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Flavin-adenine dinucleotide (FAD) dependent glucose dehydrogenase (GDH) is a thermostable, oxygen insensitive redox enzyme used in bioelectrochemical applications. The FAD cofactor of the enzyme is buried within the proteinaceous matrix of the enzyme, which makes it almost unreachable for a direct communication with an electrode. In this study, FAD dependent glucose dehydrogenase was fused to a natural minimal cytochrome domain in its c-terminus to achieve direct electron transfer. We introduce a fusion enzyme that can communicate with an electrode directly, without the use of a mediator molecule. The new fusion enzyme, with its direct electron transfer abilities displays superior activity to that of the native enzyme, with a k that is ca. 3 times higher than that of the native enzyme, a k/K that is more than 3 times higher than that of GDH and 5 to 7 times higher catalytic currents with an onset potential of ca. (-) 0.15 V vs Ag/AgCl, affording higher glucose sensing selectivity. Taking these parameters into consideration, the fusion enzyme presented can serve as a good candidate for blood glucose monitoring and for other glucose based bioelectrochemical systems.

Pandemics require a fast and immediate response to contain potential infectious carriers. In the recent 2020 Covid-19 worldwide pandemic, authorities all around the world have failed to identify potential carriers and contain it on time. Hence, a rapid and very sensitive testing method is required. Current diagnostic tools, reverse transcription PCR (RT-PCR) and real-time PCR (qPCR), have its pitfalls for quick pandemic containment such as the requirement for specialized professionals and instrumentation. Versatile electrochemical DNA/RNA sensors are a promising technological alternative for PCR based diagnosis. In an electrochemical DNA sensor, a nucleic acid hybridization event is converted into a quantifiable electrochemical signal. A critical challenge of electrochemical DNA sensors is sensitive detection of a low copy number of DNA/RNA in samples such as is the case for early onset of a disease. Signal amplification approaches are an important tool to overcome this sensitivity issue. In this review, the authors discuss the most recent signal amplification strategies employed in the electrochemical DNA/RNA diagnosis of pathogens.

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