A team of scientists at Tufts University’s School of Engineering has designed a new class of optical sensors that can potentially detect harmful bacteria levels in everyday foods.
Imagine heading to the supermarket, buying a bag of spinach, and using an enclosed bioactive silk film sensor to detect whether that bag contained E. coli. But that’s not all. The sensor can also be eaten along with the vegetables it is evaluating.
The system combines nanoscale optics with biological readout functions and, since it uses silk proteins, is fully biocompatible and biodegradable.
Naturally, eating a sophisticated nanotechnological structure could raise some public skepticism.
“The best way I would address that concern is to say that the materials we’re using are already FDA approved,” explained David Kaplan, professor and chair of the biomedical engineering department at Tufts. “Silk is a commodity that’s been used in the human body for a long, long time, and there is a long history of its safety and efficacy.”
Perhaps as exciting is the fact that the three biological agents used in the silk solution- a protein (hemoglobin), an enzyme (horseradish peroxidase), and an organic pH indicator- all remained active and effective when stored at room temperature. The enzymes, for example, if left unrefrigerated, would lose their effectiveness in just a few days if they were isolated from the silk solution. This suggests applicability in the consumer world and a realistic shelf life at a place like the grocery store.
“Ideally, we’d love to see this project in the market in three to five years,” said Kaplan, suggesting its readiness but adding that its availability “depends on funding,” and admitting that he is unsure when exactly the technology will be implemented.
The team also discovered a way to alter light in order to create an optical signal of the biological activity. Using silk to achieve this goal has not only made the Tufts group’s research a success, but it has also sparked interest from the Defense Department, who awarded Tufts, as well as other agencies, a research contract in 2007. The Defense Advanced Research Projects Agency (DARPA) is using these biodegradable sensors to potentially create better communications technology.
Silk has proven to be the perfect substance for the integration of the biological testers and the optical signals. The protein spun by spiders and silkworms represents the strongest and toughest natural fibers known, and the material can be patterned to generate a wide range of optical elements on the nanoscale.
Kaplan also addressed the concern of a price spike if these optical sensors were placed in supermarket products.
“The final answer to [the cost] question will have to wait, but the materials we are using are relatively modest in cost. It would obviously have some impact, but I don’t expect it to have a large one.”