Label-Free Electrochemical Sensing Platform for MicroRNA-21 Detection Using Thionine and Gold Nanoparticles Co-Functionalized MoS2 Nanosheet

Herein, we demonstrated a label-free and simple electrochemical sensing platform to detect microRNA-21 (miR-21) with high sensitivity by using MoS2 nanosheet funotionalized with-thionine and gold nanoparticles (MoS2=Thi-AuNPs). Interestingly, thionine (Thi) was used as a reducing agent to successfully synthesize MoS2-Thi-AuNPs nanohybrid and as a signaling molecule to monitor DNA-RNA hybridization,' which provided an ideal platform for label-free miR-21 detection. Upon hybridization with miR-21, the formation of the DNA-RNA duplex on the electrode would greatly hinder the electron transfer, :which caused the electrochemical signal decrease of Thi. After optimization of experimental conditions, the signal change of peak currents of Thi has a linear relationship with the logarithm of miR-21 concentration ranging from 1.0 pM to 10.0 nM and the limit of detection (LOD) was 0.26 pM. Moreover, this biosensor could detect miR-21 in biological samples like human serum with satisfactory results.