Alkylated lignin nanosphere-stabilized Pickering emulsion and preparation method and application thereof
By alkylating and modifying lignin and preparing nano-alkylated lignin spheres, the problems of oxidation and volatility of unsaturated aromatic aldehyde compounds in Pickering emulsion are solved, and stable Pickering emulsion and good antibacterial effects are achieved.
Patent Information
- Application Number
- CN202510135074.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-07
- Publication Date
- 2025-04-11
- Estimated Expiration
- 2045-02-07
AI Technical Summary
The failure to effectively stabilize unsaturated aromatic aldehyde compounds, such as cinnamaldehyde, as the oil phase of Pickering emulsion, leads to their oxidation and volatility, limiting their antibacterial applications.
By alkylating the lignin, the hydrophobic chains are introduced to improve its hydrophilic properties, and nano-alkylated lignin spheres are prepared by anti-solvent dialysis as a stabilizer to form a stable O/W type Pickering emulsion.
The stability of unsaturated aromatic aldehyde compounds was achieved, overcoming their easy oxidation and volatility problems, improving the stability of Pickering emulsion, and showing good antibacterial activity in the application of antibacterial agents.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of Pickering emulsions, and more specifically to an alkylated lignin nanosphere-stabilized Pickering emulsion and a preparation method and application thereof. Background Art
[0002] Pickering emulsion is an emulsion stabilized by solid particles located at the oil-water interface. Using solid particles as stabilizers, these particles can accumulate at the interface between two immiscible liquids, stabilize the droplets to prevent coalescence, and obtain a stable emulsion. Pickering emulsions have been widely used in food technology, cosmetics, photocatalysis, and drug delivery due to their low cost, good biocompatibility, excellent stability, and low toxicity.
[0003] Pickering emulsions can be divided into oil-in-water (O / W) Pickering emulsions and water-in-oil (W / O) Pickering emulsions. The specific type depends on the wettability of the solid particles at the oil-water interface: if one liquid wets the solid particles more than the other, the liquid with better wettability becomes the continuous phase and the other becomes the dispersed phase. Particles can only effectively act as stabilizers when their hydrophilicity and hydrophobicity are appropriate, because if the particles are too hydrophilic or too hydrophobic, the particles tend to remain dispersed in either phase. Biodegradable and biocompatible stabilizers of specific sizes at the micron or nanometer level and of natural origin are attracting more and more attention from scientific researchers. For example, starch, protein, nanocellulose, etc.
[0004] As the second most abundant biopolymer on earth after cellulose, lignin has many advantages, including wide sources, biodegradability, and non-toxicity. However, due to its variable chemical structure and different sources. In contrast to the irregular shapes and sizes of the original lignin powder, the existence form of lignin is controlled by lignin nanoparticles (LNPs), which have adjustable particle size and shape. The structurally stable lignin nanoparticles (LNPs) with large surface area and high surface activity can be used as an ideal stabilizer for Pickering emulsions. However, due to the imbalance between the hydrophilic and hydrophobic parts, we found that the Pickering emulsions stabilized by unmodified LNPs showed very limited stability. In order to improve the efficiency of LNPs as Pickering emulsion stabilizers, it has become a research direction to modify lignin to obtain lignin nanospheres with suitable hydrophilicity and hydrophobicity, thereby obtaining stable Pickering emulsions.
[0005] Cinnamaldehyde is an aldehyde organic compound. It is a hydrophobic aromatic aldehyde that exists in large quantities in plants such as cinnamon. It has strong antibacterial activity and can inhibit the growth of Gram-positive and Gram-negative bacteria. However, despite its excellent antibacterial potential, its scope in practical applications is subject to many restrictions. Cinnamaldehyde alone is easily oxidized, which will cause its antibacterial efficacy to decrease. If cinnamaldehyde is used as the oil phase of the Pickering emulsion, the presence of cinnamaldehyde can be stabilized. However, no suitable lignin nanoparticle stabilizer has been found in the current technology to form a stable Pickering emulsion with aldehyde organic compounds.
[0006] For example, patent CN118459796A proposes a method for preparing polymer microspheres using modified lignin as Pickering emulsion-stabilizing particles, wherein 3-chloro-2-hydroxypropylammonium chloride is reacted with lignin to obtain modified lignin, and the modified lignin is used as Pickering emulsion-stabilizing particles. Polymer microspheres are prepared using a Pickering emulsion system, but unsaturated aldehyde organic compounds are relatively active and easily react with surface modification groups. The modified lignin is not suitable for preparing Pickering emulsions containing unsaturated aldehyde organic compounds. Summary of the invention
[0007] The purpose of the present invention is to overcome the defects and shortcomings of the existing Pickering emulsion and provide a method for preparing a Pickering emulsion stabilized by alkylated lignin nanospheres. The obtained Pickering emulsion has good stability.
[0008] Another object of the present invention is to provide an alkylated lignin nanosphere.
[0009] Another object of the present invention is to provide the use of the Pickering emulsion stabilized by the alkylated lignin nanospheres in the preparation of an antibacterial agent.
[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:
[0011] The present invention provides a method for preparing a Pickering emulsion stabilized by alkylated lignin nanospheres, comprising the following steps:
[0012] Step S1, subjecting lignin to an alkylation reaction to obtain alkylated lignin;
[0013] Step S2, preparing nano-alkylated lignin balls by dialyzing the alkylated lignin through an anti-solvent to obtain a nano-alkylated lignin ball suspension;
[0014] Step S3, using the nano-alkylated lignin ball suspension as the water phase and the unsaturated aromatic aldehyde compound as the oil phase, mixing and ultrasonically emulsifying to obtain the Pickering emulsion prepared by the preparation method.
[0015] In the preparation method of the present invention, lignin is subjected to an alkylation reaction to introduce a hydrophobic chain, thereby improving the hydrophilic and hydrophobic properties of the lignin. After the alkylated modified lignin is subjected to anti-solvent dialysis to prepare nano-alkylated lignin balls, the alkylated lignin balls can be used as a stabilizer to enable the oil phase and the water phase of the unsaturated aromatic aldehyde compound to form a stable O / W type Pickering emulsion, thereby solving the problem that the unsaturated aromatic aldehyde compound is easily oxidized and volatilized.
[0016] In some embodiments, in step S1, the alkylation reaction step includes: uniformly mixing lignin, an alkaline substance, an iodine catalyst and water to form a mixed solution, adding a bromide-based alkylating agent and reacting at 60 to 100° C. for 2 to 8 hours to obtain alkylated lignin.
[0017] Optionally, the alkaline substance includes but is not limited to potassium hydroxide and / or sodium hydroxide.
[0018] Optionally, the iodine catalyst includes but is not limited to potassium iodide and / or sodium iodide.
[0019] Optionally, the bromide-based alkylating agent is a brominated alkane with a carbon chain length of 2-20, preferably a brominated alkane with a carbon chain length of 8-20; optionally, the brominated alkylating agent includes but is not limited to at least one of ethyl bromide, hexyl bromide, dodecane bromide or octadecane bromide.
[0020] Optionally, the mass ratio of the lignin to the bromide-based alkylating agent is 1:(0.2 ~ 1.5).
[0021] Optionally, the mass ratio of the lignin to the alkaline substance is 1: (0.1 ~ 0.2).
[0022] Optionally, the mass ratio of the catalyst to the bromide-based alkylating agent is 1:(20 ~ 150).
[0023] In some embodiments, in step S2, the anti-solvent dialysis step includes: dissolving the alkylated lignin in a γ-valerolactone aqueous solution and placing it in a dialysis bag, using water as an anti-solvent, immersing it in the anti-solvent for dialysis, and obtaining a nano-alkylated lignin ball suspension.
[0024] In this system, the principle of preparing lignin nanospheres is: after lignin is dissolved in a solution that can dissolve lignin, a large amount of another anti-solvent (such as water) that is not easily soluble in lignin is added through dialysis, thereby causing the macromolecules to aggregate and form a core structure, and then through direct collision and growth of the particles, the lignin forms a nanosphere structure to obtain nano-alkylated lignin spheres.
[0025] In some embodiments, the dialysis bag has a molecular weight cutoff of 100 Da to 1000 Da.
[0026] In some embodiments, the volume ratio of γ-valerolactone to water in the γ-valerolactone aqueous solution is 1:1 to 0.1.
[0027] In some embodiments, the concentration of the nano-alkylated lignin ball suspension is 1 to 5 mg / mL.
[0028] In some embodiments, in step S3, the unsaturated aromatic aldehyde compound is cinnamaldehyde or a cinnamaldehyde derivative in which one or more H is substituted by an acyl group, an amide group or a hydroxyl group. Cinnamaldehyde has strong antibacterial activity and can be used to prepare a Pickering emulsion with antibacterial effect.
[0029] In some embodiments, in step S3, the volume ratio of the unsaturated aromatic aldehyde compound to the Pickering emulsion is 10-50%.
[0030] In some embodiments, in step S3, the temperature of the ultrasonic emulsification is 15 to 40° C., the duration is 4 to 8 min, and the power is 100 to 150 W.
[0031] The invention protects a Pickering emulsion stabilized by alkylated lignin nanospheres, which is prepared by the preparation method of the Pickering emulsion stabilized by alkylated lignin nanospheres.
[0032] The invention protects the use of a Pickering emulsion stabilized by alkylated lignin nanospheres in the preparation of an antibacterial agent.
[0033] Compared with the prior art, the present invention has the following beneficial effects:
[0034] The invention provides a method for preparing a Pickering emulsion stabilized by alkylated lignin nanospheres. The method comprises the following steps: alkylating lignin to introduce hydrophobic chains, improving the hydrophilic and hydrophobic properties of the lignin; and subjecting the alkylated modified lignin to anti-solvent dialysis to prepare nano-alkylated lignin spheres. The nano-alkylated lignin spheres are used as stabilizers to enable an oil phase and a water phase of an unsaturated aromatic aldehyde compound to form a stable O / W Pickering emulsion, thereby solving the problem that the unsaturated aromatic aldehyde compound is easily oxidized and volatilized. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is a physical picture of the antibacterial Pickering emulsion prepared in Examples 1 to 3 of the present invention and Comparative Example 1.
[0036] Figure 2 Microscope photos (0 h) of the antibacterial Pickering emulsions prepared in Examples 1 to 3 and Comparative Example 1; wherein A is the sample of Comparative Example 1, B is the sample of Example 1, C is the sample of Example 2, and D is the sample of Example 3.
[0037] Figure 3 Microscope photos (24 h) of the antibacterial Pickering emulsions prepared in Examples 1 to 3 and Comparative Example 1; wherein A is the sample of Comparative Example 1, B is the sample of Example 1, C is the sample of Example 2, and D is the sample of Example 3.
[0038] Figure 4 The antibacterial Pickering emulsions prepared in Examples 1 to 3 and Comparative Example 1 were respectively effective against Gram-negative Escherichia coli ( E. coli ) and Gram-positive Staphylococcus aureus ( S. aureus ) of the cell activity results. DETAILED DESCRIPTION
[0039] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.
[0040] Aiming at the technical problem that the existing lignin cannot stabilize the Pickering emulsion well, the present invention proposes a method for preparing a Pickering emulsion stabilized by alkylated lignin nanospheres, wherein the alkylated modified lignin is subjected to anti-solvent dialysis to prepare nano-alkylated lignin spheres, and the nano-alkylated lignin spheres are used as stabilizers to stabilize organic aldehyde compounds, especially cinnamaldehyde with antibacterial effects, to form a stable Pickering emulsion, thereby overcoming the problem that cinnamaldehyde is easily oxidized and volatilized.
[0041] The present invention will be further explained and illustrated below in conjunction with specific embodiments.
[0042] Example 1
[0043] A method for preparing an antibacterial Pickering emulsion stabilized by alkylated lignin nanospheres comprises the following steps:
[0044] 1) Preparation of alkylated lignin: 10 g of alkali lignin was dissolved in 50 mL of potassium hydroxide solution (concentration of 5.6 wt %), 0.1 g of potassium iodide was added, and the mixture was evenly mixed to obtain a reaction mixture; after the mixture was heated to 60°C, 4 g of ethyl bromide was added, and the reaction was carried out for 2 h; after the reaction was completed, the mixture was cooled to room temperature, and then extracted, dialyzed, and dried to obtain alkylated lignin.
[0045] 2) Preparation of alkylated lignin nanospheres: 0.03 g of alkylated lignin was dissolved in 30 mL of γ-valerolactone aqueous solution, wherein the volume ratio of γ-valerolactone to water was 1:0.4, and the obtained lignin solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and immersed in water for dialysis to obtain a suspension of alkylated lignin nanospheres with a concentration of 1 mg / mL;
[0046] 3) Preparation of Pickering emulsion: 5 mL of the alkylated lignin nanosphere suspension was taken as the aqueous phase, and 5 mL of cinnamaldehyde was added as the oil phase. The suspension was ultrasonically crushed for 5 min at 25° C. and 150 W by an ultrasonic crusher to obtain an antibacterial Pickering emulsion.
[0047] Example 2
[0048] A method for preparing an antibacterial Pickering emulsion stabilized by alkylated lignin nanospheres comprises the following steps:
[0049] 1) Preparation of alkylated lignin: 10 g of alkali lignin was dissolved in 50 mL of potassium hydroxide solution (concentration of 5.6 wt %), 0.1 g of potassium iodide was added, and the mixture was evenly mixed to obtain a reaction mixture; after the mixture was heated to 100° C., 6 g of bromohexane was added and the mixture was reacted for 4 h; after the reaction was completed, the mixture was cooled to room temperature and then extracted, dialyzed, and dried to obtain alkylated lignin.
[0050] 2) Preparation of alkylated lignin nanospheres: 0.1 g of alkylated lignin was dissolved in 100 mL of γ-valerolactone aqueous solution, wherein the volume ratio of γ-valerolactone to water was 1:0.1, and the obtained lignin solution was placed in a dialysis bag and immersed in water for dialysis to obtain a suspension of alkylated lignin nanospheres with a concentration of 1 mg / mL;
[0051] 3) Preparation of Pickering emulsion: 6 mL of the alkylated lignin nanosphere suspension was taken as the aqueous phase, and 4 mL of cinnamaldehyde was added as the oil phase. The suspension was ultrasonically crushed at 25° C. and 150 W for 5 min, and the antibacterial Pickering emulsion was emulsified.
[0052] Example 3
[0053] A method for preparing an antibacterial Pickering emulsion stabilized by alkylated lignin nanospheres comprises the following steps:
[0054] 1) Preparation of alkylated lignin: 10 g of alkali lignin was dissolved in 50 mL of potassium hydroxide solution (concentration of 4 wt%), 0.1 g of potassium iodide was added, and the mixture was evenly mixed to obtain a reaction mixture; after the mixture was heated to 90°C, 9 g of dodecane bromide was added and the mixture was reacted for 6 h; after the reaction was completed, the mixture was cooled to room temperature and then extracted, dialyzed, and dried to obtain alkylated lignin.
[0055] 2) Preparation of alkylated lignin nanospheres: 0.1 g of alkylated lignin was dissolved in 100 mL of γ-valerolactone aqueous solution, wherein the volume ratio of γ-valerolactone to water was 1:0.4, and the obtained lignin solution was placed in a dialysis bag and immersed in water for dialysis to obtain a suspension of alkylated lignin nanospheres with a concentration of 1 mg / mL;
[0056] 3) Preparation of Pickering emulsion: 7 mL of the alkylated lignin nanosphere suspension was taken as the aqueous phase, and 3 mL of cinnamaldehyde was added as the oil phase. The suspension was ultrasonically crushed at 25° C. and 150 W for 5 min, and the antibacterial Pickering emulsion was emulsified.
[0057] Comparative Example 1
[0058] A method for preparing an antibacterial Pickering emulsion stabilized by lignin nanospheres, wherein the lignin is not subjected to alkylation modification treatment in this comparative example, and specifically comprises the following steps:
[0059] 1) Preparation of lignin nanospheres: 0.1 g of alkaline lignin was dissolved in 100 mL of γ-valerolactone aqueous solution, wherein the volume ratio of γ-valerolactone to water was 1:1, and the obtained lignin solution was placed in a dialysis bag and immersed in water for dialysis to obtain a lignin nanosphere suspension with a concentration of 1 mg / mL;
[0060] 2) Preparation of Pickering emulsion: 8 mL of the lignin nanosphere suspension was taken as the aqueous phase, and 2 mL of cinnamaldehyde was added as the oil phase. The suspension was ultrasonically crushed at 25° C. and 150 W for 5 min, and the antibacterial Pickering emulsion was emulsified.
[0061] Experimental Example 1
[0062] In this experimental example, the structure of the antibacterial Pickering emulsion stabilized by lignin nanospheres provided in Examples 1 to 3 and Comparative Example 1 was tested.
[0063] The antibacterial Pickering emulsions stabilized by lignin nanospheres prepared in Examples 1 to 3 and Comparative Example 1 were allowed to stand for 1 day. Figure 1 shown.
[0064] from Figure 1 It can be seen that the comparative example 1 ( Figure 1 A) of the Pickering emulsion showed obvious stratification; Examples 1 to 3 of the present invention ( Figure 1 The Pickering emulsions of B~D have a relatively stable emulsion state.
[0065] The Pickering emulsions of Examples 1 to 3 and Comparative Example 1 were observed under a microscope at 0 h and 24 h, respectively. The results are as follows: Figure 2~3 shown.
[0066] The results show that the droplet size in the Pickering emulsion stabilized by the modified alkylated lignin nanospheres of the present invention is relatively uniform, and the size gradually decreases with the increase of the alkylated chain length.
[0067] Experimental Example 2
[0068] In this example, the alkylated lignin nanosphere suspension prepared in Example 3 and the Pickering emulsion were used to isolate Gram-negative Escherichia coli ( E. coli ), Gram-positive Staphylococcus aureus ( S. aureus ) for antimicrobial activity.
[0069] Experimental method: Lignin nanosphere suspension (0.21 mg / mL), cinnamaldehyde (0.5 mg / mL) and Pickering emulsion (0.71 mg / mL) were mixed with 10 6 After incubating the CFU / mL bacterial suspension in a 37°C incubator for 4 hours, 100 µL of the bacterial suspension was applied to a nutrient agar plate and incubated at 37°C for 24 hours, and the number of colonies was recorded. The bactericidal rate of each sample was calculated by comparing the number of live colonies and the number of live colonies of the sample, and the comparison of the antibacterial activity of each sample was obtained. The results are shown in Figure 4 shown.
[0070] from Figure 4It can be seen that the lignin nanosphere suspension is basically the same as the blank control, indicating that the lignin nanosphere has no antibacterial effect; and the antibacterial effect is not ideal when cinnamaldehyde is used alone, because cinnamaldehyde is easily oxidized, which will cause its antibacterial efficacy to decrease. The antibacterial Pickering emulsion stabilized by alkylated lignin nanospheres provided by the present invention has good antibacterial activity against Gram-negative Escherichia coli (E.coli) and Gram-positive Staphylococcus aureus (S.aureus).
[0071] The above embodiments of the invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.
Claims
1. A method for preparing a Pickering emulsion stabilized by alkylated lignin nanospheres, characterized in that: The following steps are involved: Step S1, subjecting lignin to an alkylation reaction to obtain alkylated lignin; Step S2, preparing nano-alkylated lignin balls by dialyzing the alkylated lignin through an anti-solvent to obtain a nano-alkylated lignin ball suspension; Step S3, using the nano-alkylated lignin ball suspension as the water phase and the unsaturated aromatic aldehyde compound as the oil phase, mixing and ultrasonically emulsifying to obtain a Pickering emulsion.
2. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 1, characterized in that: In step S1, the alkylation reaction step includes: mixing lignin, alkaline substances, iodine catalysts and water to form a mixed solution, adding a bromide-based alkylating agent to react at 60 to 100° C. for 2 to 8 hours to obtain alkylated lignin.
3. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 2, characterized in that: The mass ratio of the lignin to the bromide-based alkylating agent is 1:(0.2-1.5).
4. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 2, characterized in that: The bromide-based alkylating agent is at least one of ethyl bromide, hexyl bromide, dodecane bromide or octadecane bromide.
5. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 1, characterized in that: In step S2, the anti-solvent dialysis step comprises: dissolving the alkylated lignin in a γ-valerolactone aqueous solution and placing it in a dialysis bag, using water as an anti-solvent, immersing it in the anti-solvent for dialysis, and obtaining a nano-alkylated lignin ball suspension.
6. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 1, characterized in that: The concentration of the nano-alkylated lignin ball suspension is 1 to 5 mg / mL.
7. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 1, characterized in that: In step S3, the unsaturated aromatic aldehyde compound is cinnamaldehyde.
8. The method for preparing the Pickering emulsion stabilized by alkylated lignin nanospheres according to claim 1, characterized in that: In step S3, the volume ratio of the unsaturated aromatic aldehyde compound to the Pickering emulsion is 10-50%.
9. A Pickering emulsion stabilized by alkylated lignin nanospheres, characterized in that: The method is prepared by the preparation method of the Pickering emulsion stabilized by the alkylated lignin nanospheres according to any one of claims 1 to 8.
10. Use of the Pickering emulsion stabilized by the alkylated lignin nanospheres according to claim 9 in the preparation of an antibacterial agent.
Citation Information
Patent Citations
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