Synthesis Of Nano-delivery Systems For Nitric Oxide Delivery And Tumor Therapy

Since the FDA approved the first liposome-based cancer nanomedicine Doxil in1995,chemotherapy on the basis of nano-delivery vehicles has achieved remarkable results.The delivery of chemotherapeutic drugs using nano-delivery vehicles at the size of nano level can not only reduce the adverse effects caused by them,but also increase the targeted delivery of the loaded drugs to tumor sites.However,the premature leakage of chemotherapeutic drugs and the problem of cancer multidrug resistance caused by long-term chemotherapy are still the major issues needed to be solved urgently for nanomedicines.In recent years,endogenous nitric oxide（NO）gas molecules have been proven to exert good anti-tumor effects,while not easy to cause drug resistance,which is regarded to be a new and effective treatment paradigm against tumors.However,how to efficiently load NO with a short half-life and diffusion distance and achieve its subsequent accumulation at the tumor site is still the key point of NO-based anti-tumor therapy.Therefore,in this project,we aim to construct nano-delivery systems with good biocompatibility for efficient targeted delivery of NO and subsequently to study their potential for tumor diagnosis and treatment.The specific research contents are as follows:1.The biomimetic nano-platform with light-activated NO production properties for tumor gas therapy:The anti-tumor efficacy of NO mainly depends on its own concentration,where high concentrations（>1μM）of NO can directly exert tumor-killing effects.On the basis of this,we firstly synthesized mesoporous polydopamine microspheres（M-PDA）with high specific surface area following the template method to load the light-sensitive NO donor molecule N,N′-di-sec-butyl-N,N′-dinitroso-1,4-phenylenediamine（BNN6）.Subsequently,the red blood cell membrane（RBCm）was coated on the surface of the BNN6-loaded M-PDA to construct the biomimetic NO delivery vehicle（M/B@R）for targeted delivery of NO and subsequent tumor therapy.Benefiting from the good biocompatibility of RBCm,M/B@R can achieve long circulation in vivo and be enriched in tumors.After exciting by near-infrared light（NIR）irradiation,M/B@R could overproduce NO to efficiently kill tumor cells.The chemical structure and morphology of the NO delivery carrier were characterized by means of transmission electron microscopy（TEM）,FT-IR and dynamic light scattering analyzer（DLS）;The loading capacity of BNN6 and follow-up NO release behavior were monitored by UV-vis and microplate reader;The long circulation time of M/B@R after administration in vivo and its subsequent biodistribution were verified by ICP-ms and in vivo small animal imager;The anti-tumor efficacy carried by M/B@R and its biocompatibility were measured by cytotoxicity,apoptosis experiment,in vivo anti-tumor experiment,etc.The experimental results showed that the M/B@R nanosystem can efficiently load NO donor molecule BNN6,and exhibited light-activated NO release behavior;After intravenous administration,M/B@R could achieve long circulation in the body and then accumulate into tumor sites;Without the help of chemotherapeutic drugs,M/B@R nanosystem could significantly inhibit the proliferation capacity of tumor cells and induce cell apoptosis after NIR irradiation;The cell experiments,serum biochemistry analysis and tissue sections further confirmed that the prepared M/B@R nanosystem had good biological safety.The light-activated NO delivery system is expected to provide new paradigms for the treatment of tumors.2.Construction of a self-sensitizing photodynamic nano-platform in combination with NO for tumor photodynamic therapy（PDT）:Based on the effect of NO monotherapy in the previous chapter,a covalent organic framework（COF）with photosensitizer porphyrin molecule as the structural unit was designed and developed,further loading NO donor molecule BNN6,and coating with MnO₂ to construct a tumor microenvironment-responsive photodynamic nanoplatform C/B@M for tumor PDT.The outer MnO₂ coating will degrade under H₂O₂ that was highly expressed in the tumor microenvironment to release O₂ to alleviate the hypoxia,thereby enhancing the therapeutic effects.Moreover,the introduction of NO plays a synergistic/sensitizing effect to improve the PDT effects.The morphology and composition of C/B@M were assessed by TEM,FT-IR,UV-vis,and DLS.The degradation performance of the MnO₂ coating was characterized by UV-vis and dissolved oxygen measurement experiments,and the photodynamic effect of the prepared nanocarrier under the excitation of 660-nm laser was further evaluated by the SOSG fluorescent probe.The NO release behavior controlled by laser of C/B@M was verified by Griess reagent.A series of cell-related experiments were conducted to evaluate the biocompatibility of C/B@M as well as its toxic effects on B16-F10 cells.This study proposed a self-sensibilizing photosensitizer molecules-based multifunctional nano-platform with synergistic effects with NO,providing a new paradigm for tumor treatment.