title: Influence of nanoparticle-membrane electrostatic interactions on membrane fluidity and bending elasticity.
abstract: The aim of this work is to investigate the effect of electrostatic interactions between the nanoparticles and the membrane lipids on altering the physical properties of the liposomal membrane such as fluidity and bending elasticity. For this purpose, we have used nanoparticles and lipids with different surface charges. Positively charged iron oxide (γ-Fe2O3) nanoparticles, neutral and negatively charged cobalt ferrite (CoFe2O4) nanoparticles were encapsulated in neutral lipid 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine lipid mixture. Membrane fluidity was assessed through the anisotropy measurements using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Though the interaction of both the types of nanoparticles reduced the membrane fluidity, the results were more pronounced in the negatively charged liposomes encapsulated with positively charged iron oxide nanoparticles due to strong electrostatic attractions. X-ray photoelectron spectroscopy results also confirmed the presence of significant quantity of positively charged iron oxide nanoparticles in negatively charged liposomes. Through thermally induced shape fluctuation measurements of the giant liposomes, a considerable reduction in the bending elasticity modulus was observed for cobalt ferrite nanoparticles. The experimental results were supported by the simulation studies using modified Langevin-Poisson-Boltzmann model.
authors.affiliation: Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia.
authors.forename: Poornima Budime
authors.initials: PB
authors.lastname: Santhosh
authors.affiliation: Laboratory of Biocybernetics, Faculty of Electrical Engineering, University of Ljubljana, Tržaska 25, SI-1000 Ljubljana, Slovenia; SMARTEH Research and Development of Electronic Controlling and Regulating Systems, Trg Tigrovcev 1, SI-5220 Tolmin, Slovenia.
authors.forename: Aljaž
authors.initials: A
authors.lastname: Velikonja
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaska 25, SI-1000 Ljubljana, Slovenia; Institute of Cell Biology, Faculty of Medicine, University of Ljubljana, Lipičeva 2, SI-1000 Ljubljana, Slovenia.
authors.forename: Šarka
authors.initials: Š
authors.lastname: Perutkova
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaska 25, SI-1000 Ljubljana, Slovenia.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Gongadze
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaska 25, SI-1000 Ljubljana, Slovenia.
authors.forename: Mukta
authors.initials: M
authors.lastname: Kulkarni
authors.affiliation: Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
authors.forename: Julia
authors.initials: J
authors.lastname: Genova
authors.affiliation: Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Eleršič
authors.affiliation: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaska 25, SI-1000 Ljubljana, Slovenia.
authors.forename: Aleš
authors.initials: A
authors.lastname: Iglič
authors.affiliation: Laboratory of Clinical Biophysics, Faculty of Health Sciences, University of Ljubljana, Vrazov trg 2, SI-1000 Ljubljana, Slovenia.
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglič
authors.affiliation: Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia; Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CipKeBiP), Jamova 39, SI-1000 Ljubljana, Slovenia. Electronic address: natasa.poklar@bf.uni-lj.si.
authors.forename: Nataša Poklar
authors.initials: NP
authors.lastname: Ulrih
mesh_terms: D004161:Diphenylhexatriene / Q000737:chemistry; D004548:Elasticity; D005290:Ferric Compounds / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008560:Membrane Fluidity; D010713:Phosphatidylcholines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D055672:Static Electricity
chemical_list: D005290:Ferric Compounds; D008051:Lipid Bilayers; D008081:Liposomes; D058185:Magnetite Nanoparticles; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D004161:Diphenylhexatriene; C000499:ferric oxide; C050294:1-palmitoyl-2-oleoylglycero-3-phosphoserine; C027891:1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine
keywords: Bending elasticity; Liposomes; Membrane electrostatics; Membrane fluidity; Nanoparticles