阅读说明：本技术 一种动态交联的纳米精油抗菌乳液及其制备方法和应用 (Dynamically crosslinked nano essential oil antibacterial emulsion and preparation method and application thereof ) 是由 朱东雨 肖玮 李秋怡 王洁烽 蓝明辉 王铮泽 陈海松 于 2021-08-18 设计创作，主要内容包括：本发明提供了一种动态交联的纳米精油抗菌乳液及其制备方法和应用。本发明提供的动态交联纳米精油抗菌乳液中,以具有抗菌特性的β-环糊精改性的环氧丙基季铵盐作为表面活性剂,以金刚烷为封端的分子作为交联剂；β-环糊精与金刚烷能形成稳定的络合物,因此交联剂与表面活性剂形成三维网络状分子结构,并且还能和环氧丙基季铵盐的长链形成客体竞争的特点,实现降低长链被包裹的概率,增强分子稳定性；同时表面活性剂一端的β-环糊精可与抑菌精油络合,从而实现动态释放精油的目的。本发明制备得到的纳米精油抗菌乳液不仅具有良好的稳定性,同时抑菌效果突出,还在一定程度上能实现抑菌精油的有效缓释,能够广泛应用于食品或日化品等领域。(The invention provides a dynamic cross-linked nano essential oil antibacterial emulsion and a preparation method and application thereof. In the dynamic crosslinking nano essential oil antibacterial emulsion provided by the invention, beta-cyclodextrin modified epoxy propyl quaternary ammonium salt with antibacterial property is used as a surfactant, and adamantane is used as a terminated molecule as a crosslinking agent; the beta-cyclodextrin and the adamantane can form a stable complex, so that the cross-linking agent and the surfactant form a three-dimensional network molecular structure, and can also form guest competition with the long chain of the glycidyl quaternary ammonium salt, thereby realizing the purposes of reducing the probability of wrapping the long chain and enhancing the molecular stability; meanwhile, the beta-cyclodextrin at one end of the surfactant can be complexed with the bacteriostatic essential oil, so that the aim of dynamically releasing the essential oil is fulfilled. The nano essential oil antibacterial emulsion prepared by the invention has good stability and outstanding antibacterial effect, can realize effective slow release of antibacterial essential oil to a certain extent, and can be widely applied to the fields of food or daily chemicals and the like.)

1. A dynamic cross-linked nano essential oil antibacterial emulsion is characterized in that the nano essential oil antibacterial emulsion comprises water, bacteriostatic essential oil, a surfactant and a cross-linking agent;

wherein the mass ratio of water, bacteriostatic essential oil and surfactant in the nano essential oil antibacterial emulsion is 100: 0.5-3: 0.2-2; the molar ratio of the cross-linking agent to the surfactant is 1: 3-6;

the surfactant is beta-cyclodextrin modified epoxy propyl quaternary ammonium salt; the cross-linking agent is a molecule taking adamantane as an end cap, and the structural formula of the cross-linking agent is as follows:

wherein n is 400-1000, and n is a positive integer.

2. The nano essential oil antibacterial emulsion according to claim 1, wherein the bacteriostatic essential oil is at least one of cinnamon essential oil or oregano essential oil; the epoxy propyl quaternary ammonium salt is N, N-3-dimethyl-1-epoxy propyl-dodecyl ammonium.

3. The nano essential oil antibacterial emulsion as claimed in claim 1, wherein the particle size of the nano essential oil antibacterial emulsion is 100-800 nm.

4. The nano essential oil antibacterial emulsion according to claim 1, wherein the mass ratio of water, bacteriostatic essential oil and surfactant in the nano essential oil antibacterial emulsion is 100: 1-2: 0.5-1; the molar ratio of the cross-linking agent to the surfactant is 1: 4-5.

5. The nano essential oil antibacterial emulsion according to claim 1, wherein the preparation method of the surfactant comprises the following steps:

adding beta-cyclodextrin and epoxy propyl quaternary ammonium salt into alkali liquor, reacting for 18-24 h at 55-70 ℃, performing rotary evaporation, extraction, column chromatography and drying to obtain the surfactant.

6. The nano essential oil antibacterial emulsion according to claim 5, wherein the molar ratio of the glycidyl quaternary ammonium salt to the beta-cyclodextrin is 1-2: 1; the alkali liquor is NaOH solution.

7. The nano essential oil antibacterial emulsion according to claim 1, wherein the preparation method of the cross-linking agent comprises the following steps:

s1: reacting adamantane formic acid and thionyl chloride at 60-90 ℃, performing condensation reflux for 2-4 h, adding dichloromethane after the reaction is finished, performing rotary evaporation, and performing vacuum drying to prepare adamantane acyl chloride;

s2: dissolving PEG, triethylamine and adamantane acyl chloride in dichloromethane, reacting, purifying and drying to obtain the cross-linking agent.

8. The nano essential oil antibacterial emulsion as claimed in claim 7, wherein the molar ratio of adamantanecarboxylic acid to thionyl chloride in S1 is 1: 2-1: 5; in S2, the molar ratio of adamantane acyl chloride, PEG and triethylamine is 5-10: 1-2: 5-15.

9. The preparation method of the nano essential oil antibacterial emulsion as claimed in any one of claims 1 to 8, which is characterized by comprising the following steps: mixing water, bacteriostatic essential oil, surfactant and cross-linking agent, and mechanically stirring to obtain the nanometer essential oil antibacterial emulsion.

10. Use of the nano essential oil antibacterial emulsion according to any one of claims 1 to 8 in food or daily chemical products.

Technical Field

The invention belongs to the technical field of antibacterial agent preparation, and particularly relates to a dynamically crosslinked nano essential oil antibacterial emulsion, and a preparation method and application thereof.

Background

The plant essential oil has the defects of difficult water solubility, high volatility, poor stability and the like in the single use process, and the water solubility and the stability of the essential oil can be improved by utilizing the nano-emulsion technology, so that the effect aging of the essential oil emulsion is prolonged, and the application range of the essential oil emulsion is expanded. At present, the nano-emulsion technology is widely used for improving the effect of essential oil due to the advantages of low cost and easy preparation. The physical stability of the active substance can be improved by constructing the plant essential oil nanoemulsion, a slow release effect is achieved after embedding, the volatilization loss of the essential oil is reduced, and the effective components of the essential oil are reserved to the maximum extent; meanwhile, the use amount of the essential oil is reduced, so that the cost is reduced, and the adverse effect of the essential oil on the sensory characteristics can be minimized.

In the prior art, some emulsifiers are usually required to be added to maintain the stability of the emulsion when preparing the nano emulsion, in the preparation of food and drug emulsions, small molecule surfactants such as Tween 80 and the like are frequently used as synthetic emulsifiers, and phospholipids, proteins, polysaccharides and the like are frequently used as natural emulsifiers. These emulsifiers generally do not have bacteriostatic properties and do not form a synergistic effect with bacteriostatic essential oils. Many scholars try to prepare the essential oil nano-emulsion by compounding the emulsifier, and a multi-element emulsifier system endows the emulsion with more functions, such as changes of stability, releasing property, antibacterial property and the like. The preparation and characterization of Hou Ke flood (preparation and characterization of hydroxypropyl-beta-cyclodextrin/plant essential oil based antibacterial emulsion and antibacterial film, Master academic thesis of Nanjing finance university, Hou Ke flood, 2020) researches the influence of different concentrations and proportions of Tween 80 and hydroxypropyl-beta-cyclodextrin on the particle size, antibacterial activity, stability and essential oil release performance of cinnamon essential oil nano-emulsion, although the stability of the emulsion can be improved to a certain extent; but hydroxypropyl-beta-cyclodextrin is required to be used together with a conventional surfactant to maintain the emulsion stable, and the essential oil slow release cannot be realized.

Disclosure of Invention

Aiming at the problems that the existing plant essential oil nano antibacterial emulsion has poor stability, the antibacterial performance cannot be effectively improved, and effective slow release cannot be realized, the invention aims to provide the dynamically crosslinked nano essential oil antibacterial emulsion. The nano essential oil antibacterial emulsion comprises a specific surfactant and a specific cross-linking agent, so that the bacteriostatic property of the antibacterial essential oil emulsion can be effectively improved, and the dynamic release of the nano essential oil can be realized.

The invention also aims to provide a preparation method of the nano essential oil antibacterial emulsion.

The invention also aims to provide application of the nano essential oil antibacterial emulsion in food and daily chemical products.

In order to achieve the above object, the present invention provides the following technical solutions:

a dynamic cross-linked nano essential oil antibacterial emulsion is characterized in that the nano essential oil antibacterial emulsion comprises water, bacteriostatic essential oil, a surfactant and a cross-linking agent;

wherein the mass ratio of water, bacteriostatic essential oil and surfactant in the nano essential oil antibacterial emulsion is 100: 0.5-3: 0.2-2; the molar ratio of the cross-linking agent to the surfactant is 1: 3-6;

wherein the surfactant is beta-cyclodextrin modified epoxy propyl quaternary ammonium salt; the cross-linking agent is a molecule taking adamantane as an end cap, and the structural formula of the cross-linking agent is as follows:

wherein n is 400-1000, and n is a positive integer.

The prior art shows that the glycidyl quaternary ammonium salt has excellent antibacterial property and surface activity, and the glycidyl quaternary ammonium salt modified by beta-cyclodextrin also has surface activity. However, the modified glycidyl quaternary ammonium salt has long hydrophobic chain, is easy to generate inclusion effect and is difficult to exert the surface activity. Therefore, the invention utilizes the characteristic that beta-cyclodextrin and adamantane can form a stable complex, takes adamantane as a terminated guest molecule as a cross-linking agent, forms a three-dimensional network molecular structure with beta-cyclodextrin derivatives, and can also form guest competition with the long chain of epoxypropyl quaternary ammonium salt, thereby realizing the purposes of reducing the probability of wrapping the long chain and enhancing the molecular stability; meanwhile, the beta-cyclodextrin at one end of the surfactant can be complexed with the bacteriostatic essential oil, so that the aim of dynamically releasing the essential oil is fulfilled, and the action aging of the essential oil is prolonged.

In addition, the glycidyl quaternary ammonium salt surfactant has the bacteriostatic function characteristic, so that the bacteriostatic effect of the essential oil can be enhanced when the glycidyl quaternary ammonium salt surfactant is compounded with bacteriostatic essential oil for use, and the aim of expanding the application field of the essential oil is fulfilled.

The surfactant with antibacterial property is prepared, and can form a synergistic effect with the antibacterial essential oil, so that the bacteriostatic effect of the essential oil is improved; meanwhile, the beta-cyclodextrin cavity is complexed with the cross-linking agent, so that the prepared nano essential oil antibacterial emulsion has good stability and outstanding antibacterial effect, can realize slow release of effective antibacterial essential oil to a certain extent, and can be widely applied to the fields of food or daily chemicals and the like.

Preferably, the bacteriostatic essential oil is at least one of cinnamon essential oil or oregano essential oil.

Preferably, the glycidyl quaternary ammonium salt is N, N-3-dimethyl-1-glycidyl-dodecylammonium.

Preferably, the particle size of the nano essential oil antibacterial emulsion is 100-800 nm.

Preferably, the mass ratio of the water, the bacteriostatic essential oil and the surfactant in the nano essential oil antibacterial emulsion is 100: 1-2: 0.5-1.

Further preferably, the mass ratio of the water, the bacteriostatic essential oil and the surfactant in the nano essential oil antibacterial emulsion is 100:1: 0.5.

Preferably, the molar ratio of the cross-linking agent to the surfactant in the nano essential oil antibacterial emulsion is 1: 4-5.

Further preferably, the molar ratio of the cross-linking agent to the surfactant in the nano essential oil antibacterial emulsion is 1: 5.

Preferably, the preparation method of the surfactant comprises the following steps:

adding beta-cyclodextrin and epoxy propyl quaternary ammonium salt into alkali liquor, reacting for 18-24 h at 55-70 ℃, performing rotary evaporation, extraction, column chromatography and drying to obtain the surfactant;

wherein the molar ratio of the epoxy propyl quaternary ammonium salt to the beta-cyclodextrin is 1-2: 1.

Further preferably, the molar ratio of the glycidyl quaternary ammonium salt to the beta-cyclodextrin is 1.2: 1.

Further preferably, the lye is a NaOH solution.

Preferably, the preparation method of the epoxypropyl quaternary ammonium salt comprises the following steps:

mixing long-chain alkyl tertiary amine with epoxy chloropropane, reacting for 2-3 h at 60-70 ℃, recrystallizing for 3-4 times after the reaction is finished, and drying at 40-60 ℃ to obtain the epoxy propyl quaternary ammonium salt.

Further preferably, the long-chain alkyl tertiary amine is dodecyl tertiary amine, tetradecyl tertiary amine or hexadecyl tertiary amine.

Further preferably, the long-chain alkyl tertiary amine is dodecyl tertiary amine.

Further preferably, the volume ratio of the long-chain alkyl tertiary amine to the epichlorohydrin is 1-1.5: 1.

Preferably, the preparation method of the cross-linking agent comprises the following steps:

s1: reacting adamantane formic acid and thionyl chloride at 60-90 ℃, performing condensation reflux for 2-4 h, adding dichloromethane after the reaction is finished, performing rotary evaporation, and performing vacuum drying to prepare adamantane acyl chloride;

s2: dissolving PEG, triethylamine and adamantane acyl chloride in dichloromethane, reacting, purifying and drying to obtain the cross-linking agent.

Further preferably, the molar ratio of the adamantanecarboxylic acid to the thionyl chloride in S1 is 1:2 to 1: 5; in S2, the molar ratio of adamantane acyl chloride, PEG and triethylamine is 5-10: 1-2: 5-15.

The invention also provides a preparation method of the nano essential oil antibacterial emulsion, which comprises the following steps: mixing water, bacteriostatic essential oil, surfactant and cross-linking agent, and mechanically stirring to obtain the nanometer essential oil antibacterial emulsion.

The application of the nano essential oil antibacterial emulsion in food or daily chemical products is also within the protection scope of the invention.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a dynamic cross-linked nano essential oil antibacterial emulsion, which takes beta-cyclodextrin modified epoxy propyl quaternary ammonium salt as a surfactant and takes adamantane as a capped molecule as a cross-linking agent; the beta-cyclodextrin and the adamantane can form a stable complex, so that the cross-linking agent and the surfactant form a dynamically cross-linked three-dimensional network molecular structure, and can also form guest competition with the long chain of the glycidyl quaternary ammonium salt, thereby realizing the reduction of the probability of wrapping the long chain and the enhancement of the molecular stability; meanwhile, a beta-cyclodextrin group at one end of the surfactant can be complexed with the essential oil, so that the aim of dynamically releasing the essential oil is fulfilled. The prepared nano essential oil antibacterial emulsion has good stability and outstanding antibacterial effect, can realize effective slow release to a certain extent, and can be widely applied to the fields of food, daily chemicals and the like.

Drawings

FIG. 1 is an infrared image of N, N-3-dimethyl-1-epoxypropyl-dodecylammonium prepared in example 1;

FIG. 2 is an infrared image of the surfactant prepared in example 1;

FIG. 3 is a nuclear magnetic spectrum of the crosslinking agent Ad-PEG-Ad prepared in example 1;

FIG. 4 is a graph showing the stability of the nano essential oil antibacterial emulsions prepared in examples 1 and 3 to 4 after being stored at room temperature for 1 to 5 days;

FIG. 5 is a graph showing the stability of the nano essential oil antibacterial emulsions prepared in examples 1, 5 to 6 and comparative example 1 after being stored at room temperature for 1 to 5 days;

FIG. 6 is a graph showing the stability of the nano essential oil antibacterial emulsions prepared in examples 1, 7 to 8 and comparative example 2 after being stored at room temperature for 1 to 5 days;

FIG. 7 is a graph showing a distribution of particle diameters of the antibacterial emulsions prepared in example 1 and comparative example 2 after being stored at room temperature for 5 days;

fig. 8 is a distribution diagram of particle diameters of the antibacterial emulsions prepared in example 2 and comparative example 3 after being stored at room temperature for 5 days.

Detailed Description

The invention is further illustrated by the following examples. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like.

The examples and comparative examples of the invention provide a series of dynamically crosslinked nano essential oil antibacterial emulsions, which specifically comprise the following steps:

(1) preparation of Cross-linker adamantane-polyethylene glycol-adamantane (Ad-PEG-Ad)

S1: the appropriate amount of adamantanecarboxylic acid (18g, 180.24g/moL), thionyl chloride (50mL, 118.97g/moL) was weighed into a 150mL round-bottomed flask and condensed at 75 ℃ under reflux for 3 h. And then, carrying out rotary evaporation at the temperature of 45 ℃, removing most of solvent, adding dichloromethane, continuously carrying out rotary evaporation, repeating for 3-4 times, and drying in vacuum to obtain a white solid, namely adamantane acyl chloride, wherein the preparation reaction formula is as follows:

s2, weighing a proper amount of PEG (600) in a dry flask, adding a proper amount of triethylamine solution, and adding a proper amount of dichloromethane for dissolution; under the ice-bath condition, dropwise adding adamantane acyl chloride dissolved in dichloromethane; after the dropwise addition is finished, reacting for 24 hours at room temperature;

the purification process comprises the steps of carrying out suction filtration on the solution, removing triethylamine hydrochloride precipitate, adding dilute hydrochloric acid and sodium bicarbonate water solution for extraction for 3-4 times, washing with water to remove residual sodium bicarbonate, adding a proper amount of anhydrous magnesium sulfate, standing, filtering, and collecting concentrated filtrate. Then, carrying out column chromatography purification, wherein a developing agent is dichloromethane; the preparation reaction formula is as follows:

(2) preparation of beta-cyclodextrin modified epoxy propyl quaternary ammonium salt

S1: preparation and purification of N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium

15mL of tertiary dodecyl amine (213.4g/moL, 0.0137moL) was weighed into a round bottom flask, and 12mL of epichlorohydrin (92.52g/moL, 0.0357moL) was weighed into an isopiestic funnel. Slowly dropwise adding epoxy chloropropane at the temperature of 60 ℃, then keeping the temperature at 60 ℃, and carrying out condensation reflux for 2h, wherein the reaction equation is as follows:

after the reaction is finished, acetone is used for recrystallization for 4 times (dissolution at 45 ℃, cooling crystallization at room temperature and suction filtration), and the dosage is 20mL each time; and then drying in an oven at 40 ℃ to obtain the product which is colloidal and pure white in color.

S2 preparation and purification of beta-cyclodextrin modified N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium

To 50mL of a 3 wt% NaOH solution, an appropriate amount of beta-cyclodextrin was added, and the mixture was stirred at room temperature for 1 hour. Then slowly dripping N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium (dissolved in 20mL of isopropanol solution) into the system at 65 ℃, and condensing and refluxing for 24 hours; wherein, the mol ratio of N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium to beta cyclodextrin is 1.2:1, and the reaction equation is as follows:

the purification process is that the reaction solution is concentrated by rotary evaporation at 42 ℃, then chloroform is used for extracting for a plurality of times, finally column chromatography is carried out, and the developing agent system is isopropanol: water: ammonia 5:1:3, oven dried at 40 ℃.

(3) Preparation of nano essential oil antibacterial emulsion

Taking cinnamon essential oil and oregano essential oil as oil phases, taking the prepared beta-cyclodextrin modified N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium as a surfactant, taking Ad-PEG (600) -Ad as a cross-linking agent and taking deionized water as a water phase, mixing, and oscillating the mixed solution in a high-speed homogenizer for 6min at the rotating speed of 8000 r/min. After shaking, the mixture was stored at room temperature and the results were observed. Wherein the parameter usage of each component is shown in table 1.

TABLE 1 quantity parameters of each component in examples and comparative examples

In the above examples and comparative examples, cinnamon essential oil was used except that the bacteriostatic essential oil used in example 2 and comparative example 3 was oregano essential oil.

Performance testing

The antibacterial property and the particle size distribution were measured with respect to the antibacterial emulsions prepared in example 1 and comparative example 2.

(1) Determination of MIC value of antibacterial emulsion

And (3) researching the MIC value of the emulsion by adopting a trace broth dilution method to judge the antibacterial performance of the emulsion, wherein the strains are researched by taking staphylococcus aureus and pseudomonas aeruginosa as examples.

Preparation of S1 bacterial liquid: firstly, resuscitating bacteria by using a four-zone streaking method, and inoculating the bacteria onto a nutrient agar plate; after 24 hours of culture at 37 ℃, bacteria from which single colonies could be isolated were selected and inoculated into LB broth, followed by shake culture at 37 ℃ for 24 hours.

Then, the bacterial solution was quantitatively prepared. Centrifuging the bacterial liquid cultured with LB broth, changing the liquid to MH broth, measuring the dilution factor of the bacterial liquid by enzyme labeling method, and diluting with MH broth to 1.5 × 10⁸And C, after CFU/mL, the solution is ready for use.

Preparation of S2 antibacterial emulsion: the antibacterial emulsions prepared in examples 1-2 and comparative examples 2-3 were used, wherein the aqueous phase was sterile water, and the final emulsion was sterilized by filtration using a 0.22 μm filter.

Determination of S3 MIC: using the microdilution method, 100. mu.L of the medium was added to each well of a 96-well plate, 400. mu.L of the antibacterial emulsion prepared in example 1 was added to the 1 st well of the first column 3, and then the emulsion was 2-fold diluted. Adding the emulsion into the 1 st hole, fully blowing and beating (at least 3 times) by using a pipette gun to fully mix the emulsion with the culture medium, then adding 100 mu L of the emulsion into the 2 nd hole, fully blowing and beating again, repeating the process until the last 1 hole is reached, sucking out 100 mu L of the emulsion in the 7 th line and discarding, and then adding 100 mu L of the diluted bacterium liquid into each hole in the previous 3 rows.

The antibacterial emulsion prepared in comparative example 2 was added to columns 4-6 of the same 96-well plate and the experimental procedure was the same as above.

Wherein the mass contents of the antibacterial emulsion in the 1 st to 7 th holes are respectively 80 wt.%, 40 wt.%, 20 wt.%, 10 wt.%, 5 wt.%, 2.5 wt.% and 1.25 wt.%.

At the same time, 1 positive control (100. mu.L medium + 100. mu.L of culture broth) was performed on the 7 th column of the same plate, and 1 negative control (only 100. mu.L medium) was performed on the 8 th column of the same plate.

And finally, sealing the 96-well plate, putting the 96-well plate into a constant-temperature incubator at 37 ℃, culturing for 16-20h, and then putting the 96-well plate into an enzyme-labeling instrument for determining the OD 620nm value.

MIC values of example 2 and comparative example 3 were determined as above.

S4 dilution plate count: in order to further explore the actual bacteriostatic effect of the determined MIC value and verify the reliability of the MIC value, bacteria were counted on a 96-well plate in a mixed solution corresponding to 2MIC, MIC and 0.5 MIC.

Taking 100 mu L of mixed liquor corresponding to 2MIC, MIC and 0.5MIC on a 96-well plate, diluting by 105 times with sterilized PBS, taking 100 mu L of diluted liquor to a sterile culture dish, pouring a culture medium with proper temperature (about 46-50 ℃), inverting the culture medium after cooling the culture medium, culturing for 24h, observing the growth condition of bacteria, and counting the bacteria.

(2) Determination of particle size of nano essential oil antibacterial emulsion

The sample emulsions in example 1 and comparative example 2 were emulsions that had been left for 5 days and were still uniform in appearance.

The experimental equipment is a Brookwegian particle size analyzer, the measurement time is 5min, the test times are 5 times, the test temperature is 25 ℃, the test angle is 90 degrees, and the test wavelength is 660.0 nm.

Analysis of results

(1) Analysis of synthetic substances

From the IR spectrum of N, N-3-dimethyl-1-epoxypropyl-dodecylammonium in FIG. 1, 998.32cm^-1、949.19cm^-1、903.61cm^-1At 3 characteristic peaks of epoxy groups, respectively, 720.75cm^-1Is a long chain of methylene groups, i.e., the material contains more than 4 methylene groups connected, and the peak has a transmittance of 75%. Since this substance is highly hydrophilic, i.e., contains a large amount of bound water, 3358.91cm^-1Is the hydroxyl peak of water. 2922.04cm^-1、2852.72cm^-1And 1466.94cm^-1is-CH₂-a peak of flexural vibrations; 1377.37cm^-1Characteristic peak for methyl; and 1639.12cm^-1The peak at (A) is a skeleton of-C-N-. Thus, the material prepared is illustrated as N, N-3-dimethyl-1-epoxypropyl-dodecylammonium.

From the IR spectrum of the surfactant in FIG. 2, it is found that the peak intensity of the surfactant is 1032.65cm^-1The peak is the infrared absorption peak of the glycosidic bond on the beta-cyclodextrin and is 1652.81cm^-1The peak is the skeleton characteristic peak of nitrogen and carbon of the quaternary ammonium salt. In addition, characteristic peaks of methyl groups and methylene groups are also shown in the figure. Thus, it is illustrated thatThe obtained substance is N, N-3-dimethyl-1-epoxypropyl-dodecyl ammonium modified by beta-cyclodextrin.

From the nuclear magnetic spectrum of the crosslinking agent Ad-PEG-Ad in fig. 3, 1H NMR (400MHz, Chloroform-d) δ 4.17-4.10 (m,4H),3.58(s,48H),1.96(d, J ═ 17.0Hz,14H),1.85(dd, J ═ 18.3,2.7Hz,28H),1.66(d, J ═ 9.3Hz,28H) were known. FIG. 3 shows no characteristic peak at 4.50ppm, and around 4.13ppm, a characteristic peak appears, corresponding to-CH₂The characteristic peak of CO-indicates that the hydroxyl end of PEG completely participates in the reaction. In addition, 3 characteristic peaks of adamantane and characteristic peaks on the PEG long chain still exist in a nuclear magnetic diagram, and the respective hydrogen number ratio accords with the structure, which indicates that the target product Ad-PEG-Ad exists in the synthesized substance.

(2) Stability of nano essential oil antibacterial emulsion

As can be seen from fig. 4, in example 1, the emulsion was stable for 5 days at room temperature when the mass ratio of cinnamon essential oil to aqueous phase was 5:495, whereas when the mass ratio of cinnamon essential oil to aqueous phase was 10:490 and 15:485, the cinnamon essential oil was separated out after the emulsion was left for 1 day. Therefore, compared with the traditional Chinese medicine, the emulsion stability is better when the mass ratio of the cinnamon essential oil to the water phase is 5: 495.

As can be seen from fig. 5, when the mass ratio of the cinnamon essential oil to the water phase is 5:495, the emulsion can be stably placed for 5 days when the solid content of the surfactant in the system is 0.5 wt.%, and when the solid content is 1 wt.% and 0.25 wt.%, the essential oil is separated out after the emulsion is placed for 1 day, and the stability is poor. In addition, after the antibacterial emulsion in comparative example 1 is left for 3 days, a large amount of essential oil is separated out and floats on the water surface.

As can be seen from fig. 6, under room temperature conditions, the emulsion prepared with the mass ratio of cinnamon essential oil to deionized water of 5:495, the solid content of the surfactant of 0.5 wt.%, and the molar ratio of the cross-linking agent to the surfactant of 1:5 can be stably stored for 5 days. When the molar ratio of the cross-linking agent to the surfactant is 1:3 and 1:4, the emulsion is far less stable than the cinnamon essential oil emulsion with the molar ratio of the cross-linking agent to the surfactant being 1: 5.

(3) Bacteriostatic property of nano essential oil antibacterial emulsion

Tables 2 to 5 show the average absorbance values and the bacteriostatic ratios of the antibacterial emulsions prepared in examples 1 to 2 and comparative examples 2 to 3 at different dilution concentrations, respectively.

TABLE 2 average values of absorbance and inhibition rates for different dilution concentrations of the antibacterial emulsion in example 1

TABLE 3 average value of absorbance and bacteriostasis rate of antibacterial emulsion in different dilution concentrations in comparative example 2

TABLE 4 average values of absorbance and inhibition rates for different dilution concentrations of the antibacterial emulsion in example 2

TABLE 5 average value of absorbance and bacteriostasis rate of antibacterial emulsion at different dilution concentrations in comparative example 3

By comparing the data in tables 2 and 3, it can be found that in the nano cinnamon essential oil antibacterial emulsion system, when the emulsion occupancy is only 1.25 wt.%, the bacteriostasis rate can reach 70%; and under the condition of the same dilution concentration in the corresponding comparative example 2, the bacteriostasis rate of the emulsion system without the cross-linking agent is only 25.9478 percent. The data of the oregano essential oil in tables 4-5 show that the antibacterial performance of the essential oil emulsion containing the cross-linking agent is superior to that of the essential oil emulsion without the cross-linking agent.

(4) Nanometer essential oil antibacterial emulsion particle size

As can be seen from table 6 and fig. 7 to 8, the particle sizes of the 4 emulsions were all in accordance with the normal distribution, and were all nanoemulsions. The average particle size of the oregano essential oil emulsion system is larger than that of the cinnamon essential oil emulsion system. In addition, the average particle size of the cinnamon essential oil emulsion with the cross-linking agent (example 1) is smaller than the average particle size of the cinnamon essential oil emulsion without the cross-linking agent (comparative example 2); the average particle size of the oregano essential oil emulsion containing a cross-linking agent (example 2) was smaller than the average particle size of the oregano essential oil emulsion without a cross-linking agent (comparative example 3).

TABLE 6 particle size of antibacterial emulsion in example 1 and comparative example 2

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.