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Liposomes, Exosomes, and Virosomes: From Modeling Complex
Membrane Processes to Medical Diagnostics and Drug Delivery
Poster Abstracts
98
12-POS
Board 6
Evolution of Cochleate Membrane Rolls From Unilamellar Liposomes
Tamás Bozó
1
, Richárd Brecska
1
, Imre Derényi
2
, Miklós Kellermayer
1,3
.
1
Semmelweis University, Budapest, Hungary,
2
Eötvös Loránd University, Budapest, Hungary,
3
Hungarian Academy of Sciences - Semmelweis University, Budapest, Hungary.
Addition of calcium ions to liposomes with negatively charged phospholipid headgroups may
lead to the formation of membrane rolls, the so-called cochleates. These structures have been
intensively studied as potential micro- and nanosized vehicles for drug delivery. However, little
is known about how they evolve from liposomes and what factors modulate their generation.
The aim of our study was to follow and quantify the formation of cochleates from unilamellar
liposomes. Samples were analyzed by using phase contrast and atomic force microscopy (AFM)
imaging and force spectroscopy.
When divalent cations were added to dioleoyl phosphatydilserine liposomes, they first
aggregated in form of multilamellar vesicles. Cochleates could be identified only hours later and
it took a few days to weeks until they become the dominant phase of the sample. Partially
(un)rolled particles were found occasionally, indicating that membrane layers may flow over
each other. A particle counting method was utilized to quantify the efficiency of cochleate
formation at various preparation conditions. The results indicate that the rate of calcium addition
has a key role in cochleate formation. Nanomechanical perturbations revealed that cochleates are
made up of solid-like membrane layers which are mechanically independent from each other,
thus allowing for shape changes and slow dynamics.