A pH-responsive star polymer micelle and a preparation method and application thereof

Abstract

The application relates to the technical field of polymer micelles, in particular to a pH response star polymer micelle and a preparation method and application thereof. The pH response star polymer micelle takes pentaerythritol as a core, and other block structures include polyethylene glycol monomethyl ether, a dynamic imine bond, gamma-amino-epsilon-caprolactone and epsilon-caprolactone. After loading an anticancer drug doxorubicin, the polymer micelle can stably exist in a neutral environment of human normal tissues, and can control the release of the drug in a slightly acidic environment of tumor cells.

Description

Technical Field

[0001] This invention relates to the field of polymer micelle technology, and in particular to a pH-responsive star-shaped polymer micelle, its preparation method, and its application. Background Technology

[0002] Cancer poses a serious threat to human health and is one of the leading causes of death. Studies have found that the microenvironment of tumor cells differs significantly from that of normal cells; for example, the pH in tumor cells is lower than that in normal cells, ranging from 5.0 to 6.0, while the pH in normal cells is 7.4. Furthermore, polyethylene glycol possesses excellent properties such as being non-toxic, non-antigenic, and highly biocompatible. These two characteristics provide a theoretical basis for researchers to construct drug carriers for cancer treatment.

[0003] Micelles possess a natural advantage in loading anticancer drugs. Composed of amphiphilic polymers, polymer micelles spontaneously assemble into a shell-core structure with a hydrophilic exterior and a hydrophobic interior in an aqueous environment. The hydrophobic blocks encapsulate poorly soluble drugs, releasing them at the target site; while the hydrophilic blocks encapsulate the hydrophobic core, reducing the overall interaction between the drug-loaded micelle and the bloodstream, thus improving drug targeting and in vivo bioavailability. By leveraging the characteristics of these two blocks to design responsive polymer micelles, such as by introducing pH-responsive blocks or dynamic imine bonds, targeted delivery of anticancer drugs can be achieved while ensuring the stable existence of the drug-loaded micelles in the bloodstream, releasing drugs at tumor cells. Although various nanopolymer micelles have made significant progress in anticancer drug delivery research, drug-loaded micelles still suffer from slow and incomplete drug release in the later stages of drug delivery. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the shortcomings of the prior art by providing a pH-responsive star polymer micelle that can efficiently control the release of anticancer drugs.

[0005] The second objective of this invention is to provide a method for preparing pH-responsive star polymer micelles.

[0006] The third objective of this invention is to provide an application of pH-responsive star polymer micelles.

[0007] To achieve one of the above objectives, the present invention provides the following technical solution:

[0008] The polymer in the polymer micelles has the following structural formula:

[0009] Where x = 5 to 30, y = 1 to 6, and m = 1 to 2.

[0010]

[0011] Preferably, the number-average molecular weight of the pH-responsive star polymer micelles is 11,500 to 35,700 g / mol.

[0012] This invention provides a beneficial effect of pH-responsive star polymer micelles:

[0013] This invention discloses a pH-responsive star-shaped polymer micelle, the structure of which includes pentaerythritol, polyethylene glycol monomethyl ether, γ-amino-ε-caprolactone, ε-caprolactone, and dynamic imine bonds. The polyethylene glycol monomethyl ether is a hydrophilic block with good water solubility, which prolongs the micelle's circulation time in a normal blood environment. The ε-caprolactone is a hydrophobic block, thereby improving the micelle's drug loading capacity for hydrophobic drugs. The dynamic imine bonds and the primary amino groups in γ-amino-ε-caprolactone act as pH-responsive groups. Under the slightly acidic conditions of tumor tissue, the imine bonds can hydrolyze and break, allowing the micelles to gradually remove the hydrophilic protective shell of polyethylene glycol monomethyl ether, making it easier to enter tumor cells and partially release the drug. Simultaneously, the primary amino groups in γ-amino-ε-caprolactone, copolymerized with the hydrophobic core, undergo protonation, gradually changing from completely hydrophobic to partially hydrophilic, causing the hydrophobic core to swell and further releasing the drug loaded inside the hydrophobic core, resulting in more complete drug release.

[0014] The pH-responsive star-shaped polymer micelles provided by this invention can exist stably in the microenvironment of normal cells. In the acidic or slightly acidic environment of tumor cells, they can release drugs slowly and completely. Furthermore, polyethylene glycol has excellent properties, such as high biocompatibility, non-toxicity, and low susceptibility to triggering immune responses, which effectively improves the drug-controlled release performance of polymer drug-loaded micelles.

[0015] To achieve the second objective mentioned above, the present invention provides the following technical solution:

[0016] A method for preparing pH-responsive star-shaped polymer micelles is provided, comprising the following steps:

[0017] After mixing polyethylene glycol monomethyl ether, 4-carboxybenzaldehyde, dehydrating agent, solvent and first catalyst, the mixture was evacuated and purged with nitrogen three times, and stirred at room temperature to carry out esterification reaction to obtain aldehyde-modified polyethylene glycol.

[0018] Under an argon atmosphere, pentaerythritol, ε-caprolactone, γ-(tert-butyl carbamate)-ε-caprolactone, solvent, and a second catalyst were mixed and subjected to a ring-opening polymerization reaction to obtain star-shaped polymer molecules.

[0019] The star-shaped polymer molecules were dissolved in dichloromethane with trifluoroacetic acid and then stirred to obtain a pH-responsive star-shaped polymer.

[0020] Under a nitrogen atmosphere, the pH-responsive star polymer and the aldehyde-modified polyethylene glycol obtained in step 1 were dissolved in dimethylformamide and subjected to a Schiff base reaction to obtain a pH-responsive star amphiphilic polymer.

[0021] The pH-responsive star-shaped amphiphilic polymer was dialyzed to obtain pH-responsive star-shaped polymer micelles.

[0022] The dehydrating agent is dicyclohexylcarbodiimide, the first catalyst is dimethylaminopyridine, the solvent is dichloromethane or dimethylformamide, and the esterification reaction time is 24 h;

[0023] In preparing the star-shaped amphiphilic polymer, the solvent is toluene, the second catalyst is stannous isooctanoate, and the ring-opening polymerization reaction is carried out at a temperature of 130°C for 24 hours.

[0024] The Schiff base reaction time was 48 hours.

[0025] Preferably, in step 4, after the Schiele reaction, the reaction solution is further further precipitated by passing the reaction solution through a needle filter to remove anhydrous sodium sulfate and then adding it dropwise into anhydrous diethyl ether.

[0026] Preferably, the aldehyde-modified polyethylene glycol comprises the following raw materials in parts by weight: 2-4 parts by weight of polyethylene glycol monomethyl ether, 0.55-1.22 parts by weight of 4-carboxybenzaldehyde, 0.22-0.41 parts by weight of dicyclohexylcarbodiimide, and 0.15-0.27 parts by weight of dimethylaminopyridine.

[0027] Preferably, before obtaining aldehyde-modified polyethylene glycol, the process further includes: concentration, precipitation, filtration, and drying. The precipitation is achieved by dissolving the concentrated product in a small amount of dichloromethane and then transferring this solution into 10 times its volume of cold diethyl ether for precipitation.

[0028] Preferably, the pH-responsive star polymer comprises the following raw materials in parts by weight: 0.056–0.0681 parts pentaerythritol, 3.56–6.84 parts ε-caprolactone, 0.78–4.6 parts γ-(tert-butyl carbamate)-ε-caprolactone, 0.00025–0.00087 parts stannous isooctanoate, and 6.55–7.68 parts trifluoroacetic acid.

[0029] Preferably, the pH-responsive star-shaped amphiphilic polymer comprises the following parts by weight of raw materials: 0.08 to 0.12 parts by weight of pH-responsive star-shaped polymer and 0.03 to 0.16 parts by weight of aldehyde-modified polyethylene glycol.

[0030] Before obtaining star-shaped polymer molecules, the process also includes: concentration, precipitation, filtration, and drying;

[0031] The precipitation is achieved by dissolving the concentrated product in a small amount of dichloromethane, and then transferring this solution into 10 times its volume of cold diethyl ether for precipitation.

[0032] Before obtaining the pH-responsive star polymer, the process also includes: concentration, precipitation, filtration, and drying;

[0033] The precipitation is achieved by dissolving the concentrated product in a small amount of dichloromethane, and then transferring this solution into 10 times its volume of cold diethyl ether for precipitation.

[0034] Preferably, the preparation method of γ-(tert-butyl carbamate)-ε-caprolactone includes the following steps: dissolving 4-(tert-butyloxycarbonylamino)cyclohexanone and 3-chloroperoxybenzoic acid in dichloromethane and reacting at 50°C for 15 h to obtain γ-(tert-butyl carbamate)-ε-caprolactone.

[0035] Preferably, the γ-(tert-butyl carbamate)-ε-caprolactone comprises the following raw materials in parts by weight: 20.8 to 21.3 parts by weight of 4-(tert-butyloxycarbonylamino)cyclohexanone, and 19.7 to 20.6 parts by weight of 3-chloroperoxybenzoic acid.

[0036] The present invention provides a method for preparing pH-responsive star-shaped polymer micelles with the following advantages:

[0037] The preparation method of this invention makes full use of the chemical properties of the reactants, effectively prepares pH-responsive star polymer micelles, has strong operational repeatability, and is suitable for large-scale production applications.

[0038] To achieve the third objective mentioned above, the present invention provides the following technical solution:

[0039] This invention provides an application of pH-responsive star-shaped polymer micelles in anticancer drug carriers.

[0040] pH-responsive star polymer micelles self-assemble in aqueous solution to form polymer micelles, which can be used to encapsulate anticancer drugs. The preparation of pH-responsive star polymer micelles is simple, has a high yield, and has a low critical micelle concentration.

[0041] Preferably, the anticancer drug is a hydrophobic anticancer drug.

[0042] The pH-responsive star-shaped polymer micelles provided by this invention include hydrophobic blocks, which are suitable for loading hydrophobic drugs and can solubilize hydrophobic anticancer drugs, thereby improving the drug loading capacity of polymer micelles.

[0043] Preferably, the preparation method of the anticancer drug carrier includes the following steps: pH-responsive star polymer micelles and hydrophobic anticancer drugs are dissolved in an organic solvent at a ratio of 2:1, stirred for 4 to 12 hours, dialyzed with deionized water for 48 hours, the deionized water is replaced every 4 hours, and after three replacements, the deionized water is replaced every 12 hours, and then freeze-dried.

[0044] It should be noted that when the ratio of pH-responsive star polymer to hydrophobic anticancer drug is 2:1, polymer drug-loaded micelles with uniform particle size distribution and high drug loading can be obtained. Detailed Implementation

[0045] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 The synthetic route diagram for γ-(tert-butyl carbamate)-ε-caprolactone;

[0048] Figure 2 A process route diagram for the synthesis of pH-responsive star polymer micelles;

[0049] Figure 3 The 1H NMR spectrum of aldehyde-modified polyethylene glycol in Example 2;

[0050] Figure 4 The image shows the hydrogen nuclear magnetic resonance spectrum of the star-shaped polymer molecule in Example 3;

[0051] Figure 5 The 1H NMR spectrum of the pH-responsive star-shaped amphiphilic polymer in Example 6;

[0052] Figure 6 The FT-IR spectra of the polymers at each stage of the pH-responsive star polymer synthesis process in Example 6 are shown.

[0053] Figure 7This is a gel permeation chromatogram of the pH-responsive star polymer in Example 6;

[0054] Figure 8 This is a graph showing the critical micelle concentration of the pH-responsive star polymer in Example 6.

[0055] Figure 9 This is a transmission electron microscope image of the pH-responsive star-shaped polymer drug-loaded micelles in Example 11;

[0056] Figure 10 This is an in vitro release curve of pH-responsive star-shaped polymer drug-loaded micelles in Example 12.

[0057] Example 1

[0058] Example 1 provides a preparation process for γ-(tert-butyl carbamate)-ε-caprolactone, such as... Figure 1 As shown, the steps include:

[0059] 4-(tert-butyloxycarbonylamino)cyclohexanone (21.3 g, 0.1 mol) and 3-chloroperoxybenzoic acid (20.6 g, 0.12 mol) were dissolved in anhydrous dichloromethane (100 mL), and the mixture was refluxed at 50 °C for 15 h. After the reaction was completed, the dichloromethane was rotary evaporated, and the concentrated product was added dropwise to a volume of ten times its volume of cold diethyl ether to precipitate. The product was filtered and dried under vacuum at 30 °C for 24 h to obtain γ-(tert-butyl carbamate)-ε-caprolactone.

[0060] Example 2

[0061] Example 2 provides a process for preparing aldehyde-modified polyethylene glycol, including the following steps:

[0062] Polyethylene glycol monomethyl ether (4 g, 2 mmol) was dissolved in anhydrous dichloromethane (40 mL), and dicyclohexylcarbodiimide (0.41 g, 2 mmol) and dimethylaminopyridine (0.27 g, 2 mmol) were added to the above solution. 4-Carboxybenzaldehyde (1.22 g, 10 mmol) was dissolved in dimethylformamide (5 mL), and after complete dissolution, it was added to the above solution. The mixture was evacuated and purged with nitrogen three times, then sealed in a container and stirred at room temperature for 48 hours. The solution was concentrated to 10 mL by rotary evaporation, stored at low temperature, filtered, and the filtrate was added dropwise to 500 mL of diethyl ether solution. After stirring for 15 minutes, the residue was filtered and dissolved in 10 mL of dimethylformamide. The residue was then poured into a 1000 Da dialysis bag and dialyzed for three days. The dialyzed liquid was freeze-dried to obtain the product.

[0063] Example 3

[0064] This embodiment 3 provides a process for preparing star-shaped polymer molecules, including the following steps:

[0065] Under an argon atmosphere, pentaerythritol (0.0681 g, 1 mmol), ε-caprolactone (4.55 g, 40 mmol), and γ-(tert-butyl carbamate)-ε-caprolactone (0.92 g, 4 mmol) were added to a flask. The flask was placed in a 50°C oil bath, stirred, and evacuated for 2 hours. 1 mL of toluene containing stannous isooctanoate (0.1 wt% of the monomer) was added using a syringe. Toluene was removed by repeated purging and degassing. The flask was then vacuum-sealed and magnetically stirred in a 130°C oil bath for 24 hours. The flask was rapidly cooled to room temperature to terminate the polymerization. The copolymer was dissolved in 10 mL of dichloromethane and precipitated dropwise in 500 mL of cold diethyl ether. The precipitate was filtered and dried to constant weight in a vacuum drying oven to obtain star-shaped polymer molecules.

[0066] Example 4

[0067] Example 4 provides a process for preparing star-shaped polymer molecules, including the following steps:

[0068] Under an argon atmosphere, pentaerythritol (0.0681 g, 1 mmol), ε-caprolactone (4.55 g, 40 mmol), and γ-(tert-butyl carbamate)-ε-caprolactone (2.76 g, 12 mmol) were added to a flask. The flask was placed in a 50°C oil bath, stirred, and evacuated for 2 hours. 1 mL of toluene containing stannous isooctanoate (0.1 wt% of the monomer) was added using a syringe. Toluene was removed by repeated purging and degassing. The flask was then vacuum-sealed and magnetically stirred in a 130°C oil bath for 24 hours. The flask was rapidly cooled to room temperature to terminate the polymerization. The copolymer was dissolved in 10 mL of dichloromethane and precipitated dropwise in 500 mL of cold diethyl ether. The precipitate was filtered and dried to constant weight in a vacuum drying oven to obtain star-shaped polymer molecules.

[0069] Example 5

[0070] Example 5 provides a process for preparing star-shaped polymer molecules, including the following steps:

[0071] Under an argon atmosphere, pentaerythritol (0.0681 g, 1 mmol), ε-caprolactone (6.84 g, 60 mmol), and γ-(tert-butyl carbamate)-ε-caprolactone (4.6 g, 20 mmol) were added to a flask. The flask was placed in a 50°C oil bath, stirred, and evacuated for 2 hours. 1 mL of toluene containing stannous isooctanoate (0.1 wt% of the monomer) was added using a syringe. Toluene was removed by repeated purging and degassing. The flask was then vacuum-sealed and magnetically stirred in a 130°C oil bath for 24 hours. The flask was rapidly cooled to room temperature to terminate the polymerization. The copolymer was dissolved in 10 mL of dichloromethane and precipitated dropwise in 500 mL of cold diethyl ether. The precipitate was filtered and dried to constant weight in a vacuum drying oven to obtain star-shaped polymer molecules.

[0072] Example 6

[0073] Example 6 provides a process for preparing pH-responsive star-shaped polymer micelles, such as... Figure 2 As shown, the steps include:

[0074] Step 1: Dissolve the star polymer prepared in Example 3 in 5 mL of dichloromethane and stir for 15 minutes until fully dissolved. Add 5 mL of trifluoroacetic acid and stir vigorously at 0 °C for 2 hours. Terminate the reaction when no bubbles are generated. After removing the solvent by rotary evaporation, add 5 mL of dichloromethane and 1 mL of triethylamine and stir vigorously for 1 hour. After the solution becomes clear, precipitate the mixture dropwise into cold diethyl ether, filter, and vacuum dry for 24 hours to obtain the pH-responsive star polymer.

[0075] Step 2: The pH-responsive star polymer (0.12 g) and the aldehyde-modified polyethylene glycol (0.08 g) prepared in Example 2 were added to a nitrogen-filled Stock flask. 5 mL of anhydrous dimethylformamide was added to dissolve the polymer completely. A small amount of anhydrous sodium sulfate was added to absorb the trace amounts of water generated during the reaction. The container was sealed and reacted for 48 h. After removing the anhydrous sodium sulfate through a syringe filter, the polymer was added dropwise to anhydrous diethyl ether to precipitate the product. The precipitate was then vacuum-dried for 24 h to obtain the pH-responsive star amphiphilic polymer. The molecular weight (Mn) of the polymer was characterized by gel permeation chromatography and found to be 18139.

[0076] Depend on Figures 3-6 This indicates that pH-responsive star-shaped polymer micelles can be successfully prepared.

[0077] Example 7

[0078] Example 7 provides a process for preparing pH-responsive star-shaped polymer micelles, including the following steps:

[0079] Step 1: Dissolve the star polymer prepared in Example 4 in 5 mL of dichloromethane and stir for 15 minutes until fully dissolved. Add 5 mL of trifluoroacetic acid and stir vigorously at 0 °C for 2 hours. Terminate the reaction when no bubbles are generated. After removing the solvent by rotary evaporation, add 5 mL of dichloromethane and 1 mL of triethylamine and stir vigorously for 1 hour. After the solution becomes clear, precipitate the mixture dropwise into cold diethyl ether, filter, and vacuum dry for 24 hours to obtain the pH-responsive star polymer.

[0080] Step 2: The pH-responsive star polymer (0.12 g) and the aldehyde-modified polyethylene glycol (0.08 g) prepared in Example 2 were added to a nitrogen-filled Stock flask. 5 mL of anhydrous dimethylformamide was added to dissolve the polymer completely. A small amount of anhydrous sodium sulfate was added to absorb the trace amounts of water generated during the reaction. The container was sealed and reacted for 48 h. After removing the anhydrous sodium sulfate through a syringe filter, the polymer was added dropwise to anhydrous diethyl ether to precipitate the product. The precipitate was then vacuum-dried for 24 h to obtain the pH-responsive star amphiphilic polymer. The molecular weight (Mn) of the polymer was characterized by gel permeation chromatography and found to be 20837.

[0081] Example 8

[0082] Example 8 provides a process for preparing pH-responsive star-shaped polymer micelles, including the following steps:

[0083] Step 1: Dissolve the star polymer prepared in Example 5 in 5 mL of dichloromethane and stir for 15 minutes until fully dissolved. Add 5 mL of trifluoroacetic acid and stir vigorously at 0 °C for 2 hours. Terminate the reaction when no bubbles are generated. After removing the solvent by rotary evaporation, add 5 mL of dichloromethane and 1 mL of triethylamine and stir vigorously for 1 hour. After the solution becomes clear, precipitate the mixture dropwise into cold diethyl ether, filter, and vacuum dry for 24 hours to obtain the pH-responsive star polymer.

[0084] Step 2: The pH-responsive star polymer (0.12 g) and the aldehyde-modified polyethylene glycol (0.16 g) prepared in Example 2 were added to a nitrogen-filled Stock flask. 5 mL of anhydrous dimethylformamide was added to dissolve the polymer completely. A small amount of anhydrous sodium sulfate was added to absorb the trace amounts of water generated during the reaction. The container was sealed and reacted for 48 h. After removing the anhydrous sodium sulfate through a syringe filter, the polymer was added dropwise to anhydrous diethyl ether to precipitate the product. The precipitate was then vacuum-dried for 24 h to obtain the pH-responsive star amphiphilic polymer. The molecular weight (Mn) of the polymer was characterized by gel permeation chromatography and found to be 35700.

[0085] Example 9

[0086] In Example 9, the critical micelle concentration of the pH-responsive star-shaped amphiphilic polymer prepared in step 2 of Example 6 was tested using a fluorescent probe method. The test steps included:

[0087] Step 1: Prepare a pyrene solution by dissolving pyrene in acetone to a concentration of 6 × 10⁻⁶. -5 M contains a pyrene-acetone solution;

[0088] Step 2: Accurately weigh 10 mg of the pH-responsive star-shaped amphiphilic polymer prepared in Step 2 of Example 6, dissolve it in 5 mL of acetone, and add it dropwise to 100 mL of deionized water. After evaporating the acetone, a 0.1 mg / mL solution is obtained, which is then diluted with deionized water to a series of concentrations (0.0001–0.1 mg / mL). Take 18 10 mL brown volumetric flasks, add 0.1 mL of pyrene solution to each, and then add the polymer solutions of different concentrations to prepare sample solutions. The concentration of pyrene in the sample solutions is 6 × 10⁻⁶. -7 M;

[0089] Step 3, Fluorescence Spectroscopy Test: Using 373nm as the emission wavelength, test the excitation spectrum of the sample solution in the range of 300-350nm, and take I... 337 / I 332 Plot the ratio against the logarithm of concentration (logC) Figure 8 The obtained curve was piecewise fitted, and the x-axis corresponding to the intersection of the two fitted trend lines is the critical micelle concentration value. The critical micelle concentration was measured to be 1.04 mg / L.

[0090] Example 10

[0091] Example 10 describes the self-assembly behavior of the pH-responsive star-shaped amphiphilic polymer prepared in step 2 of Example 6 at pH values ​​above the CMC, and the blank micelle particle size at different pH values ​​as determined by DLS testing.

[0092] The self-assembly process involved dissolving 30 mg of the pH-responsive star-shaped amphiphilic polymer prepared in step 2 in 1 mL of dimethyl sulfoxide, sonicating for 10 min to ensure complete dissolution, and then slowly adding it dropwise to 10 mL of distilled water at a rate of 10 seconds per drop. At this point, the solution exhibited an opalescent appearance. Another 20 mL of distilled water was added to stabilize the micelles. The solution was then transferred to a 1.5 kDa dialysis bag and dialyzed with 100 times its volume of PBS solution for 48 h. The dialysis medium was changed every 4 h, and after three changes, it was changed every 12 h. After dialysis, the solution was filtered through a 0.22 μm syringe filter to obtain a micelle solution with a concentration of 1 mg / mL.

[0093] The blank micelle particle size at different pH values ​​was determined by dividing the blank micelle solution into eight portions, adjusting the pH to 3 to 10, stabilizing for a period of time, and then measuring the particle size at each pH value using dynamic light scattering.

[0094] Example 11

[0095] Example 11 describes the loading of anticancer drugs onto the pH-responsive star-shaped amphiphilic polymers prepared in Examples 6, 7, and 8, and characterizes the particle size distribution and morphology of the pH-responsive star-shaped amphiphilic polymer loaded with anticancer drugs in Example 6.

[0096] The anticancer drug loading consisted of: 15 mg of doxorubicin hydrochloride was added to 0.5 mL of dimethyl sulfoxide (DMSO), followed by the addition of 0.1 mL of TEA and stirring for 1 h in the dark, resulting in three identical DMSO solutions. 30 mg of the pH-responsive astral amphiphilic polymers from Examples 6, 7, and 8 were added to 0.5 mL of DMSO, dissolved completely, and then mixed with the doxorubicin solution. After stirring in the dark for 12 h, the mixture was slowly added dropwise to 10 mL of distilled water at a rate of 10 seconds per drop, followed by the addition of 20 mL of distilled water to stabilize the micelles. The mixture was then transferred to a 1.5 kDa dialysis bag and dialyzed with 100 times the volume of PBS solution for 48 h, changing the dialysis medium every 4 h for three times, and then every 12 h thereafter. After dialysis, the solution was filtered through a 0.22 μm syringe filter to obtain a drug-loaded micelle solution with a concentration of approximately 1 mg / mL. After freeze-drying, three different drug-loaded micelle powders were obtained.

[0097] Example 6: Morphological characterization of pH-responsive star-shaped amphiphilic polymers loaded with anticancer drugs as follows: Figure 9 As shown, the particle size and particle size distribution were measured using dynamic light scattering. Laser light scattering revealed that the average particle size of the pH-responsive polymer micelles loaded with anticancer drugs was 90.4 nm, and the particle size distribution was 0.277. TEM observation showed that their morphology was spherical.

[0098] Example 12

[0099] Example 12 describes a drug release test on the pH-responsive star polymer micelles loaded with anticancer drugs prepared in Example 11. The test includes the following steps:

[0100] Accurately weigh 5 mg of the pH-responsive star polymer micelles loaded with anticancer drugs prepared in Example 11. Weigh two portions of each type of drug-loaded micelle, for a total of six portions of the three types of drug-loaded micelles, and dissolve them in 5 mL of buffer solutions at pH 7.4 and pH 5.0, respectively. After complete dissolution, transfer the solutions to 3.5 kDa dialysis bags and immerse them in 95 mL of the corresponding buffer solutions for drug release. Set the temperature and rotation speed to 37°C and 100 rpm, respectively. At the set time intervals (0.5, 1, 2, 3, 6, 9, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120 h), remove 5 mL of the solution from the beaker and simultaneously replenish 5 mL of the corresponding buffer solution. Measure the absorbance of the taken solutions at 498 nm using ultraviolet spectrophotometry and plot the in vitro release curve.

[0101] The results can be found in [link to results]. Figure 10 ,from Figure 10It can be seen that in a normal blood pH environment of 7.4, the release rate of the three drug-loaded micelles is slow, with the cumulative release amount within 6 hours all below 10% and within 120 hours all below 30%. PT-P[(CL 20 Drug release profiles and PT-P[(CL2)MPEG)]4 drug-loaded micelles 20 The drug release curves of the drug-loaded micelles [-co-ACL6)MPEG]4 showed similar trends, with the former having a cumulative release of 25.6% over 120 hours and the latter a final cumulative release of 26.8%, while P[(CL 30 -co-ACL 10 The drug release curves of the MPEG2]4 drug-loaded micelles remained at a low level, with a final cumulative release of 20.7%. At pH 5.0, the drug release rates of the three drug-loaded micelles were rapid, with a cumulative release of 30% over 12 hours, which is consistent with P[(CL]. 20 Compared to PT-P[(CL-ACL2)MPEG]4, PT-P[(CL-ACL2)MPEG]4 is more advanced. 20 The drug release rate of the drug-loaded micelles (-co-ACL6)MPEG)]4 was relatively fast within 48 hours, and the cumulative release rate was as high as 95% within 120 hours, while P[(CL) 20 The cumulative drug release of the drug-loaded micelles (-co-ACL2)MPEG]4 within 120 hours was only 82.6%. In the comparison of drug release rates among the three types of drug-loaded micelles, P[(CL2)MPEG]4 showed the highest drug release rate. 30 -co-ACL 10 The drug-loaded micelles [MPEG2]4 exhibited the fastest drug release rate within 48 hours, followed by a slowing trend after 48 hours, with a cumulative drug release of 90.4% within 120 hours. These experimental results demonstrate that the three drug-loaded micelles exhibit good pH responsiveness, with no burst release observed, thus meeting the requirements for controlled release. PT-P[(CL] 20 The final cumulative drug release effect is best achieved by using drug-loaded micelles with the following properties: -co-ACL6)MPEG)]4.

[0102] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pH-responsive star-shaped polymer micelle, characterized in that, The polymer in the polymer micelles has the following structural formula: where x = 5~30, y = 1~6, m = 1~2; 。 2. The pH-responsive star-shaped polymer micelles according to claim 1, characterized in that, The number-average molecular weight of the pH-responsive star polymer is 11,500–35,700 g / mol.

3. A method for preparing pH-responsive star-shaped polymer micelles as described in claim 1 or 2, characterized in that, Includes the following steps: After mixing polyethylene glycol monomethyl ether, 4-carboxybenzaldehyde, dehydrating agent, solvent and first catalyst, the mixture was evacuated and purged with nitrogen three times, and stirred at room temperature to carry out esterification reaction to obtain aldehyde-modified polyethylene glycol. Under an argon atmosphere, pentaerythritol, ε-caprolactone, γ-(tert-butyl carbamate)-ε-caprolactone, solvent, and a second catalyst were mixed and subjected to a ring-opening polymerization reaction to obtain star-shaped polymer molecules. The star-shaped polymer molecules were dissolved in dichloromethane with trifluoroacetic acid and then stirred to obtain a pH-responsive star-shaped polymer. Under a nitrogen atmosphere, the pH-responsive star polymer and the aldehyde-modified polyethylene glycol obtained in step 1 were dissolved in dimethylformamide and subjected to a Schiff base reaction to obtain a pH-responsive star amphiphilic polymer. The pH-responsive star-shaped amphiphilic polymer was dialyzed to obtain pH-responsive star-shaped polymer micelles. The dehydrating agent is dicyclohexylcarbodiimide, the first catalyst is dimethylaminopyridine, the solvent is dichloromethane or dimethylformamide, and the esterification reaction time is 24 h; In preparing the star-shaped amphiphilic polymer, the solvent is toluene, the second catalyst is stannous isooctanoate, and the ring-opening polymerization reaction is carried out at a temperature of 130°C for 24 hours. The Schiff base reaction time was 48 hours.

4. The method for preparing pH-responsive star-shaped polymer micelles according to claim 3, characterized in that, The preparation method of γ-(tert-butyl carbamate)-ε-caprolactone includes the following steps: dissolving 4-(tert-butyloxycarbonylamino)cyclohexanone and 3-chloroperoxybenzoic acid in dichloromethane and reacting at 50°C for 15 h to obtain γ-(tert-butyl carbamate)-ε-caprolactone.

5. The method for preparing pH-responsive star-shaped polymer micelles according to claim 3, characterized in that, The aldehyde-modified polyethylene glycol comprises the following raw materials in parts by weight: 2-4 parts polyethylene glycol monomethyl ether, 0.55-1.22 parts 4-carboxybenzaldehyde, 0.22-0.41 parts dicyclohexylcarbodiimide, and 0.15-0.27 parts dimethylaminopyridine.

6. The method for preparing pH-responsive star-shaped polymer micelles according to claim 3, characterized in that, The pH-responsive star polymer comprises the following raw materials in parts by weight: 0.056–0.0681 parts pentaerythritol, 3.56–6.84 parts ε-caprolactone, 0.78–4.6 parts γ-(tert-butyl carbamate)-ε-caprolactone, 0.00025–0.00087 parts stannous isooctanoate, and 6.55–7.68 parts trifluoroacetic acid.

7. The method for preparing pH-responsive star-shaped polymer micelles according to claim 3, characterized in that, The pH-responsive star-shaped amphiphilic polymer comprises the following parts by weight of raw materials: 0.08 to 0.12 parts by weight of pH-responsive star-shaped polymer, and 0.03 to 0.16 parts by weight of aldehyde-modified polyethylene glycol.

8. The use of the pH-responsive star polymer micelles prepared by the preparation method according to any one of claims 3 to 7 in the preparation of anticancer drug carriers.

9. The application according to claim 8, characterized in that, The preparation method of the anticancer drug carrier includes the following steps: pH-responsive star polymer micelles and hydrophobic anticancer drugs are dissolved in an organic solvent at a ratio of 2:1, stirred for 4 to 12 hours, dialyzed with deionized water for 48 hours, the deionized water is replaced every 4 hours, and after three replacements, the deionized water is replaced every 12 hours, and then freeze-dried.

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