Tufts University researchers create ‘E.coli sensors’ using silk

Technology may warn consumers about food safety risk

By BOB KEEFE

Cox News Service

Thursday, August 14, 2008

Source of Article: http://www.ajc.com/health/content/health/stories/2008/08/14/silk_food_safety.html

To make sure you’re not eating contaminated spinach or tomatoes, you might someday want to sprinkle special silkworm silk on your salad.

Researchers at Tufts University in Massachusetts say they’ve discovered a way to make “edible optics” from the silk that can be used as sensors for E.coli, salmonella and other potentially deadly contaminants.

By manipulating the natural optical traits of silk, researchers could “program” the sensors to display a hologram warning or change color when they come into contact with unwanted bacteria, the researchers say.

“This is something that would be similar to the hologram on your Visa card,” said Tufts researcher Fiorenzo Omenetto.

Cheap, silk-based sensors that resemble transparent pieces of thin plastic could be tossed into a bag of produce, or even used to make the produce bags themselves, researchers say. Films made from silkworm silk could be used to coat salad tongs in a restaurant, or even be shredded and sprinkled on top of your food.

Omenetto says that in his experience, it has almost no taste.

Tufts researchers recently published academic papers explaining their silkworm sensors and filed for patent applications.

They expect to begin producing prototypes within a year. If they’re successful, such sensors could possibly be on the market within the next several years. Sensors could be manufactured for as little as a few pennies each.

Scientists for years have been experimenting with different kinds of bacteria sensors for food. Researchers at Georgia Tech in Atlanta, for instance, have created electronicbiosensors that can identify bacteria in poultry plants, while scientists at Texas A&M University, Georgia Tech and other schools are experimenting with “electronic noses” and other types of semiconductor-based sensors designed for food safety.

What makes the Tufts sensors unique is that they’re natural, organic and completely edible, Omenetto said. They’re also biodegradable and don’t require refrigeration.

“You don’t have to eat it, but if you do it’s okay,” he said. The same can’t be said about electronics-based sensors.

Sensors made from silk — among the strongest substances found in nature — also are much cheaper and more environmentally friendly than electronics-based sensors. The only factory needed for the raw materials is a grove of mulberry trees,Omenetto said.

To make the sensors, Tufts researchers boil the cocoons of Bombyx silkworms, then extract sericin proteins — the glue-like substance that holds the cocoons together. The purified silk is then poured into molds and dried.

By tapping into the same natural optical properties that can make silk ties or shirts shiny and iridescent, researchers can manipulate the purified silk so that it changes color when it comes into contact with specific substances, like food-borne bacteria.

Scientists have long known about the strength and optical qualities of silk. Silk from spiders has been used for next-generation fiber optics for computing, for example.

Omenetto said spider silk also could be used for food sensors. But extracting mass quantities of silk from silkworms is a lot easier than getting it from spiders, he said.

And besides, Omenetto added, the idea of ingesting spider webs may be even less appetizing for most consumers than eating a little silk from silkworms.

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