A novel cascade colorimetric biosensor based on three-way junction-initiated primer exchange reaction for detection of influenza virus

A novel biosensor based on a three-way junction (3WJ)-induced primer exchange reaction was developed for detection of the H1N1 virus. The target H1N1 RNA induced formation of a 3WJ. The subsequent assembly of two DNA probes triggered amplification of downstream strand displacement to copiously generate signal primers to initiate primer exchange reaction to form a long single-stranded sequence containing multiple G quadruplet repeats. Abundant G-quadruplex/hemin was formed in the presence of hemin, thus catalyzing a colorimetric reaction. The detection limit of the colorimetric biosensor was 34.32 fM with a linear relationship from 100 pM to 1 mu M. By simply changing the sequence of the two probes based on the target-specific sequence, the biosensor can be easily extended to detect other viral RNA. The proposed biosensor successfully detected H1N1 RNA as a sensitive, portable, and cost-effective alternative to current methods.