Patterns of Supported Bilayers on SiO2/TiO2 Surfaces
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The work described below was performed in collaboration with the the BioInterface Group at the Swiss Federal Institute of Technology (Zürich) within the context of the Doctoral thesis of Fernanda F. Rossetti Interactions of Lipidic Assemblies with Metal Oxide Surfaces and Brush-like Polyelectrolytes.
This page was jointly designed by F. F. Rossetti and I. Reviakine.
Selectivity of liposome-surface interactions can be used to prepare patterns of bilayers
 We investigated supported bilayer formation from liposomes of various compositions on TiO2. Ralf Richter, while working in the group of Alain Brisson (Bordeaux, France) studied supported bilayer formation from lipsomes of various compositions on SiO2. Comparing the results for the two surfaces, we find that:
  • in the absence of Ca2+, liposomes composed of 20% DOPS and 80% DOPC form supported bilayers on silica but do not adsorb to titania;
  • in the presence of Ca2+, supported bilayers can be prepared from vesicles of this composition on titania as well as on silica.
Therefore, exposing a SiO2/TiO2 substrate (top right) to 80:20 DOPC:DOPS lipsomes in the absence of Ca2+ will result in lipid-free TiO2 areas and bilayer-covered SiO2 areas (middle right). In a second step, a bilayer can be prepared on TiO2 in the presence of Ca2+ (bottom right), without affecting the existing bilayer on SiO2.

The process is shown schematically on the right.

Substrates of the kind shown on the right were developed at the BioInterface group by Roger Michel in the course of his doctoral work on sellective molecular assembly patterning (SMAP). References on this subject can be found in the Publications page.
This image demonstrates that two bilayers, each containing a different fluorescently labelled lipid, can be prepared on a SiO2/TiO2 surface by the procedure described above. No intermixing is observed after > 10 hrs. In this experiment, biotinylated supported bilayers were used in the first step, and those containing Ni-chelator lipids - in the second step. These were then labelled with streptavidin and fluorescently-labeled biotinylated vesicles (red), and with green fluorescent protein (green), respectively. Details can be found in Rossetti et al. 2005 Langmuir 21, 6443.