A low-cost hand-held device engineered by researchers from Northwestern University and Stemloop Inc. (Evanston, Illinois) gauges the quality and safety of drinking water in minutes. The portable analyzer extends previous efforts to develop the RNA output sensors activated by ligand induction (ROSALIND) system, showcased in the video above, which could detect 17 different contaminants in a single drop of water.

When the test detected a contaminant concentration exceeding U.S. Environmental Protection Agency standards is detected, this version glowed green. The analytical system is based on cell-free synthetic biology, wherein DNA, proteins and other components of molecular machinery are removed from cells and reprogrammed to perform new tasks. In this application, the reworked components are likened to molecular taste buds.

The newer ROSALIND 2.0 iteration empowers the biosensor with a molecular brain based on genetic circuits that sense whether or not contaminants are present and detect contamination levels. The reprogrammed biosensor circuits are freeze-dried to ensure shelf stability and placed in test tubes. The pellets glow in the presence of a pollutant when a drop of water is added to the tube and prompts the genetic circuitry to function as an analog-to-digital converter. The result is a series of binary outputs that encode the concentration range of the target molecule.

The biosensor confirms contamination in a water sample and indicates concentration levels. Source: Julius Lucks/Northwestern University

In addition to generating positive or negative results, ROSALIND 2.0 successfully detected concentration levels of zinc, an antibiotic and an industrial metabolite during laboratory trials.

The device described in Nature Chemical Biology could form the basis of an inexpensive hand-held biosensor for use by anyone to quickly and accurately test potable water sources.