A poly(2-ethyl-2-oxazoline) block copolymer containing a sulfobetaine side group, and a preparation method and application thereof

Abstract

The application provides a poly(2-ethyl-2-oxazoline) block copolymer containing a sulfobetaine side group and a preparation method and application thereof. The copolymer prepared by the application has enhanced biocompatibility and stronger water absorption capacity due to the introduction of the sulfobetaine side group (the water absorption capacity of which is the strongest among zwitterionic groups) and poly(2-ethyl-2-oxazoline), and is more conducive to forming a hydration layer in a living body, so that water molecules repel the approach of immunoglobulins, thereby avoiding causing an immune response, and is expected to have a potential and huge development prospect in the field of biomedical materials. The copolymer of the application can be applied to drug loading and has excellent drug loading capacity and a slow release effect.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups, its preparation method and application. Background Technology

[0002] Biocompatible materials are key to ensuring medical safety and improving treatment outcomes. How to improve the biocompatibility of medical materials is a major challenge facing the development of existing medical materials.

[0003] Zwitterions are groups that possess both positive and negative charge regions. They exhibit the strongest known hydration (each zwitterion can adsorb at least 7-8 water molecules). In vivo, this unique hydrophilicity allows for the formation of a robust hydration layer on the zwitter surface. This water molecule layer repels proteins, thus hindering the adsorption of immunoglobulins and preventing immune responses. Three common zwitterions are sulfobetaine (SB), carboxybetaine (CB), and phosphorylcholine (PC). Studies have found that the sulfobetaine zwitterion possesses the best hydrophilic properties. Therefore, zwitterions demonstrate potential and broad application prospects in fields such as biopharmaceuticals. Peng et al. reported a block copolymer PS-b-SBMA with zwitterionic side groups. This was achieved by synthesizing a polystyrene macromolecular initiator (PS-Br) with bromine-terminated groups, followed by polymerization with a methacrylate monomer (SBMA) containing zwitterionic side groups of sulfonate betaine. Zhang et al. reported the preparation of hydroxyl-terminated poly(dimethylamine methacrylate) using dimethylamine ethyl methacrylate as a monomer and mercaptoethanol as a chain transfer agent via free radical polymerization. This was then reacted with caprolactone under stannous octoate catalysis to synthesize a poly(dimethylamine methacrylate)-polycaprolactone block copolymer, which was further ring-opened with 1,3-propanesulfonic acid lactone to synthesize a poly(dimethylamine methacrylate)-polycaprolactone block copolymer with zwitterionic side groups of sulfonate betaine. The copolymers prepared in these cases suffer from insufficient water solubility and biocompatibility of the blocks.

[0004] Poly(2-ethyl-2-oxazoline) (PEtOx or PEtOZ) is an important synthetic polymer material, belonging to the poly(2-oxazoline) family (PAOx). Due to its unique biocompatibility, it has received widespread attention in recent years in fields such as biomedicine, coatings, and adhesives. In 1996, Seeliger, W. first reported the ring-opening polymerization (ROP) of 2-oxazoline monomers, laying the foundation for the PAOx family; in 2005, Hoogenboom, R. first clearly defined the temperature responsiveness of PEtOx and its analogy with PEG, proving that PEtOx is a material with excellent biocompatibility; in 2012, Gaertner, F. C. presented systematic evidence for PEtOx as a PEG alternative.

[0005] Poly(2-ethyl-2-oxazoline) containing zwitterionic side groups is a polymer that combines zwitterions and poly(2-ethyl-2-oxazoline) at the molecular level. It combines the high biocompatibility of poly(2-ethyl-2-oxazoline) with the high hydrophilicity and anti-non-specific immunogenicity of zwitterions. Currently, there are few reports on poly(2-ethyl-2-oxazoline) polymer materials, especially block copolymers, containing zwitterionic side groups. Lutz Tauhardt et al. reported an oxazoline polymer with zwitterionic side groups, synthesized through ring-opening polymerization of an oxazoline monomer containing double bonds, followed by the introduction of zwitterionic groups via a click reaction. The high blood compatibility, low cytotoxicity, and anticoagulant activity demonstrate its potential applications in biomedicine. The above reaction utilizes only poly(2-ethyl-2-oxazoline), leaving room for improvement in drug loading and drug release time.

[0006] In summary, there are no reports on the presence of sulfonate betaine groups on the side groups of poly(2-ethyl-2-oxazoline) block copolymers; therefore, it is of great significance to study a poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups and explore its applications. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a poly(2-ethyl-2-oxazoline) block copolymer containing a sulfobetaine side group, its preparation method, and its applications. The copolymer prepared by this invention, due to the introduction of the sulfobetaine side group (which has the strongest water absorption capacity among zwitterionic groups) and poly(2-ethyl-2-oxazoline), exhibits enhanced biocompatibility and stronger water absorption capacity, making it more conducive to the formation of a hydration layer in vivo. Water molecules repel the approach of immunoglobulins, avoiding immune responses, and this copolymer is expected to have significant potential in the field of biomedical materials. The copolymer of this invention can be used for drug loading, exhibiting excellent drug loading capacity and sustained-release effects.

[0008] The technical solution of the present invention is as follows:

[0009] A first aspect of the present invention provides a poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups, having the structure shown in formula (1):

[0010] (1)

[0012] Wherein, R1 is a C3-C8 straight-chain alkylene group; R is selected from one or a combination of two or more polymer segments having the following repeating structural units:

[0013] .

[0014] According to a preferred embodiment of the present invention, the poly(2-ethyl-2-oxazoline) block copolymer containing a sulfonate betaine side group is selected from one of the following structures:

[0015]

[0016] Where a, d, m, n, x, y, and z are integers ranging from 10 to 5000.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups, comprising the steps of:

[0018] S1. In a solvent, under the initiation of an initiator, 2-ethyl-2-oxazoline undergoes a ring-opening polymerization reaction to obtain poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups.

[0019] S2. In a solvent, under the action of an alkali, poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups reacts with acryloyl chloride to obtain poly(2-ethyl-2-oxazoline) with terminal double bonds.

[0020] S3. In a solvent, under the action of alkali, poly(2-ethyl-2-oxazoline) with terminal double bonds reacts with a polymer with amino groups to obtain a poly(2-ethyl-2-oxazoline) block copolymer.

[0021] S4. In a solvent, a poly(2-ethyl-2-oxazoline) block copolymer is reacted with a sulfonyl lactone to obtain a poly(2-ethyl-2-oxazoline) block copolymer containing a sulfonyl betaine side group.

[0022] According to a preferred embodiment of the present invention, in step S1, the solvent is acetonitrile; the volume ratio of 2-ethyl-2-oxazoline to the solvent is 1-3 mol / L.

[0023] According to a preferred embodiment of the present invention, in step S1, the initiator is methyl p-toluenesulfonate; the molar amount of the initiator is 0.5-2% of 2-ethyl-2-oxazoline.

[0024] According to a preferred embodiment of the present invention, in step S1, the ring-opening polymerization reaction temperature is 120-160°C, the reaction time is 20-30 hours, and the reaction is carried out under protective gas and stirring conditions. The protective gas is nitrogen or argon.

[0025] According to a preferred embodiment of the present invention, in step S1, a terminator is added after the ring-opening polymerization reaction to terminate the reaction; the terminator is a KOH methanol solution with a mass concentration of 10%-40%.

[0026] According to a preferred embodiment of the present invention, in step S1, the post-treatment method of the reaction solution obtained by the ring-opening polymerization reaction is as follows: the reaction solution is precipitated with anhydrous diethyl ether and filtered to obtain poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups.

[0027] According to a preferred embodiment of the present invention, in step S2, the solvent is N,N-dimethylformamide; the molar amount of poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups and the volume ratio of the solvent are 0.1-1 mol / L.

[0028] According to a preferred embodiment of the present invention, in step S2, the base is triethylamine; the molar amount of the base is 1-1.5 times the molar amount of poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups.

[0029] According to a preferred embodiment of the present invention, in step S2, the molar ratio of poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups to acryloyl chloride is 1:1-1.5.

[0030] According to a preferred embodiment of the present invention, in step S2, the reaction temperature is 50-70°C, the reaction time is 20-30 hours, and the reaction is carried out under stirring and a protective gas atmosphere. The protective gas is nitrogen or argon.

[0031] According to a preferred embodiment of the present invention, in step S2, the post-treatment method of the reaction solution obtained from the reaction is as follows: the reaction solution is precipitated with anhydrous diethyl ether, filtered, and dried to obtain poly(2-ethyl-2-oxazoline) with terminal double bonds.

[0032] According to a preferred embodiment of the present invention, in step S3, the solvent is ethanol; the molar amount of poly(2-ethyl-2-oxazoline) with terminal double bonds and the volume ratio of the solvent are 0.005-0.01 mol / L.

[0033] According to a preferred embodiment of the present invention, in step S3, the base is triethylamine; the molar amount of the base is 3-5% of the molar amount of poly(2-ethyl-2-oxazoline) with terminal double bonds.

[0034] According to a preferred embodiment of the present invention, in step S3, the polymer with an amino terminal is a polymer with an amino terminal at one end; the polymer with an amino terminal is selected from polyethylene glycol with an amino terminal, polyethylene glycol-polylactic acid block copolymer with an amino terminal, polyethylene glycol-polycaprolactone block copolymer with an amino terminal, polyethylene glycol-polyglycolic acid block copolymer with an amino terminal, polyethylene glycol-polymethyl methacrylate block copolymer with an amino terminal, or polyethylene glycol-polystyrene block copolymer with an amino terminal.

[0035] Preferably, the polymer with amino-terminated groups is selected from one of the following:

[0036]

[0037] Where a, d, n, x, y, and z are integers ranging from 10 to 5000.

[0038] According to a preferred embodiment of the present invention, in step S3, the molar ratio of the poly(2-ethyl-2-oxazoline) with terminal double bonds to the polymer with amino groups is 1:1.

[0039] According to a preferred embodiment of the present invention, in step S3, the reaction temperature is 40-80°C, the reaction time is 4-8 hours, and the reaction is carried out under stirring and a protective gas atmosphere. The protective gas is nitrogen or argon.

[0040] According to a preferred embodiment of the present invention, in step S3, the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution is precipitated with anhydrous diethyl ether, filtered, and dried to obtain poly(2-ethyl-2-oxazoline) block copolymer.

[0041] According to a preferred embodiment of the present invention, in step S4, the solvent is ethanol; the molar ratio of the poly(2-ethyl-2-oxazoline) block copolymer to the volume ratio of the solvent is 0.01-0.05 mol / L.

[0042] According to a preferred embodiment of the present invention, in step S4, the sulfonyl lactone is any one of propanesulfonyl lactone, butanesulfonyl lactone, pentasulfonyl lactone, hexanesulfonyl lactone, heptasulfonyl lactone, or octanesulfonyl lactone.

[0043] According to a preferred embodiment of the present invention, in step S4, the molar ratio of poly(2-ethyl-2-oxazoline) block copolymer to sulfonyl lactone is 1:1-2.

[0044] According to a preferred embodiment of the present invention, in step S4, the reaction temperature is 20-80°C, the reaction time is 4-8 hours, and the reaction is carried out under stirring conditions.

[0045] According to a preferred embodiment of the present invention, in step S4, the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution is precipitated with anhydrous diethyl ether, filtered, and dried to obtain a poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups.

[0046] A third aspect of the present invention provides the use of the above-mentioned poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups as a drug carrier for loading drugs.

[0047] According to a preferred embodiment of the present invention, a method for loading a drug as a drug carrier is as follows: a poly(2-ethyl-2-oxazoline) block copolymer containing a sulfonate betaine side group and the drug are dissolved in a solvent, transferred to a dialysis bag, and then placed in water for dialysis; the liquid in the dialysis bag is freeze-dried to achieve drug loading.

[0048] The copolymer reaction route of this invention is shown below:

[0049]

[0050] Where a, b, d, m, n, x, y, and z are integers ranging from 10 to 5000; R1 is a C3 to C8 straight-chain alkylene group.

[0051] Technical features and beneficial effects of the present invention:

[0052] 1. Compared with traditional polyethylene glycol-polyester block copolymers containing methoxy end groups, the poly(2-ethyl-2-oxazoline) block copolymer containing sulfobetaine side groups prepared in this invention has enhanced biocompatibility and stronger water absorption capacity due to the introduction of sulfobetaine side groups (which have the strongest water absorption capacity among zwitterionic groups) and poly(2-ethyl-2-oxazoline). This makes it more conducive to the formation of a hydration layer in the body, and water molecules repel the approach of immunoglobulins, thus avoiding immune responses. It is expected to have a potential and huge development prospect in the field of biomedical materials.

[0053] 2. The introduction of the sulfobetaine side group in this invention allows for the bonding of more water molecules, forming a dense hydration layer on the surface and enhancing biocompatibility. The hydrophobic block copolymer ensures the drug-carrying capacity of the material, enabling the encapsulation of more drugs and providing a certain sustained-release effect. The block copolymer of this invention spontaneously aggregates in a solvent to form micelles, encapsulating hydrophobic drugs within the core, thereby achieving drug loading. After drug loading, it can achieve slow drug release under acidic and alkaline conditions, and can also release drugs within cells. Attached Figure Description

[0054] Figure 1 The GPC spectra of poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer (PEOG), amino-terminated polyethylene glycol (NH2-PEG), and poly(2-ethyl-2-oxazoline) (PEOZ) in Example 1 are shown; the horizontal axis represents the elution time (min).

[0055] Figure 2 The images show the 1H NMR spectra of the poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer and the poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer containing sulfonate betaine side groups in Example 1.

[0056] Figure 3 This is a TEM image of the drug-loaded micelle aqueous dispersion in the experimental example.

[0057] Figure 4 This is a diagram showing drug release from drug-loaded micelles in different pH media in the experimental example. Detailed Implementation

[0058] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0059] Unless otherwise specified, all raw materials used in the embodiments are commercially available products; all equipment used is conventional equipment; and all methods described are existing technologies.

[0060] Example 1

[0061] The specific reaction route for the preparation of poly(2-ethyl-2-oxazoline) block copolymers containing sulfonate betaine side groups is as follows:

[0062]

[0063] Specific steps:

[0064] (1) A 100ml single-necked flask was baked at 120℃ for 3 hours. While still hot, it was connected to a vacuum line and argon gas was introduced. After the flask cooled, a vacuum was drawn, and the flask was baked with an alcohol lamp while being evacuated. After cooling, argon gas was introduced. This process was repeated three times. Under an argon atmosphere, 10ml of ethylene oxide was added. Under an ice-water bath at 0℃, 40ml of tetrahydrofuran (THF) and 5ml of potassium hexamethyldisilazide (KHMDS) initiator were added. The mixture was stirred at 0℃ in an ice-water bath for 24 hours and then at room temperature for 12 hours to form a brownish-red viscous liquid. 1ml of methanol was added and stirred for 30 minutes to terminate the reaction. 1ml of trifluoroacetic acid was added and stirred at room temperature for 2 hours. The mixture was then poured into an anhydrous diethyl ether solution and filtered to obtain a white viscous solid. The solid was dried in a vacuum drying oven for 24 hours to obtain a white powdery solid terminal amino polyethylene glycol with a yield of 95.9%. GPC: M n =2000, PDI=1.15.

[0065] (2) Add 50 ml of acetonitrile to a 100 ml three-necked flask, purge with nitrogen, add 0.1 mol of 2-ethyl-2-oxazoline and 0.65 mmol of methyl p-toluenesulfonate (MeOTs), heat to 140 °C and stir for 24 h, then add 1 ml of KOH in methanol solution (mass concentration 10%) to terminate the reaction, precipitate in anhydrous diethyl ether, and filter to obtain a transparent viscous liquid. The yield was 97%.

[0066] (3) The poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups obtained above (10 mmol) was dissolved in 40 mL of DMF, and 12 mmol of acryloyl chloride and 12 mmol of triethylamine were added. The mixture was stirred at 60 °C under nitrogen protection for 24 h, precipitated in anhydrous diethyl ether, filtered, and dried in a vacuum oven to obtain poly(2-ethyl-2-oxazoline) with terminal double bonds. The yield was 86%.

[0067] (4) Add 0.5 mmol of terminal double-bonded poly(2-ethyl-2-oxazoline) and 0.5 mmol of the amino-terminated polyethylene glycol prepared in step (1) to a single-necked flask, dissolve in 100 ml of ethanol, add 0.02 mmol of triethylamine dropwise, stir at 60 °C for 6 h under a nitrogen atmosphere, precipitate in anhydrous diethyl ether, filter, and dry to obtain poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer. Yield: 94%.

[0068] (5) Then, 1 mmol of the copolymer was dissolved in 50 ml of ethanol, and 1.5 mmol of 1,3-propanesulfonic acid lactone was added. The mixture was stirred at 60 °C for 6 h under a nitrogen atmosphere. The precipitate was then collected in anhydrous diethyl ether, filtered, and dried to obtain a poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer containing sulfobetaine side groups. Yield: 81%

[0069] Depend on Figure 1The results show that the GPC curve of poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer (PEOG) is significantly shifted towards the higher molecular weight side compared with the curves of the first step product of amino-terminated polyethylene glycol (NH2-PEG) and poly(2-ethyl-2-oxazoline) (PEOZ). At the same time, the elution curve is a single peak, indicating that poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer was obtained.

[0070] Depend on Figure 2 The results show that the chemical shifts δ=1.11ppm, δ=3.12ppm, and δ=3.33ppm are the peaks a, b, and c of the three methylene groups of the zwitterionic sulfonic acid group. Therefore, it can be concluded that the poly(2-ethyl-2-oxazoline)-polyethylene glycol block copolymer containing sulfonate betaine side groups was successfully synthesized in this embodiment.

[0071] Example 2

[0072] The preparation of poly(2-ethyl-2-oxazoline) block copolymers containing sulfonate betaine side groups is as described in Example 1, except that:

[0073] Step (1) is as follows:

[0074] Two self-made 250ml single-necked bottles connected together were used as a double single-necked bottle, designated as bottle A and bottle B. The bottles were dried at 120℃ for 3 hours. While still hot, bottles A and B were connected to a vacuum line and argon gas was introduced. After the bottles cooled, a vacuum was drawn, and the bottles were heated with an alcohol lamp while being evacuated. After cooling, argon gas was introduced, and this process was repeated three times. Under an argon atmosphere, 6.525g of lactide was added to bottle B. Magnetic stir bar was added to both bottles A and B. Bottle A was added to 15ml of tetrahydrofuran (THF), 4ml of initiator (potassium hexamethyldisilazane), and 5ml of ethylene oxide under an ice-water bath at 0℃. Bottle A was stirred in an ice-water bath at 0℃ for 24 hours, then stirred at room temperature for 12 hours, forming a brownish-red viscous liquid. The reaction liquid (PEG) was extracted and the M was measured. n =2500, quickly poured into bottle B, stirred at room temperature for 2 hours, added 1 ml of methanol and stirred for 30 minutes to terminate the reaction, added 1 ml of trifluoroacetic acid, stirred for 2 hours, poured into anhydrous ethanol solution, filtered to obtain a white viscous solid, dried in a vacuum oven for 24 hours to obtain a white powdery solid amine-terminated polyethylene glycol-polylactic acid block copolymer. The yield was 93%. The structure of the amine-terminated polyethylene glycol-polylactic acid block copolymer is as follows:

[0075]

[0076] In step (4), the terminal amino polyethylene glycol is replaced with the terminal amino polyethylene glycol-polylactic acid block copolymer prepared above; the yield is 85%.

[0077] Step (5) is as follows: 1 mmol of the copolymer is then dissolved in 50 ml of ethanol, and 1.2 mmol of butyryl lactone is added. The mixture is stirred at room temperature for 6 h under a nitrogen atmosphere, precipitated in anhydrous diethyl ether, filtered, and dried to obtain a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polylactic acid block copolymer containing sulfobetaine side groups. The yield is 79%.

[0078] The other steps and conditions are the same as in Example 1.

[0079] The structural formula of the poly(2-ethyl-2-oxazoline)-polyethylene glycol-polylactic acid block copolymer containing sulfonate betaine side groups is as follows:

[0080]

[0081] Example 3

[0082] The preparation of the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is as described in Example 2, except that:

[0083] In step (1), lactide was replaced with 5.135 g of caprolactone; a white powdery solid amino-terminated polyethylene glycol-polycaprolactone block copolymer was obtained. The yield was 91%. The structure of the amino-terminated polyethylene glycol-polycaprolactone block copolymer is as follows:

[0084]

[0085] In step (4), the terminal amino polyethylene glycol-polylactic acid block copolymer was replaced with the terminal amino polyethylene glycol-polycaprolactone block copolymer prepared above; the yield was 81%.

[0086] Step (5) is the same as in Example 2, yielding a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polycaprolactone block copolymer containing sulfonate betaine side groups, with a yield of 78%.

[0087] The other steps and conditions are the same as in Example 2. The structure of the poly(2-ethyl-2-oxazoline)-polyethylene glycol-polycaprolactone block copolymer containing sulfonate betaine side groups is as follows:

[0088]

[0089] Example 4

[0090] The preparation of the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is as described in Example 2, except that:

[0091] In step (5), butyrate lactone is replaced with the same molar amount of pentosulfonate lactone; a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polylactic acid block copolymer containing sulfobetaine side groups is obtained with a yield of 80%.

[0092] Other steps and conditions are the same as in Example 2. The poly(2-ethyl-2-oxazoline)-polyethylene glycol-polylactic acid block copolymer containing sulfonate betaine side groups has the following structure:

[0093]

[0094] Example 5

[0095] The preparation of the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is as described in Example 2, except that:

[0096] In step (1), lactide was replaced with 2.32 g of glycolide; a white powdery solid amino-terminated polyethylene glycol-polyglycolic acid block copolymer was obtained. The yield was 84%. The structure of the amino-terminated polyethylene glycol-polyglycolic acid block copolymer is as follows:

[0097]

[0098] In step (4), the terminal amino polyethylene glycol-polylactic acid block copolymer was replaced with the terminal amino polyethylene glycol-polyglycolic acid block copolymer prepared above; yield 68%.

[0099] In step (5), butyryl lactone is replaced with the same molar amount of propanesulfonate lactone; a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polyglycolic acid block copolymer containing sulfobetaine side groups is obtained with a yield of 76%.

[0100] Other steps and conditions are the same as in Example 2. The structure of the poly(2-ethyl-2-oxazoline)-polyethylene glycol-polyglycolic acid block copolymer containing sulfonate betaine side groups is as follows:

[0101]

[0102] Example 6

[0103] The preparation of the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is as described in Example 2, except that:

[0104] In step (1), lactide was replaced with 2.32 g of methacrylic acid; a white powdery solid amino-terminated polyethylene glycol-polymethacrylic acid block copolymer was obtained. The yield was 90%. The structure of the amino-terminated polyethylene glycol-polymethacrylic acid block copolymer is as follows:

[0105]

[0106] In step (4), the terminal amino polyethylene glycol-polylactic acid block copolymer was replaced with the terminal amino polyethylene glycol-polymethacrylic acid block copolymer prepared above; yield 90%.

[0107] In step (5), butyryl lactone is replaced with the same molar amount of pentosulfonate lactone; a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polymethacrylic acid block copolymer containing sulfobetaine side groups is obtained with a yield of 72%.

[0108] Other steps and conditions are the same as in Example 2. The structure of the poly(2-ethyl-2-oxazoline)-polyethylene glycol-polymethacrylic acid block copolymer containing sulfonate betaine side groups is as follows:

[0109]

[0110] Example 7

[0111] The preparation of the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is as described in Example 2, except that:

[0112] In step (1), lactide was replaced with 2.32 g of styrene; a white powdery solid amino-terminated polyethylene glycol-polystyrene block copolymer was obtained. The yield was 88%. The structure of the amino-terminated polyethylene glycol-polystyrene block copolymer is as follows:

[0113]

[0114] In step (4), the terminal amino polyethylene glycol-polylactic acid block copolymer was replaced with the terminal amino polyethylene glycol-polystyrene block copolymer prepared above; yield 88%.

[0115] In step (5), butyryl lactone is replaced with the same molar amount of pentosulfonate lactone; a poly(2-ethyl-2-oxazoline)-polyethylene glycol-polystyrene block copolymer containing sulfobetaine side groups is obtained with a yield of 78%.

[0116] Other steps and conditions are the same as in Example 1. The structure of the poly(2-ethyl-2-oxazoline)-polyethylene glycol-polystyrene block copolymer containing sulfonate betaine side groups is as follows:

[0117]

[0118] Test case

[0119] 1) Alkalization of Doxorubicin

[0120] To increase the hydrophobicity of doxorubicin and make it easier for it to be encapsulated in the hydrophobic core of micelles, the water-soluble doxorubicin hydrochloride needs to be converted into a hydrophobic doxorubicin base. Weigh 5.0 mg DOX·HCl and dissolve it in 2 mL DMSO. Add excess triethylamine (20 μL, approximately 10 equivalents) to the above solution and stir the mixture at room temperature in the dark for 6 hours. After the reaction is complete, add the mixture dropwise to 50 mL of ice-cold diethyl ether to precipitate the solid. Centrifuge (8000 rpm, 10 min) to collect the red solid, wash the precipitate twice with diethyl ether, and dry it under vacuum to obtain hydrophobic doxorubicin (DOX-base) for later use.

[0121] (2) Preparation of drug-loaded micelles (dialysis method)

[0122] Preparation of drug-loaded micelles: Accurately weigh 50.0 mg of the block copolymer prepared by the method in Example 2 and 2.5 mg of the DOX-base prepared above (theoretical drug loading of 5% w / w), and dissolve them together in 10 mL of DMF. Sonication is used to aid dissolution, forming a clear red solution. Self-assembly and dialysis: Transfer the above DMF solution to a dialysis bag (MWCO 3500 Da). Place the dialysis bag in a beaker containing 500 mL of ultrapure water and dialyze at room temperature in the dark. Change the dialysis water every 4-6 hours for a total of 24 hours. During this process, the DMF is gradually replaced by water, and the copolymer spontaneously aggregates to form micelles, encapsulating the hydrophobic DOX within the core. Collection and purification: After dialysis, transfer the micelle solution from the dialysis bag to centrifuge tubes. If necessary, filter through a 0.45 μm microporous membrane to remove any unencapsulated small amounts of drug aggregates to obtain the drug-loaded micelle solution. Freeze-drying: The filtered micelle solution was dispensed, pre-frozen at -80°C overnight, and then transferred to a freeze dryer for freeze-drying for 48 hours to obtain red, spongy drug-loaded micelle solids, which are easy to store and weigh.

[0123] Accurately weigh the drug-loaded micelle solids and thoroughly disperse them in ultrapure water to prepare a 1 mg / mL aqueous dispersion of drug-loaded micelles (containing 1 mg of doxorubicin), and place it into a dialysis bag (MWCO 3500 Da). Completely immerse the dialysis bag in 50 mL of the appropriate release medium (PBS buffer at pH 7.4 or pH 5.6). Place the entire system in a constant-temperature shaking incubator at 37°C and 100 rpm, protected from light. At the preset time points, take 2 mL of solution from the release medium for detection, and immediately replenish with an equal volume of fresh release medium at the same temperature.

[0124] Drug concentration determination: The absorbance of the sample solution was measured at a wavelength of 480 nm using a UV-Vis spectrophotometer, and the cumulative drug concentration was calculated based on the standard curve.

[0125] Cumulative release rate calculation:

[0126] Cumulative release rate (%) = (Mt / Mtotal) × 100%

[0127] Where Mt is the total amount of drug released at time t, and Mtotal is the total amount of drug encapsulated in the micelles.

[0128] Figure 3 This is a transmission image of the drug-loaded micelle aqueous dispersion, showing the formation of spherical micelles.

[0129] Figure 4 The data show the release efficiency of doxorubicin in release media at pH 7.4 and pH 5.6. The graph shows that the drug release is higher in the weakly acidic environment at pH 5.6.

Claims

1. A poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups, characterized in that, It has the structure shown in equation (1): （1） Wherein, R1 is a C3-C8 straight-chain alkylene group; R is selected from one or a combination of two or more polymer segments having the following repeating structural units: 。 2. The poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 1, characterized in that, The poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups is selected from one of the following structures: Where a, d, m, n, x, y, and z are integers ranging from 10 to 5000.

3. A method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups as described in claim 1 or 2, comprising the steps of: S1. In a solvent, under the initiation of an initiator, 2-ethyl-2-oxazoline undergoes a ring-opening polymerization reaction to obtain poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups. S2. In a solvent, under the action of an alkali, poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups reacts with acryloyl chloride to obtain poly(2-ethyl-2-oxazoline) with terminal double bonds. S3. In a solvent, under the action of alkali, poly(2-ethyl-2-oxazoline) with terminal double bonds reacts with a polymer with amino groups to obtain a poly(2-ethyl-2-oxazoline) block copolymer. S4. In a solvent, a poly(2-ethyl-2-oxazoline) block copolymer is reacted with a sulfonyl lactone to obtain a poly(2-ethyl-2-oxazoline) block copolymer containing a sulfonyl betaine side group.

4. The method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 3, characterized in that, Step S1 includes one or more of the following conditions: i. The solvent is acetonitrile; the volume ratio of 2-ethyl-2-oxazoline to the solvent is 1-3 mol / L; ii. The initiator is methyl p-toluenesulfonate; the molar amount of the initiator is 0.5-2% of 2-ethyl-2-oxazoline; iii. The ring-opening polymerization reaction temperature is 120-160℃, the reaction time is 20-30h, and the reaction is carried out under the protection of a protective gas and under stirring conditions; the protective gas is nitrogen or argon. iv. After the ring-opening polymerization reaction, a terminator is added to terminate the reaction; the terminator is a KOH methanol solution with a mass concentration of 10%-40%.

5. The method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 3, characterized in that, Step S2 includes one or more of the following conditions: i. The solvent is N,N-dimethylformamide; the molar ratio of the terminal hydroxyl group of poly(2-ethyl-2-oxazoline) to the volume of the solvent is 0.1-1 mol / L; ii. The base is triethylamine; the molar amount of the base is 1-1.5 times the molar amount of poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups; iii. In step S2, the molar ratio of poly(2-ethyl-2-oxazoline) with terminal hydroxyl groups to acryloyl chloride is 1:1-1.5; iv. The reaction temperature is 50-70℃, the reaction time is 20-30h, and the reaction is carried out under stirring and protective gas protection; the protective gas is nitrogen or argon.

6. The method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 3, characterized in that, Step S3 includes one or more of the following conditions: i. The solvent is ethanol; the molar amount of poly(2-ethyl-2-oxazoline) with terminal double bonds and the volume ratio of the solvent are 0.005-0.01 mol / L; ii. The base is triethylamine; the molar amount of the base is 3-5% of the molar amount of poly(2-ethyl-2-oxazoline) with terminal double bonds; iii. Polymers with amino-terminated groups are polymers with amino-terminated groups at one end; polymers with amino-terminated groups are selected from polyethylene glycol with amino-terminated groups, polyethylene glycol-polylactic acid block copolymers with amino-terminated groups, polyethylene glycol-polycaprolactone block copolymers with amino-terminated groups, polyethylene glycol-polyglycolic acid block copolymers with amino-terminated groups, polyethylene glycol-polymethacrylic acid block copolymers with amino-terminated groups, or polyethylene glycol-polystyrene block copolymers with amino-terminated groups; iv. The molar ratio of poly(2-ethyl-2-oxazoline) with terminal double bonds to polymers with amino groups is 1:1; v. The reaction temperature is 40-80℃, the reaction time is 4-8h, and the reaction is carried out under stirring and protective gas protection; the protective gas is nitrogen or argon.

7. The method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 6, characterized in that, Polymers with amino-terminated groups are selected from one of the following: Where a, d, n, x, y, and z are integers ranging from 10 to 5000.

8. The method for preparing the poly(2-ethyl-2-oxazoline) block copolymer containing sulfonate betaine side groups according to claim 3, characterized in that, Step S4 includes one or more of the following conditions: i. The solvent is ethanol; the molar ratio of the poly(2-ethyl-2-oxazoline) block copolymer to the volume ratio of the solvent is 0.01-0.05 mol / L; ii. The sulfonyl lactone is any one of propanesulfonyl lactone, butanesulfonyl lactone, pentasulfonyl lactone, hexanesulfonyl lactone, heptasulfonyl lactone, or octanesulfonyl lactone. iii. The molar ratio of poly(2-ethyl-2-oxazoline) block copolymer to sulfonate lactone is 1:1-2; iv. The reaction temperature is 20-80℃, the reaction time is 4-8h, and the reaction is carried out under stirring conditions.

9. The application of the poly(2-ethyl-2-oxazoline) block copolymer containing a sulfonate betaine side group as described in claim 1 or 2, characterized in that, As a drug carrier to load drugs.

10. The application according to claim 9, characterized in that, The method for loading drugs as drug carriers is as follows: a poly(2-ethyl-2-oxazoline) block copolymer containing sulfobetaine side groups and the drug are dissolved in a solvent, transferred to a dialysis bag, and then placed in water for dialysis; the liquid in the dialysis bag is freeze-dried to achieve drug loading.

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