Supported phospholipid bilayer interaction with components found in typical room-temperature ionic liquids - a QCM-D and AFM study

Authors: Evans, Kervin

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2008
Publication Date: 4/4/2008
Citation: Evans, K.O. 2008. Supported phospholipid bilayer interaction with components found in typical room-temperature ionic liquids - a QCM-D and AFM study. International Journal of Molecular Sciences. 9:498-511.

Interpretive Summary: Utilization of vegetable oils as new products requires novel reaction conditions. These novel conditions have often made use of immobilized enzymes on an inert surface and room-temperature ionic liquids (liquid salts) which assist the enzymes in maintaining function on the surface. However, some enzymes have shown a loss of activity when placed in some room-temperature liquid salts. A method of protection for the enzymes is using lipid films. However, the current data does not address interactions of room-temperature liquid salts and lipids. Results from the current study show that two common components of liquid salts either disrupted nearly the entire lipid film or created patches within the film, whereas one room-temperature liquid salt formed an additional film on top of the lipid film. These fundamental results will be used by us and other scientists as a foundation to better understand the conditions which allow a protective lipid layer to remain stable in a room-temperature liquid salt.

Technical Abstract: Quartz crystal microbalance with dissipation monitoring and atomic force microscopy were combined to evaluate the defects created by room-temperature ionic liquid anion and cation in a supported phospholipid bilayer composed of Zwitterionic lipids on a silica surface. The cation 1-octyl-3-methyl imidazolium was shown to remove lipids from the bilayer, increase the roughness to approximately 2.8 nm (~0.2 for stable supported bilayer) and possibly redeposit lipids with entrapped water. The anion bis(trifluoromethylsulfonyl)imide was found to leave distinct defects within the bilayer that had large pore-like interiors which left the surrounding bilayer intact. However, the ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide formed a film over the supported bilayer. This work demonstrates, for the first time, the direct effects common components of ionic liquids have on a supported phospholipids bilayer.