TY - JOUR
T1 - Supported lipid bilayer nanosystems
T2 - Stabilization by undulatory-protrusion forces and destabilization by lipid bridging
AU - Savarala, Sushma
AU - Monson, Frederick
AU - Ilies, Marc A.
AU - Wunder, Stephanie L.
PY - 2011/6/1
Y1 - 2011/6/1
N2 - 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/SiO2 nanosystems was analyzed as a function of ionic strength and as a function of the ratio of lipid/SiO2 surface areas, at pH = 7.6. Salt is necessary to induce supported lipid bilayer (SLB) formation for zwitterionic lipids on silica (SiO2) (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 SiO2, 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 SiO2 nanoparticle, forming a single bilayer bridge between them. TEMdata confirmed these findings, thus indicating that lipid bridges are composed of half bilayers on adjoining SiO2 nanoparticles.
AB - 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/SiO2 nanosystems was analyzed as a function of ionic strength and as a function of the ratio of lipid/SiO2 surface areas, at pH = 7.6. Salt is necessary to induce supported lipid bilayer (SLB) formation for zwitterionic lipids on silica (SiO2) (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 SiO2, 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 SiO2 nanoparticle, forming a single bilayer bridge between them. TEMdata confirmed these findings, thus indicating that lipid bridges are composed of half bilayers on adjoining SiO2 nanoparticles.
UR - http://www.scopus.com/inward/record.url?scp=79955424182&partnerID=8YFLogxK
U2 - 10.1021/la200636k
DO - 10.1021/la200636k
M3 - Article
C2 - 21500811
AN - SCOPUS:79955424182
SN - 0743-7463
VL - 27
SP - 5850
EP - 5861
JO - Langmuir
JF - Langmuir
IS - 10
ER -