Non-Technical: This award by the Biomaterials program in the Division of Materials Research to California Institute of Technology is to explore new strategies for the design of tough, soft, protein-based materials. The materials of interest are hydrogels, polymeric materials that are highly swollen by water. Like the soft tissues of plants and animals, hydrogels exhibit a wide range of interesting and useful properties, including - most importantly - the capacity to respond to chemical and physical signals by changing shape and volume. But synthetic hydrogels are not very tough; in many cases it does not require much energy to cause them to fail. This project exploits the power of genetic engineering to design new protein-based hydrogels that show improved toughness. Artificial genes are used to encode protein sequences that dissipate energy upon deformation; the dissipated energy is then no longer available to cause the material to fail while in use. Improvements in toughness will lead to new applications of hydrogels in drug and gene delivery, tissue engineering, cell encapsulation and adhesion. The project provides important educational, training and outreach opportunities for graduate and undergraduate students. Additionally, the research activities of this project will be integrated with the "Genes to Gels," program at Caltech that will introduce high school students and teachers to research at the interface between the biological sciences and materials science. These high school students and teachers from the public schools in the greater Los Angeles area are expected to gain greatly with this hands-on research experience.
Hydrogels are crosslinked polymer networks of high water content. While their physical and chemical properties vary widely, most hydrogels form soft, elastic materials. This makes them excellent candidates to replace the natural extracellular matrix in soft tissue engineering and in vitro cell culture. But the same properties that make hydrogels appealing for these applications can also lead to brittle materials. This project uses genetic engineering to program the assembly of artificial protein hydrogels, with a specific focus on improving toughness. Genetic methods provide a level of control of chain sequence that is still not possible in conventional polymer synthesis, and the ease of sequence variation allows detailed exploration of the molecular processes that determine gel toughness. The toughening strategies developed in this work will establish general, broadly useful approaches to the design of tough, pliable materials. The project engages students at all levels from high school to graduate study, and includes science teachers drawn from high schools throughout the Los Angeles basin.