Mechanisms of nanoparticle and bioparticle deposition - Kinetic aspects

Particle deposition phenomena were theoretically analyzed in terms of a hybrid theoretical approach where the bulk transport is described by continuity equations and the surface transport by the random sequential adsorption (RSA) models. RSA modeling furnishes maximum coverages and blocking functions for spherical and anisotropic particles. These parameters are used as boundary conditions for the bulk transport equation. This enables one to derive theoretical results describing kinetics of convection and diffusion-controlled transport of particles to interfaces, which is discussed next. The utility of this theoretical approach is confirmed by experimental data obtained for various colloid systems involving micro- and nanoparticles using optical and fluorescence microscopy AFM, SEM and TEM imaging of particle monolayers. Comparison of theoretical and experimental results shows that the electrostatic interactions play a dominant role affecting the maximum coverage of and the structure of deposited particle monolayers. Particle deposition on heterogeneous surfaces formed by a controlled deposition of nanoparticles and proteins (latex, hematite, fibrinogen) is also considered. These phenomena are properly interpreted in terms of the RSA model considering fluctuations in the particle density. The classical DLVO theory, based on the mean-field (averaged) zeta potential concept proved inadequate. It is also shown that the colloid particle deposition on protein monolayers can be used to efficiently determine the coverage and a real charge distribution under wet, in situ conditions. It is concluded that particle and protein deposition phenomena show deep analogies. This suggests that the results acquired for nanoparticles can be used as convenient reference systems for interpretation of molecular adsorption phenomena inaccessible to direct measurements. (C) 2013 Elsevier B.V. All rights reserved.