(560b) Polymer-Linked Emulsions As Fully Synthetic Tissue Mimics to Evaluate Nanoparticle Transport

Adding end-functionalized polymers to an emulsion suspension arranges the emulsion droplets into hierarchical structures that percolate the material, significantly augmenting the material’s elasticity and introducing a finite yield stress. These complex systems exhibit dynamic relaxations intermediate between those observed in dense colloidal suspensions and polymer networks. Furthermore, the structure of the emulsions can be tuned by the polymer molecular weight, which controls the stochasticity of bridge formation. As a result, we find that this class of materials successfully replicate the structure, mechanics, and dynamics of soft, cellularized tissues. Here, we explore how nanoparticles transport through these polymer-linked emulsions with the goal of understanding nanoparticle transport in biological systems. We vary the nanoparticle size, polymer concentration, and polymer molecular weight and evaluate how these properties affect transport properties, including long-time diffusivity, short-time localizations, and non-Gaussian distributions of displacements. Small particles exhibit faster-than-expected diffusion whereas large particles couple to the material viscoelasticity. Furthermore, nanoparticles readily explore space for samples prepared with a high molecular weight linker but are preferentially located in low permeability zones for emulsions containing a low molecular weight linker. We attribute these differences to the bridging probability of the polymers in which high M_w polymers readily form bridges and therefore generate a homogeneous network, but low M_w polymers struggle to bridge droplets and produce a heterogeneous fluid of dense clusters. Our findings elucidate how nanoparticle transport depends on structure, dynamics, and mechanics in dense suspensions and biological environments, which begins to inform the design of advanced nanoparticle vectors.