Preparation And Applications Of Multifunctional Liposomes For Responsive Regulation Of Tumor Microenvironment

Liposomes,as the most widely used nanocarriers for drugs in clinical practice,have saved the lives of thousands of cancer patients and greatly reduced their pain.However,traditional liposomal nanodrugs suffer from the side effects on normal tissues because of their undesired releasing behaviors nearby the tumor lesions.Tumor microenvironment(TME)plays an important role in tumor cell growth,migration,and metastasis.It is a frontier direction in cancer research to design liposomal nanodrug delivery systems being responsive/regulating to TME for the improved therapeutic efficacy.In my thesis,a series of liposomal nanodrug carriers have been developed to target at the characteristic parameters of TME,such as slightly acidic pH,higher levels of Reactive Oxygen Species(ROS),relatively higher concentrations of Glutathione(GSH),etc.Their therapeutic effects have been validated by the tests on the regulation of TME and amplified ROS generation for tumor ablation.The biological safety of the liposomal nanodrug carriers have been evaluated.The synergistic effects of combined therapies have been explored by using in vivo experiments.My thesis includes the following research contents:Chapter 1:The characteristics of liposomal nanodrug delivery system;tumor microenvironment and its impacts on tumor therapies;and the methods to improve the effect of chemodynamic therapies are briefly reviewed.The rationale of the project designs and the main research contents of my thesis are described in this chapter.Chapter 2:I have developed ROS activated intelligent liposomes integrating photodynamic therapy and chemodynamic therapy for regulation of TME.Through the production of ROS,oxidative damage is castonto tumor cells,leading to apoptosis of tumor cells.In this project,I have developed a ROS-activated intelligent liposome(RALP)composed of a skeleton of unsaturated double bond containing soft egg yolk phospholipid(EPC),a thioketal bond conjugated 808 nm(near infrared(NIR))dye Cy and mPEG,simultaneously loaded with 7 nm Fe3O4 nanoparticles and cisplatin prodrug HOC.The RALP can be activated by ROS for rapid release of Fe3O4 and HOC,while increasing their retention and penetration in tumors.The released Fe3+and Pt4+ consume GSH,while being reduced to Fe2+and Pt2+by GSH.The amplification of ROS has been demonstrated to be critical for the synergistic enhancement of chemodynamic therapy and photodynamic therapy.In this project,the individual components of RALP have smartly been integrated for regulation of the tumor microenvironment,thus allowing for enhanced therapeutic effect and potential of clinical translation.Chapter 3:Inhibition of hypoxia inducible factor-1(HIF-lα)expression triggers ROS FET amplification of ROS output for tumor therapy.In this project,we have proposed a novel strategy to enhance the efficacy of chemodynamic therapy by inhibiting HIF-lα expression and triggering ROS field effect transistors(FET).The liposomal nanocarrier is loaded with HIF-1α inhibitors SN-38,Fe3O4 and GOx(Glucose oxidase,GOx).SN-38 acts as a "gate electrode" to inhibit HIF-lα expression to activate ROS FET and reduces the defense of tumor cells against ROS and clearance of ROS.GOx,as a“source electrode",can catalyze glucose to produce glucose acid to reduce pH and produce hydrogen peroxide to enhance Fenton reaction efficiency and achieve ROS output amplification.The "drain electrode" includes the proteins on the mitochondria,inside the cytoplasm,or the DNA in the tumor cell nucleus,which are recipients of the destructive ROS flux.In our design,ROS FET can not only suppress tumor cells from adapting to tumor hypoxia and ROS annihilation by down-regulating HIF-1α expression,but also promote the production of highly toxic ·OH and achieve efficient tumor ablation.Chapter 4:Studies on the integration of calcium overload and ROS production for tumor therapy.In this project,we report a multi-response enzyme-catalyzed CaCO3liposome drug delivery system that responds to the tumor microenvironment by selfaccelerating release,forming a pH-triggered positive feedback effect to achieve a closedloop for production of ·OH and effectively kill tumors.Cascades of amplified ROS and large amounts of calcium ions can damage the functions of calmodulin and calciumrelated ground ion channels as well as inhibit ROS-reducing enzymes,and achieve CDTenhanced ROS cascade amplification.They lead to mitochondrial dysfunction and sufficient ablation of tumors in vivo.Chapter 5:Preparation of self-supplied H2S hemoglobin nanoparticles and research on enhanced drug delivery in promoting tumor vascular normalization.In this project,I have prepared macrophage membrane coated,self-supplied hydrogen sulfide producing hemoglobin nanoparticles,which can selectively target tumor sites and improve vascular normalization by releasing hydrogen sulfide(H2S),facilitating delivery of M@Hb-S to tumors.The improvement of hypoxia can also produce a large amount of highly toxic·OH through iron-mediated Fenton reaction,which can cause persistent killing to tumors.Compared with the control liposomal sample(Lipo@Hb-S),macrophage membranecoated liposomes(M@Hb-S)have better tumor targeting ability and tumor enrichment effect,promising clinical translation in the future.Chapter 6:A summary of my thesis.In brief,I have prepared a series of intelligent liposomalnanocarriers responsive to tumor microenvironment,which can be released quickly after their arrival at the tumor sites,therefore reducing the toxic and side effects caused by traditional lipids on normal cells.By regulating TME(including hypoxia,H2O2,high concentration of GSH,pH,abnormal tumor blood vessels,etc.),new strategies and methods for ROS amplification have been developed in my PhD thesis to improve the efficacy of anti-tumor therapy and elevate the possibility of clinical translation in the future.