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French Team Develops Synthetic Biology Diabetes Diagnostic

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NEW YORK (360Dx) – A team led by researchers from France’s Sys2diag laboratory have developed synthetic biology-based biosensors capable of detecting biomarkers in human clinical samples.

The sensors consist of synthetic protein signaling networks encased in phospholipid bilayer membranes. In a proof-of-concept study published last month in Molecular Systems Biology, the networks were able to detect diabetes-linked markers in patient urine samples.

The results suggest that the technology could enable the creation of inexpensive, highly portable, and easy to use diagnostics capable of testing for a variety of conditions, said Alexis Courbet, a post-doctoral fellow at the University of Washington and first author on the paper.

Before moving to the University of Washington, Courbet was a graduate student under Sys2diag researcher Franck Molina, senior author on the MSB paper. Molina and his colleagues have since formed a company, SkillCell, to commercialize the technology.

A key function of biological systems is to detect conditions in their environment and to react in response to those conditions. This has led researchers to look at biological molecules as potential diagnostic tools, the idea being that such molecules could be arranged in networks — much as they are in nature — to detect markers or conditions of interest and provide a diagnostic output.

And, the authors wrote, this approach has seen notable successes, with researchers building biochemical pathways capable of performing a variety of tasks and developing "synthetic cell-like microreactors containing cascaded circuits of enzymes or nucleic acids, often referred to as protocells," that "have shown recapitulation of complex behavior found in natural cells such as communication, information processing, metabolism, and reproduction."

Such efforts, however, have been difficult to scale to a useful commercial technology, the authors noted. Combining computer-aided design with microfluidic assembly techniques, they aimed to streamline the development of these protosensors with the goal of making them broadly useful tools for applications ranging from clinical diagnostics to food and environmental testing.

"We have now a way to program all kinds of different logic functions into synthetic networks," Courbet said. "It's a really systematic methods that allows us to produce any type of device with specific characteristics we [determine] at the beginning."

The goal, he added, is to offer them as a low-cost, highly convenient alternative to existing tests based on technologies like immunoassays.

"These assays are portable, they're really cheap, and they are what's called 'smart' — that is, that they can be designed to [measure] a lot of different biomarkers and you can also put a lot of decision making into them," he said. "The idea is that you could have very smart systems that you could have in the field to be used by unskilled personnel."

Such work has often used nucleic acids as sensor components, but the Sys2diag team opted for proteins, which, Courbet said, offer a higher level of functionality.

"With nucleic acids, they are very limited in terms of their inputs and outputs," he said. "Proteins [on the other hand], are incredibly functional. That's why natural systems use proteins, because they are so much better at doing all these different things."

Proteins can also operate at faster time scales than nucleic acids, Courbet said, noting that "DNA cascades can be very, very slow."

Courbet said that the systems he and his colleagues have designed thus far consist of around 10 different enzymes and 10 or so different metabolites. However, he said, in theory, much more complex systems are possible.

"You could really imagine having hundreds of different enzymes that interact" to produce diagnostic outputs, he said. Another possibility would be to have the sensor output trigger a therapeutic response — the release of a drug upon detection of certain conditions, for instance.

He added that he and his colleagues were working towards more complex constructions involving multiple sensor networks separated into different membrane-enclosed compartments and more finely tuned control of properties like the diffusion of molecules across these membranes.

In the MSB paper, the researchers developed as a proof-of-concept a set of three protosensors that could enable the differential diagnosis of the diabetes-linking complications diabetic ketoacidosis, hyperglycemia hyperosmolar state, hypoglycemia, and lactic acidosis.

Using their modeling system, they determined that three protosensors — one that processes glucose and acetone as its inputs; one processing lactate and ethanol as inputs; and one processing glucose and nitric oxide — would be needed. The three sensors used, respectively, six, five, and four biochemical components, and produced as outputs NADH, resorufin, ABTS, and DAF.

Testing these sensors in media spiked with multiple biomarkers, the researchers determined that they behaved as expected, with the observed outputs corresponding to expected output levels. They then tested one of the sensors, the glucose and acentone (GluONe) device, in urine from 72 treatment-naïve diabetes patients and 72 healthy controls, finding that the sensor was able to distinguish between the two with nearly 100 percent specificity and sensitivity.

Molina said that SkillCell planned to release its first product based on the technology, a test for insulin resistance, by the end of the year. He said one of the company's main goals was to develop more convenient versions of existing clinical tests that could be used for home monitoring or in other venues where convenience and ease of use are key.

The assays "are designed to be used outside of a laboratory," he said. "You don't need a lab, you don't need a technician, because the system provides the measurement of the markers, calculates the decision, and the provides that decision with [for instance] a simple change of color."

SkillCell is a subsidiary of the French industrial conglomerate Alcen, which, with France's National Centre for Scientific Research (CNRS), established the Sys2Diag laboratory in 2015 as a private-public partnership aimed at developing and commercializing medical diagnostics. SkillCell currently has roughly 10 employees and is funded by Alcen and the CNRS, Molina said.