Embolism microsphere and preparation method thereof

Abstract

The invention relates to an embolism microsphere and a preparation method thereof, and belongs to the technical field of embolism microspheres. The embolism microsphere comprises a double-network structure formed by interpenetration of a first network and a second network, the first network is formed by crosslinking of covalent bonds, and the second network is formed by crosslinking of ionic bonds; wherein the cross-linking component of the first network comprises methacrylated gelatin and a hydrophilic monomer with at least one polymerizable double bond, and the cross-linking component of the second network comprises sodium alginate and multivalent metal ion salt. By designing the first network cross-linked by covalent bonds and the second network cross-linked by ionic bonds, a dual-network interpenetrating structure with gradient degradation characteristics is constructed, controllable release of drugs can be effectively realized, and the treatment effect can be further improved.

Description

Technical Field

[0001] This application relates to the field of embolization microsphere technology, and particularly to an embolization microsphere and its preparation method. Background Technology

[0002] In the field of drug delivery, drug-loadable embolizable microspheres are key carriers for achieving precise drug delivery. These microspheres can encapsulate or adsorb drugs internally, blocking blood supply to lesions through vascular embolization while slowly releasing the drugs to exert a therapeutic effect. The degradation rate of the microspheres directly affects the drug release rate, thus determining the therapeutic efficacy.

[0003] However, the degradation rate of existing embolization microspheres is usually uncontrollable, exhibiting overall disintegration degradation, that is, the sudden loss of structural integrity during the degradation process, leading to sudden drug release and affecting the therapeutic effect. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides an embolization microsphere and its preparation method, aiming to effectively solve the problem that existing drug-loaded embolization microspheres cannot achieve controlled drug release through degradation. In a first aspect, embodiments of this application provide an embolization microsphere comprising a dual-network structure formed by interpenetrating a first network and a second network, wherein the first network is formed by covalent cross-linking and the second network is formed by ionic cross-linking; wherein the cross-linking components of the first network include methacrylamide gelatin and a hydrophilic monomer having at least one polymerizable double bond, and the cross-linking components of the second network include sodium alginate and a polyvalent metal ion salt. In the aforementioned technical solution, this application utilizes a dual-network interpenetrating structure with gradient degradation characteristics to effectively achieve controlled drug release. The first network, primarily composed of methacrylamide gelatin (GelMA), possesses excellent biocompatibility and enzymatic degradation properties. By selecting hydrophilic monomers for covalent cross-linking with methacrylamide gelatin, the stretchability of the hydrophilic monomers reduces the porosity between the cross-linked networks, thereby delaying the sustained-release effect of the drug loaded in the first network. Covalent cross-linking effectively improves network stability, thereby enhancing the overall mechanical strength of the microspheres. Furthermore, the covalently cross-linked network structure exhibits strong stability and is primarily degraded through enzymatic processes (such as matrix metalloproteinases and collagenases). These enzymatic processes require the gradual breaking of peptide and carbon-carbon bonds, resulting in a relatively long degradation half-life and a slow degradation mechanism. The second network is formed by ionic cross-linking of sodium alginate and polyvalent metal ions. In a physiological environment, the polyvalent metal ions contained within are degraded by Na+ in body fluids. + K + The competitive binding of cations leads to easy dissociation of ionic bonds, and the network structure disintegrates rapidly as the ionic bonds break. Therefore, the degradation half-life is short, exhibiting a rapid degradation mechanism.

[0005] Therefore, by utilizing the porous cross-linked structure of the dual-network structure, the embolization microspheres can efficiently and stably load a variety of drugs through physical embedding or electrostatic adsorption. On the one hand, by utilizing the energy difference between ionic bonds (low bond energy) and covalent bonds (high bond energy), the second network is ensured to degrade before the first network at the bond energy level. On the other hand, the interpenetrating structure of the dual networks can prevent the second network from falling off prematurely, further ensuring the orderliness of the entire degradation process, thereby effectively achieving the controllable release of drugs.

[0006] Furthermore, the dual-network interpenetrating structure endows the microspheres with excellent mechanical strength and elasticity, allowing them to remain stable at the embolization site for extended periods without easily deforming or breaking and displacing. The controlled drug release, achieved through gradient degradation and excellent mechanical stability, effectively improves the safety and long-term efficacy of this embolization microsphere. Secondly, embodiments of this application provide a method for preparing the embolic microspheres provided in the first aspect of this application, comprising the following steps: S1: Methacrylamide gelatin, a hydrophilic monomer with at least one polymerizable double bond, sodium alginate, and an initiator are dissolved and mixed in water to obtain an aqueous phase; S2: Mixing the aqueous phase and the oil phase to form a water-in-oil suspension system; S3: Add an aqueous solution of a polyvalent metal ion salt to an oil-in-water suspension system, and obtain embolic microspheres after a cross-linking reaction.

[0007] In the above technical solution, by selecting methacrylamide gelatin, a hydrophilic monomer with at least one polymerizable double bond, sodium alginate, and a multivalent metal ion salt aqueous solution as raw materials, methacrylamide gelatin has good biocompatibility and enzymatic degradation characteristics, and contains a large number of polymerizable methacrylyl groups, which can undergo free radical copolymerization with the hydrophilic monomer to covalently crosslink and form a first network (i.e., a covalent network); while sodium alginate molecules contain a large number of carboxyl groups, which can combine with multivalent metal ions through ionic coordination and crosslink through ionic bonds to form a second network (i.e., a physical network). In the water-in-oil reverse suspension polymerization system, the two crosslinked networks interpenetrate and entwine to form a double-network interpenetrating structure.

[0008] The porous network structure of the dual-network interpenetrating structure enables microspheres to efficiently and stably load a variety of drugs through physical encapsulation and electrostatic adsorption. Since the first network, which is covalently cross-linked, can slowly degrade in the in vivo enzymatic environment, while the second network, which is ionicly cross-linked, can rapidly dissociate in the in vivo environment, the gradient degradation characteristics of the first and second networks can effectively achieve controlled drug release.

[0009] Furthermore, by introducing hydrophilic monomers into the first network and copolymerizing them with methacrylamide gelatin, the stability of the first network can be effectively improved. This further facilitates interpenetration with the second network, allowing the microspheres to possess both good mechanical strength and elasticity, ensuring long-term stability at the embolization site and preventing deformation or breakage leading to displacement. The controlled drug release through gradient degradation, combined with excellent mechanical stability, effectively enhances the safety and long-term effectiveness of the treatment.

[0010] This preparation method can simultaneously form two cross-linked networks using an oil-in-water system, thereby forming a double-network interpenetrating structure. It does not require stepwise reactions, is simple to operate, and is conducive to large-scale application. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a process flow diagram of a method for preparing embolization microspheres provided in an embodiment of this application. Detailed Implementation

[0013] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the embolic microspheres and their preparation methods of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0014] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", refer to the three cases where it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2".

[0015] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0016] In medical fields such as interventional oncology and long-acting drug delivery for chronic diseases, drug-loadable embolizable microspheres are key carriers for achieving precise drug delivery. These microspheres can encapsulate or adsorb drugs internally, blocking blood supply to lesions through vascular embolization while slowly releasing the drug to exert a therapeutic effect. The matching of the microsphere's degradation rate and drug release rate directly determines the therapeutic effect: if the microspheres degrade too quickly, a large amount of drug will be released in a short period (i.e., burst release), which may not only exceed the lesion's tolerable dose and cause toxic side effects, but also lead to rapid drug depletion and an inability to maintain a sustained effect; if the microspheres degrade too slowly, the drug release cycle is too long, which may not only miss the critical window for lesion treatment, but also increase safety risks due to prolonged drug retention in the body.

[0017] The degradation characteristics of existing microspheres are one of the core technical challenges: most microspheres exhibit overall disintegration degradation, meaning they suddenly lose their structural integrity during degradation. This can lead to a sudden release of the drug in the early stages due to the instability of the microsphere structure (a large amount of drug is released in a short period of time, causing local toxicity), and then the drug cannot be released continuously due to the rapid disintegration of the microsphere in the later stages. A few microspheres with slow degradation capabilities have poor uniformity in degradation rate, making it difficult to match the changes in drug demand during the treatment cycle of the lesion, and failing to achieve gradient control of on-demand drug release, thus affecting the safety and long-term efficacy of the treatment.

[0018] In addition, conventional hydrophilic network microspheres (such as pure gelatin-sodium alginate microspheres) have weak intermolecular forces and are prone to deformation or breakage under the impact of blood flow in blood vessels, which can lead to displacement of the embolization site, failure to stably block the blood supply to the lesion, weaken the embolization treatment effect, and increase the treatment risk. Based on this, embodiments of this application provide an embolization microsphere comprising a dual-network structure formed by interpenetration of a first network and a second network. The first network is formed by covalent cross-linking, and the second network is formed by ionic cross-linking. The cross-linking components of the first network include methacryloyl gelatin and a hydrophilic monomer with at least one polymerizable double bond, and the cross-linking components of the second network include sodium alginate and a polyvalent metal ion salt.

[0019] In this application, "methacrylamide gelatin" (GelMA) is a modified product obtained by grafting methacrylic anhydride onto gelatin. It possesses good biocompatibility and enzymatic degradation characteristics, and its molecular chain contains a large number of polymerizable methacrylamide groups (C=C double bonds). By selecting hydrophilic monomers for covalent cross-linking with methacrylamide gelatin, the stability of the covalent cross-linked network can be effectively improved. Furthermore, the network structure formed by covalent cross-linking is highly stable and is mainly degraded through enzymatic hydrolysis (such as matrix metalloproteinases and collagenases). The enzymatic hydrolysis process requires the gradual cleavage of peptide bonds and carbon-carbon bonds, resulting in a relatively long degradation half-life and exhibiting a slow degradation mechanism. Sodium alginate, on the other hand, contains a large number of carboxyl groups on its molecular chain, which are ionicly cross-linked with polyvalent metal ions to form a second cross-linked network. In a physiological environment, the polyvalent metal ions it contains are degraded by Na+ in body fluids. + K + The competitive binding of cations leads to easy dissociation of ionic bonds, and the network structure disintegrates rapidly as the ionic bonds break. Therefore, the degradation half-life is short, exhibiting a rapid degradation mechanism.

[0020] Therefore, by utilizing the porous cross-linked structure of the dual-network structure, the embolization microspheres can efficiently and stably load a variety of drugs through physical embedding or electrostatic adsorption. On the one hand, by utilizing the energy difference between ionic bonds (low bond energy) and covalent bonds (high bond energy), the second network is ensured to degrade before the first network at the bond energy level. On the other hand, the interpenetrating structure of the dual networks can prevent the second network from falling off prematurely, further ensuring the orderliness of the entire degradation process, thereby effectively achieving the controllable release of drugs.

[0021] Furthermore, the dual-network interpenetrating structure endows the microspheres with excellent mechanical strength and elasticity, allowing them to remain stable at the embolization site for extended periods without easily deforming or breaking and displacing. The controlled drug release, achieved through gradient degradation and excellent mechanical stability, effectively improves the safety and long-term efficacy of this embolization microsphere. The features and performance of the technical solution of this application will be further described in detail below with reference to the embodiments.

[0022] Figure 1 For a process flow diagram of a method for preparing embolic microspheres provided in this application embodiment, please refer to [link / reference]. Figure 1 The preparation method of the embolic microspheres includes the following steps: S1: Methacrylamide gelatin, a hydrophilic monomer with at least one polymerizable double bond, sodium alginate, and an initiator are dissolved and mixed in water to obtain an aqueous phase.

[0023] In some embodiments, the hydrophilic monomer includes at least one of N-acryloylglycine (NAGA), acrylate PEG derivatives, acrylamide PEG derivatives, or maleimide PEG derivatives. These hydrophilic monomers all contain strong hydrophilic groups (such as -COOH, -OH, amide groups) and have good compatibility with methacrylamide gelatin and sodium alginate. Their addition can further improve the entanglement of the dual network and enhance the mechanical stability of the microspheres.

[0024] N-Acryloylglycine (NAGA) can form hydrogen bonds with methacrylamide gelatin through its amide group, enhancing the toughness of the covalent cross-linked network (i.e., the first network). Simultaneously, due to the presence of carboxylic acid groups in its molecule, it can synergistically bind polyvalent metal ions with sodium alginate, improving the stability of the ionic cross-linked network (i.e., the second network). Acrylate PEG derivatives, acrylamide PEG derivatives, or maleimide PEG derivatives, due to the high hydrophilicity and flexibility of the PEG segments, can enhance network stability through flexible chain entanglement.

[0025] Furthermore, the acrylate PEG derivative includes at least one of polyethylene glycol diacrylate, acrylate polyethylene glycol carboxyl group, acrylate polyethylene glycol amino group, or acrylate polyethylene glycol hydroxy group.

[0026] Furthermore, the acrylamide PEG derivative includes at least one of polyethylene glycol diacrylamide, acrylamide polyethylene glycol amino, or acrylamide polyethylene glycol mercapto.

[0027] Furthermore, the maleimide PEG derivative includes at least one of maleimide polyethylene glycol acrylate, maleimide polyethylene glycol hydroxyl, maleimide polyethylene glycol thiol, or maleimide polyethylene glycol thiol.

[0028] In some embodiments, the hydrophilic monomer accounts for 30% to 60% of the mass percentage of the methacrylamide gelatin. The amount of hydrophilic monomer added is beneficial for its full participation in cross-linking, improving the density of the first network. Furthermore, different amounts of hydrophilic monomer correspond to different mass percentages of methacrylamide gelatin, which can adjust the degree of network cross-linking and thus the degradation characteristics of the network. When a higher amount of hydrophilic monomer is added, i.e., a lower mass percentage of methacrylamide gelatin, the network cross-linking degree is lower, the network porosity is higher, degradation is relatively faster, and the drug release rate is faster. Conversely, when a higher amount of hydrophilic monomer is added, the corresponding mass percentage of methacrylamide gelatin is higher, the network cross-linking degree is higher, the structure is denser, the degradation rate is slower, and the drug release cycle is longer.

[0029] As an example, the mass percentage of hydrophilic monomers in methacrylamide gelatin can be any one of 30%, 40%, 50%, or 60%, or any value between any two of these.

[0030] In some embodiments, sodium alginate accounts for 50% to 80% of the mass percentage of methacrylamide gelatin. Different mass percentages of sodium alginate and methacrylamide gelatin correspond to different proportions of the subsequently formed first and second networks. A suitable proportion of sodium alginate helps control the respective proportions of the first and second networks, thereby regulating the degradation rate of the microspheres, further controlling the gradient and long-lasting sustained release of the drug, and further improving the stability of the interpenetrating dual-network structure, thus enhancing the mechanical stability of the microspheres.

[0031] As an example, the mass percentage of sodium alginate in methacrylamide gelatin can be any one of 50%, 60%, 70%, or 80%, or any value between any two of these.

[0032] In some embodiments, step S1 includes: heating and dissolving methacrylated gelatin at a first temperature T1 to form a gelatin solution, adding a hydrophilic monomer and stirring to dissolve, then cooling to a second temperature T2, and sequentially adding sodium alginate and an initiator to form an aqueous phase. Segmented temperature control combined with stepwise mixing improves the mixing uniformity of the aqueous system and reduces mutual interference between components.

[0033] Furthermore, the degree of amino substitution in the methacrylamide gelatin is 50%–90%. The degree of amino substitution refers to the proportion of amino groups (containing C=C double bonds) that replace amino groups on the gelatin molecular chain, directly determining the number of sites for cross-linking reactions. In the embodiments of this application, controlling the degree of amino substitution in the methacrylamide gelatin to 50%–90% is beneficial for providing a sufficient number of cross-linking sites to control the degree of cross-linking, while retaining good hydrophilicity, biocompatibility, and biodegradability.

[0034] As an example, the degree of amino substitution of methacrylamide gelatin can be any one of 50%, 60%, 70%, 80%, 90%, or a value between any two of these values.

[0035] Furthermore, the first temperature T1 is 37~50 ℃, and the second temperature T2 is 30~35 ℃. Methacrylamide gelatin, as a modified gelatin, retains the collagen triple helix structure of gelatin in its molecular chain. It can dissolve rapidly at 37~50 ℃ to form a homogeneous and transparent solution. When hydrophilic monomers are added at this temperature, they can dissolve fully and mix evenly with the gelatin solution. Adding sodium alginate after cooling to 30~35 ℃ can reduce the damage to its molecular structure caused by high temperatures and reduce premature interactions with the methacrylamide gelatin.

[0036] As an example, the first temperature T1 can be any value among 37 ℃, 40 ℃, 45 ℃, and 50 ℃, or a value between any two values; the second temperature T2 can be any value among 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃, and 35 ℃, or a value between any two values.

[0037] In some embodiments, step S1 further includes adding a hydrophobic monomer having at least one polymerizable double bond.

[0038] By adding hydrophobic monomers, they can be cross-linked with methacrylamide gelatin and hydrophilic monomers through double covalent bonds to form a three-dimensional cross-linked network that combines hydrophilic properties with hydrophobic microdomains. On the one hand, this can improve the network density and shear resistance, and lengthen the drug diffusion pathway (especially for hydrophilic drugs, which need to bypass hydrophobic microdomains to be released), further slowing down the release rate. On the other hand, it can be directly used as a loading site for hydrophobic drugs, reducing the aggregation of hydrophobic drugs in hydrophilic systems, improving loading uniformity, and delaying the drug detachment from the microdomains through hydrophobic interactions, further optimizing the drug release curve and effectively avoiding the problem of sudden drug release.

[0039] Furthermore, the hydrophobic monomer accounts for 10% to 40% of the mass of the methacrylamide gelatin. Adding a suitable amount of hydrophobic monomer helps control the formation of more hydrophobic microdomains, thereby increasing the loading capacity of hydrophobic drugs; it also effectively improves the density and mechanical stability of the cross-linked network.

[0040] As an example, the percentage of hydrophobic monomers in methacrylamide gelatin by mass can be any one of 10%, 20%, 30%, or 40%, or any value between any two of these.

[0041] Furthermore, the hydrophobic monomer includes at least one of methyl methacrylate (MMA) or butyl acrylate (BA). Both MMA and BA contain polymerizable acrylate double bonds (C=C), similar to the methacryloyl double bond structure of the GelMA side chain, and can be stably embedded into the GelMA covalent network through free radical copolymerization (photoinitiated or redox initiated). Moreover, the hydrophobic groups (methyl, butyl) of MMA / BA can form dispersed hydrophobic microdomains in the hydrophilic GelMA network, prolonging the release pathway of the loaded hydrophilic drug and enhancing its sustained-release effect; and efficiently adsorbing hydrophobic drugs such as paclitaxel and doxorubicin through hydrophobic interactions. In addition, the molecular chains of MMA / BA are relatively rigid, and copolymerization can increase the crosslinking density and chain entanglement degree of the GelMA network, further improving the drug sustained-release effect and mechanical stability of the microspheres.

[0042] Furthermore, before adding sodium alginate, the hydrophobic monomer is added to the co-solvent and mixed before being added to the gelatin solution. The hydrophobic monomer is an oil-soluble substance; pre-dispersing it in the co-solvent improves its dispersion uniformity in the aqueous phase and ensures the copolymerization compatibility between the hydrophobic monomer and methacrylamide gelatin. Optionally, the co-solvent refers to a solvent miscible with water, which may include ethanol, propylene glycol, etc.

[0043] S2: Mix the aqueous phase and the oil phase to form a water-in-oil suspension system.

[0044] In some embodiments, the method for preparing the oil phase includes: adding an oil-soluble dispersant to an oil-soluble solvent and stirring to disperse and form an oil phase.

[0045] Furthermore, the oil-soluble dispersant includes at least one of the Span and Tween series, cellulose acetate, octadecyl acrylate, methylcellulose, octadecyl phosphate monoester, hydroxyethyl cellulose and its derivatives, or hexadecyl phosphate monoester.

[0046] Furthermore, the oil-soluble solvent includes at least one of liquid paraffin, petroleum ether, n-hexane, cyclohexane, butyl acetate, polyethylene glycol, n-pentane, n-hexane, gasoline, cyclohexane, toluene, xylene, benzene, light oil, or carbon tetrachloride.

[0047] In some embodiments, step S2 includes: under stirring conditions, maintaining the oil phase temperature at 35~45 °C, slowly adding the aqueous phase dropwise to the oil phase to form a water-in-oil suspension system.

[0048] Optionally, the volume percentage of the aqueous phase in the oil phase is 15% to 40%. As an example, the volume percentage of the aqueous phase in the oil phase can be any value among 15%, 20%, 25%, 30%, 35%, and 40%, or a value between any two of these values.

[0049] S3: Add an aqueous solution of a polyvalent metal ion salt to an oil-in-water suspension system, and obtain embolic microspheres after a cross-linking reaction.

[0050] In some embodiments, the initiator added in step S1 is a redox initiator; step S3 includes: heating the water-in-oil suspension system to 45~50 °C and reacting for 20~40 min, then adding an aqueous solution of a polyvalent metal ion salt, continuing the reaction for 20~40 min, then adding a catalyst, and continuing the reaction for 2~6 h to obtain embolization microspheres. This application employs a redox initiation method. First, at 45-50 °C, the initiator is accelerated to decompose and generate free radicals, initially cross-linking to form a covalent network. Then, an aqueous solution of a polyvalent metal ion salt is added to initiate the reaction. The polyvalent metal ions diffuse within the aqueous droplets and react with sodium alginate to form an ionic cross-linked network. Finally, a catalyst is added to continue the reaction, further increasing the covalent cross-linking density and ensuring thorough entanglement between the covalent and ionic networks, forming a dense, interpenetrating double-network structure. This method results in good cross-linking uniformity and high mechanical stability of the microspheres.

[0051] Furthermore, the polyvalent metal ion salts include at least one of CaCl2, BaCl2, ZnCl2, and FeCl3. These polyvalent metal ion salts can all cross-link with sodium alginate via ionic bonds to form a physical network. In a physiological environment, these polyvalent metal ions are absorbed by the Na+ in body fluids. + K + The competitive binding of cations leads to easy dissociation of ionic bonds, causing the network structure to rapidly disintegrate and degrade quickly. Furthermore, these polyvalent metal ion salts exhibit good biocompatibility and compatibility with the GelMA covalent network. Preferably, the polyvalent metal ion salt includes CaCl2.

[0052] Furthermore, the mass percentage of polyvalent metal ion salts in the aqueous solution of polyvalent metal ion salts is 5% to 10%, which is beneficial to improving the crosslinking density and crosslinking uniformity.

[0053] As an example, the mass percentage of the polyvalent metal ion salt can be any one of 5%, 6%, 7%, 8%, 9%, 10%, or a value between any two of these values.

[0054] Furthermore, the catalyst includes at least one of tetramethylethylenediamine or triethylamine.

[0055] Furthermore, the redox initiator includes at least one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride, or sodium bisulfite.

[0056] In some embodiments, the initiator added in step S1 is a photoinitiator; step S3 includes: adding an aqueous solution of a polyvalent metal ion salt to an oil-in-water suspension system, reacting for 2-40 min, and then performing a crosslinking reaction under light irradiation to obtain embolic microspheres. By first adding an aqueous solution of a polyvalent metal ion salt for ionic crosslinking, and then initiating a photocrosslinking reaction under light irradiation, the orderly formation of the first and second networks can be controlled, the crosslinking uniformity can be improved, and the uniform interpenetration of the first and second networks can be promoted.

[0057] Optionally, the polyvalent metal ion salt includes at least one of CaCl2, BaCl2, ZnCl2, and FeCl3.

[0058] Optionally, the mass percentage of the polyvalent metal ion salt in the aqueous solution of the metal ion salt is 5% to 10%. As an example, the mass percentage of the polyvalent metal ion salt can be any value among 5%, 6%, 7%, 8%, 9%, and 10%, or a value between any two of these values.

[0059] Furthermore, the photoinitiator includes at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropyl phenyl ketone or lithium phenyl (2,4,6-trimethylbenzoyl)phosphate.

[0060] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0061] Example 1 This embodiment provides an embolization microsphere, the preparation method of which includes the following steps: (1) Based on the total mass of the aqueous phase, 8 wt% of methacrylamide gelatin (GelMA, degree of amino substitution of 70%) was dissolved in purified water in a 47 ℃ water bath at a stirring speed of 70 rpm to obtain a gelatin solution; 4 wt% of N-acryloylglycine (NAGA, degree of monomer neutralization of 60%) was added and stirred until completely dissolved; then the temperature was lowered to 30 ℃, and 6 wt% of sodium alginate (SA) and 0.3 wt% of photoinitiator lithium benzoyl phosphate were added in sequence, and the mixture was stirred in the dark for 5 min to form an aqueous phase.

[0062] (2) At 40 ℃ and 400 rpm, 3 g of cellulose acetate (CAB) was dispersed in butyl acetate to obtain an oil phase, ensuring that the water phase accounted for 25% of the volume of the oil phase. The temperature of the oil phase was kept at 35 ℃, and the water phase was slowly added dropwise to the oil phase under stirring to form a stable water-in-oil suspension system.

[0063] (3) Slowly add 8% CaCl2 aqueous solution (preheated to 45℃) dropwise to the above water-in-oil suspension system, stir for 10 min, and then irradiate under 400~450 nm blue light for 20 min to complete the photocrosslinking polymerization. The obtained microspheres are washed three times with methanol, acetone and water in sequence, and then sieved to obtain embolization microspheres of different particle sizes.

[0064] Example 2 This embodiment provides an embolization microsphere, the preparation method of which differs from that of Example 1 in that: Step (1) includes: dissolving 8 wt% methacrylamide gelatin (GelMA, amino substitution degree of 70%) in purified water at a water bath of 47 ℃ and a stirring speed of 70 rpm to obtain a gelatin solution; taking 1 wt% methyl methacrylate (MMA) and adding 0.5 wt% co-solvent ethanol (volume ratio of 1:1 with MMA) and stirring until completely dissolved to obtain an MMA-ethanol solution; adding this solution together with 4 wt% N-acryloylglycine (NAGA, monomer neutralization degree of 60%) to the gelatin solution and stirring until uniformly mixed; then cooling to 30 ℃ and sequentially adding 6 wt% sodium alginate (SA) and 3 wt% ammonium persulfate, stirring and mixing evenly to form an aqueous phase.

[0065] Example 3 This embodiment provides an embolization microsphere, the preparation method of which differs from that of Example 2 in that: In step (1), the mass percentage of MMA is 2 wt%, and the amount of co-solvent ethanol is adjusted to 1.0 wt% (volume ratio of 1:1 with MMA).

[0066] Example 4 This embodiment provides an embolization microsphere, the preparation method of which differs from that of Example 2 in that: In step (1), the mass percentage of MMA is 3 wt%, and the amount of co-solvent ethanol is adjusted to 1.5 wt% (volume ratio of 1:1 with MMA).

[0067] Example 5 This embodiment provides an embolization microsphere, the preparation method of which differs from that of Example 2 in that: In step (1), the mass percentage of methacrylamide gelatin is 10 wt%.

[0068] Comparative Example 1 This comparative example provides an embolization microsphere, the preparation method of which includes the following steps: (1) Based on the total mass of raw materials, 8 wt% of methacrylamide gelatin (GelMA, amino substitution degree of 70%) was dissolved in purified water in a 47 ℃ water bath at a stirring speed of 70 rpm to obtain a gelatin solution; 0.3 wt% of photoinitiator lithium benzoyl phosphate was added and stirred for 5 min in the dark to obtain an aqueous phase.

[0069] (2) At 40 ℃ and 400 rpm, 3 g of cellulose acetate (CAB) was dispersed in butyl acetate to obtain an oil phase, ensuring that the water phase accounted for 25% of the volume of the oil phase. The temperature of the oil phase was kept at 35 ℃, and the water phase was slowly added dropwise to the oil phase under stirring to form a stable water-in-oil suspension system.

[0070] (3) The above-mentioned water-in-oil suspension system was irradiated with 400~450 nm blue light for 20 min to complete the photocrosslinking polymerization. The obtained microspheres were washed three times with methanol, acetone and water in sequence. After sieving, embolization microspheres of different particle sizes were obtained.

[0071] Comparative Example 2 This comparative example provides an embolic microsphere, the preparation method of which differs from that of Example 1 in that: N-Acryloylglycine (NAGA) is not added in step (1).

[0072] Performance testing and results analysis 1. Mechanical properties Blank microspheres with a particle size of 100-300 μm from Examples 1-5 and Comparative Examples 1-2 were taken respectively, spread evenly on a glass slide, placed under the probe of a texture analyzer (TA.XT PlusC), and tested in Hold Compression mode. The test results are shown in Table 2: Table 2. Test results of mechanical properties of embolized microspheres

[0073] As can be seen from Table 2, compared with Comparative Examples 1-2, the embolic microspheres prepared in Examples 1-5 all have better mechanical strength and elasticity, with strength greater than 120 g, rebound force greater than 95 g, and elasticity greater than 65%.

[0074] Comparing Example 1 (strength 125±8 g, resilience 98±5 g) without MMA with Examples 2-4 (strength 160±10 g~210±15 g, resilience 120±6 g~145±8 g) containing MMA, it can be seen that the strength and resilience of the microspheres are significantly improved after the introduction of MMA, and the strength and resilience increase with the increase of MMA ratio.

[0075] Example 5 (10 wt% GelMA, 1 wt% MMA) showed higher strength (183±10 g) and resilience (132±4 g) than Example 2 (8 wt% GelMA, 1 wt% MMA, strength 160±10 g, resilience 120±6 g), and its elasticity (76±3%) was close to that of Examples 1 and 2, indicating that increasing the GelMA content can further enhance mechanical properties. This may be because the hydrophobic monomer MMA enhances network density and crosslink strength through hydrophobic microdomains, which is key to improving mechanical properties; high GelMA content can supplement the enhancement by increasing crosslink density; and the dual-network structure is the basic guarantee of mechanical properties. Combined with hydrophobic monomers or high GelMA content, it is possible to achieve a significant improvement in strength and resilience while maintaining good elasticity.

[0076] 2. Drug release performance Drug-loaded microspheres (100-300 μm in diameter) were placed in a dialysis bag, and 5 mL of PBS (pH=7.4) containing 0.25 mg / mL collagenase was added. The bag was then sealed and immersed in 100 mL of the same concentration of enzyme-PBS. The mixture was incubated at 37 ℃ and 110 rpm on a shaker. 5 mL samples were taken at set intervals, and fresh enzyme-PBS was added as needed. The concentration was calculated by measuring the peak area in the liquid chromatography. The cumulative release rate was calculated using the following formula: ; In the formula, Q represents the cumulative drug release rate (%), and M represents the cumulative drug release rate (%). D Where n is the quantity of drug loaded, and C is the number of times the drug is retrieved. n Let V be the concentration of the sample taken in the nth sampling, V be the total volume of the released liquid, and C be the concentration of the sample taken in the nth sampling. i V represents the sample concentration of the i-th sampling. i Let C0 and V0 be the sample volume of the i-th sampling, where C0 and V0 are both 0.

[0077] The test results are shown in Table 3.

[0078] Table 3. Results of drug release performance tests on drug-loaded embolized microspheres

[0079] As shown in Table 3, Comparative Example 1 uses single GelMA microspheres without cross-linking, resulting in only long-term sustained-release effects but lacking short-term rapid release. Comparative Example 2 has interpenetrating microspheres, but the first network also lacks cross-linking, so the long-term sustained-release effect is also poor. The drug-loaded embolized microspheres in Example 1 exhibit both short-term rapid release and long-term sustained-release effects. The multi-component interpenetrating network microspheres in Examples 1-5 can all achieve low burst release and long-term stable drug release. Examples 2-5, containing MMA, show superior performance (cumulative release rate of 90.78%~95.12% over 168 hours), while the microspheres in Comparative Example 1 (single GelMA) and Comparative Example 2 (interpenetrating network) suffer from severe burst release or release stagnation.

[0080] Therefore, based on the differences in drug release rate, different clinical needs can be specifically matched: for example, the embolization microspheres prepared in Example 2 have a fast drug release rate, balancing low burst release and long-lasting effect, and can be effectively applied to scenarios requiring rapid onset of action and maintenance of a certain efficacy (such as administration to acute inflammatory sites); the embolization microspheres prepared in Example 4 have a slower release rate and the best long-lasting effect, and can be effectively applied to scenarios requiring long-term slow drug release (such as tumor chemotherapy and chronic disease treatment); the embolization microspheres prepared in Example 5 have stable drug release and the strongest network stability, and can be effectively applied to implantable drug delivery requiring strict control of the drug release rate (such as intra-articular and intraperitoneal drug delivery). However, the embolization microspheres prepared in Comparative Examples 1 and 2 both have problems with severe burst release or incomplete release, and are only suitable for short-term rapid drug release scenarios (such as topical application, not suitable for long-term treatment).

[0081] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An embolic microsphere, characterized in that, It includes a dual-network structure formed by interpenetrating a first network and a second network, wherein the first network is formed by covalent cross-linking and the second network is formed by ionic cross-linking; The crosslinking components of the first network include methacrylamide gelatin and a hydrophilic monomer with at least one polymerizable double bond, while the crosslinking components of the second network include sodium alginate and polyvalent metal ion salts.

2. The embolic microspheres according to claim 1, characterized in that, The hydrophilic monomer includes at least one of N-acrylylglycine, acrylate PEG derivative, acrylamide PEG derivative, or maleimide PEG derivative; Optionally, the acrylate PEG derivative includes at least one of polyethylene glycol diacrylate, polyethylene glycol carboxyl acrylate, polyethylene glycol amino acrylate, or polyethylene glycol hydroxy acrylate. Optionally, the acrylamide PEG derivative includes at least one of polyethylene glycol diacrylamide, acrylamide polyethylene glycol amino, or acrylamide polyethylene glycol mercapto. Optionally, the maleimide PEG derivative includes at least one of maleimide polyethylene glycol acrylate, maleimide polyethylene glycol hydroxyl, maleimide polyethylene glycol thiol, or maleimide polyethylene glycol thiol.

3. The embolic microspheres according to claim 1, characterized in that, The hydrophilic monomer constitutes 30% to 60% of the mass percentage of the methacrylamide gelatin; and / or, The sodium alginate accounts for 50% to 80% of the mass percentage of the methacrylamide gelatin.

4. The embolic microspheres according to claim 1, characterized in that, The crosslinking component of the first network also includes a hydrophobic monomer having at least one polymerizable double bond; Optionally, the hydrophobic monomer accounts for 10% to 40% of the mass percentage of the methacrylamide gelatin.

5. The embolic microspheres according to claim 4, characterized in that, The hydrophobic monomer includes at least one of methyl methacrylate or butyl acrylate.

6. A method for preparing embolic microspheres as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Methacrylamide gelatin, a hydrophilic monomer with at least one polymerizable double bond, sodium alginate, and an initiator are dissolved and mixed in water to obtain an aqueous phase; S2: Mix the aqueous phase and the oil phase to form a water-in-oil suspension system; S3: Add an aqueous solution of a polyvalent metal ion salt to the water-in-oil suspension system, and obtain the embolization microspheres after a cross-linking reaction.

7. The preparation method according to claim 6, characterized in that, Step S1 includes: heating and dissolving the methacrylamide gelatin at a first temperature T1 to form a gelatin solution, adding the hydrophilic monomer and stirring to dissolve, then cooling to a second temperature T2, and sequentially adding the sodium alginate and the initiator to form the aqueous phase; Optionally, the degree of amino substitution of the methacrylamide gelatin is 50% to 90%; Optionally, the first temperature T1 is 37~50 ℃, and the second temperature T2 is 30~35 ℃.

8. The preparation method according to claim 7, characterized in that, Step S1 further includes: adding a hydrophobic monomer with at least one polymerizable double bond; Optionally, the hydrophobic monomer accounts for 10% to 40% of the mass percentage of the methacrylamide gelatin; Optionally, the hydrophobic monomer includes at least one of methyl methacrylate or butyl acrylate; Optionally, before adding the sodium alginate, the hydrophobic monomer is added to a co-solvent and mixed before being added to the gelatin solution.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The initiator added in step S1 is a redox initiator; step S3 includes: heating the water-in-oil suspension system to 45~50 ℃ and reacting for 20~40 min, then adding the aqueous solution of the polyvalent metal ion salt, continuing the reaction for 20~40 min, then adding the catalyst, and continuing the reaction for 2~6 h to obtain the embolization microspheres; Optionally, the polyvalent metal ion salt includes at least one of CaCl2, BaCl2, ZnCl2, and FeCl3; Optionally, the multivalent metal ion salt accounts for 5% to 10% of the mass percentage of the multivalent metal ion salt aqueous solution; Optionally, the catalyst comprises at least one of tetramethylethylenediamine or triethylamine. Optionally, the redox initiator includes at least one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride, or sodium bisulfite.

10. The preparation method according to any one of claims 6 to 8, characterized in that, The initiator added in step S1 is a photoinitiator; step S3 includes: adding the aqueous solution of the polyvalent metal ion salt to the water-in-oil suspension system, reacting for 2 to 40 minutes, and then performing a crosslinking reaction under light irradiation to obtain the embolization microspheres; Optionally, the polyvalent metal ion salt includes at least one of CaCl2, BaCl2, ZnCl2, and FeCl3; Optionally, the multivalent metal ion salt accounts for 5% to 10% of the mass percentage of the multivalent metal ion salt aqueous solution; Optionally, the photoinitiator includes at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropyl phenyl ketone or lithium phenyl (2,4,6-trimethylbenzoyl)phosphate.

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