Preparation Of Gold-palladium Nanoheterostructures And Their Application In Tumor Phototherapy

Traditional cancer treatment methods inevitably produce toxic side effects on normal tissues due to poor selectivity.Compared with traditional treatment methods,phototherapy,such as photothermal therapy(PTT)and photodynamic therapy(PDT),has the characteristics of temporal and spatial controllability and non-invasiveness,and has become a current cancer treatment method with great potential.In addition,the synergistic treatment of PTT and PDT can combine the characteristics of the two phototherapy techniques.On the one hand,the local heat generated by PTT promotes the transfer of intracellular photosensitizer(PS),thereby increasing the production of reactive oxygen species(ROS),which can enhance PDT.effect.On the other hand,the PTT effect increases the blood flow in the tumor and strengthens the oxygenation of the tumor.The increase in oxygen content enhances the effect of PDT.In addition,PTT does not rely on oxygen and can kill all cancer cells including hypoxic cells.The two treatment methods can promote each other's curative effect and become a new type of cancer treatment strategy,which has received extensive attention from scientific researchers.Since the absorption of biological tissues is mostly located in the ultraviolet-visible region,it has certain limitations in clinical transformation.The near-infrared light(NIR)has smaller light scattering and lower absorption of biological tissues.Therefore,the construction of NIR-excited combination therapy nano-system with integrated diagnosis and treatment is very important for the clinical application of combination therapy.At present,the synergistic treatment of PTT and PDT is mainly by combining photothermal materials such as precious metal materials and carbon-based materials with PS through physical action or as a carrier,but the absorption of photothermal materials and PS may not overlap,and the nanosystem is complicated.The synthesis process will hinder its application in clinical treatment.Under the excitation of the light source,noble metals can generate ROS while generating heat due to the plasmon effect.On the other hand,precious metal nanoparticles with a heterogeneous structure can promote the generation of highenergy charge carriers under the irradiation of external light,release heat through the electron-phonon relaxation process,and promote the generation of ROS through chemical and energy conversion processes.Therefore,synthetic precious metal nano-heterostructures can achieve efficient combined therapy of PTT and PDT.Therefore,the following researches are carried out in this paper:1.By synthetic palladium(Pd)deposited on the tips of gold nanorods(PTA NRs),whose absorption located in the NIR region.Because PTA NRs have a heterogeneous structure and excellent local surface plasmon resonance(LSPR)effect,they have excellent photothermal and photodynamic properties.In the cell experiment,by co-incubating PTA NRs with human breast cancer cells(MCF-7),the results showed that under 808 nm laser irradiation,PTA NRs caused cancer cells to apoptotic;but without laser irradiation,it had less effect on cancer cells,which proves that PTA NRs not only have excellent therapeutic effects,but also have excellent biocompatibility.Through in vivo experiments on tumorbearing mice,the results show that PTA NRs can inhibit the growth and metastasis of tumor cells,and have no obvious side effects on normal tissues.PTA NRs have great potential in clinical applications in the future due to their excellent photothermal and photodynamic properties.2.By synthesizing Pd deposited on the tips of Au nanobipyramids(PTA NBPs),compared with gold nanorods(Au NRs),Au nanobipyramids(Au NBPs)have stronger local electric field enhancement capabilities,larger optical cross-sections,and narrower line widths,better shape and size uniformity.The performance test of PTA NBPs found that it has excellent photothermal and photodynamic performance under 808 nm laser irradiation.In the cell experiment,the cells are still viable without laser irradiation,which proves that PTA NBPs have excellent biocompatibility.Under the irradiation of 808 nm laser,PTA NBPs can produce obvious photothermal effect in cells,and generate ROS.ROS and photothermal can promote cancer cell apoptosis.The experimental results show that PTA NBPs have better photothermal and photodynamic properties than PTA NRs,so they have a broader application prospect in treatment.