Cell Autophagy Induced By Modified Gold Nanoparticles (a Preliminary Study)

Nanotechnology has rapid development and exploitation in a wide spectrum of fields, including information technology, energy production, environmental protection, biomedical applications, food, agriculture and many more, since the late 1960s Nobel laureate Richard Feynman first proposed the concept of nano science and technology. With the extensive application of nanotechnology, nanomaterials enter the ecological environment in various ways and means and cause potential ecological and human health risks.It is reported that the entire process of production, transport and use of nanoparticles can cause its release and diffusion in the environment. Nanoparticles be exposed by breathing, skin exposure, oral exposure and exposure to other ways may enter into various organs in the body through lymphatic circulation and blood circulation, causing the body’s stress response.With the deepening study of ecological effects of nanomaterials, it is in urgent need to learn how the properties of nano materials affect their biological effects, so as to provide theoretical support for scientific, safe use of nanomaterials. Current research indicates that components of nanomaterials, particle size, morphology, surface properties, etc. can affect the biological effects of nanomaterials. Electrostatic interactions, hydrophobic interactions, hydrogen bonding interactions, π-π conjugation, steric hindrance, etc. play a key role in terms of the biological effects of nanomaterials. In order to systematically elucidate how the surface properties of nanomaterials affect the biological effect, we designed and synthesized five univariant gold nano series with continous changed properties (hydrophilicity, charge, hydrogen bonding, π-bond and steric hindrance) by surface modification of gold nano material which is widely used in the diagnosis, treatment, carrying medicine and other fields.At the first part of this work we synthesized a library of gold nanoparticles (GNPs) with surface π-bond density continuous changed. We connected our ligands (5-(1,2-dithiolan-3-y l)-N-phenylpentanamide and N-cyclohexyl-5-(1,2-dithiolan-3-yl) pentanamide) with GNPs by Au-S covalent bond, and changed the ratio of the two ligands to get GNPs with continuous changed property. The series of gold nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Zeta potentials, etc. The results showed that the six GNPs are spherical particles with diameter between 5 to 7 nm. Their octanol-water partition coefficients (LogP) are positive, meaning that all the six gold nanoparticles are hydrophobic. The results of DLS and Zeta potential indicate that the six GNPs are in the stable state of aggregation in solution.At the second part, we studied the ability of the five series of GNPs to induce autophagy in human glioma cell lines U87 transfected with GFP-LC3. The results showed that the hydrophilic/hydrophobic continuously changing series of GNPs and surface charge continuously changing series can cause significant upregulation of the level of autophagy, and with enhanced hydrophobicity and surface charge density increases the level of cell autophagy. The ability of the other three series of GNPs to induce autophagy is weak, and do not show clear trend. The results of this work provide a theoretical basis for the rational and safe use of gold nano material.