Preparation method of bishell polyurea-chitosan microcapsules for pH-responsive release of antibacterial drugs

Abstract

The invention discloses a method for preparing a bishell polyurea-chitosan microcapsule capable of releasing an antibacterial drug in a pH-responsive manner. The method comprises the following steps: firstly, preparing a drug-coated polyurea core material by an interfacial polymerization method; then coating the prepared single-layer microcapsule with a diphenol-modified chitosan layer; the invention prepares polyurea microcapsules with weak chemical bonds for sustained-release of the drug, and then coating the outer layer with a natural, harmless, modified chitosan layer that responds to certain pH conditions, so as to regulate the slow release of the drug under certain pH conditions; the invention has simple preparation steps, readily available materials, and the prepared microcapsules have good drug release behavior and good antibacterial properties.

Description

Technical Field

[0001] The present invention relates to a method for preparing a double-layer microcapsule, in particular to a method for preparing a double-shell polyurea-chitosan microcapsule capable of releasing antibacterial drugs in a pH-responsive manner. The microcapsule has the ability to slowly release drugs and has good antibacterial properties. Background Art

[0002] Bacterial infections are a serious global challenge, threatening public health and imposing a heavy economic burden. The skin is the body's largest, multilayered organ, and microbial infections can significantly prolong the healing process. The widespread and extensive use of antibiotics over a long period of time has inevitably led to the emergence of drug resistance. Therefore, the development of antibiotic-free, multifunctional wound dressings for the treatment of bacterial infections is crucial.

[0003] Currently, a variety of approaches have been developed to promote the healing of infected wounds, primarily including peptides, antimicrobial drugs, stem cell therapy, nanofiber dressings, and hydrogels. Microencapsulation technology involves encapsulating small bioactive particles within a wall composed of a heterogeneous or homogenous polymer matrix, forming a complex known as a microcapsule. This technology offers the advantage of controlling the release point or release parameters, providing a controlled-release system for the active ingredient. Microencapsulating small molecule drugs as the core material can significantly inhibit their rapid diffusion and improve their long-term storage performance. Polyurea is widely used in microencapsulation due to its excellent film-forming properties and high chemical stability. However, existing preparation methods yield microcapsules with suboptimal size and release performance. The release performance of microcapsules under certain conditions needs to be further improved. Studies have shown that double-layer microcapsules can effectively enhance the sustained- and controlled-release properties of microcapsules and provide excellent protection for the encapsulated substance. The natural organic compound chitosan (CS) has attracted attention due to its unique biodegradability, biocompatibility, nontoxicity, and antimicrobial properties. Summary of the Invention

[0004] The present invention aims to provide a method for preparing bishell polyurea-chitosan microcapsules for pH-responsive drug release with controlled conditions. This method, with simple reaction conditions and preparation steps, involves coating a chitosan layer on the outer layer of low-cost drug-containing polyurea microcapsules. Through the interaction between thiourea bonds and drug molecules and the pH responsiveness of the modified chitosan, the prepared microcapsules exhibit conditional release and excellent antibacterial properties.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing a birefringent polyurea-chitosan microcapsule for pH-responsive release of antibacterial drugs, wherein the method first prepares a polyurea microcapsule coated with a drug, and then coats a diphenol-modified chitosan layer on the outside. 3+Cross-linking allows the outer layer of the microcapsule to control the slow release of drugs under certain pH conditions.

[0007] Specifically, the method includes the following steps:

[0008] (1) The drug, isocyanate and organic solvent are mixed as an oil phase; the amino monomer is dispersed in water as an aqueous phase; the oil phase and the aqueous phase are mixed at a stirring speed of 800-1200 rpm, and then an aqueous solution of polyvinyl alcohol is added for emulsification for 5 minutes, and a catalyst dibutyltin dilaurate is added, followed by reaction at 25-80°C and a stirring speed of 200-500 rpm for 2-6 hours to obtain a solution of drug-coated polyurea microcapsules;

[0009] The drug is one or two of curcumin, ciprofloxacin, and chlorhexidine;

[0010] The isocyanate is one or two of p-phenylene diisocyanate, m-xylylene diisocyanate, and toluene diisocyanate;

[0011] The organic solvent is one or two of methyl laurate, ethyl acetate, chlorobenzene, cyclohexanone, and butyl acetate;

[0012] In the oil phase, the concentration of the drug is 0.009-0.1 g / mL, and the concentration of the isocyanate is 0.1 g / mL;

[0013] The amino monomer is one or both of m-phenylenediamine and tetraethylenepentamine;

[0014] In the aqueous phase, the concentration of the amino monomer is 0.01-0.02 g / mL;

[0015] The concentration of the polyvinyl alcohol aqueous solution is 0.006 g / mL;

[0016] The preferred volume ratio of the oil phase to the water phase, the aqueous solution of polyvinyl alcohol, and the catalyst dibutyltin dilaurate is 1:4:6.6:0.03;

[0017] (2) dissolving chitosan in an aqueous solution of acetic acid to obtain a chitosan solution; dissolving 2,4-dihydroxybenzaldehyde in ethanol to obtain a 2,4-dihydroxybenzaldehyde solution; mixing the 2,4-dihydroxybenzaldehyde solution with the chitosan solution, reacting at 40-60° C. for 1-3 hours, separating unreacted substances with a dialysis bag, and freeze-drying to obtain 2,4-dihydroxybenzaldehyde-modified chitosan; dispersing the 2,4-dihydroxybenzaldehyde-modified chitosan in deionized water, mixing it evenly with a ferric chloride trihydrate solution, and then mixing it with the solution of the drug-coated polyurea microcapsules obtained in step (1), stirring at 30-60° C. for 1-2 hours, adding a crosslinking agent, glutaraldehyde, stirring for 1-2 hours, and then centrifuging and washing to obtain the double-shelled polyurea-chitosan microcapsules;

[0018] The mass fraction of the aqueous solution of acetic acid is 1-2%;

[0019] The mass ratio of the 2,4-dihydroxybenzaldehyde to chitosan is 1:5-10;

[0020] The mass ratio of the ferric chloride trihydrate to the modified chitosan is 1:5-20;

[0021] Preferably, the volume ratio of the dispersion obtained by dispersing the modified chitosan in deionized water, the solution of the drug-coated polyurea microcapsules obtained in step (1), and the cross-linking agent glutaraldehyde is 160:350:1.

[0022] The beneficial effects of the present invention are:

[0023] The invention discloses a method for preparing a double-shelled polyurea-chitosan microcapsule for releasing antibacterial drugs in a pH-responsive manner. Firstly, polyurea microcapsules coated with drugs are prepared by interfacial polymerization, and a cross-linked diphenol-modified chitosan layer is coated on the outside of the prepared single-layer microcapsule.

[0024] This invention prepares polyurea microcapsules with weak chemical bonds for sustained drug release, then coats them with a natural, harmless, pH-responsive chitosan layer to regulate the slow release of drugs under certain conditions. The preparation process is simple, the materials are readily available, and the resulting microcapsules exhibit excellent sustained drug release and antibacterial properties. DETAILED DESCRIPTION

[0025] The present invention is further described below by means of specific examples, but the protection scope of the present invention is not limited thereto.

[0026] Example 1:

[0027] A uniform oil phase solution was prepared by mixing 0.08 g of curcumin, 0.06 g of ciprofloxacin, and 15 mL of butyl acetate solution of 1.5 g of toluene diisocyanate; 0.8 g of tetraethylene pentamine was dispersed in 60 mL of aqueous solution; 0.6 g of polyvinyl alcohol particles were dissolved in 100 mL of aqueous solution at 80°C; the oil phase solution was dripped into the tetraethylene pentamine aqueous solution at a uniform speed using a peristaltic pump, and then the polyvinyl alcohol aqueous solution was added under stirring at 800 rpm / min; after emulsification for 5 minutes, 500 microliters of dibutyltin dilaurate was added, followed by reaction at 50°C and stirring at 300 rpm for 3 hours to obtain a microcapsule solution.

[0028] Dissolve 2g of chitosan in 100ml of 1wt% acetic acid and stir thoroughly for 2h to obtain a transparent chitosan solution. Dissolve 0.4g of 2,4-dihydroxybenzaldehyde in 20ml of ethanol, mix thoroughly with the chitosan solution, and heat at 50°C for 2h. Unreacted material is separated using a dialysis bag (molecular weight cut-off = 35,000Da) and freeze-dried. Disperse 1g of 2,4-dihydroxybenzaldehyde-modified chitosan in 80ml of aqueous solution and mix thoroughly with 0.1g of ferric chloride in 10ml of aqueous solution. Add the monolayer microcapsule solution to this mixture and stir at 50°C for 1h. Then, add a mixture of 0.5ml of glutaraldehyde and 2ml of water dropwise and stir for 1h to obtain double-shelled microcapsules through a crosslinking reaction. Finally, wash the mixture by centrifugation with an alcohol-water solution.

[0029] 2mg microcapsules were used for 10 5 In the antibacterial test of CFU / mL Escherichia coli and Staphylococcus aureus, the inhibition zones were 10.1 mm and 15.3 mm, respectively. The cumulative release of the drug reached 67% after 6 hours under the condition of pH = 5.5.

[0030] Example 2:

[0031] A uniform oil phase solution was prepared by dispersing 0.08 g of curcumin, 0.06 g of ciprofloxacin, and 1.5 g of toluene diisocyanate in 5 mL of methyl laurate and 10 mL of ethyl acetate; 0.8 g of tetraethylene pentamine was dispersed in 60 mL of aqueous solution; 0.6 g of polyvinyl alcohol particles were dissolved in 100 mL of aqueous solution at 80°C; the oil phase solution was dripped into the tetraethylene pentamine aqueous solution at a uniform speed through a peristaltic pump, and then the polyvinyl alcohol aqueous solution was added under stirring at 800 rpm / min; after emulsification for 5 minutes, 500 microliters of dibutyltin dilaurate was added, followed by reaction at 70°C and stirring at 300 rpm for 3 hours to obtain a microcapsule solution.

[0032] Dissolve 2g of chitosan in 100ml of 1wt% acetic acid and stir thoroughly for 2h to obtain a transparent chitosan solution. Dissolve 0.4g of 2,4-dihydroxybenzaldehyde in 20ml of ethanol, mix thoroughly with the chitosan solution, and heat at 50°C for 2h. Unreacted material is separated using a dialysis bag (molecular weight cut-off = 35,000Da) and freeze-dried. Disperse 1g of 2,4-dihydroxybenzaldehyde-modified chitosan in 80ml of aqueous solution and mix thoroughly with 0.1g of ferric chloride in 10ml of aqueous solution. Add the monolayer microcapsule solution to this mixture and stir at 50°C for 1h. Then, add a mixture of 0.5ml of glutaraldehyde and 2ml of water dropwise and stir for 1h to obtain double-shelled microcapsules through a crosslinking reaction. Finally, wash the mixture by centrifugation with an alcohol-water solution.

[0033] 2mg microcapsules were used for 105 In the antibacterial test of CFU / mL Escherichia coli and Staphylococcus aureus, the inhibition zones were 11.2 mm and 16.7 mm respectively after 2 days. At pH = 5.5, the cumulative drug release reached 68.4% after 6 hours.

[0034] Example 3:

[0035] A uniform oil phase solution was prepared by mixing 0.08 g of curcumin, 0.06 g of chlorhexidine, and 15 mL of butyl acetate solution of 1.5 g of toluene diisocyanate; 0.8 g of tetraethylene pentamine was dispersed in 60 mL of aqueous solution; 0.6 g of polyvinyl alcohol particles were dissolved in 100 mL of aqueous solution at 80°C; the oil phase solution was dripped into the tetraethylene pentamine aqueous solution at a uniform speed through a peristaltic pump, and then the polyvinyl alcohol aqueous solution was added under stirring at 800 rpm / min; after emulsification for 5 minutes, 500 microliters of dibutyltin dilaurate was added, followed by reaction at 50°C and stirring at 300 rpm for 3 hours to obtain a microcapsule solution.

[0036] Dissolve 2g of chitosan in 100ml of 1wt% acetic acid and stir thoroughly for 2h to obtain a transparent chitosan solution. Dissolve 0.4g of 2,4-dihydroxybenzaldehyde in 20ml of ethanol, mix thoroughly with the chitosan solution, and heat at 50°C for 2h. Unreacted material is separated using a dialysis bag (molecular weight cut-off = 35,000Da) and freeze-dried. Disperse 1g of 2,4-dihydroxybenzaldehyde-modified chitosan in 80ml of aqueous solution and mix thoroughly with 0.1g of ferric chloride in 10ml of aqueous solution. Add the above-mentioned single-layer microcapsule solution to this mixture and stir at 60°C for 1h. A mixture of 0.5ml of glutaraldehyde and 2ml of water is then added dropwise and stirred for 1h to produce double-shelled microcapsules through a crosslinking reaction. Finally, wash the mixture with an alcohol-water solution by centrifugation.

[0037] 2mg microcapsules were used for 10 5 In the antibacterial test of CFU / mL Escherichia coli and Staphylococcus aureus, the inhibition zones were 10.4 mm and 16.9 mm respectively after 2 days, and the cumulative drug release reached 69.7% after 6 hours under the condition of pH = 5.5.

[0038] Example 4:

[0039] A uniform oil phase solution was prepared by mixing 1.5 g of curcumin and 15 mL of butyl acetate solution of 1.5 g of toluene diisocyanate; 0.8 g of m-phenylenediamine was dispersed in 60 mL of aqueous solution; 0.6 g of polyvinyl alcohol particles was dissolved in 100 mL of aqueous solution at 80°C; the oil phase solution was dripped into the tetraethylenepentamine aqueous solution at a uniform speed through a peristaltic pump, and then the polyvinyl alcohol aqueous solution was added under stirring at 800 rpm / min; after emulsification for 5 minutes, 500 microliters of dibutyltin dilaurate was added, followed by reaction at 50°C and stirring at 300 rpm for 3 hours to obtain a microcapsule solution.

[0040] Dissolve 2g of chitosan in 100ml of 1wt% acetic acid and stir thoroughly for 2h to obtain a transparent chitosan solution. Dissolve 0.4g of 2,4-dihydroxybenzaldehyde in 20ml of ethanol, mix thoroughly with the chitosan solution, and heat at 50°C for 2h. Unreacted material is separated using a dialysis bag (molecular weight cut-off = 35,000Da) and freeze-dried. Disperse 1g of 2,4-dihydroxybenzaldehyde-modified chitosan in 80ml of aqueous solution and mix thoroughly with 0.1g of ferric chloride in 10ml of aqueous solution. Add the monolayer microcapsule solution to this mixture and stir at 50°C for 1h. Then, add a mixture of 0.5ml of glutaraldehyde and 2ml of water dropwise and stir for 1h to obtain double-shelled microcapsules through a crosslinking reaction. Finally, wash the mixture by centrifugation with an alcohol-water solution.

[0041] 2mg microcapsules were used for 10 5 In the antibacterial test of CFU / mL Escherichia coli and Staphylococcus aureus, the inhibition zones were 8.2 mm and 14.7 mm respectively after 2 days, and the cumulative drug release reached 63.5% after 6 hours under the condition of pH = 5.5.

Claims

1. A method for preparing a pH-responsive bishell polyurea-chitosan microcapsule for releasing antibacterial drugs, characterized in that: The following steps are involved: (1) The drug, isocyanate and organic solvent are mixed as an oil phase; the amino monomer is dispersed in water as an aqueous phase; the oil phase and the aqueous phase are mixed at a stirring speed of 800-1200 rpm, and then an aqueous solution of polyvinyl alcohol is added for emulsification for 5 minutes, and a catalyst dibutyltin dilaurate is added, followed by reaction at 25-80°C and a stirring speed of 200-500 rpm for 2-6 hours to obtain a solution of drug-coated polyurea microcapsules; The drug is one or two of curcumin, ciprofloxacin, and chlorhexidine; The isocyanate is one or two of p-phenylene diisocyanate, m-xylylene diisocyanate, and toluene diisocyanate; The organic solvent is one or two of methyl laurate, ethyl acetate, chlorobenzene, cyclohexanone, and butyl acetate; The amino monomer is one or both of m-phenylenediamine and tetraethylenepentamine; (2) dissolving chitosan in an aqueous solution of acetic acid to obtain a chitosan solution; dissolving 2,4-dihydroxybenzaldehyde in ethanol to obtain a 2,4-dihydroxybenzaldehyde solution; mixing the 2,4-dihydroxybenzaldehyde solution with the chitosan solution, reacting at 40-60° C. for 1-3 hours, separating unreacted substances with a dialysis bag, and freeze-drying to obtain 2,4-dihydroxybenzaldehyde-modified chitosan; dispersing the 2,4-dihydroxybenzaldehyde-modified chitosan in deionized water, mixing it evenly with a ferric chloride trihydrate solution, and then mixing it with the solution of the drug-coated polyurea microcapsules obtained in step (1), stirring at 30-60° C. for 1-2 hours, adding a crosslinking agent, glutaraldehyde, stirring for 1-2 hours, and then centrifuging and washing to obtain the double-shelled polyurea-chitosan microcapsules.

2. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In the oil phase of step (1), the concentration of the drug is 0.009-0.1 g / mL, and the concentration of the isocyanate is 0.1 g / mL.

3. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In the aqueous phase of step (1), the concentration of the amino monomer is 0.01-0.02 g / mL.

4. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: The concentration of the aqueous solution of polyvinyl alcohol in step (1) is 0.006 g / mL.

5. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In step (1), the volume ratio of the oil phase to the water phase, the aqueous solution of polyvinyl alcohol, and the catalyst dibutyltin dilaurate is 1:4:6.6:0.

03.

6. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In step (2), the concentration of the aqueous solution of acetic acid is 1-2 wt %.

7. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In step (2), the mass ratio of 2,4-dihydroxybenzaldehyde to chitosan is 1:5-10.

8. The method for preparing the pH-responsive bishell polyurea-chitosan microcapsules for releasing antibacterial drugs according to claim 1, wherein: In step (2), the mass ratio of ferric chloride trihydrate to modified chitosan is 1:5-20.

9. The method for preparing the pH-responsive antibacterial drug-releasing bishell polyurea-chitosan microcapsules according to claim 1, wherein: In step (2), the volume ratio of the dispersion obtained by dispersing the modified chitosan in deionized water, the solution of the drug-coated polyurea microcapsules obtained in step (1), and the cross-linking agent glutaraldehyde is 160:350:1.