Janus electrochemistry: Simultaneous electrochemical detection at multiple working conditions in a paper-based analytical device

Abstract

The simultaneous detection of multiple analytes from a single sample is a critical tool for the analysis of real world samples. However, this is challenging to accomplish in the field by current electroanalytical techniques, where tuning assay conditions towards a target analyte often results in poor selectivity and sensitivity for other species in the mixture. In this work, an electrochemical paper-based analytical device (ePAD) capable of performing simultaneous electrochemical experiments in different solution conditions on a single sample was developed for the first time. We refer to the system as a Janus-ePAD after the two-faced Greek god because of the ability of the device to perform electrochemistry on the same sample under differing solution conditions at the same time with a single potentiostat. In a Janus-ePAD, a sample wicks down two channels from a single inlet towards two discreet reagent zones that adjust solution conditions, such as pH, before flow termination in two electrochemical detection zones. These zones feature independent working electrodes and shared reference and counter electrodes, facilitating simultaneous detection of multiple species at each species' optimal solution condition. The device utility and applicability are demonstrated through the simultaneous detection of two biologically relevant species (norepinephrine and serotonin) and a common enzymatic assay product (p-aminophenol) at two different solution pH conditions. Janus-ePADs show great promise as an inexpensive and broadly applicable platform which can reduce the complexity and/or number of steps required in *

Development of a Pencil Drawn Paper‐based Analytical Device to Detect Lysergic Acid Diethylamide (LSD)*†

“…Most of these electrodes use ceramic or polymers as substrate, even for a wearable device (1)(2)(3)10,11). Due to environmental concerns, the use of paper substrate for these electrodes is attracting more researchers, as it is a biodegradable material (5,(12)(13)(14)(15).…”

Recent Advances in Microfluidic Paper-Based Analytical Devices toward High-Throughput Screening

“…The Janus e-μPAD was utilized for the simultaneous detection of multiple neurotransmitters with the capability for in situ pH control and optimized electrochemical experiments. This device showed great potential as a low-cost platform that could provide multiplexed analysis by using simple steps ( Figure 8 ) [ 139 ]. The Janus e-μPAD was also applied for high-throughput determination of the concentrations of different metals, including Cd, Pb, Cu, Fe, and Ni metals, from a single sample of airborne particulate matter, and the results were in agreement with those obtained using a traditional method (95% confidence) [ 140 ].…”

“… Schematic representation of a Janus e-μPAD: ( a ) design of the Janus e-μPAD and ( b ) operation for multiplexed detection with in situ pH adjustment. Reproduced with permission from the authors of [ 139 ]. Copyright 2019, Elsevier B.V. …”

Recent applications of paper‐based point‐of‐care devices for biomarker detection

“…Examples on novel designs and fabrication techniques include a flow controllable 3D‐PAD fabricated by 3D‐printing technology using digital light processing stereolithography for the detection of glucose and albumin , a vacuum filtration assisted wax printing‐PAD chemiresistive biosensor using single‐walled carbon nanotubes as a low cost POC detection of human serum albumin , and a filtration‐assisted screen printing‐PAD for glucose detection . A Janus (two‐faced Greek god)‐electrochemical paper device was proposed for simultaneous analysis of norepinephrine, serotonin, and p‐aminophenol in a sample . The design enabled the use of a single potentiostat for different sample solutions in two electrochemical zones.…”