3 research outputs found
Deposition of Metal Nanoparticles on Phospholipid Multilayer Membranes Modified by Gramicidin
A planar
dipalmitoyl phosphatidylcholine (DPPC) multilayer phospholipid
membrane was structurally modified by introducing a transmembrane
protein, gramicidin (up to 25 mol %), to study its effect on the metal
nanoparticles deposited on the membrane. Without gramicidin, when
3-nm-thick Ag, Sn, Al, and Au were deposited, the nanoparticles hardly
nucleated on the DPPC membrane in rigid gel state (except for Au);
however, the gramicidin addition dramatically enhanced the DPPC membrane
surface’s affinity for metal atoms so that a dense array of
metal (Ag, Sn, and Au) or metal-oxide (Al-oxide) nanoparticles was
produced on the membrane surface. The particle sizes ranged from 3
to 15 nm depending on the metal and gramicidin concentration, whereas
the particle density was strongly dictated by the gramicidin concentration.
The proposed method provides a convenient, generally applicable synthesis
route for preparing different metal or metal-oxide nanoparticles on
a relatively robust biocompatible membrane
Stabilization of Solid-Supported Phospholipid Multilayer against Water by Gramicidin Addition
It was demonstrated that hydrophobicity
of solid supported planar
dipalmitoyl phosphatidylcholine (DPPC) phospholipid multilayer can
be greatly increased by incorporating a transmembrane protein, gramicidin,
into the DPPC membrane. The contact angle of deionized water droplet
on the gramicidin-modified DPPC membrane increased from 0° (complete
wetting) without gramicidin to 55° after adding 15 mol % gramicidin.
The increased hydrophobicity of the gramicidin-modified DPPC membrane
allowed the membrane to remain stable at the air/water interface as
well as underwater. The Au nanoparticles deposited on the gramicidin-modified
DPPC membrane reproduced the characteristic surface plasmon resonance
peak after being kept underwater or in phosphate-buffered saline solution
for 5 days, attesting to the membrane stability in an aqueous environment.
The enhanced underwater stability of the lipid multilayer substantially
broadens the potential application of the lipid multilayer which includes
biosensing, enzymatic fuel cell, surface enhanced Raman spectroscopy
substrate
Effect of Temperature and Humidity on Coarsening Behavior of Au Nanoparticles Embedded in Liquid Crystalline Lipid Membrane
Coarsening behavior of the Au nanoparticles produced
by thermal evaporation of Au onto a liquid crystalline lipid (1,2-dioleoyl-3-trimethylammonium-propane,
DOTAP) membrane was investigated by subjecting the nanoparticle-embedded
DOTAP membrane to two different annealing conditions (at 100 °C
under no humidity and at 20 °C and 80% relative humidity). Although
the coarsening rate was relatively slow because of the low temperature
(from 5.6 nm in the as-deposited state to ∼7 nm after 30 h),
it was identified that at 100 °C without humidity the Au nanoparticles
resulted in shape refinement whereas the high humidity at 20 °C
induced self-organization of the nanoparticles into a monolayer. It
was also found that annealing in both cases tended to segregate the
lipid molecules from the nanoparticle array and forced the nanoparticles
into a tighter area. In the case of the high-humidity sample, the
lipid segregation eventually led to extensive coalescence of the Au
nanoparticles