Study On The Effect Of SiO₂ Nanoparticles On Lipid Monolayer Membrane

Silica has been widely used in water treatment,coatings,chromatography,cosmetics,functional materials,biomedicine,catalysis and other fields,since it has low density,no moisture absorption,good optical properties,stable chemical properties,acid and alkali corrosion resistance,high hardness and good biocompatibility.Especially in biomedicine,silica is used as antibacterial agent and medical equipment,such as silicone filler in medical beauty.Due to the large amount of silica used in human life and medical treatment,though silica has good biocompatibility,silica nanoparticles are toxic to human if they are inhaled into the lungs.Organs such as the lungs will be strongly affected.Therefore,in this study,the toxicity of silica nanoparticles to human body will be explored.Lipid monolayer is constructed to mimic cell membrane on the lung surface,and the effect of silica nanoparticles on cell membrane is investigated.LB technology,Atomic force microscope(AFM)and other instruments are used to obtain surface pressure-area,surface pressure-time isotherms,and AFM diagrams.The effect of different silica nanoparticles to lipid monolayer is analyzed by these data.Silica nanoparticles are prepared by microemulsion,meanwhile,APTES and DMDCS are used to modify silica NPs to substitute the hydroxyl groups on the interface of silica NPs as aminopropyl and methyl groups,respectively,and then get three types of modified silica NPs.They are S1(hydrophilic silica nanoparticles with aminopropyl group),S2(amphoteric silica nanoparticles)and S3(hydrophobic silica nanoparticles with methyl groups).US is unmodified silica(directly prepared by microemulsion).The research content is the interaction between silica nanoparticles and lipid membranes.Therefore,after preparing the silica nanoparticles,it is necessary to select suitable lipid molecules to prepare lipid monolayers.1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC)is a common phospholipid in the human body,especially on the alveolar surface.Alveolar surfactants are mainly DPPC and surfactant binding proteins(SP).DPPC are arranged in monolayer on the air-liquid interface of the alveoli.Therefore,this experiment first studies the effect of silica nanoparticles on DPPC monolayers and the interaction between DPPC and silica nanoparticles.The DPPC monolayer was constructed to simulate the lung surface.Experimental results show that the addition of silica nanoparticles changes the phase behavior,collapse time and structure of the monolayer.Hydrophilic silica nanoparticles reduce the stiffihess and collapse pressure of DPPC monolayer,and makes it collapses prematurely.However,the effect of hydrophobic silica nanoparticles on the collapse pressure and stiffness of monolayer is much weaker.It mainly affects the surface morphology of the monolayer.The addition of hydrophobic silica nanoparticles results in the appearance of holes in the surface of the monolayer.The results show that different hydrophilic and hydrophobic silica partieles have different effects on the membrane structure and rheological behavior of DPPC monolayer.Since DPPC is a neutral lipid,the effect of silica nanoparticles on charged lipid DPPG and DOTAP monolayers at the air-liquid interface is investigated after the study of neutral lipids.For DPPG monolayers,the addition of positively charged silica nanoparticles S1 and S3 allows plateau advancing forward and reaching the plateau in advance,and reduces the elasticity of DPPG monolayer.For DOTAP monolayers,the addition of positively charged silica nanoparticles(S1 and S3)reduces the stiffness of the monolayer.Especially for the addition of S3,the stiffness of the monolayer is greatly reduced.From the results of different hydrophilic and hydrophobic silica nanoparticles to different lipid monolayer,it is known that nano-scale silica has a large influence on the lungs,which will change the arrangement and morphology of cells on the surface of the lungs.It can be seen that different silica nanoparticles are toxic to the lungs,but the toxicity is different.Therefore,attention should be paid to the inhalation of silica nanoparticles in daily life,medical and industrial production,and to avoid nano-scale silica firom entering the human body through respiration.