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Tsaloglou, Maria-Nefeli

This article describes a 3D microfluidic paper-based analytical device that can be used to conduct an enzyme-linked immunosorbent assay (ELISA). The device comprises two parts: a sliding strip (which contains the active sensing area) and a structure surrounding the sliding strip (which holds stored reagents—buffers, antibodies, and enzymatic substrate—and distributes fluid). Running an ELISA involves adding sample (e.g. blood) and water, moving the sliding strip at scheduled times, and analyzing the resulting color in the sensing area visually or using a flatbed scanner. We demonstrate that this device can be used to detect C-reactive protein (CRP)—a biomarker for neonatal sepsis, pelvic inflammatory disease, and inflammatory bowel diseases—at a concentration range of 1-100 ng/mL in 1000-fold diluted blood (1-100 µg/mL in undiluted blood). The accuracy of the device (as characterized by the area under the receiver operator characteristics curve) is 89% and 83% for cut-offs of 10 ng/mL (for neonatal sepsis and pelvic inflammatory disease) and 30 ng/mL (for inflammatory bowel diseases) CRP in 1000-fold diluted blood respectively. In resource limited settings, the device can be used as a part of a kit (containing the device, a fixed-volume capillary, a pre-filled tube, a syringe, and a dropper); this kit would cost ~$0.50 when produced in large scale (>100,000 devices/week). This kit has the technical characteristics to be employed as a pre-screening tool, when combined with other data such as patient history and clinical signs.

This paper describes the design and characterization of an open-source “universal wireless electrochemical detector” (UWED). This detector interfaces with a smartphone (or a tablet) using “Bluetooth Low Energy” protocol; the smartphone provides (i) a user interface for receiving the experimental parameters from the user and visualizing the result in real time, and (ii) a proxy for storing, processing, and transmitting the data and experimental protocols. This approach simplifies the design, and decreases both the size and the cost of the hardware; it also makes the UWED adaptable to different types of analyses by simple modification of the software. The UWED can perform the most common electroanalytical techniques of potentiometry, chronoamperometry, cyclic voltammetry, and square wave voltammetry, with results closely comparable to benchtop commercial potentiostats. Although the operating ranges of electrical current and voltage of the UWED (±1.5 V, ±180 μA) are more limited than most benchtop commercial potentiostats, its functional range is sufficient for most electrochemical analyses in aqueous solutions. Because the UWED is simple, small in size, assembled from inexpensive components, and completely wireless, it offers new opportunities for the development of affordable diagnostics, sensors, and wearable devices.