Sustained release implantable biodegradable stents loaded with antitumor active ingredients

Abstract

The application relates to the fields of biological medicine and high polymer materials, and discloses a sustained-release implant type biodegradable stent loaded with an antitumor active component, which is composed of polylactic acid-glycolic acid copolymer, doxorubicin hydrochloride, citric acid-terminated polyethylene glycol polymer, zinc acetate dihydrate and N-acetyl cysteine. The metastable complex structure is constructed by in-situ coordination reaction between the components, so that the rapid release of the water-soluble doxorubicin hydrochloride in the initial implantation stage is blocked. After implantation, N-acetyl cysteine is preferentially dissociated and released, so that the zinc ion coordination unsaturated sites are generated in the coordination network; with the hydrolysis of the polylactic acid-glycolic acid copolymer, the generated lactic acid molecules intervene in the above unsaturated sites to generate a competitive coordination reaction, so that the coordination skeleton is destroyed and the antitumor drug is released. The application realizes the synchronization of the drug release rate and the high polymer matrix degradation rate, and the acetate dissociated from the zinc acetate can effectively buffer the pH value of the degradation microenvironment.

Description

Technical Field

[0001] This invention relates to the fields of biomedicine and polymer materials technology, specifically to a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients. Background Technology

[0002] In the clinical treatment of tumors, surgical resection followed by local implantation of biodegradable scaffolds loaded with antitumor drugs is a routine treatment method. Polylactic acid-glycolic acid copolymer (PLA) is often used as the polymer matrix for scaffolds due to its biocompatibility and biodegradability. The traditional manufacturing process involves physically blending the antitumor drugs with the polymer matrix to create a homogeneous scaffold for implantation.

[0003] When the loaded antitumor drug is a water-soluble active ingredient such as doxorubicin hydrochloride, existing physically blended scaffolds have limitations in application. Due to the high water solubility of the drug itself, during the initial fluid infiltration phase after scaffold implantation, the drug distributed on the matrix surface and in the pores rapidly dissolves and diffuses extensively into surrounding tissues, resulting in a rapid initial drug release. This phenomenon can lead to excessively high drug concentrations in local tissues, causing toxic side effects and shortening the effective drug delivery cycle of the scaffold. After the initial rapid release phase, the drug release rate deeply embedded within the polymer matrix decreases significantly. The long bulk hydrolysis and degradation cycle of polylactic acid-glycolic acid copolymer makes it difficult to effectively release the drug from the scaffold in the middle and later stages, failing to maintain an effective drug concentration that continuously inhibits tumor cell growth, resulting in a time-separation between drug release and polymer matrix degradation.

[0004] Furthermore, polylactic acid-glycolic acid copolymers (PLA-GACs) hydrolyze in vivo to produce lactic acid and glycolic acid. These acidic monomeric products gradually accumulate in the local tissues at the implantation site, leading to a decrease in the pH of the microenvironment. This acidic environment easily triggers local inflammatory responses, and the acidic substances can also catalyze the breakage of the ester bonds within the PLA itself, accelerating the disintegration of the polymer matrix and compromising the stability of the stent-based sustained-release system. Summary of the Invention

[0005] The technical problem solved by this invention is that existing implantable stents for loading water-soluble antitumor drugs with polylactic acid-glycolic acid copolymers have the following limitations: rapid drug release in the early stage of implantation, slow release in the middle and late stages, and asynchronous drug degradation with the matrix. In addition, the acidic byproducts generated by polymer degradation are prone to causing local inflammatory reactions and autocatalytic degradation.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, employing the following technical solution:

[0008] The sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients is composed of the following raw materials in weight percentages, and the sum of the weight percentages of each raw material is 100%: polylactic acid-glycolic acid copolymer 70.0wt%~85.0wt%; doxorubicin hydrochloride 3.0wt%~8.0wt%; citric acid-terminated polyethylene glycol polymer 8.0wt%~15.0wt%; zinc acetate dihydrate 2.0wt%~5.0wt%; N-acetylcysteine ​​1.0wt%~3.0wt%.

[0009] By adopting the above technical solution, and through the chemical linkage design of multi-component in-situ coordination and matrix degradation product response, a uniform release effect that synchronizes drug release with stent degradation is achieved. The specific reaction mechanism and innovative process are divided into the following steps:

[0010] The first step involves constructing a metastable coordination network to block initial release. During stent formation, the terminal carboxyl groups of the citrate-terminated polyethylene glycol polymer, the thiol and carboxyl groups of N-acetylcysteine, undergo non-covalent coordination reactions with zinc ions dissociated from zinc acetate and the amino groups of doxorubicin hydrochloride, forming a metastable multi-component complex structure. This polymeric coordination network immobilizes doxorubicin hydrochloride molecules within the polylactic-co-glycolic acid copolymer matrix, reducing the diffusion rate of the water-soluble drug in an aqueous environment and preventing rapid release during the initial stage of stent implantation.

[0011] The second step involves the preferential dissociation of the sensitizer to form coordination unsaturated sites. N-acetylcysteine ​​is highly water-soluble and has a low coordination bond energy with zinc ions. After the stent is implanted in the body fluid environment, N-acetylcysteine ​​preferentially dissociates from the coordination network and diffuses into the surrounding medium. This dissociation process generates multiple zinc ion coordination unsaturated sites in the original supramolecular coordination network structure, providing reaction targets for the subsequent intervention of degradation products.

[0012] The third step involves degradation products triggering competitive coordination release of the drug. As the polylactic acid-glycolic acid copolymer matrix undergoes ester bond hydrolysis, lactic acid and glycolic acid molecules are continuously generated in the microenvironment. The resulting monomeric acid molecules bind to unsaturated zinc ion coordination sites left from the earlier removal of N-acetylcysteine, competing for coordination with the citrate-terminated polyethylene glycol polymer ligand. Ligand substitution leads to the gradual disintegration of the original coordination framework, allowing doxorubicin hydrochloride to detach from the metal nodes and dissolve. The drug release rate is driven by the acid production rate from the hydrolysis of the polymer matrix, synchronizing drug release with the degradation of the polymer matrix.

[0013] The fourth step is to buffer the pH of the microenvironment in situ. Free acetate ions generated during the coordination and recombination process of zinc acetate undergo proton exchange with lactic acid and glycolic acid generated from matrix degradation, neutralizing the acidic degradation products, maintaining the acid-base balance of the local microenvironment, and slowing down the acid-catalyzed accelerated degradation process of polylactic acid-glycolic acid copolymer.

[0014] Preferably, the citric acid-terminated polyethylene glycol polymer is a linear polymer obtained by esterification condensation reaction of anhydrous citric acid and polyethylene glycol with hydroxyl groups at both ends; wherein the weight average molecular weight of the polyethylene glycol is 1000 Da to 4000 Da.

[0015] By employing the above technical solution, the molecular weight of polyethylene glycol is controlled within the range of 1000 Da to 4000 Da, enabling the synthesized citric acid-terminated polyethylene glycol polymer to possess moderate coordination strength. This coordination strength is sufficient to immobilize doxorubicin hydrochloride in a neutral environment, while ensuring that the weakly bidentate lactic acid ligands generated from the degradation of polylactic acid-glycolic acid copolymer can undergo an effective displacement reaction under thermodynamic conditions, thus guaranteeing the normal operation of the degradation response triggering mechanism.

[0016] Preferably, the preparation method of citric acid-terminated polyethylene glycol polymer includes the following steps: dissolving anhydrous citric acid in anhydrous N,N-dimethylformamide, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine, and activating under nitrogen protection and 0°C ice-water bath conditions for 30 minutes to obtain an activated solution; uniformly adding polyethylene glycol pre-dissolved in anhydrous dichloromethane to the activated solution, stirring at 25°C in the dark for 36-60 hours, and obtaining the citric acid-terminated polyethylene glycol polymer after purification and drying; wherein, the molar ratio of anhydrous citric acid to polyethylene glycol is (8-12):1.

[0017] By employing the above technical solution, maintaining an excess of anhydrous citric acid ensures that only end-group esterification reactions occur at both ends of polyethylene glycol, preventing three-dimensional cross-linking and gelation caused by multifunctional group reactions. Low-temperature activation controls the reaction rate, reduces side reactions caused by carbodiimide activators, and improves the yield of linear macromolecular products.

[0018] Preferably, the polylactic acid-glycolic acid copolymer is a carboxyl-terminated random copolymer composed of lactic acid and glycolic acid in a molar ratio of 50:50 to 75:25, with a weight-average molecular weight of 20,000 Da to 50,000 Da.

[0019] By adopting the above technical solution, the polyester material with the above monomer ratio and molecular weight range has a moderate degradation cycle. The end carboxyl structure increases the polarity inside the matrix, which is beneficial to the uniform dispersion of the zinc-containing supramolecular coordination network inside the polymer continuous phase.

[0020] Preferably, in the raw material ratio, the feed molar ratio of zinc acetate dihydrate, citric acid-terminated polyethylene glycol polymer, doxorubicin hydrochloride and N-acetylcysteine ​​is controlled as (2.5~3.5):1:(1~1.5):(1.5~2.5).

[0021] By adopting the above technical solution, the specific molar ratio ensures that the system is in dynamic equilibrium after the reaction, forming a metastable state with macromolecular ligands as the main body and small molecule coordination nodes, avoiding drug release blockage due to excessive ligands or loose network structure due to insufficient cross-linking nodes.

[0022] Secondly, the present invention provides a method for preparing a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, using the following technical solution:

[0023] A method for preparing a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients includes the following steps:

[0024] S1 aqueous phase preparation: Doxorubicin hydrochloride, zinc acetate dihydrate and N-acetylcysteine ​​were dissolved in deionized water and stirred in the dark to obtain an aqueous solution;

[0025] S2 oil phase preparation: Polylactic acid-glycolic acid copolymer and citric acid-terminated polyethylene glycol polymer are dissolved in a volatile halogenated hydrocarbon solvent that is insoluble in water, and stirred in a closed container to obtain an oil phase solution;

[0026] S3 microemulsion preparation: An aqueous solution was injected into an oil phase solution in a shear-homogeneous state, followed by ultrasonic dispersion to obtain a metastable coordination network primary emulsion;

[0027] S4 curing molding: The colostrum is allowed to stand and evaporate to remove some of the solvent to obtain a cured preform. The preform is then vacuum freeze-dried to obtain a sustained-release implantable biodegradable scaffold loaded with anti-tumor active ingredients.

[0028] By employing the above technical solution, addressing the chemical limitation that inorganic salts and water-soluble drugs are difficult to dissociate and coordinate in pure organic solvents, a microemulsion solid-phase dispersion method combined with ultrasonic dispersion is used. This allows polar molecules in the aqueous phase to collide with macromolecular ligands in the oil phase at the two-phase interface, completing an in-situ complexation reaction. The ultrasonic cavitation effect provides energy for the chemical reaction, promoting the formation of highly dispersed coordination structure clusters at the micro-nano interface, solving the problems of uneven mixing and precipitation caused by differences in the solubility of each component. The curing step freezes the formed interfacial coordination structure in-situ within a continuous polymeric phase, achieving a homogeneous distribution of each component at the macroscopic level of the scaffold.

[0029] Preferably, in step S3, the aqueous phase solution is injected at a constant rate of 0.5 mL / min into the oil phase solution at a rotation speed of 10,000 rpm to 15,000 rpm.

[0030] By adopting the above technical solution, the combination of low injection rate and high shear speed causes the water phase to be dispersed into multiple droplets under the action of fluid shear force after entering the oil phase, thereby increasing the specific surface area of ​​the interface between the oil and water phases and increasing the probability of phase interface reaction.

[0031] Preferably, in step S3, the process parameters for ultrasonic dispersion are as follows: under the condition that the system temperature is kept below 15°C by ice bath cooling, the ultrasonic power is set to 150W~250W, the working mode is ultrasonic for 3 seconds and intermittent for 2 seconds, and the total working time lasts for 5~8 minutes.

[0032] By adopting the above technical solutions, intermittent ultrasound mode and external ice bath cooling can dissipate the heat energy generated by high-frequency mechanical oscillation, preventing local temperature rise in the system from causing thermal degradation of polymer chains or thermal inactivation of the antitumor component doxorubicin hydrochloride.

[0033] Preferably, in step S4, the specific method for static evaporation is as follows: the colostrum is transferred to a flat-bottomed mold, the liquid surface thickness is controlled to be 2mm~5mm, and static evaporation is carried out for 12~18 hours under normal pressure and light protection at 20℃~25℃.

[0034] By adopting the above technical solution, the atmospheric pressure and low temperature volatilization conditions allow the volatile solvent to slowly detach from the liquid matrix, giving the long chains of polylactic acid-glycolic acid copolymer sufficient time to entangle and shrink, thus preventing the solvent from rapidly boiling and forming structural defects inside the support.

[0035] Preferably, in step S4, the specific process parameters for vacuum freeze drying are as follows: after pre-freezing at -40°C for 4 hours, the vacuum is turned on to make the absolute pressure of the system lower than 10Pa, the temperature of the partition is raised from -40°C to 0°C at a heating rate of 0.5°C / min and held for 12 hours, and then raised to 25°C and held for 24 hours.

[0036] By employing the above technical solution, low-temperature pre-freezing transforms the liquid phase within the microemulsion into a solid state, and the subsequent programmed temperature rise process allows bound water and residual solvent to be directly sublimated and removed in a vacuum environment. The gentle drying conditions maintain the previously established non-covalent coordination network, ensuring the chemical stability of the scaffold's microstructure.

[0037] This invention provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients. It has the following beneficial effects:

[0038] 1. This invention involves an in-situ coordination reaction between doxorubicin hydrochloride, zinc acetate dihydrate, N-acetylcysteine, and citric acid-terminated polyethylene glycol polymer to form a multi-component complex structure within a polylactic-co-glycolic acid copolymer matrix. This complex structure reduces the free diffusion rate of water-soluble doxorubicin hydrochloride in an aqueous environment, inhibiting the rapid drug release during the initial implantation phase. Simultaneously, as the polylactic-co-glycolic acid copolymer undergoes hydrolysis, the resulting lactic acid competes for coordination with the unsaturated zinc ion sites left by the dissociation of N-acetylcysteine, triggering the disintegration of the coordination framework and the release of the drug. This achieves synchronization between the drug release rate and the degradation rate of the polymer matrix.

[0039] 2. This invention introduces N-acetylcysteine, which is highly water-soluble and has a low coordination bond energy, into the coordination system. After the stent is implanted in the body fluid environment, N-acetylcysteine ​​preferentially dissociates and releases, generating zinc ion coordination unsaturated sites in the original coordination network. This design of reserved reaction sites allows subsequently generated monomeric acid molecules with weak coordination ability to smoothly intervene in the coordination network and undergo displacement reactions, overcoming the defect of drug release and internal embedding in strong coordination systems, and ensuring the normal operation of the degradation product-triggered drug release mechanism.

[0040] 3. This invention uses zinc acetate dihydrate as the metal center donor for the coordination reaction. While participating in the construction of the cross-linked network, zinc acetate dissociates into acetate ions. These dissociated acetate ions can undergo proton exchange with the lactic acid and glycolic acid produced by the hydrolysis of the polylactic acid-glycolic acid copolymer, acting as an in-situ acid-base buffer within and around the scaffold. This buffering mechanism alleviates the local tissue inflammation caused by acidic degradation products and inhibits the catalytic acceleration of the degradation of the polylactic acid-glycolic acid copolymer matrix by acidic substances, maintaining the stability of the scaffold degradation cycle. Attached Figure Description

[0041] Figure 1 This is a process diagram for the preparation of the present invention. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The main raw materials and specifications used in the following examples and comparative examples are as follows. Conventional reaction reagents and solvents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0044] Polylactic acid-glycolic acid copolymer (PLA-GAC) is a carboxyl-terminated linear random copolymer, with repeating units composed of lactic acid and glycolic acid in a molar ratio of 50:50. Its weight-average molecular weight ranges from 20,000 to 50,000 Da, and its intrinsic viscosity ranges from 0.36 to 0.54 dL / g. Doxorubicin hydrochloride has the molecular formula C27H30ClNO11 and a purity greater than 99.0%. Zinc acetate dihydrate has the molecular formula C4H10O6Zn and a purity greater than 99.0%. N-acetylcysteine ​​has the molecular formula C5H9NO3S and a purity greater than 99.0%. Polyethylene glycol is a linear homopolymer with hydroxyl-terminated ends, and its weight-average molecular weights include 1000 Da, 2000 Da, and 4000 Da. Anhydrous citric acid has the molecular formula C6H8O7 and a purity greater than 99.5%.

[0045] Preparation Example 1:

[0046] This preparation example provides a method for preparing a citric acid-terminated polyethylene glycol polymer, comprising the following steps:

[0047] Weigh 20.0 mmol of anhydrous citric acid and dissolve it in 50 mL of anhydrous N,N-dimethylformamide. Add 6.0 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.6 mmol of 4-dimethylaminopyridine to the solution, and activate the mixture by magnetic stirring for 30 minutes under dry nitrogen at a flow rate of 20 mL / min and an ice-water bath at 0 °C. Dissolve 2.0 mmol of polyethylene glycol with a weight-average molecular weight of 2000 Da in 20 mL of anhydrous dichloromethane beforehand, and add it dropwise to the activated solution at a rate of 1 drop / second using a constant pressure dropping funnel. After the addition is complete, transfer the reaction system to a 25 °C environment and stir continuously at a constant temperature for 48 hours under light protection and nitrogen protection. After the reaction is completed, remove the dichloromethane from the mixture using a rotary evaporator at 40 °C and an absolute pressure of 0.02 MPa. The remaining liquid was added dropwise at a uniform rate to 500 mL of anhydrous diethyl ether at -20 °C, resulting in a white precipitate. After standing for 1 hour, the precipitate was collected by vacuum filtration through a sintered glass funnel and washed three times with anhydrous diethyl ether at the same temperature. The collected solid product was placed in a vacuum drying oven and dried at 25 °C and 0.01 MPa absolute pressure for 24 hours to obtain purified citric acid-terminated polyethylene glycol polymer powder.

[0048] Preparation Example 2:

[0049] This preparation example provides a method for preparing a citric acid-terminated polyethylene glycol polymer, comprising the following steps:

[0050] Weigh 24.0 mmol of anhydrous citric acid and dissolve it in 50 mL of anhydrous N,N-dimethylformamide. Add 9.0 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.9 mmol of 4-dimethylaminopyridine to the solution, and activate the mixture by magnetic stirring for 30 minutes under dry nitrogen at a flow rate of 20 mL / min and an ice-water bath at 0 °C. Dissolve 3.0 mmol of polyethylene glycol with a weight-average molecular weight of 1000 Da in 20 mL of anhydrous dichloromethane beforehand, and add it dropwise to the activated solution at a rate of 1 drop / second using a constant pressure dropping funnel. After the addition is complete, transfer the reaction system to a 25 °C environment and stir continuously at a constant temperature for 36 hours under light protection and nitrogen protection. After the reaction is completed, remove the dichloromethane from the mixture using a rotary evaporator at 40 °C and an absolute pressure of 0.02 MPa. The remaining liquid was added dropwise at a uniform rate to 500 mL of anhydrous diethyl ether at -20 °C, resulting in a white precipitate. After standing for 1 hour, the precipitate was collected by vacuum filtration through a sintered glass funnel and washed three times with anhydrous diethyl ether at the same temperature. The collected solid product was placed in a vacuum drying oven and dried at 25 °C and 0.01 MPa absolute pressure for 24 hours to obtain purified citric acid-terminated polyethylene glycol polymer powder.

[0051] Preparation Example 3:

[0052] This preparation example provides a method for preparing a citric acid-terminated polyethylene glycol polymer, comprising the following steps:

[0053] Weigh 12.0 mmol of anhydrous citric acid and dissolve it in 50 mL of anhydrous N,N-dimethylformamide. Add 3.0 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.3 mmol of 4-dimethylaminopyridine to the solution, and activate the mixture by magnetic stirring for 30 minutes under dry nitrogen at a flow rate of 20 mL / min and an ice-water bath at 0 °C. Dissolve 1.0 mmol of polyethylene glycol with a weight-average molecular weight of 4000 Da in 20 mL of anhydrous dichloromethane beforehand, and add it dropwise to the activated solution at a rate of 1 drop / second using a constant pressure dropping funnel. After the addition is complete, transfer the reaction system to a 25 °C environment and stir continuously at a constant temperature for 60 hours under light protection and nitrogen protection. After the reaction is completed, remove the dichloromethane from the mixture using a rotary evaporator at 40 °C and an absolute pressure of 0.02 MPa. The remaining liquid was added dropwise at a uniform rate to 500 mL of anhydrous diethyl ether at -20 °C, resulting in a white precipitate. After standing for 1 hour, the precipitate was collected by vacuum filtration through a sintered glass funnel and washed three times with anhydrous diethyl ether at the same temperature. The collected solid product was placed in a vacuum drying oven and dried at 25 °C and 0.01 MPa absolute pressure for 24 hours to obtain purified citric acid-terminated polyethylene glycol polymer powder.

[0054] Reference Figure 1 Example 1:

[0055] This embodiment provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, including the following steps:

[0056] Weigh 34 mg of doxorubicin hydrochloride, 32 mg of zinc acetate dihydrate, and 16 mg of N-acetylcysteine, add them to 2.0 mL of deionized water, and stir magnetically at 25°C in the dark for 30 minutes until completely dissolved to form an aqueous solution. Weigh 803 mg of polylactic acid-glycolic acid copolymer and 115 mg of the citric acid-terminated polyethylene glycol polymer obtained in Preparation Example 1, add them to 17.5 mL of anhydrous dichloromethane, and stir magnetically at 25°C for 2 hours at a stirring speed of 500 rpm to form a homogeneous and transparent oil phase solution. Inject the above aqueous solution into the oil phase solution, which is in a high-speed shear homogenization state, at a rate of 0.5 mL / min using a micro-injection pump. The shear homogenization speed is set to 12500 rpm. Immediately after injection, the mixture was transferred to a probe-type ultrasonic disruptor for ultrasonic dispersion under ice bath cooling, maintaining the system temperature below 15°C. The ultrasonic power was set to 200W, with a working mode of 3 seconds of ultrasonication followed by 2 seconds of intermittent operation, for a total working time of 6 minutes, yielding a metastable coordination network pre-emulsion. The ultrasonically dispersed pre-emulsion was transferred to a flat-bottomed PTFE mold, with the liquid surface thickness controlled at 3mm. The mold was placed at 25°C under normal pressure and in the dark for 15 hours to allow for evaporation, resulting in a cured preform. The preform was then transferred to a vacuum freeze dryer and pre-frozen at -40°C for 4 hours. Subsequently, the vacuum was turned on to reduce the system absolute pressure to below 10Pa. The temperature of the partition was increased from -40°C to 0°C at a rate of 0.5°C / min and maintained for 12 hours, then increased to 25°C and maintained for 24 hours. The mold was then removed, yielding a macroscopically homogeneous biodegradable scaffold.

[0057] Example 2:

[0058] This embodiment provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, including the following steps:

[0059] Weigh 35 mg of doxorubicin hydrochloride, 33 mg of zinc acetate dihydrate, and 15 mg of N-acetylcysteine, add them to 1.5 mL of deionized water, and stir magnetically at 25°C in the dark for 30 minutes until completely dissolved to form an aqueous solution. Weigh 837 mg of polylactic acid-glycolic acid copolymer and 80 mg of the citric acid-terminated polyethylene glycol polymer obtained in Preparation Example 2, add them to 15.0 mL of anhydrous dichloromethane, and stir magnetically at 25°C for 2 hours at a stirring speed of 500 rpm to form a homogeneous and transparent oil phase solution. Inject the above aqueous solution into the oil phase solution, which is in a high-speed shear homogenization state, at a rate of 0.5 mL / min using a micro-injection pump. The shear homogenization speed is set to 10,000 rpm. Immediately after injection, the mixture was transferred to a probe-type ultrasonic disruptor for ultrasonic dispersion under ice bath cooling, maintaining the system temperature below 15°C. The ultrasonic power was set to 150W, with a working mode of 3 seconds of ultrasonication followed by 2 seconds of intermittent operation, for a total working time of 5 minutes, resulting in a metastable coordination network pre-emulsion. The ultrasonically dispersed pre-emulsion was transferred to a flat-bottomed PTFE mold, with the liquid surface thickness controlled at 2mm. The mold was placed at 20°C under normal pressure and in the dark for 12 hours to allow for evaporation, resulting in a cured preform. The preform was then transferred to a vacuum freeze dryer and pre-frozen at -40°C for 4 hours. Subsequently, the vacuum was turned on to reduce the system absolute pressure to below 10Pa. The temperature of the partition was increased from -40°C to 0°C at a heating rate of 0.5°C / min and maintained for 12 hours, then increased to 25°C and maintained for 24 hours. The mold was then removed, yielding a macroscopically homogeneous biodegradable scaffold.

[0060] Example 3:

[0061] This embodiment provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, including the following steps:

[0062] Weigh 30 mg of doxorubicin hydrochloride, 26 mg of zinc acetate dihydrate, and 14 mg of N-acetylcysteine, add them to 2.5 mL of deionized water, and stir magnetically at 25°C in the dark for 30 minutes until completely dissolved to form an aqueous solution. Weigh 780 mg of polylactic acid-glycolic acid copolymer and 150 mg of the citric acid-terminated polyethylene glycol polymer obtained in Preparation Example 3, add them to 20.0 mL of anhydrous dichloromethane, and stir magnetically at 25°C for 2 hours at a stirring speed of 500 rpm to form a homogeneous and transparent oil phase solution. Inject the above aqueous solution into the oil phase solution, which is in a high-speed shear homogenization state, at a rate of 0.5 mL / min using a micro-injection pump. The shear homogenization speed is set to 15000 rpm. Immediately after injection, the mixture was transferred to a probe-type ultrasonic disruptor for ultrasonic dispersion under ice bath cooling, maintaining the system temperature below 15°C. The ultrasonic power was set to 250W, with a working mode of 3 seconds of ultrasonication followed by 2 seconds of intermittent operation, for a total working time of 8 minutes, resulting in a metastable coordination network pre-emulsion. The ultrasonically dispersed pre-emulsion was transferred to a flat-bottomed PTFE mold, with the liquid surface thickness controlled at 5mm. The mold was placed at 25°C under normal pressure and in the dark for 18 hours to allow for evaporation, resulting in a cured preform. The preform was then transferred to a vacuum freeze dryer and pre-frozen at -40°C for 4 hours. Subsequently, the vacuum was turned on to reduce the system absolute pressure to below 10Pa. The temperature of the partition was increased from -40°C to 0°C at a heating rate of 0.5°C / min and maintained for 12 hours, then increased to 25°C and maintained for 24 hours. The mold was then removed, yielding a macroscopically homogeneous biodegradable scaffold.

[0063] Example 4:

[0064] This embodiment provides a sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, including the following steps:

[0065] Weigh 34 mg of doxorubicin hydrochloride, 32 mg of zinc acetate dihydrate, and 16 mg of N-acetylcysteine, add them to 2.0 mL of deionized water, and stir magnetically at 25°C in the dark for 30 minutes until completely dissolved to form an aqueous solution. Weigh 803 mg of polylactic acid-glycolic acid copolymer and 115 mg of the citric acid-terminated polyethylene glycol polymer obtained in Preparation Example 1, add them to 17.5 mL of anhydrous dichloromethane, and stir magnetically at 25°C for 2 hours at a stirring speed of 500 rpm to form a homogeneous and transparent oil phase solution. Inject the above aqueous solution into the oil phase solution, which is in a high-speed shear homogenization state, at a rate of 0.5 mL / min using a micro-injection pump. The shear homogenization speed is set to 15000 rpm. Immediately after injection, the mixture was transferred to a probe-type ultrasonic disruptor for ultrasonic dispersion under ice bath cooling, maintaining the system temperature below 15°C. The ultrasonic power was set to 250W, with a working mode of 3 seconds of ultrasonication followed by 2 seconds of intermittent operation, for a total working time of 8 minutes, resulting in a metastable coordination network pre-emulsion. The ultrasonically dispersed pre-emulsion was transferred to a flat-bottomed PTFE mold, with the liquid surface thickness controlled at 3mm. The mold was placed at 20°C under normal pressure and in the dark for 18 hours to allow for evaporation, resulting in a cured preform. The preform was then transferred to a vacuum freeze dryer and pre-frozen at -40°C for 4 hours. Subsequently, the vacuum was turned on to reduce the system absolute pressure to below 10Pa. The temperature of the partition was increased from -40°C to 0°C at a heating rate of 0.5°C / min and maintained for 12 hours, then increased to 25°C and maintained for 24 hours. The mold was then removed, yielding a macroscopically homogeneous biodegradable scaffold.

[0066] Comparative Example 1:

[0067] Compared with Example 1, the difference is that the formulation does not contain zinc acetate dihydrate, N-acetylcysteine ​​and citric acid-terminated polyethylene glycol polymer, only doxorubicin hydrochloride is dissolved in the aqueous phase, and only polylactic acid-glycolic acid copolymer is dissolved in the oil phase. In order to maintain the consistency of the total mass of the stent, the amount of polylactic acid-glycolic acid copolymer is adjusted to 966 mg, and the rest are the same.

[0068] Comparative Example 2:

[0069] Compared with Example 1, the difference is that the formulation does not contain N-acetylcysteine, and in order to maintain the consistency of the total scaffold mass, the amount of polylactic acid-glycolic acid copolymer is adjusted to 819 mg, while the rest are the same.

[0070] Comparative Example 3:

[0071] Compared with Example 1, the difference is that phytic acid is used to replace citric acid-terminated polyethylene glycol polymer in the oil phase in an equimolar amount. Due to the difference in molar mass of the substances, the amount of polylactic acid-glycolic acid copolymer is adjusted to make up for the difference in the total mass of the stent. All other aspects are the same.

[0072] Comparative Example 4:

[0073] Compared with Example 1, the difference is that the formulation does not contain zinc acetate dihydrate, and in order to maintain the consistency of the total mass of the stent, the amount of polylactic acid-glycolic acid copolymer is adjusted to 835 mg, while the rest are the same.

[0074] Comparative Example 5:

[0075] Compared with Example 1, the difference is that unmodified pure polyethylene glycol with a weight average molecular weight of 2000 Da is used to replace the citric acid-terminated polyethylene glycol polymer in the oil phase by an equal mass, while all other aspects are the same.

[0076] Test Example 1:

[0077] Three equal-mass biodegradable scaffolds prepared in Examples 1, 2, and 3 were used. Each scaffold was placed in a light-protected centrifuge tube containing 50 mL of standard phosphate buffer (pH 7.4). The centrifuge tubes were placed in a constant-temperature shaking incubator at 37°C and 100 rpm. On days 1, 3, and 7, 1 mL of release medium was aspirated, and immediately 1 mL of fresh phosphate buffer at the same temperature was added to the centrifuge tube. The concentrations of N-acetylcysteine ​​and doxorubicin hydrochloride in the sample solution were simultaneously detected using dual-channel high-performance liquid chromatography (HPLC) to calculate the cumulative release rate of the first stage.

[0078] After testing on day 7, remove the support tube and wash its surface with deionized water, then blot dry with filter paper. Place the support tube into a centrifuge tube containing 50 mL of 50 mM lactic acid solution and incubate at 37°C with shaking. At 24, 48, and 72 hours after incorporation into the lactic acid solution, aspirate 1 mL of release medium and replenish with 1 mL of fresh lactic acid solution at the same temperature. Analyze the concentration of doxorubicin hydrochloride in the sample using high-performance liquid chromatography (HPLC). Calculate the cumulative release rate for the second stage based on the residual doxorubicin hydrochloride concentration on day 7 of the first stage.

[0079] Table 1. Test data on the cumulative release rate of each component in the release medium at different stages.

[0080] Analysis Project Sampling time Example 1 (%) Comparative Example 2 (%) Comparative Example 3 (%) Phase 1 N-acetylcysteine ​​cumulative release rate Day 1 63.2 Not detected 58.7 Phase 1 N-acetylcysteine ​​cumulative release rate Day 3 79.5 Not detected 76.4 Phase 1 N-acetylcysteine ​​cumulative release rate Day 7 88.1 Not detected 84.9 Phase 1 Cumulative Release Rate of Doxorubicin Hydrochloride Day 1 1.8 1.4 1.2 Phase 1 Cumulative Release Rate of Doxorubicin Hydrochloride Day 3 2.6 2.1 1.5 Phase 1 Cumulative Release Rate of Doxorubicin Hydrochloride Day 7 4.3 3.5 2.1 Phase II Doxorubicin Hydrochloride Cumulative Release Rate 24 hours 15.6 5.2 1.8 Phase II Doxorubicin Hydrochloride Cumulative Release Rate 48 hours 31.4 8.7 2.6 Phase II Doxorubicin Hydrochloride Cumulative Release Rate 72nd hour 48.9 11.3 3.1

[0081] In Example 1, after 7 days of testing in a phosphate buffer environment, the cumulative release rate of doxorubicin hydrochloride was 4.3%. The experimental data indicate that the coordination network formed by the components confines doxorubicin hydrochloride within the polylactic-co-glycolic acid copolymer, preventing rapid release of doxorubicin hydrochloride in the initial stage of the test. In Example 1, the cumulative release rate of N-acetylcysteine ​​in phosphate buffer on day 7 was 88.1%. N-acetylcysteine ​​preferentially dissociates from the coordination network and enters the release medium; the dissociation process forms zinc ion coordination unsaturated sites in the original coordination network structure.

[0082] In Example 1, after being transferred to a lactic acid aqueous solution, the release rate of doxorubicin hydrochloride increased, reaching a cumulative release rate of 48.9% within 72 hours. The lactic acid aqueous solution simulated the acidic environment generated by the hydrolysis of polylactic acid-glycolic acid copolymer. The test data indicated that lactic acid molecules entered the coordination unsaturated sites left by the dissociation of N-acetylcysteine, undergoing a competitive coordination reaction. This disrupted the coordination structure formed by the citric acid-terminated polyethylene glycol polymer, zinc ions, and doxorubicin hydrochloride, leading to the release of doxorubicin hydrochloride from the polymer matrix.

[0083] Comparative Example 2 did not contain N-acetylcysteine, and no N-acetylcysteine ​​was shed in the first stage, resulting in the absence of coordinating unsaturated sites. After 72 hours in a lactic acid aqueous solution, Comparative Example 2 showed a cumulative release rate of 11.3% for doxorubicin hydrochloride, lower than the 48.9% in Example 1. These results indicate that the absence of N-acetylcysteine ​​prevents lactic acid molecules from entering the coordination network, causing doxorubicin hydrochloride to remain within the polylactic-co-glycolic acid copolymer and thus prevent its release.

[0084] In Comparative Example 3, phytic acid was used instead of citric acid-terminated polyethylene glycol (PEG). The cumulative release rate of N-acetylcysteine ​​in the first stage was 84.9%, but in a lactic acid aqueous solution, the cumulative release rate of doxorubicin hydrochloride was only 3.1% after 72 hours. Phytic acid contains multiple phosphate groups, and its coordination ability with zinc ions is greater than that of lactic acid. The test results indicate that even with unsaturated coordination sites in the coordination network, lactic acid molecules cannot displace phytic acid and disrupt the coordination structure. Using citric acid-terminated PEG instead of phytic acid satisfies the chemical reaction conditions for lactic acid molecules to compete for coordination and release doxorubicin hydrochloride.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients, characterized in that, It consists of the following raw materials by weight percentage, and the sum of the weight percentages of each raw material is 100%: Polylactic acid-glycolic acid copolymer 70.0wt%~85.0wt%; Doxorubicin hydrochloride 3.0wt%~8.0wt%; Citric acid-terminated polyethylene glycol polymer 8.0wt%~15.0wt%; Zinc acetate dihydrate 2.0wt%~5.0wt%; N-acetylcysteine ​​1.0wt%~3.0wt%.

2. The sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 1, characterized in that, The citric acid-terminated polyethylene glycol polymer is a linear polymer obtained by esterification condensation reaction of anhydrous citric acid and polyethylene glycol with hydroxyl groups at both ends; wherein the weight average molecular weight of the polyethylene glycol is 1000 Da to 4000 Da.

3. The sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 2, characterized in that, The preparation method of the citric acid-terminated polyethylene glycol polymer includes the following steps: Anhydrous citric acid was dissolved in anhydrous N,N-dimethylformamide, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-dimethylaminopyridine were added. The mixture was activated for 30 minutes under nitrogen protection and an ice-water bath at 0°C to obtain an activated solution. Polyethylene glycol, which had been pre-dissolved in anhydrous dichloromethane, was added dropwise to the activated solution at a uniform rate. The mixture was stirred at 25°C in the dark for 36-60 hours. After purification and drying, the citric acid-terminated polyethylene glycol polymer was obtained. The molar ratio of anhydrous citric acid to polyethylene glycol is (8~12):

1.

4. The sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 1, characterized in that, The polylactic acid-glycolic acid copolymer is a carboxyl-terminated random copolymer composed of lactic acid and glycolic acid in a molar ratio of 50:50 to 75:25, with a weight-average molecular weight of 20,000 Da to 50,000 Da.

5. The sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 1, characterized in that, In the raw material ratio, the feed molar ratio of zinc acetate dihydrate, citric acid-terminated polyethylene glycol polymer, doxorubicin hydrochloride and N-acetylcysteine ​​is controlled as (2.5~3.5):1:(1~1.5):(1.5~2.5).

6. The method for preparing the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of aqueous phase: Doxorubicin hydrochloride, zinc acetate dihydrate and N-acetylcysteine ​​were dissolved in deionized water and stirred in the dark to obtain an aqueous solution; S2. Oil phase preparation: Polylactic acid-glycolic acid copolymer and citric acid-terminated polyethylene glycol polymer are dissolved in a water-insoluble volatile halogenated hydrocarbon solvent and stirred in a closed container to obtain an oil phase solution. S3. Microemulsion preparation: The aqueous phase solution is injected into the oil phase solution which is in a shear homogeneous state, and then ultrasonically dispersed to obtain a metastable coordination network primary emulsion. S4. Curing and molding: The promulgated material is allowed to stand to evaporate and remove some of the solvent to obtain a cured preform. The preform is then subjected to vacuum freeze-drying to obtain the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients.

7. The method for preparing the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 6, characterized in that, In step S3, the aqueous phase solution is injected at a constant rate of 0.5 mL / min into the oil phase solution at a rotation speed of 10,000 rpm to 15,000 rpm.

8. The method for preparing the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients as described in claim 6, characterized in that, In step S3, the process parameters for ultrasonic dispersion are as follows: under the condition that the system temperature is kept below 15°C by ice bath cooling, the ultrasonic power is set to 150W~250W, the working mode is ultrasonic for 3 seconds and intermittent for 2 seconds, and the total working time lasts for 5~8 minutes.

9. The method for preparing the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 6, characterized in that, In step S4, the specific method for static evaporation is as follows: transfer the colostrum to a flat-bottomed mold, control the liquid surface thickness to 2mm~5mm, and allow it to stand and evaporate for 12~18 hours under normal pressure and light protection at 20℃~25℃.

10. The method for preparing the sustained-release implantable biodegradable scaffold loaded with antitumor active ingredients according to claim 6, characterized in that, In step S4, the specific process parameters for vacuum freeze drying are as follows: after pre-freezing at -40℃ for 4 hours, the vacuum is turned on to make the absolute pressure of the system lower than 10Pa, and the temperature of the partition is raised from -40℃ to 0℃ at a heating rate of 0.5℃ / min and held for 12 hours, then raised to 25℃ and held for 24 hours.

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