1 research outputs found
Phospholipid Composition Modulates Carbon Nanodiamond-Induced Alterations in Phospholipid Domain Formation
The
focus of this work is to elucidate how phospholipid composition
can modulate lipid nanoparticle interactions in phospholipid monolayer
systems. We report on alterations in lipid domain formation induced
by anionically engineered carbon nanodiamonds (ECNs) as a function
of lipid headgroup charge and alkyl chain saturation. Using surface
pressure vs area isotherms, monolayer compressibility, and fluorescence
microscopy, we found that anionic ECNs induced domain shape alterations
in zwitterionic phosphatidylcholine lipids, irrespective of the lipid
alkyl chain saturation, even when the surface pressure vs area isotherms
did not show any significant changes. Bean-shaped structures characteristic
of dipalmitoylphosphatidylcholine (DPPC) were converted to multilobed,
fractal, or spiral domains as a result of exposure to ECNs, indicating
that ECNs lower the line tension between domains in the case of zwitterionic
lipids. For membrane systems containing anionic phospholipids, ECN-induced
changes in domain packing were related to the electrostatic interactions
between the anionic ECNs and the anionic lipid headgroups, even when
zwitterionic lipids are present in excess. By comparing the measured
size distributions with our recently developed theory derived by minimizing
the free energy associated with the domain energy and mixing entropy,
we found that the change in line tension induced by anionic ECNs is
dominated by the charge in the condensed lipid domains. Atomic force
microscopy images of the transferred anionic films confirm that the
location of the anionic ECNs in the lipid monolayers is also modulated
by the charge on the condensed lipid domains. Because biological membranes
such as lung surfactants contain both saturated and unsaturated phospholipids
with different lipid headgroup charges, our results suggest that when
studying potential adverse effects of nanoparticles on biological
systems the role of lipid compositions cannot be neglected