42 research outputs found
Quantitative Studies of Antimicrobial Peptide Pore Formation in Large Unilamellar Vesicles by Fluorescence Correlation Spectroscopy (FCS)
Phase transitions and steady-state microstructures in a two-temperature lattice-gas model with mobile active impurities
Cationic liposomal drug delivery system for specific targeting of human cd14+ monocytes in whole blood
Remote Loading of <sup>64</sup>Cu<sup>2+</sup> into Liposomes without the Use of Ion Transport Enhancers
Due to low ion permeability of lipid bilayers, it has
been and still is common practice to use transporter molecules such
as ionophores or lipophilic chelators to increase transmembrane diffusion
rates and loading efficiencies of radionuclides into liposomes. Here,
we report a novel and very simple method for loading the positron
emitter <sup>64</sup>Cu<sup>2+</sup> into liposomes, which is important
for <i>in vivo</i> positron emission tomography (PET) imaging.
By this approach, copper is added to liposomes entrapping a chelator,
which causes spontaneous diffusion of copper across the lipid bilayer
where it is trapped. Using this method, we achieve highly efficient <sup>64</sup>Cu<sup>2+</sup> loading (>95%), high radionuclide retention
(>95%), and favorable loading kinetics, excluding the use of transporter
molecule additives. Therefore, clinically relevant activities of 200–400
MBq/patient can be loaded fast (60–75 min) and efficiently
into preformed stealth liposomes avoiding subsequent purification
steps. We investigate the molecular coordination of entrapped copper
using X-ray absorption spectroscopy and demonstrate high adaptability
of the loading method to pegylated, nonpegylated, gel- or fluid-like,
cholesterol rich or cholesterol depleted, cationic, anionic, and zwitterionic
lipid compositions. We demonstrate high <i>in vivo</i> stability
of <sup>64</sup>Cu-liposomes in a large canine model observing a blood
circulation half-life of 24 h and show a tumor accumulation of 6%
ID/g in FaDu xenograft mice using PET imaging. With this work, it
is demonstrated that copper ions are capable of crossing a lipid membrane
unassisted. This method is highly valuable for characterizing the <i>in vivo</i> performance of liposome-based nanomedicine with
great potential in diagnostic imaging applications
Remote-loading of liposomes with manganese-52 and in vivo evaluation of the stabilities of <sup>52</sup>Mn-DOTA and <sup>64</sup>Cu-DOTA using radiolabelled liposomes and PET imaging
Liposome accumulation in irradiated tumors display important tumor and dose dependent differences
Remote loading of liposomes with a <sup>124</sup>I-radioiodinated compound and their in vivo evaluation by PET/CT in a murine tumor model
Thermal undulations of quasi-spherical vesicles stabilized by gravity
The classical treatment of quasi-spherical vesicle undulations has,
in the present work, been reviewed and extended to
systems, which are affected by a gravitational field caused by a density
difference across the membrane. The effects have been
studied by the use of perturbation theory leading to corrections to the
mean shape and the fluctuation correlation matrix.
These corrections have been included in an analytical expression for
the flicker spectrum to probe how the experimentally
accessible spectrum changes with gravity. The results are represented
in terms of the gravitational parameter,
.
The contributions from gravity are in most experimental situations
small and thus negligible, but for values of
above a certain limit, the perturbational corrections must be
included. Expressions for the relative error on the flicker
spectrum have been worked out, so that it is possible to define
the regime where gravity is negligible. An upper limit of
has also been identified, where the error in all modes of
the flicker spectrum is significant due to
distortion of the mean shape