board (PCB) electrodes for wastewater monitoring using portable PCR instruments, such as miniPCR®, without the requirement for qPCR reagents.
PCB electrodes are attractive candidates for low-cost and sensitive DNA
biosensors of relevance in a pandemic such as COVID-19, and facilitate
the opportunity to map disease spread in Low-Middle Income Countries
(LMICs) through monitoring of environmental samples such as wastewater.
The biosensor reported in this work is capable of detecting PCR amplicons
through the intercalation of methylene blue (MB) with DNA, which increases
the voltammogram peak current at the redox potential of MB. We describe
how these changes are likely to result from the adsorption of MB-DNA complex on the electrode surface. The electrodes are reusable, easy to clean, do
not undergo any surface modification and represent a cost-effective solution
with long shelf-life. We also explore the impact that MB concentration and
DNA length have upon our biosensor performance and provide insights useful to other investigators in the field. The sensor reported here is capable
of detecting SARS-CoV-2 nucleocapsid gene amplicons at concentrations as
low as 10 pg=µl (approximately 1:7 fM) and can detect nucleotides amplified
after 10 PCR cycles. Furthermore, using the PCB electrode and approaches
described here, SARS-CoV-2 amplicons were detected in simulated wastewater sample, by spiking wastewater collected from a sewage treatment plant
in Mumbai, India with SARS-CoV-2 RNA.
- methylene blue
- DNA biosensor
- PCB electrode
- wastewater epidemiology