Evaporative concentration on a paper-based device to concentrate analytes in a biological fluid.

We report the first demonstration of using heat on a paper device to rapidly concentrate a clinically relevant analyte of interest from a biological fluid. Our technology relies on the application of localized heat to a paper strip to evaporate off hundreds of microliters of liquid to concentrate the target analyte. This method can be used to enrich for a target analyte that is present at low concentrations within a biological fluid to enhance the sensitivity of downstream detection methods. We demonstrate our method by concentrating the tuberculosis-specific glycolipid, lipoarabinomannan (LAM), a promising urinary biomarker for the detection and diagnosis of tuberculosis. We show that the heat does not compromise the subsequent immunodetectability of LAM, and in 20 min, the tuberculosis biomarker was concentrated by nearly 20-fold in simulated urine. Our method requires only 500 mW of power, and sample flow is self-driven via capillary action. As such, our technology can be readily integrated into portable, battery-powered, instrument-free diagnostic devices intended for use in low-resource settings.