The Development And Mechanism Studies Of Single-agent Cancer Photodynamic Theranostics Systems

Most of current tumor photodynamic theranostics systems are developed based on“all-in-one”nanomedicine or drug-detector conjugates via nanotechnology or chemical means.These photodynamic theranostics systems can realize the co-delivery of different diagnostic reagents and photodynamic therapy(PDT)photosensitizers to achieve the on-demand theranostics of different tumors.However,these photodynamic theranostics systems also face various problems,such as complex preparation process,drug leakage,low delivery efficiency,and susceptibility to physiological environment.In addition,they emphasize imaging-guided drug activation or monitoring of drug delivery.The evaluation of antitumor effect depends on other imaging methods,such as X-ray computed tomography and magnetic resonance imaging,which is hard to evaluate early response in real time.Therefore,the development of a new single-agent photodynamic theranostics system combining dual functions of exceptional noninvasive tumor ablation capability and real-time anticancer efficacy-reporting characteristics would possess a great scientific significance and clinical value for accurate diagnosis and prognosis of cancer.In this thesis,we characterized the photodynamic theranostics characteristics of triphenylamine derivatives containing four pyridine salt(TPCI).We also investigated the mechanism of tumor cell death caused by photodynamic effect from TPCI.In addition,we developed a TPCI-mediated combined photodynamic-chemotherapy system to achieve the synergistic theranostics effect of large tumors.1.The photodynamic theranostics characteristics of triphenylamine derivatives TPCITPCI has an extremely high singlet oxygen(¹O₂)quantum yield of 98.6%,as well as excellent light stability and a property of aggregation-induced emission.In vitro studies have shown that TPCI holds low dark toxicity,and can easily bind with small grooves of DNA to increase its fluorescence intensity.TPCI can effectively kill a variety of tumor cells,and enter the nucleus of dead cancer cells simultaneously.The interaction between TPCI and DNA in the cell nucleus can significantly increase its fluorescence,so that it can report the cell death in real time.Moreover,we have validated the effective TPCI-based single-agent theranostics in different tumor-bearing mouse models.2.The mechanisms of cancer cell death caused by TPCI-mediated photodynamic therapyOur in vitro studies have showed that the cytotoxicity of TPCI-mediated photodynamic therapy(TPCI-PDT)can be regulated by a series of iron chelating agents,and TPCI-PDT can cause the accumulation of a large amount of LPO in He La cells.Futhermore,we have investigated the mechanisms of He La cells ferroptosis induced by TPCI-PDT,and proposed one possible pathway associated with the accumulation of lethal LPO in He La cells that leads to cell ferroptosis.The pathway is that TPCI-PDT may inhibit the synthesis of glutathione and deplete reduced glutathione(GSH),which consequently reduces the activity of glutathione peroxidase 4(GPX4)and impairs the clearance of LPO.3.The synergistic theranostics effect of TPCI-mediated combined photodynamic-chemotherapyTo overcome the issue of limited light penetration depth in photodynamic therapy,we have combined TPCI-PDT with a chemotherapy drug paclitaxel(PTX)to achieve synergically enhanced anti-tumor theranostics effect.We have prepared a liposome system loaded with TPCI and PTX(TPCI/PTX@Lipo).The liposomes enter the cells through endocytosis,and the uptake of drugs can be increased via the photochemical internalization effect.TPCI can light up the dead cells caused by TPCI-PDT or chemotherapy,therefore self-reporting the therapeutic response in real time.Meanwhile,TPCI/PTX@Lipo can induce PC3 tumor cells apoptosis synergistically via the mitochondrial pathway.The efficacy of PTX and TPCI in TPCI/PTX@Lipo treatment have been increased up to 30 folds and 5 folds respectively,compared with sole PDT or chemotherapy.The in vivo studies using a mouse model bearing PC3 prostate tumor cells have demonstrated the effective ablation of tumors with initial sizes of 200 mm³,as well as the precise early tumor response monitored by TPCI/PTX@Lipo.In conclusion,we have developed a highly effective photosensitizer that can not only kill neoplastic cells through PDT,but also real-time monitoring of anti-tumor efficacy.Moreover,TPCI-PDT leads to the depletion of cellular GSH,and GPX4 affects sensibility of He La cells to ferroptosis-meidated by TPCI-PDT.In addition,the photosensitizer has a good synergistic anti-tumor effect to ablate large tumor when combined with chemotherapy,and TPCI can also report the combined therapy effect in real time,exhibiting great potential as a self-reporting medicine for precise cancer therapy in clinic.