Colloid Chemistry - Prof. Koetz

Nanoparticle formation in polyelectrolyte-modified bilayer membrane systems

Our investigations have shown that it is surprisingly possible to introduce oppositely charged cationic polyelectrolytes into an ionically charged double layer membrane system (consisting of an anionic surfactant (SDS), decanol and water) without the system being separated. The polymer is incorporated directly into the double layer, attracts the oppositely charged head groups of the double layer membrane and causes a "roll-up" to form compact balls by partial charge neutralization. Figure 2 shows an electron microscope image of such a multivesicular superstructure.

Figure 2: Scanning electron micrograph of a multivesicular superstructure.

Neutron scattering experiments in combination with microcalorimetry showed that this process is temperature-dependent. Phospholipid-containing double layer systems showed similar behavior. This opens up the possibility of the controlled build-up of superstructures in biomembrane systems by incorporating oppositely charged polyelectrolytes, which is of particular interest in drug application. Such superstructures are also used as a template phase, with rod-shaped particles being formed predominantly. If phospholipid-containing vesicle systems are used as the template phase, flat triangles with {111} crystal planes are preferably formed on the top and bottom side of the platelets. High-resolution TEM images prove this experimentally (see Figure 3).

Figure 3: HRTEM image of a gold triangle with corresponding Fourier transformation.