A liver-targeting, long-circulating and acid-responsive nano-drug delivery system loaded with oleuropein, and a preparation method and application thereof

Abstract

The present application relates to the technical field of nanomedicine delivery system, and particularly relates to a liver-targeting, long-circulating and acid-responsive nanomedicine delivery system loaded with oleuropein and a preparation method and application thereof. The nanomedicine delivery system comprises a drug-loaded core and a functional surface modification layer; the drug-loaded core is a zeolitic imidazolate framework loaded with oleuropein; and the functional surface modification layer is a lactobionic acid-polyethylene glycol conjugate. The present application realizes the precise delivery and efficient release of oleuropein at the site of sepsis liver injury by constructing a liver-targeting, long-circulating and acid-responsive three-level modular nanomedicine delivery system. The technical scheme can solve the technical problems of low bioavailability of oleuropein and unsatisfactory targeting delivery efficiency at the site of sepsis liver injury. The technical scheme comprehensively improves the pharmacokinetic characteristics and targeted treatment efficiency of OLE, and provides an efficient and safe nanomedicine delivery system for the precise treatment of sepsis liver injury.

Description

Technical Field

[0001] This invention relates to the field of nanomedicine delivery systems, specifically to a liver-targeting, long-circulating, and acid-responsive nanomedicine delivery system loaded with oleuropein, its preparation method, and its application. Background Technology

[0002] Sepsis, a systemic inflammatory response syndrome triggered by infection, has a complex pathological mechanism involving multiple aspects such as overactivated immune responses, oxidative stress imbalance, and microcirculatory disturbances. The liver, as a vital metabolic and immune organ, is highly susceptible to damage during the progression of sepsis. The incidence of liver injury is high in sepsis patients, and once liver dysfunction develops, the mortality rate rises significantly, far exceeding that of patients with simple sepsis. Currently, treatment for sepsis-related liver injury primarily focuses on anti-infection, organ function support, and symptomatic management, such as using broad-spectrum antibiotics to control the source of infection, clearing inflammatory factors through blood purification, and applying hepatoprotective drugs to improve hepatocyte metabolism. However, these methods are insufficient to halt the pathological progression of liver injury and suffer from significant side effects and limited efficacy. Therefore, there is an urgent need to explore more efficient and precise intervention strategies to reduce the mortality and disability rates of sepsis-related liver injury.

[0003] In this research field, natural products, due to their wide availability, diverse biological activities, and low toxicity, have become important resources for new drug development. Among them, oleuropein (OLE), as the main active ingredient extracted from olive leaves, is considered a potential therapeutic candidate due to its significant anti-inflammatory and antioxidant activities. Studies have shown that oleuropein can inhibit the activation of inflammatory signaling pathways, reduce the release of pro-inflammatory factors, and enhance the activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), thereby reducing oxidative stress damage to hepatocytes. However, the application of oleuropein has significant drawbacks. Its water solubility is extremely poor, making it difficult to fully dissolve in body fluids, resulting in the inability to rapidly form an effective blood concentration after administration; furthermore, its short half-life means it is rapidly metabolized and cleared from the body, significantly shortening the duration of drug action. These pharmacokinetic defects collectively result in extremely low bioavailability of oleuropein after administration to the body. More importantly, it is difficult to achieve effective accumulation in the liver, and the hepatic uptake rate is at a low level, failing to reach the concentration required to exert a therapeutic effect. This severely restricts its therapeutic efficacy and makes it difficult to meet the clinical needs for treating sepsis-related liver injury.

[0004] To improve the delivery of drugs such as oleuropein, existing technologies have explored the use of nanomedicine delivery systems, such as liposomes, polymer nanoparticles, and mesoporous silica nanoparticles. These nanocarriers can, to some extent, improve the water solubility of drugs, delay drug metabolism, and prolong their circulation time in the body. However, these attempts still have many drawbacks: on the one hand, most nanocarriers lack specific targeting ability to hepatocytes, and after administration, they tend to be non-specifically distributed in other tissues and organs throughout the body, which not only reduces the effective concentration of drugs at the site of liver damage but may also cause toxic side effects; on the other hand, some nanocarriers are easily recognized and cleared by the immune system in the body, resulting in an unsatisfactory blood circulation time and failing to fully exert the long-term therapeutic effect of the drugs; in addition, some nanocarriers have poor responsiveness to the microenvironment of the lesion site, making it difficult to achieve precise drug release at the site of liver damage, further affecting the therapeutic effect.

[0005] Regarding the further application of OLE, the following problems still exist in the existing technology: insufficient intrahepatic concentration of free OLE due to pharmacokinetic defects; existing carriers are difficult to achieve precise targeted delivery to the liver; the carrier has a short circulation time in vivo, which cannot fully exert the therapeutic effect of the drug, etc. How to improve the pharmacokinetic characteristics of oleuropein and improve its targeted delivery efficiency at the site of sepsis-induced liver injury has become one of the key issues in current research. Summary of the Invention

[0006] The purpose of this invention is to provide a liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded oleuropein nanomedicine delivery system to address the technical problems of low bioavailability and unsatisfactory targeted delivery efficiency at sites of sepsis-induced liver injury.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A liver-targeting, long-circulating, and acid-responsive nanomedicine delivery system loaded with oleuropein comprises a drug-loaded core and a functionalized surface modification layer; the drug-loaded core is a zeolite imidazole ester backbone loaded with oleuropein; the functionalized surface modification layer is a lactobionic acid-polyethylene glycol conjugate. Further, the oleuropein nanoparticles are prepared by the following method: oleuropein is dispersed in dimethyl sulfoxide, then the resulting mixed solution is added to water, stirred, centrifuged, and the precipitate is collected. The precipitate is then purified to obtain oleuropein nanoparticles.

[0009] Furthermore, the zeolite imidazole ester skeleton is a porous crystal framework formed by the coordination of zinc ions and 2-methylimidazolium; the mass ratio of oleuropein to the zeolite imidazole ester skeleton is 1:3-1:1.

[0010] Furthermore, the molar ratio of zinc ions to 2-methylimidazole is 1:6;

[0011] The zeolite imidazole ester skeleton is obtained by mixing an aqueous solution of zinc ions with a methanol solution of 2-methylimidazole and stirring the mixture at room temperature to obtain a zeolite imidazole ester skeleton with a dodecahedral crystal structure.

[0012] Furthermore, the drug-loaded core releases oleuropein in a weakly acidic environment.

[0013] Furthermore, the lactobionic acid-polyethylene glycol conjugate is formed by coupling lactobionic acid and amino-polyethylene glycol-carboxyl groups via amide bonds; the carboxyl terminus of the amino-polyethylene glycol-carboxyl group is covalently linked to the amino group of the zeolite imidazole ester skeleton.

[0014] Furthermore, the molar ratio of lactobionic acid to amino-polyethylene glycol-carboxyl group is 1.5:1; the mass ratio of amino-polyethylene glycol-carboxyl group to drug-loaded core is 1:3-1:2.

[0015] Furthermore, the molecular weight of the amino-polyethylene glycol-carboxyl group is 2000 Da.

[0016] This technical specification also provides a method for preparing a liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded nanodrug delivery system, comprising the following sequential steps:

[0017] S1: Mix an aqueous solution of zinc ions with a methanol solution of 2-methylimidazole and stir the mixture at room temperature. After the reaction is complete, wash and freeze-dry the mixture to obtain the zeolite imidazole ester skeleton.

[0018] S2: Dissolve oleuropein nanoparticles in methanol, then add zeolite imidazole ester framework dispersion, stir and react at room temperature in the dark, centrifuge to remove free drug and freeze dry to obtain drug-loaded core;

[0019] S3: The carboxyl group of amino-polyethylene glycol-carboxyl group is activated using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide; then, the activated amino-polyethylene glycol-carboxyl group is mixed with the drug-loaded core, and after reaction, a drug-loaded core modified with polyethylene glycol is obtained.

[0020] S4: The carboxyl group of lactobionic acid was activated using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide; then, the activated lactobionic acid was mixed with a drug-loaded core modified with polyethylene glycol, and after reaction, a liver-targeting, long-circulating and acid-responsive nanomedicine-loaded oleuropein nanomedicine delivery system was obtained.

[0021] Furthermore, in steps S2 and S3, the molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 1:1.5; carboxyl activation is carried out at room temperature for 30 minutes.

[0022] This technical solution also provides the application of a liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded oleuropein nanomedicine delivery system in the preparation of drugs for treating sepsis or alleviating liver damage.

[0023] In existing technologies, therapeutic drugs such as free oleuropein (OLE) possess synergistic anti-inflammatory and antioxidant activities, but their poor water solubility (solubility <0.1 mg / mL) and extremely short in vivo half-life (t after intravenous injection) limit their effectiveness. 1 / 2 After oral or intravenous administration, these drugs are rapidly metabolized and eliminated, with a liver tissue uptake rate of less than 5%, making it difficult to maintain an effective therapeutic concentration in the acidic microenvironment of sepsis-induced liver infection and failing to block the cascade damage of "inflammatory cytokine outbreak - oxidative stress exacerbation." Simultaneously, traditional interventional drugs may exacerbate infection spread due to immunosuppressive side effects or, due to their single pathway of action, fail to simultaneously regulate the "inflammation-oxidation" interaction network, thus limiting therapeutic efficacy. While traditional nanodelivery systems can passively accumulate in inflamed tissues through enhanced permeability and retention, they suffer from a lack of synergy, exhibiting poor liver tissue specificity and a short blood circulation half-life: unmodified carriers are easily non-specifically taken up by mononuclear-macrophage systems such as those in the lungs and spleen, resulting in a liver targeting index <1.5, leading to insufficient intrahepatic drug concentration and increased risk of non-target organ toxicity; some targeting carriers are modified with only a single ligand, but due to insufficient surface hydrophilicity and charge exposure, their blood circulation half-life (t) is short. 1 / 2 The <4h> timeframe is insufficient to match the ongoing pathological progression of septic liver injury, making it impossible to maintain effective drug exposure within multiple delivery windows. This demonstrates that current technologies face bottlenecks in the pharmacokinetic properties of the drug itself, its multi-pathway regulatory capabilities, and the synergistic effect of the "long-circulation-targeting" delivery system. Consequently, the treatment of septic liver injury faces a dilemma of "difficulty in maintaining effective drug concentrations, poor liver targeting, and uncontrollable side effects," making it difficult to effectively block the lethal cascade of "inflammatory outbreak-oxidative damage-liver failure."

[0024] This invention achieves precise delivery and efficient release of oleuropein (OLE) at the site of septic liver injury by constructing a three-level modular nanomedicine delivery system (ZIF-8 / LA-PEG@OLE) that integrates liver targeting, long circulation, and acid response. The core technical principle is as follows:

[0025] (1) Acid-responsive drug-loaded core design: Using zeolite imidazole ester framework material (ZIF-8) as a carrier, a porous crystal framework is formed through the coordination self-assembly of zinc ions and 2-methylimidazole. The porous nature of ZIF-8 can efficiently encapsulate hydrophobic OLEs, and its framework dissociates in a weakly acidic environment (such as the inflammatory microenvironment of sepsis-induced liver injury), achieving targeted environmental response release of drugs and solving the problems of poor water solubility and non-specific release of free OLEs.

[0026] (2) Long-circulating intermediate layer modification: Polyethylene glycol (PEG, molecular weight 2000 Da) is coupled to the surface of the ZIF-8 drug-loaded core via amide bonds. The hydrophilicity of PEG molecules can reduce the probability of nanoparticles being recognized and cleared by the reticuloendothelial system (RES), prolonging their blood circulation time in vivo (ZIF-8 / LA-PEG@OLE half-life reaches 6.8h), avoiding the problem of low bioavailability caused by rapid drug metabolism, while improving the targeting performance of the targeting ligand lactobionic acid (LA).

[0027] (3) Active liver-targeting recognition mechanism: LA is covalently coupled to the end of PEG, and the specific binding of LA to the desialyl glycoprotein receptor (ASGPR) highly expressed on the surface of hepatocytes is utilized to achieve active targeting and enrichment of nanoparticles to the liver, thereby improving the accumulation efficiency of drugs at the site of liver injury (liver-targeting efficiency reaches 63.7%) and reducing the distribution of drugs in non-target organs and toxic side effects.

[0028] (4) Cascade Synergistic Effect: The ZIF-8 drug-carrying core, PEG, and LA are connected in an orderly manner through chemical bonds, forming a cascade regulatory mechanism of "active targeted enrichment - long circulation retention - drug release in acidic environment". Among them, the acid responsiveness of ZIF-8 ensures the precise release of drugs at the target site, the long circulation characteristics of PEG prolong the drug action time, and the targeting of LA improves the uptake rate of liver tissue. The three work together to overcome the technical bottlenecks of "mutual exclusion between targeting and circulation time" and "imbalance between drug loading and release efficiency" in traditional carriers.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) Significantly improve liver targeting efficiency: Through the specific binding of LA to hepatocyte ASGPR, the liver targeting efficiency of nanoparticles reaches 63.7%, which is much higher than that of unmodified or non-optimized carriers (such as the targeting efficiency of ZIF-8 directly coupled with LA in Comparative Example 2, which is only 52.1%). This greatly increases the accumulation concentration of OLE at the site of liver injury and solves the problem of insufficient distribution of free drugs in the liver.

[0031] (2) Prolonging the in vivo circulation time: PEG modification prolongs the blood circulation half-life of nanoparticles to 6.8h, avoiding the defects of short drug action time and low bioavailability caused by rapid clearance of traditional carriers, and ensuring the long-term effect of drugs in vivo.

[0032] (3) Achieve precise drug release in response to acid: The ZIF-8 core dissociates efficiently in the weakly acidic microenvironment of the liver injury site in sepsis, with a drug release rate of 98.2% in 24 hours, ensuring that the drug is released in a concentrated manner at the target site, reducing toxic side effects on normal tissues, and solving the problem of non-specific release in the free state of OLE.

[0033] (4) Improve drug loading and stability: By optimizing the crystal form (dodecahedral structure) and preparation process (zinc / imidazolium molar ratio 1:6) of ZIF-8, the drug loading reached 22.3±1.5wt%, and the batch repeatability was excellent (RSD<5%), overcoming the problem of drug loading decrease caused by the target ligand blocking the carrier pores (e.g., the drug loading of Comparative Example 2 was only 4.7±0.3wt%).

[0034] (5) Enhance the efficacy of treatment for sepsis-induced liver injury: Through the synergistic mechanism of “targeted enrichment-long circulation-acid-response drug release”, OLE can exert anti-inflammatory and antioxidant effects at the site of liver injury, significantly improve the treatment effect of sepsis-induced liver injury, and reduce the mortality rate of liver injury in patients with simple sepsis.

[0035] (6) Process feasibility and scalability potential: The stability and uniformity of LA-PEG modification are ensured by process control such as EDC / NHS activation and step-by-step coupling during the preparation process. The final product can be made into sterile lyophilized powder injection, which is convenient for storage and clinical application and has the potential for large-scale production.

[0036] In summary, this invention comprehensively improves the pharmacokinetic characteristics and targeted therapeutic efficacy of OLE through a multi-module synergistic design. The ZIF-8 / LA-PEG@OLE delivery system of this invention significantly enhances targeted delivery efficiency, increasing liver tissue drug concentration by 5.3 times compared to free OLE, while reducing non-target organ distribution by 68%. It also achieves breakthroughs in pathological intervention, reducing serum inflammatory factors by over 65%, restoring liver function indicators by 70%, and increasing mouse survival rate to 70% in a sepsis model. This provides a highly efficient and safe nanomedicine delivery system for the precise treatment of sepsis-related liver injury. This nanomedicine delivery system possesses clinical translational potential, its process controllability supports large-scale production, and its "acid-responsive + liver-targeting" design can be extended to the treatment of various liver diseases. Attached Figure Description

[0037] Figure 1 The image shows the SEM characterization of the dodecahedral ZIF-8 nanoparticles synthesized in Example 1.

[0038] Figure 2 The image shows the SEM characterization of the tetrahedral ZIF-8 nanoparticles synthesized in Comparative Example 1.

[0039] Figure 3 The results of fluorescence distribution and targeting evaluation of different drug delivery systems in mice in Example 4 are shown.

[0040] Figure 4 The statistical results show the effects of different drug delivery systems on mouse survival rate in Example 5.

[0041] Figure 5The effects of different drug delivery systems on mouse liver pathology in Example 6 (H&E images and statistical results).

[0042] Figure 6 The results show the statistical effects of different drug delivery systems on liver function in mice in Example 6.

[0043] Figure 7 The effects of different drug delivery systems on serum inflammatory factors in mice, as described in Example 7. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials and reagents used can all be obtained commercially.

[0045] Example 1: Preparation of Nanoparticles

[0046] (1) Composition of nanoparticles

[0047] The core components of the nanoparticles consist of two parts: a drug-loaded core ZIF-8@OLE and a functionalized surface modification layer LA-PEG.

[0048] Drug-loaded core ZIF-8@OLE: using zinc ions (Zn 2+ The ZIF-8 zeolitic imidazolate framework, formed by the self-assembly of ZIF-8 with the organic ligand 2-methylimidazolium, serves as a carrier. Within its regular pores, the therapeutically active ingredient oleuropein (OLE) is encapsulated through physical adsorption or coordination, forming a drug-loaded core complex. This core endows the nanoparticles with high drug loading capacity, and the targeted release of OLE at the lesion site is achieved through responsive dissociation in the weakly acidic environment of the ZIF-8 framework (pH≈5.0–6.5). ZIF-8 is composed of zinc ions (Zn... 2+ A porous crystal framework formed by coordination of Zn(C4H5N2) with 2-methylimidazole (C4H6N2) is also present, with the chemical formula Zn(C4H5N2)2. Oleuropein (OLE) has the molecular formula C4H6N2. 25 H 32 O 13 The CAS number is 32619-42-4, and the structural formula is shown in formula (1).

[0049]

[0050] Equation (1)

[0051] The functionalized surface modification layer LA-PEG (lactobionic acid-polyethylene glycol conjugate): This LA-PEG complex is formed by covalently coupling the liver-targeting ligand lactobionic acid (LA) to the ends of the polyethylene glycol (PEG) molecular chain, and is chemically fixed to the surface of the ZIF-8 carrier. The PEG segment is linear polyethylene glycol NH2-PEG-COOH with a molecular weight of 2000 Da. LA is C 12 H 22 O 12 (4-O-β-D-galactopyranosyl-D-gluconic acid). The carboxyl group of LA is coupled to the terminal amino group of PEG via an amide bond (-CO-NH-), forming LA-PEG-COOH. The PEG chain acts as a spatial spacer arm, extending the distance between the targeting ligand and the carrier surface, preserving the specific binding ability of LA to the hepatocyte desialyl glycoprotein receptor (ASGPR), while preventing direct LA modification from blocking the ZIF-8 drug-carrying pores. Its molecular layer further provides a stealth effect to prolong blood circulation time and enhances particle colloidal stability.

[0052] Sepsis-induced liver injury is characterized by an acidic microenvironment and ASGPR overexpression in hepatocytes. The pH-responsive dissociation properties of the core ZIF-8 precisely control the release of OLE in the slightly acidic environment of septic liver injury, while the surface LA-PEG layer actively guides the accumulation of nanoparticles in liver lesions through liver targeting, and utilizes the long-cycle properties of PEG to enhance delivery efficiency. Through hierarchical functional integration, both significantly enhance the therapeutic targeting and bioavailability of OLE for liver injury while protecting drug activity.

[0053] (2) Preparation method of nanoparticles

[0054] S1: Synthesis of ZIF-8 support (zeolite imidazolium ester backbone)

[0055] A 0.1-0.5 M aqueous solution of zinc nitrate (preferably 0.2 M) was mixed with a 1.2 M solution of 2-methylimidazolium methanol at a zinc / imidazolium molar ratio of 1:6, and the mixture was stirred at room temperature (preferably 20-35 °C) for 4 hours. After the reaction was completed, the mixture was washed three times by conventional centrifugation (12,000 rpm for 15 minutes each time), and the precipitate was then subjected to conventional freeze-drying to obtain pure-phase ZIF-8 nanoparticles.

[0056] Typical scanning electron microscope (SEM) images of ZIF-8 nanoparticles prepared according to the preferred method described above are shown below. Figure 1 It has a high specific surface area (BET: 1870 m²). 2The synthesized ZIF-8 particles exhibit advantages such as uniform pore distribution (pore size concentrated at 1.1 nm) and enhanced anti-aggregation stability (Zeta potential: +30.5 mV). They also possess a typical dodecahedral crystal structure with clear crystal faces and regular edges, consistent with the characteristic topological configuration of ZIF-8 coordination self-assembly. The particles show good dispersion with no obvious agglomeration or adhesion, providing a uniform reaction interface for subsequent hydrophobic loading of oleuropein (OLE), amide bond modification with polyethylene glycol (PEG), and targeted coupling with lactobionic acid (LA). This ensures the batch-to-batch stability of the nanoparticles' physicochemical properties, supporting large-scale preparation and consistent drug efficacy.

[0057] S2: OLE load

[0058] Oleuropein (OLE) was dissolved in methanol to prepare a solution with an OLE concentration of 2-10 mg / mL (preferably 5 mg / mL). A ZIF-8 dispersion with a concentration of 5-15 mg / mL (preferably 10 mg / mL) prepared from ZIF-8 obtained in step S1 was added, ensuring that the mass ratio of OLE to ZIF-8 was 1:3-1:1 (preferably 1:2). The mixture was stirred under light-protected conditions for 12-24 hours (preferably 16 hours). Afterwards, free drug was removed by routine centrifugation, and the precipitate was freeze-dried to obtain the drug-loaded core ZIF-8@OLE.

[0059] Following the preferred method described above, the drug loading of ZIF-8@OLE can reach 22.3 ± 1.5 wt% (mean ± standard deviation, n=5). The drug loading is calculated as follows: Drug loading (wt%) = (mass of oleuropein (OLE) loaded on the ZIF-8 carrier / total mass of ZIF-8@OLE drug-loaded particles × 100%). The nanoparticles obtained according to this scheme exhibit good batch-to-batch repeatability of drug loading (RSD < 5%, n=5). That is, RSD is the relative standard deviation of drug loading in 5 parallel experiments, also known as the coefficient of variation, which is a statistical measure reflecting the degree of data dispersion. Five parallel experiments were conducted, and the measured values ​​of drug loading were relatively concentrated with a small deviation from the mean, indicating that the preparation process has good stability and repeatability and can obtain relatively consistent product quality across different batches.

[0060] S3: PEG surface modification

[0061] Amino-polyethylene glycol-carboxyl group (NH2-PEG-COOH, molecular weight 2000 Da) was dissolved in PBS buffer at pH 7.4, with a concentration of 5 mg / mL. EDC / NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide molar ratio 1:1.5) was added, and the carboxyl group was activated at room temperature for 30 minutes. The molar ratio of EDC to NH2-PEG-COOH was 10:1. Next, ZIF-8@OLE dispersion, prepared using PBS buffer at pH 7.4 as the solvent, was added, with a concentration of 20 mg / mL. After mixing, the reaction was carried out for 12 hours (PEG to drug-loaded core ZIF-8@OLE mass ratio 1:3-1:2, preferably 1:2.5). After centrifugation and purification, the ZIF-8 / PEG@OLE intermediate (modified with a polyethylene glycol drug-loaded core) was obtained.

[0062] S4: LA-targeted conjugation

[0063] Lactobionic acid (LA) was activated with EDC / NHS. LA was dissolved in ultrapure water to obtain a 5 mg / mL LA solution. Then, EDC and NHS (EDC:NHS molar ratio 1:1.5) were added at a molar ratio of 10:1 to 10:1, and the carboxyl groups were activated at room temperature for 30 minutes. Next, the ZIF-8 / PEG@OLE intermediate from step S3 was added, and the reaction was carried out under nitrogen protection for 24 hours (LA:PEG molar ratio 1.5:1). Unreacted matter was removed by centrifugation to obtain ZIF-8 / LA-PEG@OLE composite particles.

[0064] S5: Formulation

[0065] ZIF-8 / LA-PEG@OLE composite particles were dispersed in a 5% mannitol solution, sterilized by passing through a 0.22 μm filter membrane, and freeze-dried at -50°C for 48 hours to obtain a sterile lyophilized powder for injection. This product can be prepared as a sterile lyophilized powder for injection, and should be reconstituted into a nano-suspension with physiological saline before use.

[0066] The liver-targeting efficiency and drug release rate of the obtained ZIF-8 / LA-PEG@OLE were tested. The liver-targeting efficiency reached 63.7%, and the drug release rate at pH 6.0 (24h) reached 98.2%. The test method for liver-targeting efficiency is detailed in "Liver Targeting Verification" in Example 4 below. Statistical calculations were performed at the peak fluorescence time of liver tissue after nanoparticle injection. The calculation method was: Liver-targeting efficiency (%) = (Liver tissue fluorescence intensity / Total fluorescence intensity of all organs) × 100%. The drug release rate was tested as follows: 1.0 mg of ZIF-8 / LA-PEG@OLE composite particles were dispersed in 10 ml of pH 6.0 acetate-sodium acetate buffer, placed in a dialysis bag, sealed, and then placed in a release medium with the same buffer solution. The release system was placed in a 37°C constant temperature water bath shaker and oscillated at 100 rpm to simulate the physiological temperature and dynamic environment in vivo. After 24 h, the supernatant of the release medium was collected, and an equal volume of fresh buffer was added to maintain a constant volume. The concentration of oleuropein (OLE) in the supernatant was determined by high performance liquid chromatography (HPLC), and the cumulative release was calculated. The drug release rate was calculated as follows: 24-hour drug release rate (%) = (cumulative mass of OLE released in 24 hours / total mass of OLE loaded in the composite particles × 100%). In this study, the 24-hour drug release rate reached 98.2% under pH 6.0 conditions, indicating that the particles can efficiently release the drug in acidic microenvironments (such as sites of sepsis-induced liver injury).

[0067] Comparative Example 1

[0068] This comparative example is basically the same as Example 1, except for step S1, which is as follows:

[0069] A 0.2M aqueous solution of zinc nitrate and a 0.4M methanol solution of 2-methylimidazolium were mixed at a zinc / imidazolium molar ratio of 1:2 and stirred at room temperature for 2 hours to produce ZIF-8 nanoparticles. Except for the above operations, all other procedures were the same as in Example 1.

[0070] Comparison of ZIF-8 nanoparticles

[0071] SEM images of the ZIF-8 nanoparticles obtained in this comparative example can be found here. Figure 2 The obtained ZIF-8 particles exhibit a cubic morphology with a crystal facet exposure ratio >90%. This high proportion of single crystal facet exposure leads to a single pore orientation, and these crystal faces typically have high surface energy, making it easy for particles to aggregate due to enhanced interactions. The ZIF-8 nanoparticles prepared in Example 1 of this scheme are dodecahedral, with more diverse exposed crystal faces and a more uniform pore distribution. This avoids the pore orientation limitation caused by single crystal facet exposure, reduces interparticle interactions caused by crystal facet characteristics, and provides more space for drug loading.

[0072] Through systematic optimization, it was found that controlling the supersaturation concentration of ligands is key to crystal facet regulation. Increasing the 2-methylimidazole concentration from 0.4 M to 1.2 M (zinc / imidazole molar ratio 1:6) and extending the reaction time to 4 h successfully induced a thermodynamically stable rhombic dodecahedral morphology, which has the following advantages: higher specific surface area (BET value increased from 1620 m² in this comparative example). 2 / g increased to 1870 m in Example 1 2 / g), uniform pore distribution (the pore size of the ZIF-8 nanoparticles in Example 1 is concentrated at 1.1 nm) and enhanced anti-aggregation stability (the Zeta potential value increased from +24.3 mV in this comparative example to +30.5 mV in Example 1).

[0073] Comparison of ZIF-8@OLE

[0074] Due to its uniform pore orientation and high surface energy, this morphology leads to significant aggregation after drug loading (polydispersity index PDI > 0.3). Specifically, when the ZIF-8 nanoparticles obtained in this comparative example are loaded with drug using the optimal method in S2 of Example 1, the resulting drug-loaded core ZIF-8@OLE has a PDI > 0.3. In contrast, the drug-loaded core ZIF-8@OLE obtained using the method in Example 1 has a PDI of 0.15 ± 0.03 (n = 5), indicating that the nanoparticles have a uniform particle size distribution and no significant aggregation. This is attributed to its lower surface energy and superior spatial structure due to its dodecahedral morphology, which allows it to maintain good dispersion during drug loading, ensuring uniform drug loading. Furthermore, the ZIF-8@OLE framework prepared according to this comparative example exhibits a collapse rate > 50%.

[0075] After loading the ZIF-8 nanoparticles prepared in this comparative example with drugs, the drug loading was only 18.1 ± 2.1 wt% (calculated for ZIF-8@OLE), while the drug loading of ZIF-8@OLE prepared in Example 1 reached 22.3 ± 1.5 wt% (significant difference in drug loading, p < 0.01, t-test), an increase of 22.3%. Furthermore, batch repeatability was significantly improved (RSD of drug loading in this comparative example was 11.6%, n=5; Example 1: RSD < 5%, n=5), confirming that crystal form optimization significantly improves drug loading stability.

[0076] Comparison of ZIF-8 / LA-PEG@OLE

[0077] The acid-responsive drug release rate of the ZIF-8 / LA-PEG@OLE composite particles obtained according to this comparative method decreased to 45.6% (24h release rate under pH 6.0 conditions), which is significantly lower than the 98.2% in Example 1.

[0078] In addition, the acid-responsive drug release rate of the ZIF-8 / LA-PEG@OLE composite particles obtained according to this comparative method fluctuated greatly (the test method is described in Example 1), with an RSD of 18.7% (n=5) for drug release over 24 hours. In contrast, the RSD of the ZIF-8 / LA-PEG@OLE composite particles obtained according to Example 1 was only 3.2% (n=5).

[0079] Comparative Example 2

[0080] In this comparative example, the drug-loaded core ZIF-8@OLE was synthesized according to the optimal method of steps S1 and S2 of Example 1, and then LA was directly coupled to the surface of the ZIF-8 carrier. More specifically, as follows:

[0081] LA was dissolved in ultrapure water to obtain an LA solution with a concentration of 5 mg / mL. Then, EDC and NHS (molar ratio of EDC to NHS of 1:1.5) were added at a molar ratio of EDC:LA of 10:1, and the carboxyl groups were activated at room temperature for 30 minutes. Next, ZIF-8@OLE was added, and the reaction was carried out under nitrogen protection for 24 hours (LA to ZIF-8@OLE mass ratio of 0.107:1, consistent with the optimal LA to ZIF-8@OLE mass ratio in Example 1). Unreacted matter was removed by centrifugation, and the precipitate was freeze-dried to obtain ZIF-8 / LA@OLE composite particles.

[0082] Testing revealed that this comparative example, which did not contain PEG, exhibited a liver-targeting efficiency of 52.1% for the ZIF-8 / LA@OLE composite particles, lower than the 63.7% efficiency of the ZIF-8 / LA-PEG@OLE composite particles in Example 1. The drug loading of OLE in ZIF-8 / LA@OLE was also measured, showing a significant decrease to 4.7 ± 0.3 wt% (in contrast, the drug loading of LA in unloaded ZIF-8@OLE reached as high as 22.3 ± 1.5 wt%). The inventors believe this may be due to LA molecules blocking the ZIF-8 pores, leading to a reduction in OLE retention within the pores and consequently a sharp drop in drug loading. In this comparative example, ZIF-8 / LA@OLE was the intended final product for treatment. However, due to the decrease in drug loading on OLE caused by LA loading, the therapeutic effect of directly using ZIF-8 / LA@OLE would be significantly reduced. Therefore, a new method for loading LA onto ZIF-8@OLE is needed. The technical solution in Example 1 involves first loading PEG onto ZIF-8@OLE, and then loading LA. In the resulting ZIF-8 / LA-PEG@OLE, LA does not clog the ZIF-8 pores. In the final product ZIF-8 / LA-PEG@OLE prepared in Example 1, the drug loading of OLE was 22.1 ± 1.2 wt% (n=5), which was not significantly different from the drug loading of ZIF-8@OLE before LA modification in Example 1 (22.3 ± 1.5 wt%) (p>0.05), and the drug loading retention rate was as high as 99.1%. In contrast, the drug loading of ZIF-8 / LA@OLE in Comparative Example 2 plummeted to 4.7 ± 0.3 wt%, with a drug loading loss rate of 78.9%. This clearly demonstrates that the PEG spacer arm strategy of Example 1 can effectively avoid the pore blockage problem caused by direct LA modification, ensuring a high drug loading in the final product.

[0083] In addition, the drug release rate of ZIF-8 / LA@OLE in an acidic environment (pH 6.0) was 31.5% (24h), which was significantly lower than the 98.2% in Example 1, and scanning electron microscopy showed that the carrier pore structure completely collapsed.

[0084] Comparative Example 3

[0085] This comparative example is basically the same as Example 1, except that the amino-polyethylene glycol-carboxyl group with a molecular weight of 2000 Da is replaced with an amino-polyethylene glycol-carboxyl group with a molecular weight of 5000 Da in equal molar amounts.

[0086] Following the method of Example 1, the liver-targeting efficiency, drug loading, and acidic drug release rate of the final ZIF-8 / LA-PEG@OLE composite particles obtained in this comparative example were tested. The liver-targeting efficiency decreased to 28.3%, the drug loading decreased to 19.8 ± 1.1 wt%, and the drug release rate decreased to 88.9%. Compared with the final product ZIF-8 / LA-PEG@OLE composite particles of Example 1, which had a liver-targeting efficiency of 63.7%, a drug loading of 22.1 ± 1.2 wt%, and a drug release rate of 98.2%, the performance of the ZIF-8 / LA-PEG@OLE composite particles prepared in this comparative example was significantly reduced. This further illustrates the necessity of PEG modification and the use of appropriate PEG.

[0087] Comparative Example 4

[0088] This comparative example was carried out in the optimal manner of Example 1, except that the EDC / NHS activation step was omitted and PEG was coupled directly first, followed by LA. Due to insufficient activation of the carboxyl group, the LA grafting rate was <20% (HPLC detection showed that the amount of free LA residue was >80%), and the liver targeting efficiency was only 9.7%.

[0089] In summary, this scheme, through strict control of PEG molecular weight (2000 Da), zinc / imidazolium molar ratio (1:6), and EDC / NHS activation, successfully prepared a ZIF-8 / LA-PEG@OLE system that achieved synergistic optimization with a drug loading of 22.1 ± 1.2 wt%, liver targeting efficiency of 63.7%, and drug release rate of 98.2% at pH 6.0. This demonstrates that overcoming the challenge of "target-drug incompatibility" requires the coupling of multiple technical aspects, including spacer arm structure design, carrier crystal form regulation, and directional coupling processes, to achieve efficient liver-targeted delivery.

[0090] Example 2: Cell viability assay

[0091] RAW264.7 macrophages (density 1.2 × 10⁻⁶) were used. 4Cells were seeded in 96-well plates. Different concentrations of ZIF-8 / LA-PEG@OLE (5-40 μg / mL, OLE equivalent gradient: 5, 10, 20, 40 μg / mL) were added to the experimental groups. The negative control group consisted of untreated cells, the blank control group consisted of cell-free culture medium (containing an equal volume of nanoparticle buffer), and the positive control group consisted of acetaminophen (APAP, 20 mM, to induce a liver injury model). 24-48 hours after drug intervention, 10 μL of CCK-8 reagent was added to each well, and the cells were incubated at 37°C and 5% CO2 in the dark for 1-3 hours. The absorbance (OD value) at 450 nm was measured using a microplate reader. Viability was calculated using the formula: Viability (%) = (Experimental group OD - Blank OD) / (Negative control OD - Blank OD) × 100%. Experiments were performed in 3-6 replicates, with edge wells filled with PBS to reduce evaporation error. Data are expressed as mean ± SD. One-way ANOVA was performed, with p < 0.05 considered statistically significant. Cell viability was also measured for L02 cells. Experimental results showed that for RAW264.7 macrophages, even at a high concentration of 40 μg / mL (OLE equivalent), the cell viability remained above 85%, and the half-maximal inhibitory concentration (IC50) was also high. 50 The concentration of the nanoparticles was greater than 200 μg / mL, indicating extremely low toxicity to immune cells. Simultaneously, for normal human hepatocytes (L02), cell viability remained above 90% within the tested concentration range (5-40 μg / mL), with no significant toxicity observed. This verifies the high biocompatibility of the nanoparticles to hepatocytes and immune cells, with a toxicity threshold far exceeding the dosage concentration (10 mg OLE equivalent / kg) set for subsequent in vivo experiments. This provides direct evidence for selecting a safe therapeutic dose, indicating a broad safety window. This embodiment verifies the toxicity threshold of the nanoparticles to hepatocytes and immune cells, supporting in vivo dosage design.

[0092] Example 3: Evaluation of Cellular Anti-inflammatory and Antioxidant Effects

[0093] After establishing an inflammation model by inducing RAW264.7 macrophages with LPS for 24 h, the experimental group was supplemented with ZIF-8 / LA-PEG@OLE, while the control group consisted of free OLE, ZIF-8@OLE, and an equal volume of buffer blank. After 24 h of incubation, the levels of TNF-α and IL-6 in the co-culture supernatant were detected by ELISA. The results showed that the ZIF-8 / LA-PEG@OLE group had a 68%±5.2% reduction in TNF-α (p<0.01) and a 65%±4.5% reduction in IL-6 (p<0.01) compared to the model group, which were significantly better than the free OLE group (42%±3.8% and 39%±3.2%, respectively) and the ZIF-8@OLE group (51%±4.1% and 48%±3.6%, respectively). The anti-inflammatory and antioxidant effects on L02 cells were also evaluated. ROS levels were assessed by detecting fluorescence intensity at 520 nm after L02 cells were incubated with the DCFH-DA probe for 30 min. The ROS fluorescence intensity of the ZIF-8 / LA-PEG@OLE group was 62%±5.8% lower than that of the model group (p<0.01), which was significantly better than that of the free OLE group (38%±4.3%) and the ZIF-8@OLE group (47%±4.9%).

[0094] Example 4: Validation of liver targeting

[0095] Sixteen C57BL / 6 mice were selected and a sepsis-induced liver injury model was established via cecal ligation and perforation (CLP). The mice were randomly divided into four groups: free OLE-Cy5.5 group (free drug, administered via tail vein), ZIF-8@OLE-Cy5.5 group (no PEG / LA modification, drug-loaded ZIF-8), ZIF-8 / PEG@OLE-Cy5.5 group (PEG-modified only, without LA targeting), and ZIF-8 / LA-PEG@OLE-Cy5.5 group (LA and PEG dual modification, prepared using the optimal method in Example 1). Each group received an equal dose of the formulation (OLE equivalent concentration 10 mg / kg, Cy5.5 labeling and tracking) via tail vein injection. Mice were anesthetized at 2 h, 6 h, and 12 h post-administration. Whole-body and liver fluorescence images were acquired using an in vivo imaging system. Radiant efficiency (photon flux, unit: p / s / cm) in the liver was quantitatively analyzed using software. 2 The experiment was conducted in triplicate, and statistical data are expressed as mean ± SD. Experimental results can be found in [reference needed]. Figure 3 .

[0096] At 2 hours: Cy5.5 fluorescence signals were observed in the liver regions of mice in all groups. The liver fluorescence of the ZIF-8 / LA-PEG@OLE group was concentrated and the signal intensity was the highest. The signal of the ZIF-8 / PEG@OLE group was slightly weaker. Due to the non-specific uptake of surface positive charge by monocytes, the fluorescence of the ZIF-8-OLE group diffused to the spleen / lungs, and the liver signal was only 45% of that of the ZIF-8 / LA-PEG@OLE group. The free OLE group had the weakest signal and was distributed throughout the body, with no obvious enrichment characteristics in the liver.

[0097] At 6h: The liver fluorescence in the ZIF-8 / LA-PEG@OLE group was further enhanced, and the fluorescence outline was highly consistent with the anatomical location of the liver, indicating that the targeted enrichment was continuous; the signal in the ZIF-8 / PEG@OLE group was maintained but not enhanced, and the proportion of background fluorescence in the lungs / spleen caused by non-targeted uptake was increased; the signal in the ZIF-8@OLE group and the free OLE group was significantly attenuated, and the distribution throughout the body was more diffuse.

[0098] At 12 hours: the ZIF-8 / LA-PEG@OLE group maintained high-intensity liver fluorescence, indicating a significant targeting retention effect; the signal in the ZIF-8 / PEG@OLE group decreased to 1.1 × 10⁻⁶. 9 p / s / cm 2 / sr, the signal of the non-targeted group (ZIF-8@OLE, free OLE) was close to the background value. Quantitative analysis showed that the liver fluorescence intensity of the ZIF-8 / LA-PEG@OLE group was significantly higher than that of other groups at all time points, confirming that lactobionic acid (LA) specifically recognizes hepatocyte ASGPR, and synergistically with the long-circulating effect of PEG, achieves precise targeted enrichment of sepsis-induced liver injury sites, laying a spatial foundation for efficient drug delivery.

[0099] Example 5: Effect of Nanomedicine Delivery System on Mouse Survival Rate

[0100] A sepsis animal model was established using the conventional cecal ligation and punching (CLP) technique. Eight-week-old Balb / c mice (n=12 per group) were randomly divided into four groups: sham-operated group (NC, laparotomy without ligation and punching), CLP + free OLE group (tail vein injection, OLE 10 mg / kg), CLP + ZIF-8@OLE group (drug-loaded ZIF-8, OLE 10 mg / kg, without PEG / LA modification), and CLP + ZIF-8 / LA-PEG@OLE group (dual-modified nanoparticles, OLE 10 mg / kg). CLP model construction: After anesthesia, the distal 1 / 2 of the cecum was ligated, and sepsis was induced by double-perforation with an 18G needle; 1 hour after the operation, the corresponding preparation was injected via the tail vein (once a day, each dose of OLE equivalent 10mg / kg, for 3 days). The sham-operated group and the control group were injected with the same volume of physiological saline. The mice were observed for 8 consecutive days, and the survival status of the mice was recorded every 12 hours (individuals that died within 24 hours after the operation were excluded to exclude the interference of surgical trauma).

[0101] Survival data were fitted with survival curves ( Figure 4 The data were analyzed using the Log-rank test (*p<0.05, **p<0.01, ***p<0.001): The sham-operated group (NC) had a near 100% survival rate at 8 days, reflecting a normal physiological state; the survival rates of the CLP+free OLE group and the CLP+ZIF-8@OLE group decreased rapidly, with survival rates dropping to 35% and 55% respectively at 4 days post-operation; while the survival period of the CLP+ZIF-8 / LA-PEG@OLE group was significantly prolonged, with a survival rate of 72% at 7 days post-operation, showing a highly significant difference compared to the other CLP-treated groups (p<0.0001). These results confirm that ZIF-8 / LA-PEG@OLE effectively blocks the lethal cascade of sepsis-induced liver injury through a mechanism of "targeted liver enrichment + responsive release + synergistic anti-inflammatory and antioxidant effects," significantly improving the survival probability of mice.

[0102] Example 6: Effects of Nanomedicine Delivery Systems on Liver Injury in Mice

[0103] Mice that underwent different treatments after CLP modeling were selected (groups: NC: CLP + saline (model control); OLE: CLP + free OLE; ZIF-8@OLE: CLP + untargeted drug delivery system; ZIF-8 / LA-PEG@OLE: CLP + dual-modified nano-drug delivery system). Left lobe liver tissue and serum were isolated for analysis. Liver tissue blocks were fixed in 4% neutral formaldehyde, dehydrated with graded ethanol (70%→100%), cleared with xylene, and embedded in paraffin. 4μm thick sections were cut using a microtome and baked at 60℃ for 3 hours to enhance adhesion. After dewaxing with xylene and rehydration with graded ethanol, hematoxylin-eosin (H&E) staining was performed sequentially (hematoxylin staining of nuclei for 8 min, hydrochloric acid ethanol differentiation (microscopic monitoring of nucleus color lightening), ammonia blue reversion for 5 min, and eosin chromatin staining for 3 min). After mounting with neutral resin, the sections were examined under a microscope. Serum was separated by centrifugation at 4℃ and 3000 rpm for 10 min, and the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin (TBIL) were measured. The experiment was performed in 6 biological replicates, and the data were analyzed by one-way ANOVA.

[0104] Visible under a microscope ( Figure 5 In the NC group, the liver lobule structure was severely damaged, with widespread swelling and necrosis of hepatocytes, dense infiltration of neutrophils in the portal area, accompanied by large-scale hemorrhage and vacuolar degeneration; in the OLE group, the range of hepatocyte necrosis was reduced, but focal inflammatory accumulation and sinusoidal congestion still existed; in the ZIF-8@OLE group, the damage was further reduced, but the liver lobule structure was still disordered; in the ZIF-8 / LA-PEG@OLE group, the liver lobule morphology was basically restored to normal, the hepatocyte morphology was close to normal, and only a small number of scattered inflammatory cells were seen.

[0105] Serum biochemical indicators ( Figure 6 In the NC group, AST, ALT, and TBIL reached pathological high values, reflecting severe hepatocellular necrosis and metabolic dysfunction induced by sepsis. Although the indicators in the OLE group decreased compared to the NC group, the repair effect was limited. The ZIF-8@OLE group showed further reductions, demonstrating the delivery advantage of the drug delivery system. The indicators in the ZIF-8 / LA-PEG@OLE group were reduced to the lowest level, showing a highly significant difference from the NC group and being superior to the ZIF-8@OLE group.

[0106] The synergistic effect of pathological morphology and biochemical indicators confirms that ZIF-8 / LA-PEG@OLE, with its LA-targeted liver enrichment, long-circulating PEG, and pH-responsive drug release characteristics, effectively inhibits hepatocyte necrosis, inflammatory infiltration, and abnormal bilirubin metabolism, and significantly blocks the pathological process of sepsis-induced liver injury.

[0107] Example 7: Effects of Nanomedicine Delivery System on the Release of Inflammatory Factors in Mouse Serum

[0108] Mice that underwent different treatments after CLP modeling (groups: NC: CLP + saline, OLE: CLP + free oleuropein, ZIF-8@OLE: CLP + untargeted drug delivery system, ZIF-8 / LA-PEG@OLE: CLP + dual-modified nano-drug delivery system) had blood collected from the inner canthal venous plexus of the eye. Serum was separated by centrifugation at 3000 rpm for 10 min at 4℃. The levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were detected using an ELISA kit. The experiment was performed in 6 biological replicates. Data are expressed as mean ± standard deviation (SD) and analyzed by one-way ANOVA.

[0109] The results show that ( Figure 7 Serum TNF-α (320±25pg / ml) and IL-1β (420±30pg / ml) levels were significantly elevated in the NC group, reflecting the strong inflammatory storm induced by sepsis. Although the OLE group showed a decrease compared to the NC group, the anti-inflammatory effect was limited. The ZIF-8@OLE group showed a further decrease, demonstrating the delivery advantage of the drug delivery system. The ZIF-8 / LA-PEG@OLE group had the lowest level of inflammatory factors, which was significantly different from the NC group and significantly better than the ZIF-8@OLE group.

[0110] The above results indicate that ZIF-8 / LA-PEG@OLE, by leveraging its liver-targeting enrichment and pH-responsive drug release properties, effectively blocks NF-κB pathway activation and significantly inhibits the release of pro-inflammatory factors such as TNF-α and IL-1β in the serum of septic mice, thus creating a low-inflammatory microenvironment for the repair of liver pathological damage.

[0111] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A liver-targeting, long-circulating, and acid-responsive nanomedicine delivery system loaded with oleuropein, characterized in that: It includes a drug-loaded core and a functionalized surface modification layer; the drug-loaded core is a zeolite imidazole ester skeleton loaded with oleuropein; the functionalized surface modification layer is a lactobionic acid-polyethylene glycol conjugate. The zeolite imidazole ester framework is a porous crystal framework formed by the coordination of zinc ions and 2-methylimidazolium; the mass ratio of oleuropein to the zeolite imidazole ester framework is 1:3-1:1; the molar ratio of zinc ions to 2-methylimidazolium is 1:6; the zeolite imidazole ester framework is obtained by mixing an aqueous solution of zinc ions with a methanol solution of 2-methylimidazolium, stirring and reacting at room temperature to obtain a zeolite imidazole ester framework with a dodecahedral crystal structure. The drug-loaded core releases oleuropein in a weakly acidic environment; The lactobionic acid-polyethylene glycol conjugate is formed by coupling lactobionic acid and amino-polyethylene glycol-carboxyl groups via amide bonds; the carboxyl terminus of the amino-polyethylene glycol-carboxyl group is covalently linked to the amino group of the zeolite imidazole ester skeleton; the molar ratio of lactobionic acid to amino-polyethylene glycol-carboxyl group is 1.5:1; the mass ratio of amino-polyethylene glycol-carboxyl group to drug-loaded core is 1:3-1:2; The molecular weight of the amino-polyethylene glycol-carboxyl group is 2000 Da.

2. The method for preparing a liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded oleuropein nanodrug delivery system according to claim 1, characterized in that: The following steps are performed sequentially: S1: Mix an aqueous solution of zinc ions with a methanol solution of 2-methylimidazole and stir the mixture at room temperature. After the reaction is complete, wash and freeze-dry the mixture to obtain the zeolite imidazole ester skeleton. S2: Dissolve oleuropein nanoparticles in methanol, then add zeolite imidazole ester framework dispersion, stir and react at room temperature in the dark, centrifuge to remove free drug and freeze dry to obtain drug-loaded core; S3: The carboxyl group of amino-polyethylene glycol-carboxyl group is activated using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide; then, the activated amino-polyethylene glycol-carboxyl group is mixed with the drug-loaded core, and after reaction, a drug-loaded core modified with polyethylene glycol is obtained. S4: The carboxyl group of lactobionic acid was activated using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide; then, the activated lactobionic acid was mixed with a drug-loaded core modified with polyethylene glycol, and after reaction, a liver-targeting, long-circulating and acid-responsive nanomedicine-loaded oleuropein nanomedicine delivery system was obtained.

3. The method for preparing a liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded oleuropein nanodrug delivery system according to claim 2, characterized in that: In steps S3 and S4, the molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 1:1.5; carboxyl activation is carried out at room temperature for 30 minutes.

4. The application of the liver-targeting, long-circulating, and acid-responsive nanomedicine-loaded oleuropein nanomedicine delivery system according to claim 1 in the preparation of a drug for treating sepsis-induced liver injury.

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