Amplified collection of binary G-quadruplex on a binary C-rich functionalized palindromic hairpin probe for label-free detection of a molecular cancer biomarker of microRNA

Detection of well-studied cancer biomarkers of microRNAs (miRNAs) is very valuable for early cancer diagnosis and therapy in clinical medicine. Herein, we designed a binary C-rich functionalized palindromic hairpin probe (BC-FPHP) and employed it as the only species to amplify the common ovarian cancer biomarker of miRNA-21. The BC-FPHP is concurrently proposed with a miRNA-21 recognition loop region, a self-complementary stem region, a binary C-rich fragment at its 5′ end, and a palindromic sequence at its 3′ end. The presence of target miRNA-21 induces the configuration change of BC-FPHP. It makes the amplification event on BC-FPHP occurred without the aid of any other probes, leading to a substantial collection of binary G-quadruplex DNA motifs that can be inserted with thioflavin T (ThT) for remarkable fluorescence emission. In this system, the BC-FPHP is smartly designed with the capabilities to be self-primered, self-templated, and self-amplified, ensuring the isothermal amplification system a simple, low cost, and user-friendly detection platform for sensitive and specific detection of miRNA-21. In addition, the BC-FPHP based amplification system has been successfully used for the detection of miRNA-21 in diluted human serum samples. We envision that this work holds great potential in the early assisting screening of ovarian cancer.