Polarization of cells and soft objects driven by mechanical interactions: consequences for migration and chemotaxis

Area of Science:

• Soft matter physics
• Biophysics
• Cellular mechanics

Background:

• Self-propelled soft objects, such as biological cells, exhibit complex behaviors like polarization and motility.
• Understanding the physical mechanisms governing these behaviors is crucial for various fields, from developmental biology to biomimetic engineering.

Purpose of the Study:

• To develop a generic model for the polarization and motility of self-propelled soft objects.
• To investigate the role of mechanical interactions and substrate properties in emergent cell behaviors.
• To explore mechanisms for optimizing motility and achieving chemotaxis.

Main Methods:

• Modeling active forces generated by cells as oscillating force multipoles at the cell-substrate interface.
• Analyzing long-range mechanical interactions mediated by intracellular and substrate components.
• Investigating the influence of system parameters like oscillation frequency, viscosity, and cellular noise.

Main Results:

• Cell polarization emerges naturally from mechanical interactions, but motility requires substrate-mediated forces.
• Optimal motility is achieved by matching oscillation frequency to system relaxation time or matching viscosities.
• Cellular noise can disrupt polarization, and motion persistence depends on cell size and substrate viscosity.

Conclusions:

• The model provides insights into how physical interactions drive cell polarization and motility.
• Chemotaxis can be achieved by modulating motion persistence, similar to bacterial 'run and tumble' behavior.
• The findings have implications for understanding biological self-propulsion and designing artificial micro-swimmers.