Joint Effect Of Nanocomposite On The Pulmonary Surfactant Layer Revealed By Molecular Dynamics Simulations

With the development of modern science and technology,people have reached an unprecedented level of understanding and transformation of the microcosm.In this context,nanotechnology has developed rapidly.Various nanomaterials are widely used in daily life,causing a large number of nanoparticles to be discharged into the environment,increasing the exposure risk of human beings exposed to nanoparticles.At the same time,the pollutants in the complex atmospheric environment have diverse types,which can easily form nanocomposite particles and cause multiple compound toxicity.This seriously threatens the ecological environment and human physiological health,but the mechanism is not clear.When people breathe normally,nanoparticles can enter the lungs through the respiratory tract to deposit,and first interact with the pulmonary surfactant at the air-liquid interface of the alveoli.On the one hand,by disturbing the structure,properties and functions of lung surfactants,destroying its inherent biological characteristics,on the other hand,it also has an impact on the fate and fate of the nanoparticles themselves.Nowadays,molecular simulation has become an important research method in the field of studying environmental Nano biological effects.In this paper,molecular dynamics simulation methods are used to study the interaction between inhalable nanoparticles and lung surfactants.The main research contents are summarized as follows:(1)Interaction between PAHs nanoparticles and pulmonary surfactantsAs a typical volatile organic pollutant,PAHs have been proved to be harmful to human health through respiration,skin contact and other ways.A large number of PAHs are produced in daily life and production.Some of them will form aggregated particles of different sizes after a long time of thermal movement.It then enters the lungs through the respiratory tract through human respiration and interacts with the lung surfactant at the alveolar gas-liquid interface.We simulated the thermal movement of different amounts of PAHs in the gas phase and extracted the PAHs aggregated particles of different sizes that had been formed stably.We studied the interaction of PAHs nanoparticles with pulmonary surfactants.The results showed that PAHs particles were easily dissolved by pulmonary surfactants,which increased the bioavailability.PAHs particles disturb the structure of pulmonary surfactants and eventually tend to be deposited on the pulmonary surfactants in a vertical insertion pattern.Our simulations suggest that the interaction with phospholipid molecules at the gas-liquid interface should be considered in assessing pulmonary inhalation toxicity of PAHs.(2)Interaction of nanoparticles and PAHs nanocomposites with pulmonary surfactantsNano-level fine particles,mainly based on carbon materials,have extremely high surface energy,which makes the nanoparticles easily absorb other small molecule pollutants in the atmospheric environment,and then form complex and changeable composite pollutants.The biological effects of nanomaterials entering the lungs as inhalable particles are more complex,resulting in multiple toxicity.Based on the above background,the interaction system of nanocomposites with lung surfactants was designed to investigate the gaseous adsorption of PAHs on graphene and GO nanosheets and their interactions with lung surfactants at the alveolar gas-liquid interface.On the one hand,the specific process and steady state configuration of the recombination between nanoparticles and PAHs in gas environment were explored.On the other hand,the interaction between different physical and chemical properties of nanocomposites and pulmonary surfactants was investigated.The results showed that when PAHs were adsorbed on graphene,the solubility of PAHs was inhibited by pulmonary surfactant,which indicated that the interaction among graphene,pulmonary surfactant and PAHs was competitive.Similar results were seen in simulations of GO systems,where deposition of graphene and GO combined with local accumulation of high concentrations of PAHs exacerbated the disturbance of pulmonary surfactants.At the same time,the degree of disturbance to the ultrastructure of the lung surfactant also depends on the oxidation of graphene,the configuration of the complex,and the adsorption capacity of PAHs.Our results suggest that inhalation toxicity of nanocomposites should be studied by considering the gaseous combination of nanoparticles with PAHs and the toxic effects of the complex on pulmonary surfactants.(3)Interaction of suspended nanoparticles and PAHs nanocomposites with pulmonary surfactantsSuspended contact is one of the actual contact modes between nanocomposites and pulmonary surfactants.The inhalation toxicity caused by the contact between different compounds and pulmonary surfactants is also different.We designed a system of suspended nanocomposites interacting with pulmonary surfactants.The simulation results show that,in addition to graphene oxidation and PAHs adsorption differences,the suspension state and tilt degree of the nanocomposites significantly affect the extraction of phospholipid molecules,causing varying degrees of disturbance and damage to the ultrastructure of pulmonary surfactants.The results show that in the graphene composite system with low adsorption capacity,the amount of phospholipid molecules is large,which easily leads to the breakdown of phospholipid layer.In the system with high adsorption capacity of Benzo[a]pyrene,the dissolved amount of Benzo[a]pyrene is large,the molecular removal amount of phospholipid is small,and the disturbance to phospholipid layer structure is small.For GO systems,no matter how much Benzo[a]pyrene is adsorbed,the amount of phospholipid molecules is sufficient to cause hole damage in phospholipid formation.Therefore,the significant influence of suspension exposure mode should be considered in assessing inhalation toxicity of compounds.