CN111973794B

CN111973794B - Preparation method of nano-silver slow-release antibacterial agent

Info

Publication number: CN111973794B
Application number: CN202010878207.4A
Authority: CN
Inventors: 李义涛; 孙明刚; 钟颖贤; 黄永锋; 张宏清; 唐火强
Original assignee: Dongguan HEC Tech R&D Co Ltd
Current assignee: Dongguan HEC Tech R&D Co Ltd
Priority date: 2020-08-27
Filing date: 2020-08-27
Publication date: 2023-05-12
Anticipated expiration: 2040-08-27
Also published as: CN111973794A

Abstract

The invention provides a preparation method of a nano silver slow-release antibacterial agent, which adopts polyphenol hydroxyl flavonol compounds as a reducing agent and a dispersing agent, reduces the introduction of impurity compounds in the nano silver synthesis process, is free from using and generating toxic and harmful impurities in the preparation process, is safe and environment-friendly, and simultaneously selects carboxylate compounds as a PH regulator, so that acidic groups in the PH regulator react with phenolic hydroxyl groups in the reducing agent, and the reduction reaction activity can be controlled by controlling the PH regulator, thereby controlling the particle size and the particle size distribution of nano silver. The reducing agent selected by the invention can also coordinate and combine with nano silver to realize the wrapping of silver nano clusters, plays a role in protecting high-activity silver nano clusters from oxidation, can adjust the coordination binding force and wrapping degree of myricetin by adjusting process conditions, and realizes the aim of adjusting the release rate of silver ions.

Description

Preparation method of nano-silver slow-release antibacterial agent

Technical Field

The invention relates to the technical field of antibacterial agents, in particular to a preparation method of a nano-silver slow-release antibacterial agent, an antibacterial agent obtained by the preparation method and application thereof.

Background

The nano silver antibacterial agent is a novel antibacterial material developed based on nano technology, has excellent antibacterial effect and safety which are incomparable with the traditional inorganic antibacterial agent due to quantum effect, small-size effect and extremely large specific surface area, and is an antibacterial agent with long-acting property and weather resistance. Nano silver has made great progress in biomedical application research, and nano silver antibacterial products are beginning to be applied to people's daily life.

The traditional nano silver preparation method comprises the following steps: polyol reduction method, sodium citrate reduction method, two-phase reduction method, ultrasonic radiation reduction method, etc., which have the following problems:

(1) The nano silver particles have high activity due to physical properties such as small particle size, large specific surface area and the like, and are easy to oxidize or react with other compounds in the use process;

(2) In the preparation process of the nano silver, different types of reducing agents and dispersing agents are often added for obtaining better size, and excessive dispersing agents and excessive reducing agents are removed, so that the problems of post-treatment and application development of the nano silver are always plagued;

(3) The nano silver is easy to agglomerate, the product with single particle size distribution is difficult to prepare, the particle size of the product is often distributed widely, and the stable and sustained release of the antibacterial performance of the nano silver is affected;

(4) In the use process of the nano silver, the nano silver wrapping technology determines whether the silver ion release rate of the nano silver is stable or not, and is another important factor of the antibacterial and bactericidal performance, and the silver ion release rate control is always a difficult point of application control of the nano silver.

Disclosure of Invention

In order to solve at least one of the problems of large reactivity, easy agglomeration, wide particle size distribution, difficult post-treatment, difficult release rate control and the like of the nano silver in the prior art, the invention provides a preparation method of the nano silver slow-release antibacterial agent.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

in one aspect, the invention provides a preparation method of a nano-silver slow-release antibacterial agent, which comprises the following steps:

s1, mixing a reducer solution and a silver source solution, adding a PH regulator, and carrying out a reduction reaction to obtain a silver nanocluster solution;

s2, freeze-drying the silver nanocluster solution to obtain a nano silver slow-release antibacterial agent;

wherein the reducing agent is polyphenol hydroxy flavonol compound, and the PH regulator contains carboxylate compound.

The reducing agent selected by the invention comprises the following components: carbonyl, phenolic hydroxyl and hydroxyl, the phenolic hydroxyl has a certain reducibility and can reduce Ag ⁺ The silver is reduced into nano silver simple substance, carbonyl, phenolic hydroxyl and hydroxyl can form organic ligand with silver in the reaction and freeze drying processes, nano silver is wrapped by ligand structure, and meanwhile, nano silver agglomeration is prevented, so that the dispersing effect is achieved. The PH regulator is equivalent to an activity regulator of a reaction system, on one hand, the PH regulator stabilizes the PH value of the system, ensures that phenolic hydroxyl reacts in a fixed PH environment, and promotes the stable generation of nano silver; on the other hand, the acidic group in the PH regulator can react with the phenolic hydroxyl group to generate phenolic ester compound, and the amount of the phenolic hydroxyl group is controlled by controlling the generation of the phenolic ester compound, so that the aim of regulating the reducibility of the reducer and further controlling the generation rate, the particle size and the distribution of the nano silver is fulfilled. Meanwhile, the phenolic hydroxyl group also has certain oxidation resistance, and the nano silver can be prevented from being oxidized under the wrapping of the reducing agent containing the phenolic hydroxyl group.

Further, the carboxylate compound is at least one of acetate and citrate.

In a specific embodiment of the present invention, the carboxylate compound is at least one of sodium acetate and trisodium citrate.

Further, the pH adjustor may further comprise a carboxylic acid or/and carboxylic anhydride compound corresponding to the carboxylate compound. The carboxylic acid and carboxylic anhydride compounds are acidic and are matched with basic carboxylate compounds, so that the PH value of a reaction system can be better stabilized, and the aim of stably preparing nano silver is fulfilled.

If the pH adjustor contains carboxylic acid or/and carboxylic anhydride compounds, the molar amount of the pH adjustor should be smaller than the molar amount of the carboxylate. In a specific embodiment of the present invention, the molar ratio of the carboxylic acid or/and carboxylic anhydride compound to the carboxylate salt is (2-4): 5.

Further, the carboxylic acid compound is at least one of acetic acid and citric acid; the carboxylic acid anhydride compound is at least one of acetic anhydride and citric anhydride. In view of the fact that carboxylic anhydride has a higher activity, it is more likely to undergo an esterification reaction with a phenolic hydroxyl group, and the acid anhydride compound is hydrolyzed to form a corresponding acid, and no other impurities are introduced, the carboxylic anhydride compound is preferable.

In particular embodiments of the present invention, the PH adjuster may be any one of acetic acid-sodium acetate mixture, citric acid-trisodium citrate mixture, acetic anhydride-sodium acetate mixture, citric anhydride-trisodium citrate mixture, acetic acid-acetic anhydride-sodium acetate mixture, citric acid-citric anhydride-trisodium citrate mixture.

Further, the reducing agent is myricetin compound, preferably at least one of myricetin and dihydromyricetin.

The structural formulas of myricetin (formula I) and dihydromyricetin (formula II) are respectively as follows:

further, the silver source is a silver carboxylate compound; further, the silver source is at least one of silver acetate and trisilver citrate.

Preferably, to avoid introducing impurities, the anion type of the silver source should be consistent with the PH adjuster.

Further, the concentration of the reducing agent solution is 0.1 to 10mmol/L, preferably 1 to 10mmol/L; the concentration of the silver source solution is 0.1-10 mmol/L, preferably 1-10 mmol/L; the molar ratio of the reducing agent to silver ions in the silver source solution is (1.5 to 10): 1, preferably (1.5 to 3): 1, and in this range, the particle size of the nano silver obtained is preferable, and if the amount of the reducing agent is smaller than the amount of silver ions, the reduction rate of silver ions becomes slow, resulting in an increase in the particle size of nano silver.

In particular embodiments of the invention, the concentration of the reducing agent solution is 0.1mmol/L, 0.5mmol/L, 1mmol/L, 2mmol/L, 3mmol/L, 4mmol/L, 5mmol/L, 6mmol/L, 7mmol/L, 8mmol/L, 9mmol/L, 10mmol/L, etc.

In specific embodiments of the present invention, the concentration of the silver source solution is 0.1mmol/L, 0.5mmol/L, 1mmol/L, 2mmol/L, 3mmol/L, 4mmol/L, 5mmol/L, 6mmol/L, 7mmol/L, 8mmol/L, 9mmol/L, 10mmol/L, and so forth.

In particular embodiments of the invention, the molar ratio of the reducing agent to silver ions in the silver source solution is 1.5:1, 1.9:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and so forth.

Further, the molar ratio of the reducing agent to the pH regulator is (2-10): 1. The amount of the pH adjustor is determined by the amount of phenolic hydroxyl groups in the reducing agent and the pH adjustment range, and in this molar ratio range, the obtained nano-silver has a good particle size and a narrow particle size distribution.

In particular embodiments of the invention, the molar ratio of the reducing agent to the pH adjustor is 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 9.6:1, 10:1, and the like.

Further, the pH adjustor is provided in the form of an aqueous solution containing a carboxylate compound, the concentration of the aqueous solution being 5 to 10mmol/L, preferably added in a dropwise manner.

In specific embodiments of the present invention, the concentration of the aqueous solution of the carboxylate-containing compound is 5mmol/L, 6mmol/L, 7mmol/L, 8mmol/L, 9mmol/L, 10mmol/L, etc.

Further, the reduction reaction is carried out under the ultrasonic condition, the reduction reaction temperature is 30-70 ℃, and the reduction reaction time is 2-7 h. The ultrasonic condition is to better disperse the nano silver, and in the temperature range, the reduction reaction rate is high, and the obtained nano silver has good particle size and particle size distribution. In a specific embodiment of the present invention, the reduction reaction temperature is 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, etc.; the reduction reaction time is 2h, 3h, 4h, 5h, 6h, 7h, etc.

Further, the freeze-drying treatment specifically includes: the rapid freeze treatment is carried out at a temperature of-5 ℃ to-30 ℃ and then reduced-pressure freeze drying is carried out in a freeze dryer, and preferably the freeze drying temperature is the same as the rapid freeze treatment temperature. The inventor discovers that the freezing technology is an important factor for controlling the synthesis of the ligand between the nano silver and the reducing agent, and the nano silver and carbonyl, hydroxyl and phenolic hydroxyl in the myricetin compound structure form the ligand through freezing treatment, so that the silver nanocluster is dispersed and wrapped, and the slow release effect of the nano silver is controlled. The inventor also found that the slow release effect of the antibacterial agent obtained by performing low-temperature rapid freezing and then freeze drying is better, because the ligand structure can be more stable by two freezing treatments.

In another aspect, the invention provides the nano-silver slow-release antibacterial agent obtained by the preparation method.

Further, the particle size of the nano silver is below 30nm, preferably 5-30nm, for example: 5nm, 6.25nm, 10nm, 15nm, 18.81nm, 20nm, 25nm, 29.79nm, 30nm, etc.

In a third aspect, the invention provides application of the nano-silver slow-release antibacterial agent in antibacterial dressing. The nano silver slow release antibacterial agent can be directly used in wound dressing and antibacterial gel, such as woundplast, burn patch and other products, and has the effects of broad-spectrum, lasting and stable silver ion release.

The invention has the beneficial effects that:

(1) The myricetin compound is used as a reducing agent and a dispersing agent, so that the introduction of impurity compounds in the synthesis process of the nano silver is reduced, toxic and harmful impurities are not generated in the preparation process, and the preparation method is safe and environment-friendly;

(2) The myricetin compound can be coordinated and combined with nano silver to realize the wrapping of silver nanoclusters, plays a role in protecting high-activity silver nanoclusters from being oxidized, and can adjust the coordination binding force and wrapping degree of myricetin by adjusting process conditions so as to realize the aim of adjusting the release rate of nano silver;

(3) The carboxylate compound is selected as a PH regulator, so that an acidic group in the PH regulator reacts with a phenolic hydroxyl group in a reducing agent, the reduction reaction activity can be controlled by controlling the PH regulator, and the grain size and grain size distribution of the nano silver are further controlled;

(4) The particle size of the nano silver prepared by the method is unimodal, and the particle size is below 30nm and the distribution is narrow through a Markov characterization test, so that the stability of the antibacterial agent can be effectively improved;

(5) The myricetin compound has certain antibacterial and anti-inflammatory effects, and can enhance the antibacterial performance of the product together with nano silver.

Definition of terms

The solutions described in the present invention are aqueous solutions unless specified otherwise.

The term "water" as used herein refers to "deionized water".

All ranges cited herein are inclusive unless clearly indicated to the contrary.

The numbers in the present invention are approximations, by use of the antecedent "about" or "about" herein. The numerical values of the numbers may differ by 1%, 2%, 5%, 7%, 8%, 10%, etc. Whenever a number is disclosed having a value of N, any number having a value of N+/-1%, N+/-2%, N+/-3%, N+/-5%, N+/-7%, N+/-8% or N+/-10% will be explicitly disclosed, where "+/-" means plus or minus, and a range between N-10% and N+10% is also disclosed.

The following definitions as used herein should be applied unless otherwise indicated. For the purposes of the present invention, the chemical elements are in accordance with the CAS version of the periodic Table of the elements, and the 75 th edition handbook of chemistry and Physics, 1994. In addition, general principles of organic chemistry may be referenced to the descriptions in "Organic Chemistry", thomas Sorrell, university Science Books, sausalato:1999, and "March's Advanced Organic Chemistry" by Michael b.smith and Jerry March, john Wiley & Sons, new york:2007, the entire contents of which are incorporated herein by reference.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety unless a particular paragraph is cited. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Drawings

FIG. 1 is a graph showing the concentration of silver ions released over time for examples 1-3 and comparative examples 1-2.

Detailed Description

The following description is of the preferred embodiment of the present invention and is not intended to limit the invention, but is intended to cover any modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Example 1

50mL of 1mmol/L silver acetate solution, 50mL of 3mmol/L myricetin solution and 5mL of 10mmol/L acetic anhydride-sodium acetate (molar ratio of 2:5) mixed solution are respectively prepared, the silver acetate solution and the myricetin solution are mixed and put into an ultrasonic reactor, the reaction temperature is controlled at 30 ℃, 5mL of acetic anhydride-sodium acetate mixed solution is dropwise added for reduction reaction for 5h, and the silver nanocluster solution is obtained.

Freezing the silver nanocluster solution at-5 ℃ by using a freezer, sending a sample into a freeze dryer after freezing, and drying under reduced pressure at-5 ℃ to obtain the nano silver slow-release antibacterial agent.

Example 2

50mL of 1mmol/L of trisilver citrate solution, 100mL of 3mmol/L of dihydromyricetin solution and 10mL of 5mmol/L of mixed solution of citric anhydride and trisodium citrate (molar ratio is 3:5) are respectively prepared, the trisilver citrate solution and the dihydromyricetin solution are mixed, the mixture is put into an ultrasonic reactor, the reaction temperature is controlled at 70 ℃,10 mL of mixed solution of citric anhydride and trisodium citrate is dropwise added, and the reduction reaction is carried out for 2h, so that the silver nanocluster solution is obtained.

Freezing the silver nanocluster solution at-30 ℃ by using a freezer, sending a sample into a freeze dryer after freezing, and drying under reduced pressure at-30 ℃ to obtain the nano silver slow-release antibacterial agent.

Example 3

Respectively preparing 50mL of 5mmol/L silver acetate solution, 80mL of 6mmol/L dihydromyricetin solution, 5mL of 10mmol/L acetic anhydride-sodium acetate (molar ratio of 4:5) mixed solution, mixing the silver acetate solution and the dihydromyricetin solution, placing the mixture into an ultrasonic reactor, controlling the reaction temperature at 40 ℃, dropwise adding 5mL of acetic anhydride-sodium acetate mixed solution, and carrying out reduction reaction for 7h to obtain the silver nanocluster solution.

Freezing the silver nanocluster solution at-10deg.C with a freezer, freezing, and drying the sample in a freeze dryer under reduced pressure at-10deg.C to obtain the nanometer silver slow-release antibacterial agent.

Comparative example 1

The only difference compared to example 1 is that the pH adjustor is ammonia.

Comparative example 2

The only difference compared to example 1 is that the reducing agent is glucose.

Test data

The silver nanocluster solutions obtained in examples 1 to 3 and comparative examples 1 to 2 were subjected to particle size measurement using a malvern particle size tester, and the data results are shown in table 1.

The nano silver slow release antibacterial agents obtained in examples 1-3 and comparative examples 1-2 were coated on medical dressings by a coating technique, and the change of silver ion release concentration with time was measured, and the results are shown in fig. 1.

TABLE 1

Name of the name	Example 1	Example 2	Example 3	Comparative example 1	ComparisonExample 2
						Particle size/nm	6.27	18.81	29.79	53.45	102.12
PDI	0.229	0.168	0.197	0.684	0.739

As can be seen from table 1, the nano silver obtained by the preparation method provided by the invention has small particle size, the size of PDI (polydispersity index) reflects the width of the range of nano silver particle size, and the PDI result shows that the nano silver particle size distribution of the embodiment of the invention is narrower.

As can be seen from fig. 1, the silver ion release rate is stable in the embodiment of the present invention, which indicates that the myricetin compound effectively encapsulates the nano silver, whereas in comparative example 2, which uses glucose as a reducing agent, the early silver ion release rate is too fast and the later silver ion release rate is reduced because the nano silver is not encapsulated. In comparative example 1, ammonia water is used as a PH regulator, and the obtained nano silver particles have larger particle diameter, wide particle size distribution, slower silver ion release rate and unstable release rate in the early and later stages.

The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The preparation method of the nano silver slow-release antibacterial agent is characterized by comprising the following steps of:

wherein the reducing agent is polyphenol hydroxy flavonol compound, and the PH regulator contains carboxylate compound; the freeze drying treatment specifically comprises the following steps: firstly, rapidly freezing at the temperature of minus 5 ℃ to minus 30 ℃, and then performing reduced pressure freeze drying in a freeze dryer.

2. The method according to claim 1, wherein the carboxylate compound is at least one of acetate and citrate.

3. The method according to claim 1, wherein the reducing agent is at least one of myricetin and dihydromyricetin.

4. The method according to claim 1, wherein the PH adjuster further comprises a carboxylic acid compound or/and a carboxylic anhydride compound corresponding to the carboxylate compound, and the carboxylic acid compound is at least one of acetic acid and citric acid; the carboxylic acid anhydride compound is at least one of acetic anhydride and citric anhydride.

5. The method of claim 1, wherein the silver source is a silver carboxylate compound.

6. The method according to claim 5, wherein the silver source is at least one of silver acetate and trisilver citrate.

7. The method according to claim 1, wherein the concentration of the reducing agent solution is 0.1 to 10mmol/L, and the concentration of the silver source solution is 0.1 to 10mmol/L.

8. The method according to claim 1, wherein the molar ratio of the reducing agent to silver ions in the silver source solution is (1.5-10): 1.

9. The method according to claim 1, wherein the molar ratio of the reducing agent to the pH adjuster is (2-10): 1.

10. The preparation method according to claim 1, wherein the reduction reaction is carried out under ultrasonic conditions, the reduction reaction temperature is 30-70 ℃, and the reduction reaction time is 2-7 h.

11. The nano-silver slow-release antibacterial agent obtained by the preparation method of any one of claims 1-10.

12. Use of the nano-silver slow-release antibacterial agent according to claim 11 for preparing medical dressing.