Research On Effects Of Nanoparticles On The Structure And Function Of Artifical Lung Surfactant Films

The monolayers of1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) as well as1,2-Dipalmitoyl-sn-glycerol-3-phosphoglycerol (DPPG), which are the important components of lung surfactant (LS), have been used as the artificial model system representative of pulmonary surfactant in the present study for interacting with the negative charged Ag nanoparticles (naked Ag and citrate modified Ag) which provided with an average diameter of50nm as well as the negative charged naked SiO2nanoparticles with an average diameter of20nm respectively under the physiological condition. Quantification of Phosphatanalysis and film balance measurements provided a systematical analysis for investigating the effect of the nanoparticles mentioned above on the structure and function of the artificial lung surfactant comprise of pure phospholipid.The amount of lipid molecules binding to the nanoparticles was determined by using a procedure based on detecting the absorbance of a blue colored-complex formation of malachite green with phosphomolybdate under acidic conditions at wavelength of610nm. The experimental results showed an obvious stronger adsorption of zwitter ionic DPPC with each negative charged nanoparticles in comparison with that of anionic DPPG under the same conditions.The nanoparticles coated with lipid corona were spread on the surface of a buffered subphase (25mM HEPES,3mM CaCl2, pH7.0,20℃)for determining the surface tension by film balance measurements. The effect of the nanoparticles on the structure and function of the artifical lipid monolayer was investigated from the changes in the phase behavior of the artifical lipid monolayer by the obtained surface pressure-area (π-A) isotherms. The results exhibited that naked Ag nanoparticles have no effects on the structure or function of the artifical DPPC monolayer but have a significant effect on that of the artifical DPPG monolayer. Moreover, an obvious effect of Ag-citrate nanoparticles as well as naked SiO2 nanoparticles on the structure and function of the artifical DPPC monolayer could be observed. Additionally, two different modified Ag nanoparticles surrounded by DPPC corona were spread on the surface of a buffered subphase (25mM HEPES, pH7.0,20℃) in the absence of Ca2+in turn in order to investigate the influence of Ca2+within the subphase on the phase behavior of the artifical DPPC monolayer by comparing with the surface pressure-area (π-A) isotherms obtained in the present of Ca2+. It’s found that the phase behavior of the artifical lipid monolayer changes in a calcium-dependent manner.