Transport of a self-propelled tracer through a hairy cylindrical channel: interplay of stickiness and activity

TL;DR

This study computationally explores how activity and stickiness influence the transport dynamics of a tracer in a crowded, polymer-grafted cylindrical channel, revealing complex behaviors relevant for cellular transport and artificial nanomachines.

Contribution

It demonstrates how activity can override stickiness effects and alter transport pathways, providing new insights into active transport in confined, crowded environments.

Findings

Passive tracers show subdiffusion with increased stickiness.

Active tracers exhibit faster, superdiffusive dynamics.

Activity influences the transport pathway and reduces stickiness effects.

Abstract

Active transport of biomolecules assisted by motor proteins is imperative for the proper functioning of cellular activities. Inspired by the diffusion of active agents in crowded cellular channels, we computationally investigate the transport of an active tracer through a polymer grafted cylindrical channel by varying the activity of the tracer and stickiness of the tracer to the polymers. Our results reveal that the passive tracer exhibits profound subdiffusion with increasing stickiness by exploring deep into the grafted polymeric zone, while purely repulsive one prefers to diffuse through the pore-like space created along the cylindrical axis of the channel. In contrast, the active tracer shows faster dynamics and intermediate superdiffusion even though the tracer preferentially stays close to the dense polymeric region. This observation is further supported by the sharp peaks in the density profile of the probability of radial displacement of the tracer. We discover that the activity plays an important role in deciding the pathway that the tracer takes through the narrow channel. Interestingly, increasing the activity washes out the effect of stickiness. Adding to this, van-Hove functions manifest that the active tracer dynamics deviates from Gaussianity, and the degree of deviation grows with the activity. Our work has direct implications on how effective transportation and delivery of cargo can be achieved through a confined medium where activity, interactions, and crowding are interplaying. Looking ahead, these factors will be crucial for understanding the mechanism of artificial self-powered machines navigating through the cellular channels and performing in vivo challenging tasks.