Contrasting nanoparticle diffusion in branched polymer and particulate solutions: more than just volume fraction

Abstract

We contrasted the diffusion of gold nanoparticles (AuNPs) in crowded solutions of a randomly branched polymer (dextran) and rigid, spherical particles (silica). The goal was to understand the roles played by the probe size and structure of the crowding agent in determining the probe diffusion. AuNPs of two different sizes (2.5 nm & 10 nm), dextran of molecular weight 70 kDa and silica particles of radius 10 nm were used. Our results indicated that the AuNP diffusion can be described using the bulk viscosity of the matrix and hydrodynamically dextran behaved similar to a soft colloid. In all situations, we observed normal diffusion except for 2.5 nm sized AuNPs in dextran solution at a higher volume fraction. This is caused by transient trapping of particles within the random branches. The results showed the importance of macromolecular architecture in determining the transport properties in intracellular matrix and in cells with spiny dendrites.