Study On The Interaction Between Fe3O4 Nanoparticles And Mixed Lipid Monolayer Membrane

Pulmonary surfactants play a vital role in the respiratory process.It is mainly composed of phospholipids,cholesterol(Chol)and specific surface-active proteins.Many studies have found that the lack or inactivation of pulmonary surfactants can lead to various diseases such as respiratory distress syndrome.However,natural surfactants are inefficient and costly,and the treatment of diseases remains to be discussed.Nanotechnology has provided new tools for the development of biomedical and other fields.In particular,the Fe3O4 nanoparticles have super-paramagnetic properties,no cytotoxicity,good biocompatibility and low cost,which lays a foundation for targeted drug delivery and other technologies.However,due to the complexity of pulmonary surfactants and the lack of safe and reliable in vivo experimental techniques and methods.It is extremely urgent for us to study the interaction of in vitro simulated nanoparticles or drugs with pulmonary surfactants.Therefore,the interaction of Fe3O4 nanoparticles with binary and ternary mixed lipid monolayers(DPPC,DOPC,POPC and Chol)as the main cytoskeleton of pulmonary surfactant membrane was studied by Langmuir-Blodgett(LB)membrane technology and atomic force microscopy(AFM).1.The effects of different concentrations of hydrophilic and hydrophobic Fe3O4 nanoparticles with binary lipid mixed DPPC/DOPC and ternary lipid mixed DPPC/DOPC/Chol monolayers.The interaction of mixed DPPC/DOPC and DPPC/DOPC/Chol monolayers with hydrophilic and hydrophobic Fe3O4 nanoparticles was studied by surface pressure-area isotherms(?-A)and adsorption curves(?-t),compressibility analysis and thermodynamic stability based on ?-A isotherms,and AFM observation.The results show that both hydrophilic and hydrophobic Fe3O4 nanoparticles have the characteristics of non-surfactant.When enough hydrophobic Fe3O4 nanoparticles were added to the subphase,the surface pressure of the lipid monolayers increased significantly.Hydrophilic and hydrophobic Fe3O4 nanoparticles can penetrate the lipid monolayer,and hydrophobic nanoparticles have much greater influence on the lipid monolayer than hydrophilic nanoparticles.At the same time,hydrophobic Fe3O4 nanoparticles were well distributed at the interface.During the adsorption process,the stability of hydrophilic Fe3O4 nanoparticles is lower than that of hydrophobic Fe3O4 nanoparticles.When Chol was added into the mixed DPPC/DOPC monolayers,the adsorption curve and the ?-A isotherm changed significantly.This is because the rigid molecular structure of Chol affects the phase separation of mixed lipid monolayers.The AFM images show that when a large number of hydrophobic Fe3O4 nanoparticles are added into the subphase,the interface is filled with nanoparticles and a multilayer structure is formed.However,hydrophilic Fe3O4 nanoparticles occupy only part of the interface.2.The effects of hydrophilic and hydrophobic Fe3O4 nanoparticles on pure POPC,DPPC and different molar ratios of mixed DPPC/POPC monolayers.The results show that different content of mixed DPPC/POPC monolayers has a great influence on the structure of monolayers.In particular,the sub-phase contains different properties of Fe3O4 nanoparticles.The ?-A isotherms of pure DPPC and XPOPC=0.25 monolayers have LE-LC coexistence region,but when the proportion of POPC continues to increase,it is found that LE-LC coexistence region disappears in the isotherms of mixed DPPC/POPC monolayers(XPOPC=0.5,0.75).The LE-LC phase of mixed DPPC/POPC monolayers was reduced to 3 mN/m surface pressure by hydrophobic Fe3O4 nanoparticles.When hydrophilic Fe3O4 nanoparticles were added to the sub-phase,the compressibility of mixed DPPC/POPC monolayers increased,while hydrophobic Fe3O4 nanoparticles were the opposite.The effect of hydrophobic Fe3O4 nanoparticles on the adsorption capacity of mixed DPPC/POPC monolayer is greater than that of hydrophilic Fe3O4 nanoparticles on the adsorption capacity of mixed DPPC/POPC monolayer.In order to further explain the interaction between mixed lipid monolayers and Fe3O4 nanoparticles,the surface morphology of the films was studied by using AFM.We observed that the exclusion between hydrophobic Fe3O4 nanoparticles and tail chains of mixed lipid molecules led to the entry of lipid-NPs complex into the subphase.The interaction between hydrophilic Fe3O4 nanoparticles and lipid head enhances the attraction interaction between lipid molecules.At the same time,Fe3O4 nanoparticles can improve the roughness of mixed DPPC/POPC monolayers under low surface pressure.The hydrophobicity of Fe3O4 nanoparticles is stronger than hydrophilicity,but the effect is not obvious at high surface pressure.It is found that the concentration of Fe3O4 nanoparticles affects the distribution at the air-water interface and the different properties have a great influence on the mixed monolayers.The high concentration of Fe3O4 nanoparticles shows a large number of nanoparticles occupying the interface space at the air-water interface;while the hydrophobic Fe3O4 nanoparticles fill the entire interface at high concentration,but hydrophilic Fe3O4 nanoparticles only occupy part of the interface.It was also found that the interaction between hydrophilic Fe3O4 nanoparticles and the head of mixed lipid molecules enhanced the attraction interaction between lipid molecules,while the exclusion between hydrophobic Fe3O4 nanoparticles and tail chains of mixed lipid molecules led to the entry of lipid-nanoparticle complexes into the subphase.These studies provide experimental and theoretical basis for targeted drug delivery or drug therapy and understanding of biofilm structure models.