Multifunctional Nano-drug Delivery System Based On Metal-phenolic Networks For Tumor Therapy

Background and ObjectivesCancer has become a major public health problem that threatens human health.Clinically commonly used radiotherapy,chemotherapy and surgery are often limited to side effects,multidrug resistance,tumor metastasis and recurrence.The development of nanotechnology provides a new opportunity for antitumor therapy,and nanomedicine has been obtained widely concerned in cancer theranostics.The nanosized carrier can effectively deliver a variety of drugs,meanwhile improving the bioavailabolity,enhancing the antitumor effect and reducing the side effects.However,the conventional nanoparticles were limited by complicated preparation process,low drug loading capacity,immunogenicity and long-term toxicity,and the development and design of novel multifunctional nanomaterials with biocompatibility could realize safer and efficient cancer therapy.Metal-phenolic networks（MPNs）,as supermolecular framework nanomaterials coordinated by metal ions and polyphenols,have many advantages,including excellent durg loading performance,bioadhesion and biocompatibility.More importantly,the metal ions and polyphenols also can be applied for versatile cancer theranostics.Therefore,MPNs are potential nanomaterial for drug delivery and tumor treatment.In order to explore the application of MPNs in cancer therapy,three MPNs-based drug delivery strategies are proposed,which is aimed to combine multiple treatment means and overcome the limitations of tumor microenvironment,thereby achieving enhanced cancer therapy.Method and Results1.The MPNs-based shell-core nanosystem enhances PDT against hypoxic tumor via oxygen self-supply and HIF-1αinhibition.The pure drug nanocore composed of rapamycin（RAP）and chlorin e6（Ce6）was prepared via solvent exchange method,then the core-shell nanosystem（RC@TFC）was constructed by coating catalase（CAT）-loaded MPNs onto the nanocore.The size,morphology,drug loading and release behavior of RC@TFC were characterized.The nanoparticles showed obvious shell-core structure,with the particle size of 239.3 nm,and the total drug loading was up to 60%.Meanwhile,the nanoparticles showed sustained drug release profile.The CAT activity,oxygen and singlet oxygen（¹O₂）production capability of RC@TFC were investigated.The results showed that the nanoparticles can protect CAT from protease digesition,and generate oxygen by decomposing H₂O₂ for photodynamic conversion,thereby increasing the ¹O₂ production.MDA-MB-231 breast cells were selected to evaluate the cellular uptake,intracellular ROS generation and in vitro antitumor activity of RC@TFC.The nanoparticles were effectively uptaken by tumor cells,and showed strong cytostatic activity via producing ROS under laser irradiation.Western blot study indicated that RC@TFC downregulated hypoxia-inducible factor-1α（HIF-1α）.The subcutaneous MDA-MB-231 cancer model was constructed and in vivo biodistribution was investigated by living flurescence imaging.The results showed the accumulation amount of nanoparticles in the tumor sites was significantly higher than that of free drug.Moreover,the antitumor activity and biosafety of RC@TFC were valuated.The results indicated that nanoparticles can suppress and ablate tumors,and the HIF-1αexpression in the tumor tissues was reduced by78.9%.In addition,RC@TFC showed negligible side effect on normal tissues.2.Hybrid cyclic nano-reactor for starvation/PDT combinational therapyThe PLGA/MPNs hybrid nanocarrier（PTF）was prepared via solvent exchange and self-assembly method,and PTF can efficiently load Ce6,Nile red（NR）and glucose oxidase（GOx）.The GOx and Ce6 co-loaded nanosystem（PTFCG）was modified with Mn O₂ via reduction method,subsequently coated with hyaluronic acid（HA）via electrostatic interaction,the nano-reactor（PTFCG@MH）was obtained.The size,ζpotential,morphology,surface element,drug loading and release behavior of PTFCG@MH were characterized.The nano-reactor showed shell-core structure,and its surface has wrinkled Mn O₂.The PTFCG@MH exhibited the particle size of 206.3 nm and theζpotential of-21.7 m V,and the Ce6and GOx loading was 108.4μg/mg and 24.6μg/mg,respectively.In addition,the nanoparticles showed a burst drug release after incubating with glutathione（GSH）.The PTFCG@MH-midiated cyclic catalytic reaction was investigated by monitoring the glucose consumption,O₂ concentration and p H change.The results indicated that GOx consumes glucose and O₂ to generate H₂O₂,as well as decrease the p H.The produced H₂O₂ is decomposed by the Mn O₂to generate O₂,which in turn supplies GOx catalytic reaction and photodynamic conversion.This nano-reactor can maintain O₂ balance and achieve cyclic O₂ supply during cyclic catalytic reaction.MDA-MB-231 breast cells were selected to evaluate the cellular uptake behavior and mechanism of PTFCG@MH.The nanoparticles selectively recognized tumor cells via CD44 receptor for efficient uptake,and internalized via clathrin-mediated endocytosis.In vitro antitumor activity study showed that PTFCG@MH relieved intracellular hypoxia,and produced ROS under laser irradiation,and depleted intracellular ATP and GSH,thereby inducing cancer cells apoptosis and necrosis.During the treatment of subcutaneous MDA-MB-231 tumor,the nanoparticles effectively accumulated into tumor sites,significantly suppressed tumor with excellent biosafety.3.DNAzyme-loaded Fe/Mn-MPNs for cyclically amplified tumor ferroptosis/PTT/immunotherapyThe DNAzyme（DZ）-loaded Fe/Mn-tannic acid（TA）networks（DZ@TFM）were prepared via self-assembly method.The size,morphology,surface element,drug loading of DZ@TFM were characterized.The nanoparticles showed irregular structure,with the particle size of 149.3 nm,meanwhile the P,Fe and Mn elements were observed on the surface.In addition,DZ@TFM protected CAT from nuclease decomposition,and triggered Fenton reaction by facilitating Fe³⁺/Fe²⁺conversion,and caused photothermal thansform under laser irradiation（η=32.1%）.The DZ cleavage study indicated that Mn²⁺was introduced to act as metal cofactor of DZ.B16F10 melanoma cells were selected to evaluate the anticancer effect and mechanism of DZ@TFM.The results showed that the nanoparticles increased intracellular ROS and lipid peroxidation（LPO）level,thereby inducing cell ferroptosis.Meanwhile,the nanoparticles caused photothermal effect to kill cancer cells,along with immunogenic cell death（ICD）.Moreover,IFN-γfacilitated cell ferroptosis via inhibiting SLC7A11,thereby enhancing the anticancer effect of DZ@TFM.The subcutaneous B16F10 cancer model was constructed to investigate the in vivo immune response and anticancer activity of DZ@TFM.The results showed that PD-L1 was successfully silenced by DZ@TFM,which synergized with ferroptosis/photothermal effect-induced ICD,thereby boosting anticancer immune response,leading to dendritic cells（DCs）maturation,effector T cells activation and cytokines secretion.Cell ferroptosis was enhanced by IFN-γ,achieving cyclically amplified tumor ferroptosis-immunotherapy.Finally,both primary and distant tumors were effectively suppressed with significantly prolonged survival rate.ConclusionIn summary,three MPNs-based delivery nanoplatforms were construted.Owing to the biocompacibility,excellent drug loading performance and multiple treatment function of MPNs,enhanced anticancer outcomes were achieved by combining various therapy means and overcome the limitation of tumor microenvironment.Therefore,the MPNs exhibit superior application potential in cancer therapy and provide a novel strategy for codelivery of multiple drug,as well as provide novel theories and ideas for the development of safe and efficient nanomedicine.