Shape of things to comeEdible optical sensor to watch for bacteria in food

Imagine an edible optical sensor that could be placed in produce bags to detect harmful levels of bacteria and consumed right along with the veggies. Or an implantable device that would monitor glucose in your blood for a year, then dissolve. Scientists at Tufts University’s School of Engineering have demonstrated for the first time that it is possible to design such “living” optical elements that could enable an entirely new class of sensors. These sensors would combine sophisticated nanoscale optics with biological readout functions, be biocompatible and biodegradable, and be manufactured and stored at room temperatures without use of toxic chemicals. The Tufts team used fibers from silkworms to develop the platform devices. Tufts University has filed a number of patent applications on silk-based optics and is actively exploring commercialization opportunities. “Sophisticated optical devices that are mechanically robust yet fully biodegradable, biocompatible and implantable don’t exist today,” said principal investigator Fiorenzo Omenetto, associate professor of biomedical engineering and associate professor of physics. “Such systems would greatly expand the use of current optical technologies in areas like human and livestock health, environmental monitoring and food quality.” David Kaplan, professor and chair of the biomedical engineering department, explained: “For example, at a low cost, we could potentially put a bioactive silk film in every bag of spinach, and it could give the consumer a readout of whether or not E. coli bacteria were in the bag-before the food was consumed.” The Tufts research was published in a recent paper in Biomacromolecules (sub. req.; the paper, titled “Bioactive Silk Protein Biomaterial Systems for Optical Devices,” was written by by Brian Lawrence, graduate student in biomedical engineering; Mark Cronin-Golomb, associate professor, biomedical engineering; Irene Georgakoudi, assistant professor, biomedical engineering; Kaplan, and Omenetto).

Optics — the science of light and its interaction with matter — has fascinated generations of scientists such as Sir Isaac Newton. Current optical device platforms are based primarily on glass, semiconductors, plastics, or polymers. The harsh solvents and extreme temperatures needed for manufacture make it impossible to incorporate bioactive sensing components into the devices. Chemical residues and lack of biodegradability also limit environmental and medical applications. Furthermore, biological components typically need to be stored at controlled temperatures to retain their activity. The possibility of integrating optical readout and biological function in a single biocompatible device unconstrained by these limitations is tantalizing. Silk optics has captured the interest of the Defense Department,