title: Anionic and Cationic Silver Nanoparticle Binding Restructures Net-Anionic PC/PG Monolayers with Saturated or Unsaturated Lipids.
abstract: We have examined the interactions between polymer-coated anionic (Ag-COOH) and cationic (Ag-NH) silver nanoparticles, and net-anionic lipid monolayers using dynamic surface pressure measurements. Monolayers composed of saturated or monounsaturated mixtures of anionic phosphatidylglycerol (PG) and zwitterionic phosphatidylcholine (PC) lipids (3:1 molar ratio) were used to determine how lipid packing and monolayer phase state influence the extent of nanoparticle binding and the monolayer response. Anionic Ag-COOH inserted into saturated dipalmitoyl-PC/PG (DPPC/DPPG) and dioleoyl-PC/PG (DOPC/DOPG) monolayers at a low initial surface pressure (10 mN m-1) and caused lipid condensation at high initial surface pressures (20 and 30 mN m-1). Hydrophobic interactions were responsible for insertion, while electrostatic and charge-dipole interactions with PCs were responsible for condensation. In contrast, cationic Ag-NH inserted only into saturated DPPC/DPPG monolayers and otherwise led to lipid condensation. For Ag-NH, adsorption was driven primarily by electrostatic interactions with PGs. Analysis of the subphase Ag and phosphorus concentrations confirmed that Ag-NH had a higher degree binding compared to Ag-COOH, and that the monolayer response was not due to lipid extraction.
authors.affiliation: Department of Chemical Engineering, University of Rhode Island , 16 Greenhouse Road, Kingston, Rhode Island 02881, United States.
authors.forename: G D
authors.initials: GD
authors.lastname: Bothun
authors.affiliation: Department of Chemical Engineering, University of Rhode Island , 16 Greenhouse Road, Kingston, Rhode Island 02881, United States.
authors.forename: N
authors.initials: N
authors.lastname: Ganji
authors.affiliation: Department of Chemical Engineering, University of Rhode Island , 16 Greenhouse Road, Kingston, Rhode Island 02881, United States.
authors.forename: I A
authors.initials: IA
authors.lastname: Khan
authors.affiliation: Department of Chemical Engineering, University of Rhode Island , 16 Greenhouse Road, Kingston, Rhode Island 02881, United States.
authors.forename: A
authors.initials: A
authors.lastname: Xi
authors.affiliation: Department of Chemical Engineering, University of Rhode Island , 16 Greenhouse Road, Kingston, Rhode Island 02881, United States.
authors.forename: C
authors.initials: C
authors.lastname: Bobba