Further understanding of cellular processes and communication strategies, promotes continuous progress in the design of synthetic biological systems and mimicking the functional components of cells. Introducing more complex internal structure into liposomes, by internalizing water soluble copolymer poly-N-isopropylacrylamide-Vinyl Ferrocene (PNIPAAm-VFc), is a suitable method to mimic macromolecular crowding and to achieve localized compartmentalization, thus approaching more complex architectures within lipid vesicles.
PNIPAAm-VFc is the thermo-responsive polymer, which contracts after increasing the temperature above its Lower Critical Solution Temperature (LCST). During our investigation, we observed an exceptionally strong interaction between PNIPAAm-VFc and the vesicle membrane, numerous lipid nanotubes were drawn from the vesicle membrane, leading to spontaneous morphological changes of the vesicle. Moreover, internalization of vesicular membrane material, have been observed during this process.
Figure 1 Behavior of the vesicle system with PNIPAAm-VFe containing 3.0%wt of VFc. Panel A shows the natural state of the GUV at room temperature, prior to any temperature increase. Panels B-J show a confocal image sequence of the coarsening phenomena, above the LCST (33°C), and the combination of membrane protrusions. [1]
1. Wegrzyn Ilona, Jeffries Gavin D. M., Nagel Birgit, Katterle Martin, Gerrard Simon R., Brown Tom, Orwar Owe, Jesorka Aldo, "Membrane Protrusion Coarsening and Nanotubulation within Giant Unilamellar Vesicles", Journal of the American Chemical Society, 2011, 133, 45: 18046-18049, pdf, SI.
2. Osinkina, L., et al., A Method for Heat-Stimulated Compression of Poly(N-isopropyl acrylamide) Hydrogels Inside Single Giant Unilamellar Vesicles, Langmuir, 2010, 26(1): p. 1-4, pdf.
3. Markstrom, M., et al., Dynamic microcompartmentalization of giant unilamellar vesicles by sol gel transition and temperature induced shrinking/swelling of poly(N-isopropyl acrylamide), Soft Matter, 2007, 3(5): p. 587-595.