Trigging stepwise-strand displacement amplification lights up numerous G-quadruplex for colorimetric signaling of serum microRNAs.

MicroRNAs (miRNAs) play an important biomarker in various biological processes, especially cancer related, yet economic, simple, sensitive and specific methods for miRNA determination are still challenging. In this study, we have developed stepwise-strand displacement amplification (S-SDA)-based colorimetric sensing platform for let-7a miRNA detection in clinical serum samples. Our results demonstrated that the developed S-SDA-based method shows high sensitivity with a detection limit of 63.2 pM and a naked eye detection limit of 0.1 nM. Moreover, the S-SDA amplifier is able to discriminate target miRNAs from their mutants with high accuracy and specificity. With its high sensitivity and selectivity, this method successfully identified healthy individuals from patients with colon cancer by detecting let-7a miRNAs in serum. We believe the colorimetric analysis method will provide a new paradigm for the detection of miRNA with different abundance and show great potential for clinical application in biomedical analysis and early clinical diagnosis.