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

Herein, we demonstrated a label-free and simple electrochemical sensing platform to detect microRNA-21 (miR-21) with high sensitivity by using MoS2 nanosheet functionalized 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.