It may look humble, but that tiny piece of filter paper pictured above is a portable diagnostics laboratory condensed into a pocket-sized strip. The technology is currently being developed by scientists at Harvard’s Wyss Institute as a cheap and easy way to detect a wide range of infections or medically important molecules such as glucose. Although it’s not ready to be used in the field yet, the researchers have demonstrated that the test can successfully pick up two different strains of Ebola virus.
The technology works by embedding synthetic gene circuits onto pieces of litmus paper and freeze drying them so that they can be stored for prolonged periods at room temperature. To make the circuit come to life, it simply needs to be dipped into water. If a particular pathogen or molecule is present in the water, the tiny dots on the paper change color.
The networks are designed in a way that when a particular target, such as a piece of viral or bacterial genetic material, binds to one of the genes, the circuit becomes switched on. This then triggers genes downstream in the circuit to start producing colorful proteins, such as the fluorescent molecule that makes jellyfish glow. By mixing up the combination of genes in the circuit, researchers can detect a wide range of target molecules.
The scientists put their mini laboratory to the test by exposing it to two different strains of Ebola virus, and sure enough it was able to detect them. It was so efficient that a color change was observed in just 30 minutes, which is roughly how long more traditional antibody tests take to produce a result. They also designed another test that successfully picked up genetic material from antibiotic-resistant bacteria, which could be useful for hospitals.
Impressively, the tests cost just $21 to produce, which is significantly cheaper than diagnostic machines which often come with a hefty price tag. If the researchers can produce the gene sequences themselves, rather than paying other companies to synthesize them, then the cost can be brought down even more.
Because the test is so small, it could easily be transported to remote places that have little or no access to clinical facilities, improving diagnosis rates. This would be particularly useful for disease outbreaks in developing countries, such as the current Ebola crisis. The test is also versatile and could be used on a variety of different bodily fluids, such as saliva or blood. However, the technology needs to be improved before it can be brought into practice as currently it is not sensitive enough to detect very small amounts of target molecules. The team also needs to make sure that the number of false positive results given by the test is low enough to meet specified diagnostic standards.