Motor-driven advection competes with macromolecular crowding to drive spatiotemporally heterogeneous transport in cytoskeleton composites

The cytoskeleton, a far-from-equilibrium network of biofilaments and their associated proteins, facilitate life-sustaining mesoscale transport of cellular cargo through a crowded, dynamic, and viscoelastic environment. Understanding the transport of particles traversing the cytoskeleton is critical to cellular processes such as mitosis, endocytosis, migration, and regeneration. Yet, at the same time, macromolecules and particles diffusing through active, crowded, or heterogeneous environments have been shown to exhibit widely varying and poorly understood anomalous transport properties that deviate significantly from normal Brownian diffusion. As such, dissecting the complex transport of particles through active matter that exhibits a combination of these complexities, remains a formidable challenge. Here, we investigate diffusive transport of spherical particles and DNA through in vitro motor-driven cytoskeleton composites using single particle tracking and differential dynamic microscopy. We show that myosin motors induce ballistic-like dynamics of the composites, leading entrained particles to exhibit superdiffusive, advective and Gaussian-like transport. Conversely, steric entanglements, connectivity and slow thermal relaxation of cytoskeletal filaments mediate heterogeneous, subdiffusive transport of confined particles. Additionally, we show that the topology of the DNA plays a strong role in determining the degree to which restructuring of the cytoskeleton can mediate advective transport, possibly due to a threading mechanism.