Combination Nanomedicine To Overcome Tumor Hypoxia Through Phototherapy-Enhanced Synergistic Effect

Hypoxia is a trademark characteristic of most solid tumors.The existence of hypoxia inside solid tumors has a serious limiting effect on therapeutic efficacy including chemotherapy and photodynamic therapy.Therefore,there is an urgent need to develop effective therapeutic strategies to enhance the therapeutic efficacy of chemotherapy and photodynamic therapy in hypoxic environments to inhibit tumor growth.This paper focuses on the development of novel nanocarriers that overcome the hypoxic environment of tumors based on the synergistic effect of phototherapy combined with other therapeutic modalities to improve the therapeutic efficacy of nanomedicines on hypoxic tumors.Abstracts of the work presented each chapter are as follows:Chapter ⅠHypoxia as a distinctive feature of tumor microenvironment,plays a pivotal role in tumor invasion,migration and resistance to conventional cancer therapies like chemotherapy,radiotherapy,photodynamic therapy,immunotherapy etc.In this chapter,as the research background of this thesis,we summarized the causes of hypoxia in tumor tissues,hypoxia-responsive nanocarrier systems,research progresses on nanocarrier construction strategies for overcoming hypoxia to enhance the effect of photodynamic therapy,as well as nanoparticles that integrated photodynamically exacerbated tumor hypoxia with hypoxia-responsive drug activation.Based on the summary of these research results,the research proposals of this topic were put forward.In the research topic of this dissertation,we construct novel polyprodrug nanocarriers that improved hypoxiaresponsive drug release through photodynamic therapy and photodynamically enhanced hypoxic microenvironment,as well as covalent organic framework(COF)nanoparticles with photothermal and photothermal-promoted oxygen-independent singlet oxygen storage and release.The research in this thesis aims to develop novel nanocarriers to overcome tumor hypoxia and achieve efficient therapy.Chapter ⅡThe hypoxic environment inside the tumor is closely related to tumor growth,metastasis and drug resistance.The hypoxic microenvironment limits the therapeutic efficacy of various oxygen-dependent therapies,such as radiotherapy and photodynamic therapy.On the other hand,the uneven distribution of hypoxic regions also limits the efficacy of hypoxia-responsive chemotherapy drugs.Herein,we constructed the hypoxia-activable block copolymer polyprodrugs which are composed of poly(ethylene glycol)(PEG)and copolymerized segments of ortho-nitrobenzyl linked camptothecin(CPT)methacrylate and 2-(piperidin-1-yl)ethyl methacrylate(PEMA)monomers.After self-assembly in aqueous solution,indocyanine green(ICG)photosensitizers are encapsulated to formulate ICGloaded micellar nanoparticles(ICG@CPTNB)for near infrared(NIR)light-boosted photodynamic therapy(PDT),tumor hypoxia aggravation,and responsive drug activation.In vitro studies demonstrate the excellent hypoxia-specific activation of ICG@CPTNB and concurrent release of CPT.The nanoparticles are taken by cancerous cells within 24 h and high amount of intercellular CPT release is observed in hypoxia condition.Moreimportantly,laser irradiation further enhances the CPT release via increase production of intercellular ROS and elevating the hypoxia.Through intravenous injection and prolonged blood circulation,the nanoparticles can accumulate into tumor efficiently.Tumor aciditytriggered charge transition of PEMA units remarkably promotes cellular internalization of the nanoparticles.Upon exposure to NIR laser irradiation,ICG inside the nanoparticles produces reactive oxygen species(ROS)along with local hypothermia.Simultaneously,the oxygen consumption during ROS production aggravates the intratumoral hypoxia,which can amplify hypoxia-responsive self-immolative CPT release from the nanoparticles.The combined photodynamic-chemotherapy by using the hypoxia-responsive polyprodrugs nanoparticles,ICG@CPTNB,overcomes the limitations of single therapy of hypoxia-activable prodrugs and PDT,which remarkably improves the efficiency of tumor growth suppression.Chapter ⅢThe hypoxic environment of tumors severely limits the therapeutic effect of photodynamic therapy.At the same time,in the process of photodynamic therapy,continuous illumination will further lead to the enhancement of hypoxia,thereby reducing the effect of photodynamic therapy.Oxygen-independent photodynamic therapy can effectively solve this problem.Herein,we constructed singlet oxygen-stored nanoscale covalent organic framework(nCOF)nanoparticles which under near-infrared(NIR)laser irradiation,endows oxygen-independent singlet oxygen(1O2)production for synergistic PDT and photothermal therapy(PTT).The covalent organic polymer is prepared by using photosensitizer,5,10,15,20-Tetrakis(4-aminopheny 1)porphyrin(TAPP),1O2-carrying monomer 9,10-di(4-formylphenyl)anthracene(ANT)and poly(vinyl pyrrolidone)(PVP),followed by loading of cypate(Cy)to fabricate Cy@COF-1 nanoparticles covered by PVP.The COF-1 formation was extensively analyzed by FT-IR,XPS and CP-MAS 13C NMR experiments and BET nitrogen adsorption isotherm experiment demonstrated the surface nature of COF-nanocarrier.After loading into the porous structure of COF nanoparticles,the stability of cypate dyes were improved remarkably.After repeated irradiation of 808 nm laser,cypate can till perform excellent photothermal effect.Under 660 nm laser irradiation,1O2 was successfully stored in Cy@COF-1 and Cy@COF-2 nanoparticles were formulated.Upon 808 nm laser irradiation,the stored 1O2 can be release efficiently due to the local photothermal temperature increase.In comparison to Cy@COF-1 nanoparticles with either NIR 660 nm or 808 nm laser irradiation,Cy@COF-2 in the presence of 808 nm laser produces remarkably higher amount of intercellular reactive oxygen species(ROS)and demonstrates excellent cancer cell killing effect in both hypoxic and normoxic conditions.Simultaneously,Cy@COF-2 showed high stability under the physiological medium.After intravenous injection and tumor accumulation,with the help of 808 nm laser,Cy@COF-2 can improve the tumor temperature locally and release stored 1O2 inside tumors,which finally inhibited the tumor growth drastically.The established COF nanoparticles provide a paradigm to develop 1O2-stored and released COF nanoparticles with excellent photodynamic and photothermal capability for hypoxic tumor treatment.Chapter ⅣIn this chapter,the research contents of this thesis are summarized,and the characteristics and excellent properties of the multifunctional nanocarriers based on the synergistic effect of phototherapy-promoted combination therapy are analyzed.Moreover,we also compared them with the related systems in the literatures,and summarized the significance of the systems that we constructed to the field of phototherapy.Finally,the direction of future work related to phototherapy nanocarriers are proposed.