Programmable solid materials formed from silk protein are now possible thanks to researchers in the US. These materials can be tailored to have properties of interest from the biological, chemical, or optical perspective and potentially be used as mechanical components that change color with strain, act as drug delivery agents or have a useful response to light. The team from Tufts University in Medford, Massachusetts, describes the work in the Proceedings of the National Academy of Sciences (USA). [Benedetto Marelli Proc Natl Acad Sci (2016) DOI: 10.1073/pnas.1612063114.]
It is silk's unique crystalline structure that makes it one of nature's toughest materials. Fibroin, an insoluble protein found in silk, has a remarkable ability to protect other materials while being fully biocompatible and biodegradable.
By exploiting protein self-assembly in water Fiorenzo Omenetto and colleagues were able to generate three-dimensional bulk materials from the durable protein silk fibroin which they could then form into solid forms. For example, they created a surgical pin that changes color as it nears its mechanical limits and is about to fail, functional screws that can be heated on demand in response to infrared light, and a biocompatible component that enables the sustained release of bioactive agents, such as enzymes. One might envisage a functional and biocompatible screw for use in prosthetic joints where it can be tightened and embedded using infrared light and carry growth factors into the attachment site to encourage the body to accept the prosthetic.
Critically, making a single material with multiple properties at the intersection of biology and technology has been possible with hierarchical materials to some extent and by embedding functional groups within such a material. Science has had greatest success in this endeavor with two-dimensional materials but three-dimensional could expand the repertoire greatly. The team explains the significance of their work in that they have demonstrated an entirely water-based sol-gel-solid process to generating 3D materials that have biological and other functionality. "This approach is a step toward the development of multifunctional devices that may liaise between the biotic and abiotic worlds," they report.
"The ability to embed functional elements in biopolymers, control their self-assembly, and modify their ultimate form creates significant opportunities for bio-inspired fabrication of high-performing multifunctional materials," explains Omenetto. The complete research team is large, but it is members Omenetto, Benedetto Marelli, and David Kaplan who are listed as inventors in the patent application based on this silk technology carried out with backing from the US Office of Naval Research.
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".