(325g) Brownian/Ballistic Motion of Charged Colloidal Particles in the Proximity of Charged Surfaces

The purpose of this work is to characterize the influence of surface functionalization on the behavior (Brownian and ballistic movement) of charged colloidal particles located close to those surfaces. Knowledge of these phenomena is relevant for the engineering of carrier systems with applications to drug delivery methods or the modification of the adhesion properties of surfaces of tissues and biomaterials.

In this work, we used fluorescent colloidal particles suspended in proximity of surfaces functionalized with different biomolecules (Poly-L-Lysine, Hyaluronic Acid and Phosphoryl Choline). The colloidal particles were tracked three-dimensionally by digital video microscopy. From their trajectories we computed their mean square displacement to calculate the diffusion coefficient in directions parallel and perpendicular to the surface as well as the mean displacement to calculate the mean perpendicular velocity as a function of the particle distance from the surface. We used colloidal particles with different surface charges, and found differences in the parallel and the perpendicular diffusions highly dependent on the interfacial characteristics and adsorption of the colloidal particles and the surfaces. We also registered ballistic behavior close to the surface that may be attributed to the electrostatic interactions of the surfaces.