Amplification‐ and Enzyme‐Free Magnetic Diagnostics Circuit for Whole‐Genome Detection of SARS‐CoV‐2 RNA

Abstract

AbstractPolymerase chain reaction (PCR) requires thermal cycling and enzymatic reactions for sequence amplification, hampering their applications in point‐of‐care (POC) settings. Magnetic bioassays based on magnetic particle spectroscopy (MPS) and magnetic nanoparticles (MNPs) are isothermal, wash‐free, and can be quantitative. Realizing them amplification‐ and enzyme‐free on a benchtop device, they will become irreplaceable for POC applications. Here we demonstrate a first‐in‐class magnetic signal amplification circuit (MAC) that enables detection of whole genome of SARS‐CoV‐2 by combining the specificity of toehold‐mediated DNA strand displacement with the magnetic response of MNPs to declustering processes. Using MAC, we detect the N gene of SARS‐CoV‐2 samples at a concentration of 104 RNA copies/μl as determined by droplet digital PCR. Further, we demonstrate that MAC can reliably distinguish between SARS‐CoV‐2 and other human coronaviruses. Being a wash‐, amplification‐ and enzyme‐free biosensing concept and working at isothermal conditions (25 °C) on a low‐cost benchtop MPS device, our MAC biosensing concept offers several indispensable features for translating nucleic acid detection to POC applications.