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

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.

Automated summary

In this paper, the detection of SARS-CoV-2 is carried out using reverse transcription loop-mediated isothermal amplification, and palladium nanoclusters are used as indicators of the amplification reaction at end point. The catalytic activity of palladium nanoclusters on the oxygen reduction reaction can be electrochemically observed due to the decrease in pH during the reaction. By premodifying flexible and small-size screen-printed electrodes with palladium nanoclusters, and using a simple and small electrochemical equipment, their integration into field-deployable devices is greatly facilitated, enabling faster detection of SARS-CoV-2 as well as future microbial threats after easy adaptation.