Supported Lipid Bilayer NanoSystems: Stabilization by Undulatory-Protrusion Forces and Destabilization by Lipid Bridging

Abstract

Control of the stabilization/destabilization of supported lipid bilayers (SLBs) on nanoparticles is important for promotion of their organized assembly and for their use as delivery vehicles. At the same time, understanding the mechanism of these processes can yield insight into nanoparticle-cell interactions and nanoparticle toxicity. In this study, the suspension/precipitation process of zwitterionic lipid/SiO(2) nanosystems was analyzed as a function of ionic strength and as a function of the ratio of lipid/SiO(2) surface areas, at pH = 7.6. Salt is necessary to induce supported lipid bilayer (SLB) formation for zwitterionic lipids on silica (SiO(2)) (Seantier, B.; Kasemo, B., Influence of Mono- and Divalent Ions on the Formation of Supported Phospholipid Bilayers via Vesicle Adsorption. Langmuir 2009, 25 (10), 5767-5772). However, for zwitterionic SLBs on SiO(2) nanoparticles, addition of salt can cause precipitation of the SLBs, due to electrostatic shielding by both the lipid and the salt and to the suppression of thermal undulation/protrusion repulsive forces for lipids on solid surfaces. At ionic strengths that cause precipitation of SLBs, it was found that addition of excess SUVs, at ratios where there were equal populations of SUVs and SLBs, restored the undulation/protrusion repulsive forces and restabilized the suspensions. We suggest that SUVs separate SLBs in the suspension, as observed by TEM, and that SLB-SLB interactions are replaced by SLB-SUV interactions. Decreasing the relative amount of lipid, to the extent that there was less lipid available than the amount required for complete bilayer coverage of the SiO(2), resulted in precipitation of the nanosystem by a process of nanoparticle lipid bridging. For this case, we postulate a process in which lipid bilayer patches on one nanoparticle collide with bare silica patches on another SiO(2) nanoparticle, forming a single bilayer bridge between them. TEM data confirmed these findings, thus indicating that lipid bridges are composed of half bilayers on adjoining SiO(2) nanoparticles.

Sustained Broad-Spectrum Antibacterial Effects of Nanoliposomes Loaded with Silver Nanoparticles

“…AgNPs of 5 ± 1 nm were used. These results were in agreement with those obtained by SEM and TEM as well as previous reports [19]. Nanoparticles showed low polydispersity indices (table 1).…”

Experimental Aspects of Colloidal Interactions in Mixed Systems of Liposome and Inorganic Nanoparticle and Their Applications

“…This is the case when either the radius of the particle ( R NP ) is larger than the vesicle radius ( R Ves ) or when the surface area of all particles is equal or larger than the total surface of the potentially formed SLB ( SA NP ≥ SA Ves —taking into account that when SA NP ≫ SA Ves nanoparticles are believed to be partially covered by lipid bilayer patches [91]).…”

Cell membrane disruption induced by amorphous silica nanoparticles in erythrocytes, lymphocytes, malignant melanocytes, and macrophages

“…It is noted that a major constituent of cell membranes is phosphatidylcholine (PC), which has a zwitterionic head group of the phosphate ester (ÀR(PO 4 À )R 0 À) and the quaternary amine (ÀN(CH 3 ) 3 + ) moieties and is more commonly found in the exoplasmic leaflet of a cell membrane. The interactions of silica particles with protein-free bilayers of PC have been investigated by the leakage of entrapped tracers from liposomes [56][57][58], the adsorption isotherms [57][58][59][60][61][62], the nuclear magnetic resonance (NMR) spectroscopy [63], the cryogenic transmission electron microscopy (Cryo-TEM) [64], the fluorescence microscopy and isothermal titration calorimetry [65], and the calorimetry, electrophoresis, dynamic light scattering (DLS), and Cryo-TEM [66,67]. The interactions of silica particles with supported membranes of PC have been studied by the electrochemistry and calorimetry [68] and the electrophysiology and fluorescence microscopy [69].…”