DNA-Based Electrochemical Biosensor for Microrna-155 Detection By Exonuclease III -Aided Cascade Target Recycling

Abstract

MicroRNAs (miRNAs) are important biomarkers for early diagnosis and prognosis of genetic diseases including human cancers and neurological diseases, etc. They are a class of small (about 22 nucleotides) single-stranded non-protein-encoding RNAs, whose abnormal expressions are closely related to the pathogenesis of many malignant tumors. However, they have intrinsic characteristics such as low abundance, short length and sequence homology, so accurate and rapid analysis of miRNAs is of great significance for biological research, diagnosis and treatment of diseases. In this study, based on exonuclease III (Exo III) -aided cascade target recycling, a simple and sensitive electrochemical biosensor is developed for miRNA-155 detection, which is of an important biomarker for the diagnosis of breast cancer. At the same time, Ti3C2 MXene was synthesized and used as a support due to its special layered structure and metallic property. Noble metal nanoparticles were used to enlarge the electro-active surface area and facilitate the electron mobility of electrochemical biosensors. Moreover, MXene nanosheets embedded with noble metal nanoparticles (such as Au NPs, Ag NPs, Pt NPs) could totally ensure MXene nanosheets with improved conductivity and enhanced electrochemical properties. Therefor AuNPs/Ti3C2 MXene three-dimensional composite was selected as substrate for immobilizing capture DNA (cDNA) by Au-S chemical bonds. The whole sensing system is named as cDNA/AuNPs/ Ti3C2 Mxene /Au E. The cDNA was modified with methylene blue (MB) at the end of 3', resulting in a large initial electrochemical signal. In the presence of miRNA-155, Exo III cleaved the 3' end of the cDNA in the double strands, caused the electrochemical signal molecule MB to be released from the electrode surface, thereby reduced the electrochemical signal. The concentrations of miRNA-155 could be monitored simply and effectively by measuring the peak current difference of MB redox (ΔI=Ic﹣Ih, Ic represents the DPV peak current value obtained in the absence of miRNA-155, Ih represents the peak current value recorded in the presence of miRNA-155, and ΔI represents the change in peak current value). Under the optimal experimental conditions, the electrochemical sensor achieved a detection limit of 0.35 fM (S/N =3) with a linear range from 1.00 fM to 100 pM. This method also shows desirable stability, reproducibility and specificity. In conclusion, with its excellent analytical performance, the biosensor may have the potential to be used in the clinical diagnosis of breast cancer.Keywords: Exonuclease III; miRNA-155; Au NPs; Ti3C2 Mxene; Electrochemical biosensor; Figure 1