A study of the fractal dimension of the aggregation of three different types of large unilamellar vesicles, formed by egg yolk phosphatidylcholine (EYPC), dimyristoyl-phosphocholine (DMPC), and dipalmitoyl-phosphocholine (DPPC), in the presence of ${\mathrm{La}}^{3+}$, is presented. Aggregate liposome fractal dimensions were calculated by two methods, aggregation kinetics, using the approaches diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA) and angle-scattering light dispersion. Electrophoretic measurements show a similar variation of the zeta potential ($\zeta$ potential) for EYPC and DPPC, with a small increase of initial positive values. However, the $\zeta$ potential of DMPC changes from a initial negative value to near zero with increasing ${\mathrm{La}}^{3+}$ concentration. The evolution of the aggregate sizes was followed by light scattering. DPPC and DMPC show a RLCA regimen growth at low ${\mathrm{La}}^{3+}$ concentrations and a DLCA regimen at higher concentrations. In the case of EYPC, the final size of aggregation strongly depends on ${\mathrm{La}}^{3+}$ concentration. The calculated fractal dimension is in the range 1.8 to 2.1.

• Received 8 March 2007

DOI:https://doi.org/10.1103/PhysRevE.76.011408