Cohesive Living Bacterial Films with Tunable Mechanical Properties from Cell Surface Protein Display

Area of Science:

• Biomaterials Engineering
• Synthetic Biology
• Materials Science

Background:

• Engineered living materials (ELMs) integrate living organisms into functional materials.
• Current ELMs often rely on polymeric matrices, limiting genetic control over mechanical properties.
• Cell-surface protein display offers a new strategy for tuning material mechanics.

Purpose of the Study:

• To develop living materials with genetically tunable mechanical properties.
• To investigate the role of engineered cell-surface proteins in material behavior.
• To demonstrate self-healing capabilities in these novel materials.

Main Methods:

• Engineered *Escherichia coli* strains displaying elastin-like proteins (ELPs) were created.
• Surface-displayed ELPs (E6) and cysteine-modified ELPs (CE6) were used to form bacterial films.
• Mechanical properties were characterized using bulge testing and oscillatory stress tests.
• Self-healing was assessed after induced damage.

Main Results:

• E6 films exhibited soft mechanical properties (14 kPa modulus) and significant yielding.
• CE6 films showed a 3-fold increase in modulus (44 kPa), reduced yielding, and elastic behavior.
• CE6 films demonstrated autonomous self-healing, restoring mechanical integrity within hours.
• Significant hysteresis and plastic deformation were observed in E6 films, unlike CE6 films.

Conclusions:

• Cell-surface display of engineered proteins provides precise genetic control over living material mechanics.
• Cysteine modification of ELPs enhances material stiffness, elasticity, and self-healing.
• This approach enables the creation of programmable, self-healing biomaterials for diverse applications.