Tuberculosis (TB) is one of the leading causes of death worldwide according the World Health Organization (source: http://www.who.int/gho/tb/en/), despite the availability of treatments which are often completely paid for by the government. Even so, 1.4 million died from TB in 2014 (source: http://www.who.int/mediacentre/factsheets/fs104/en/). The problem is patients with TB are not being diagnosed until it is too late. Current methods are either cheap but unreliable, or are accurate but prohibitively expensive, or require access to advanced medical facilities.

Our team decided to tackle this problem by developing a genetic switch that could detect TB biomarkers that did not require lab equipment or labor necessary for protein detection assays such as ELIZAs. By incorporating our genetic switch in a paper strip that could be easily self administered with no specialized equipment, we would be able to provide a low-cost detection system to regions where TB is most prevalent, namely Africa and sub-continental Asia, where access to labs and lab equipment is difficult.

Our switch design this year relies on two unique aptamers that both bind to the target protein. These two aptamers have been designed with sequences that enable the free-floating tails to ligate with each other through proximity dependent ligation. When the aptamers bind to the target protein and ligate together, they allow expression of the lacZ alpha fragment, which enables free floating lacZ to convert Xgal to 5,5'-dibromo-4,4'-dichloro-indigo and cause a blue colorimetric output.

When this system is freeze dried onto the paper test strip it can last up to a year with no refrigeration (Pardee, Green, et al.). To use, a consumer need only dehydrate with a sputum sample and watch for the color to change.

For our proof of concept we utilized thrombin due to its availability and it's through characterization. However, we expect converting the target protein to a TB biomarker such as CFP-10, which is highlighted in "IFN-γ/TNF-α ratio in response to immuno proteomically identified human T-cell antigens of Mycobacterium tuberculosis - The most suitable surrogate biomarker for latent TB infection." (Prabhavathi et al.) would not be very difficult.