Preparation Of Two-dimensional Alloy Nanosheets And Their Application Of Tumor Optical Diagnosis And Treatment

Cancer is one of the important public health problems worldwide,and its high morbidity and mortality seriously threaten human life and health.With the continuous development of nanotechnology,nanoscience,life science and medical science have gradually intersected to form nanobiomedicine,which has continuously promoted the diversified development of new strategies for cancer diagnosis and treatment.Two-dimensional inorganic nanomaterials show great potential in optical imaging,drug delivery,photothermal therapy and photodynamic therapy due to their large specific surface area,tunable optical properties and high biocompatibility.In this thesis,based on the excellent optical properties of two-dimensional alloy nanomaterials,a series of high-efficiency optical diagnosis and treatment platforms for tumors have been constructed by taking advantage of their high photothermal conversion efficiency and optical stability.The specific research contents are as following:（1）Two-dimensional platinum-tin-bismuth（PtSnBi）alloy nanosheets were synthesized by one-pot method and modified with polyethylene glycol（PEG）for surface modification to enhance biocompatibility（PtSnBi-PEG）.PtSnBi-PEG has high near-infrared light absorption ability and optical stability,and the photothermal conversion efficiency is as high as 61%.Meanwhile,PtSnBi-PEG has good photoacoustic imaging performance.PtSnBi-PEG showed good biocompatibility and photothermal killing effect at the cellular level,which provided a basis for PtSnBi-PEG to realize photoacoustic imaging-guided photothermal therapy at the in vivo level.（2）The in vivo antitumor application of PtSnBi-PEG was studied.After intratumoral injection of the tumor,photoacoustic imaging of the tumor site could be performed.Under the irradiation of near-infrared light,the local temperature of the tumor area rapidly rose to kill tumor cells and realized in vivo photothermal therapy.Short-term and long-term biosafety experiments showed that PtSnBi-PEG had low toxicity and side effects with potential clinical translation prospects.（3）Platinum-bismuth（PtBi）nanosheets were synthesized by solvothermal method,surface-modified with PEG to enhance biocompatibility and coupled with photosensitizer chlorin e6（Ce6）to obtain PtBi-PEG-Ce6 nanosheets.PtBi-PEG-Ce6has high near-infrared light absorption capacity and photothermal conversion efficiency（46.1%）,and can generate a large amount of singlet oxygen（¹O₂）under the excitation of 660 nm laser.The element Pt in PtBi-PEG-Ce6 has excellent catalase-like activity,which can continuously catalyze the decomposition of excess hydrogen peroxide in tumor tissue to generate oxygen,relieve tumor hypoxia,and improve the effect of photodynamic therapy.The nanosheets achieved high-efficiency photothermal/photodynamic combined killing effect at the cellular level,which provided a research basis for PtBi-PEG-Ce6 for photothermal/photodynamic combined therapy guided by imaging at the in vivo level.（4）The in vivo antitumor application of PtBi-PEG-Ce6 was studied.After tumor-bearing mice injecting with PtBi-PEG-Ce6 through the tail vein,under the combined action of 808 nm laser and 660 nm laser,the temperature of the tumor area was slightly increased,which could increase the catalase-like activity of Pt and relieve tumor hypoxia to improve the effect of photodynamic therapy.Photothermal/photodynamic combined therapy thereby was realized.Biosafety evaluation experiments showed that PtBi-PEG-Ce6 had less side effects and was a potential multifunctional clinical diagnosis and treatment platform.