2 research outputs found
Controlling the Localization of Polymer-Functionalized Nanoparticles in Mixed Lipid/Polymer Membranes
Surface hydrophobicity plays a significant role in controlling the interactions between nanoparticles and lipid membranes. In principle, a nanoparticle can be encapsulated into a liposome, either being incorporated into the hydrophobic bilayer interior or trapped within the aqueous vesicle core. In this paper, we demonstrate the preparation and characterization of polymer-functionalized CdSe NPs, tuning their interaction with mixed lipid/polymer membranes from 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phophocholine and PIB<sub>87</sub>-<i>b</i>-PEO<sub>17</sub> block copolymer by varying their surface hydrophobicity. It is observed that hydrophobic PIB-modified CdSe NPs can be selectively located within polymer domains in a mixed lipid/polymer monolayer at the air/water interface, changing their typical domain morphologies, while amphiphilic PIB-PEO-modified CdSe NPs showed no specific localization in phase-separated lipid/polymer films. In addition, hydrophilic water-soluble CdSe NPs can readily adsorb onto spread monolayers, showing a larger effect on the molecule packing at the air/water interface in the case of pure lipid films compared to mixed monolayers. Furthermore, the incorporation of PIB-modified CdSe NPs into hybrid lipid/polymer GUVs is demonstrated with respect to the prevailing phase state of the hybrid membrane. Monitoring fluorescent-labeled PIB-CdSe NPs embedded into phase-separated vesicles, it is demonstrated that they are enriched in one specific phase, thus probing their selective incorporation into the hydrophobic portion of PIB<sub>87</sub>-<i>b</i>-PEO<sub>17</sub> BCP-rich domains. Thus, the formation of biocompatible hybrid GUVs with selectively incorporated nanoparticles opens a new perspective for subtle engineering of membranes together with their (nano-) phase structure serving as a model system in designing functional nanomaterials for effective nanomedicine or drug delivery
Temperature-Dependent In-Plane Structure Formation of an X‑Shaped Bolapolyphile within Lipid Bilayers
Polyphilic compound B12 is an X-shaped
molecule with a stiff aromatic
core, flexible aliphatic side chains, and hydrophilic end groups.
Forming a thermotropic triangular honeycomb phase in the bulk between
177 and 182 °C but no lyotropic phases, it is designed to fit
into DPPC or DMPC lipid bilayers, in which it phase separates at room
temperature, as observed in giant unilamellar vesicles (GUVs) by fluorescence
microscopy. TEM investigations of bilayer aggregates support the incorporation
of B12 into intact membranes. The temperature-dependent behavior of
the mixed samples was followed by differential scanning calorimetry
(DSC), FT-IR spectroscopy, fluorescence spectroscopy, and X-ray scattering.
DSC results support in-membrane phase separation, where a reduced
main transition and new B12-related transitions indicate the incorporation
of lipids into the B12-rich phase. The phase separation was confirmed
by X-ray scattering, where two different lamellar repeat distances
are visible over a wide temperature range. Polarized ATR-FTIR and
fluorescence anisotropy experiments support the transmembrane orientation
of B12, and FT-IR spectra further prove a stepwise “melting”
of the lipid chains. The data suggest that in the B12-rich domains
the DPPC chains are still rigid and the B12 molecules interact with
each other via π–π interactions. All results obtained
at temperatures above 75 °C confirm the formation of a single,
homogeneously mixed phase with freely mobile B12 molecules