Cheap, fast 'paper strip' test for Ebola, other infections, steps closer

Date: Oct-27-2014 Researchers working in the field of synthetic biology are bringing

together science, engineering and computing to understand and copy the workings

of biological life in new ways to achieve remarkable breakthroughs. Two studies

published in Cell show how advances in this field could one day lead to

cheap, reliable diagnostics for diseases like Ebola - tests that could be done

rapidly in the field using only drops of blood or saliva on strips of paper

embedded with synthetic biology circuits.

Two new studies demonstrate how advances in engineering and computing could eventually yield cheap diagnostics that can be performed quickly in the field for diseases such as Ebola.

In the first study, the scientists, from Harvard University's Wyss Institute

for Biological Inspired Engineering in Boston, MA, describe how they brought

lab-testing ability to pocket-sized slips of paper by embedding them with

synthetic gene networks. They also explain how they created various diagnostics,

"including glucose sensors and strain-specific Ebola virus sensors."

Until recently, progress in synthetic biology has been hampered because

scientists have only been able to develop synthetic mechanisms within living

cells.

However, the study describes how the Wyss team took a giant leap by creating a

system where they can design synthetic versions of biological mechanisms outside

of cells.

Paper-based, synthetic biology tools can be freeze dried and stored

Dr. Keith Pardee, lead author of the first paper and staff scientist at Wyss,

explains:

"We've harnessed the genetic machinery of cells and embedded them in the fiber

matrix of paper, which can then be freeze dried for storage and transport - we

can now take synthetic biology out of the lab and use it anywhere to better

understand our health and the environment."

Dr. Pardee and colleagues have built a range of paper-based diagnostics and

biosensors. These incorporate proteins that fluoresce and change color to show

they are working.

Once freeze-dried, the paper-based tools can be stored for up to a year; they

are activated by adding water.

The tools can also be used in the lab to save time and cost compared with

conventional methods that use living cells and tissue.

"Where it would normally take 2 or 3 days to validate a tool inside of

a living cell, this can be done using a synthetic biology paper-based platform in

as little as 90 minutes," says Dr. Pardee.

In their study, he and his colleagues describe how they tested a range of

paper-based synthetic biology tools. They activated genetic switches, quickly

designed and produced complex gene circuits, and programmed diagnostics that can

test for antibiotic-resistant bacteria and strain-specific Ebola virus.

'Toehold switch' used to create Ebola sensor

The Wyss team created the Ebola sensor with the help of a "toehold switch," a

new system for controlling gene expression that is very flexible and highly

programmable. This is the subject of the second study.

The toehold switch was initially designed to work inside living cells, but the

team managed to transfer its function to the freeze-dried paper method.

The toehold switch can be programmed to switch on the production of a specific

protein after precisely detecting an RNA signature of virtually any kind. RNA

signatures are sequences of genetic code that can be used to identify a broad

range of infectious agents, including bacteria, viruses, yeast and

parasites.

The team says it is also possible to link several toehold switches together,

creating a complex circuit that can be programmed to carry out a series of steps,

such as detect a pathogen and then deliver an appropriate therapy.

The video below explains how the toehold switch works:

Peng Yin, associate professor in the Department of Systems Biology at Harvard

Medical School and Wyss Core Faculty Member, is senior author of the second

paper. He explains that conventional synthetic biology just takes existing

biological parts and rewires them to achieve a new purpose. But this complicates

accuracy and functionality.

On the other hand, while the toehold switch is inspired by nature, it is

entirely re-designed from scratch, he adds, noting that the study describes how

they produced a device that "is a truly 'synthetic' gene regulator with 40-fold

better ability to control gene expression than conventional regulators."

In September 2014, Medical News Today learned how researchers are working on a way to fight drug-resistant pathogens with their own "gene-editing" system. In a paper published in Nature Biotechnology, the team describes how they used CRISPR - a gene-editing system that bacteria use to defend against attack by viruses - to target the superbugs themselves.

Written by Catharine Paddock PhD

Not to be reproduced without permission.

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.