nanoparticle solution to the cysteine solution is 1 mL: (30-80) mu L; the molar concentration of the cysteine solution is 40-80 mmol/L; the molar concentration of Au/cys-PEG/cys in the Au/cys-PEG/cys nano-particle solution is 1-15 nmol/L;

further preferably: the cysteine in step (1) and step (3) may be D-cysteine or L-cysteine.

10. The chiral cysteine nano self-assembled antibacterial material of claim 1, which is applied as an antibacterial material.

Technical Field

The invention belongs to the technical field of nano materials, and particularly relates to a chiral cysteine nano self-assembled antibacterial material, and a preparation method and application thereof.

Background

L-cysteine (L-Cys) is a common amino acid in organisms, has the effects of eliminating inflammatory reaction, accelerating the decomposition and elimination of heavy metal ions in vivo, reducing the accumulation of acetaldehyde in vivo, protecting the liver and the like, and is currently used in the fields of food, medicine, cosmetics and the like. D-cysteine (D-Cys) is a natural enantiomer of L-Cys, is mainly synthesized by chiral catalysis of the L-Cys, has a certain antibacterial effect on most bacteria such as escherichia coli, staphylococcus aureus and the like, and particularly has a strong antibacterial effect on the escherichia coli. But the industrial application of the compound is seriously influenced by the problems of high preparation cost, low solubility, instability and the like.

Disclosure of Invention

The invention aims to provide a chiral cysteine nano self-assembly antibacterial material, and a preparation method and application thereof.

The purpose of the invention is realized by the following technical scheme:

a chiral cysteine nano self-assembly antibacterial material is prepared by the following steps:

(1) mixing water and a chloroauric acid solution, stirring and heating to boil, then adding a trisodium citrate solution, heating and stirring until the color of the solution is not changed, stopping heating, adding a sodium hydroxide solution, finally adding a cysteine solution, stirring and cooling to room temperature to obtain an Au/cys nanoparticle solution;

(2) adding a sulfhydryl polyethylene glycol solution into the Au/cys nanoparticle solution, stirring at room temperature, centrifuging to remove a supernatant, adding water for resuspension, and obtaining an Au/cys-PEG nanoparticle solution;

(3) adding cysteine solution into the Au/cys-PEG nano-particle solution, stirring at room temperature, centrifuging to remove supernatant, adding water for resuspension, and obtaining the Au/cys-PEG/cys nano-antibacterial solution.

A preparation method of a chiral cysteine nano self-assembly antibacterial material comprises the following steps:

(1) mixing water and a chloroauric acid solution, stirring and heating to boil, then adding a trisodium citrate solution, heating and stirring until the color of the solution is not changed, stopping heating, adding a sodium hydroxide solution, finally adding a cysteine solution, stirring and cooling to room temperature to obtain an Au/cys nanoparticle solution;

(2) adding a sulfhydryl polyethylene glycol solution into the Au/cys nanoparticle solution, stirring at room temperature, centrifuging to remove a supernatant, adding water for resuspension, and obtaining an Au/cys-PEG nanoparticle solution;

(3) adding cysteine solution into the Au/cys-PEG nano-particle solution, stirring at room temperature, centrifuging to remove supernatant, adding water for resuspension, and obtaining the Au/cys-PEG/cys nano-antibacterial solution.

The method comprises the following steps: the molar concentration of the chloroauric acid solution in the step (1) is 10-20 mmol/L; the mass fraction of the trisodium citrate is 0.1-2.0%; the molar concentration of the sodium hydroxide solution is 100-300 mmol/L; the molar concentration of the cysteine solution is 100-450 mmol/L; chloroauric acid solution: water: trisodium citrate solution: sodium hydroxide solution: the volume ratio of the cysteine solution is 1-2: 45-50: 0.5-10: 0.5-10: 0.5 to 10.

In some preferred embodiments: chloroauric acid solution: water: trisodium citrate solution: sodium hydroxide solution: the volume ratio of the cysteine solution is 1-2: 45-50: 0.5-1.5: 0.5-1.5: 0.5 to 1.5.

The method comprises the following steps: in the step (1), the particle size of the Au/cys nano-particles is 10-15 nm; the molar concentration of Au/cys in the Au/cys nanoparticle solution is 1-15 nmol/L.

The method comprises the following steps: the volume ratio of the Au/cys nanoparticle solution to the thiol-polyethylene glycol solution in the step (2) is 1 mL: (10-30) mu L; the average molecular weight of the sulfhydryl polyethylene glycol is 350-8000 kD, and the concentration of the sulfhydryl polyethylene glycol is 1-10 mM; the molar concentration of Au/cys-PEG in the Au/cys-PEG nanoparticle solution is 1-15 nmol/L.

The method comprises the following steps: in the step (3), the volume ratio of the Au/cys-PEG nanoparticle solution to the cysteine solution is 1 mL: (30-80) mu L; the molar concentration of the cysteine solution is 40-80 mmol/L; the molar concentration of Au/cys-PEG/cys in the Au/cys-PEG/cys nanoparticle solution is 1-15 nmol/L.

The method comprises the following steps: the cysteine in the step (1) and the step (3) is D-cysteine or L-cysteine.

The technical scheme of the invention is as follows: the chiral cysteine nano self-assembled antibacterial material is applied to the aspect of being used as an antibacterial material.

The invention has the beneficial effects that:

(1) high-efficiency and broad-spectrum antibacterial activity: the antibacterial agent can generate strong bactericidal effect on gram-positive bacteria and gram-negative bacteria only by a small amount of nano material with a wide spectrum antibacterial property;

(2) the chemical property is stable; can effectively prevent the agglomeration of the nano gold particles, can be stored for a long time and has higher antibacterial activity;

(3) the biological safety is good: cysteine is directionally assembled on the surface of the nanogold, so that the cytotoxicity of the nanogold can be greatly reduced;

(4) the synthesis method is simple: the reaction condition is mild, the reagent is green and environment-friendly, the operation is simple, and the control is easy.

Drawings

FIG. 1 is a diagram of ultraviolet spectra of different nanomaterial solutions after being placed at 4 ℃ for 14 days

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention:

example 1

(1) Preparing Au/D-cys nanoparticles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L D-cys solution, and stirring at room temperature for 2 hours to obtain Au/D-cys nanoparticle solution; the particle size of the Au/D-cys nano particles is 15 +/-2 nm; the molar concentration of Au/D-cys in the Au/D-cys nanoparticle solution was 5 nmol/L.

(2) Preparing Au/D-cys-PEG nanoparticles:

adding 20 mu L of 6mM sulfhydryl polyethylene glycol solution (molecular weight is 1000kD) into 1mL Au/D-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm, removing supernatant, and adding ultrapure water for resuspension to obtain Au/D-cys-PEG nanoparticle solution; the molar concentration of Au/D-cys-PEG in the Au/D-cys-PEG nanoparticle solution is 5 nmol/L.

(3) Preparing Au/D-cys-PEG/D-cys nano particles:

adding 50 mu L of 80mmol/L D-cys solution into 1mL of Au/cys-PEG nano-particle solution obtained in the step (2), stirring at room temperature for 20min, centrifuging at 7200rpm/min for 25min, removing supernatant, and adding ultrapure water for resuspension to obtain Au/D-cys-PEG/D-cys nano-antibacterial solution; the molar concentration of Au/D-cys-PEG/D-cys in the Au/D-cys-PEG/D-cys nanoparticle solution was 5 nmol/L.

Example 2

(1) Preparing Au/L-cys nano particles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L L-cys solution, and stirring at room temperature for 2 hours to obtain Au/L-cys solution; the particle size of the Au/L-cys nano-particles is 10 +/-2 nm; the molar concentration of Au/L-cys in the Au/L-cys nanoparticle solution is 5 nmol/L;

(2) preparing Au/L-cys-PEG nanoparticles:

adding 20 mu L of 6mM sulfhydryl polyethylene glycol solution (molecular weight is 1000kD) into 1mL Au/L-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm, removing supernatant, and adding ultrapure water for resuspension to obtain Au/L-cys-PEG nanoparticle solution; the molar concentration of Au/L-cys-PEG in the Au/L-cys-PEG nanoparticle solution is 5 nmol/L;

(3) preparing Au/L-cys-PEG/L-cys nano particles:

adding 50 mu L of 80mmol/L L-cys solution into 1mL of Au/L-cys-PEG nano-particle solution obtained in the step (2), stirring at room temperature for 20min, centrifuging at 7200rpm/min for 25min, removing supernatant, and adding ultrapure water for resuspension to obtain Au/L-cys-PEG/L-cys nano-antibacterial solution; the molar concentration of Au/L-cys-PEG/L-cys in the Au/L-cys-PEG/L-cys nanoparticle solution is 5 nmol/L;

example 3

(1) Preparing Au/D-cys nanoparticles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.5% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 250mmol/L D-cys solution, and stirring at room temperature for 2h to obtain Au/D-cys nanoparticle solution; the particle size of the Au/D-cys nano-particles is 10 +/-1 nm; the molar concentration of Au/D-cys in the Au/D-cys nanoparticle solution is 10 nmol/L;

(2) preparing Au/D-cys-PEG nanoparticles:

adding 20 mu L of 3mM sulfhydryl polyethylene glycol solution (molecular weight is 350kD) into 1mL Au/D-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm, removing supernatant, and adding ultrapure water for resuspension to obtain Au/D-cys-PEG nanoparticle solution; the molar concentration of Au/D-cys-PEG in the Au/D-cys-PEG nano-particle solution is 10 nmol/L;

(3) preparing Au/D-cys-PEG/D-cys nano particles:

adding 50 mu L of 40mmol/L D-cys solution into 1mL of Au/D-cys-PEG nano-particle solution obtained in the step (2), stirring at room temperature for 20min, centrifuging at 7200rpm/min for 25min, removing supernatant, and adding ultrapure water for resuspension to obtain Au/D-cys-PEG/D-cys nano-antibacterial solution; the molar concentration of Au/D-cys-PEG/D-cys in the Au/D-cys-PEG/D-cys nanoparticle solution is 10 nmol/L.

Example 4

(1) Preparing Au/L-cys nano particles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.5% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 250mmol/L L-cys solution, and stirring at room temperature for 2h to obtain Au/L-cys nanoparticle solution; the particle size of the Au/L-cys nano-particles is 10 +/-1 nm; the molar concentration of Au/L-cys in the Au/L-cys nano-particle solution is 10 nmol/L;

(2) preparing Au/L-cys-PEG nanoparticles:

adding 20 mu L of 3mM sulfhydryl polyethylene glycol solution (molecular weight is 350kD) into 1mL Au/L-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm, removing supernatant, and adding ultrapure water for resuspension to obtain Au/L-cys-PEG nanoparticle solution; the molar concentration of Au/L-cys-PEG in the Au/L-cys-PEG nanoparticle solution is 10 nmol/L;

(3) preparing Au/L-cys-PEG/L-cys nano particles:

adding 50 mu L of 40mmol/L L-cys solution into 1mL of Au/L-cys-PEG nano-particle solution obtained in the step (2), stirring at room temperature for 20min, centrifuging at 7200rpm/min for 25min, removing supernatant, and adding ultrapure water for resuspension to obtain Au/L-cys-PEG/L-cys nano-antibacterial solution; the molar concentration of Au/L-cys-PEG/L-cys in the Au/L-cys-PEG/L-cys nanoparticle solution is 10 nmol/L.

Comparative example 1

Pure gold nanoparticles were used as comparative example 1, and the molar concentration of Au nanoparticles was 5 nmol/L.

The synthesis steps are as follows: putting a clean conical flask into a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of chloroauric acid solution with the molar concentration of 10mmol/L, stirring and heating to boiling at 900r/min, then quickly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, and uniformly stirring for 2h to obtain the gold nanoparticle solution.

Comparative example 2

The Au/D-cys nanoparticles were used as comparative example 2, and the molar concentration of the Au/D-cys nanoparticles was 5 nmol/L.

The synthesis steps are as follows: putting a clean conical flask into a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L D-cys solution, and stirring at room temperature for 2h to obtain the Au/D-cys solution.

Comparative example 3

The Au/L-cys nanoparticles were used as comparative example 3, and the molar concentration of the Au/L-cys nanoparticles was 5 nmol/L.

The synthesis steps are as follows: putting a clean conical flask into a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L L-cys solution, and stirring at room temperature for 2h to obtain Au/L-cys solution.

Comparative example 4

The Au/D-cys-PEG nanoparticles were used as comparative example 4, and the molar concentration of the Au/D-cys nanoparticles was 5 nmol/L. The synthesis steps are as follows:

(1) preparing Au/D-cys nanoparticles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L D-cys solution, and stirring at room temperature for 2 hours to obtain Au/D-cys solution;

(2) preparing Au/D-cys-PEG nanoparticles:

and (2) adding 20 mu L of 6mM sulfhydryl polyethylene glycol solution (molecular weight is 1000kD) into 1mL of the Au/D-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm/min, removing supernatant, and adding ultrapure water to carry out resuspension to obtain the Au/D-cys-PEG nanoparticle solution.

Comparative example 5

The Au/L-cys-PEG nanoparticles were used as comparative example 5, and the molar concentration of the Au/L-cys nanoparticles was 5 nmol/L.

The synthesis steps are as follows:

(1) preparing Au/L-cys nano particles:

placing a clean conical flask in a stirring heater, sequentially adding 48.75mL of ultrapure water and 1.25mL of 10mmol/L chloroauric acid solution, stirring and heating to boil, rapidly adding 1mL of 1.2% trisodium citrate solution, stopping heating after the solution becomes wine red, sequentially adding 1mL of 150mmol/L sodium hydroxide solution and 1mL of 200mmol/L L-cys solution, and stirring at room temperature for 2 hours to obtain Au/L-cys solution;

(2) preparing Au/L-cys-PEG nanoparticles:

and (2) adding 20 mu L of 6mM sulfhydryl polyethylene glycol solution (molecular weight is 1000kD) into 1mL Au/L-cys nanoparticle solution obtained in the step (1), stirring for 1h at room temperature, centrifuging for 25min at 7200rpm, removing supernatant, and adding ultrapure water to carry out resuspension to obtain the Au/L-cys-PEG nanoparticle solution.

Comparative example 6

Comparative example 6 was prepared as a 200mmol/L D-cysteine (D-cys) solution.

20mg of D-cys were weighed out and dissolved in ultrapure water to give a solution having a molar concentration of 200mmol/L D-cys.

Comparative example 7

Comparative example 7 was prepared as a 200mmol/L L-cysteine (L-cys) solution.

20mg of L-cys was weighed out and dissolved in ultrapure water to give a solution having a molar concentration of 200mmol/L L-cys.

Blank group

Ultrapure water was used as a blank set.

And (3) performance detection:

1) test of antibacterial Property

The antibacterial activity of the nano material prepared in the embodiment on gram-positive bacteria and gram-negative bacteria is measured by taking staphylococcus aureus and escherichia coli as representative bacteria, the materials in the embodiments 1-4, the blank groups and the comparative examples 1-7 are in the same volume, and after the materials are respectively mixed with a bacterial solution and cultured for 4 hours, the antibacterial performance of the chiral cysteine nano self-assembly material is evaluated by comparing the change of bacterial colony number.

Before the sterilization treatment, the number of bacterial colonies was 10⁸CFU/mL。

The change in the bacterial colony count after the mixed culture of examples 1 to 4, blanks and comparative groups 1 to 7 with the bacterial solution is shown in the table.

TABLE 1 variation of E.coli colony count

As can be seen from Table 1, the colony number of Escherichia coli treated by the Au/D-cys-PEG/D-cys or Au/L-cys-PEG/L-cys chiral nano material (examples 1 to 4) is far lower than that of the blank group, the pure nanogold (comparative example 1), the Au/D-cys (comparative example 2), the Au/L-cys particle group (comparative example 3), the Au/D-cys/PEG (comparative example 4), the Au/L-cys/PEG (comparative example 5), the pure D-cys (comparative example 6) and the pure L-cys (comparative example 7), which indicates that the prepared chiral nano antibacterial has strong antibacterial activity.

TABLE 2 Staphylococcus aureus colony number variation values

Group of	Colony number reduction value (log CFU/mL)
		Example 1	4.46±0.15
Example 2	4.79±0.26
		Example 3	4.66±0.12
Example 4	4.93±0.09
		Comparative example 1	0.24±0.20
Comparative example 2	0.46±0.34
		Comparative example 3	0.52±0.41
Comparative example 4	0.60±0.52
		Comparative example 5	0.39±0.09
Comparative example 6	0.43±0.12
		Comparative example 7	0.30±0.01
Blank group	0

As can be seen from Table 2, the colony number of the staphylococcus aureus treated by the Au/D-cys-PEG/D-cys or Au/L-cys-PEG/L-cys chiral nano material (examples 1 to 4) is far lower than that of the blank group, the pure nanogold (comparative example 1), the Au/D-cys (comparative example 2), the Au/L-cys particle group (comparative example 3), the Au/D-cys/PEG (comparative example 4), the Au/L-cys/PEG (comparative example 5), the pure D-cys (comparative example 6) and the pure L-cys (comparative example 7), which indicates that the prepared chiral nano antibacterial has strong antibacterial activity.

Compared with the table 1, the antibacterial effect of Au/D-cys-PEG/D-cys or Au/L-cys-PEG/L-cys on staphylococcus aureus is slightly lower than that of Escherichia coli. The reason is that staphylococcus aureus belongs to gram-positive bacteria, and the outer layer of staphylococcus aureus has a thick cell wall and has a certain protection effect on bacteria, so that staphylococcus aureus is difficult to kill compared with gram-negative bacteria.

2) Stability testing

Placing examples 1-4, blanks and comparative examples 1-7 in a 4 ℃ refrigerator, after 14 days, taking the same volume materials of examples 1-4, blanks and comparative examples 1-7, respectively mixing and culturing with an escherichia coli solution for 4 hours, and evaluating the stability of the chiral cysteine nano self-assembly material by comparing the change of the colony number of escherichia coli.

TABLE 3 detection of antibacterial Activity of chiral nano self-assembled materials after 14 days of storage

Group of	Colony number reduction value (log CFU/mL)
		Example 1	6.42±0.14
Example 2	6.34±0.24
		Example 3	6.61±0.12
Example 4	6.53±0.17
		Comparative example 1	0.20±0.20
Comparative example 2	0.24±0.10
		Comparative example 3	0.15±0.11
Comparative example 4	0.30±0.18
		Comparative example 5	0.24±0.13
Comparative example 6	0.04±0.04
		Comparative example 7	0.03±0.09
Blank group	0

As can be seen from Table 3, the antibacterial activity of the Au/D-cys-PEG/D-cys or Au/L-cys-PEG/L-cys chiral nanomaterial did not change much after being stored for 14 days at 4 ℃ (examples 1 to 4). In contrast, the pure D-cys (comparative example 6) or L-cys (comparative example 7) and the Au/D-cys (comparative example 2) or Au/L-cys particle group (comparative example 3) modified with nanogold lose their activity very quickly, which may be related to the stability of the nanomaterial. When the nanomaterial is aggregated (fig. 1), its antibacterial activity is significantly reduced. The method can obviously improve the stability of cysteine and nano-gold and prolong the antibacterial activity of the cysteine and nano-gold.