Multifunctional Nanoparticle Platform for Surface Accumulative Nucleic Acid Amplification and Rapid Electrochemical Detection: An Application to Pathogenic Coronavirus

Of various molecular diagnostic assays, the real-time reverse transcription polymerase chain reaction is considered the gold standard for infection diagnosis, despite critical drawbacks that limit rapid detection and accessibility. To confront these issues, several nanoparticle-based molecular detection methods have been developed to a great extent, but still possess several challenges. In this study, a novel nucleic acid amplification method termed nanoparticle-based surface localized amplification (nSLAM) is paired with electrochemical detection (ECD) to develop a nucleic acid biosensor platform that overcomes these limitations. The system uses primer-functionalized Fe₃O₄-Au core-shell nanoparticles for nucleic acid amplification, which promotes the production of amplicons that accumulate on the nanoparticle surfaces, inducing significantly amplified currents during ECD that identify the presence of target genetic material. The platform, applying to the COVID-19 model, demonstrates an exceptional sensitivity of ∼1 copy/μL for 35 cycles of amplification, enabling the reduction of amplification cycles to 4 cycles (∼7 min runtime) using 1 fM complementary DNA. The nSLAM acts as an accelerator that actively promotes and participates in the nucleic acid amplification process through direct polymerization and binding of amplicons on the nanoparticle surfaces. This ultrasensitive fast-response system is a promising method for detecting emerging pathogens like the coronavirus and can be extended to detect a wider variety of biomolecules.