Active Nematics Reinforce the Ratchet Flow in Dense Environments Without Jamming

Area of Science:

• Biophysics
• Cell Biology
• Soft Matter Physics

Background:

• Biological systems like bacteria and cells exhibit active polar or nematic behavior, forming local order during migration.
• Understanding and controlling collective cell motion is crucial for applications in tissue engineering and developmental biology.
• Neural progenitor cells (NPCs) are treated as nematics due to their back-and-forth migration without distinct head or tail orientation.

Purpose of the Study:

• To control the collective motion of neural progenitor cells (NPCs) in vitro using the ratchet effect.
• To investigate the role of confinement geometry and active forces in directing cell migration.
• To explore the physical mechanisms underlying topotaxis in dense cell populations.

Main Methods:

• Utilizing a physical ratchet effect to guide cell movement.
• Employing splay-shaped confinements to modulate collective cell dynamics.
• Developing and applying an agent-based simulation to model cell behavior.
• Observing collective motion in dense NPC populations without explicit jamming.

Main Results:

• Demonstrated controllable directional cell flow of NPCs using engineered ratchets.
• Showcased the synergistic effect of ratchet asymmetry and nematic order in reinforcing directional movement.
• Identified that confinement geometry significantly influences collective cell dynamics in crowded 2D environments.
• Agent-based simulations revealed the interplay between physical constraints and active cell forces.

Conclusions:

• The ratchet effect offers a viable strategy for controlling collective cell transport in vitro.
• Asymmetric ratchets combined with nematic cell order can effectively direct cell populations.
• Findings provide insights into topotaxis mechanisms in confined, dense cell populations.
• This work contributes to understanding the physical regulation of collective cell behavior.