Last year, we were inspired by “Toehold switches: de-novo-designed regulators of gene expression” (Green, Silver, et al.) to create a paper-based gene network featuring an aptamer-based genetic switch that was capable of producing a colorimetric output in the presence of a chosen target protein. We iterated through two toehold-based switch designs based but were not able to detect our target protein at in vitro levels.

This year, we have completely redesigned our genetic switch in an attempt to further improve its specificity and effectiveness. Our new design features two unique aptamers that bind to the target protein and are designed for proximity-dependent ligation similarly to those outlined in “Protein detection using proximity-dependent DNA ligation assays” (Fredriksson, Gullberg, et al.). Once ligated, the tails of the two aptamers express the alpha fragment of lacZ, which enables free floating lacZ to metabolize Xgal and create a blue colorimetric output.

While we are testing this with Thrombin as the target protein, we believe that by changing the aptamers, this system could be used to detect any target you choose, opening the doors for a wide range of diagnostic uses. It is our goal to use the technology outlined in “Paper-based synthetic gene networks” (Pardee, Green, et al.) to mount our dehydrated synthetic gene network onto paper test strips that could be cheaply and effectively used as diagnostic devices similar to those discussed in “Rapid, Low-Cost Detection of Zika Virus Using Programmable Biomolecular Components” (Pardee, Green, et al). This technology would particularly benefit the fight against tuberculosis, as cheap and accurate diagnosis is the largest hurdle to treatment of the disease in much of the world.