Interplay between hydrodynamic and direct interactions using liposomes

This work deals with the short-time effective diffusion coefficient of charged and uncharged liposomes, measured ~as a function of the volume fraction! using fiber optic dynamic light scattering. Particularly, we are interested in the interplay between electrostatic and hydrodynamic interactions on the diffusion of these lipid vesicles. Regarding the charged liposome, it has been found that the effective diffusion coefficient can be theoretically justified for volume fractions not exceeding certain critical value. In applying the theoretical approach, a surface charge has been obtained which is consistent with the electrokinetic characterization of the liposome. Regarding the uncharged liposome, the hard-sphere model seems to account for reasonably well the self-diffusion data. In addition, comparing the measurements of the short-time self-diffusion coefficient for both liposomes, we conclude that strong electrostatic forces ~direct interactions! slow down diffusion processes. © 2003 American Institute of Physics. @DOI: 10.1063/1.1578628#