Engineering Living Materials with Tailored Properties

Researchers from Rice University have identified new sequence-structure-property relationships for tailoring engineered living materials (ELMs). These relationships allow for more precise control over their structure and response to deformation forces such as stretching or compression.

The research, published in the study ACS Synthetic Biology, centers on modifying protein matrices, which are networks of proteins that provide structural support to ELMs. Through small genetic modifications, the team demonstrated significant changes in the behavior of these materials.

These insights could lead to advancements in areas such as tissue engineering, drug delivery, and even 3D printing of living devices.

We are engineering cells to create customizable materials with unique properties. While synthetic biology has given us tools to tweak these properties, the connection between genetic sequence, material structure, and behavior has been largely unexplored until now.”

Caroline Ajo-Franklin, Professor and Study Corresponding Author, Rice University

The researchers utilized synthetic biology techniques with a bacterium called Caulobacter crescentus. Previous lab members had engineered the bacteria to produce a protein called BUD (short for “bottom-up de novo”), which enables cells to adhere to one another and form a supportive matrix. This allowed the bacteria to grow into centimeter-scale structures, referred to as BUD-ELMs.

Using this engineering strategy, the team adjusted the length of specific protein segments known as elastin-like polypeptides (ELPs) to create new materials. They analyzed the original midlength BUD-ELM alongside two new variants, each exhibiting distinct properties.

The first material, BUD₄₀, had the shortest ELPs and formed thicker fibers, resulting in a stiffer bulk material. The second material, BUD₆₀, with midlength ELPs, produced a mix of globules and fibers, yielding the strongest material under deformation oscillation stress.

The third variant, BUD₈₀, with the longest ELPs, formed thinner fibers, creating a less stiff material that was more prone to breaking under deformation stress.

Advanced imaging and mechanical testing revealed that these differences were not merely superficial but also influenced how the materials responded to stress and pressure. For instance, BUD₆₀ demonstrated greater resilience to force and better adaptability to environmental changes, making it particularly suitable for applications such as 3D printing or drug delivery.

All three materials shared two key characteristics: they exhibited shear-thinning behavior and retained a high water content approximately 93% of their weight. These properties make them ideal for biomedical applications, such as scaffolds for supporting cell growth in tissue engineering or systems for controlled drug delivery.

This study is one of the first to focus on building living materials from the ground up with tailored mechanical properties rather than just adding biological functions. By making small tweaks to protein sequences, we have gained valuable insights into how to design materials with specific mechanical properties.”

Esther Jimenez, Graduate Student and Study First Author, Rice University

The potential applications extend beyond biomedicine; these self-assembling materials could also be adapted for environmental cleanup or renewable energy uses, such as constructing biodegradable structures or leveraging natural processes to generate energy.

“This work emphasizes the importance of understanding sequence-structure-property relationships. By identifying how specific genetic modifications affect material properties, we are building a foundation for designing next-generation living materials,” said senior Carlson Nguyen, a biosciences major and second author of the study.