Development of a Fully Automated Device for Applying Aqueous Two-Phase Systems Onto the Lateral-Flow Immunoassay for Improved Detection

Two major water pollutant classes are microorganisms and organic chemicals. Although laboratory-based assays effectively detect water contaminants, they are costly, require trained personnel, and have a long time to result. This limits the continuous monitoring required for preventing widespread use of contaminated water. An alternative is the lateral-flow immunoassay (LFA) which is rapid, inexpensive, and easy to use. However, LFAs can yield false negatives when the target is present at low concentrations, such as with water contaminants. Aqueous two-phase systems (ATPSs) can preconcentrate targets into one phase before application to the LFA, and the fold-concentration depends on the volume ratio (VR) between the top and bottom phases. Since a user typically adds a set volume to LFAs, the limit of detection (LOD) of the assay can vary as the VR, and thus the preconcentration, can vary depending on the water samples’ salt content. To address this, we recently applied the entire target-containing phase to an LFA and demonstrated that the same LOD can be achieved, irrespective of the VR. This method unfortunately required multiple user steps. To enable this approach to be used at the point of need (PON), we describe the development of the first fully battery-operated and automated device for detecting the ATPS interface regardless of the VR, extracting the entire target-containing phase, and dispensing it onto an LFA. This device yields a 10-fold improvement in the LOD for both Escherichia coli and atrazine, providing results within 30 min and offering a solution for monitoring water quality.