The avian influenza A H7N9 virus is known as one of the newly discovered highly pathogenic avian influenzas with serious threat to public health and the poultry industry. In this work, an ultrasensitive surface-enhanced Raman scattering (SERS) determination of H7N9 virus via exonuclease III-assisted cycling amplification was proposed to meet the needs of rapid, sensitive and accurate detection of H7N9-related genes. The SERS strategy aims to simultaneously determine the characteristic gene fragments of H7 and N9 by specially designing Capture, Replace, and Probe single-strand DNAs to realize exonuclease III-assisted cycling amplifications, and then integrating the cyclic amplification with SERS-active Ag nanorods array substrate to achieve an ultrasensitive SERS determination of H7N9. After characterizing the effectiveness of the sensing mechanism and further investigating the surface blocking and the dosage of exonuclease III, the optimal surface blocking was achieved by using 10 μM and 100 μM mercaptohexanol for H7 and N9 detection respectively, and the optimal Exo III concentrations for sensing H7 and N9 were 0.10 U μL-1 and 0.30 U μL-1 respectively. Under the optimal conditions, dual and specific detections of H7 and N9 gene fragments were obtained with detection linear interval from 1 fM to 100 pM and limit of detections low to 31 aM of H7 and 44 aM of N9, as well as recovery in the range of 93.8-106.2% with relative standard deviation less than 6.12%. The proposed ultrasensitive SERS strategy can provide a powerful tool for determining H7N9 virus and other avian influenza viruses.
Keywords: Avian influenza; Exonuclease III-Assisted cycling amplification; H7N9 virus; SERS.
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