Regulating Autophagy And Tissue Penetration For Enhanced Antitumor Photothermal Therapy

Photothermal therapy?PTT?as a new kind of tumor therapy is widely studied because of the advantages of good effect,non-invasiveness and small side effects by converting near-infrared light?NIR?energy into thermal energy.At present,a large number of photothermal nano-agents with good effect and low toxicity have been widely used in the treatment of various types of tumors.Although PTT has shown a wide application prospect,there are still some problems to be solved.The tumor microenvironment is hypoxia,ischemia,intercellular density and high tumor pressure that cause low efficiency and difficulty of deep tumor destruction by PTT.With well understanding the role of autophagy,through inhibition of cellular protective autophagy,or promoting excessive autophagy in cel s to trigger apoptosis autophagy will significantly improve the efficacy of tumor therapy by PTT.Furthermore,increasing the tumor penetration will produce a deep homogenization of heat effect and more helpful to kill deep tumor cel s,that avoids uneven heat caused incomplete tumor destruction.In addition,photothermal nano-agents have the potential of multimod a l therapeutics to enhance the efficacy of PTT through combining chemical drug,radiotherapy and photodynamic therapy.The contents of this dissertation are summarized as follows:Chapter 1:This part introduces the present condition of the cancer therapy,the main problems of PTT and solving strategies.The end of part describes the content of this dissertation.Chapter 2:Cells produce protective autophagy in the period of PTT.Inhibition the autophagy will improve the efficacy of PTT.We loaded the autophagy inhib itor chloroquine?CQ?on the surface of polydopamine nanoparticles?PDA?via the?-?accumulation and prepared PDA/CQ nanoparticles.CQ can be released under acidic conditions,indicating that PDA/CQ can respond to tumor acid environment and improve the organizational accuracy of CQ release.The converting of autophagic protein LC3 and TEM images confirm that PDA/CQ works through inhibit autophagy.PDA/CQ inhibits cell autophagy process and enhances the sensitivity of the heat killing in vitro.In animal experiments,PDA-PEG/CQ treated group plus NIR fully suppressed the tumor growth compared other groups.In the whole period of treatment no side effects was be found.In this study,inhibiting cel s autophagy to enhance the sensitivit y of heat provides a new perspectives for tumor PTT.Chapter 3:Chapter 2 shows inhibiting cell autophagy can increase the effects of tumor PTT and improve the sensitivity of heat during tumor treatment.On the contrary,promoting cell autophagy may also is a feasible method to improve the effects of tumor PTT.We use RGD modified polydopamine targeted delivering autophagy promoting peptide Bec?PPBR?to tumor cel s to induce apoptosis autophagy occurring under photothermal therapy?PTT?,that eventually lead to tumor cell death.PPBR solves the problem of the tissue distribution and solubleness of Bec.In vitro experiments show that,compared to PP and Bec,PPBR specifically targets tumor cel s with increasing cel ular uptake and causing autophagy,which significantly improves the efficacy of PTT.For tracking the tissue distribution of PPR in vivo we prepared PPR@Fe through chelating Fe³⁺into PDA internal.PPR@Fe also have the ability of magnetic resonance imaging?MRI?and optical acoustic imaging?PAI?in vivo.Animal experiments showed that PPBR significant suppressed tumor growth through targeted PTT and apoptotic autophagy in tumor.In the whole experiment PPBR shows no toxicity.In a word,we prepared multifunctional therapeutic,which possess biological safety,multimod a l images and durg delivery,enhanced sensitivity of PTT through promoting cell autophagy.Chapter 4:The penetration of photothermal nanoparticles in the tumor tissue is an important aspect in efficient tumor PTT.The hyaluronic acid?HA?and collagen in tumor tissue blocks the penetration of nanoparticles in tumor.By degrading the hyaluronic acid and reducing the interstitial density of tumor tissue can improve the penetration of nanoparticles in tumor tissues.Hyaluronidase?HAase?,which can specific degradation of HA,was modified on the surface of the PEGylated polydopamine?PDA?,namely PP-HAase.We prepared a gel comprising HA and 3D cel ular model with HA high expression to simulate tumor microenvironment to test the penetration of PP-HAase in vitro.Results show that PDA-HAase degrades HA and penetrating deeper distance.In animal experiments,PP-HAase treated mouse can still heated to 44 ^oC at tumor post vein injection 48 and 72 hours.The results show that PP-HAase enhances the PDA retention in tumor tissue.The tumor section also confir med that HA was degraded by PP-HAase,and the apoptosis was significantly higher than that of other treatment groups after PTT.In a word,we prepared PP-HAase,which can degrade HA and increase the PDA penetration in tumor tissue.PDA-HAase enhance the PDA stranded in tumor and shows significant tumor suppressive effect by PTT.Chapter 5:In this chapter,we further study regulating the tumor penetration for high efficiency tumor therapy by PTT.Losartan is a clinical drug used to reduce blood vessel pressure.We deliver losartan to the tumor tissue to increasing tumor penetration through reducing tumor blood vessel pressure.The PDA can load Losartan?PLST?and Losartan can be released from PLST in an acidic solution.In vitro experiment PLST shows significantly down-regulated collagen related gene,indicates that PLST could degrade collagen as result of low density of ECM and low pressure of the tumor blood vessels,which will increase tumor penetration.The distribution of PLST in mouse shows PLST increase the concentration of photothermal nanoparticles in tumor.PLST reduces tumor pressure in vivo and maintains a high PTT temperature even post i.v.injection 48 and 72 hours.PLST promotes the tumor penetration and enhances PTT efficiency through reducing tumor pressure by degrading the collagen in the tumor.Chapter 6:Summarize the full text and give the prospect of tumor PTT by regulat ing cel s autophagy and increasing the tumor penetration.There are still many chal e nges in tumor PTT.Multi-strategy combination therapy is still the trend in the developme nt of PTT in the future.To develop new and safe photothermal agents,to build a tumor model that is close to clinical research,and strive to develop efficient and univers a l PTT concept,all togrther will contribute to cancer breakthrough.