This article describes a 3D microfluidic paper-based analytical device that can be used to conduct an enzymelinked 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 cutoffs 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.
The field results of our collaboration with the University of Nairobi have been published in the “International Journal of Veterinary Science” (IJVS).
Kelly Wilkister Nakami used DfA's device in the field to collect her results. Profs. Tsuma (University of Nairobi) and Odipo (University of Eldoret) also contributed to the work, with the assistance of our scientists Kendall Milkey, Michelle Wong and Matt Dickerson.
The project was generously funded by the Gates Foundation, in collaboration with PATH.
Link to the paper (Open Access):
Nakami WN, Tsuma VT, Milkey K, Dickerson M, Wong M, Mutembei HM, Muthee JK, Odipo O and Ngetich W, 2017. Lateral flow immunoassay for whole blood progesterone detection as a tool for assessment of reproductive status in cattle. Inter J Vet Sci, 6(1): 19-25. www.ijvets.com (©2017 IJVS. All rights reserved)
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