Electrocatalytic Palladium Nanoclusters as Versatile Indicators of Bioassays: Rapid Electroanalytical Detection of SARS‐CoV‐2 by Reverse Transcription Loop‐Mediated Isothermal Amplification

Abstract

Quantitative polymerase chain reaction (qPCR) is considered the gold standard for pathogen detection. However, improvement is still required, especially regarding the possibilities of decentralization. Apart from other reasons, infectious diseases demand on‐site analysis to avoid pathogen spreading and increase treatment efficacy. In this paper, the detection of SARS‐CoV‐2 is carried out by reverse transcription loop‐mediated isothermal amplification, which has the advantage of requiring simple equipment, easily adaptable to decentralized analysis. It is proposed, for the first time, the use of palladium nanoclusters (PdNCs) as indicators of the amplification reaction at end point. The pH of the medium decreases during the reaction and, in turn, a variation in the catalytic activity of PdNCs on the oxygen reduction reaction (ORR) can be electrochemically observed. For the detection, flexible and small‐size screen‐printed electrodes can be premodified with PdNCs, which together with the use of a simple and small electrochemical equipment would greatly facilitates their integration in field‐deployable devices. This would allow a faster detection of SARS‐CoV‐2 as well as of other future microbial threats after an easy adaptation.

Single‐Response Duplexing of Electrochemical Label‐Free Biosensor from the Same Tag

“…[ 37 ] Powerful alternatives to improve the sensitivity of our vertical chips are the use of metal‐organic frameworks (MOFs), [ 100 ] the electrodeposition of nanostructured microelectrode on recessed WE, [ 37,101,102 ] reagentless molecular pendulum‐based detection, [ 10,35,103 ] the electrochemical nano‐roughening of Au film, [ 18 ] the anisotropic etching to create nanoporous Au films, [ 15 ] and the use of electrocatalytic palladium nanoclusters. [ 19 ] Such methods are particularly promising as they can entail antifouling capacity against untreated biological fluids, which are expected to inhibit the use of the MECs by passivating the recessed WEs, as demonstrated here with FBS.…”

“…[6][7][8] To fulfill the REASSURED criteria, the diagnostic devices must also offer a reasonable trade-off between i) the performance of laboratory-based standard techniques (i.e., polymerase chain reaction and enzyme-linked immunosorbent assay) and ii) the ease of operation, high throughput, and portability of rapid testing (e.g., lateral flow assays). Although many electrochemical nanobiosensors have been devised as an effective solution to cope with POC analysis-related issues, [9][10][11][12][13][14][15][16][17][18][19] this platform has not yet addressed the market needs or reached wide utilization in clinical practice. [6,20,21] Key challenges facing the development of diagnostic devices across all nine technology readiness levels (TRLs) are tightly tied to the device lifespan, prototyping, throughput (the ability to analyze hundreds of samples in a short period), and bodily fluid properties that hinder accuracy by implying fouling and cross-reactivity issues.…”