Target-induced multiple palindrome-mediated strand displacement amplification of Scarecrow-shaped DNA nanoprobe for ultrasensitive detection of MicroRNA

A growing number of studies suggest that miRNAs play a vital role in the diagnosis and treatment of several diseases, especially for cancers. However, miRNA detection still remains great challenges because of its small size, low abundance and easy degradation. In this contribution, we demonstrate an intelligent DNA machine for the detection of miRNA-21 via designing a multiple palindrome-mediated strand displacement amplification (called MP SDA) strategy combined with fluorescence measurement. Essentially, the nano-machine is a scarecrow-shaped DNA nanoprobe (S-nanoprobe) assembled from only three single-stranded DNAs (ssDNAs) each with a palindromic fragment at the 3’-end. In the presence of target, S-nanoprobe can be dissembled into two parts, leading to the release of palindromic ends that can execute MP SDA under DNA polymerase. Benefiting from the high efficiency of MP SDA, S-nanoprobe can be used to detect down to 1 fM of target and exhibit a high specificity. Target miRNA can be 100% discriminated from homologous miRNAs and can also be sensitively detected in complex biological samples. More excitingly, a high recovery rate, desirable blind test results and precise target assay in real samples demonstrate the huge application potential of S-nanoprobe in the detection of tumor-associated biomarkers in early diagnosis. • Target-Induced Multiple Palindrome-Mediated SDA ( MP SDA) for miR-21 detection. • The miR-21 could be detected down to 1 fM with a wide dynamic range. • This strategy displayed an excellent selectivity. • The nanoprobe possessed enhanced resistance to nuclease degradation. • Suitable for the detection of target in a complicate biological milieu.