Quercetin@zif-8 core-shell nanoparticles based on polysaccharide modification, preparation method and application thereof

Abstract

The application belongs to the technical field of medicine preparation, and particularly relates to a polysaccharide modified quercetin@ZIF-8 core-shell nanoparticle, a preparation method and application thereof. The polysaccharide modified quercetin@ZIF-8 core-shell nanoparticle comprises the following steps: mixing polysaccharide solution and ZIF-8 suspension loaded with quercetin in equal volume, reacting for 30-120 min, centrifuging, taking the precipitate, and cleaning to obtain the polysaccharide modified quercetin@ZIF-8 core-shell nanoparticle; the pH value of the polysaccharide solution and the ZIF-8 suspension loaded with quercetin is 5-7; the polysaccharide in the polysaccharide solution is any one of fucoidan, tremella polysaccharide and medlar polysaccharide; and the mass ratio of the ZIF-8 loaded with quercetin and the polysaccharide is 1-4:1:4.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical preparation technology, specifically relating to a polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticle, its preparation method, and its application. Background Technology

[0002] Quercetin is a polyphenolic compound widely found in plants such as buckwheat, sea buckthorn, and onions, and is commonly used in functional foods or dietary supplements. Quercetin has long been considered to possess anti-inflammatory and antioxidant properties, and its therapeutic effects have been confirmed in colitis, arthritis, and inflammatory diseases of the lungs. However, its widespread application is limited by its low water solubility, poor chemical stability, and low bioavailability. Quercetin's low solubility in gastric and intestinal juices leads to its rapid metabolism in these fluids, making it difficult to reach effective concentrations in the colon and exert its anti-inflammatory and antioxidant effects. This further limits its application in treating intestinal diseases.

[0003] Among numerous carrier materials, the metal-organic framework ZIF-8 has attracted considerable attention due to its excellent biocompatibility and controllable degradation. Its hydrophobic microporous structure exhibits a strong affinity for quercetin, enabling high drug loading and encapsulation efficiency, which is beneficial for establishing and maintaining effective drug concentrations in the colon. Furthermore, ZIF-8 possesses unique pH-responsive characteristics: it is structurally stable in physiological neutral to weakly alkaline environments, while rapidly degrading in the acidic microenvironment of inflamed sites, thus achieving in-situ targeted drug release. Nevertheless, ZIF-8 still faces challenges in the complex in vivo environment, including insufficient colloidal stability, easy aggregation, and poor drug sustained-release effects. Therefore, functionalization modification is necessary to optimize its delivery performance. Existing technologies utilize polysaccharide encapsulation, which requires modifying ZIF-8 with sulfamic acid before reacting with lentinan to improve stability, prevent aggregation, and enhance drug sustained-release. However, this method involves complex modification steps and can only utilize lentinan after modification, limiting its application to multiple polysaccharides. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles, their preparation method, and applications.

[0005] A method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles includes the following steps: Equal volumes of ZIF-8 suspension loaded with quercetin in polysaccharide solution were mixed and reacted for 30-120 min. After centrifugation, the precipitate was collected, washed, and polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles were obtained. The pH values ​​of the polysaccharide solution and the ZIF-8 suspension loaded with quercetin are both 5 to 7. The polysaccharide in the polysaccharide solution is any one of fucoidan, tremella polysaccharide and wolfberry polysaccharide; The mass ratio of ZIF-8 loaded with quercetin to the polysaccharide is 1~4:1:4.

[0006] This invention achieves the modification of quercetin@ZIF-8 with various natural polysaccharides through precise control of reaction conditions. Furthermore, the entire process requires no modification of ZIF-8, resulting in polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles with high stability and good sustained-release effect of quercetin. The polysaccharides selected in this invention not only exert an adjunctive therapeutic effect through their inherent activity, but their molecular chains can also enhance the mucosal adhesion of the nanoparticles through interactions such as hydrogen bonding and electrostatics, thereby prolonging their residence time at the lesion site.

[0007] In another preferred embodiment, the concentrations of the fucoidan solution and the wolfberry polysaccharide solution are 2 mg / mL to 8 mg / mL; the concentration of the tremella polysaccharide solution is 1 mg / mL to 4 mg / mL. At these concentrations, the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles obtained from these three polysaccharides exhibit the optimal particle size, best dispersibility, and highest absolute Zeta potential.

[0008] In another preferred embodiment, equal-volume mixing of the polysaccharide solution loaded with quercetin and the ZIF-8 suspension refers to adding the polysaccharide solution dropwise into the ZIF-8 suspension loaded with quercetin.

[0009] In another preferred embodiment, the specific process for obtaining the ZIF-8 suspension loaded with quercetin is as follows: Quercetin, organic ligand, zinc salt and stabilizer were stirred and reacted in an alcoholic environment for 15 min to 30 min. The precipitate was collected by centrifugation and dried to obtain ZIF-8 loaded with quercetin. The mass ratio of quercetin, organic ligand, zinc salt and stabilizer was 170~330:75~150:75~150. The quercetin-loaded ZIF-8 was redissolved in water to obtain a quercetin-loaded ZIF-8 suspension.

[0010] In another preferred embodiment, the organic ligand is 2-methylimidazole, the zinc salt is zinc nitrate, and the stabilizer is polyvinylpyrrolidone.

[0011] The second aspect of the present invention provides a method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles.

[0012] A third aspect of this invention provides the application of polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles in the preparation of anti-inflammatory drugs.

[0013] In another preferred embodiment, the release rate of the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles in intestinal fluid is 73.17%~82.08%.

[0014] In another preferred embodiment, the release rate of the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles in gastric juice is 23%~32%.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention, through precise control of multiple parameters including polysaccharide type, reaction system pH, polysaccharide concentration, feed mass ratio, and reaction time, has for the first time achieved the successful one-step construction of quercetin@ZIF-8 core-shell nanoparticles modified with fucoidan, tremella fuciformis polysaccharide, and wolfberry polysaccharide without any chemical modification of ZIF-8. Existing technologies require modification of ZIF-8 with aminosulfonic acid and are only compatible with lentinan, severely limiting their applicability. This invention is the first to discover that, under weakly acidic to neutral conditions with a pH of 5-7, without any modification treatment, various natural polysaccharides with significantly different molecular weights and structures, such as fucoidan, tremella fuciformis polysaccharide, and wolfberry polysaccharide, can spontaneously and uniformly coat the ZIF-8 surface through electrostatic adsorption and hydrogen bonding to form a stable core-shell structure. This not only significantly expands the range of available polysaccharides, but more importantly, the selected polysaccharides themselves possess inherent pharmacological activities such as anti-inflammatory (fucoidan), immunomodulatory (tremella polysaccharide), and antioxidant (lycium barbarum polysaccharide). These activities can synergistically enhance the therapeutic effects of quercetin, endowing nanoparticles with an integrated "drug delivery-targeting-therapeutic" function. The reaction conditions of this invention are mild and precisely controllable, and it eliminates the harsh conditions of strong acids, strong bases, or organic solvents required in existing technologies. The entire process is carried out at room temperature in a near-neutral aqueous phase, fully preserving the bioactivity of the polysaccharides and the integrity of the ZIF-8 crystal structure. Existing technologies require multiple complex steps involving aminosulfonic acid modification, activation, and polysaccharide grafting. This invention simplifies the process to a single step: direct mixing and reaction of the polysaccharide solution and ZIF-8 suspension, significantly reducing production costs and process complexity. Furthermore, the entire process uses water as a solvent, leaving no organic solvent residue, meeting the requirements of green chemistry and pharmaceutical excipient safety, and laying a solid foundation for subsequent oral formulation development.

[0016] This invention successfully solves the core problems of complex modification steps, limited types of polysaccharides, and easy destruction of ZIF-8 structure in the prior art by using the universality of polysaccharide selection, the mildness of reaction conditions, and the precision of process parameters. It provides a simple, efficient, and green new preparation platform for colon-targeted delivery of quercetin. Attached Figure Description

[0017] Figure 1 Figure 1 shows the structural characterization results of the nanoparticles; A is a representative transmission electron microscope (TEM) image (scale bar: 200 nm) of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles; B is a representative scanning electron microscope (SEM) image (scale bar: 500 nm) of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles; C is the hydrodynamic diameter and PDI of quercetin@ZIF-8 and quercetin@ZIF-8 / PS nanoparticles in aqueous solution; D is the zeta potential of quercetin@ZIF-8 and quercetin@ZIF-8 / PS nanoparticles.

[0018] Figure 2 Fourier transform infrared (FT-IR) spectra of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles.

[0019] Figure 3 Figure 1 shows the physicochemical characterization results of the nanoparticles; A is the X-ray diffraction (XRD) pattern of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles; B is the UV-Vis absorption spectrum of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles; C is the effect of quercetin dosage on the EE and LC of quercetin@ZIF-8; D is the in vitro release curve of free quercetin, quercetin@ZIF-8, and quercetin@ZIF-8 / PS nanoparticles in SGF and SIF. Data are expressed as mean ± standard deviation (n=3).

[0020] Figure 4 Figure 1 shows the effect of different preparation conditions on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / Fu NPs. Figure 2 shows the effect of different concentrations (2, 4, 8 mg / mL) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / Fu NPs. Figure 3 shows the effect of different pH values ​​(5, 6, 7) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / Fu NPs. Figure 4 shows the effect of different NP to fucoidan concentration ratios (4:1, 2:1, 1:1, 1:2, 1:4) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / Fu NPs. Figure 5 shows the effect of different preparation times (30, 60, 90, 120 min) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / Fu NPs. The data are average ± SD (n=3).

[0021] Figure 5The effects of different preparation conditions on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / TFP NPs were investigated. (A) Effects of different concentrations (1, 2, 4 mg / mL) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / TFP NPs. (B) Effects of different pH values ​​(5, 6, 7) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / TFP NPs. (C) Effects of different NP-to-Tremella polysaccharide ratios (8:1, 4:1, 2:1, 1:1, 1:2) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / TFP NPs. (D) Effects of different preparation times (30, 60, 90, 120 min) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / TFP NPs. Data are presented as mean ± SD (n=3).

[0022] Figure 6 The following figures illustrate the effects of different preparation conditions on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / LBP NPs: A shows the effect of different concentrations (1, 2, 4 mg / mL) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / LBP NPs; B shows the effect of different pH values ​​(5, 6, 7) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / LBP NPs; C shows the effect of different NP to Lycium barbarum polysaccharide concentration ratios (8:1, 4:1, 2:1, 1:1, 1:2) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / LBP NPs; D shows the effect of different preparation times (30, 60, 90, 120 min) on the particle size, PDI, and Zeta potential of Qu@ZIF-8 / LBP NPs. Data are presented as mean ± SD (n=3).

[0023] Figure 7 Stability results of different NPs under light conditions; A~D: Particle size, PDI and Zeta potential changes of Qu@ZIF-8 (A), Qu@ZIF-8 / Fu (B), Qu@ZIF-8 / TFP (C), and Qu@ZIF-8 / LBP (D) under different light exposure times (0, 30, 60, 90, 120 min); E represents the drug retention rate of free Qu, Qu@ZIF-8 and Qu@ZIF-8 / PS NPs under light conditions over time; Data are mean ± SD (n=3); Statistical analysis was performed using a two-tailed Student's t-test; ***p<0.001.

[0024] Figure 8Stability assessment of different nanoparticles under heating at 80℃. (A~D) Changes in particle size, PDI, and Zeta potential of Qu@ZIF-8 (A), Qu@ZIF-8 / Fu (B), Qu@ZIF-8 / TFP (C), and Qu@ZIF-8 / LBP (D) after heating for different times (0, 30, 60, 90, 120 min); E shows the drug retention rate of Qu, Qu@ZIF-8, and Qu@ZIF-8 / PS under the same heating conditions as a function of time. Data are expressed as mean ± standard deviation (n=3); statistical analysis was performed using a two-tailed Student's t-test, with ***p<0.001.

[0025] Figure 9 Structural diagram showing the effect of storage time on the mean particle size, PDI, and zeta potential of NPs. (AD): Changes in particle size, PDI, and zeta potential of Qu@ZIF-8 (A), Qu@ZIF-8 / Fu (B), Qu@ZIF-8 / TFP (C), and Qu@ZIF-8 / LBP (D) at different storage times (1, 7, and 14 days); (E): Changes in drug retention over time of free Qu, Qu@ZIF-8, and Qu@ZIF-8 / PS NPs under light conditions. Data are presented as mean ± SD (n=3). Statistical analysis was performed using a two-tailed Student's t-test; ***p<0.001. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Fucoidan (Fu), a sulfated polysaccharide derived from brown algae, has a backbone composed of α-(1→3) and α-(1→4) linked fucose residues. It exhibits significant anti-inflammatory and immunomodulatory activities, primarily exerting its effects by downregulating inflammatory mediators. Tremella fuciformis polysaccharide (TFP), a key active ingredient of the edible and medicinal fungus Tremella fuciformis, has a linear (1→3)-α-D-mannose backbone with side chains rich in β-D-xylose and negatively charged β-D-glucuronic acid. This polyelectrolyte property facilitates its assembly with ZIF-8 via electrostatic interactions. TFP also plays a positive role in enhancing immune responses and restoring intestinal barrier function. Lycium barbarum polysaccharide (LBP), an anionic plant polysaccharide derived from Lycium barbarum, has a backbone mainly composed of (1→5)-α-L-arabinose and (1→4)-α-D-galacturonic acid residues. It possesses various biological activities, including antioxidant and immunomodulatory effects, and can bind to ZIF-8 via electrostatic and hydrogen bonding interactions. These polysaccharides not only exert adjuvant therapeutic effects due to their inherent activity, but their molecular chains can also enhance the mucosal adhesion of nanoparticles through interactions such as hydrogen bonding and electrostatics, thereby prolonging their retention time at the lesion site. This invention constructed core-shell nanoparticles (Qu@ZIF-8 / PS) with ZIF-8 encapsulated quercetin as the core and three different molecular weight polysaccharides (LBP, ~5.2 kDa; Fu, ~63 kDa; TFP, ~380 kDa) modified on the surface. The morphology, size, surface potential, drug loading capacity, and core-shell structure of the nanoparticles were systematically confirmed using various characterization methods.

[0029] Fucoidan, Tremella fuciformis polysaccharide, and Lycium barbarum polysaccharide were purchased from Shanghai Maclean Biochemical Co., Ltd. Quercetin (Qu) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0030] 1. Experimental Methods 1.1 Synthesis of ZIF-8 and Qu@ZIF-8 First, 150 mg of zinc nitrate and 150 mg of polyvinylpyrrolidone were dissolved in 10.5 mL of deionized water; simultaneously, 330 mg of 2-methylimidazole and 5 mg of quercetin were dissolved in 5.5 mL of methanol. The two solutions were mixed and reacted with magnetic stirring at room temperature for 15 min. After the reaction, the resulting yellow product was centrifuged at 12000 rpm for 10 min, washed with ethanol, and dried overnight under vacuum to obtain quercetin-loaded ZIF-8 nanoparticles, denoted as Qu@ZIF-8 nanoparticles. As a control, unloaded ZIF-8 nanoparticles were synthesized using the same procedure, but without the addition of quercetin.

[0031] 1.2 Preparation of Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP and Qu@ZIF-8 / LBP Qu@ZIF-8 nanoparticles were coated with fucoidan (Fu), tremella fuciformis polysaccharide (TFP), and wolfberry polysaccharide (LBP) respectively to prepare corresponding polysaccharide-modified nanoparticles Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP, and Qu@ZIF-8 / LBP. The basic coating steps are as follows:

[0032] After ultrasonic dispersion of the Qu@ZIF-8 aqueous suspension, it was transferred to a brown glass bottle and stirred at 30℃ and 500-1000 rpm. The pre-prepared polysaccharide solution was added dropwise at a rate of approximately 2 drops / second, and stirring was continued for 30 minutes. After the reaction was completed, the mixture was centrifuged at 10000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was washed twice with 25 mL of distilled water to remove unadsorbed polysaccharides. Finally, it was resuspended in 5 mL of distilled water for later use.

[0033] To further investigate the effects of polysaccharide coating process, the effects of polysaccharide type, polysaccharide concentration, solution pH, stirring time, and the mass ratio of Qu@ZIF-8 to polysaccharide were investigated. The specific experimental design is as follows: 1) Optimization of polysaccharide type and concentration For Fu and LBP, three concentrations of 2 mg / mL, 4 mg / mL, and 8 mg / mL were tested respectively. 5 mL of each of these three polysaccharide solutions was then mixed with 5 mL of Qu@ZIF-8 suspension at the same concentration and volume. This means the concentrations of the Qu@ZIF-8 suspension were 2 mg / mL, 4 mg / mL, and 8 mg / mL, the same as the polysaccharide concentration. For high molecular weight TFP, considering its solution characteristics, the concentrations were set to 1 mg / mL, 2 mg / mL, and 4 mg / mL, and it was similarly mixed with an equal volume of Qu@ZIF-8 suspension at the same concentration.

[0034] 2) Solution pH Adjust the pH of the polysaccharide solution and the Qu@ZIF-8 suspension to 5, 6 and 7 respectively using 0.1 mol / L HCl or NaOH solution. Prepare 2 mg / mL of the above three polysaccharide solutions and 5 mL of Qu@ZIF-8 suspension, and perform coating according to the basic steps described above.

[0035] 3) Stirring time Three polysaccharide solutions were added dropwise to Qu@ZIF-8 suspension at a fixed concentration of 2 mg / mL and 5 mL of each solution. Samples were taken at 30 min, 60 min, 90 min and 120 min of stirring, and the subsequent treatment was the same as before.

[0036] 4) Feed mass ratio Fu system, LBP system and TFP system: set the mass ratio of Qu@ZIF-8 to polysaccharide to be 1:4, 1:2, 1:1, 2:1 and 4:1 respectively, and achieve the corresponding ratio by adjusting the concentration of the two solutions (for example, 1:4 corresponds to 2 mg / mL Qu@ZIF-8 and 8 mg / mL polysaccharide, 5 mL each).

[0037] In all the above experiments, except for specific variables, the operating conditions were consistent with the basic coating steps.

[0038] 1.3 Structural Characterization The morphology and size of the samples were characterized using transmission electron microscopy (TECNAI G2, FEI) at an accelerating voltage of 80 kV. The surface microstructure of the freeze-dried samples was observed using scanning electron microscopy (SU8010, Hitachi, Japan) at 10 kV. The crystal structure of the materials was analyzed using X-ray diffraction (XRD-7000S, Shimadzu, Japan), and the functional groups and chemical structure were detected using Fourier transform infrared spectroscopy (Vetex70, Bruker, Germany). The absorption spectra of the samples in the ultraviolet-visible region were recorded using a UV-Vis spectrophotometer (UV-2600, Shimadzu, Japan). The average particle size, polydispersity index (PDI), and zeta potential of the nanoparticles were determined using a Malvern laser particle size analyzer (ZEN3600, Malvern Instruments Ltd., UK). All measurements were repeated three times, and the results are expressed as mean ± standard deviation.

[0039] 1.4 Encapsulation efficiency (EE) and loading capacity (LC) First, the freshly prepared nanoparticle suspension was centrifuged at 10,000 rpm for 10 minutes to remove unencapsulated free quercetin (Qu). The supernatant was collected to determine the concentration of free Qu. To determine the drug loading, the dried nanoparticles were placed in a centrifuge tube containing 10 mL of 3% formic acid methanol solution and sonicated for 30 minutes to fully extract Qu. The absorbance of the supernatant was measured at the maximum absorption wavelength of Qu (372 nm) using a UV-Vis spectrophotometer (UV-2600, Shimadzu, Japan), and its concentration was calculated according to the standard curve of Qu. The encapsulation efficiency (EE) and drug loading (LC) were calculated according to formulas (1), (2), and (3), respectively:

[0040] (1); (2); (3).

[0041] Where A1 is the amount of Qu encapsulated, A2 is the total amount of Qu, A3 is the amount of MOF recycled, and A4 is the total amount of Qu-MOF.

[0042] Stability of 1.5 nanoparticles To evaluate the stability of the nanoparticles, thermal stability, photostability, and storage stability tests were conducted. Freshly prepared Qu, Qu@ZIF-8, and Qu@ZIF-8 / polysaccharide nanoparticles were heated in an 85°C water bath for 2 hours, then cooled to room temperature and characterized. The changes in particle size and zeta potential after 2 hours of UV irradiation were also investigated. Furthermore, fresh samples were stored at room temperature for 14 days, and their particle size distribution and zeta potential were measured on days 1, 7, and 14. Under these conditions, the retention rate of Qu was calculated using the following formula (4) to assess its physical stability.

[0043] (4).

[0044] 1.6 In vitro drug release study To simulate the gastrointestinal digestion process and evaluate the release behavior of quercetin, 1 mL of solutions containing 1 mg / mL of Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP, and Qu@ZIF-8 / LBP were placed in a dialysis bag with a molecular weight cutoff of 3.5 kDa. The bag was then immersed in 15 mL of simulated gastric fluid and dialyzed at 37°C and 115 rpm for 2 h to simulate gastric digestion. During this period, 1 mL of the released fluid was collected every 30 min to determine the quercetin content, and 1 mL of fresh medium was added simultaneously. After the gastric stage, the dialysis device was transferred to 15 mL of simulated intestinal fluid, and dialysis was continued under the same conditions for 4 h to evaluate intestinal release. After release, 1 mL of the in vitro digestion fluid was extracted with 1 mL of ethyl acetate containing 1.5% formic acid. The extracted sample was dried under nitrogen and then reconstituted with 1.5 mL of methanol. Finally, the concentration of quercetin was determined using a UV-Vis spectrophotometer. All experiments were independently repeated three times.

[0045] 2. Results 2.1 Analysis and characterization of different polysaccharide shell NPs Qu-loaded ZIF-8 nanoparticles (Qu@ZIF-8NPs) were synthesized in a one-pot method at room temperature. Further surface modification was used to prepare three derivatives: Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP, and Qu@ZIF-8 / LBP, coated with fucoidan (Fu), tremella fuciformis polysaccharide (TFP), and wolfberry polysaccharide (LBP), respectively, to systematically compare the effects of different polysaccharide modifications on their properties. The morphology of the materials was observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Figure 1 (A and B), the results show that the nanoparticles have a uniform three-dimensional polyhedral structure.

[0046] Malvern laser particle size analyzer analysis showed that the average particle size of Qu@ZIF-8 NPs was 342.2 nm, and the PDI was 0.23. Figure 1 C), the Zeta potential is +20.4mV ( Figure 1 D). After coating with polysaccharides, the particle sizes of the three NPs increased to 424.1 nm, 413.1 nm, and 409.4 nm, respectively. Figure 1 The PDI values ​​were 0.25, 0.21, and 0.24, respectively, and the surface Zeta potential all changed to approximately -18.5 mV. Figure 1 D). The increased particle size and the shift from positive to negative potential align with the coating design expectations, and the higher surface negative potential is beneficial for the retention and accumulation of nanoparticles in the colon region. Furthermore, as... Figure 3 As shown in C, when the Qu addition amount was 7 mg, the encapsulation efficiency (EE%) and drug loading rate (LC%) of Qu@ZIF-8 NPs for quercetin reached the maximum equilibrium, which were 36.32%±0.41% and 5.19%±0.04%, respectively.

[0047] Infrared spectroscopy analysis shows that, Figure 2 As shown, pure quercetin at 3402 cm⁻¹ -1 (Phenolic hydroxyl group), 1655cm -1 and 1606cm -1 Characteristic peaks were observed in the C=O vibration and the fingerprint region. After the formation of Qu@ZIF-8, the hydroxyl peak shifted to 3417 cm⁻¹. -1 Furthermore, the intensity decreased, and the carbonyl peak shifted to 1665 cm⁻¹. -1 And it decreased, while the quercetin fingerprint peak was replaced by the ZIF-8 characteristic peak (1417 cm⁻¹). -1 1140cm -1 990cm -1 The masking effect demonstrates that quercetin was successfully encapsulated within the ZIF-8 channels, with hydrogen bonds or π-π interactions between them, and the ZIF-8 skeleton remained stable. After polysaccharide functionalization, the hydroxyl peak further shifted to 3445–3458 cm⁻¹. -1 The carbonyl region peak is located at 1651~1662 cm⁻¹. -1 Fluctuations and the appearance of polysaccharide characteristic peaks in the fingerprint region confirm that the functional ligand has been successfully modified onto the material surface. X-ray diffraction (XRD) patterns show... Figure 3 A) The characteristic peaks of crystalline quercetin completely disappeared in Qu@ZIF-8 and its polysaccharide coating system, indicating that the drug was encapsulated in an amorphous form. Qu@ZIF-8 exhibited sharp diffraction peaks completely consistent with standard ZIF-8, proving its good crystallization. After surface modification with polysaccharides (Fu, TFP, or LBP), the diffraction peak positions remained unchanged, with only a slight decrease in intensity, indicating that the crystal structure of ZIF-8 was not destroyed, and a stable core-shell coating structure was successfully constructed. Figure 3As shown in Figure B, Qu exhibits strong absorption in the 300–400 nm ultraviolet region, but weak absorption in the 400–500 nm visible light region. After sequential coating with ZIF-8 and polysaccharides, the absorption of the resulting nanoparticles in the visible light region is significantly enhanced, with a marked red shift in the absorption edge, indicating that Qu was successfully loaded into ZIF-8 and that the polysaccharides were further modified on its surface.

[0048] In vitro simulated gastrointestinal release experiments showed that ( Figure 3 D) Free quercetin (Qu) has poor water solubility and slow release, with a cumulative release rate of only about 35% over 360 minutes, indicating limited oral bioavailability. Qu@ZIF8 exhibits pH-responsive release behavior: In simulated gastric juice (SGF), the ZIF8 structure gradually degrades under acidic conditions, but drug release is relatively slow due to the limited volume of the release medium (leakage conditions); upon entering simulated intestinal juice (SIF), ZIF8 degradation accelerates with increasing pH, and drug release significantly increases, reaching a release rate of approximately 63% over 360 minutes. The polysaccharide-encapsulated systems Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP, and Qu@ZIF-8 / LBP all exhibited a "slow-release in the stomach, fast-release in the intestine" delivery pattern: In the gastric juice stage, the polysaccharide layer acted as a physical barrier, delaying the acid hydrolysis of ZIF-8 and drug release, with a release rate of 23%–32%, significantly lower than that of Qu@ZIF-8; after entering the intestinal juice, the polysaccharide barrier gradually dissolved under the action of various enzymes, ZIF-8 was further degraded, and drug release was significantly enhanced. Among them, Qu@ZIF-8 / TFP had the highest final cumulative release rate of 82.08%, while Qu@ZIF-8 / Fu and Qu@ZIF-8 / LBP were 76.56% and 73.17%, respectively. This difference may be related to the molecular weight, spatial structure, and enzymatic hydrolysis behavior of different polysaccharides in simulated intestinal juice, providing important in vitro physicochemical property evidence for subsequent evaluation of their biological functions.

[0049] 2.2 Effects of different factors on Qu@ZIF-8 / Fu NPs The effect of different polysaccharide concentrations on Qu@ZIF-8 / Fu NPs is as follows: Figure 4 As shown in Figure A, the hydrodynamic particle size of the nanoparticles exhibits a non-monotonic variation at polysaccharide concentrations of 2 mg / ml, 4 mg / ml, and 8 mg / ml. The optimal particle size (418.3 nm) is observed at a polysaccharide concentration of 8 mg / ml. At this concentration, the PDI is 0.253, and the Zeta potential is -27.5 mV, demonstrating the best dispersibility and the highest absolute Zeta potential. When the solution pH is 6, the nanoparticles exhibit a smaller particle size (445.2 nm) and better dispersibility (PDI = 0.308), with a Zeta potential of -23.6 mV. Figure 4B); Different NP to fucoidan concentration ratios showed that a 1:1 ratio achieved a good balance between particle size, dispersibility, and surface potential (426.7 nm, PDI = 0.328, Zate = -25.5 mV). Figure 4 C) indicates that at this ratio, the coating of fucoidan may be close to saturation, which fully utilizes its steric stabilizing effect and avoids the increase in medium viscosity or particle size expansion caused by secondary adsorption due to excessive polysaccharide.

[0050] Furthermore, it was found that the nanoparticles had the smallest particle size (394.9 nm) when the stirring time was 120 min. Figure 4 (D) However, under these conditions, the colloidal solution exhibits poor dispersibility (PDI = 0.582) and the lowest absolute value of the Zeta potential (Zeta = -16.6). When the stirring time is 60 min, the Zeta potential of the solution system reaches its maximum value (-32.2 mV), and the PDI is at its lowest (PDI = 0.319). At this point, the particle size of the nanoparticles is 435.5 nm, indicating that the system exhibits higher dispersibility and stability under the stirring time of 60 min. In summary, by controlling the Fu polysaccharide concentration at 8 mg / mL, adjusting the pH of the reaction system to 6, using a 1:1 NPs / fucose mass ratio, and maintaining a stirring time of 60 min, Qu@ZIF-8 / Fu nanoparticles with moderate particle size, uniform dispersion, and high surface charge can be obtained.

[0051] 2.3 Effects of different factors on Qu@ZIF-8 / TFP NPs The effect of different TFP concentrations on the system is as follows: Figure 5 As shown in Figure A, with the increase of TFP polysaccharide concentration, the particle size of the nanoparticles increased from 521.8 nm to 717 nm, and the dispersibility index (PDI) of the colloidal solution increased from 0.439 to 0.623. However, the change in the solution Zeta potential was small (26.7 mV ~ 24.4 mV), indicating that high-concentration polysaccharide solutions may promote particle aggregation, leading to a decrease in the system's dispersibility, but the surface charge remains stable. Observations at different solution pH levels revealed that when the solution pH was 6, the nanoparticles had the smallest particle size (507.4 nm) and the lowest PDI (0.405), while also exhibiting a relatively high Zeta potential (Zeta = -25.2 mV). Figure 5 B) indicates that a near-neutral environment is conducive to maintaining moderate extension and charge distribution of polysaccharide chains, promoting uniform coating and stable dispersion; the results of different NPs to Tremella polysaccharide concentration ratios show that when the ratio is 2:1, the colloidal solution exhibits the best overall properties. Figure 5At point C, the nanoparticles exhibit a small particle size (436.8 nm), the lowest PDI index (PDI = 0.339), and the highest absolute Zeta potential (Zeta = -25.4 mV). Results from different stirring times show that at a stirring time of 30 min, the nanoparticle size is the smallest (370.1 nm), but the dispersibility of the solution is poor (PDI = 0.452). At a stirring time of 90 min, the nanoparticles have a moderate particle size (413.1 nm) and exhibit the best dispersibility (PDI = 0.344) and stability (Zeta = -24.4 mV). Figure 5 D). In summary, by controlling the polysaccharide concentration to 1 mg / ml, adjusting the solution pH to 6, using an NPs / TFP mass ratio of 2:1, and a reaction time of 90 min during the nanoparticle synthesis process, a Qu@ZIF-8 / TFP nanoparticle system with small particle size, uniform distribution, and good colloidal stability can be obtained.

[0052] 2.4 Effects of different factors on Qu@ZIF-8 / LBP NPs The effect of different LBP polysaccharide concentrations on the system showed that with increasing LBP polysaccharide concentration, the nanoparticle size first increased and then decreased. When the LBP concentration was 2 mg / ml, the smallest nanoparticle size was 388.2 nm; however, the dispersibility of the colloidal solution was relatively poor at this point, with a PDI of 0.298. When the LBP concentration increased to 8 mg / ml, the particle size increased to 406.7 nm, but the colloidal solution exhibited excellent dispersibility, with a PDI of 0.166, and good solution stability, with a Zeta of -22.7 mV. Figure 6 A) indicates that higher concentrations of LBP may promote a more uniform and rapid nucleation process, and enhance the effective adsorption and dense coating of LBP on the particle surface, thereby improving the monodispersity and stability of the system through the synergistic effect of steric hindrance and electrostatic repulsion. Under different solution pH conditions, it was found that the optimal nanoparticle size (425.9 nm) was achieved at pH 6, at which point the solution exhibited good dispersibility (PDI = 0.311) and the best stability (Zeta = -22.7 mV). Figure 6 B); The results of different NPs to Lycium barbarum polysaccharide concentration ratios showed that when the ratio was 1:1, the solution system exhibited superior overall performance. At this ratio, the nanoparticle size was moderate (429.0 nm), the PDI was lowest (0.257), and the Zeta potential was -19.7 mV. Figure 6 C); Among different preparation times, the nanoparticles prepared under the 90-min condition had the smallest particle size (404.5 nm), the best dispersibility (PDI = 0.314), and maintained a Zeta potential of -19.1 mV. Figure 6(D) This reaction time likely corresponds to the equilibrium stage of nanoparticle coordination assembly, resulting in structurally stable nanoparticles with uniform interfacial charge distribution. Shorter reaction times may lead to insufficient reaction, while longer reaction times may induce particle aggregation, resulting in an increase in PDI and a decrease in the absolute value of the potential. In summary, by controlling the polysaccharide concentration to 8 mg / ml, adjusting the solution pH to 6, using an NPs / TFP mass ratio of 1:1, and a reaction time of 90 min during nanoparticle synthesis, a Qu@ZIF-8 / LBP nanoparticle system with small particle size, uniform distribution, and good colloidal stability can be obtained.

[0053] Photostability of 2.5 nanoparticles The stability results of different NPs under illumination are shown in the figure. During the 120-minute illumination process, the hydrodynamic particle size of all nanoparticles gradually increased with time, while the solution dispersibility gradually decreased with the extension of illumination time. Among them, the particle size of the unmodified polysaccharide Qu@ZIF-8 increased from 322.2 nm to 448.2 nm, and the PDI increased from 0.230 to 0.392. Figure 7 A), while the particle size of polysaccharide-modified systems such as Qu@ZIF-8 / Fu increased from 404.0 nm to 464.0 nm, and the PDI increased from 0.229 to 0.307. Figure 7 B), the particle size of Qu@ZIF-8 / TFP increased from 394.5 nm to 468.7 nm, and the PDI increased from 0.254 to 0.355. Figure 7 C), the particle size of Qu@ZIF-8 / LBP increased from 409.4 nm to 453.2 nm, and the PDI increased from 0.237 to 0.313. Figure 7 (D) Overall, the PDI of the polysaccharide-modified system was consistently lower than that of the unmodified system, especially at the end of illumination, where the PDI of Qu@ZIF-8 reached 0.392, while the PDIs of Qu@ZIF-8 / Fu, Qu@ZIF-8 / TFP, and Qu@ZIF-8 / LBP were 0.307, 0.355, and 0.313, respectively. This indicates that the polysaccharide shell effectively suppressed heterogeneous aggregation of particles and maintained the homogeneity of the system. Regarding the zeta potential, all systems remained relatively stable. The zeta potential of the unmodified Qu@ZIF-8 fluctuated around 20 mV, while the polysaccharide-modified systems all carried a high negative charge (approximately -25 to -29 mV) and fluctuated less during illumination, indicating that the surface polysaccharides maintained the stability of the colloid by enhancing electrostatic repulsion.

[0054] In addition, drug retention experiments showed ( Figure 7After 120 minutes of illumination, the retention rate of Qu (E) significantly decreased to 73.89%, while that of Qu@ZIF-8 increased to 82.27%. The polysaccharide-modified systems exhibited superior photoprotective performance, with Qu@ZIF-8 / LBP showing the highest retention rate (92.44%), followed by Qu@ZIF-8 / TFP and Qu@ZIF-8 / Fu at 92.57% and 91.64%, respectively. These results collectively demonstrate that polysaccharide modification not only maintains the physical integrity of nanoparticles through steric hindrance and electrostatic stabilization mechanisms, but its dense hydrophilic interface also effectively shields the core drug from direct degradation by photoradiation, thus significantly improving the stability of photosensitizing drugs. In summary, this confirms that polysaccharide surface functionalization is an effective strategy for optimizing the photostability of ZIF-8-based nanocarriers.

[0055] Thermal stability of 2.6 nanoparticles The stability of different NPs under heating at 80℃ is shown in the figure. During the heat treatment process of up to 120 minutes, the unmodified Qu@ZIF-8 showed a significant tendency for thermal aggregation. The hydrodynamic particle size of the nanoparticles increased significantly from 303.4 nm to 454.6 nm, the PDI increased from 0.254 to 0.382, and the Zeta potential decreased from 17.4 mV to 14.1 mV, indicating that both particle uniformity and surface charge stability decreased with increasing heating time. Figure 8 A). In contrast, the polysaccharide-modified nanoparticle system exhibited significantly enhanced colloidal stability: among them, the fucoidan-modified Qu@ZIF-8 / Fu system was the most stable, with the particle size increasing only from 434.0 nm to 446.3 nm, the PDI remaining in a low range of 0.209–0.291, and the Zeta potential remaining high and negative (-26.8 ~ -29.7 mV), indicating that its surface polysaccharide layer can effectively inhibit thermally induced aggregation and maintain an electrostatic repulsion barrier. Figure 8 B), the particle size of the Tremella fuciformis polysaccharide modified system (Qu@ZIF-8 / TFP) increased from 408.6 nm to 490.8 nm, the PDI increased from 0.251 to 0.320, and the Zeta potential remained at a high value (-27.4 mV-29.5 mV). Figure 8 C), the particle size of the Lycium barbarum polysaccharide modified system (Qu@ZIF-8 / LBP) increased from 426.1 nm to 550.3 nm, the PDI increased from 0.292 to 0.461, and the Zeta potential remained at a high value (-21.5 mV to 23.4 mV). Figure 8 (D) The systems modified with Tremella fuciformis polysaccharide and Lycium barbarum polysaccharide showed relatively significant changes in particle size growth. However, the increase in PDI and the decrease in Zeta potential in the two polysaccharide-modified systems were still milder than in the unmodified system, indicating that polysaccharide coating buffered the damage to particle structure caused by thermal disturbance to a certain extent.

[0056] Drug retention rate experiments showed that polysaccharide modification significantly improved the thermal stability of quercetin. Figure 8 After heating for 120 minutes (E), the retention rate of free quercetin was only 63.77%, while Qu@ZIF-8 retained 72.38%. All polysaccharide-modified systems exhibited superior thermal protection, with Qu@ZIF-8 / Fu showing the highest retention rate (90.66%), followed by Qu@ZIF-8 / TFP at 89.84%, and Qu@ZIF-8 / LBP at 87.75%. These results collectively demonstrate that the surface polysaccharide layer not only effectively maintains the colloidal integrity of nanoparticles under thermal conditions through steric hindrance and electrostatic stabilization mechanisms, but its dense hydrophilic interface also acts as a thermal barrier, reducing direct heat transfer to the drug core and thus significantly delaying the thermal degradation kinetics of the drug. In summary, polysaccharide functionalization is proven to be an effective strategy for improving the thermal stability of ZIF-8-based nanocarriers.

[0057] Storage stability of 2.7 nanoparticles The effect of storage time on NPs is shown in the figure. During the 14-day storage period, the hydrodynamic particle size of all nanoparticles gradually increased with time. Among them, the particle size of unmodified Qu@ZIF8 increased significantly from 308.1 nm to 429.4 nm, and the PDI increased from 0.184 to 0.366, while the Zeta potential decreased from 17.1 mV to 15.3 mV, indicating that the particles underwent significant aggregation and distribution. Figure 9 A). In contrast, the polysaccharide-modified system exhibited superior colloidal stability. Specifically, the particle size of the fucoidan-modified Qu@ZIF8 / Fu increased from 363.9 nm to 426.2 nm, while the PDI only decreased from 0.182 to 0.264, and the Zeta potential only decreased from -30.4 mV to -27.2 mV. Figure 9 B); The particle size of the Tremella fuciformis polysaccharide-modified system Qu@ZIF-8 / TFP increased from 364.1 nm to 428.0 nm, the PDI increased from 0.189 to 0.286, and the Zeta potential decreased from -26.2 mV to -23.3 mV. Figure 9 C), the particle size of the Lycium barbarum polysaccharide-modified system Qu@ZIF-8 / LBP increased from 384.4 nm to 488.3 nm, the PDI increased from 0.253 to 0.337, and the Zeta potential decreased from -26.3 mV to -22.2 mV. Figure 9 (D) These results show that the polysaccharide shell effectively inhibits the long-term aggregation behavior of particles, and in terms of surface charge, the polysaccharide-modified system exhibits a high negative potential, indicating that the polysaccharide layer provides a durable electrostatic repulsion barrier, which helps maintain the colloidal dispersion stability.

[0058] Furthermore, the drug retention results further confirm the superiority of polysaccharide modification. Figure 9After 14 days of storage, the retention rate of free quercetin was only 68.06%, compared to 81.04% for unmodified Qu@ZIF8. In contrast, the polysaccharide-modified systems all maintained high retention rates, with Qu@ZIF-8 / Fu and Qu@ZIF-8 / TFP reaching 92.08% and 92.79%, respectively, and Qu@ZIF-8 / LBP reaching 90.16%. These results indicate that polysaccharide surface functionalization significantly delays the aggregation and sedimentation of nanoparticles during storage, greatly improving the long-term storage stability of the drug. In conclusion, polysaccharide modification is an effective strategy for enhancing the storage stability of ZIF8-based nanocarriers.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles, characterized in that, Includes the following steps: Equal volumes of ZIF-8 suspension loaded with polysaccharide solution were mixed and reacted for 30-120 min. After centrifugation, the precipitate was collected, washed, and polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles were obtained. The pH values ​​of the polysaccharide solution and the ZIF-8 suspension loaded with quercetin are both 5 to 7. The polysaccharide in the polysaccharide solution is any one of fucoidan, tremella polysaccharide and wolfberry polysaccharide; The mass ratio of ZIF-8 loaded with quercetin to the polysaccharide is 1~4:1:

4.

2. The method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles according to claim 1, characterized in that, The concentrations of the fucoidan solution and the wolfberry polysaccharide solution are 2 mg / mL to 8 mg / mL; The concentration of the Tremella polysaccharide solution is 1 mg / mL to 4 mg / mL.

3. The method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles according to claim 1, characterized in that, Equal-volume mixing of polysaccharide solution loaded with quercetin ZIF-8 suspension refers to adding the polysaccharide solution dropwise into the quercetin-loaded ZIF-8 suspension.

4. The method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles according to claim 1, characterized in that, The specific process for obtaining the ZIF-8 suspension loaded with quercetin is as follows: Quercetin, organic ligands, zinc salts and stabilizers were stirred and reacted in an alcoholic environment for 15 min to 30 min. The precipitate was collected by centrifugation and dried to obtain ZIF-8 loaded with quercetin. The mass ratio of quercetin, organic ligand, zinc salt, and stabilizer is 170~330:75~150:75~150; The quercetin-loaded ZIF-8 was redissolved in water to obtain a quercetin-loaded ZIF-8 suspension.

5. The method for preparing polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles according to claim 4, characterized in that, The organic ligand is 2-methylimidazole, the zinc salt is zinc nitrate, and the stabilizer is polyvinylpyrrolidone.

6. A polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticle prepared by the method described in any one of claims 1 to 5.

7. The use of the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles as described in claim 6 in the preparation of anti-inflammatory drugs.

8. The application according to claim 7, characterized in that, The release rate of the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles in intestinal fluid was 73.17%~82.08%.

9. The application according to claim 7, characterized in that, The release rate of the polysaccharide-modified quercetin@ZIF-8 core-shell nanoparticles in gastric juice was 23%~32%.

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