Interfacial Chemical Interactions Between Fine Particulate Matter And Pulmonary Surfactant

As one of the important components of air pollutants,atmospheric particulate matter has been the focus of global attention due to its adverse environmental and health effects.Previous studies based on epidemiological survey reported that long-term exposure to atmospheric particulate matter can induce the lung cancer and cardiovascular diseases.Atmospheric pollution with particulate matter is considered as an important environmental problem in China,for this reason,particulate matter,VOCs,SO₂,and NO_x have been listed as four types of controlled atmospheric pollutants.The respiratory system is one of the main ways of atmospheric particulate matter exposure,lung as internal organs in direct contact with the atmospheric environment,is the target organ by particles directly harm.Once into the alveolar region,inhaled PM_2.5.5 must first come into contact with pulmonary surfactant?PS?distirbuted in the alveolar lining.In addition,PM_2.5.5 may be considered as a carrier of volatile organic compounds?VOCs?,polycyclic aromatic hydrocarbons?PAHs?and heavy metals in atmospheric environment.When PM_2.5 comes into contact with PS,the interaction between them may impact the aggregation state of PM_2.5,solubilization of organic compounds adsorbed on PM_2.5,and the dissolution of soluble metal components,which may influence the bioavailability of these toxic compounds and induce the pulmonary disease.In this paper,the natural PS?extracted from pig's lungs?was used as PS model,and nanoparticles were selected as representative of atmospheric fine particles.The adsorption of active components in PS by nanoparticles exposure and the effects of interfacial activity?e.g.,surface tension,compression isotherm and foaming properties?were studied.Volatile organic compounds?i.e.,benzene series?and PAHs?i.e.,pyrene,phenanthrene and acenaphthene?were used as the representatives of organic components carried by PM_2.5.The effects of benzene series exposure on PS interfacial activity and membrane structure,and the solubilization effects of PS components on benzene series and PAHs were also investigated.In addition,the changes of interficial chemical properties of PS in the presence of fine soot particles were further examined,and the effects of PS components on the bioavailability of heavy metals in fine soot particles were also also quantitatively evaluated.The main achievements are as follows:?1?PS was successfully extracted from porcine lungs by gradient centrifugation and organic solvent extraction with a self-made alveolar lavage fluid extraction device combined with ultrasound–assisted method.The results showed that ultrasound-assisted extraction was beneficial to the release and extraction of PS from lungs.There were six phospholipid components?89.89%?and two hydrophobic surfactant proteins?1.02%?in PS.The types and contents of the active components were consistent with those reported in the literature.Surface activity test showed that the critical micelle concentration of PS was about 20 mg/L at 37°C.PS could adsorb and diffuse rapidly on the air–liquid interface at room temperature,and the surface tension could reach 0 mN/m.It can be seen that the active components of extracted PS are complete and can be used as PS for subsequent experiments.?2?The main active components?phospholipids and proteins?of PS were adsorbed by nanoparticles,and the order of phospholipids adsorption was SiO₂>SiC>C>ZnO>Fe₃O₄>CeO₂.The adsorption rate of SiO₂ to phospholipids was as high as 88.9%.The absorption ability of nanoparticles to protein components was Fe₃O₄>ZnO>SiC>C>SiO₂>CeO₂.The sorption rate of Fe₃O₄ to protein components could reach 81.2%.The presence of nanoparticles increases the surface tension of PS solutions,and the degree of surface tension enhancement of PS is positively correlated with the adsorption capacity of nanoparticles to phospholipid components.The agglomeration of nano–carbon powder after PS adsorption aggravated,resulting in the decrease of the film forming component?PS?at the interface,the?–A isotherm shrinks,while SiO₂ can enter the molecular gap of the interfacial film and lead to the expansion of the?–A isotherm.Foaming experiments show that protein component plays critical role in the foaming ability of PS.Foaming ability of PS were obviously altered in the presence of NCPs,while the influence of SiO₂ on PS foaming ability increases first and then decreases.?3?Here,simulated PS extracted from porcine lungs was used to study the interaction with BTEX?i.e.,benzene,toluene,ethylbenzene,and p–xylene?as representatives of VOCs.Surface pressure–area??–A?isotherms showed that in the presence of individual BTEX,PS monolayer's phase conversion from gas to liquid expanded phase was dramatically influenced and its collapse pressure decreased greatly compared to those of PS alone,which was attributed to the alteration of PS monolayer's microstructure characterized by atomic force microscopy and Brewster angle microscopy.Solubilization experiments manifested that PS and its major components?dipalmitoyl phosphatidylcholine,DPPC;bovine serum albumin,BSA?exhibited obvious solubilization effects on individual BTEX.The solubilization capacity followed an order:PS>DPPC>BSA,which was positively correlated with hydrophobicity of individual BTEX.Synergistic solubilization test unveiled that the mixed phospholipid components were largely responsible for the solubilization capacity of PS.These findings indicate that VOCs exposure may induce potential pulmonary health risk due to the alteration of gas-liquid interfacial properties of PS.?4?PS and its major components?DPPC and BSA?exhibited great enhancing effect on PAHs solubility,which follows the order:PS>DPPC>BSA,and it was positively correlated with the hydrophobicity of PAHs.Further experiments demonstrated that mixed phospholipids of PS were largely responsible for the solubilization of PS on PAHs.In the presence of PS,DPPC or BSA,adsorption of PAHs by silica was notably inhibited,indicating competitive adsorption between PAHs and PS components on silica.These findings provide evidence for the surface chemistry by which PS facilitates the solubilization of PAHs and reducing the adsorption of PAHs on silica,which may be helpful for deeply understanding the effects of particulate matter and PAHs on lung health.?5?Exposure of soot particles can lead to the phase transition of gas/liquid phase and the change of collapse zone of the?–A isotherm of PS.BAM characterization also confirmed that soot particles in subphase solution would adsorb at the gas–liquid interface,which was the reason for the increasing foaming performance of PS solutions.Only Zn,As and Cd were detected in simulated lung fluid?SLF?.The solubility of Zn,As and Cd in SLF could be improved by the presence of PS,DPPC and BSA components.The order of solubility enhancement was BSA>PS>DPPC.DLS analysis showed that the hydrodynamic diameter of soot particles in four solutions was in the order of saline>DPPC>PS>BSA,which was negatively correlated with BSA contents in solutions.