Studies On The Preparation Of Mn-doped Hollow Titanium Dioxide Nanoprobes And Enhanced Sonodynamic Therapy For Liver Cancer

Liver cancer is a major disease that seriously threatens people’s life and health.Traditional treatments such as surgery,radiotherapy and chemotherapy have high side effects and poor efficacy.Therefore,the development of new safe and effective treatment modalities is an important means to improve the current status of liver cancer treatment.Sonodynamic therapy（SDT）,which is based on the generation of reactive oxygen species by ultrasound stimulation of sonosensitizers to induce tumor apoptosis,is one of the most promising non-invasive treatment modalities.How to increase the level of reactive oxygen species in cancer cells is the key issue to be solved for SDT to effectively inhibit liver cancer.There are two main ways to regulate the intracellular reactive oxygen species level,one is to enhance the production of reactive oxygen species by designing high-performance sonosensitizers,and the other is to reduce the scavenging of reactive oxygen species by inhibiting the level of reduced glutathione in the tumor microenvironment.In this thesis,by combining the above two regulatory strategies,we significantly elevated the level of reactive oxygen species in cancer cells,which thus enhanced the effect of SDT in hepatocellular carcinoma.The main work is as follows:（1）Mn-doped hollow TiO₂（MHT）sonosensitizers with a homogeneous shape and highly dispersed were synthesized by a multi-step reaction with an inner diameter of about 80 nm and a thickness of about 20 nm.The Rk1@MHT-PEG nanoprobe was obtained by modification of MHT with ginsenoside Rk1 loaded and polyethylene glycol（PEG）.The doping of Mn reduced the band gap energy of TiO₂ from 3.2 e V to 3.0 e V,achieving a 1.3-fold and 2.5-fold increase in the yield of reactive oxygen species compared to undoped TiO₂and commercial TiO₂（P25）,respectively.Meanwhile,the doping of Mn conferred good T₁-weighted MRI performance of the nanoprobe（r₂/r₁=1.41）.（2）Therapeutic studies of Rk1@MHT-PEG nanoprobes were carried out at the cellular and animal levels.The good biosafety of Rk1@MHT-PEG nanoprobe was demonstrated by cytotoxicity analysis and hematological tests,which laid the foundation for the subsequent therapeutic studies.The good SDT effect of MHT nanoprobe was demonstrated by ex vivo ultrasound treatment experiments,and Rk1@MHT-PEG nanoprobe had an enhanced SDT effect with an inhibition rate of model hepatocellular carcinoma of 87.5%.Then,through immunofluorescence and histopathological staining experiments,we demonstrated that the Rk1@MHT-PEG nanoprobe synergistically enhanced the mechanism of SDT in hepatocellular carcinoma through the dual regulatory strategy of exogenous reactive oxygen species production and endogenous glutathione synthesis pathway inhibition under ultrasound excitation.Finally,through in vivo magnetic resonance imaging tests in mice,we demonstrated that the Rk1@MHT-PEG nanoprobe was able to enhance the T₁ MR signal at the tumor site and visualize the SDT treatment.Meanwhile,the nanoprobe provides new ideas for the design of high-performance SDT sonosensitizers due to its good anti-tumor efficiency and the first innovation of using ginsenoside Rk1 for SDT enhancement strategy.