Paper-based electrodes modified with molybdenum disulfide (MoS2) in the form of bulk crystals or exfoliated nanosheets were developed and used as a biosensing platform for the impedimetric detection of miRNAs (miRNA-155 and miRNA-21) related to early diagnosis of lung cancer. For this purpose, MoS2 crystals or nanosheets were used for the modification of the working electrode area of paper-based platform for the first time in this study. The proposed assay offers sensitive and selective detection of microRNAs by electrochemical impedance spectroscopy (EIS) technique. The entire assay, both the electrode modification and the miRNA detection being completed in 30 min and a single sample droplet (5 μL) was enough to cover working electrode area which enabled analysis in low sample volumes. The limits of detection (LOD) for miRNA-21 and miRNA-155 were calculated both in buffer and fetal bovine serum media. It is found that the LOD is varying between 1 and 200 ng/mL. In comparison to nanosheets, a larger electroactive surface area was obtained with bulk MoS2 resulting in lower LOD values on miRNA detection. The paper-based electrodes showed high specificity towards their target sequences. Moreover, they effectively discriminated single base mismatched non-target sequences. The advantages of these MoS2 paper based electrodes include high sensitivity, and low-cost provide great potential for improved monitoring of miRNA biomarkers even in artificial serum media.
Keywords: Electrochemical impedance spectroscopy; Molybdenum disulfide; Paper-based electrode; microRNA.
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