Polymer-Supported Lipid Bilayers on Benzophenone-Modified Substrates

Abstract

Solid-supported lipid membranes are important for their roles in fundamental biophysical research as well as in applications such as biosensors. In our study, lipopolymers containing alkyl side chains were synthesized and a mixture of the lipopolymer and free lipids was preorganized at the air-water interface and then transferred to a solid substrate using the Langmuir-Blodgett technique. A photochemical reaction between a substrate-functionalized benzophenone and C-H bonds on the lipopolymer was used to attach the lipopolymers to the substrate. The final assembly of the membrane was completed by vesicle fusion. Langmuir film experiments at the air-water interface indicate tighter molecular packing for the lipopolymers with 28 mol % alkyl side chains than for the ones with 22 mol %. Atomic force microscopy images point to phase separation of lipopolymers on the substrates due to their dewetting from hydrophobic surfaces. However, a mixture of lipopolymers and free lipids formed a smooth film on the same substrate. After the addition of the second lipid layer on the lipopolymer/free lipid layer, the fluorescence images of the polymer-supported bilayer suggested that the distal lipid layer is homogeneous on the micrometer scale. The relaxation of the fluorescent probe lipids was analyzed after application of an electric field to determine their diffusion coefficient; the distal lipid layer was mobile with an average diffusion coefficient of ∼0.1 µm 2 /s. Moreover, the immobile fraction of the lipids in the distal layer was estimated to be around 15%.

Tribological Properties of Ultra-Thin Functionalized Polyethylene Film Chemisorbed on Si with an Intermediate Benzophenone Layer

“…After modifying with benzophenone, the water contact angle of Si/Ph 2 CO is hydrophobic at 86°. This value correlates with the measurement of Shen et al [33]. fPE layer on Si/Ph 2 CO sample has a contact angle of 80°which is slightly less than the reported values for the bulk polyethylene (91°-97°) [34,35].…”

Coarse-grained modeling of interactions of lipid bilayers with supports

“…To address this problem several methods have been developed to increase the spacing between the bilayer and substrate. 15,18,[28][29][30] Nonetheless, measurements of pure and mixed lipid membranes performed directly on supports remain a valuable source of information on the nature of lipid-lipid and lipid-solvent interactions.…”

Structural characterization of an elevated lipid bilayer obtained by stepwise functionalization of a self-assembled alkenyl silane film

“…For example, an oxide surface was first modified by benzophenone and, in a second step, a lipid-containing poly͑2-ethyl-2-oxazoline͒ was grafted to this surface by photocrosslinking. 26 A similar two step strategy has been employed for gold substrates where in a first step a thiopeptide was chemisorbed to a gold surface, and in a second step, its COOH termini were functionalized with DMPE lipids via N-hydroxysuccinimide ͑NHS͒ chemistry to form a thiopeptide-tethered lipid monolayer. 27 This strategy is very useful because it involves surface lipid tethering via stable amide bonds.…”