Now, silk-based material programmed for pre-designed functions

Scientists have created a novel material from silk protein that can be preprogrammed with biological, chemical or optical functions, such as mechanical components that change colour with strain, deliver drugs or respond to light.
Using a water-based fabrication method based on protein self-assembly, researchers from Tufts University in the US generated three-dimensional bulk materials out of silk fibroin, the protein that gives silk its durability.
They manipulated the bulk materials with water-soluble molecules to create multiple solid forms, from the nano- to the micro-scale, that have embedded, pre-designed functions.
The researchers created a surgical pin that changes colour 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.

Although more research is needed, additional applications could include new mechanical components for orthopedics that can be embedded with growth factors or enzymes, a surgical screw that changes colour as it reaches its torque limits, hardware such as nuts and bolts that sense and report on the environmental conditions of their surroundings, or household goods that can be remolded or reshaped.
Silk's unique crystalline structure 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.
"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," said Fiorenzo G Omenetto, Professor at Tufts University's School of Engineering.

The study was published in the journal Proceedings of the National Academy of Sciences (PNAS).