Research On The Molecular Mechanism Of Nanoscale Biological Effects

The potential applications of nanomaterials in biomedicine and environment have made the biological effects and biosafety evalutions of nanomaterials be widely concerned,the biological effects of which depend on many factors,including the dynamic physical and chemical interactions between nanomaterials and the surface of biological components.Therefore,a thorough and systematic study of the interaction mechanism between nanomaterials and biological systems is the key to controlling the biological effects of nanmaterials and promoting the development of nanomaterials.In this dissertation,with nanomaterials and its degradable components as well as biological components,including proteins,biomembrane and cells,we explored the molecular mechanism and nature of nano-bio interface interactions by changing analysis techniques and methods,such as surface enhanced infrared absorption spectroscopy and fluorescnece technology,which can provide theoretical guidance for the evaluation of the nano-bio effects and the safety as well as the design of nanomaterials for various medical applications.The main points are outlined as follows:1.The biological effects of nanomaterials depend on the interaction between nanomaterials and proteins.With SiO2 nanoparticles(SiO2 NPs)and cytochrome c(cyt c)on the bio interface as a nanobio model,we probed the influence of SiO2 NPs on the structure and function of cyt c by combining surface enhanced infrared absorption spectroscopy and electrochemistry.Our results found that SiO2 NPs slightly induced the structural changes of the ?-sheet in the oxidized form and the change of microenvironment surrounding them,which could further change the orientation and microenvironment of heme and its surrounding environment,facilitating the hydration of cyt c at the oxidized state.It could be the enhanced hydration of cyt c(Fe3+)and a smaller change in the total hydration from reduced to oxidized state that resulted in the slight negative shift in the formed potential and promoted the electron transfer capability.In addition,cyt c's slight conformational change and the disturbance to the microenvironment of heme resulting from the adsorption of SiO2 NPs could also be one of reasons that led to the enhanced catalytic capability towards the reduction of hydrogen peroxide.2.The biological effects of nanomaterials also rely on the interation between nanomaterials and biomembrane.With graphene oxide(GO)and a lipid membrane as a nanobio model,and modulating interaction forces at the GO-biomembrane interface by varying the amounts and species of oxygenated functional groups on the surface of GO,we revealed how weak forces interacted synergistically to induce the extractive effects of GO on the biomembrane with surface enhanced infrared absorption spectroscopy and confocal laser scanning microscopy.Our results showed that after balancing with electrostatic repulsion,the moderate attraction between GO and lipid headgroups(such as electrostatic and/or hydrophobic interactions)was most favorable for lipid extraction,whereas lipid extraction was inhibited under an attraction that was too strong or too weak.Under moderate attraction between GO and the headgroups of lipids,the appropriate degree of rotation freedom was maintained for GO,which was beneficial to the hydrogen-bonding interaction between the C=O group in the phosphatide hydrophobic region and GO,thus triggering the insertion of GO into the lipid alkyl chain region,resulting in the rapid and significant extraction of lipids.Our results have important guiding significance for how to reveal the synergistic mechanism of weak interactions at the nanobio interface.3.On the basis of the results of last section,we investigated the effect of the phase behavior of the lipid membrane on the interaction between GO and the lipid membrane.We found that the extractive effect of GO on lipid membrane had significant phase selectivity,and it selectively extracted the lipid molecules of the fluid phase,which was affected by the ratio of the lipids in the gel phase.The extraction of lipids in the fluid could only occur when the lipids of the fluid phase accounted for most of the lipids in the lipid membrane.4.The biological effects of nanomaterials involve a series of intracellular reactions triggered by the degradation of nanmaterials.For instance,the iron ions released by the degradation of iron-containing nanomaterials can participate in lipid peroxidation reactions to produce reactive oxygen species and lead to ferroptosis.We focused on the molecular mechanism of iron-dependent lipid peroxidation in ferroptosis using surface enhanced infrared absorption spectroscopy and fluorescence technology.We found that lipid peroxy free radicals from lipid peroxidation initiated by hydroxyl radicals could directly generated small amount of singlet oxygen through the Russell mechanism.More importantly,the interaction of lipid peroxy radicals with lipids could cause the accumulation of more lipid peroxy radicals and lipid hydroperoxides,which could generated a lot of singlet oxygen under the catalysis of iron ions.Singlet oxygen could promote the loss of membrane integrity and ferroptosis of cells.In addition,this is the first report about the production and influence of singlet oxygen in the ferroptosis.