Tuning The Autophagic Effect Of Ni-Co Nanomaterial And Nano Gene Vector In Tumor Diagnosis And Therapy

As the most promising material in the21st century and the "leader" of material science, nanomaterials show great potential in the field of industry, agricultural and biomedicine, due to their notable advantages of light, electricity, heat, force and magnetism, comparing with macroscopic material and atom. With the development of nanotechnology and biomedicine, outstanding achievements of applying nanomaterials for diagnostic imaging, tumor targeted drug and gene delivery, tumor cell killing make them become the powerful weapon for fighting against tumor.Autophagy, a highly conserved and precisely regulated biological phenomena that existing general in eukaryotic cells, is a process for cell to degrade destructive organelles and long-lived proteins. It is also functioned as a power cycle system for cell renewing and energy balancing. Therefore, autophagy plays vital role in waste removal, self-protection, structure restitution, growth and development. More and more researches demonstrat that autophagy induction may present a common response of eukaryotic cells upon exposure to nanomaterials. However, autophagy elicited by nanomaterials is actually a "double edged sword". When nanomaterials were employed for diagnostic imaging, the elicited autophagy may stand for a potential safety concern for the in vivo bio-application of nanomaterials and oftentimes should be avoided. But for certain therapeutic applications, such as cancer therapy, the capacity to induce pro-death autophagy becomes a desirable feature and may be purposely exploited dramatically. Therefore, modulating the autophagic effect induced by nanomaterials properly and rationally, becomes a fascinating approach in tumor diagnosis and therapy. In this dissertation, we investigate the autophagic effect induced by several kinds of nanomaterials and try to regulate the autophagic extent through various methods in order to facilitate the further application of nanomaterials in tumor diagnosis and therapy.In part I, a series of Ni-Co alloy NC assemblies, composed of nanoparticles (NPs) with a size of about30nm, can be quickly synthesized under microwave irradiation in aqueous solution. The saturation magnetization (Ms) shows a ’roller coaster’effect with varying component molar ratio, while the autophagy-inducing activity and toxicity of these alloy NCs presents an elevated tendency with the increase of nickel component. The autophagic response partly contributes to the observed cellular toxicity of the NC assemblies, as inhibition of autophagy partially but significantly reduces toxicity. Therefore, through tuning the composition of the Ni-Co alloy, we can modulate the magnetism and autophagic effect of the alloy properly in order to satisfying the needs of different applications such as diagnostic imaging (maximum magnetization and low autophagic response) or magnetically-directed cancer cell killing (maximum autophagic response and sufficient magnetization).In part Ⅱ, three non-viral vectors (DMRIE-C, Superfect and Lipofectamine2000) are investigated systematically for their induction of autophagy and the relation between transfection efficiency and autophagic extent. Our results reveal that the three non-viral nano gene vectors can all induce authentic autophagy by enhancing autophagosome formation. Furthermore, a basic positive correlation between transfection and autophagy is presented herein, as transfection efficiency can be restrained by inhibiting of autophagy. Autophagic extent can also be down-regulated by inhibiting endocytosis together with transfection. Our researches indicate that autophagy probably represents a universal cellular response upon non-viral nano gene vectors, and transfection efficiency can be regulated by modulating the level of autophagy in some extent, which may ultimately facilitate the application of transfection in clinical and biomedical research.