Bipedal DNAzyme walker triggered dual-amplification electrochemical platform for ultrasensitive ratiometric biosensing of microRNA-21

Circulating microRNAs (miRNAs) can be regarded as reliable noninvasive biomarkers in body fluids for the early diagnosis, prognosis, and monitoring of cancers. By combining target triggered bipedal DNAzyme walker cleavage cycling amplification and planar intercalated methylene blue (MB) molecules amplification, a versatile ratiometric electrochemical biosensing system is constructed for miRNAs detection. Using the microRNA-21 (miRNA-21) as a triggered model target from breast cancer cells (MCF-7) and cervical cancer cells (HeLa), the sensitivity and feasibility of the ratiometric biosensing strategy were verified on the basis of decreased streptavidin-conjugated cupric sulfide@platinum (CuS@Pt-SA) nanozyme signal with cleaved Zn2+-dependent DNAzyme walkers as well as enhanced duplex section of MB signal, which were assisted by the modification of high electronic conductivity and specific surface area of metallic WSe2 nanoflowers on the electrode. Hence, the introduced sensing strategy of higher cleavage activity of the bipedal DNAzyme walker cyclic amplification resulted into the remarkable sensitive measurement which had a detection limit of 0.16 fM from 1 fM to 1 nM for miRNA-21. Benefiting from the precise design of the capture Hairpin DNA, this proposed method showed excellent specificity to distinguish miRNA-21 from other miRNAs sequences, in addition to possessing good stability and reproducibility. Thus, this versatility platform can be utilized to sense various miRNAs biomarkers by simple of the redesigning the capture Hairpin DNA, hence presents a great promise in clinical application towards early cancer diagnosis, biological analysis and prognosis.