Construction And Study Of Quercetin Delivery System Based On CuS@MOF

Cancer is a global public health issue threatening human health seriously nowadays,and morbidity of it increases year by year.Among various treatments,chemotherapy is one of the most effective methods.However,most anticancer drugs have severe side effects and may cause the generation of multi-drug resistance in clinic.Quercetin,a phytogenic flavonoid,is widely found in Chinese herbs and food.Recent researches found that quercetin can inhibit the proliferation and induce apoptosis of many kinds of cancer cells by regulating tumor suppressor gene expression,blocking cell cycle,inducing apoptosis,arresting invasion and metastasis.In addition,quercetin exerts negligible cytotoxicity against normal cells compared to traditional chemotherapeutic agents.However,the anticancer effect of quercetin has been greatly restricted by its poor bioavailability,which is caused by low water-solubility and chemical instability in the neutral and alkaline medium.Therefore,it is significant to develop a safe and effective quercetin delivery system to improve the water solubility and chemical instability of quercetin.Zeolitic imidazolate framework-8(ZIF-8)is a kind of metal organic frameworks(MOFs)with the advantages of high porosity,large specific surface area,regular pore size,adjustable pore size.In addition,it has good stability under neutral and alkali conditions,while disintegrating under acidic conditions.It is an ideal drug carrier which could achieve drug loading through coordination.Photothermal therapy is an emerging method of cancer treatment,which has the advantages of minimally invasive,safe and efficient compared to traditional treatment methods.Recently,much effort has been made to construct composite nanoparticles as chemo-photothermal therapy platforms to enhance the therapeutic efficacy and to decrease the multidrug-resistance of cancer cells.In recent years,CuS NPs have been reported to encapsulate in the framework of ZIF-8 without obvious influencing the drug loading or altering its pH-sensitive property.Based on the above research background,we constructed a quercetin drug delivery system based on copper sulfide-metal organic framework materials:CuS@ZIF-8 was synthesized through in situ growth of ZIF-8 around PVP-modified CuS NPs,following encapsulating quercetin via chelation interactions,then modified with bovine serum albumin-folic acid conjugate(FA-BSA)as a targeting agent and stabilizer.Eventually,quercetin drug-loading system with active targeting and pH sensitivity for combination therapy of quercetin and photothermal therapy were obtained and it was evaluated in vivo and in vitro.The main research contents,methods and conclusions are as follows:A pH-responsive delivery system for co-delivery of quercetin and CuS NPs(FA-BSA/CuS@ZIF-8-QT NPs)was synthesized and characterized.CuS NPs were obtained by hydrothermal synthesis,in which PVP was used as the growth template.ZIF-8 would grow around CuS NPs to form the CuS@ZIF-8 NPs with the coordination reaction between 2-methylimidazole(2-MI)and Zn(NO3)2.Then the quercetin loading was performed by introducing via chelation interactions.Finally,the drug-loading nanoparticles were modified with FA-BSA conjugate which was synthesized via amide bond as targeting agent.Fourier transform infrared spectroscopy(FT-IR)was used to verify the successful synthesis of the product.The morphology of nanoparticles was observed by transmission electron microscopy(TEM)and scanning electron microscopy(SEM).The particle size distribution of nanoparticles was measured by dynamic light scattering(DLS).The results showed that the prepared nanoparticles exhibited uniform spherical morphology with uniform particle size and good dispersion.The particle size was 45.1 ± 15.0 nm,and the Zeta potential was-27.9 ± 6.0 mV.The stability of quercetin was studied by the change of ultraviolet absorbance.The stability experiment indicted that the nano-delivery system effectively improved the chemical instability of quercetin.The results of in vitro photothermal temperature increasing experiment suggested that formulation exhibited satisfactory photothermal effect,which met the requirements of photothermal therapy.After fully disintegrated in diluted hydrochloric acid,the drug loading capacity of quercetin was determined to approximately 24%.In vitro release experiments indicted that the formulation had a pH-responsive and NIR-induced release behavior.The results of hemolysis test indicted that the preparation had good blood compatibility.B16F10 mouse melanoma cells were selected as tumor model cells for in vitro anti-tumor evaluation.In order to study the cellular uptake behavior of the formulation,IR820,a fluorescent dye,was used to label the nanoparticles.The cellular uptake of the formulation was qualitatively and quantitatively analyzed by inverted fluorescence microscopy and flow cytometry respectively.The experimental results indicated that FA-BSA/CuS@ZIF-8-IR820 exhibited remarkable more efficient cellular uptake behavior than IR820 and CuS@ZIF-8-IR820,which would be ascribed to the passive targeting ability and FA receptors(FR)-mediated endocytosis.The results of in vitro cytotoxicity test and cell apoptosis assay indicated that photothermal therapy combined with chemotherapy exhibited better anticancer effect than chemotherapy or PTT alone.Finally,the mice bearing B16F10 tumor were used as tumor models for in vivo anti-tumor evaluation.The in vivo biodistribution experiments indicated that FA-BSA/CuS@ZIF-8-QT NPs had good tumor accumulation ability.The results of in vivo anti-tumor efficacy assay indicted that the chemo-photothermal treatment had distinctly superior anticancer effect over the chemotherapy or PTT alone.In addition,histological analysis showed that the most severe apoptosis and necrosis of tumor cells could be observed in chemo-photothermal treatment group,while no significant abnormality was found in the maj or organ sections.In summary,a pH-sensitive quercetin drug delivery system based on copper sulfide-metal organic framework material was constructed and systematically studied.This system can achieve satisfactory drug loading,overcome the drawbacks low water-solubility and chemical instability of quercetin,fulfill synergistic combination of chemotherapy and PTT via co-delivery of quercetin as anticancer agent and CuS nanoparticles(NPs)as photothermal therapy(PTT)agent,and finally enhance antitumor effect as well as reduce toxic side effect.The multifunctional quercetin delivery system in this paper provides an effective solution to exert the medicinal value of quercetin.Therefore,this research topic has important theoretical and practical significance.