Non-invasive paper-based microfluidic device for ultra-low detection of urea through enzyme catalysis.

Vignesh Suresh,Karen S L Chong,Ong Qunya,Bera Lakshmi Kanta,Lee Yeong Yuh

doi:10.1098/rsos.171980

Vignesh Suresh, Karen S L Chong + Show 3 more

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https://doi.org/10.1098/rsos.171980

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Abstract

This work describes the design, fabrication and characterization of a paper-based microfluidic device for ultra-low detection of urea through enzyme catalysis. The microfluidic system comprises an entry port, a fluidic channel, a reaction zone and two electrodes (contacts). Wax printing was used to create fluidic channels on the surface of a chromatography paper. Pre-conceptualized designs of the fluidic channel are wax-printed on the paper substrate while the electrodes are screen-printed. The paper printed with wax is heated to cause the wax reflow along the thickness of the paper that selectively creates hydrophilic and hydrophobic zones inside the paper. Urease immobilized in the reaction zone catalyses urea into releasing ions and, thereby, generating a current flow between the electrodes. A measure of current with respect to time at a fixed potential enables the detection of urea. The methodology enabled urea concentration down to 1 pM to be detected. The significance of this work lies in the use of simple and inexpensive paper-based substrates to achieve detection of ultra-low concentrations of analytes such as urea. The process is non-invasive and employs a less cumbersome two-electrode assembly.

Highlights

Recent advances in microfluidics present different material substrates such as polymers, paper and overhead transparency sheets that enable controlled flow of fluid through micro-channels and, are not limited to device channels conventionally made using polydimethylsiloxane (PDMS) [1,2,3]
Samples containing urea were injected into the entry port and the fluid flowed through the channel via capillary action, before reaching the reaction zone, which was preloaded with urease
As long as the fluid transported by capillary action continued to flow through the hydrophilic channels, the contact established with the electrodes captured the minuscule change in conductivity

Summary

Introduction

Recent advances in microfluidics present different material substrates such as polymers, paper and overhead transparency sheets that enable controlled flow of fluid through micro-channels and, are not limited to device channels conventionally made using polydimethylsiloxane (PDMS) [1,2,3]. Among the materials to fabricate microfluidic substrates, plastics and papers are the most promising choices for point-of-care devices that need to be in contact with bodily fluids such as urine, serum and blood owing to their biocompatibility, flexibility and ease of handling [11,12,13]. Paperbased microfluidic devices have emerged as a new class of point-of-care diagnostic devices that are biocompatible, inexpensive, flexible, easy to fabricate and dispose [14,15,16,17,18]

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