The Mechanism Research On Cancer Cell Death Caused By Gold Nanorods

Previous studies of this subject found that our well-designed gold nanorods can specifically target and kill cancer cells, but has a little effect on normal cells. There is few researches on the mechanism of this specific phenomenon currently. For this view, the goal of this project is to analyze, confirm and clarify the mechanisms behind that gold nanorods can specifically kill cancer cells.First of all, we commence the research of nanoparticles interacting with cells in this paper.Accordingto the endocytosed particle’s size, the endocytosis include phagocytosis, macrophages, clathrin-mediated endocytosis, caveolin-mediated endocytosis, and related proteins mediated ion channel. On this basis, we have further synthesized gold nanorod whose size was about 30-60 nm, then after purification and incubation by bovine serum(FCS / FBS),those particle size is still less than 100 nm. Related studies have confirmed that particles of 50-100 nm mainly get into the cell via clathrin-mediated endocytosis way, and part of them by caveolin-mediated endocytosis. Secondly, we focuses on the research of delivery process of endocytic vesicles in cells. The FBS packaged gold nanorods pass into the cell to form early endosomes and further develop into late endosomes. Part of late endosomes fuse with the primary lysosome and eventually develop into secondary lysosomes(mature lysosomes), another part of the late endosomes fuse with autophagosome to form autophagy-endosomes(Amphisome), which then fuse with the lysosome to formate autophagic-lysosome. Finally, we comprehensively confirmed the relationship between gold nanorods and lysosomes by the flow apoptosis detection, laser confocal and western blot technology. By the lysosomal hydrolases monomers, various types of FBS protein molecules on the surface of the gold nano-rods have been hydrolyzed into small molecules(e.g., amino acids, a single phospholipid molecule, monosaccharides, etc.) to provide raw materials for intracellular synthesis. But the gold nanorods can not be degraded, and interacted with lysosome membrane, so, gold nanorod has an effect on lysosomal permeability, which is especially obvious in cancer cells. Compared with the normal cells, the cancer cells’ lysosome membrane is more fragile to dissolve. This specific difference is mainly due to the huge difference of lysosomal membrane components between the cancer cells and the normal cells; at a lower permeability, lysosome can induce activation of apoptotic pathways; at a high degree of numerous breakage, lysosome facilitates cell enters necrosis pathway rapidly; the main reason is that the lysosomal proteolytic enzymes respectively activate the apoptosis and necrosispathway.On this basis, we choose the preliminary experimental cells - MCF-7 cells and further study the mechanism of gold nanorods interacting with the cancer cells. After research and analysis, we found that MCF-7 cells showed necrosis on early stage and manifested apoptosis on late stage at the process of gold nanorods interacting with MCF-7 cells. This is because, after lysosomal destruction, the Cathepsin proteases act on the sk-1, then sk-1 interacts with tumor necrosis factor TNF, then the RIP1-RIP3 complex forms and activates the necrotic process. At this point, NF-κB pathway proceeds self-repair and self-help, and along with the increased expression of Caspase8, the RIP1 is cleaved, which further inhibits tumor necrosis and diverts them to the apoptotic program; the related apoptotic pathway also includes: Caspase8 apoptotic pathway(Caspase8 activate Caspase3), Caspase9 mitochondrial apoptosis pathway(Caspase9 activate Caspase3) and gold nanorods induced autophagy and autophagosomes accumulation, which in turn generated signals of cellular senescence and apoptosis. However, the generation of these signals is attributed to the permeability of the lysosomal membrane under the effect of the gold nanorod.This series of studies provide a theoretical basis and experimental evidence on the subject of nanoparticles for cancer treatment, and these have an important clinical significance.