Interaction Of Zn²⁺ Doped Fe₃O₄ Nanoparticles With Pepsin

In recent decades,the nanomaterials have gained rapid development and a larger scale use in numerous areas such as industry,commerce and biomedicine.The huge application prospects and the extensive production of nanomaterials in the industry have greatly increased the probability of their exposure to human.Under the circumstances,the biological effects of nanomaterials have attracted a lot of attention and interest from researchers.It's generally considered that when nanomaterials exposed to biological fluids,the adsorption and interactions with protein will lead the formation of "protein corona" on the surface of particles.In the view from nanomaterials,the formation of "protein corona" has a further impact on various biological activities such as metabolic pathway,cellular uptake and body elimination of nanomaterials,and ultimately determining their distribution and function in vivo.In the view from protein molecules,the "protein corona" will modify the structure,bioactivity and function of original proteins,which determine the biological toxicity of nanomaterials.Therefore,to study the interactions of nanomaterials and protein is vital important for the further application in biotechnology and bioscience of nanomaterials.The magnetic nanomaterials have been widely used in biomedicine because of their higher magnetic susceptibility and better biocompatibility.Currently,Super-paramagnetic ferroferric oxide nanoparticles are the only magnetic nanomaterials approved for clinical use by the US Food and Drug Administration.Zn²⁺ doped ferroferric oxide nanoparticles(Zn_xFe_3-xO₄ NPs)have higher magnetic susceptibility than ferroferric oxide nanoparticles,which makes them more suitable for medical therapies as magnetic resonance imaging contrast agents.However,it's necessary to figure out the interactions between Zn_xFe_3-xO₄ NPs and proteins and biosafety problems caused by their interactions before their application.In this work,Zn_0.4Fe_2.6O₄ NPs were used to explore their interaction with proteins in vitro and in vivo.The whole thesis is divided into three chapters.Chapter 1:Firstly,we briefly reviewed the mechanism of interaction between nanomaterials and proteins.Secondly,we analyzed the factors influencing adsorption behavior in three directions:nanoparticles,protein and medium.Then,we summarized the effects of adsorption on the properties of nanoparticles and proteins on the base of existing work.Finally,we introduced many methods to study the interaction between nanoparticles and proteins.Chapter 2:The Zn_0.4Fe_2.6O₄ NPs were synthesized using hydrothermal method.TEM,XRD and DLS were used to characterize the particles.After intragastric administration of Zn_0.4Fe_2.6O₄ NPs,the protein corona formed on the surface of particles in the mouse stomach was studied.The results showed that protein corona contained the proteins from stomach,such as pepsinogen,gastric lipase,gastric intrinsic factors,etc.,and proteins produced in the pancreas,such as pancreatic amylase and elastase.For in vitro tests,we studied the interaction between Zn_0.4Fe_2.6O₄ NPs and pepsin.The adsorption equilibrium of pepsin on Zn_0.4Fe_2.6O₄ NPs was achieved quickly and the adsorption behavior was fitted best with Langmuir model.The maximum adsorption capacity was reached near the isoelectric point of pepsin and increase of solution ionic strength would inhibit the adsorption of pepsin on Zn_0.4Fe_2.6O₄ NPs.In addition,obvious agglomeration was observed both in vivo and in vitro adsorption of proteins.Chapter 3:The effects of adsorption on the structure and activity of pepsin were studied after interactions of Zn_0.4Fe_2.6O₄ NPs with pepsin.The results showed that the secondary structure of pepsin changed and the enzyme activity significantly reduced after adsorption.In addition,the adsorption of pepsin on Zn_0.4Fe_2.6O₄ NPs resulted in the hydrolysis of pepsin.