Highly sensitive and universal detection strategy based on a colorimetric assay using target-specific heterogeneous sandwich DNA aptamer.

A simple, universal, and sensitive colorimetric biosensor for detecting of various biomarkers was devised using a target-specific DNA aptamer, as the recognition element, and engineered with streptavidin-fusion replication protein A 70 kDa (RPA70A) linked to biotin-horseradish peroxidase, as the colorimetric element. To improve sensitivity and stability compared to other colorimetric sensing platforms, we developed a novel detection strategy by integrating a newly selected heterogeneous sandwich DNA aptamer and protein engineering in this study. The proposed method is based on a change in color from colorless to blue due to the interaction of the aptamer with RPA70A in the presence of the target; this color change could be observed by the naked eye or measured with a UV-vis spectrometer. We confirmed its high sensitivity and specificity for two model targets using their aptamers under optimal experimental conditions. In addition, the feasibility of the assay was investigated in clinical samples containing NPs of influenza A or B virus. These results suggest that our detection system developed herein can be universally applied to the diagnosis of various diseases owing to its stability, sensitivity, and specificity.