Tuning Cell Autophagy By Nanoparticle-protein Corona

Autophagy is an important and conserved lysosomal degradation pathway in eukaryotic cells.It maintains the balance between protein synthesis and degradation,organelle formation and clearance,and plays an essential physiological role.Autophagy is also associated with cancer,neurodegenerative diseases and inflammation.Modulation of autophagy plays a vital role in the treatment of these diseases.Evidence has also shown that autophagy may represent a common cellular response to nanoparticles.The rational design of nanoparticles for cell autophagy modulation is expected to become an effective method to treat autophagy-related diseases.Recently,it's reported that different surface chemically modified nanoparticles are prepared to regulate autophagy,but such chemical modification is complex and has potential biosafety issues.Similarly,the technique of obtaining the short peptide RE-1and its variants that bind to the nanoparticle characteristics through phage display to regulate the level of autophagy is also not easy to grasp.Therefore,there is a need to develop simple,safe protocols to obtain nanoparticles that can regulate autophagy levels.When the nanoparticles are applied to a living body,the surface rapidly binds to biological molecules such as proteins to form nanoparticle-protein complexes namelya"protein corona"structure.These nanoparticle-protein complexes can not only regulate the cellular uptake of nanoparticles,improve biocompatibility,but also serve as regulators of cell signaling pathways and targeted drug carriers,and have great potential for application in the biomedical field.In this work,we found that nanoparticle-protein complexes can induce different levels of autophagy,which is expected to develop into a simple and effective autophagy regulator.To further understand the effect of nanoparticle-protein complexes on autophagy,we systematically analyzed the role of different physicochemical properties in the autophagy-inducing effect of nanoparticle-protein complexes.These physicochemical properties included nanoparticles size,shape and core composition,as well as the different protein species on the nanoparticle surface.The main research content is as follows:?1?It was found that the autophagic inducibility of Fe₃O₄ nanoparticles was weakened due to adsorption of serum proteins.In serum-free cultured cells,Fe₃O₄nanoparticles can cause high levels of autophagy,while in serum culture,Fe₃O₄nanoparticles are coated with serum proteins,and autophagy levels are reduced by 50%.This result suggests that the nanoparticle-protein complex formed after adsorption of the protein can regulate the level of autophagy.?2?Different kinds of protein crowns can regulate the level of autophagy to different degrees.We compared the nanoparticle-protein complexes formed by the interaction of four serum-model proteins?albumin-BSA,transferrin-BTf,immunoglobulin-BIg,and fibrinogen-BFG?with Fe₃O₄ nanoparticles to autophagy.The level of regulation ability,found that the autophagic regulation ability of these complexes is different from strong to weak:BFG>BIg>BTf>BSA.Moreover,the relationship between the autophagic regulatory ability and molecular weight of these proteins was analyzed and a positive correlation was found.The more molecular weight the proteins,the stronger the ability of autophagy regulation.?3?The nanoparticle-protein complex regulates the autophagy level with particle size dependence.The particle size of 5,10 and 20 nm Fe₃O₄ nanoparticles adsorbed serum proteins to form nanoparticle-protein complexes with different particle sizes.It was found that 5 nm,10 nm,and 20 nm nanoparticles-protein complexes downregulate the phagocytic levels by 12%,38%,and 61%respectively,indicating a particle size-dependent effect.The larger the particle size,the stronger the nanoparticle-protein complexes'ability to regulate autophagy.?4?Nanoparticle-protein complexes regulate shape-dependent autophagy.The naked Fe3O4-sphere can induce high levels of cellular autophagy,and Fe₃O₄-sphere nanoparticle-protein complexes that encapsulate serum proteins downregulate the level of autophagy by 63%.However,Fe₃O₄-cube and Fe₃O₄-rod showed completely different autophagic inducing ability.The naked Fe₃O₄-cube and Fe₃O₄--rod induced low levels of autophagy.After the formation of Fe₃O₄-cube and Fe₃O₄-rod nanoparticle-protein complexes,the levels of autophagy increased by 57%and 192%,respectively.This indicates that nanoparticles in different shapes have completely different capabilities regulating the level of autophagy.?5?The nanoparticle-protein complex regulates the level of autophagy with a core component dependency.The autophagic inducibilities of AuNPs and Fe₃O₄nanoparticles with particle diameters of 20 nm were compared.Compared with bare Fe₃O₄ nanoparticles,Fe₃O₄ nanoparticle-protein complexes have reduced autophagic inducibility.In contrast,the autophagy-inducing ability of the bare AuNPs was low,whereas the AuNPs nanoparticle-protein complex showed strong autophagy-inducing ability,which increased the autophagic level by 200%.In summary,in this paper we examined the autophagy induced by nanoparticle-protein complexes with different particle sizes,shapes,core components,and surface-bound protein types.It was demonstrated that these physicochemical properties of the nanoparticle-protein complex have a great influence on the level of autophagy.In addition,the relationship between autophagic levels and the molecular weight of each protein on the nanoparticles is revealed,which will guide the rational design of nanoparticle-protein complexes in autophagy regulation and biomedical applications.