Indicator-free electrochemical biosensor for microRNA detection based on carbon nanofibers modified screen printed electrodes

• Carbon nanofiber modified screen printed electrodes (CNF-SPEs) were characterized by SEM.
• Electrochemical characterization of CNF-SPEs was performed by electrochemical impedance spectroscopy.
• Indicator-free detection of miRNA-34a hybridization was performed by differential pulse voltammetry.
• miRNA-34a spesific biosensor was presented good selectivity towards to miRNA-15a or miRNA-660.

Carbon nanofibers (CNFs) are fiber-structured nano-sized carbon materials, which have excellent mechanical, thermal and electrical properties. CNFs possess a wide range of application especially in biorecognition area. In this study, we developed an indicator-free voltammetric biosensor for detection of miRNA-34a target RNA by using carbon nanofiber enriched disposable screen printed electrodes (CNF-SPEs). The sensitive and selective recognition of miRNAs has been an attractive topic due to they have been defined as small RNAs and play major roles in regulating the translation and degradation of messenger RNAs. The characterization of CNF-SPEs in contrast to unmodified ones was firstly performed by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) techniques. The amino linked DNA probe, that was the complementary sequence of miRNA-34a, was immobilized onto the surface of CNF-SPEs. After measuring the guanine oxidation signal measured by differential pulse voltammetry (DPV), the detection of sequence-selective hybridization was then investigated between probe and miRNA-34a RNA target, or other miRNA sequences; miRNA-15a, or miRNA-660, which were chosen as noncomplementary sequences (NC). The detection limit was corresponded to 10.98 μg/mL (54 pmol in 35 μL sample) in the linear concentration range of target miRNA-34a from 25 to 100 μg/mL by using CNF-SPEs. The features of this present study was comprehensively discussed by means of the unique characteristics of single-use CNF-SPEs and importance of miRNA monitoring.

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