Spring 2012

Infection detection

Sensors will help keep food supply safe

Feature Image
Omowunmi Sadik holds a version of the sensor device being developed for use in testing farm produce in the fields.

Last year nearly 150 Americans in 28 states contracted listeriosis, a bacterial infection, after consuming contaminated cantaloupes shipped from a farm in Colorado. Thirty died.

It was one of the worst cases of food-borne illness in the United States since the Centers for Disease Control (CDC) began tracking such outbreaks in the 1970s. But it was hardly unique. The CDC estimates that 48 million Americans — one in six — contract a food-borne illness every year. Nearly 130,000 of them end up in the hospital. At least 3,000 die.

No surprise that public health officials share an interest in the development of tools to help prevent such infections. And they’re about to get a new one.

Last fall, while the listeriosis outbreak was dominating national news, CapWave Sensors Inc., a California-based company, received notice of a $65,700 supplemental grant from the National Science Foundation (NSF) awarded to Phasiks Inc. to help fund research on a thermal control unit vital to CapWave’s portable biosensor immunoassay device, which has the potential to revolutionize the way food is tested for pathogens. The collaboration between the two companies is the first of several joint ventures planned by CapWave to speed product development for its biomedical testing devices.

CapWave Sensors is a subsidiary of SUTIMCo International Inc., a holding company that launches businesses built around new technologies developed at world-class universities. And it was at precisely such an institution that the new device was invented.


The foundation of the new tester was technology pioneered by Omowunmi “Wunmi” Sadik, professor of chemistry at Binghamton University and director of the University’s Center for Advanced Sensors and Environmental Systems (CASE). The device employs micro-biosensors, which are at the heart of Sadik’s research.

Modern biosensors and chemical sensors are analytical tools used to detect a wide range of biological and chemical elements. They are technological descendents of earlier tools like the blood-glucose biosensor, which employs an enzyme called glucose oxidase to essentially “digest” blood, breaking it down into constituent components so that the concentration of glucose can be measured.

In laboratories like Sadik’s, biosensors have become increasingly sophisticated in recent years. Think of them as tenacious bloodhounds on the trail of bugs like Listeria monocytogenes, the opportunistic strain of Listerium bacteria that causes listeriosis, preying especially on the most vulnerable — babies, pregnant women, the elderly, anyone with a weakened immune system who has the misfortune to consume infected food. Depending on how Sadik’s sensors are configured, they can detect all kinds of organic and inorganic matter. And they don’t need much of a “scent.”

The sensors rely on capillaries, tiny glass conduits in which the actual testing takes place. Sadik refined the capacity of those capillaries to test for small amounts of toxins while she was a visiting research fellow at the Naval Research Laboratory in Washington, D.C., from 2002 to 2004. She was looking for ways to detect Staphylococcal enterotoxin B, a toxic protein that attacks the central nervous system. Lethal in tiny amounts, it represented a threat, especially in the hands of a terrorist.

The new CapWave device is so sensitive that it can detect a sample as small as a tenth of a pictogram (a trillionth of a gram) in a thousandth of a liter of liquid. It’s quick, too. “Right now,” says Ed Ellsworth, vice president of business development at CapWave, “the standard for testing a food sample is 12 to 24 hours. We expect the new tester to trim that by eight to 12 hours.” He hopes the device will be on the market within a year.

The collaboration with Phasiks, a developer of thermal-management and fluid-control technologies, will “eliminate the need for moving parts to transfer the chemicals in the tester’s cartridge,” Ellsworth explains. “That will dramatically increase its reliability.” Simplified through years of design modifications, the tester seems poised for success. It’s small and portable and easy to use, requiring only minimal training.

It’s remarkably adaptable as well. Initially the device will offer tests for Listeria and three other common microbial culprits that cause food poisoning — E. coli, Salmonella and Campylobacter. But, Ellsworth says, “We envision a cartridge that will eventually hold up to 12 capillaries,” the tiny tubes in which the actual testing takes place.

Path to the future

“This is exciting work,” says Sadik, who earned her bachelor’s and master’s degrees in chemistry at the University of Lagos in her native Nigeria and then pursued her doctorate at the University of Wollongong in New South Wales, Australia, in the early 1990s. “The capillaries are not only highly sensitive, but they are also highly versatile. They can be used for early cancer testing, for instance, and homeland security. The possibilities are limited mostly by imagination.”

Sadik first began working with sensors in Australia. While the first devices were developed in the mid-20th century, they were primitive by today’s standards. In fact, the technology was still in its infancy when she arrived in Wollongong. She quickly discovered it was a field of research that captivated her wide-ranging imagination. By the time she had earned her PhD, her work on sensor design had resulted in two patents.

Besides the fellowship at the Naval Research Laboratory, she also has held appointments at Cornell and Harvard universities. Such opportunities reflect the esteem in which her work is held by her peers. From the moment she arrived at Binghamton, she has played an important role in defining the University as an innovator in cutting-edge applications of chemistry. In addition to chemical- and biosensors, her broad research interests include the synthesis of cross-selective arrays of polymers and the fabrication of new devices such as polymer membranes capable of conducting electricity, novel plating techniques used in the fabrication of electronics packaging, pattern recognition and machine learning, and bioelectrochemistry.

This year she was named a fellow of the prestigious American Institute for Medical and Biological Engineering, an honor accorded a scant 2 percent of professionals working in the field.

“Discovery and learning are intricately connected,” she says. “I believe that chemistry must be relevant to life. It’s the inspiration for my research and my teaching.” 

In her eclectic laboratory she heads a research group of graduate students, postdoctoral researchers and visiting scholars whose interests embrace not only sensors, but also environmental, electrochemical and materials chemistry. The result is a creative hive in which ideas from several disparate projects are likely to inform progress in the other projects, as well as in the classes — both graduate and undergraduate — that Sadik teaches.

“Dr. Sadik is an exceptional professor,” says Naumih Noah, one of the doctoral candidates who helped Sadik develop the sensor. “She is very concerned about what all of her students are working on. We have regular one-on-one meetings, and she pays close attention to the direction of our research. She offers insights and challenges us to think about our work in new ways. She teaches by example.”

“I try to inspire all of my students and encourage them to contemplate the relevance of chemistry to their lives,” Sadik says. “We learn by solving real problems and making the world a better place in the process. Applications are the path to the future.”