Direct quantitative screening of influenza A virus without DNA amplification by single-particle dual-mode total internal reflection scattering.

ABSTRACT

Quantitative screening of influenza A (H7N9) virus without DNA amplification was performed based on single-particle dual-mode total internal reflection scattering (SD-TIRS) with a transmission grating (TG). A gold nanopad was utilized as a substrate for the hybridization of probe DNA molecules with the TIRS nanotag (silver-nanoparticle). The TG effectively isolated the scattering signals in first-order spectral images (n=+1) of the nanotag from that of the substrate, providing excellent enhancement of signal-to-noise and selectivity. By using single-DNA molecule/TIRS nanotag hybridization, target DNA molecules of H7N9 were detected down to 74 zM, which is at least 100,000 times lower than the current detection limit of 9.4fM. By simply modifying the design of the probe DNA molecules, this technique can be used to directly screen other viral DNAs in various human biological samples at the single-molecule level without target amplification.