Researchers at Rice University have uncovered key genetic mechanisms that fine-tune the structure and mechanical behavior of engineered living materials (ELMs), paving the way for unprecedented control over how these bio-based materials respond to physical stress. Their findings, published in ACS Synthetic Biology, could lead to major breakthroughs in biomanufacturing, regenerative medicine, and even 3D printing of living structures.

At the heart of this discovery is a deeper understanding of how genetic modifications alter protein matrices—the protein-based scaffolds that give ELMs their shape and function. By tweaking specific genetic sequences, the research team demonstrated that small molecular adjustments could yield dramatic changes in material stiffness, elasticity, and response to external forces like stretching and compression.

Genetic Blueprints for Material Innovation

"We are engineering cells to create customizable materials with unique properties," said Caroline Ajo-Franklin, professor of biosciences and corresponding author of the study. "While synthetic biology has given us powerful tools to modify these materials, the direct connection between genetic sequence, material structure, and behavior has remained largely uncharted—until now."

To investigate this link, the team worked with Caulobacter crescentus, a bacterium previously engineered to produce a matrix-forming protein called BUD (bottom-up de novo). This protein facilitates bacterial adhesion and assembly into centimeter-scale structures—living materials dubbed BUD-ELMs.

By systematically altering the length of elastin-like polypeptides (ELPs)—protein segments within the BUD scaffold—the team produced three distinct material variants, each with unique physical properties:

• BUD40 (shortest ELPs) formed thick fibers and yielded a stiffer material.
• BUD60 (mid-length ELPs) balanced globules and fibers, demonstrating superior strength under mechanical stress.‍
• BUD80 (longest ELPs) formed thinner fibers, making it the least stiff and most fragile under deformation.

Advanced imaging and mechanical testing confirmed that these variations directly influenced how the materials responded to pressure and stress. Notably, BUD60 exhibited the best resilience, making it particularly promising for applications requiring robust, adaptable biomaterials, such as 3D bioprinting and controlled drug release.

From Bioengineering to Real-World Applications

Despite their differences, all three BUD-ELM materials shared two fundamental traits: they were highly water-retentive (comprising about 93% water by weight) and exhibited shear-thinning behavior, meaning they became less viscous under stress. These properties are particularly advantageous for biomedical applications like tissue engineering scaffolds and advanced drug delivery systems.

"This study is one of the first to focus on designing living materials with tailored mechanical properties rather than simply adding biological functions," said Esther Jimenez, a graduate student in biosciences and lead author of the paper. "By making small but deliberate changes to protein sequences, we’ve uncovered key principles for engineering bio-based materials with precision."

Beyond the biomedical sphere, the researchers envision far-reaching applications for these self-assembling, environmentally responsive materials. Potential uses include environmental remediation, biodegradable construction materials, and bioenergy harvesting, where engineered biomaterials could play a role in capturing and storing energy from natural processes.

"This work underscores the significance of understanding sequence-structure-property relationships," said Carlson Nguyen, a biosciences major and second author of the study. "By pinpointing how specific genetic modifications impact material performance, we’re laying the groundwork for the next generation of living materials."