Rigidity Governs Entrainment of Bacteria Cells in Biopolymer Scaffolds

Area of Science:

• Biomaterials Science
• Soft Matter Physics
• Cellular Engineering

Background:

• Embedding cells in biopolymer networks creates dynamic materials for applications like tissue engineering.
• Cellular influence on material properties depends on biopolymer physical characteristics and component interactions.

Purpose of the Study:

• Investigate how biopolymer stiffness and cross-linking affect cell entrainment within networks.
• Analyze how embedded cells restructure biopolymer networks.

Main Methods:

• Designed composites of *Escherichia coli* cells and either actin filaments or microtubules.
• Characterized effects of cell volume fraction and filament cross-linking on composite structure and interactions.

Main Results:

• Entropically driven depletion interactions cause filament bundling at intermediate cell densities, more so with actin than microtubules.
• Actin cross-linking enhances cell clustering and cell-filament colocalization compared to entanglement.
• Microtubule cross-linking suppresses cell-induced restructuring and colocalization compared to entanglement.

Conclusions:

• Biopolymer stiffness and connectivity can selectively tune composite properties and cell entrainment.
• Findings are relevant for applications ranging from tissue engineering to biocement development.