Trigger-activated autonomous DNA machine for amplified liver cancer biomarker microRNA21 imaging

MicroRNA-21 (miRNA-21) is a kind of RNA that exists in biological fluids such as blood, urine and saliva. It has over expression in liver cancer and has different expression in different stages of cancer. However, due to the characteristics of small base number, short length, low abundance and easy degradation of miRNA-21, the detection of miRNA-21 is a challenging subject. Visualization, sensitive, specific and stable detection of tumor suppressor or oncogene microRNAs (miRNAs) remains challenging and is highly significant for clinical diagnostics. To solve this problem, we have developed a target-triggered hybridization assembly DNA machine for intracellular miRNA imaging based on strand displacement amplification (SDA) and branched hybridization chain reaction (B-HCR). In this approach, the target miRNA could hybridize with the template probe to trigger the SDA, resulting in the formation of nicked fragments (NFs) that hybridized with hairpin probe1 (HP1). The opened HP1 could hybridize with hairpin probe2 (HP2), leading to the self-assembly of hyperbranched DNA nanostructures through B-HCR. As expected, the newly developed method exhibits a detection limit down to 11.3 pM miRNA-21 and achieves high selectivity toward miRNA-21 against other interfering miRNAs. Due to its superior sensitivity and selectivity, our method can be further used to detect miRNA-21 in human serum samples. By taking advantage of intelligent design, the proposed method was also used for image miRNA-21 expression levels in different cell lines. This method shows a broad application in clinical diagnosis.