Distance-Based Visual miRNA Biosensor with Strand Displacement Amplification-Mediated DNA Hydrogel Assembly

We have developed a novel paper biosensor for miRNA assays by monitoring the seepage flow distance along the strip. Target miRNA-initiated strand displacement polymerization produces abundant DNA strands, which assist the assembly of the DNA hydrogel. The phase transition is successfully demonstrated by elastography and electrochemical techniques. The variation of flow distance is highly related to the viscosity of the DNA hydrogel. By visual observation of the distance, highly sensitive quantification of miRNA can be achieved. The limit of detection is estimated to be 1 fM, which is quite low. The utility in clinical samples is also verified by consistent results of the standard quantitative reverse transcription PCR (qRT-PCR) technique. This approach is not only highly sensitive but also exhibits the merits of convenient operation and low cost, meeting the requirements of point-of-care testing. It shows significant potential for the applications of biological studies and clinical disease diagnosis.