A bright idea: DNA glucose sensors

For people with diabetes, monitoring blood-sugar levels several times a day can be painful to the pocketbook as well as the flesh. But thanks to the work of a group of Missouri S&T students, the process may cost less in the future.

Members of the Missouri S&T chapter of iGEM — the International Genetically Engineered Machine Foundation — recently devised a synthetic biological system that uses segments of DNA embedded in bacteria to detect glucose. The students believe their development could lead to a new type of test strip for diabetics.

“We designed DNA so that bacteria that have DNA would sense a change in osmolarity due to the presence of glucose,” says Erica Shannon of Wildwood, Mo., a senior in biological sciences at Missouri S&T and former president of the campus’s iGEM chapter. Osmolarity refers to the concentration of a compound — in this case, glucose — in a solution.

For their project, the students designed genes that allow the bacteria — a non-virulent strain of E. coli — to sense the presence of the simple sugar glucose. The bacteria emit a yellow glow when glucose is present. As glucose concentrations become higher, the glow becomes brighter.

The team developed the system as part of an annual competition sponsored by iGEM, the Americas Regional Jamboree, held Oct. 8-10, 2011, in Indianapolis. S&T’s iGEM chapter received a silver medal for their effort.

The idea was part of a larger proposal put forth by Logan Sauerbrei of Lebanon, a junior in biological sciences. As a person with Type 1 diabetes, he knows firsthand the problems of managing the disease and suggested that a synthetic biological solution would be considerably less expensive than commercial test strips.

His proposal went much further, calling for a self-regulating, insulin-producing process inside the body, serving as a replacement for the pancreas. Because the larger scheme was beyond the reach of the team’s budget and knowledge, the team chose just the test strip part, Shannon said.

According to Shannon, the team’s biological system could form the basis for new, less costly processes to help people with diabetes monitor their blood-sugar levels. It would require replacing the fluorescent gene with one that would cause the bacteria to change color based on glucose levels. This in turn could lead to the development of diabetes blood-test strips that could indicate glucose levels based on various colors. For example, a test strip might turn green if glucose levels are within normal ranges, yellow if borderline and red if elevated.

“All you would have to do is put the DNA inside a bacteria and you’ve got your test strip,” says Shannon.

Bacteria-based test strips would also be less expensive to make than current chemical-based test strips, Shannon says.

“In the future, based on further research, an insulin gene could be added to this system for use in insulin pumps, where specific glucose levels trigger insulin production,” she says.

S&T’s iGEM chapter recently joined the cadre of design teams under the Student Design and Experiential Learning Center. iGEM is the first non-engineering team to be part of the center. The team is advised by Dr. David Westenberg, associate professor of biological sciences, and Dr. Katie Shannon, assistant professor of biological sciences.

By Andrew Careaga

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